Technical field
[One]
The present invention relates to a plated steel plate welding member and a method of manufacturing the same, and more particularly, to a plated steel plate welding member having excellent porosity resistance and fatigue properties of the welded portion, and a method of manufacturing the same.
Background
[2]
In the automotive field, research on technology to reduce weight of vehicle bodies and parts is emerging as a major issue due to policies to regulate fuel economy in accordance with environmental protection such as global warming. Chassis parts, which are important for vehicle driving performance, are also required to apply high-strength steel for weight reduction in accordance with this trend. In order to achieve weight reduction of parts, it is essential to increase the strength of the material, and guaranteeing the durability of parts made of high-strength steel in an environment where repeated fatigue loads are applied is an important factor.
[3]
In the case of arc welding, which is mainly used for securing strength when assembling automobile chassis parts, since overlapping joint welding is performed between parts by welding of welding wires, it is inevitable to give the geometric shape of the welding joint. This acts as a cyclic fatigue stress concentration part (notch effect) and becomes a fracture starting point, resulting in a decrease in the durability of the part, so the advantage of applying a high-strength steel material is lost.
[4]
As described above, it is important to reduce the angle of the end of the weld joint, which is the stress concentration part, that is, the toe angle, and control the material and stress of the toe part in order to improve the fatigue properties of the weld part. Can be said.
[5]
In addition, as described above, due to the thinning of the material due to the high strength and light weight of parts, the demand for rust prevention to prevent penetration corrosion has increased, so the adoption of plated steel is increasing. Pore ​​defects are sensitive to the problem of lowering the strength and fatigue properties of the weld.
[6]
On the other hand, application of Zn-Mg-Al-based high corrosion resistance alloy plated steel, which has far superior corrosion resistance than the existing hot dip galvanized steel sheet, is proposed, but the melting point and vaporization point of ternary alloy plating are lower than that of conventional zinc plating, so that the generation of plating vapor is more effective. Since it is sensitive, it is necessary to develop a technology to suppress the occurrence of pore defects in the welding area.
[7]
Prior Literature 1 proposes to set the gap of the overlapping joint in the range of 0.2 to 1.5mm in order to suppress the occurrence of pore defects in the arc welding of galvanized steel sheets, but the welding characteristics of the joint structure without gaps when the actual parts are applied. There are limitations that cannot be guaranteed.
[8]
In addition, in Prior Document 2, in order to suppress the occurrence of pore defects in the galvanized steel sheet arc welding, the application of a mixture of three gas mixtures of CO 2 and O 2 in Ar and a low-viscosity solid wire with limited contents of Si and Mn, etc. In addition, it is proposed to raise the arc position by 1 mm from the tip of the weld overlapping joint, but restrictions on the protective gas and welding material are inevitable, and there is a burden to keep the arc position constant when applying real parts.
[9]
(Patent Document 0001) Japanese Patent Laid-Open Publication No. 2016-101593
[10]
(Patent Document 0002) Japanese Patent Laid-Open Publication No. 2015-167981
Detailed description of the invention
Technical challenge
[11]
Embodiments of the present invention is to provide a plated steel plate welding member excellent in welded porosity and fatigue properties.
[12]
In addition, embodiments of the present invention is to provide a method of manufacturing a plated steel plate welding member having excellent weld porosity and fatigue properties.
Means of solving the task
[13]
A plated steel plate welding member having excellent weld porosity resistance and fatigue properties according to an embodiment of the present invention is a weld metal formed through arc welding by overlapping a first member and a second member laminated to partially overlap the first member. A toe angle (θ) of the welded metal part is 45° or less, and the first member and the second member are plated steel sheets.
[14]
In addition, according to an embodiment of the present invention, the plated steel plate may be a Zn-Mg-Al alloy plated or galvanized hot rolled steel plate.
[15]
In addition, according to an embodiment of the present invention, the hot-rolled steel sheet may have a tensile strength of 590 MPa or more and a thickness of 6 mm or less.
[16]
In addition, according to an embodiment of the present invention, the hot-rolled steel sheet may be 590FB steel.
[17]
In addition, according to an embodiment of the present invention, the pore area ratio formed in the weld metal portion may be less than 0.5%.
[18]
In addition, according to an embodiment of the present invention, the fatigue strength of the weld metal part is 250 MPa or more, and the fatigue life may be 2,000,000 cycles or more at a cyclic fatigue load of 10 kN (minimum/maximum load ratio, R=0.1).
[19]
A method of manufacturing a plated steel plate welding member having excellent weld porosity resistance and fatigue properties according to an embodiment of the present invention includes a first member and a second member that is partially overlapped on the first member by overlapping arc welding. Forming a welded metal part, wherein the first member and the second member are plated steel sheets, and during the arc welding, a welding current is supplied to the solid wire to generate an arc, and the welding current is a first As a pulse current that is repeated with the current of the peak and the second peak having a current value smaller than the first peak as one pulse cycle, the welding molten metal stirring wave frequency defined by the following formula (1) is repeated at 20 to 30 Hz. Perform.
[20]
1/(T H +T L ) --- Equation (1)
[21]
Here, T H is a period of the first peak, and T L is a period of the second peak.
[22]
In addition, according to an embodiment of the present invention, the solid wire may be supplied into a shield gas, which is an Ar gas containing 10 to 30% of CO 2 gas.
[23]
Further, according to an embodiment of the present invention, the welding current may be 200 to 300A.
[24]
In addition, according to an embodiment of the present invention, during the arc welding, solid wire diameter: 1.0 to 1.2mm, torch angle: 30 to 45°, push angle: 0 to 25°, welding speed: 0.6 to 1.0 m/min Can be done with.
[25]
Further, according to an embodiment of the present invention, the first member and the second member may be a Zn-Mg-Al alloy plated or galvanized hot-rolled steel sheet.
[26]
In addition, according to an embodiment of the present invention, the hot-rolled steel sheet may have a tensile strength of 590 MPa or more and a thickness of 6 mm or less.
Effects of the Invention
[27]
When manufacturing a plated steel plate welding member having excellent weld porosity and fatigue properties according to the embodiments of the present invention, it is possible to effectively reduce porosity defects in the weld metal part by optimizing the wave frequency of the welding current, and control the tow angle of the weld metal part. Thus, it is possible to reduce the concentration of fatigue stress on the welding toe. Accordingly, in order to secure high strength of parts such as automobile chassis members and rust prevention due to thinning, a high corrosion resistance plated steel plate can be used, and accordingly, a plated steel plate welding member having excellent weld porosity resistance and fatigue properties can be obtained.
Brief description of the drawing
[28]
1 is a photograph of a cross-section of a plated steel plate welding member having excellent weld porosity and fatigue properties according to an embodiment of the present invention.
[29]
2 is a photograph of the appearance of a welding part according to an embodiment of the present invention.
[30]
3 is an X-ray photograph of the appearance of a welding part according to an embodiment of the present invention.
[31]
4 is a photograph showing a result of a tensile rupture test of a plated steel plate welding member according to an embodiment of the present invention.
[32]
5 is a schematic view for explaining a welded metal part of a plated steel plate welding member according to an embodiment of the present invention.
[33]
6 is a graph for explaining a molten metal stirring wave frequency during arc welding of a plated steel sheet welding member according to an embodiment of the present invention.
Best mode for carrying out the invention
[34]
A plated steel plate welding member having excellent weld porosity resistance and fatigue properties according to an embodiment of the present invention is a weld metal formed through arc welding by overlapping a first member and a second member laminated to partially overlap the first member. A toe angle (θ) of the welded metal part is 45° or less, and the first member and the second member are plated steel sheets.
Mode for carrying out the invention
[35]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are presented in order to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited only to the examples presented here, but may be embodied in other forms. In the drawings, in order to clarify the present invention, portions not related to the description may be omitted, and the size of components may be slightly exaggerated to aid understanding.
[36]
1 is a photograph of a cross-section of a plated steel plate welding member having excellent weld porosity and fatigue properties according to an embodiment of the present invention. 2 is a photograph of the appearance of a welding part according to an embodiment of the present invention. 3 is an X-ray photograph of the appearance of a welding part according to an embodiment of the present invention. 4 is a photograph showing a result of a tensile rupture test of a plated steel plate welding member according to an embodiment of the present invention. 5 is a schematic view for explaining a welded metal part of a plated steel plate welding member according to an embodiment of the present invention.
[37]
1 to 5, according to a plated steel plate welding member having excellent weld porosity and fatigue properties according to an embodiment of the present invention, a first member and a second member stacked to partially overlap the first member. And a weld metal portion formed through arc welding to overlap the member.
[38]
At this time, the toe angle (θ) of the welded metal part is 45° or less.
[39]
The method of increasing the fatigue characteristics of the welding member can be largely divided into a method of using residual stress and a method of controlling bead shape.
[40]
In the case of the present invention, its purpose is to improve the fatigue properties of the welding member through the control of the bead shape, and for this purpose, the toe angle of the weld metal part is 45° or less (excluding 0°), more preferably One technical feature is that it is controlled to 35° or less (excluding 0°), and more preferably 30° or less (excluding 0°).
[41]
At this time, the tow angle is defined as a weld toe when the contact between the boundary line of the first member and the second member and the weld metal part in a cross section perpendicular to the welding line is defined as a weld toe as a reference point. And an angle between the boundary line of the second member and the tangent line of the bead curvature closest to the welding tow of the weld metal part.
[42]
By forming the tow angle to be 45° or less, it is possible to alleviate the stress concentrated on the welded metal part, thereby improving the fatigue characteristics of the welding member.
[43]
Although it is possible to improve the fatigue characteristics of the welded part by simply controlling the tow angle of the welded metal part as described above, it is more preferable to appropriately control the penetration depth of the welded metal part in order to maximize the effect, and according to an embodiment of the present invention According to this, the penetration depth of the welded metal part may be controlled to be 20% or more compared to the thickness of the second member. More preferably, the penetration depth of the weld metal part may be controlled to be 45% or more compared to the thickness of the second member. This is because, if the penetration depth of the welded metal part is insufficient, there is a risk that the weld metal part may be fractured starting from the bead root due to repeated fatigue loads.
[44]
In addition, the first member and the second member are plated steel sheets.
[45]
Therefore, by using a plated steel plate instead of a general hot-rolled steel plate, it is possible to secure rust prevention for preventing penetration corrosion due to the thinning of the material due to the high strength and weight reduction of recent parts.
[46]
For example, the plated steel plate may be a Zn-Mg-Al alloy plated or galvanized hot rolled steel plate. More preferably, the plated steel sheet may be a Zn-Mg-Al alloy plated hot rolled steel sheet having superior corrosion resistance than a galvanized hot rolled steel sheet.
[47]
For example, the hot-rolled steel sheet may have a tensile strength of 590 MPa or more and a thickness of 6 mm or less, and the hot-rolled steel sheet may be 590FB steel having a microstructure including ferrite and bainite.
[48]
For example, the pore area ratio formed in the weld metal part may be less than 0.5%.
[49]
In the case of welding the plated steel plate welding member according to the conventional arc welding method, when the plated layer contacts the welding arc, a large amount of pore defects such as pits or blowholes occurs due to the generation of plating vapor, reducing the strength and fatigue characteristics of the weld. There is a problem to make. In addition, in the case of Zn-Mg-Al high corrosion resistance alloy plated steel sheet, which has superior corrosion resistance compared to the existing galvanized steel sheet, the melting point and evaporation point of the ternary alloy plating are much lower, and the generation of plating vapor is higher. There is a problem with a higher incidence rate.
[50]
However, according to the manufacturing method including arc welding according to an embodiment of the present invention, such a problem is minimized so that not only a conventional galvanized steel sheet but also a Zn-Mg-Al-based high corrosion resistance alloy plated steel sheet is used. The pore area ratio formed in the weld metal part may be limited to less than 0.5%, preferably to 0%.
[51]
For example, the fatigue strength of the welded metal part is 250 MPa or more, and a fatigue life of 2,000,000 cycles or more can be secured under a cyclic fatigue load of 10 kN (minimum/maximum load ratio, R=0.1), indicating excellent weld fatigue characteristics. have. At this time, the fatigue strength (or fatigue limit) is defined as a value obtained by dividing the maximum fatigue load value at which the fatigue life is 2,000,000 cycles or more by the cross-sectional area of ​​the member.
[52]
In addition, according to the method of manufacturing a plated steel plate welding member having excellent weld porosity and fatigue properties according to an embodiment of the present invention, the first member and the second member stacked so as to partially overlap the first member are overlapped arc And forming a weld metal portion through welding.
[53]
First, after preparing the first member and the second member, a welding line is formed by laminating the second member on the first member so that at least a portion of the second member overlaps. Here, the welding line means an end portion of the second member among regions where the first member and the second member overlap.
[54]
The overlapping width of the weld joint may be applied to about 5 to 50 mm, but is not limited thereto.
[55]
At this time, the arc welding is performed while providing a shield gas along the formed welding line, and during the arc welding, a welding current is supplied to the solid wire to generate an arc to weld.
[56]
For example, the solid wire may be supplied into a shield gas, which is an Ar gas containing 10 to 30% of CO 2 gas. More preferably, the shielding gas may be Ar gas containing 10 to 20% of CO 2 gas.
[57]
That is, the shielding gas is an Ar gas, from 10 to CO of 30% 2 comprises a gas, CO 2 by the arc heat pinch force effect by the arc-up decreased if it contains a gas less than 10%, the plating vapor withdrawing effect If more than 30% of CO 2 gas is included, the arc heat pinch force effect due to arc contraction is excessive, and the effect of discharging plating vapor is reduced.
[58]
When the first and second members to be welded are plated steel sheets, for example, galvanized steel sheets, the zinc plated layer with a low boiling point becomes zinc gas due to arc heat during arc welding and floats to the top of the molten part. Most of these are released, but some remain in the molten part, and when solidified, a spherical cavity, a blowhole, is formed, and when zinc gas solidifies near the surface of the base metal, a small pits, or pits, are formed. For example, by using Ar gas containing a predetermined amount of CO 2 gas as the shielding gas, the arc force generated between the solid wire and the base material during gas shielded arc welding is increased, thereby greatly breaking the weld under the solid wire. I can go down. Accordingly, it is possible to facilitate the release of zinc gas generated in the lower part of the molten part, and in the case of gas shield arc welding, the penetration depth of the weld metal part can be further increased, and finally, the fatigue property of the welding part can be improved and pore defects Can be suppressed.
[59]
The solid wire may be used as a welding material, and for example, ER70S-3 (KC-25M) Φ1.2 soild wire may be applied, but is not particularly limited thereto.
[60]
For example, the welding current is a pulsed current that is repeated with a first peak and a second peak having a current value smaller than the first peak as one pulse cycle.
[61]
The pulsed current is repeatedly supplied with a welding molten metal stirring wave frequency defined by the following equation (1) at 20 to 30 Hz to perform welding.
[62]
1/(T H +T L ) --- Equation (1)
[63]
Here, T H is a period of the first peak, and T L is a period of the second peak.
[64]
6 is a graph for explaining a molten metal stirring wave frequency during arc welding of a plated steel plate welding member according to an embodiment of the present invention.
[65]
The welding molten metal stirring wave frequency is defined as 1/(T H +T L ) as shown in FIG. 6 . The frequency accordingly is repeatedly supplied in the range of 20 to 30 Hz, and pulsed current is supplied. If the frequency range thereof is too low or high, there is a problem that it is difficult to reduce pore defects due to a decrease in the plating vapor discharge effect.
[66]
For example, the welding current may be in the range of 200 to 300A.
[67]
More preferably, the lower limit of the welding current may be 225A or more, and the upper limit may be 270A or less. When the current is too low, the effect of discharging plating vapor is reduced due to a decrease in arc force, and on the contrary, when the current is too high, there is a problem in that the molten welded metal portion is unstable and the incidence of pore defects increases.
[68]
For example, during the arc welding, solid wire diameter: 1.0 to 1.2mm, torch angle: 30 to 45°, push angle: 0 to 25°, welding speed: 0.6 to 1.0m/min.
[69]
In the embodiment of the present invention, a gap of 0 mm is applied to the weld joint, but is not particularly limited thereto.
[70]
In addition, the first member and the second member are plated steel sheets, the plated steel sheet is a Zn-Mg-Al alloy plated or galvanized hot rolled steel sheet, and the hot rolled steel sheet may have a tensile strength of 590 MPa or more and a thickness of 6 mm or less. . Detailed descriptions of the first member and the second member are the same as described above, and thus will be omitted below.
[71]
[72]
Hereinafter, the present invention will be described in more detail through examples.
[73]
Examples 1 to 4 and Comparative Examples 1 to 6
[74]
After arranging two 2.2mm thick 590FB steel plates coated with Zn-Mg-Al with a plating amount of 90g/m 2 on both sides of the steel plate so that 20mm overlap each other, the connection part was arc-welded according to the conditions in Table 1 below to weld metal. To form a welding member.
[75]
[Table 1]
Shield gas Welding material Welding condition Welding pulse current frequency (Hz)
Example 1 Ar+20%CO 2 KC-25MΦ1.2 200A, 60cm/min 30
Example 2 Ar+20%CO 2 KC-25MΦ1.2 225A, 60cm/min 30
Example 3 Ar+20%CO 2 KC-25MΦ1.2 225A, 80cm/min 30
Example 4 Ar+20%CO 2 KC-25MΦ1.2 225A, 100cm/min 30
Comparative Example 1 Ar+30%CO 2 MIX-ZnΦ1.0 200A, 80cm/min 20
Comparative Example 2 Ar+30%CO 2 MIX-ZnΦ1.0 220A, 80cm/min 20
Comparative Example 3 Ar+20%CO 2 KC-25MΦ1.2 200A, 100cm/min 0
Comparative Example 4 Ar+20%CO 2 KC-25MΦ1.2 300A, 100cm/min 0
Comparative Example 5 Ar+20%CO 2 KC-25MΦ1.2 200A, 60cm/min 20
Comparative Example 6 Ar+20%CO 2 KC-25MΦ1.2 250A, 80cm/min 20
[76]
By observing the weld metal part of the welding member, the presence or absence of pit generation and the pore area ratio were measured, and are shown in Table 2 below.
[77]
[Table 2]
Presence or absence of pit Pore ​​area ratio (%)
Example 1 X 0.0
Example 2 X 0.0
Example 3 X 0.0
Example 4 X 0.0
Comparative Example 1 O 2.5
Comparative Example 2 O 7.4
Comparative Example 3 O 1.6
Comparative Example 4 O 4.1
Comparative Example 5 O 0.6
Comparative Example 6 O 2.4
[78]
5 is a schematic view for explaining a welded metal part of a plated steel plate welding member according to an embodiment of the present invention.
[79]
Referring to FIG. 5, the width of the weld metal part, that is, the leg length of the weld is indicated by L, the thickness of the second member is indicated by h1, and from the top edge of the second member to the tow part on the first member. The distance from the straight line of, to the contact point of the first and second members and the weld metal part is represented by d, the distance to the highest surface of the weld metal part was represented by r, the penetration depth was represented by p, and the tow angle was represented by θ. I did. Accordingly, the results of observing the size of the weld metal part of the embodiments of the present invention are shown in Table 3 below.
[80]
[Table 3]
h1 (mm) L (mm) r (mm) d (mm) p (mm) Tow angle (°)
Example 1 2.2 6.0 1.8 1.6 1.2 38
Example 2 2.2 6.2 1.8 1.6 1.4 33
Example 3 2.2 5.9 1.8 1.7 2.1 30
Example 4 2.2 4.8 1.4 1.7 One 44
[81]
Referring to the above, it is possible to secure the tow angle of the welding metal part of the welding member according to an embodiment of the present invention to be 45° or less, and in the plated steel plate welding member because pits and pores do not occur in the welding metal part. Porosity is improved, and the welded metal part can secure a fatigue strength of 250 MPa or more, thereby increasing the range of use of high-strength plated hot-rolled sheet steel for thinning and weight reduction of parts such as automobile chassis members.
Industrial availability
[82]
The plated steel sheet welding member having excellent weld porosity and fatigue properties according to embodiments of the present invention and a manufacturing method thereof can be applied to parts such as automobile chassis members.
Claims
[Claim 1]
A first member and a weld metal portion formed by overlapping arc welding of a second member laminated to partially overlap the first member, and a toe angle (θ) of the weld metal portion is 45° or less, The first member and the second member are plated steel plate welding members having excellent porosity resistance and fatigue properties of the welded portion.
[Claim 2]
The plated steel plate welding member according to claim 1, wherein the plated steel plate is a Zn-Mg-Al alloy plated or galvanized hot-rolled steel plate having excellent porosity resistance and fatigue properties of a weld.
[Claim 3]
The plated steel sheet welding member according to claim 2, wherein the hot-rolled steel sheet has a tensile strength of 590 MPa or more and a thickness of 6 mm or less.
[Claim 4]
4. The plated steel plate welding member according to claim 3, wherein the hot-rolled steel plate is 590FB steel and has excellent weld resistance porosity and fatigue properties.
[Claim 5]
The plated steel plate welding member according to claim 1, wherein the pore area ratio formed in the weld metal part is less than 0.5%.
[Claim 6]
The plated steel sheet welding member according to claim 1, wherein the weld metal part has a fatigue strength of 250 MPa or more, and a fatigue life of 2,000,000 cycles or more at a cyclic fatigue load of 10 kN (minimum/maximum load ratio, R = 0.1). .
[Claim 7]
Forming a weld metal part by overlapping arc welding of the first member and the second member stacked on the first member to partially overlap, wherein the first member and the second member are plated steel sheets, and the During arc welding, a welding current is supplied to the solid wire to generate an arc, but the welding current is a pulse that is repeated by applying the first peak and the second peak having a current value smaller than the first peak as a period of one pulse. As a current, the welding molten metal stirring wave frequency defined by the following formula (1) is repeatedly performed at 20 to 30 Hz, a method of manufacturing a plated steel plate welding member having excellent porosity resistance and fatigue properties of the weld. 1/(T H +T L ) --- Equation (1) Here, T H is the period of the first peak, and T L is the period of the second peak.
[Claim 8]
The method of claim 7, wherein the solid wire is supplied into a shield gas, which is an Ar gas containing 10 to 30% of CO 2 gas.
[Claim 9]
[8] The method of claim 7, wherein the welding current is 200 to 300A.
[Claim 10]
According to claim 7, In the arc welding, solid wire diameter: 1.0 to 1.2mm, torch angle: 30 to 45°, push angle: 0 to 25°, welding speed: 0.6 to 1.0 m/min. A method of manufacturing a plated steel plate welding member with excellent porosity resistance and fatigue properties.
[Claim 11]
The method of claim 7, wherein the first member and the second member are Zn-Mg-Al alloy plated or galvanized hot-rolled steel plates having excellent weld porosity resistance and fatigue properties.
[Claim 12]
The method of claim 11, wherein the hot-rolled steel sheet has a tensile strength of 590 MPa or more and a thickness of 6 mm or less, and has excellent porosity resistance and fatigue properties of a welded steel sheet.