[0001]The present invention relates to a lap fillet welding method and lap fillet weld joint of a high strength steel sheet, in particular, be used as a structural component of a motor vehicle, obtained by it lap fillet welding method weldable component and from one side only on lap fillet welded joints.
Background technique
[0002]
　In the field of motor vehicles, for environmental protection, together with improved fuel economy by reducing vehicle weight, the improvement of collision safety has been demanded. Therefore, along with thinning using high strength steel plate, by optimizing the body structure, in order to improve weight reduction and crashworthiness of the vehicle body, various efforts have been made so far.
[0003]
　On the other hand, in the parts of welding, such as an automobile, but spot welding is mainly carried out, must be linear welding at the site that require strength and rigidity, such as a foot around and chassis, fillet welding is performed ing. Then, in the welded joint of such sites, it is required to include a sufficient fatigue strength and static tensile strength.
[0004]
　Normally, the fatigue strength of the base material used to weld members, which increases in proportion to the base metal strength, fatigue strength of the welded joint, even necessarily increase the base material strength, it is known that not increase there. This is a factor that has inhibited the weight of the vehicle body by the use of high-strength steel sheet.
[0005]
　Therefore, in the welded joint obtained by carrying out the fillet welding high strength steel plate, fatigue strength have been studied mainly be improved, to improve the tensile strength has not been made many studies .
[0006]
　Patent Document 1, the hardness of the weld metal, component, and the proper size of the fillet weld bead, techniques for improving the tensile strength of the welded joint obtained by fillet welding is disclosed.
[0007]
　Patent Document 2, the T-shaped welded joints, increasing the thickness of the weld metal overlapping the weld bead, techniques for improving the joint strength is disclosed.
[0008]
　Patent Document 3, as a technology for improving the fatigue strength, the lap fillet weld joint, apart from a technique of forming a stiffening bead is disclosed a weld bead.
CITATION
Patent Literature
[0009]
Patent Document 1: JP 2005-103622 Patent Publication
Patent Document 2: JP 2013-139047 Patent Publication
Patent Document 3: Japanese Patent No. 5522317
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　Superimposing a high-strength steel sheet, it indicates to the test piece obtained by carrying out fillet welding, an example after the tensile test in the state in FIG.
[0011]
　1, the tensile strength 1180MPa class, steel 1a having a thickness of 1.6 mm, superimposing 1b, performs fillet weld between the surface of the end portion and the steel plate 1b of the steel sheet 1a, the obtained test piece an imaging in the thickness direction cross section of the state after performing a tensile test. Incidentally, it may a steel plate 1a side upper, the steel plate 1b side of the lower side.
[0012]
　Test piece shown in FIG. 1, the steel sheet not destroyed (base material) 1a, 1b, when a load of 28KN, weld bead (fillet welds) are cracks from 2 root portion pulling direction and substantially perpendicular making progress in the direction, being broken at the weld metal.
[0013]
　Figure 2 shows the Vickers hardness distribution. Figure 2 is the steel sheet weld bead 2 is formed on the surface shown in FIG. 1 (base material) 1b 0.2 mm depth from the surface in the thickness direction (shown by the dotted line position), steel (base material) parallel to the surface direction of 1b is obtained by measuring the Vickers hardness. In FIG. 2, A region is Vickers hardness of the base metal and weld heat affected zone (HAZ portion), B region is Vickers hardness of the weld metal. Thus, Vickers hardness of the weld metal has become equal to the Vickers hardness of the base material.
[0014]
　Thus, the test piece fabricated using tensile strength of at least upper steel over steel sheet (base material) 780 MPa, not have high ductility of the upper steel sheet, also Vickers hardness of Vickers hardness and the base metal of the weld metal since the Saga equal, not fractured in the base metal, stress and progress crack from the root portion to focus breaks in the weld metal.
[0015]
　On the other hand, in the welded joint obtained by fillet welding, when subjected to excessive tensile loads, without breaking the weld metal, as long as it stably destroyed matrix, reproducibly welded joint since the design strength is obtained, the safety of an automobile or the like, can contribute to improvement in reliability.
[0016]
　The technique disclosed in Patent Document 1, in order to improve the tensile strength, but is intended to adjust the hardness of the weld metal due to its chemical composition, if the Vickers hardness HV of the weld metal to more than 500, the weld metal it may be delayed crack occurs. The adjustment of the chemical composition, it may not be possible to select a flexible welding wire.
[0017]
　Further, the present inventors have with reference to Patent Document 2, in order to improve the tensile strength of lap fillet weld joint was investigated to increase the thickness of the weld metal. However, the weld metal is to be welded so as to be thick, it is necessary to increase the heat input, a result, there is the welding deformation is increased.
[0018]
　Further, the stiffening bead disclosed in Patent Document 3 remain in partial reinforcement, also when increasing the number of stiffening bead heat input increases, sometimes welding deformation increases.
[0019]
　On the other hand, in the lap fillet weld joint, by fillet welding to both sides of the member to be welded, it is possible to improve the tensile strength. However, the structure of the member to be welded can not be welded only from one side of the member to be welded, it may not be possible to implement the fillet weld on both sides of the workpiece to be welded.
[0020]
　In the present invention, in view of such circumstances, provided without increasing the welding deformation, when a load of tension, not broken in the weld metal, the welding method of obtaining a lap fillet welded joint having excellent tensile strength it is an object of the invention to.
Means for Solving the Problems
[0021]
　The present inventors have intensively studied means for solving the above problems. The present inventors have an upper steel sheet becomes tensile strength 780MPa or more first steel sheet in fillet welded joint (hereinafter also referred to as "high-strength steel sheet"), overlapping a second steel plate as the lower side of the steel plate together, reinforced between the end portion and the second surface of the steel sheet of the first steel plate when fillet welding, the first steel sheet, on the opposite side of the surface and the overlapping surface with the second steel plate the provided section was conceived dispersing the stress concentrated on the root portion.
[0022]
　Then, the weld metal, the ends of the reinforcing portion, the end portion of the first steel sheet, were fillet welded to cover between the surface of the second steel sheet, without increasing the welding deformation of the welded joint, the tensile strength was found that to improve.
[0023]
　The present invention has been made based on such findings, the gist is as follows.
[0024]
　(1) a first steel plate and a method of fillet welding overlay welding planned portion of the second steel sheet, and the tensile strength of the first steel sheet 780MPa or more, the method, the first a surface of the steel sheet, the step of forming the first steel plate and a reinforcing portion bonded to the surface opposite to the surface in contact with the second steel sheet at the time of superimposing the second steel plate, the reinforcing portion fillet welding method, which comprises an end portion, a step of fillet welding as between cover has a weld metal with the first steel plate end portion and the second surface of the steel sheet of the.
[0025]
　(2) the fillet weld throat thickness of the fillet welds formed by D T (mm), the average hardness of the fillet weld H F (HV), the thickness of the first steel plate D 1 (mm), the smaller hardness of the hardness of the base material hardness and a first steel HAZ softening of the fillet weld of the first steel sheet H S when the (HV), (D T × H F ) / (D 1 × H S fillet welding method (1) which) is equal to or is less than 1.50.
[0026]
　(3) fillet welding method (1) or (2) the reinforcing portion, which is a reinforcing material.
[0027]
　(4) an end portion of the reinforcement, the a surface of the first steel plate is fillet welded to the surface opposite to the surface in contact when superposed first steel plate and a second steel plate fillet welding method (3), characterized in that.
[0028]
　(5) the reinforcing member is a surface of said first steel plate, the opposite surface to the first steel plate and the surface in contact with the time of superimposing the second steel plate, the reinforcing material and the first fillet welding method (3), wherein the joining by overlapping surface with the steel plate.
[0029]
　(6) the reinforcement section, a corner of said, characterized in that said first opposite weld bead formed on the surface of the second surface overlaying the steel of the steel plate (1) or (2) meat welding method.
[0030]
　(7) the reinforcing portion, fillet welding method according to (1) or (2), characterized in that it is formed by processing the first steel sheet.
[0031]
　(8) a first steel plate and welded joint second steel plates are fillet welded, and at the first steel tensile strength 780MPa or more, a surface of said first steel plate, said first comprising a first steel plate and a second reinforcing portion joined to a surface opposite to the surface in contact with the steel plate when overlapping the second steel plate, the end portion of the first steel plate, the second steel plate surface, and fillet weld joint and having a fillet weld between the end portion of the reinforcing member.
[0032]
　(9) said throat thickness of the fillet weld D T (mm), the average hardness of the fillet weld H F (HV), wherein the thickness of the first steel plate D 1 (mm), the first fillet welds HAZ softening of the hardness of the steel plate, and a smaller hardness of the hardness of the base material of the first steel sheet H S when the (HV), (D T × H F ) / ( D 1 × H S fillet welded joint of the (8)) is equal to or is less than 1.50.
[0033]
　(10) fillet welded joint of the (8) or (9) wherein the reinforcing portion, which is a reinforcing material.
[0034]
　(11) an end portion of the reinforcement, the first a surface of the steel sheet, the surface opposite to the surface in contact with the second steel sheet at the time of overlapping the said first steel plate and a second steel plate fillet welded joint of the (10), characterized in that it is fillet welded to.
[0035]
　(12) the reinforcing member, the first a surface of the steel sheet, on the surface opposite to the surface in contact with the second steel sheet at the time of overlapping the said first steel plate and a second steel sheet, the fillet welded joint of the (10), characterized in that a reinforcing material is joined with the reinforcing member and the overlapping surface between the first steel sheet.
[0036]
　(13) the reinforcing section, a corner of said, characterized in that the a first side opposite the weld bead formed on the surface of the second surface overlaying the steel of the steel plate (8) or (9) meat welded joints.
[0037]
　(14) the reinforcing portion is fillet welded joint of the (8) or (9), characterized in that it is formed by processing the first steel sheet.
Effect of the invention
[0038]
　According to the present invention, since the fillet weld is provided with reinforcing portions on the surface of the high strength steel sheet, without increasing the welding deformation of the welded joint, stress concentration to the root portion can be avoided, improving the tensile strength it can be.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039]
An imaging showing a state after the tensile test [1] fillet weld test piece obtained by carrying out.
Is a diagram illustrating a FIG. 2 Vickers hardness distribution.
[3] The reinforcing member on the upper surface of the upper steel sheet provided is a diagram illustrating an example of fillet welding. (A) shows a state in which a reinforcement on the upper surface of the upper steel sheet (b) shows the upper steel plate, the lower steel plate, and, the state of fillet welded to the reinforcement.
[4] providing a reinforcement on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint reinforcement and fillet welding.
[5] provided the reinforcements curved upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint reinforcement and fillet welding.
[6] providing a reinforcement on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint discontinuously fillet weld reinforcement.
[7] The reinforcing member on the upper surface of the upper steel sheet provided is a diagram illustrating an example of fillet welding. (A) shows a state where the bonding is provided a reinforcing member on the upper surface of the upper steel sheet (b) shows the upper steel plate, the lower steel plate, and, the state of fillet welded to the reinforcement.
[8] provided a reinforcing member on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint reinforcement and fillet welding.
[9] providing a reinforcing member that is curved to the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint reinforcement and fillet welding.
[10] provided a reinforcing member on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view showing an example of a welded joint discontinuously fillet weld reinforcement.
[11] The reinforcing bead is formed on the upper surface of the upper steel plate is a diagram showing an example of fillet welding. (A) shows a state of forming a reinforcing bead on the upper surface of the upper steel sheet (b) shows the upper steel plate, the lower steel plate, and, the state of fillet welded to the reinforcing bead.
[12] to form a reinforcing bead on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view of an example of a welded joint reinforcement beads were fillet welded.
[13] to form a reinforcing bead which is curved to the upper surface of the upper steel sheet, the upper steel sheet, lower sheet and, a plan view of an example of a welded joint reinforcement beads were fillet welded.
[Figure 14] to form a reinforcing bead on the upper surface of the upper steel sheet, the upper steel plate, the lower steel plate, and is a plan view of an example of a welded joint discontinuously fillet welded reinforcing bead.
[Figure 15] is a view for explaining the throat thickness of the fillet weld, (a) shows the case the weld bead is convex, (b) if the weld bead is concave, (c) the upper steel plate and lower it is a diagram of a case where there is a gap between the steel plates.
[16] The upper steel sheet and a lower steel plate is a diagram showing a comparative example in which multiplexing up welding.
DESCRIPTION OF THE INVENTION
[0040]
　Fillet welding method of the present invention (hereinafter referred to as "welding method of the present invention") is,
　first a high-strength steel sheet reinforcement portion is provided on the surface opposite to the surface to overlay (i) and the second steel plate superimposing of the steel plate and a second steel plate,
fillet welding so as to cover the (ii) the end portion of the reinforcing member, an end portion of the first steel plate, the weld metal between a surface of the second steel plate it is a method.
[0041]
　Thus, without increasing the welding deformation of the welded joint, it is possible to avoid stress concentration to the root portion, it is possible to improve the tensile strength. Hereinafter, the first steel plate upper steel refers to a second steel plate with the lower steel sheet, a first steel plate side upper, second steel plate side of the lower side.
[0042]
　Next, the described background investigation that led to the welding method of the present invention, a description will be given of the basic structure of the welding method of the present invention.
[0043]
　In lap fillet weld joint, without increasing the welding deformation, to improve the tensile strength has been desired. Technology for improving the joint strength by increasing the thickness of the weld metal is conventionally known, the welding as the weld metal becomes thick, it is necessary to increase the heat input, the welding deformation there had to be increased.
[0044]
　The present inventors have found that increasing the thickness of the weld metal, dispersing the stress concentrated on the root portion, thought to improve the tensile strength, together with dispersing the stress concentrated on the root portion, suppress welding deformation It was investigated means for. As a result, it was conceived to be fillet welded by providing a reinforcing section on the upper surface of the upper steel plate.
[0045]
　First, an example of a method of fillet welding is provided with reinforcing portions will be described with reference to the drawings.
[0046]
　3, the reinforcing portion the ends of the reinforcing member on the upper surface of which is fillet welded the upper steel plate is provided, the end portion of the reinforcing portion, so that the end portion and the surface of the lower steel plate of the upper steel plate covered by the weld metal It shows an example of fillet welding. 3 (a) shows a state in which a reinforcement portion on the upper surface of the upper steel sheet, FIG. 3 (b) shows the upper steel plate, the lower steel plate, and, the state of fillet welded to the reinforcing portion.
[0047]
　Reinforcing portion, as shown in FIG. 3 (a), the reinforcing member 30 on the upper side of the upper steel plate 10a arranged, as shown in FIG. 3 (b), one end of the reinforcing member 30 and the surface of the upper steel sheet 10a performed fillet welding between, to form a fillet weld 40 is provided by fixing the reinforcing member 30 to the upper steel plate 10a. Then, the other end portion of the reinforcing member 30, performs the end portion of the upper steel plate 10a, a fillet weld between the surface of the lower steel plate 10b, to form a fillet weld 20, fillet weld joint obtained. Note that the fillet weld 20 shows where there is the weld bead.
[0048]
　Next, performed fillet welding is provided with reinforcing portions, to prepare a test piece, it will be described results of the tensile test.
[0049]
　First, the same tensile strength 1180MPa class as the test piece shown in FIG. 1 were prepared two sheets of steel sheet having a thickness of 1.6 mm. Then, as shown in FIG. 3, the reinforcing member on the upper side of the upper steel plate is provided, between the end portion and the upper surface of the steel sheet reinforcement, using a high-strength steel sheet for wire and secured perform arc welding. Next, the fixed upper steel sheet superposed reinforcement and the lower steel plate, between the end portion of the reinforcing member, and the end portion of the upper steel sheet, the surface of the lower steel sheet, high strength steel sheet in the same manner as described above with use wire was bonded performs arc welding.
[0050]
　Respect prepared specimens were subjected to tensile load in the direction indicated by the arrow in FIG. 3 (b), was subjected to a tensile test at a tensile rate of 10 mm / min. As a result, the test piece does not break in the weld metal, when a load of 47KN, was broken in the weld heat affected zone of the other steel plate (base metal) (HAZ portion).
[0051]
　As described above, in the case of not using a reinforcing member (FIG. 1), the test piece, when a load of 28KN, is fractured at the weld metal, the use of the reinforcing member, stress concentration to the root portion avoidance can, tensile strength can be improved.
[0052]
　The present invention, the above (1) through the study process as described above and (2) in are those that led to the invention described, such fillet welded joint welding method and the present invention of the present invention (hereinafter, About) called "joint of the present invention", further, the necessary requirements and preferred features will be described in sequence.
[0053]
　First, with respect to the reinforcing portion and fillet dissolved reinforcements on the upper steel plate, the shape of the reinforcing member, the dimensions, arrangement, relationship between the fillet weld, the component composition will be described.
[0054]
　(Shape and dimensions of the reinforcing member)
　for the preferred shape of the reinforcing member provided on the upper surface of the upper steel sheet will be described with reference to FIG.
[0055]
　The shape of the reinforcing member is not limited in particular, in FIG. 3, the cross-sectional shape, but has a rectangular shape, can be adopted trapezoid like any shape. The shape of the reinforcing member in a plan view from above is not limited in particular, it may be employed a rectangular shape, a semicircular shape or the like of any shape.
[0056]
　The width W of the reinforcing member 30 in the pulling direction in contact with the overlapping surfaces of the upper steel plate 10a, in order to stress the root portion of the weld bead formed by fillet welding efficiently dispersed, or the thickness tb of the upper steel plate 10a It is preferred. Width W of the reinforcing member 30, since the weight of the fillet weld joint, the tensile preferably less than or equal to the maximum overlap width X of the upper steel plate 10a and the lower steel plate 10b in the direction. The width W of the reinforcing member 30 need not be constant in the longitudinal direction of the fillet weld.
[0057]
　Thickness ta of the reinforcing member 30 of the end on the side to be welded with the lower steel plate 10b, since the tensile strength increase, half the thickness tb of the upper steel plate 10a (tb × 0.5) or more. Thickness ta of the reinforcing member 30, for reducing the weight of the fillet weld joint, double the thickness tb of the upper steel plate 10a (tb × 2.0) or less. The thickness ta of the reinforcing member 30 need not be constant in the longitudinal direction of the weld bead.
[0058]
(Reinforcement arrangement)
　positions the ends of the reinforcing member 30 on the side welded to the lower steel plate 10b is preferably is aligned with the position of the end portion of the upper steel plate 10a. However, based on the position of the end portion of the upper steel plate 10a, if located within the range of ± 2 mm in the tensile direction the ends of the reinforcing member 30, it is possible to obtain a weld joint of sufficient tensile strength.
[0059]
(The relationship between the reinforcing material and the fillet weld)
　shown in FIG. 3 (b), the height tc fillet weld 20 from the surface of the lower steel plate 10b, for the tensile strength increase, the upper steel plate 10a and the thickness tb greater. The height of the fillet weld 20 tc, it is preferable that the sum of the thickness ta of the thickness tb of the upper steel plate 10a stiffener (ta + tb) equivalent. Height tc fillet weld 20, for the welding deformation suppression, double the sum of the stiffener ta and the thickness tb of the upper steel plate 10a [(ta + tb) × 2.0] or less. The height tc fillet welds 20 need not be constant in the longitudinal direction of the fillet weld 20.
[0060]
　Height td fillet weld 40 from the surface of the upper steel plate 10a is not limited in particular, it may be a height at which the reinforcing member 30 and the upper steel plate 10a is bonded, thickness of the reinforcing member 30 it is preferable that the equivalent to the ta.
[0061]
　4, the reinforcing member on the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement and fillet welding. Figure 4 is a view showing a case where the welded joint from above in a plan view. The length La of the reinforcing member 30 along the end on the side to be welded of the upper steel sheet 10a, since the tensile strength increase, half of the total length Lb of the fillet weld 20 in the welding direction (Lb × 0.5) or more It is preferred. The length La of the reinforcing member 30, since the weight of the fillet weld joint, double the total length Lb of the fillet weld 20 (Lb × 2.0) or less.
[0062]
　In Figure 4, the reinforcing member 30, the upper steel plate 10a, and, the length of the fillet weld 20 for joining the lower steel plate 10b Lc (length Lc of the fillet weld reinforcement), the length of the reinforcing member 30 is La and is, although shown as matching, the length of both may not coincide. The length Lc of the fillet weld 20, for the tensile strength improvement, it is preferable that the half of the total length Lb of the fillet weld 20 (Lb × 0.5) or more. The length Lc of the fillet weld 20, it is more preferable to match the total length Lb of the fillet weld 20.
[0063]
　Further, (total length Ld of the fillet weld reinforcement) the total length Ld of the fillet weld 40 in the welding direction is not limited in particular, reinforcing member 30 and the upper steel plate 10a is only to be joined, it is preferable that equal to the length La of the reinforcing member 30.
[0064]
　Figure 5, a reinforcing member that is curved to the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement and fillet welding. Figure 5 is a view showing a case where the welded joint from above in a plan view. As shown in FIG. 5 curved, when viewed from above the end on the side to be welded from the upper side of the upper steel plate 10a, if the end portion is in the curve, along the edge of the side where the welding of the upper steel plate 10a it is preferable to provide the reinforcing member 30 to be equal. The relationship between the total length Lb of the lengths La and fillet weld 20 of the reinforcing member 30, the relationship between the total length Lb of the fillet weld length Lc and fillet weld, full length Ld of fillet welds 40 It may be the same as that described with reference to FIG.
[0065]
　Figure 6, a reinforcing member on the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and, a plan view of an example of welded joint discontinuously fillet weld reinforcement. As shown in FIG. 6, fillet weld 20 may be discontinuous. Then, the reinforcing member 30, the length of the fillet weld 20 between the upper steel plate 10a, a lower steel plate 10b (Lc1 + Lc2), because the tensile strength improved, the overall length of the fillet weld 20 (Lb1 + Lb2) it is preferable that the half [(Lb1 + Lb2) × 0.5] or higher. Further, fillet weld length of (Lc1 + Lc2), it is more preferable to match the total length of the fillet weld 20 (Lb1 + Lb2). The number of fillet weld 20 is discontinuous is not particularly limited.
[0066]
(Reinforcement component composition, etc.)
　composition of the reinforcing material is not particularly limited, it can be employed steel plate of various component compositions. It is also possible to employ a metal member other than steel. The reinforcing material may be obtained by forming a surface treatment coating such as plating on the surface.
[0067]
　(Another Embodiment 1 of the reinforcing portion)
　will be described next reinforcement portion bonding the reinforcing member in superposed on the upper steel plate surface.
[0068]
(Shape and dimensions of the reinforcing member)
　for the preferred shape of the reinforcing member provided on the upper surface of the upper steel sheet will be described with reference to FIG.
[0069]
　The shape of the reinforcing member is not limited in particular, in FIG. 7, the cross-sectional shape, but has a rectangular shape, can be adopted trapezoid like any shape. The shape of the reinforcing member in a plan view from above is not limited in particular, it may be employed a rectangular shape, a semicircular shape or the like of any shape.
[0070]
　Width W of the reinforcing member 130 in the pulling direction in contact with the overlapping surfaces of the upper steel plate 10a, in order to stress the root portion of the weld bead formed by fillet welding efficiently dispersed, or the thickness tb of the upper steel plate 10a It is preferred. Width W of the reinforcing member 130 is, for reducing the weight of the fillet weld joint, the tensile preferably less than or equal to the maximum overlap width X of the upper steel plate 10a and the lower steel plate 10b in the direction. The width W of the reinforcing member 130 need not be constant in the longitudinal direction of the fillet weld.
[0071]
　In FIG. 7 (a), the thickness ta (right side) of the reinforcing member 130 is, for tensile strength increase, half the thickness tb of the upper steel plate 10a (tb × 0.5) or more. Thickness ta of the reinforcing member 130 is, for reducing the weight of the fillet weld joint, double the thickness tb of the upper steel plate 10a (tb × 2.0) or less. The thickness ta of the reinforcing member 130 need not be constant in the longitudinal direction of the weld bead.
[0072]
(Arrangement of reinforcement)
　in FIG. 7 (b), the position of the (right) end of the reinforcing member 130 is preferably aligned with the position of the (right) end of the upper steel plate 10a. However, based on the position of the end portion of the upper steel plate 10a, if located within the range of ± 2 mm in the tensile direction the ends of the reinforcing member 130, it is possible to obtain a weld joint of sufficient tensile strength.
[0073]
(The relationship between the reinforcing material and the fillet welds and joint)
　shown in FIG. 7 (b), the height tc fillet weld 120 from the surface of the lower steel plate 10b, since the tensile strength increase, the upper the thickness tb of greater than steel 10a. The height of the fillet weld 120 tc, it is preferable that the sum of the thickness ta of the thickness tb of the upper steel plate 10a stiffener (ta + tb) equivalent. Height tc fillet weld 120 for the welding deformation suppression, double the sum of the stiffener ta and the thickness tb of the upper steel plate 10a [(ta + tb) × 2.0] or less. The height tc fillet weld 120 does not have to be constant in the longitudinal direction of the fillet weld 120.
[0074]
　Stiffener 130 and junction 140 which is formed on the overlapping surface of the upper steel sheet 10a may be formed so as both are bonded, the position and the width of the width W direction of the reinforcing member 130 and the like, particularly limited not intended to be. Width Wa of the weld 140 in the width W direction of the reinforcing member 130 is 0.1 unfused width Wb of the reinforcing member 130 (the width of the portion other than the portions that have been melted by fillet welding of the width W of the reinforcing member) it is preferable that more than doubled the width. An end position of the fillet weld portion of the welded portion 140 in the width W direction of the reinforcing member 130, from the end of the reinforcing member 130 of the fillet weld portion, the reinforcing member 130 of unmelted width Wb 0. it is preferable to be positioned overlapping surface away 1 times or more.
[0075]
　8, the reinforcing member on the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement and fillet welding. Figure 8 is a diagram when the welding joint from above in plan view, and further, projecting the joints on the upper surface of the reinforcing member. The length La is a reinforcement 130 along the end on the side to be welded of the upper steel plate 10a, because of the tensile strength increase, half of the total length Lb of the fillet weld 120 in the welding direction (Lb × 0.5) or more It is preferred. The length La of the reinforcing member 130 is, for reducing the weight of the fillet weld joint, double the total length Lb of the fillet weld 120 (Lb × 2.0) or less.
[0076]
　In Figure 8, the reinforcing member 130, the upper steel plate 10a, and, the length of the fillet weld 120 joining the lower steel plate 10b Lc (length Lc of the fillet weld reinforcement), the length of the reinforcing member 130 is La and is, although shown as matching, the length of both may not coincide. The length Lc of the fillet weld 120, because of the tensile strength increase, it is preferable that the half of the total length Lb of the fillet weld 120 (Lb × 0.5) or more. The length Lc of the fillet weld 120, it is more preferable to match the total length Lb of the fillet weld 120.
[0077]
　Also, the total length Ld of the joint 140 in the direction of welding is not limited in particular, it is sufficient that the upper steel plate 10a and the reinforcing member 130 are joined, it is preferable that equal to the length La of the stiffener 130 .
[0078]
　9, a reinforcing member that is curved to the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement and fillet welding. Figure 9 is a diagram when the welding joint from above in plan view, and further, projecting the joints on the upper surface of the reinforcing member. As shown in FIG. 9, a plan view of the end on the side to be welded from the upper side of the upper steel plate 10a, if the end portion is in the curve, along the edge of the side where the welding of the upper steel plate 10a curved it is preferable to provide a reinforcing member 130 to be equal. The relationship between the total length Lb of the lengths La and fillet weld 120 of the stiffener 130, the relationship between the total length Lb of the fillet weld length Lc and fillet weld, full length Ld of the joint 140, it can be the same as that described with reference to FIG.
[0079]
　10, the reinforcing member on the upper surface of the upper steel sheet provided, showing the upper steel plate, the lower steel plate, and, a plan view of an example of welded joint discontinuously fillet weld reinforcement. As shown in FIG. 10, fillet weld 120 may be discontinuous. Then, a reinforcing member 130, the length of the fillet weld 120 between the upper steel plate 10a, a lower steel plate 10b (Lc1 + Lc2), because the tensile strength improved, the overall length of the fillet weld 120 (Lb1 + Lb2) it is preferable that the half [(Lb1 + Lb2) × 0.5] or higher. Further, fillet weld length of (Lc1 + Lc2), it is more preferable to match the total length of the fillet weld 120 (Lb1 + Lb2). The number of fillet weld 120 is discontinuous is not particularly limited.
[0080]
　Further, FIG. 10, further, has projecting joints to the upper surface of the reinforcing member, the junction 140 may be discontinuous. The length of the junction 140 (Ld1 + Ld2) is not limited in particular, may be the upper steel plate 10a and the reinforcing member 130 is long as it is joined, above 0.1 times the length La of the reinforcing member 130 and it is preferable to. The width of the joint 140 (Wa1 + Wa2) is not particularly limited as long upper steel plate 10a and the reinforcing member 130 are joined, it is 0.1 times or more of unmelted width Wb of the reinforcing member 130 It is preferred. The number of joints 140 is discontinuous is not particularly limited.
[0081]
(Reinforcement component composition, etc.)
　composition of the reinforcing material is not particularly limited, it can be employed steel plate of various component compositions. It is also possible to employ a metal member other than steel. The reinforcing material may be obtained by forming a surface treatment coating such as plating on the surface.
[0082]
　(Other embodiments of the reinforcement part 2)
　Next, the surface of the upper steel plate, the weld bead has a fillet weld is formed separately (reinforcing bead) will be described with respect to embodiments of the reinforcing section.
[0083]
(Shape and dimensions of the reinforcing beads)
　for the preferred shape of the reinforcing bead is provided on the upper surface of the upper steel sheet will be described with reference to FIG. 11.
[0084]
　The shape of the reinforcing bead is not particularly limited, it is possible as shown in FIG. 11, is conventional cross-sectional shape and mountain shape. The shape of the reinforcing bead in a plan view from above is not limited in particular, linear, can also be employed curved like any shape.
[0085]
　The maximum width of the reinforcing beads 230 in the pulling direction W ', in order to stress the root portion of the fillet weld bead efficiently dispersed, or the thickness tb of the upper steel plate 10a is preferred. The maximum width W of the reinforcing bead 230 ', for reducing the weight of the fillet weld joint, the tensile preferably less than or equal to the maximum overlap width X of the upper steel plate 10a and the lower steel plate 10b in the direction. The maximum width W of the reinforcing bead 230 need not be constant in the longitudinal direction of the fillet weld.
[0086]
　To broaden the reinforcing bead 230, it is possible to employ a parallel beads or weaving bead. In addition, the reinforcing bead is not only the arc heat source, can be employed laser cladding, etc. any heat source utilizing a laser heat source. The filler material may be employed rods, wire, powder and the like.
[0087]
　Maximum height ta of the reinforcing bead 230 'because of the tensile strength increase, half the thickness tb of the upper steel plate 10a (tb × 0.5) or more. Maximum height ta of the reinforcing bead 230 for weight reduction of fillet welded joint, double the thickness tb of the upper steel plate 10a (tb × 2.0) or less. The maximum height ta of the reinforcing bead 230 'need not be constant in the longitudinal direction of the weld bead.
[0088]
(Reinforcing arrangement of beads)
　position of the toe portion 240 of the lower steel plate 10b and fillet weld to the side of the reinforcing bead 230 is preferably is aligned with the position of the end portion of the upper steel plate 10a. However, from the end of the upper steel plate 10a, toe portion of the reinforcing bead 230 if located in a range of 2 mm, it is possible to obtain a weld joint of sufficient tensile strength.
[0089]
(Reinforcing bead and the corner relationship between the weld portion)
　height tc fillet weld 220 from that shown in FIG. 11 (b), the surface of the lower steel plate 10b, since the tensile strength increase, the upper steel plate 10a and the thickness tb greater. Height tc fillet weld 220, 1.2 times the thickness tb of the upper steel plate 10a (tb × 1.2) or more, the maximum height of the thickness tb between the reinforcing bead of the upper steel plate 10a ta ' it is further preferred that the sum of (ta '+ tb) equivalent. Height tc fillet weld 220 for the welding deformation suppression, double the sum of the thickness tb between the reinforcing bead ta of the upper steel plate 10a [(ta '+ tb) × 2.0] or less. The height tc fillet weld 220 does not have to be constant in the longitudinal direction of the fillet weld 220.
[0090]
　Also, toe 250 of the side of the fillet weld 220 in contact with the reinforcing bead 230 of the surface of the reinforcing beads 230, from the position indicating the maximum height ta of the reinforcing beads 230, toe reinforcing beads 230 240 it is preferably formed on the surface of up to.
[0091]
　12, to form a reinforcing bead on the upper surface of the upper steel sheet, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement beads were fillet welded. Figure 12 is a view showing a case where the welded joint from above in a plan view. The length La is a reinforcing bead 230 along the end on the side to be welded of the upper steel plate 10a, because of the tensile strength increase, half of the total length Lb of the fillet weld 220 in the welding direction (Lb × 0.5) or more It is preferred. The length La of the reinforcing bead 230 for weight reduction of fillet welded joint, double the total length Lb of the fillet weld 220 (Lb × 2.0) or less.
[0092]
　In Figure 12, the reinforcing bead 230, the upper steel plate 10a, and, the length of the fillet weld 220 joining the lower steel plate 10b Lc (length Lc of the fillet weld reinforcing beads), the length of the reinforcing bead 230 is La and is, although shown as matching, the length of both may not coincide. The length Lc of the fillet weld 220, because of the tensile strength increase, it is preferable that the half of the total length Lb of the fillet weld 220 (Lb × 0.5) or more. The length Lc of the fillet weld 220, it is more preferable to match the total length Lb of the fillet weld 220.
[0093]
　13, to form a reinforcing bead which is curved to the upper surface of the upper steel sheet, showing the upper steel plate, the lower steel plate, and a plan view of an example of a welded joint reinforcement beads were fillet welded. Figure 13 is a view showing a case where the welded joint from above in a plan view. As shown in FIG. 13 curved, when viewed from above the end on the side to be welded from the upper side of the upper steel plate 10a, if the end portion is in the curve, along the edge of the side where the welding of the upper steel plate 10a it is preferable to form the reinforcing bead 230 equally. The relationship between the total length Lb of the lengths La and fillet weld 220 of the reinforcing beads 230, the relationship between the total length Lb of the lengths Lc and fillet weld fillet weld has been described with reference to FIG. 12 It may be the same as ones.
[0094]
　14, to form a reinforcing bead on the upper surface of the upper steel sheet, showing the upper steel plate, the lower steel plate, and, a plan view of an example of welded joint discontinuously fillet welded reinforcing bead. As shown in FIG. 14, fillet weld 220 may be discontinuous. Then, a reinforcing bead 30, the length of the fillet weld 220 between the upper steel plate 10a, a lower steel plate 10b (Lc1 + Lc2), because the tensile strength improved, the overall length of the fillet weld 220 (Lb1 + Lb2) it is preferable that the half [(Lb1 + Lb2) × 0.5] or higher. Further, fillet weld length of (Lc1 + Lc2), it is more preferable to match the total length of the fillet weld 220 (Lb1 + Lb2). The number of fillet weld 220 is discontinuous is not particularly limited.
[0095]
(Component composition of the reinforcing beads)
　composition of the reinforcing bead is not particularly limited, it may be a weld metal of the various component compositions. However, the working efficiency of the welding, it is preferable to form the reinforcing bead by using the same welding wire and the welding wire used in the formation of fillet weld, equivalent to the component composition of the fillet weld the component composition of the weld metal it is preferable to.
[0096]
　Note that the example using the reinforcing bead as a reinforcing part of the present invention, as appearance similar form, welding a plurality of times, a so-called multi-prime. This Applying the present invention, after the fillet welding overlapping the lower steel plate and the upper steel plate is in the form of forming a reinforcing bead thereon.
[0097]
　However, in such a multi-platter, lap fillet welding of the upper steel plate and the lower steel sheet, it does not take place the end of the reinforcing portion so as to cover the weld metal, different from the embodiment of the present invention. Further, in this embodiment, when formed on the fillet weld overlapping reinforcing beads, because martensite of lap fillet weld is partially tempered been softened region occurs, lap fillet welds weld metal tends to break the. That is, the effect of the present invention can not be obtained.
[0098]
　As another embodiment of the reinforcing portion, the other embodiments described above, the reinforcing portion may be provided by processing the steel sheet. For example, press-molded so that the ends of the steel sheet surface becomes convex, the end became convex can also be used as a reinforcing portion.
[0099]
　It will now be described steel sheet used in the welding process and joint of the present invention of the present invention.
　In the welding method and joint of the present invention of the present invention, the tensile strength in the upper steel plate used 780MPa or more steel (high-strength steel sheet). In welded joint fillet welding using high strength steel plate in the upper steel plate when subjected to excessive tensile load, without breaking with the base material, it may be broken at the weld metal, the improvement of tensile strength of a welded joint This is because you need. Lower steel plate, or the like chemical composition is not limited in particular, it is possible to use a high strength steel sheet similar to the upper steel plate.
[0100]
　The thickness of the upper steel plate and lower steel plates, not limited in particular, can be 0.5 ~ 3.0 mm. Further, the thickness of the whole of the upper steel plate and lower steel plates, not limited in particular, can be 1.0 ~ 6.0 mm. The upper sheet and lower steel sheet may be a steel sheet to form a surface treatment coating such as plating on both surfaces or one surface. If blowhole defects plating due occurs, it may be welded with a gap between the plates.
[0101]
　Steel plate, has a plate-shaped portion on at least a portion, as long as it has a portion where the plate-like portion is stacked superposed each other or even entirely without a plate. Further, the steel sheet is not limited to those composed of separate steel plate, or a superposition of those molding a single steel plate into a predetermined shape of the tubular, and the like.
[0102]
　Next, the flow of the welding method of the present invention.
[0103]
　First, in the welding method of the present invention, to prepare the upper sheet and the lower steel plate as described above. For example, to prepare two pieces of the non-plated steel plate of a tensile strength 1180MPa having a thickness of 1.6 mm. Next, prepare the reinforcement, the upper steel plate reinforcement shapes and sizes in accordance with the fillet weld is formed by fillet welding between the lower steel plate. For example, the shape when viewed in plan from the cross-sectional shape and an upper plate thickness direction, a rectangular shape, the width W is 20 mm, thickness ta is prepared 1.6mm reinforcements.
[0104]
　If the reinforcing material to form a reinforcing portion, which is fillet welded, superposed reinforcement to the upper steel plate and fillet weld between the one end portion of the surface of the upper steel reinforcement. For example, fillet weld height td fillet welds so that 1.6mm is the same height as the reinforcing material. Then, the other end portion of the reinforcing member, and the end portion of the upper steel plate is fillet welded to the between the surface of the lower steel sheet becomes a relationship between the reinforcing material and the fillet weld above. For example, in 3.2mm height tc fillet welds plus the thickness ta of the reinforcing material and the thickness tb of the upper steel plate, the length Lc of the fillet weld, the length La and the corner of the reinforcement to match the total length Lb of the weld portion, the fillet weld.
[0105]
　Incidentally, the other end portion of the reinforcing member, and the end portion of the upper steel sheet, and fillet welding as between the surface of the lower steel sheet becomes a relationship between the reinforcing material and the fillet weld above, then, between the surface and the one end portion of the reinforcement of the upper steel sheet may be fillet welded.
[0106]
　If the reinforcing material to form a reinforcing portion joined by overlapping face, superposed reinforcement to the upper steel plate, bonding the overlapping surfaces of the upper steel sheet reinforcement. Bonding is not particularly limited, may be performed by resistance welding such as spot welding or seam welding, even if other resistance welding for example by laser welding, is filled to the surface overlapped adhesive bond it may be carried out. Conditions for the bonding process may according to the conventional method, is not particularly limited.
[0107]
　For example, when joining at the spot welding, superposed reinforcement to the upper steel plate, so as to sandwich the two metal plates from both sides, the Domurajiasu type made of copper alloy electrodes tip diameter 6 ~ 8 mm, while pressed under a pressure of 1.5 ~ 6.0kN, 5 ~ 50 cycles (power supply frequency 50 Hz), at 4 ~ 15 kA, and energized to form a molten metal, cooling and solidifying, the weld having a diameter of about 5mm to form. In this case, the width and length of the weld becomes equivalent.
[0108]
　Then, between the end portion and the surface of the lower steel reinforcements, including an end portion of the upper steel plate is fillet welded to the relationship between the reinforcing material and the fillet weld above. For example, in 3.2mm height tc fillet welds plus the thickness ta of the reinforcing material and the thickness tb of the upper steel plate, the length Lc of the fillet weld, the length La and the corner of the reinforcement to match the total length Lb of the weld portion, the fillet weld.
[0109]
　When forming the reinforcing portion due to the reinforcing bead, reinforcing bead has to be formed prior to the formation of the fillet weld. Thus, as shown in FIG. 11 (b), one of the toe portion 250 of the fillet weld 220 is so located on the surface of the reinforcing beads 230.
[0110]
　Next, the surface of the reinforcing bead, and the end portion of the upper steel plate is fillet welded to the between the surface of the lower steel sheet becomes a relationship between the reinforcing bead and the fillet weld above. For example, in 3.2mm height tc fillet welds plus the thickness ta of the reinforcing bead and the thickness tb of the upper steel plate, the length Lc of the fillet weld, the length La and the corner of the reinforcing bead to match the total length Lb of the weld portion, the fillet weld.
[0111]
　Conditions of an arc welding in fillet welding may according to a conventional method, not particularly limited. For example, as the shielding gas, 100% CO 2 other gas, Ar gas and 3 ~ 20% CO 2 , etc. can be used a mixed gas of the gas, the welding current and voltage, the value undercut come out settings can be.
[0112]
　Welding wire to be used is not particularly limited, if it is possible to use high-strength steel sheet for wire, employing a material having a composition Vickers hardness HV of the weld metal is less than 500, delayed fracture suppression can, preferable.
[0113]
　Stress to improve the tensile strength of lap fillet weld joint of the present invention, the distance from the root portion of the fillet weld to the surface of the fillet weld, i.e. by throat thickness becomes longer, which concentrates on the root portion There is thought to be due to the dispersion.
[0114]
　Throat thickness D T , as shown in FIG. 15 (a), (b) , defined as the shortest distance from the root portion to the fillet weld surface. (A), when the welding bead of fillet weld is formed convexly, (b) shows an example in which the weld bead is formed into a concave shape.
[0115]
　As shown in FIG. 15 (c), if there is a gap upper and lower plates is the shortest distance from the root portion of the upper plate side to fillet welding surface, to fillet weld surface from the root portion of the lower plate side the shortest distance of the shorter and throat thickness.
[0116]
　According to the studies of the present inventors, the throat thickness of the fillet weld D T (mm), the average hardness of the fillet weld H F (HV), the thickness of the upper steel plate D 1 (mm) , hardness smaller hardness of the base material of the hardness and the upper steel HAZ softening of the fillet weld portion of the upper steel sheet H S when the (HV), (D T × H F ) / (D 1 × H S ) of 1.20 or more, and preferably a 1.50, it was found that the more the tensile strength is improved. Hardness is, here, is a Vickers hardness.
[0117]
　Further, the melting width of the lower steel sheet L b when a (mm), (L b × H F ) / (D 1 × H S satisfies the) ≧ 1.70, preferably by improving the tensile strength.
[0118]
　The average hardness of the fillet weld, a value obtained by averaging the Vickers hardness of the weld metal of the area shown in FIG. 2 in B. If the weld metal internal, measurement position and the number of measurements may be arbitrarily determined.
[0119]
　In order to improve the tensile strength of the welded joint more effectively, so as to satisfy the above relationship may be adjusted as appropriate welding conditions.
Example
[0120]
　[Example 1]
　Next, a description will be given of an embodiment of the present invention, conditions in examples are an example of conditions adopted for confirming the workability and effects of the present invention, the present invention is, It is not limited to this single example of conditions. The present invention does not depart from the gist of the present invention, as long as they achieve the object of the present invention, it is capable of adopting various conditions.
[0121]
　Length 100mm shown in Table 1, were prepared steel sheet width 25 mm. Further, the reinforcing member having a rectangular parallelepiped shape as shown in FIG. 3 (a) and FIG. 4, was manufactured by processing a steel plate of a tensile strength 1180 MPa. It shows the dimensions of the reinforcing member in Table 2. 3 (a), the right end of the reinforcing member is aligned with the right end of the upper steel plate 10a.
[0122]
[Table 1]

[0123]
[Table 2]

[0124]
　A combination of the steel sheet shown in Table 3, superimposed in longitudinal end portions of the overlapping margin X20mm of steel, further except for a part overlapped with the reinforcing member, and fillet welding using a welding wire shown in Table 3 Test to produce a piece. Table 3 shows the height and length of the fillet weld. Table Formula 1 in 3, the throat thickness of the welded portion D T (mm), the average hardness of the weld H F (HV), the thickness of the upper steel plate D 1 (mm), welding of the upper steel plate the hardness of HAZ softening portion and a smaller hardness of the hardness of the base material of the upper steel sheet H S (HV) and the time (D T × H F ) / (D 1 × H S represents the value of) (hereinafter, example 2, example 3, the same in Comparative example).
[0125]
　In addition, Table 4 shows the welding conditions of the fillet weld.
[0126]
[table 3]

[0127]
[Table 4]

[0128]
　Then, by holding the end portions of the prepared test pieces were subjected to tensile test. The tensile test was carried out at a tensile speed of 10mm / min. Table 5 shows the tensile strength at break point.
[0129]
[table 5]

[0130]
　Test No. 1-5, and 7-9, has performed fillet welding using a reinforcement, the tensile strength is high, broken portion becomes HAZ.
[0131]
　Test No. 6 is performed fillet welding without using a reinforcing member, since the base material strength is low, breaking point was the base metal.
[0132]
　Test No. 10, has performed a fillet welding without using a reinforcing material, the tensile strength is low, broken portion becomes weld metal.
[0133]
　Test No. 11, the reinforcing material for performing the fillet welding in a state of not being joined to the upper steel plate, not to obtain the effect of reinforcement, the tensile strength is low, broken portion becomes weld metal.
[0134]
　Example 2
　Length 100mm shown in Table 6, were prepared steel sheet width 25 mm. Further, the reinforcing member having a rectangular parallelepiped shape as shown in FIG. 3 (a) and FIG. 4, was manufactured by processing a steel plate of a tensile strength 1180 MPa. Table 7 shows the dimensions of the reinforcing member. 3 (a), the right end of the reinforcing member is aligned with the right end of the upper steel plate 10a.
[0135]
[Table 6]

[0136]
[Table 7]

[0137]
　A combination of reinforcing material and an upper steel plate shown in Table 8, superimposed except for some were bonded for 1 point spot welding substantially at the center of the stiffener. Nugget diameter (length and width of the junction) was performed such that the 6 mm.
[0138]
　Then, as the combination shown in Table 8, superimposed lower steel plates to those who join the upper steel reinforcement, to prepare a fillet weld to the test piece. At that time, it superimposed in overlapping margin X20mm the longitudinal ends of the upper steel sheet and lower steel plates. Table 8 shows the fillet weld height and length, a reinforcing material right weld length, unmelted width of the reinforcing member, the length and width of the joint. In addition, in Table 9 shows the welding conditions of the fillet weld.
[0139]
[Table 8]

[0140]
[Table 9]

[0141]
　Then, by holding the end portions of the prepared test pieces were subjected to tensile test. The tensile test was carried out at a tensile speed of 10mm / min. Table 10 shows the tensile strength at break point.
[0142]
[Table 10]

[0143]
　As a result of the fillet welding using a reinforcing member in the same manner as in Example 1, the tensile strength is high, broken portion becomes HAZ.
[0144]
　[Example 3]
　length 100mm shown in Table 11, were prepared steel sheet width 25 mm.
[0145]
[Table 11]

[0146]
　The shape reinforcing bead shown in FIGS. 11 (a) and 12 were formed on the upper surface of the upper steel plate. Also, toe 40 of the reinforcing bead, as shown in FIG. 11 (a), aligned with the end portion of the upper steel plate 10a. Table 12 shows the height of the reinforcing bead, the width and length.
[0147]
[Table 12]

[0148]
　Then, as the combination shown in Table 13, it superimposed the lower steel sheet obtained by forming the reinforcing bead to the upper steel plate to produce a fillet weld to the test piece. At that time, it superimposed in overlapping margin X20mm the longitudinal ends of the upper steel sheet and lower steel plates. Table 13 shows the height and length of the fillet weld. Also, Table 14 shows the welding conditions of the reinforcing bead and fillet weld.
[0149]
[Table 13]

[0150]
[Table 14]

[0151]
　Then, by holding the end portions of the prepared test pieces were subjected to tensile test. The tensile test was carried out at a tensile speed of 10mm / min. Table 15 shows the tensile strength at break point.
[0152]
[Table 15]

[0153]
　As a result of the fillet weld to form a reinforcing bead, Example 1, in the same manner as in Example 2, the tensile strength is high, broken portion becomes HAZ.
[0154]
　[Comparative Example]
　length 100mm shown in Table 16, were prepared steel sheet width 25 mm.
[0155]
[Table 16]

[0156]
　As shown in FIG. 16, a lower steel plate and the upper steel sheet of the present weld formed by fillet welding, further, subjected to multi-layer welding to form a reinforcing bead on top of the weld bead formed by fillet welding , a test piece was prepared. Overlap width X of the longitudinal ends of the upper steel plate and the lower steel plate was 20 mm. It indicates the height and length of the weld in Table 17. Also, Table 18 shows the welding conditions of the reinforcing bead and fillet weld.
[0157]
[Table 17]

[0158]
[Table 18]

[0159]
　Then, by holding the end portions of the prepared test pieces were subjected to tensile test. The tensile test was carried out at a tensile speed of 10mm / min. Table 19 shows the tensile strength at break point.
[0160]
[Table 19]

[0161]
　As a result of the fillet welding by multi prime, the effect of the tensile strength enhancing can not be obtained, broken portion became weld metal. This is some multiple prime, as shown in FIG. 16, throat thickness D T does not become large, since the welded portion is partially tempered in forming the reinforcing bead, softened region to the weld It is considered to be due to occur.
Industrial Applicability
[0162]
　According to the present invention, since the fillet weld is provided with reinforcing portions on the surface of the high strength steel sheet, without increasing the welding deformation of the welded joint, stress concentration to the root portion can be avoided, improving the tensile strength it can be. Accordingly, the present invention has high industrial applicability.
DESCRIPTION OF SYMBOLS
[0163]
　1a, 1b steel (base
　material) 2 weld bead (fillet
　welds) 10a upper steel plate
　10b lower steel plate
　20 welded bead (fillet
　welds) 30 reinforcing member
　40 weld bead (fillet
　welds) 120 weld bead (corner weld
　portion) 130 stiffener
　140 weld bead (fillet welds)
　220 fillet weld bead (fillet
　welds) 230 reinforcing beads
　240 toe portion of the reinforcing bead
　toe portion 250 fillet weld bead
　310 present weld (fillet welds)
　320 reinforcing bead
　ta reinforcing portion thickness of
　ta 'maximum height of the reinforcing bead
　thickness of tb upper steel plate
　height tc fillet weld
　height td fillet weld
　length of La reinforcement portion
　Lb, Lb1, Lb2 fillet weld total length
　Lc, Lc1, Lc2
　length of fillet weld reinforcement portion Ld, Ld1, Ld2 length of the weld
　width W reinforcing portion
　maximum width of W 'reinforcing bead
　Wa, Wa1, W a2 width of the joint portion
　unmelted width Wb reinforcing portion
　X maximum overlap width
　D T　throat thickness

claims

[Claim 1]A method of fillet welding overlay welding planned portion of the first steel plate and a second steel sheet,
　and the tensile strength of the first steel sheet 780MPa or more,
　the method is
　a surface of said first steel plate a is, the step of forming the first steel plate and a reinforcing portion bonded to the surface opposite to the surface in contact with the second steel sheet at the time of superimposing the second steel sheet,
　and the end portion of the reinforcing section a step of fillet welding as between cover has a weld metal with the first steel plate end portion and the second surface of the steel sheet of the
fillet welding method, which comprises a.
[Claim 2]
　The fillet the throat thickness of the fillet weld formed by welding D T (mm), the average hardness of the fillet weld H F (HV), the thickness of the first steel plate D 1 ( mm), the smaller hardness of the hardness of the base material hardness and a first steel HAZ softening of the fillet weld of the first steel sheet H S when the (HV), (D T × H F ) / (D 1 × H S fillet welding method according to claim 1) is characterized in that at least 1.50.
[Claim 3]
　Fillet welding method according to claim 1 or 2, wherein the reinforcing portion is a reinforcing material.
[Claim 4]
　End of the reinforcement, characterized in that the first a surface of the steel plate, fillet welding on the surface opposite to the surface in contact when superposed first steel plate and a second steel plate fillet welding method according to claim 3,.
[Claim 5]
　The reinforcing material, the a surface of the first steel plate, the surface in contact when superposed first steel plate and a second steel plate on the opposite side, the reinforcing member and the first steel plate fillet welding method according to claim 3, characterized in that joining by overlapping surface of the.
[Claim 6]
　The reinforcing portion is fillet welding method according to claim 1 or 2, characterized in that said first opposite weld bead formed on the surface of the second surface overlaying the steel of the steel sheet.
[Claim 7]
　The reinforcing portion is fillet welding method according to claim 1 or 2, characterized in that said formed by processing the first steel sheet.
[8.]
　A first steel plate and welded joint second steel plates are fillet welded,
　and at the first steel tensile strength 780MPa or more,
　a surface of said first steel plate, said first steel plate If a second steel plate and a second reinforcing portion bonded to the surface opposite to the surface in contact steel when superimposing,
　the end of the first steel sheet, the surface of the second steel plate, and having a fillet weld between the end of the stiffener
fillet welded joint, characterized in that.
[Claim 9]
　The throat thickness of the fillet weld D T (mm), the average hardness of the fillet weld H F (HV), wherein the thickness of the first steel plate D 1 (mm), the first steel plate hardness of HAZ softening of the fillet weld and a smaller hardness of the hardness of the base material of the first steel sheet H S when the (HV), (D T × H F ) / (D 1 × H S fillet weld joint according to claims)
[Claim 10]
　Fillet weld joint according to claim 8 or 9, wherein the reinforcing portion is a reinforcing material.
[Claim 11]
　End of the reinforcement, the first a surface of the steel sheet, fillet on a surface opposite to the surface in contact with the second steel sheet at the time of overlapping the said first steel plate and a second steel plate fillet weld joint according to claim 10, characterized in that welded.
[Claim 12]
　The reinforcing member is a surface of said first steel plate, the surface opposite the surface in contact with the second steel sheet at the time of overlapping the said first steel plate and a second steel plate, and the reinforcing member fillet weld joint according to claim 10, characterized in that the reinforcing material is joined at overlapping surfaces of the first steel plate.
[Claim 13]
　The reinforcing portion is fillet welded joint according to claim 8 or 9, characterized in that said first opposite weld bead formed on the surface of the second surface overlaying the steel of the steel sheet.
[Claim 14]
　The reinforcing portion is fillet welded joint according to claim 8 or 9, characterized in that it is formed by processing the first steel sheet.