JP2010131637A - Gas shielded arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas shielded arc welding method for increasing work efficiency of an entire welding process by preventing delayed crack and lowering preheating temperature. <P>SOLUTION: Gas shielded arc welding is performed to a steel plate 500 having a tensile strength of ≥570 N/mm<SP>2</SP>or a cracking parameter P<SB>CM</SB>of ≥0.24% and a thickness of ≥16 mm. A contact tip 100 has a conductive power supply part 110 installed on the base end side and a guide part 120 which is installed on the tip end side and non-conductive and which guides a launching wire. The guide part 120 is installed in an area of 5-70 mm from the tip end of the contact tip 100. A wire projection length L is ≤30 mm and a welding wire 300 has an electric resistance of ≥80 μΩ per 1 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas shielded arc welding method, and more particularly, to a gas shielded arc welding method for reducing the preheating temperature and speeding up the welding process.

It is delayed cracking (also referred to as hydrogen cracking or cold cracking) that the volume is expanded by the accumulation of diffusible hydrogen in the weld metal or the base metal and the pressure from the volume expansion leads to cracking.
The factors affecting the delayed cracking, the thickness, the amount of diffusible hydrogen, and the weld metal or base metal heat affected zone (H eat A ffected Z one, HAZ) hardness, are three like. When these three factors increase, delayed cracking occurs.

  Patent Document 1 describes that rare earth metal or Ca is added to a steel material in order to prevent delayed cracking, but when these metals are added to a welding material, welding workability is increased due to an increase in spatter and the like. Gets worse.

  In order to prevent delayed cracking, (a) a welding material with a small amount of diffusible hydrogen is used, (b) a composition in which the steel material or the weld metal is hard to harden, and (c) an appropriate amount to be hard to harden. There are methods of controlling heat input and interpass temperature, and (d) performing appropriate preheating and postheating to release diffusible hydrogen.

  In particular, preheating is an effective means for welding high-strength steel with high hardness. For example, WES-3001 and JIS Z3118 show the relationship between the chemical composition of the steel material that affects the plate thickness, the amount of diffusible hydrogen, and the hardness, and the crack prevention preheating temperature.

  With the recent demands for reducing the weight of steel materials and improving the work efficiency by reducing the plate thickness, while steel materials are becoming higher in tension, there is also a limit to reducing the hydrogen content of welding materials, so preheating temperature is a measure to prevent cracking. May have to be raised. However, when the preheating temperature is increased, time is required for the pre-welding process, and the work efficiency of the entire welding process is reduced.

  On the other hand, the flux-cored wire has the characteristics that the arc is stable, the spatter is small, and the bead appearance is beautiful. Likely to happen.

  In order to prevent the occurrence of delayed cracking and to use a flux-cored wire, the preheating temperature must be increased. However, if the preheating temperature is increased as described above, the work efficiency of the entire welding process is lowered.

  Patent Document 2 discloses an arc welding method for lowering the preheating temperature when welding high-strength steel, but the effect of lowering the preheating temperature is still insufficient.

Japanese Patent Publication No. 6-77837 JP 07-323392 A

  As described above, a gas shielded arc welding method having a low preheating temperature, hardly causing delayed cracking, and having good welding workability has not yet been developed, and its realization is desired.

  The present invention has been made in view of such problems, and provides a gas shielded arc welding method capable of preventing delayed cracking and reducing the preheating temperature to improve the working efficiency of the entire welding process. Objective.

The gas shielded arc welding method according to the first aspect of the present invention includes:
A tensile strength of 570N / mm ² or more, or weld crack sensitivity index _{P CM} is 0.24% or more, the welding wire and steel plate thickness is more than 16mm A method of gas shielded arc welding, fed In the gas shielded arc welding method in which the welding wire is fed while being passed through the contact tip in the longitudinal direction and is guided toward the wire aiming position of the weld portion, the contact tip has its proximal end portion The portion provided on the side and contacting the welding wire has a conductive power supply portion, and the portion provided on the tip side of the contact tip and contacting the welding wire is non-conductive and has a guide portion for guiding the delivery wire. The guide portion is provided in a range of 5 to 70 mm from the tip of the contact tip, and an arc generation point from the tip of the contact tip. Wire extension length in is at 30mm or less, the welding wire is characterized in that the electrical resistance per 1mm is iron alloy solid wire or an iron alloy skin flux cored wire is more 80Myuomega.

  In this case, the power feeding part of the contact chip is constituted by a conductive first member, the guide part is constituted by a non-conductive second member, and the second member is a wire of the first member. It is preferable that it is connected to the front end side in the feeding direction by a screw.

  The power supply part of the contact chip is formed of a conductive first member, and the second member is coupled to the front end side of the wire feeding direction of the first member with a screw. The guide part of the contact chip Can also be provided locally at the portion of the second member that contacts the welding wire.

Moreover, the gas shielded arc welding method according to the second aspect of the present invention includes:
A tensile strength of 570N / mm ² or more, or weld crack sensitivity index _{P CM} is 0.24% or more, the welding wire and steel plate thickness is more than 16mm A method of gas shielded arc welding, fed In the gas shielded arc welding method in which the welding wire is fed while passing through the contact tip in the longitudinal direction, a guide hole through which the welding wire is inserted is provided in front of the contact tip in the wire feeding direction. A wire guide member that guides the welding portion toward the wire target position of the welded portion, the distance between the tip of the contact tip and the guide hole is 5 to 70 mm, and the distance from the guide hole to the arc generation point An iron alloy solid wire having a wire protrusion length of 30 mm or less and the welding wire having an electric resistance of 80 μΩ or more per 1 mm. Or wherein the iron alloy outer skin flux-cored wire.

  In this case, it is preferable that the wire guide member has a rod-shaped member provided at a tip portion of a shield nozzle that externally fits the contact chip, and the guide hole is formed in a central portion of the rod-shaped member. .

  The wire guide member may include a lead member provided in front of the tip portion of the contact chip, and the guide hole may be formed in a central portion of the lead member.

  Moreover, it is preferable that 0.30 g or more of lubricating oil is applied to the surface of the welding wire per 10 kg of the wire.

  Furthermore, it is preferable that the welding wire is not subjected to copper plating on its surface, or is subjected to annealing oxidation without applying copper plating to the surface.

  In the gas shielded arc welding method according to the present invention, even if the hydrogen content of the welding wire is high, the hydrogen contained in the welding wire is vaporized before the formation of droplets and is removed from the arc range by riding on the seal gas flow. Therefore, delayed cracking due to diffusible hydrogen in the weld metal hardly occurs, and the preheating temperature in the welding process can be lowered. Accordingly, the work efficiency of the entire welding process is increased. In addition, since it is difficult to cause delayed cracking due to the lubricant applied to the surface of the welding wire or the moisture absorbed by the flux, various types of lubricants can be used while preventing a reduction in work efficiency due to the preheating process. In addition, a flux can be used, and the degree of freedom in selecting a welding material is increased. Thereby, while having the outstanding workability | operativity, the welding material suitable for high strength steel can be obtained.

(First embodiment)
First, the gas shield arc welding method according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a gas shielded arc welding method according to the first embodiment, in which (A) is a schematic view from the tip direction of a contact tip, and (B) is A in FIG. 1 (A). FIG.

  As shown in FIG. 1 (B), the contact tip 100 is provided on the base end side thereof, and a portion contacting the welding wire 300 is provided on the conductive power supply portion 110 and the tip end side of the contact tip 100 and welded. The portion that contacts the wire 300 is non-conductive and has a guide portion 120 that guides the delivery wire. In addition, all the guide parts 120 of this embodiment are shape | molded with the insulating material. The guide part 120 is provided in a range from 5 to 70 mm from the tip of the contact chip 100. That is, the length ΔX of the guide part 120 is 5 mm or more and 70 mm or less.

  The guide part 120 is made of an insulating material such as ceramic. The guide part 120 is coupled to the front end side of the power feeding part 110 in the wire feeding direction by a screw. That is, a male screw is formed in the power feeding part 110, and a female screw is formed in the guide part 120. By screwing the male screw into the female screw, the power feeding part 110, the guide part 120, Are connected. According to this structure, the whole guide part 120 can be attached or detached easily. The power feeding unit 110 and the steel plate 500 are energized from the welding machine 600.

  When gas shielded arc welding is performed using the apparatus configured as described above, the welding wire 300 is fed toward the contact tip 100 at a predetermined speed, and the welding wire 300 is moved in the longitudinal direction of the contact tip 100. The sheet is inserted through the hole in the center and sent toward the steel plate 500. And the arc 400 is induced between the welding wire 300 and the steel plate 500, and the welding part of the steel plate 500 is welded.

  Next, the reason why the contact chip 100 is constituted by the power feeding part 110 and the guide part 120 and the length ΔX of the guide part is set to 5 mm or more and 70 mm or less will be described.

As shown in the following formula 1, the melting rate in arc welding is the heat generated at the electrode of the arc (C ₁ term) and the resistance heating at the protruding part of the contact tip (C ₂ term), where the welding speed is MR. Depends on and. The present inventor has found that by increasing the resistance heating in the projecting portion of the contact tip of the (C ₂ term), hydrogen contained in the welding wire is vaporized prior to droplet formation, outside arc range riding seal gas flow It was found that the amount of diffusible hydrogen in the weld metal can be greatly reduced. In Equation 1, the C ₁ term is represented by the product of the constant K ₁ and the current I, and the C ₂ term is represented by the constant K ₂ , the current I, the electrical resistance ρ, and the wire protrusion length L.

Based on this finding, the guide portion 120 attached to a lower portion of the feeding portion 110, and the wire protruding substantially to extend the length with greatly heat generation in the C ₂ term, to stabilize the target position of the welding wire 300 Yes. That is, welding in order to improve the accuracy of the target position of the wire 300, the amount of hydrogen it is desirable to shorten the length L and the wire protruding, but So the amount of heat generated by the C ₂ term that by increasing the process proceeds to weld It is difficult to lower the value. Therefore, the guide portion 120 provided below the feeding section 110, the amount of heat generated by the C ₂ term in conjunction with stabilizing the target position of the welding wire causes large. Here, when the length ΔX of the guide portion 120 is 5 mm or more, the effect of reducing the amount of hydrogen becomes remarkable, and the effect of reducing the preheating temperature is great. However, if ΔX is less than 5 mm, the amount of hydrogen is not sufficiently lowered and the effect of lowering the preheating temperature is insufficient. Therefore, ΔX is 5 mm or more, more preferably ΔX is 10 mm or more. On the other hand, when ΔX exceeds 70 mm, it is difficult to maintain a stable arc length, and the arc becomes unstable. Moreover, arc start property deteriorates. Therefore, ΔX is 70 mm or less. FIG. 2 shows the relationship between ΔX, the amount of diffusible hydrogen in the weld metal, and the preheating temperature drop.

Steel 500, the tensile strength is not more 570N / mm ² or more, or weld crack sensitivity index _{P CM} 0.24% or more, the thickness is not less than 16 mm.

The reason why the tensile strength of the steel plate 500 is set to 570 N / mm ² or more is that, by setting the tensile strength in this way, it is effective to lower the preheating temperature for preventing cracking. In addition, Preferably, the tensile strength of the steel plate 500 is 650 N / mm ² or more.

Also, the tensile strength of the steel sheet 500 is not more 570N / mm ² or less, if the weld cracking susceptibility _{P CM} as high C steel 0.24% or more, the higher the susceptibility to cracking of the steel sheet 500, cracking The preheating temperature reduction for prevention becomes effective. Here, P _CM (%) = C + Si / 30 + Mn / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5B. The reason why the _PCM parameter is provided only in the steel plate 500 is that the relationship between the component and the tensile strength of the steel plate 500 is not constant due to the cooling rate control process at the time of manufacture. Incidentally, preferably, the welding crack sensitivity index _{P CM} is 0.30% or more.

On the other hand, 570N / mm ² less than the tensile strength, and is low originally preheating temperature in the steel sheet of less than P _CM 0.24%, or for substantially preheating is not required, use a welding method according to this embodiment There is little profit to do. Further, 570N / mm ² less than the tensile strength, _and the steel sheet of less than 500 P CM 0.24%, there is a case of using the economically disadvantageous welding method according to this embodiment.

  Next, the reason why the thickness of the steel plate 500 is set to 16 mm or more is that the larger the plate thickness, the faster the cooling rate of the welded portion and the easier it is to cause delayed cracking because it hardens, so preheating by the welding method according to this embodiment. This is because the temperature lowering effect becomes remarkable. On the contrary, if the plate thickness of the steel plate 500 is less than 16 mm, the preheating temperature is low in the first place or substantially no preheating is required, and therefore there are few benefits of using the welding method according to this embodiment. In addition, using the welding method according to the present embodiment may be disadvantageous in terms of cost.

The welding wire 300 is an iron alloy solid wire or an iron alloy outer flux cored wire having an electric resistance per mm of 80 μΩ or more, and obtains a weld metal having a tensile strength of 570 N / mm ² or more. Further, the wire protrusion length L from the tip of the contact tip 100 to the generation point of the arc 400 is 30 mm or less.

  The higher the electric resistance of the welding wire 300, the more effectively the resistance heat is generated, the hydrogen contained in the welding wire 300 is vaporized, and the transition to the weld metal can be prevented, so the electric resistance of the welding wire 300 is 80 μΩ / mm. That's it. The electrical resistance (Ω / mm) is a value obtained by dividing the resistance value (Ω) measured by the four-terminal method by the distance between measurements (mm).

  The welding wire 300 is preferably an iron alloy solid wire. This is because an iron alloy outer flux cored wire has a small effective sectional area due to its tube structure, but generally has very few components such as C, Si, and Mn in the outer sheath (hoop) and has a low electric resistance. In exceptional cases, an iron alloy skin flux-cored wire in which a large amount of components are contained in the iron alloy skin has a higher electrical resistance than an iron alloy solid wire, and can be suitably used. Moreover, when using an iron alloy outer shell flux cored wire, since the electrical resistance becomes high when the ratio (flux rate) of the flux area in the cross-sectional area is large, it can be suitably used.

  The wire diameter of the welding wire 300 is preferably smaller. This is because if the wire diameter is small, the cross-sectional area is small and the electrical resistance becomes high.

  In the welding wire 300, the composition of the iron alloy solid wire or the iron alloy outer sheath is such that elements such as C, Si, Mn, Cr, Mo, Ni, Ti, Nb, V, Co, W, Al, and N are added to iron. It is preferred that This is because the electrical resistance increases when these elements are added.

The reason why the weld metal having a tensile strength of the welding wire 300 of 570 N / mm ² or more is obtained is that delayed cracking occurs not only in the heat-affected zone of the steel plate 500 but also in the weld metal. This is because it is necessary to limit the lower limit. The strength of the weld metal is preferably 650 N / mm ² or more.

  The reason why the wire protrusion length L is limited to 30 mm or less is that as the wire protrusion length L is longer, the hydrogen contained in the welding wire 300 is vaporized before the droplet formation and escapes out of the arc range. This is because the longer the length L, the greater the target misalignment and the more difficult the stable welding becomes. Therefore, the wire protrusion length L is suppressed to 30 mm or less in order to reduce the target misalignment and obtain a low hydrogenation effect.

  The welding wire 300 is coated with a lubricating oil such as vegetable oil, animal system, or mineral. This is because the friction resistance of the welding wire 300 is lowered to improve the wire feeding property and to improve the wire rust prevention property. The method of applying the lubricating oil to the welding wire 300 is a means for transferring the oil uniformly by sandwiching the wire between fibers dripped and immersed in the oil, a means for causing the oil to be atomized and ionized, and to adhere to the wire electrically, or Means for spraying atomized oil can be used.

  Lubricating oil is applied in an amount of 0.30 g or more per 10 kg of wire. In the welding method according to the present embodiment, hydrogen contained in the welding wire 300 is vaporized before droplet formation and the amount of diffusible hydrogen in the weld metal can be reduced. This is because an appropriate amount of lubricating oil can be applied. The upper limit of the lubricant application amount is not particularly limited, but if it is applied to 2.00 g / 10 kg or more, the feed roller may slip due to an excessive friction coefficient, which may cause a feed failure. .

It is desirable that the surface of the welding wire 300 is not subjected to copper plating. The reason for this will be described below. That is, the melting speed MR in Equation 1 described above is mainly a (C ₁ paragraph) has been described to depend on the resistance heating in the projecting portion of the contact tip and (C ₂ term), as shown in FIG. 3 Further, it also depends on the “electric resistance of the contact portion between the chip and the wire” as the C ₃ term proportional to the current. The factors affecting the C ₃ Section include the presence or absence of copper plating and surface oxidation. The electric resistance of the contact portion is higher when there is no copper plating applied to the welding wire for the purpose of ensuring electric conductivity, wire drawing or rust resistance. Therefore, it is preferable that the welding wire 300 is not plated with copper. Furthermore, the surface of the welding wire 300 has an oxide layer formed by annealing oxidation (baking), so that the electrical resistance of the contact portion is increased. Therefore, the welding wire 300 is preferably subjected to an annealing oxidation treatment.

(Second Embodiment)
FIG. 4 is a schematic view for explaining a gas shielded arc welding method according to the second embodiment of the present invention, in which (A) is a schematic view from the tip direction of a contact tip, and (B) is a schematic view of FIG. It is an AA 'line sectional view in). As shown in FIGS. 4A and 4B, the power feeding unit 110 includes a conductive first member 111 and a second member 112, and the second member 112 is a wire of the first member 111. It is connected to the front end side in the feeding direction with screws. The guide portion 120 is locally provided at a portion that contacts the welding wire 300 in the center portion of the second member 112. Others are the same as in the first embodiment.

  According to the configuration of the second embodiment, since the guide portion 120, which is an insulating material that tends to be expensive, is locally formed, the entire contact chip 100 can be formed at low cost. Further, since the first member 111 and the second member 112 can be formed of the same conductive material, the strength of the joint portion by the male screw and the female screw can be increased.

(Third embodiment)
FIG. 5 is a schematic diagram for explaining a gas shielded arc welding method according to a third embodiment of the present invention, in which (A) is a schematic diagram from the tip direction of a contact tip, and (B) is a schematic diagram of FIG. It is an AA 'line sectional view in A). As shown in FIGS. 5A and 5B, a rod-shaped member 210 is provided on the lower end surface of the long shield nozzle 200, and a guide hole 150 is formed at the center of the rod-shaped member 210. The position ΔX of the guide hole 150, that is, the distance ΔX from the distal end portion of the guide hole 150 to the distal end portion of the contact chip 100 is 5 mm or more and 70 mm or less.

The reason why the welding wire 300 protruding from the tip end of the contact tip 100 is inserted into the guide hole 150 is that the wire protruding length L is substantially extended, and the reason is that C is the same as the reason described in the first and second embodiments. _{This is} to increase heat generation in the _second term and stabilize the target position of the welding wire 300.

  The reason why ΔX is 5 mm or more and 70 mm or less is the same as the reason explained in the first and second embodiments. If ΔX is less than 5 mm, the amount of hydrogen is not sufficiently lowered and the effect of lowering the preheating temperature is insufficient. This is because if ΔX exceeds 70 mm, it is difficult to maintain a stable arc length and the arc becomes unstable. More preferably, ΔX is not less than 10 mm and not more than 70 mm.

(Fourth embodiment)
FIG. 6 is a schematic diagram for explaining a gas shielded arc welding method according to a fourth embodiment of the present invention, in which (A) is a schematic diagram from the tip direction of a contact tip, and (B) is a schematic diagram of FIG. It is an AA 'line sectional view in A). In the third embodiment, the guide hole 150 is formed at the center of the rod-shaped member 210 provided on the lower end surface of the shield nozzle 200. However, in the fourth embodiment, the guide hole 150 is spaced apart from the tip of the contact chip 100. A difference is that a letter-shaped lead member 220 is provided, and a guide hole 150 is formed at the center of the lead member 220. According to this configuration, even if the guide hole 150 is damaged, it is only necessary to replace the lead member 220 without changing the contact chip 100. Others are the same as in the third embodiment.

  Hereinafter, the results of tests conducted to verify the effects of the present invention will be described. JIS Z3158 “diagonal Y-type weld cracking test” was conducted as a means for confirming the minimum preheating temperature capable of preventing cold cracking. Table 1 below shows the components and tensile strength of the steel plates used. Table 2 below shows the wire type, flux rate, wire component, and presence / absence of plating in Examples (No. 1 to No. 32). Table 3 below shows the wire type, flux rate, wire component, and presence / absence of plating in comparative examples (No. 33 to No. 44) outside the scope of the present invention. In addition, No. No. 23 contained W: 1.7 mass%, Co: 1.6 mass%, and N: 0.04 mass% as other components in the wire component. Example No. Reference numeral 31 is a baking wire subjected to a baking treatment.

  In Table 4 below, the amount of feed lubricating oil adhering to the surface in Examples (No. 1 to No. 32), the amount of diffusible hydrogen of weld metal, electrical resistance measurement, applicable shield gas composition, steel plate, plate thickness, An embodiment in which ΔX is a predetermined length, ΔX length, metal strength of the welding wire, preheating temperature decrease, arc stability, wire aiming position stability, and wire feeding stability are shown. In Table 5 below, the amount of feed lubricating oil adhering to the surface in Comparative Examples (No. 33 to No. 44), the amount of diffusible hydrogen of weld metal, electrical resistance measurement, applicable shield gas composition, steel plate, plate thickness, Embodiment of contact tip, ΔX length, metal strength of welding wire, preheating temperature decrease, arc stability, wire aiming position stability, wire feeding stability are shown.

  The chemical component in the flux-cored wire is a value obtained by converting the outer skin and the flux composition. All flux-cored wire hoops are made of 0.01% C-0.01% Si-0.22% Mn-0.010% P-0.005% S-balance iron and inevitable impurities A 0.9 mm thick steel strip was used. Separately from the “diagonal Y-type weld cracking test”, the weld metal has a tensile strength of 35 ° V groove under the same conditions of the steel plate and plate thickness, shield gas, and the conditions of the present embodiment 1, 2 or 3. It is the result of collecting a JIS Z3111 A1 tensile test piece from the center of the weld metal part when multi-ply welding with a gap of 8 mm and backing metal, and performing a tensile test. The amount of diffusible hydrogen in the weld metal was measured according to the gas chromatographic method of JIS 3118 “Method for measuring hydrogen content in steel welds” using a normal welding tip and a shield nozzle.

In the test, the preheating temperature was changed by 25 ° C., and the lowest value of the preheating temperature at which cracking did not occur, that is, the crack stop time value temperature was determined. The difference between the crack stop preheating temperature Temp ^N when using a normal welding tip and a shield nozzle and the crack stop preheating temperature Temp ^{A under} each condition, ΔTemp (= Temp ^N −Temp ^A ) is obtained, and ΔTemp is 25 ° C. or more. Then, it was judged that there was an improvement effect. However, when ΔTemp was less than 25 ° C., that is, when it was not different from the normal welding method, there was no improvement effect.

  In addition, regarding arc stability, wire aiming position stability, and wire feed stability, all were good, ◯ when slightly inferior, and x when poor and unusable.

In Examples (No. 1 to No. 32), an effect of reducing the amount of diffusible hydrogen in the weld metal is obtained as compared with the case of using a normal contact tip or a welding torch system, and thus an effect of reducing the preheating temperature. Was demonstrated. Further, in the examples, arc stability, wire aiming position stability, and wire feed stability were all good. In addition, Example No. No. 32 was a little unstable because only the wire feedability was low because the amount of oil applied to the supply lubricant was small as a high strength steel welding wire. Therefore, Example No. 1-No. Even if a supply lubricant equivalent to that of a mild steel wire is applied as in 31, the welding method according to the present invention is not affected by this and suppresses the amount of diffusible hydrogen in the weld metal and improves the feedability. It was confirmed that the effect of lowering the preheating temperature can be obtained while maintaining it.

  On the other hand, about a comparative example (No. 33-No. 44), for example, comparative example No. Since the strength of the steel plate to be applied was low, the sensitivity to delayed cracking was low, and the effect of lowering the preheating temperature was insufficient. Comparative Example No. Since the strength of the steel plate to which No. 34 is applied is low and the strength of the weld metal is also low, the delayed cracking sensitivity is originally low and the effect of lowering the preheating temperature is insufficient. Comparative Example No. 35-No. No. 37 has a low electrical resistance of the welding wire due to its chemical composition or wire diameter, so the effect of removing hydrogen due to heat generation is low, and the effect of lowering the preheating temperature is insufficient. Comparative Example No. Although No. 38 has high strength in both the steel plate and the weld metal, since the plate thickness is thin, the delayed cracking susceptibility was originally low, so that the effect of lowering the preheating temperature was insufficient. Comparative Example No. 39-No. Since ΔX of 40 was too small, the effect of removing hydrogen due to heat generation was low, and the effect of lowering the preheating temperature was insufficient. Comparative Example No. 41-No. On the other hand, in No. 43, since ΔX was excessive, the welding wire generated a large amount of heat, and it was in a semi-molten state before the arc generation point, and the arc was unstable and unstable. Comparative Example No. No. 44 is a conventional welding torch system that attempts to obtain a heat generation effect of the welding wire by increasing the protruding length. However, since the distance from the tip of the contact tip is long, the deviation of the wire target position is severe, and the bead Meandered.

It is a figure explaining the welding method which concerns on 1st Embodiment with which the guide part is couple | bonded with the electric power feeding part with the screw | thread, (A) is an external view from the downward direction, (B) is sectional drawing in an AA 'line | wire. It is. It is a graph which shows the relationship between (DELTA) X, the amount of diffusible hydrogen of a weld metal, and a preheating temperature fall width. It is a figure explaining the C ₁ term, C ₂ term, and C ₃ term which affect the melting rate MR. It is a figure explaining the welding method which concerns on 2nd Embodiment by which the 2nd member containing a cylindrical guide part is couple | bonded with the 1st member of the electric power feeding part with the screw | thread, (A) is an external view from the bottom, (B) is sectional drawing in the AA 'line. It is a figure explaining the welding method which concerns on 3rd Embodiment by which the guide hole is formed in the center of the rod-shaped member located in the lower end surface of a long shield nozzle, (A) is an external view from the bottom, (B ) Is a cross-sectional view taken along the line AA ′. It is a figure explaining the welding method which concerns on 4th Embodiment by which the guide hole is formed in the lower surface center of a U-shaped lead member, (A) is an external view from the downward direction, (B) is AA. It is sectional drawing in a line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Contact tip 110 Electric power feeding part 120 Guide part 150 Guide hole 200 Shield nozzle 300 Welding wire 400 Arc 500 Steel plate

Claims (8)

A tensile strength of 570N / mm ² or more, or weld crack sensitivity index _{P CM} is 0.24% or more, the welding wire and steel plate thickness is more than 16mm A method of gas shielded arc welding, fed In the gas shielded arc welding method in which the welding wire is fed while being passed through the contact tip in the longitudinal direction and is guided toward the wire aiming position of the weld portion, the contact tip has its proximal end portion The portion provided on the side and contacting the welding wire has a conductive power supply portion, and the portion provided on the tip side of the contact tip and contacting the welding wire is non-conductive and has a guide portion for guiding the delivery wire. The guide portion is provided in a range of 5 to 70 mm from the tip of the contact tip, and an arc generation point from the tip of the contact tip. And the wire protruding length 30mm In the following, the welding wire gas shielded arc welding wherein the electrical resistance per 1mm is iron alloy solid wire or an iron alloy skin flux cored wire is more 80Myuomega. The power supply part of the contact chip is constituted by a conductive first member, the guide part is constituted by a non-conductive second member, and the second member is a tip of the first member in the wire feeding direction. The gas shielded arc welding method according to claim 1, wherein the gas shielded arc welding method is coupled to the side by screws. The power supply portion of the contact chip is formed of a conductive first member, the second member is coupled to the front end side of the wire feeding direction of the first member by a screw, and the guide portion of the contact chip is The gas shielded arc welding method according to claim 1, wherein the gas shielded arc welding method is provided locally at a portion of the second member that contacts the welding wire. A tensile strength of 570N / mm ² or more, or weld crack sensitivity index _{P CM} is 0.24% or more, the welding wire and steel plate thickness is more than 16mm A method of gas shielded arc welding, fed In the gas shielded arc welding method in which the welding wire is fed while passing through the contact tip in the longitudinal direction, a guide hole through which the welding wire is inserted is provided in front of the contact tip in the wire feeding direction. A wire guide member that guides the welding portion toward the wire target position of the welded portion, the distance between the tip of the contact tip and the guide hole is 5 to 70 mm, and the distance from the guide hole to the arc generation point An iron alloy solid wire having a wire protrusion length of 30 mm or less and the welding wire having an electric resistance of 80 μΩ or more per 1 mm. Or gas-shielded arc welding method, wherein the iron alloy outer skin flux-cored wire.   The wire guide member has a rod-shaped member provided at a tip portion of a shield nozzle that externally fits the contact chip, and the guide hole is formed at a central portion of the rod-shaped member. 4. The gas shielded arc welding method according to 4.   5. The wire guide member according to claim 4, wherein the wire guide member has a lead member provided in front of a tip portion of the contact chip, and the guide hole is formed in a central portion of the lead member. Gas shield arc welding method. The gas shielded arc welding method according to any one of claims 1 to 6, wherein a lubricating oil is applied to the surface of the welding wire in an amount of 0.30 g or more per 10 kg of the wire. The gas shielded arc welding method according to claim 7, wherein the welding wire is not subjected to copper plating on the surface, or is subjected to annealing oxidation while not performing copper plating on the surface.

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