Technical field
[0001]
The present invention includes a consumable electrode gas-shield arc welding method, a arc welding unit obtained by the consumable-electrode gas-shield arc welding method.
This application, on January 20, 2016, claiming priority on Japanese Patent Application No. 2016-008695 filed in Japan, the contents of which are incorporated herein.
BACKGROUND
[0002]
Gas shielded arc welding is widely used in various fields, for example, it has been used in welding, such as underbody member in the automotive field.
The shield gas when the steel members to a gas shielded arc welding using a solid wire, CO 2 100% of the gas, or, Ar and CO 2 mixed gas of is used. However, CO 2 when welding using a shielding gas containing an oxidizing gas such as oxygen contained in the oxidizing gas shielding gas reacts with elements such as Si and Mn contained in the steel and wire, Si Si mainly of oxides and Mn oxides, Mn slag is produced. As a result, like the surface of the weld bead is melt-solidified portion Si, as Mn slag much remains.
[0003]
A car or underbody members, the member that requires corrosion resistance, electrodeposition coating is performed after welding assembly. In making this electrodeposition coating, if the surface of the arc welding unit Si, the Mn slag remains, electrodeposition coating of this portion is deteriorated. As a result, not adhere paint, Si, corrosion resistance point of Mn slag appears on the surface occurs will reduce (see FIG. 8).
[0004]
Why Si, electrodeposition coatability in the remaining portion of the Mn slag drops are Si oxide and Mn oxide insulator, can not be energized during coating, coating is because it does not adhere to the entire surface.
　The Si, Mn slag is a by-product of the deoxidation process of the weld, also, because an effect of stabilizing the arc itself, the gas-shielded arc welding using a solid wire or the like, the Si, the Mn slag it is difficult to prevent the occurrence. As a result, corrosion of the welded portion in electrodeposition coating was member was inevitable.
　Therefore, in the design of automobile underbody member, considering thinning due to corrosion, it has been made the thickness design of the thick, this becomes an obstacle for thinning by the use of high tensile steel.
[0005]
　With respect to such problems, by reducing the amount of Si, Mn slag generated in the gas-shielded arc welding, in order to improve the electrodeposition coatability, conventionally, the following measures have been proposed.
[0006]
　For example, Patent Document 1, oxidizing gas shielding gas is oxygen supply decrease of (CO 2 , O 2 has proposed a method of reducing the amount of slag is an oxide by limiting the amount of).
[0007]
　Patent Document 2, a shielding gas consisting of inert gas is supplied toward the consumable electrode, the consumable-electrode gas-shield for supplying an additive gas comprising a mixed gas of an oxidizing gas and the inert gas toward the molten pool edge It has proposed an arc welding method. According to this welding method, while stabilizing the arc, it can be suppressed to an extremely low concentration of dissolved oxygen in the weld metal.
[0008]
　Patent Document 3 proposes a gas shielded metal arc welding method using a welding wire of the total Si amount limited component composition in 0.04 to 0.2% of the welding wire and the base metal.
CITATION
Patent Document
[0009]
Patent Document 1: Japanese Patent 2012-213801 JP
Patent Document 2: Japanese Patent 2007-044736 JP
Patent Document 3: Japanese Patent Laid-Open 8-33997 discloses
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　However, in the technique Patent Documents 1-3, not sufficient from the viewpoint of eliminating the generation of insulating slag. In particular, the high-tensile steel sheet containing a large amount of Si or Mn, there is a problem that Si caused by Si and Mn contained in the base material, the Mn slag frequently occurs. Further, CO of shielding gas as in Patent Document 1 2 and O 2 reducing the amount of, the ratio of Ar increases, the cost becomes high, and an arc is wobbles during welding, that bead shape is deteriorated There's a problem. Further, there is as in Patent Document 3, when the deoxidizing element is small, insufficient deoxidation of the weld metal, the problem that blowholes are easily generated.
[0011]
　The present invention, Si, and to provide a consumable electrode gas-shield arc welding method and an arc welding unit weld electrodeposition coating defect portion due to Mn slag is not generated can be formed.
Means for Solving the Problems
[0012]
　The gist of the present invention is as follows.
[0013]
(1) the first aspect of the present invention, there is provided a consumable electrode gas-shield arc welding method of arc welding the two steel plates with a welding torch having a consumable electrode, oxygen represented by the following formula (A) weld bead potential α is the shielding gas is 1.5% to 5%, performed arc welding while feeding toward the consumable electrode from the welding torch is in a state of 700 ° C. or higher, which is formed by the arc welding and to the weld toe, the oxidation-promoting gas oxygen potential β is 15% to 50% represented by the following formula (B), sprayed at a flow rate of 1 ~ 3m / sec, the consumable-electrode gas-shield arc welding it is a method.
alpha = 100 × ([V 1 (O 2 )] + [V 1 (CO 2 )] / 5) / ([V 1 (X)] + [V 1 (O 2 )] + [V 1 (CO 2 )]) ··· (A) formula beta = 100 × [V 2 (O 2 )] / ([V 2 (X)] + [V 2 (O 2
)] + [V 2 (CO 2 )]) · · · (B) formula
,
where, [V 1 (X)] is the mixing ratio of the inert gas contained in the shielding gas
(vol%), [V 1 (O 2 )] is the mixing ratio of oxygen contained in the shielding gas
(vol%), [V 1 (CO 2 a)] is the mixing ratio of the carbon dioxide contained in the shielding gas
(vol%), [ V 2 (X)] is the mixing ratio of the inert gas used in the oxidation promoting gas
(vol%), [V 2 (O 2 in) the mixing ratio of oxygen contained in the oxidation-promoting gas (vol%)
There, [V 2 (CO 2 )] is the mixing ratio of the carbon dioxide contained in oxidation-promoting gas (vol%).
[0014]
(2) In the consumable-electrode gas-shield arc welding method according to (1), wherein the oxidation-promoting gas is formed between the welding torch and, the outer peripheral wall which is spaced apart outwardly from the outer peripheral surface it may be blown through the space defined.
[0015]
(3) In the above (1) or a consumable-electrode gas-shield arc welding method according to (2), the oxidation-promoting gas, the weld bead and at least a portion of the weld toe in the state of more than 700 ° C. in a state where the upper region enclosed, it may be blown to the upper region.
[0016]
(4) In the above (1) to (3) any consumable-electrode gas-shield arc welding method according to one of the sites to be sprayed is the oxidation promoting gas of the weld bead and weld toe, the horizontal shortest distance between the tip position of consumable electrodes may be not more than 35 mm.
[0017]
(5) The second aspect of the present invention, the above (1) to an arc welding unit formed by the consumable-electrode gas-shield arc welding method according to any one of the weld bead (4) surface, and the surface of the weld toe of the weld bead is arc welding unit covered with a conductive iron oxide slag containing either or both magnetite and wustite.
[0018]
(6) In the arc welding unit according to (5), the thickness of the conductive iron oxide slag may be 10 [mu] m ~ 50 [mu] m.
[0019]
(7) In the above (5) or the arc welding unit according to (6), wherein the surface of the weld bead, and the entire surface of the weld toe of the weld bead covered with the conductive iron oxide slag it may be cracking.
Effect of the invention
[0020]
　According to the method described in the above (1) to (4), the weld bead and the surface of the weld toe in the state of 700 ° C. or higher, which is formed by arc welding, exposed to oxygen potential β is higher oxidation promoting gas is will be. Therefore, it is possible to cover the surface of the weld bead and the weld bead toe portion of a conductive iron oxide slag, insulating Si, Mn slag is prevented from appearing on the surface. Therefore, even if the structural member of the electrodeposition coating comprising weld without electrodeposition coating failure occurs in the weld, and thus it is possible to increase the corrosion resistance of the structural member.
[0021]
　In particular, according to the method described in (2), oxidation-promoting gas is blown to the weld toe and the weld bead through an outer periphery formed in a space of the welding torch. Therefore, more reliably, to the weld bead in the state of 700 ° C. or higher, which is formed by arc welding and weld toe, it is possible to blow oxidation promoting gas, the surface of the weld bead and the weld bead toe portion it can be covered with a conductive iron oxide slag. Furthermore, it is possible to increase also the construction of the welding.
[0022]
　Further, according to the method described in (3), for blowing an oxidizing promoting gas into the region in a state of surrounding the upper region of the weld bead and weld toe in the direction of travel behind the welding torch, advanced oxidation it can be blown to the weld bead while maintaining the high concentration gas and weld toe. Therefore, more reliably, the surface of the weld bead and the weld bead toe portion can be covered with a conductive iron oxide slag.
[0023]
　Further, according to the method described in (4), by setting the distance D below 35 mm, more reliably, a weld bead in the 700 ° C. or more states formed by arc welding weld toe a hand, can be sprayed prooxidant gas, the surface of the weld bead and the weld bead toe portion can be covered with a conductive iron oxide slag.
[0024]
　(5) In the arc welding unit according to (7) appearance, since the surface of the weld bead and weld toe is covered with a conductive iron oxide slag, insulating Si, Mn slag to the surface It is not to be. Therefore, even if the structural member of the electrodeposition coating comprising weld without electrodeposition coating failure portion is generated in the welded portion, and thus it is possible to increase the corrosion resistance of the structural member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025]
[FIG. 1A] is a vertical sectional view for explaining a consumable electrode gas-shield arc welding method according to an embodiment of the present invention.
[FIG 1B] is a top view illustrating a consumable electrode gas-shield arc welding method according to the embodiment.
Is a view seen from below the oxidation promoting gas blowing device used in FIG. 2 consumable electrode gas-shield arc welding method according to the embodiment.
[FIG 3A] is a longitudinal sectional view for explaining an oxidation promoting gas blowing device according to the first modification.
[FIG 3B] is a top view for explaining an oxidation promoting gas blowing device according to the modification.
4 is a cross-sectional view of a welding torch for explaining an oxidation promoting gas blowing device according to a second modification.
[5] Comparative Example using no oxidation promoting gas G2 (Experimental Example 16), comparative example in which 10.0% of oxygen potential β of the oxidation promoting gas G2 (Experimental Example 19), and, the oxygen of the oxidation promoting gas G2 for an invention example where the potential β was 15.0% (experiment 2) is a photograph showing post-weld appearance, after painting appearance, and corrosion after appearance.
[6] appearance showing a comparative example in which 10.0% of oxygen potential β of the oxidation promoting gas G2 (Experimental Example 19), Si, a state in which a part of Mn slag is substituted with Fe-based oxide photo shows (left) and the SEM photograph
is a schematic illustration showing the effect of in FIG. 7 invention example, compared with the technique of Patent documents 1-3.
8 is a cross-sectional view perpendicular to a view for explaining the structure of the weld by conventional welding methods steel.
DESCRIPTION OF THE INVENTION
[0026]
　The consumable electrode gas shielded arc welding, from the viewpoint of arc stability, mixing forced a predetermined amount of oxidizing gas to the shielding gas. As a conventional measure for suppressing the electrodeposition coating defects, measures to reduce the amount of oxidizing gas shielding gas, or, Si reduces the oxidizing component in the consumable electrode (filler wire), the amount of Mn slag when adopting measures to reduce, there is a possibility that adverse effects will occur in the weld quality.
[0027]
　Accordingly, the present inventors used a conventional shielding gas and the welding wire, as a result of evaluating the slag occurrence and electrodeposition coating of the welded portion in various welding conditions, in excessively high criteria of heat input Si, Mn slag is reduced, electrodeposition coating properties were found tends to be improved. Furthermore, observation of the surface of the weld bead and weld toe at these welding conditions, the iron oxide having conductivity on a surface layer of the weld bead (FeO, Fe 3 O 4 was confirmed that)
[0028]
　Since the cooling rate of the weld metal slows down the welding conditions of high heat input, it tends to deviate from the area where the weld bead high temperature after melt-solidification and weld toe is protected by shielding gas. As a result, the weld toe hot weld bead is accelerated oxidation is exposed to the atmosphere, the surface of the weld bead and weld toe is believed to have been covered with iron oxide.
[0029]
　Based on the above findings, the present invention, rather than prevent oxidation of the welded portion, by actively oxidize solidified weld bead and the surface of the weld toe, the iron oxide having conductivity (FeO , Fe 3 O 4 and Si oxide to produce a)
[0030]
　This tendency to increase the welding speed, uniquely determined but was also confirmed by spreading the molten pool in the traveling direction rearward, generally welding conditions by the plate thickness and the form of the joint of the applied steel sheet is intended to be, it can not be freely set for the purpose of controlling the amount of formation of slag. Increase in excessive heat input leads to burn through steel plate, faster welding speed leads to failure of the weld bead shape.
　Accordingly, the present inventors does not depend on the heat input and speed, for the purpose of forming a stable iron oxide film on the surface of the weld bead were studying.
[0031]
　As a result, the conventional welding direction of the arc welding torch relative to the weld bead and weld toe of a high temperature state in the rear, if Fukitsukere high oxidation-promoting gas G2 oxygen potential beta, the weld bead and weld toe can be eliminated lower shielding gas G1 oxygen potentials α remaining on the surface, the weld bead and oxide of iron on the surface of the weld toe is accelerated, formed by reaction with oxidizing gas shielding gas including Si and Mn oxides, newly found that the surface of the weld bead and weld toe can be covered with an iron oxide having conductivity, leading to the present invention.
[0032]
　It is described in detail below with reference to the drawings Embodiments of the present invention made based on the above findings.
[0033]
　1A, 1B is a schematic view for explaining a gas-shielded arc welding method according to the present embodiment.
　In gas shielded arc welding method according to the present embodiment, Figure 1A, as shown in 1B, the welding torch 1 having a consumable electrode, oxidation-promoting gas which extends toward the opposite side of the welding direction of the welding torch 1 using the spray nozzle 22 (Food nozzles 22A), to weld the two sheets of steel plates.
[0034]
　In this embodiment, a conductive iron oxide slag generated in the course of the consumable-electrode gas-shield arc welding, the surface of the weld bead 81, and, at the boundary of the weld bead 81 and the steel (base material) covering the surface of a weld toe 82. Thus, the resulting insulating Si during welding, to confine Mn slag in the conductive iron oxide slag 9.
[0035]
　Slag that may be generated during welding, as having a conductive, magnetite (Fe 3 O 4 is known to have)
　Therefore, on the surface of the molten pool 8, or weld bead 81 and to promote the oxidation of iron on the surface of the weld toe 82, magnetite and wustite main conductive iron oxide slag 9 by covered arc welding parts it is necessary to obtain.
[0036]
　During welding, by exposing the surface of the weld bead 81 and the weld toe 82 of the high temperature to an oxidizing atmosphere, can magnetite or wustite is an iron oxide is formed and the surface of the weld bead 81, and weld toe the surface of the end portion 82 may be covered with a conductive iron oxide slag containing one or both of magnetite and wustite.
　Incidentally, not only the surface and the surface of the weld toe 82 of the weld bead 81, also the surface of the molten pool 8 outside than shielding region formed by the shield gas G1 from the welding torch 1 is exposed to an oxidizing atmosphere it is preferable.
[0037]
　In this embodiment, to facilitate the oxidation of iron by blowing separately from the oxygen potential β is high oxidation-promoting gas G2 toward the surface of the surface and the weld toe 82 of at least the weld bead 81 shielding gas G1, welding the surface of the bead 81 and the weld toe portion 82 covering the iron oxide slag conductivity.
[0038]
　According to gas-shielded arc welding method according to the present embodiment, when the consumable electrode gas shielded arc welding, the oxygen potential α is lower shielding gas in consumable electrode consisting of inert gas or an oxidizing gas and an inert gas towards supplied, and immediately thereafter, blow towards the weld bead 81 and weld toe 82 of at least a high temperature state oxygen potential β is higher oxidation promoting gas G2 comprising a mixed gas of an oxidizing gas and an inert gas. Thus, covered with weld bead 81 and weld toe 82 are all conductive iron oxide slag, insulating Si, a weld Mn slag is buried in the iron oxide slag conductive it is possible to obtain.
[0039]
　Whether conducting iron oxide slag is formed, the composition of the surface of the weld bead 81 and weld toe 82 and be examined by elemental mapping by EPMA, it can be confirmed by examining the conductivity.
　By cutting the range of weld bead 81 and its weld toe 82 after welding using oxidizing promoting gas G2 as described above, polishing the cut surface, the elemental mapping by EPMA, the weld bead 81 a its vicinity of the surface observed by the cross section of the weld toe 82, it is covered with a conductive iron oxide slag, the outermost surface of the conductive iron oxide slag is substantially iron oxide and that it, insulating Si, Si oxide and Mn oxide to form a Mn slag can be sure that little present in the outermost surface of the weld bead 81 and the weld toe 82.
[0040]
　Further, the surface of the iron oxide slag using a commercial tester, weld bead 81, by measurement of conduction between the outer surface of the steel sheet of the weld toe 82, conduction in the resistance value of 40 ~ 1000 [Omega] to confirm the sex. The surface on an insulating Si of the weld bead 81 and weld toe 82, the Mn slag is present, the electrical resistance is measured in a common commercial testers become measurement range infinity or normal conductor it can not be.
[0041]
(Welding torch 1)
　the welding torch 1, between the peripheral wall portion surrounding it with consumable electrode 5 is configured such that the passage of shielding gas G1. While shielding gas G1 from the welding torch 1 is supplied toward the consumable electrode 5, along a weld line formed between the steel member disposed in the welding position, arc welding is performed.
[0042]
(Consumable electrode 5)
　consumable electrode 5 is not particularly limited, Si in the molten pool 8, in order to minimize the occurrence of Mn slag, Si content is less than 1 mass%, Mn content is it is desirably 2 mass% or less.
[0043]
(Shield gas G1)
　shielding gas G1 is an inert gas O mainly such as Ar and the He 2 and / or CO 2 are mixed gas obtained by mixing, consumable electrode 5 (the welding wire) from the welding torch 1 and arc and it flows out toward the area surrounding the plasma. The role of shielding gas G1 is the atmosphere of generating area of the arc plasma in addition to replacing the atmosphere, because it is possible to ensure the stability of the arc, the following (1) oxygen potential α is 1.5% represented by formula or more, preferably 2.0%, as more preferably a 4.0%, inert gas, O 2 , CO 2 mixing ratio of is adjusted.
[0044]
α = 100 × ([V 1 (O 2 )] + [V 1 (CO 2 )] / 5) / ([V 1 (x)] + [V 1 (O 2 )] + [V 1 (CO 2 )]) · · · (1)式
[0045]
　In the above
(1), [V 1 (X)] is the mixing ratio of the inert gas contained in the shielding gas G1
(vol%), [V 1 (O 2 )] is the oxygen contained in the shielding gas G1 a mixing ratio
(volume%), [V 1 (CO 2 is a)] is the mixing ratio of the carbon dioxide contained in the shielding gas G1 (% by volume).
[0046]
　On the other hand, when the oxygen potential α shielding gas G1 is more than 5%, the excess Si on the surface of the molten pool 8, since the Mn slag is produced, even by blowing oxidizing promoting gas G2 after weld bead 81 and the surface of the weld toe 82 can not be covered with a conductive iron oxide.
　Therefore, the oxygen potential α 5% shielding gas G1 or less, preferably 4.5% or less, as more preferably equal to or less than 4.0%, O 2 and / or CO 2 content of is adjusted.
[0047]
(Oxidation-promoting gas G2)
　is oxidation-promoting gas G2, an inert gas (nitrogen or argon or He, etc.), O 2 , and CO 2 is a gas mixture obtained by mixing two or more kinds of the air (O 2 : 15% to 25% nitrogen: 75% to 85%) is convenient to be used. It is also possible to adjust the degree of progress of even when using air, adding more oxygen gas oxidation.
[0048]
　The oxidation-promoting gas G2, sprayed in the region of the weld bead 81 and weld toe 82 rearward of 700 ° C. or more molten pool 8. The role of the oxidation promoting gas G2 is weld bead 81 and to accelerate the oxidation of the iron on the surface of the weld toe 82, Si insulating formed by melt pool 8, conductive iron oxides of Mn slag ( FeO, Fe 3 O 4 for is to replace the), the following (2) oxygen potential β of 15% indicated by the formula, preferably 20% or more, as more preferably is 25% or more, an inert gas, O 2 , CO 2 mixing ratio of is adjusted.
[0049]
β = 100 × [V 2 (O 2 )] / ([V 2 (x)] + [V 2 (O 2 )] + [V 2 (CO 2 )]) · · · (2)式
[0050]
　In the above equation
(2), [V 2 a (X) the mixing ratio of the inert gas used in the oxidation promoting gas G2 is
(vol%), [V 2 (O 2 contained in) the oxidation-promoting gas G2 is a mixing ratio of oxygen
(vol%), [V 2 (CO 2 is a)] is the mixing ratio of the carbon dioxide contained in oxidation-promoting gas G2 (vol%).
[0051]
　In the shielding gas G1 and oxidation-promoting gas G2 CO 2 effects are different.
　CO arc plasma is contained in the shielding gas G1 to be used in areas that occur 2 acts as an oxidizing gas to dissociate the plasma heat.
　On the other hand, CO contained in the oxidation-promoting gas G2 used in iron melting point (about 1500 ° C.) below the area 2 is stable CO 2 acts as an inert gas due to the presence of a.
　Therefore, the oxygen potential β of the oxidation promoting gas G2, CO in the formula of the molecule different from the oxygen potential α shielding gas G1 2 not included.
[0052]
　The thickness of the iron oxide formed by the oxidation promoting gas is 10 ~ 50 [mu] m, the thickness of the iron oxide film formed on the surface of the weld bead 81 only in normal shielding gas G1, i.e., Si, Mn slag generation unit thicker than the thickness of the oxide film formed on the outside of the area (approximately 5μm at most).
[0053]
(Oxidation-promoting gas blowing means 20)
　in the gas shielded arc welding according to the present embodiment, when welding the steel member by a gas shielded arc welding while supplying the shielding gas G1, the oxidation-promoting gas blowing device 20, the consumable electrode 5 and on the surface of the rear of the weld bead 81 and weld toe 82 the welding torch 1, blowing the oxidation promoting gas G2 containing an oxidizing gas. Thus, to cover the surface of the weld bead 81 and weld toe 82 of a conductive iron oxide layer. The oxidation-promoting gas G2, may be sprayed in molten pool 8 behind the consumable electrode 5 and the welding torch 1 unless exacerbate bead appearance.
[0054]
　Weld bead 81 and the weld toe 82 oxidation-promoting gas blowing means 20 for blowing oxidizing promoting gas G2 to the surface of the oxidation-promoting gas blowing an oxidizing promoting gas supply unit 21 for supplying a pro-oxidant gas G2, the oxidation-promoting gas G2 and a spray nozzle 22.
[0055]
　The oxidation-promoting gas blowing nozzle 22, FIG. 1A, FIG. 1B, the hood nozzle 22A as shown in FIG. 2 is illustrated. The hood nozzle 22A has a side surface depending from a rectangular top surface and its edges are shaped to surround the upper region of the weld bead 81 and weld toe 82 of the periphery of the welding torch 1. On the upper surface of the hood nozzles 22A, with one longitudinal end to the oxidation-promoting gas supply unit 21 is provided, the welding torch 1 in the longitudinal direction of the other end can be inserted torch through hole 30 is formed.
[0056]
　The oxidation-promoting gas G2, in the welding torch 1 torch insertion hole 30 is inserted into the hood nozzle 22A in a state of being integrated, it is supplied from the oxidation-promoting gas supply unit 21, and the surface and the weld bead 81 of molten pool 8 on the surface of the weld toe 82 is blown while maintaining a high oxygen potential beta.
[0057]
　Incidentally, food nozzles 22A may be integrated manner at the distal end of the oxidation-promoting gas supply unit 21 may be detachable manner.
　Also, hood nozzle 22A is what is downward as in FIG. 2 was released, it is possible to employ any of those numerous gas blowout holes on the bottom surface in a box shape is formed. Moreover, even those lower is released, may be one gas lens 10, such as a wire mesh in the vicinity of open end portions attached. Furthermore, a partition wall provided inside the vicinity of the welding torch 1 can be so oxidation-promoting gas G2 does not interfere with the flow of shielding gas G1.
[0058]
　In the welding movement, the shielding gas G1 is discharged from the welding torch 1, while being shielded the surrounding ambient and the molten pool 8 of the arc 6 generated from consumable electrode 5, the welding torch 1 in the arrow direction along the weld line 11 make. At that time, the oxidation-promoting gas supply unit 21 provided at the rear of the hood nozzles 22A, oxidation-promoting gas G2 containing an oxidizing gas is supplied into the hood nozzle 22A, the surface of the weld bead 81 weld toe 82 oxidation-promoting gas G2 is blown.
[0059]
(Range blown prooxidant gas G2)
　when the surface temperature of the weld bead 81 weld toe 82 is 700 ° C. or more, significantly oxidation reaction with oxidizing gas and Fe in the oxidation-promoting gas G2 Occur. Therefore, in order to form an iron oxide slag conductivity on the surface of the weld bead 81 and weld toe 82, part surface temperature of the weld bead 81 weld toe 82 is 700 ° C. or higher, more preferably the site is 750 ° C. or higher, with respect to the site is more preferably 800 ° C. or higher, spraying prooxidant gas G2.
　The surface temperature of the weld bead 81 weld toe 82 can be measured by a radiation thermometer. Also, the relationship between the iron color and temperature may be sure that the above 700 ° C..
[0060]
　As described above, the oxidation promoting gas G2 needs to be sprayed on the site surface temperature of the weld bead 81 weld toe 82 is 700 ° C. or higher. Thus, a portion oxidation-promoting gas G2 is blown out of the weld bead 81 and the weld toe 82, the shortest distance D in the horizontal direction between the tip position of the consumable electrode 5 is preferably at most 35 mm, in 30mm or less there is further preferable.
　On the other hand, if the shortest distance D is 10mm or more, the shielding gas G1 arcing region of the welding torch 1, O of the oxidation-promoting gas G2 2 or CO 2 can be prevented that is mixed, therefore, an arc discharge forms the stabilized, Si, it is possible to suppress the increase of the Mn slag. Therefore, the shortest distance D is preferably at 10mm or more.
[0061]
(Flow rate of the oxidation promoting gas G2)
　as the flow rate of the oxidation-promoting gas G2, or 5L / min is preferably required for the progress of oxidation of the iron, and more preferably 7L / min or more. The flow rate of the oxidation-promoting gas G2 is not to disturb the shielding by shielding gas G1, it is preferably not more than the flow rate of the shielding gas G1.
[0062]
(Flow rate of oxidation promoting gas G2)
　gas flow rate at the nozzle outlet of the oxidation-promoting gas G2 is a 1 m / sec or more 3m / sec. The flow rate of oxidation-promoting gas G2 is the flow rate of the oxidation promoting gas G2 (L / min), a value prooxidant gas G2 is divided by the cross-sectional area of the site to be discharged out of the nozzle outlet.
　To promote the oxidation of the surface of the weld by oxidation-promoting gas G2 bead 81 and weld toe 82, the atmosphere of the surface of the weld bead 81 and weld toe 82 from the components of the shielding gas G1 of oxidation-promoting gas G2 it is necessary to replace the component.
[0063]
　At a flow rate of oxidation promoting gas G2 is 1 m / sec or less, be sufficiently replaced the atmosphere upper region shielding gas G1 atmosphere from oxidation promoting gas G2 of principal subject of the surface of the weld bead 81 weld toe 82 can not. On the other hand, the flow rate of the oxidation-promoting gas G2 exceeds the 3m / s, by the components of the oxidation promoting gas G2 is mixed into the shielding gas G1 arcing portion, excess Si, are Mn slag to produce the molten pool surface I fear there is. Further, the arc that shield according shielding gas G1 is disturbed becomes unstable, there is a fear that prevent the formation of weld beads.
　Accordingly, the flow rate of the oxidation-promoting gas G2 is set to 1 m / sec or more 3m / sec, more preferably from 1.5 m / sec or more 2.5 m / sec.
[0064]
　To ensure electrodeposition coating properties, it is preferred that the entire surface of the weld bead 81 surface of the weld toe 82 is covered only by the iron oxide slag conductivity.
　To weld bead 81 and the weld toe 82 is conductive, it is preferably covered by an iron oxide slag 9 in a thickness of more than 10μm from the surface. The thickness of the iron oxide slag is further preferably 15μm or more.
　On the other hand, if the weld bead 81 and the iron oxide slag excess thickness on the surface of the weld toe 82 is formed, there is a possibility that paint peeling occurs. Therefore, it is preferable that the thickness of the iron oxide slag is 50μm or less, and more preferably 40μm or less.
[0065]
　Arc welding method according to the present embodiment is applied to a well-known consumable electrode gas shielded arc welding (also called gas metal arc welding). Welding conditions are not particularly limited, normal conditions can be used.
　However, submerged arc welding, it does not belong to the present invention for a welding without using shielding gas. Further, since the submerged arc welding flux sprayed before welding is melted and solidified at the time of welding, thick slag of about 5 ~ 10 mm covers the weld bead. This is thick slag weld bead surface after removal of the, Si, Mn slag hardly exists, the weld bead surface is covered by the following thin iron oxide layer of about 5 [mu] m. That is, the present application to form an iron oxide 15 ~ 50 [mu] m to the weld bead and the toe portion surface oxidation-promoting gas, the form of the weld bead and toe section are different in submerged arc welding.
[0066]
　Welding, even overlapping welding, or may be a butt weld.
　Thickness and tensile strength of the steel sheet is not particularly limited, the thickness 1.6 ~ 3.2 mm, tensile strength 440 ~ 980 MPa are standard applied. It is also possible to use hot-dip galvanized steel sheet, galvannealed steel sheets, and aluminum-plated steel sheet.
[0067]
　But not limited to steel components and welding material components in particular, Si in the molten pool, to minimize the occurrence of Mn slag, respectively steel or welding material, Si content is less than 1 mass%, Mn it is desirable content is 2 mass% or less. It is also possible to weld the same kind steel plates, it may be welded heterogeneous steel plates.
[0068]
　While the present invention has been described in detail with reference to embodiments for, the above-described embodiment is merely illustrate concrete examples of implementing the present invention, the technical scope of the present invention is limited by these It should not be interpreted.
[0069]
　For example, in the above description, as an oxidation promoting gas blowing nozzle 22, FIG. 1A, FIG. 1B, although spraying prooxidant gas G2 with hood nozzle 22A as shown in FIG. 2, employs a variation of the following it may be.
[0070]
　As a first modification, FIG. 3A, as shown in FIG. 3B, 'directly from the after nozzles 22B which are connected, oxidation-promoting gas blowing means 20 for blowing oxidizing promoting gas G2' oxidation-promoting gas supply unit 21 adopts a it may be.
　In the oxidation-promoting gas blowing device 20 ', a rectangular after nozzle 22B in a plan view, it is arranged to move together with the welding torch 1 in the rear of the welding torch 1. Then, the after-nozzle 22B of supplying oxidizing promoting gas G2 from oxidation-promoting gas supply unit 21 'provided on the upper surface, a weld toe mainly weld bead 81 prooxidant gas G2 from the lower end of the after-nozzle 22B blown to the 82 surface of. Thus, it is possible to allow the oxidation of the iron is allowed to proceed to cover the weld bead 81 and weld toe 82 of a conductive iron oxide slag.
[0071]
　The shape of the after nozzle 22B is, 3A, may be of circular in plan view as in Figure 3B. After the nozzle 22B may be those downward is released, or may be a large number of gas blow holes on the bottom surface in a box shape is formed. Moreover, even those lower is released, may be one gas lens 10, such as a wire mesh in the vicinity of open end portions attached.
[0072]
　The second modified example, as oxidation promoting gas blowing device 20 '' may be a coaxial nozzle 22C as shown in FIG. The coaxial nozzle 22C is constructed by providing the outer peripheral wall is spaced outwardly from the outer circumferential surface of the welding torch 1. In this structure, oxidation-promoting gas G2 supplied from the oxidation-promoting gas supply unit 21 '' is blown through the space formed between the outer peripheral surface and the outer peripheral wall.
[0073]
(Example)
　For realization of the effect of the operability and the invention of the present invention based on the following examples will be described.
[0074]
　Components shown in Table 1, thickness, superimposed tensile steel sheet having a strength (A) between, or steel plates (B) ends of each other were lap fillet welded by gas shielded arc welding. At that time, using a solid wire (JIS Z3312, YGW16) having components and a diameter shown in Table 2, were Parusumagu welding. It shows a specific welding conditions shown in Table 3.
[0075]
[Table 1]

[0076]
[Table 2]

[0077]
[table 3]

[0078]
　Table 4 for each of Experimental Examples 1 to 19 show the evaluation results and the experimental conditions.
　Shielding gas G1 is, Ar, O 2 , CO 2 and adjusted the oxygen potential α by adjusting the amount of.
[0079]
　In Table 4, alpha represents the oxygen potential of the shielding gas G1 which is calculated by the above equation (1), beta indicates the oxygen potential of the oxidation promoting gas G2 which is calculated by the above equation (2). Gas flow rate of shielding gas G1 and oxidation-promoting gas G2 is a value prooxidant gas G2 is divided by the cross-sectional area of ​​the site to be discharged out of the nozzle outlet.
[0080]
　For the oxidation-promoting gas G2, which also shows the nozzle type, spray position, and gas flow rate.
　Nozzle type, Fig. 3A, Aft in the case of using the after-nozzle as shown in Figure 3B. Is denoted by N (After Nozzle), C. in the case of using a coaxial nozzle as shown in FIG. 4 It is indicated as N (Co-axial nozzle).
[0081]
　In the experimental examples using the after-nozzle, it was welded while supplying an oxidation promoting gas G2 in the same time after the nozzle when passing a shielding gas G1 from the welding torch.
　After nozzle, so that it can stop end surface of the weld bead (melt-solidified portion) is also covered with iron oxide, was 25mm width (with respect to the weld line).
　In this experimental example is about 50mm from the arc immediately below to the end how after the nozzle, the bead surface temperature at that location is about 700 ° C..
[0082]
　Welding torch, the cross-sectional shape of the passage of shielding gas G1 was used a circular inner diameter 16 mm (outer diameter 20 mm).
　The column of "blowing position" in Table 4 describes the portion oxidation promoting gas is blown out of the weld bead and weld toe, the shortest distance D in the horizontal direction between the tip position of consumable electrodes. Figure 3A, in the case of using the after-nozzle as shown in Figure 3B, the horizontal distance between the tip of the consumable electrode 5, and the outlet of the oxidation promoting gas G2 is discharged out of the oxidation promoting gas blowing device 20 ' , and the horizontal and outlet oxidation promoting gas G2 in the tip and oxidation promoting gas blowing device 20 of the consumable electrode 5 '' and is discharged in the case of using a coaxial nozzle of the double shield structure as shown in FIG. 4 it is a distance of direction.
　Gas flow rate is a flow rate at the nozzle tip.
[0083]
　As evaluation results,
(1) Si, adhesion area ratio of Mn slag
(2) conductive
(3) coating defects area ratio of
presence of (4) Iron oxide according sectional survey
are shown for Table 4. Explaining the evaluation method will be described below.
[0084]
(1) Si, adhesion area ratio of Mn slag
　the weld bead and the surface of the weld toe and photographed, from the image, the slag glassy brown Si. Regarded as Mn slag was measured the ratio of slag area to weld bead area.
[0085]
(2) conductive
　throughout resistance portions 10 between the weld bead and the slag surface of the weld toe steel, universal tester was measured conduction (POCKET TESTER MODEL CDM-03D) and addressed to. The If the resistance is infinity was determined by × and insulation. Bead surface covered with iron oxide showed a resistance of 40 ~ 1000 [Omega].
[0086]
(3) the area ratio of the coating defect
　weld specimens degreasing, after chemical conversion treatment was subjected to electrodeposition coating with a thickness of 20μm aim. As with the measurement of the slag area ratio, the weld bead coated part photographed, from the image, and measuring the ratio of the coating defect area with respect to the weld bead area.
[0087]
(4) cross-sectional study whether iron oxides by
　30% iron concentration over a cross section observation by EPMA, was ○ a case where iron oxide thickness of at least 10μm was confirmed.
[0088]
[Table 4]

[0089]
　In Inventive Example Experimental Example 1 belonging to 1-8, by which is blown to the weld bead with the surface of the weld toe in the appropriate conditions prooxidant gas G2, conductive iron oxides weld beads and weld toe It could be covered with slag. Therefore, Si in the weld bead and the outermost surface of the toe portion, the adhesion area ratio suppression of Mn slag, painting defects in the case of performing electrodeposition coating did not occur.
[0090]
　In Example 9, due to the oxygen potential β of the oxidation promoting gas G2 is excessive, conductive iron oxide slag is excessively formed on the surface of the weld bead and weld toe. For this reason, paint peeling occurs.
　In Example 10, due to the oxygen potential β of the oxidation promoting gas G2 is too small, the conductivity of the iron oxide slag is not sufficiently formed on the surface of the weld bead and weld toe. For this reason, coating failure has occurred.
[0091]
　In Example 11, the flow rate of the oxidation-promoting gas G2 is due to an excessive, shielding gas to a component of the oxidation-promoting gas G2 arcing portion had mixed. Therefore, Si is formed on the molten pool surface, since the Mn slag is excessively generated, later also as a proper range prooxidant gas G2, conductive iron oxide slag surface of the weld bead and weld toe It could not be covered with. For this reason, coating failure has occurred.
　In Example 12, the flow rate of the oxidation-promoting gas G2 is due to a too small, the atmosphere of the weld bead and weld toe of the surface could not be replaced with the oxidation-promoting gas G2. Therefore, it was not possible to sufficiently cover the surface of the weld bead and weld toe of a conductive iron oxide slag. For this reason, coating failure has occurred.
[0092]
　In Example 13, the oxygen potential α shielding gas G1 is due to an excessive, Si formed on the molten pool surface, since the Mn slag is excessively generated, the appropriate range prooxidant gas G2 after also, it was not possible to cover the surface of the weld bead and weld toe of a conductive iron oxide slag. For this reason, coating failure has occurred.
　In Example 14, due to the oxygen potential α shielding gas G1 is too small, arc welding state becomes unstable. For this reason, the bead formation failure has occurred.
　In Example 15, blowing position of the oxidation promoting gas G2 is, the consumable electrode due to the too far from 5, oxidation-promoting gas G2 at a position where the surface is less than 700 ° C. of the weld bead and weld toe is since the blown, it was not possible to cover the surface of the weld bead and weld toe of a conductive iron oxide slag. For this reason, coating failure has occurred.
[0093]
　In Experimental Example 16, due to using no oxidation-promoting gas G2, it could not cover the surface of the weld bead and weld toe of a conductive iron oxide slag. For this reason, coating failure has occurred.
　Experimental Examples 17 and Experiment Example 18, similarly as in Experimental Example 16, although an experimental example using no oxidation promoting gas G2, assuming the conditions of Patent Document 1, a shielding gas G1 Ar = 97%, O 2 = 3%, or, Ar = 88% CO 2 has a = 12%. Again in these examples, shielding gas components remaining on the surface of the weld bead and weld toe immediately after welding due to that have not been replaced by the oxidation promoting gas G2, the surface of the weld bead and weld toe it can not be covered with the electrically conductive certain iron oxide conductivity is iron oxide. For this reason, coating failure has occurred.
[0094]
　In Example 19, Patent Document 2, assuming the conditions of Experimental Example 3, the oxygen potential α shielding gas G1 and 0.0%, the oxygen potential β of the oxidation promoting gas G2 supplied from the coaxial nozzle 10.0% and the.
　In this experimental example, due to the oxygen potential α shielding gas G1 is too small, arc welding state becomes unstable, bead formation failure occurred. Furthermore, due to the oxygen potential β of the oxidation promoting gas G2 is too small, not conducting iron oxide slag is sufficiently formed on the surface of the weld bead and weld toe, painting failure occurred.
[0095]
　Figure 5 is a comparative example not using the oxidation-promoting gas (Experimental Example 16), comparative example in which 10.0% of oxygen potential β of the oxidation promoting gas G2 (Experimental Example 19), and, the oxygen potential of the oxidation-promoting gas G2 for an invention example in which the β and 15.0% (experiment 2) is a photograph showing post-weld appearance, after painting appearance, and corrosion after appearance.
　As shown in FIG. 5, can form a conductive iron oxide slag on the surface of the weld bead and weld toe by using a suitable oxidation-promoting gas G1, it can be avoided painting failure, further, advanced oxidation the higher effect by increasing the oxygen potential β of the gas G2 is obtained was confirmed.
[0096]
　Incidentally, FIG. 6 shows an example comparison and 10.0% oxygen potential β of the oxidation promoting gas G2 (Experimental Example 19), Si, a state in which a part of Mn slag is substituted with Fe-based oxide appearance shows a photograph (left) and SEM photograph. As shown in FIG. 6, when the Si oxide and Mn oxide by using the oxidation-promoting gas G2 but it is possible to replace the Fe oxide, the oxidation-promoting gas G2 oxygen potential β is low remain in Si oxide and Mn oxide surface, paint defects seen to cause to occur.
[0097]
　Further examples comparisons oxygen potential β of the oxidation promoting gas G2 and 10.0% (Experimental Example 19), and, for an invention example where the oxygen potential β of the oxidation promoting gas G2 and 15.0% (Example 2) the weld bead before welding after electrodeposition coating along a line perpendicular to the weld line, embedded in a resin, after polishing, were carried out element mapping with EPMA (Fe, C, O, Si, Mn) and. As a result, the Si, Mn slag observation of Comparative Example (Experimental Example 19), while the Fe concentration was approximately as low as 3-7%, the Fe-based oxide observations of the inventive example (Example 2) Fe concentration is increasing to 40 to 70%, it was confirmed that the thickness was also Buatsuka' and 30 [mu] m. Also in the weld bead surface in Comparative Example (Experimental Examples 19), Si, although the oxide film of iron on Mn slag generated outside the region of the bead surface is formed, is thin as about 5μm thickness, invention examples (experiments example 2) the iron oxide was confirmed that generation form is different.
[0098]
　Figure 7 is a schematic diagram illustrating the effect of the inventive example compared to the techniques of Patent Documents 1-3. As shown in this figure, as in the technique of Patent Documents 1 to 3, in gas-shielded arc welding is not performed blowing of oxidation-promoting gas G2, the weld bead and weld toe of the high temperature state is in contact with the shielding gas G1 because the state can not be on the surface of the weld bead and weld toe covering a conductive iron oxide slag.
　On the other hand, according to the present invention example, the blown at a flow rate of more than 1 m / sec relative to the weld bead and weld toe of a high temperature state of the oxidation-promoting gas G2 at least 700 ° C., flow into on the weld bead from the welding torch shielding gas G1 to the other is eliminated. Thus, the weld bead and weld toe of the high temperature state is a state of contact with the oxidation-promoting gas G2. The oxidation-promoting gas G2, the oxygen potential β is increased to 15% or more, the welding oxidation reaction of beads and weld toe of the surface is promoted, the conductivity of the iron oxide slag be sufficiently formed it can. Therefore, the effect of preventing coating defects can be obtained. Furthermore, food nozzles, after the nozzle, in the case of blowing oxidizing promoting gas G2 using a coaxial nozzle, it is possible to collect the oxidation-promoting gas G2 in necessary portions, it is possible to enhance the effect.
Industrial Applicability
[0099]
　According to the present invention, it is possible to provide Si, weld electrodeposition coating defect portion due to Mn slag does not occur, and the consumable-electrode gas-shield arc welding method welding portion can be formed.
DESCRIPTION OF SYMBOLS
[0100]
　1 welding torch
　5 consumable electrode
　6 arc
　8 molten pool
　81 weld bead
　82 weld toe
　9 conductive iron oxide slag
　10 gas lens
　11 weld lines
　20, 20 ', 20' 'oxidation-promoting gas blowing means
　21, 21' , 21 '' oxidation-promoting gas supply unit
　22 oxidation-promoting gas blowing nozzles
　22A hood nozzle
　22B After the nozzle
　22C coaxial nozzle
　30 torch through holes
　G1 shielding gas
　G2 oxidation-promoting gas

The scope of the claims
[Requested item 1]
The two sheets of steel plates with a welding torch having a consumable electrode and a consumable electrode gas-shield arc welding method for arc welding,
an oxygen potential α is 1.5% to 5% represented by the following formula (1) the shielding gas, the welding while supplying toward the consumable electrode from the torch performs arc welding,
to a welding bead which is in the state of 700 ° C. or higher, which is formed by the arc welding with weld toe, the following (2 ) oxygen potential β is the oxidation promoting gas is 15% to 50% blowing at a flow rate of 1 ~ 3m / sec of formula
consumable-electrode gas-shield arc welding method, characterized in that.
alpha = 100 × ([V 1 (O 2 )] + [V 1 (CO 2 )] / 5) / ([V 1 (X)] + [V 1 (O 2 )] + [V 1 (CO 2 )]) (1) beta = 100 × [V 2 (O 2 )] / ([V 2 (X)] + [V
2 (O 2 )] + [V 2 (CO 2 )]) · · · (2) equation
,
where, [V 1 by (X)] is the mixing ratio of the inert gas contained in the shielding gas (vol%)
There, [V 1 (O 2 a)] is the mixing ratio of oxygen contained in the shielding gas
(vol%), [V 1 (CO 2 )] is the mixing ratio of the carbon dioxide contained in the shielding gas (vol%) and
a, [V 2 (X)] is the mixing ratio of the inert gas used in the oxidation promoting gas
(vol%), [V 2 (O 2 )] is the mixing ratio of oxygen contained in the oxidation-promoting gas ( is the
volume%), [V 2 (CO 2 )] is the mixing ratio of the carbon dioxide contained in oxidation-promoting gas (vol%).
[Requested item 2]
　The oxidation-promoting gas, said welding torch is blown through the space formed between the outer peripheral wall which is spaced apart outwardly from the outer peripheral surface
depletion of claim 1, characterized in that electrode gas-shield arc welding method.
[Requested item 3]
　The oxidation-promoting gas, with at least a portion of the upper region of the weld bead and weld toe is surrounded in the state of more than 700 ° C., it is blown into the upper region
claim 1, characterized in that or 2 consumable electrode gas-shield arc welding method according to.
[Requested item 4]
　The weld bead and said portion oxidation promoting gas is blown out of the weld toe, the horizontal direction of the shortest distance between the tip position of consumable electrodes is less than 35mm
of claims 1 to 3, characterized in that consumable-electrode gas-shield arc welding method according to any one of.
[Requested item 5]
　A arc welding unit formed by the consumable-electrode gas-shield arc welding method according to any one of claims 1 to 4,
　the surface of the weld bead, and the surface of the weld toe of the weld bead , the arc welding unit, characterized in that is covered with a conductive iron oxide slag containing one or both of magnetite and wustite.
[Requested item 6]
　The thickness of the conductive iron oxide slag is 10 [mu] m ~ 50 [mu] m
arc welding unit according to claim 5, characterized in that.
[Requested item 7]
　The surface of the weld bead, and the entire surface of the weld toe of the weld bead is covered with the conductive iron oxide slag
arc welding unit according to claim 5 or 6, characterized in that .