JP6745423B1 - Welding method for thin metal sheet to the surface of thick metal substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method capable of welding a thin metal sheet to a thick metal base material by using arc welding. A method for welding a thin metal sheet to a surface of a thick metal base material, which is made of stainless steel having a thickness of 0.1 mm or more and 1.0 mm or less on a surface of a thick metal base material P1 made of carbon steel. A first welding step of welding the first thin metal sheet P21 is provided, and in the first welding step, a hot wire is used as a welding wire and pulse TIG welding is performed using a pulse current as a welding current. .. [Selection diagram] Figure 1

Description

The present invention relates to a method of welding a thin metal sheet having excellent corrosion resistance and antifouling property to the surface of a thick metal base material by using arc welding.

In recent years, for example, a marine steel structure installed in a harbor area or on the sea has been replaced with a conventional coating, and a metal lining method has been adopted which is maintenance-free and can maintain corrosion resistance and stain resistance for a long period of time. In the metal lining method, for example, a thin metal sheet such as stainless steel, titanium, or a nickel-based alloy is attached and coated on the surface of a steel structure which is a base material.

Patent Literatures 1 and 2 and Non-Patent Literature 1 disclose a welding method for attaching a thin metal sheet made of stainless steel to the surface of a tubular base material by welding. Patent Literature 3 discloses a welding method for attaching a stainless steel plate to the surface of a flat plate-shaped base material by welding. Further, Patent Document 4 discloses a welding method in which TIG (Tungsten Inert Gas) welding, which is a type of arc welding, is used as the welding method.

Japanese Patent No. 4785443 Japanese Patent No. 4975948 Patent No. 4392003 JP, 11-58017, A

Yasuhiro Kawai and 3 others, "High Corrosion Resistant Stainless Steel Lining Welding Technology for Marine Steel Structures", Nippon Steel Technical Report, Nippon Steel & Sumitomo Metal Corporation, 2006, No. 385, p. 86-90

In order to reduce the weight and reduce the material cost, for example, it is considered that a relatively thin thin metal sheet having a thickness of 1.0 mm or less is attached to the surface of the base material by welding. Conventionally, when welding a thin metal sheet to the surface of a base material, combined welding of indirect resistance seam welding and plasma welding has been used.

Since plasma welding has a large torch and is heavy and is expensive as compared with TIG welding, application of TIG welding to the welding of a thin metal sheet and a base material has been studied. However, when the welding methods disclosed in Patent Documents 3 and 4 are used for welding a thin metal sheet and a base material, heat input to the thin metal sheet due to arc energy becomes too large and the thin metal sheet is broken ( It may melt down). In particular, under the welding conditions described in Patent Document 4, even if an attempt is made to weld a thin metal sheet having a thickness of 1.0 mm or less to the surface of the base material, the heat input to the thin metal sheet becomes too large and the thin metal sheet Can be torn and the welding cannot be performed properly.

In Patent Document 1 and Non-Patent Document 1, indirect resistance seam welding is performed before plasma welding or arc welding, and a base material and a thin metal sheet are preliminarily joined to each other, whereby a thin metal sheet produced by plasma welding or arc welding The heat input to the base metal is released to the base material via the indirect resistance seam weld, thereby preventing the thin metal sheet from breaking. When performing indirect resistance seam welding, it is necessary to pressurize the electrode wheel to bring the thin metal sheet and the base material into close contact. If the base material is tubular, it is possible to secure the necessary reaction force of the pressing force by using a tower-shaped indirect seam welding device equipped with a portal frame, but the base material is a large-sized flat plate shape. In this case, it is difficult to arrange the gate-shaped frame so as to straddle the base material. Therefore, it is difficult to apply the welding methods of Patent Document 1 and Non-Patent Document 1 to a flat plate-shaped substrate.

Although Patent Document 2 discloses a method of arc welding a base material and a thin metal sheet, when one thin metal sheet is used, its ends are overlapped and arc welding is performed only on the overlapped part. Be seen. In addition, in the overlapping portion, resistance spot welding or resistance seam welding is performed before arc welding. In the case of using resistance spot welding, in order to allow the heat input to the thin metal sheet during arc welding to escape to the base material by an amount sufficient to prevent the thin metal sheet from breaking, for example, resistance at a narrow pitch of 15 mm is used. Spot welding is required. In this case, the work of resistance spot welding becomes complicated.

There is a demand for a welding method capable of welding a thin metal sheet having a thickness of 1.0 mm or less to a base material by arc welding without performing resistance seam welding or resistance spot welding at a narrow pitch.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a welding method capable of welding a thin metal sheet to a thick metal base material by using arc welding.

In order to solve the above problems, the present invention proposes the following means.

A method of welding a thin metal sheet to a surface of a thick metal base material according to the present invention includes a first stainless steel sheet having a thickness of 0.1 mm or more and 1.0 mm or less on a surface of a thick metal base material made of carbon steel. A first welding step of welding a metal sheet is provided, and in the first welding step, a hot wire is used as a welding wire and pulse TIG welding is performed using a pulse current as a welding current.

By the pulse TIG welding, at the peak current, an arc having high energy capable of melting the thick metal base material and the first thin metal sheet is generated to increase the heat input amount to the thick metal base material and the first thin metal sheet. Enlarge and melt the thick metal substrate and the first thin metal sheet. At the time of the base current, the base current, whose current value is significantly lower than the peak current, is applied to suppress the arc energy while maintaining the arc generation, and the heat input to the thick metal base material and the first thin metal sheet. Is reduced to solidify the thick metal substrate and the first thin metal sheet melted at the peak current. By thus repeating the melting of the thick metal base material and the first thin metal sheet at the peak current and the solidification of the molten metal at the base current, the total heat input to the first thin metal sheet is reduced. It is possible to weld the first thin metal sheet to the thick metal base material by using TIG welding which is a kind of arc welding while preventing the first thin metal sheet from breaking. That is, the first thin metal sheet can be welded to the thick metal base material by arc welding without performing resistance seam welding or resistance spot welding at a narrow pitch. Further, by using a hot wire as the welding wire, it is possible to prevent the unmelted residue of the welding wire even at the time of a base current with a low arc energy (that is, the amount of heat input to the thick metal base material and the first thin metal sheet). You can

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the first welding step, the pulse current has a peak current value of 200 A or more and 250 A or less and a base current value of 20 A or more. It may be 40 A or less.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the first welding step, a ratio of a peak current time per cycle of the pulse current to a pulse cycle of the pulse current is , 40% or more and 60% or less.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the first welding step, a peak current value of the pulse current and a peak current time per cycle of the pulse current, The amount of applied peak current per second obtained by the product of the pulse current and the pulse frequency is 115 A or more and 120 A or less, and the welding speed of the pulse TIG welding is 35 cm/min or more and 60 cm/min or less. The average welding voltage of the pulse TIG welding may be 11.5 V or more and 13.7 V or less.

In the method for welding a thin metal sheet to the surface of a thick metal substrate according to the present invention, the pulse frequency of the pulse current may be 8 Hz or more and 12 Hz or less in the first welding step.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the first welding step, a wire feeding speed for supplying the welding wire is 1.5 m/min or more and 2.6 m/min or more. The value of the hot wire current flowing through the welding wire may be 30 A or more and 45 A or less.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, a gas containing hydrogen may be used as a shield gas in the first welding step.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, after the first welding step, the first thin metal sheet has a thickness of 0.1 mm or more and 1.0 mm or less. A second welding step of welding a second thin metal sheet made of stainless steel is further provided, and in the second welding step, hot wire is used as a welding wire and pulse TIG welding is performed using a pulse current as a welding current. May be.

Further, in the method for welding a thin metal sheet to the surface of a thick metal substrate according to the present invention, in the second welding step, the pulse current has a peak current value of 200 A or more and 250 A or less and a base current value of 20 A or more. It may be 40 A or less.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the second welding step, a ratio of a peak current time per cycle of the pulse current to a pulse cycle of the pulse current is , 20% or more and 30% or less.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the second welding step, a peak current value of the pulse current, and a peak current time per cycle of the pulse current, The input current amount of the peak current per second obtained by the product of the pulse current and the pulse frequency is 68 A or more and 72 A or less, and the welding speed of the pulse TIG welding is 36 cm/min or more and 65 cm/min or less. The average welding voltage of the pulse TIG welding may be 10.5 V or more and 12.2 V or less.

In the method for welding a thin metal sheet to the surface of a thick metal substrate according to the present invention, the pulse frequency of the pulse current may be 8 Hz or more and 12 Hz or less in the second welding step.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the second welding step, a wire feeding speed for supplying the welding wire is 1.2 m/min or more and 2.5 m/min or more. The value of the hot wire current flowing through the welding wire may be 30 A or more and 45 A or less.

Further, in the method for welding a thin metal sheet to the surface of a thick metal substrate according to the present invention, a gas containing hydrogen may be used as a shield gas in the second welding step.

Further, in the method for welding a thin metal sheet to a surface of a thick metal base material according to the present invention, in the first welding step, the base material and the first thin metal sheet are resisted before the pulse TIG welding. Spot welding may be used.

Further, in the method for welding a thin metal sheet to the surface of a thick metal base material according to the present invention, the base material may have a flat plate shape.

Further, in the method for welding a thin metal sheet to a surface of a thick metal substrate according to the present invention, in the first welding step, the first thin metal sheet is arranged on the substrate, A rail is arranged on at least one of the thin metal sheets of 1 or around the base material, and a welding device is moved on the rail to automatically move the base material and the first thin metal sheet. Pulse TIG welding may be used.

According to the present invention, thin metal sheets can be welded to thick metal substrates using arc welding.

It is the front view which fractured|ruptured a part of welding apparatus used for the welding method of the thin metal sheet to the surface of the thick metal base material which concerns on embodiment of this invention. It is a figure for demonstrating the 1st welding process of the welding method which concerns on embodiment of this invention. It is a figure for demonstrating the 2nd welding process of the welding method which concerns on embodiment of this invention. It is a figure which shows the welding conditions in the 1st welding process of the welding method which concerns on embodiment of this invention. It is a figure which shows the welding conditions in the 2nd welding process of the welding method which concerns on embodiment of this invention. It is a figure which shows the welding conditions of Example 1 of the welding method which concerns on embodiment of this invention, and a determination result. It is a figure which shows the welding conditions and the determination result of Example 2 of the welding method which concerns on embodiment of this invention.

Hereinafter, a method for welding a thin metal sheet to a surface of a thick metal substrate according to an embodiment of the present invention (hereinafter, simply referred to as a welding method) will be described with reference to FIGS.

FIG. 1 is a partially cutaway front view of a welding device 1 used in the welding method of the present embodiment. The welding device 1 is for performing TIG (Tungsten Inert Gas) welding, which is a type of arc welding. The welding device 1 also performs TIG welding using a hot wire. The configuration of the welding device 1 is not limited to this example.

The welding device 1 includes, for example, a welding torch 11, a welding head 21, and a control unit 41.

The welding torch 11 has a TIG electrode 12, a wire guide portion 13, and a torch body 14. The TIG electrode 12 is formed of a metal such as tungsten in a rod shape. The TIG electrode 12 extends in the up-down direction. The wire guide portion 13 is formed of a non-conductive material such as ceramics and has a tubular shape. The wire guide portion 13 is arranged such that the lower end portion thereof is adjacent to the lower end portion of the TIG electrode 12. A welding wire W is arranged in the wire guide portion 13. The welding wire W is point-contacted and electrically connected by a wire power supply (not shown) installed in the wire guide portion 13. As the welding wire W, for example, a Ni-based alloy material having high corrosion resistance is used.

The torch main body 14 has a built-in delivery portion 15 for supplying the welding wire W to the tip side. For example, the delivery unit 15 includes a pair of rollers 15a and a roller drive motor (not shown) that drives the pair of rollers 15a. The welding wire W is arranged between the pair of rollers 15a. The welding wire W is supplied to the tip side by the roller drive motor rotating the pair of rollers 15a in a predetermined direction. The TIG electrode 12 and the upper ends of the wire guide portions 13 are fixed to the lower portion of the torch body 14, respectively.

The welding head 21 has a head main body 22 and a transport unit 23. The head body 22 is connected to the torch body 14 by a connecting member 24. The transport unit 23 has wheels 25 and wheel drive motors (not shown). The wheel 25 is arranged on a rail (rail) R arranged at a desired position and moves along the rail R. The wheel drive motor rotates the wheel 25.

The device body 30 and the torch body 14 of the welding torch 11 are connected by a connection cable 32. Wiring and a welding wire W are arranged in the connection cable 32. A winding device 33 for winding the base end portion of the welding wire W is attached to the device body 30. The winding device 33 is rotatable with respect to the device body 30.

The control unit 41 has an arithmetic circuit and a memory (not shown), and an input unit 42. The arithmetic circuit has a CPU (Central Processing Unit) and the like. A roller drive motor and a wheel drive motor are connected to the arithmetic circuit. The arithmetic circuit controls the roller drive motor and the wheel drive motor. A control program for controlling the arithmetic circuit is stored in the memory. The input unit 42 has, for example, a switch or the like. The switch is attached to the outer surface of the device body 30. The input given by the operator operating the switch is transmitted to the arithmetic circuit. The arithmetic circuit controls the roller drive motor and the like based on the received input and control program.

A welding method in which a thin metal sheet P2 made of stainless steel is welded to the surface of a thick metal base material P1 made of carbon steel (hereinafter simply referred to as a base material P1) using the welding apparatus 1 configured as described above. Will be described. In the present embodiment, a plurality of small thin metal sheets P21, P22,... Are used as the thin metal sheet P2. The small thin metal sheets P21, P22,... Are sequentially welded to the base material P1 to weld the thin metal sheet P2 to the entire surface of the base material P1.

The base material P1 and the thin metal sheet P2 (small thin metal sheets P21, P22,...) Are formed in a rectangular shape in a plan view when viewed in the respective thickness directions. The small thin metal sheets P21, P22,... Have the same shape as each other. The small thin metal sheets P21, P22,... May have different shapes.

The thickness of the thin metal sheet P2 (small thin metal sheets P21, P22,...) Is 0.1 mm or more and 1.0 mm or less. The thickness of the thin metal sheet P2 (small thin metal sheets P21, P22,...) Is more preferably 0.4 mm or more and 1.0 mm or less. The thickness of the base material P1 is not particularly limited, but is sufficiently thicker than the thickness of the thin metal sheet P2, for example.

First, as shown in FIG. 2, a small thin metal sheet P21 (first thin metal sheet) is arranged on the base material P1 and the small thin metal sheet P21 is welded to the base material P1 (first welding step). .. That is, in the first welding step, the base material P1 and the thin metal sheet P2 are welded. Thereafter, as shown in FIG. 3, the small thin metal sheet P22 (second thin metal sheet) is arranged on the base material P1 such that the edge portion thereof overlaps the edge portion of the small thin metal sheet P21. The small thin metal sheet P22 is welded to the small thin metal sheet P21 at a portion overlapping with the small thin metal sheet P21 (second welding step). That is, in the second welding step, the thin metal sheets P2 are welded to each other. Of the small thin metal sheet P22, the small thin metal sheet P22 does not overlap the small thin metal sheet P21 and is directly arranged on the base material P1. The small thin metal sheet P22 is welded to the base material P1 (third welding step). That is, in the third welding step, the base material P1 and the thin metal sheet P2 are welded. The second welding process and the third welding process are repeated until the entire surface of the base material P1 is covered with the small thin metal sheets P21, P22,....

The first welding step will be described in detail. First, as shown in FIG. 2, the small thin metal sheet P21 is arranged on the base material P1. The small thin metal sheet P21 is arranged so as to cover the surface of the base material P1. The small thin metal sheet P21 is preferably arranged at a corner of the base material P1.

Then, the small thin metal sheet P21 is temporarily attached on the base material P1. Specifically, as shown in FIG. 2, a plurality of ends of the small thin metal sheet P21 are fixed to the base material P1 by using, for example, TIG welding. By this TIG welding, a plurality of temporary welded portions W1 are formed at the ends of the small thin metal sheet P21. The installation interval of the tack welded portion W1 is, for example, 50 mm. The tack weld portion W1 is preferably formed over the entire circumference of the edge of the small thin metal sheet P21. Further, in addition to the tack welding portion W1, a plurality of end portions of the small thin metal sheet P21 may be fixed to the base material P1 by resistance spot welding. By this resistance spot welding, a plurality of resistance spot welds W2 are formed at the ends of the small thin metal sheet P21. The installation interval of the resistance spot welds W2 is, for example, 25 mm. The installation interval of the resistance spot welds W2 may be smaller than 25 mm.

After that, the rail R is arranged on at least one of the base material P1 and the small thin metal sheet P21. The rail R may be arranged around the base material P1.

Then, the welding device 1 is moved on the rail R to automatically perform pulse TIG welding on the base material P1 and the small thin metal sheet P21. That is, the edge of the small thin metal sheet P21 is fillet welded to the base material P1.

Specifically, the operator operates the input unit 42 to activate the welding device 1. A welding current is supplied from a TIG welding power source (not shown) to generate an arc between the TIG electrode 12 and the base material P1 and the small thin metal sheet P21. The arc energy melts the base material P1 and the small thin metal sheet P21 to form a molten pool. A hot wire current is supplied to the welding wire W from a wire power supply (not shown) to heat the welding wire W by Joule heat. The roller drive motor is driven to supply the heated welding wire W so that the tip of the welding wire W contacts the molten pool. The wheel drive motor is driven to move the welding device 1 (welding head 21) with respect to the rail R at a predetermined welding speed, and the welding of the small thin metal sheet P21 and the base material P1 is advanced. In order to stabilize the arc and protect the molten metal from the atmosphere, a shield gas is supplied from a gas supply device (not shown) between the TIG electrode 12 and the base material P1 and the small thin metal sheet P21. ..

In this embodiment, a pulse current is used as the welding current from the TIG welding power source. The pulse current is a current that is alternately changed to a peak current and a base current at a predetermined pulse period T _C. That is, in the first welding process, pulse TIG welding using a pulse current as the welding current is performed.

The reason for performing pulse TIG welding will be described. Since the base material P1 and the small thin metal sheet P21 (thin metal sheet P2) are made of different materials, they have different melting points. For example, the melting point of the carbon steel base material P1 is about 1450°C, and the melting point of the stainless steel thin metal sheet P2 is about 1400°C. The melting point of the welding wire W is about 1350°C. In addition, since the base material P1 and the thin metal sheet P2 have large differences in thickness, there is a large difference in heat capacity.

When welding the base material P1 and the small thin metal sheet P21, it is necessary to generate an arc capable of melting the base material P1 having a high melting point and a large plate thickness (large heat capacity). In normal TIG welding, since the welding current is always constant and an arc having high energy capable of melting the base material P1 is constantly generated, the amount of heat input from the arc to the small thin metal sheet P21 becomes too large. As a result, the small thin metal sheet P21, which has a melting point lower than that of the base material P1 and has a plate thickness of 1.0 mm or less, is greatly broken. Further, when the torn small thin metal sheet P21 contracts, a hole (falling out of the small thin metal sheet P21) is generated in the small thin metal sheet P21.

In this embodiment, a pulse current is used as the welding current. At the time of the peak current, an arc having high energy capable of melting the base material P1 and the small thin metal sheet P21 is generated to melt the base material P1 and the small thin metal sheet P21. At the time of the base current, the arc current (that is, the amount of heat input to the base material P1 and the small thin metal sheet P21) is lowered while maintaining the generation of the arc by passing the base current having a lower current value than the peak current. The substrate P1 and the small thin metal sheet P21 melted at the peak current are solidified while being suppressed. By repeating the peak current and the base current, it is possible to weld the base material P1 and the small thin metal sheet P21 using TIG welding while suppressing the total heat input and preventing the small thin metal sheet P21 from breaking. ..

Further, in this embodiment, pulse TIG welding using a hot wire is performed. That is, the welding wire W is supplied to the molten pool while being heated by the hot wire current. Since it is not necessary to heat/melt the welding wire W by the arc energy, or the energy consumption for heating/melting the welding wire W by the arc energy can be reduced, the total amount of the welding wire W can be reduced as compared with the case of using the cold wire. The arc energy can be reduced. That is, since the total heat input to the base material P1 and the small thin metal sheet P21 can be suppressed, it is possible to more effectively prevent the small thin metal sheet P21 from breaking. Further, by using the hot wire, it is possible to prevent the unmelted residue of the welding wire W even at the time of the base current when the arc energy (that is, the amount of heat input to the base material P1 and the thin metal sheet P2) is low.

Furthermore, in the present embodiment, a mixed gas of argon (Ar) and hydrogen (H ₂ ) is used as the shield gas. For example, as the shield gas, an Ar-5% H ₂ mixed gas in which hydrogen is added to argon by 5% by volume is used. Hydrogen promotes an endothermic reaction in an arc atmosphere and absorbs arc energy. Therefore, by using the mixed gas of argon and hydrogen as the shield gas, the heat input to the base material P1 and the small thin metal sheet P21 is reduced, and the breakage of the small thin metal sheet P21 is more effectively prevented. You can In order to effectively absorb the arc energy with hydrogen, the amount of hydrogen added to argon is preferably 3% by volume or more. On the other hand, in order to prevent cold cracking due to an increase in the amount of hydrogen taken into the weld between the base material P1 and the small thin metal sheet P21, the amount of hydrogen added to argon is preferably 7% by volume or less.

Hereinafter, with reference to FIG. 4, welding conditions suitable for welding the base material P1 and the small thin metal sheet P21 in the first welding process will be described.

The welding speed of pulse TIG welding, which is the speed at which the wheel driving motor is driven to move the welding head 21, is preferably 35 cm/min or more and 60 cm/min or less. If the welding speed is slower than 35 cm/min, the small thin metal sheet P21 may be broken due to an increase in heat input. If the welding speed is higher than 60 cm/min, the heat input amount may be insufficient, the base material P1 and the small thin metal sheet P21 may not be melted, and welding defects (poor penetration) may occur.

Here, in the present embodiment, pulse TIG welding using a hot wire is performed as described above, but a pulse current hot wire is used as the hot wire in order to keep the welding speed within the above range (that is, hot A pulse current is preferably used as the wire current). The frequency of the pulse current as the hot wire current is preferably 50 to 200 Hz.

By using a pulsed hot wire, the welding speed can be increased (for example, 35 cm/min or more). The reason for this will be described below.
First, by using a hot wire in pulse TIG welding, it is not necessary to heat/melt the welding wire W by arc energy, or the energy consumption for heating/melting the welding wire W by arc energy can be reduced. You can increase the speed. The welding speed can be increased as the temperature of the welding wire W (hot wire) is higher.
For example, when a constant current hot wire is used as the hot wire (that is, a constant current is used as the hot wire current), the current of the hot wire current (constant current) in order to increase the temperature of the welding wire W (hot wire). If the value is increased, the arc is deflected by the wire energization, so-called magnetic blow occurs, and the welding becomes unstable. Therefore, there is a limit to increase the current value of the hot wire current (constant current), and it is difficult to sufficiently heat the welding wire W (just below the melting point). As a result, it is difficult to increase the welding speed to 35 cm/min.
On the other hand, when a pulsed hot wire is used as the hot wire, it is possible to secure a period in which magnetic blowing does not occur at a base current having a small current value, although magnetic blowing occurs at a peak current having a large current value. In addition, it is possible to suppress the influence of this on the welding operation by making the magnetic blow at the peak current instantaneous. That is, even if the current value of the hot wire current (pulse current) is increased, it is possible to prevent the welding from becoming unstable. Therefore, the current value of the hot wire current (pulse current) can be increased to a desired value, and the welding wire W can be supplied to the molten pool while being heated to just below the melting point. As a result, the welding speed can be increased to, for example, 35 cm/min or more.

The peak current value I _P of the pulse current is preferably 200 A (ampere) or more and 250 A or less. If the peak current value I _P is less than 200 A, the heat input amount may be insufficient, the base material P1 and the small thin metal sheet P21 may not be melted, and welding defects (defective penetration) may occur. If the peak current value I _P is larger than 250 A, the small thin metal sheet P21 may be broken due to an increase in heat input.

The base current value I _B of the pulse current is preferably 20 A or more and 40 A or less. If the base current value I _B is less than 20 A, the arc may disappear and welding may not be possible. When the base current value I _B is larger than 40 A, the small thin metal sheet P21 may melt even during the base current, and the small thin metal sheet P21 may be broken.

The pulse frequency f is preferably 8 Hz or more and 12 Hz or less. When the pulse frequency f is higher than 12 Hz, the time during which the base current flows is shortened, and there is a possibility that sufficient time for solidifying the base material P1 and the small thin metal sheet P21 melted at the peak current cannot be secured. If the pulse frequency f is less than 8 Hz, the ripple pattern on the surface of the weld bead in the welded portion between the base material P1 and the small thin metal sheet P21 becomes deep, and an instruction pattern may occur in the fluorescent penetrant inspection. There is.

With respect to the pulse period T _C, the ratio of the peak current time T _P per period (hereinafter, simply referred to as the ratio of the peak current time T _P) is preferably not more than 40% to 60%. If the ratio of the peak current time T _P is less than 40%, the heat input amount may be insufficient, the base material P1 and the small thin metal sheet P21 may not be melted, and a welding defect (defective penetration) may occur. If the ratio of the peak current time T _P is larger than 60%, the small thin metal sheet P21 may be broken due to an increase in heat input.

Further, in the present embodiment, as a parameter for managing the heat input amount, the peak current value I _P , the peak current time T _P per cycle, and the pulse frequency f The input current amount S at the peak current is used. By appropriately managing the input current amount S at the peak current per second, the heat input amount at the peak current is controlled by the base material P1 and the small thin metal sheet P21 while preventing the small thin metal sheet P21 from breaking. It can be adjusted so that it can be sufficiently melted. The applied current amount S at the peak current per second is preferably 115 A or more and 120 A or less. If the input current amount S at the peak current per second is smaller than 115 A, the heat input amount may be insufficient, the base material P1 and the small thin metal sheet P21 may not be melted, and welding defects (poor penetration) may occur. is there. When the input current amount S at the peak current per second is larger than 120 A, the small thin metal sheet P21 may be broken due to the increase in the heat input amount.

The average welding voltage of pulse TIG welding is preferably 11.5 V (volt) or more and 13.7 V or less. The average welding voltage is determined by the distance between the TIG electrode 12 and the small thin metal sheet P21. If the average welding voltage is lower than 11.5 V, the TIG electrode 12 and the small thin metal sheet P21 may come into contact with each other. If the average welding voltage is higher than 13.7 V, the small thin metal sheet P21 may be broken due to an increase in heat input.

The wire feeding speed for driving the roller driving motor to supply the welding wire W is preferably 1.5 m/min or more and 2.6 m/min or less. By setting the wire feeding speed in the above range, the amount of welding wire W to be used can be suppressed, and the welded portion between the base material P1 and the small thin metal sheet P21 can be made large enough to secure the yield strength of the welded portion. can do.

The energization distance of the welding wire W and the hot wire current value flowing through the welding wire W are determined so that the welding wire W is heated to just below the melting point immediately before being inserted into the molten pool. The energization distance of the welding wire W is determined by the specifications of the welding device 1, and is, for example, 57 mm. The hot wire current value is determined by the wire feeding speed and the energization distance, but is preferably 30 A or more and 45 A or less, for example.

The relative position between the TIG electrode 12 and the welding wire W is determined so that the tip of the welding wire W is directly inserted into the molten pool while preventing the welding wire W from being melted by the heat of the arc. For example, the tip of the TIG electrode 12 is arranged so as to be positioned about 2 mm to 3 mm behind the tip of the welding wire W in the welding line direction (that is, the direction along the rail R). Further, the tip of the TIG electrode 12 extends from the same position as the tip of the welding wire W in the direction orthogonal to the welding line along the plane of the base material P1 (hereinafter, also referred to as the welding line orthogonal direction), and It is arranged so that it is located 1 mm from the tip to a position on the side of the base material P1. If the distance between the tip of the welding wire W and the tip of the TIG electrode 12 is too short, the welding wire W is melted by the heat of the arc and the welding becomes unstable. If the distance between the tip of the welding wire W and the tip of the TIG electrode 12 is too large, the tip of the welding wire W will come off the molten pool, and the weld bead cannot be formed. The relative position between the TIG electrode 12 and the welding wire W is not limited to the above.

Next, the second welding step and the third welding step will be described in detail. First, as shown in FIG. 3, the small thin metal sheet P22 is arranged on the base material P1. At this time, the small thin metal sheet P22 is arranged so that the end thereof overlaps the end of the small thin metal sheet P21.

Then, the small thin metal sheet P22 is temporarily attached on the small thin metal sheet P21 and the base material P1. Specifically, as shown in FIG. 3, a plurality of ends of the small thin metal sheet P22 are fixed to the small thin metal sheet P21 and the base material P1 by using, for example, TIG welding. By this TIG welding, a plurality of temporary welded portions W3 are formed at the ends of the small thin metal sheet P22. The installation interval of the tack welding portion W3 is, for example, 30 mm. The tack weld portion W3 is preferably formed over the entire circumference of the edge of the small thin metal sheet P22. Note that resistance spot welding is not performed in the second welding process.

Then, the rail R is arranged on at least one of the base material P1, the small thin metal sheet P21, and the small thin metal sheet P22. The rail R may be arranged around the base material P1.

Then, the welding apparatus 1 is moved on the rail R to automatically perform pulse TIG welding on the small thin metal sheet P21 and the small thin metal sheet P22, or the base material P1 and the small thin metal sheet P22. That is, the edge of the small thin metal sheet P22 is fillet welded to the small thin metal sheet P21 or the base material P1. The operation of the welding apparatus 1 in the second welding process and the third welding process is the same as that in the first welding process, and thus the description thereof is omitted here.

Also in the second welding process and the third welding process, similar to the first welding process, the hot wire is used as the welding wire W and the pulse TIG welding is performed using the pulse current as the welding current. Also in the second welding process and the third welding process, as in the first welding process, a mixed gas of argon (Ar) and hydrogen (H ₂ ) is used as the shield gas.

Hereinafter, the welding conditions suitable for welding the small thin metal sheet P21 and the small thin metal sheet P22 in the second welding step will be described with reference to FIG. Note that the third welding process is performed under the same welding conditions as the first welding process, and thus the description thereof is omitted here.

In the second welding process, the small thin metal sheets P21, P22 are melted while preventing breakage of the small thin metal sheets P21, P22 at the peak current, and the molten small thin metal sheets P21, P22 are melted at the base current. Perform the action of solidifying. That is, in the second welding step, since the thin metal sheets P2 are welded to each other (small thin metal sheets P21 and P22), the arc energy required for melting the small thin metal sheets P21 and P22 is different from that in the first welding step. Becomes smaller. Therefore, the second welding process is performed under welding conditions different from those of the first welding process.

The welding speed of pulse TIG welding, which is the speed at which the wheel driving motor is driven to move the welding head 21, is preferably 36 cm/min or more and 65 cm/min or less. If the welding speed is slower than 36 cm/min, the small thin metal sheets P21 and P22 will be broken due to the increase in heat input, or the small thin metal sheets P21 and P22 that have been excessively melted due to the increase in heat input will drop by gravity. Welding defects (overlap) may occur. If the welding speed is higher than 65 cm/min, hot cracking may occur.

The peak current value I _P of the pulse current is preferably 200 A or more and 250 A or less. If the peak current value I _P is less than 200 A, the heat input amount may be insufficient, the small thin metal sheets P21 and P22 may not be melted, and welding defects (melting failure) may occur. If the peak current value I _P is larger than 250 A, the small thin metal sheets P21 and P22 will be broken due to the increase in heat input, or the small thin metal sheets P21 and P22 that have been excessively melted due to the increase in heat input will be gravity. There is a possibility of sagging and welding defects (overlap).

The base current value I _B of the pulse current is preferably 20 A or more and 40 A or less. If the base current value I _B is less than 20 A, the arc may disappear and welding may not be possible. When the base current value I _B is larger than 40 A, the small thin metal sheets P21 and P22 are melted even during the base current and the small thin metal sheets P21 and P22 are broken, or are excessively melted due to an increase in heat input. The small thin metal sheets P21 and P22 may hang down due to gravity, and welding defects (overlap) may occur.

The pulse frequency f is preferably 8 Hz or more and 12 Hz or less. When the pulse frequency f is higher than 12 Hz, the base current flows for a short time, and thus it may not be possible to secure the time for solidifying the melted small thin metal sheets P21, P22 at the peak current. If the pulse frequency f is lower than 8 Hz, the ripple pattern on the surface of the weld bead in the welded portions of the small thin metal sheets P21 and P22 becomes deep, and an instruction pattern may occur in the fluorescent penetrant inspection.

The ratio of the peak current time T _P per cycle to the pulse cycle T _C is preferably 20% or more and 30% or less. If the ratio of the peak current time T _P is less than 20%, the heat input amount may be insufficient, the small thin metal sheets P21 and P22 may not be melted, and welding defects (melting failure) may occur. When the ratio of the peak current time T _P is larger than 30%, the small thin metal sheets P21 and P22 are broken due to an increase in heat input, or the small thin metal sheets P21 and P22 excessively melted due to an increase in heat input. May hang down due to gravity, resulting in welding defects (overlap).

The applied current amount S at the peak current per second is preferably 68 A or more and 72 A or less. If the input current amount S at the peak current per second is smaller than 68 A, the heat input amount is insufficient, the small thin metal sheets P21 and P22 do not melt, and welding defects (defective melting) may occur. If the input current amount S at the peak current per second is larger than 72 A, the small thin metal sheets P21 and P22 are broken due to the increase in heat input, or the small thin metal excessively melted due to the increase in heat input. The sheets P21 and P22 may hang down due to gravity, and a welding defect (overlap) may occur.

The average welding voltage of pulse TIG welding is preferably 10.5 V or more and 12.2 V or less. If the average welding voltage is lower than 10.5 V, the TIG electrode 12 and the small thin metal sheet P22 may come into contact with each other. If the average welding voltage is higher than 12.2 V, the small thin metal sheets P21 and P22 will be broken due to an increase in heat input, or the small thin metal sheets P21 and P22 excessively melted due to an increase in heat input will be gravity. There is a possibility of sagging and welding defects (overlap).

The wire feeding speed for driving the roller driving motor to supply the welding wire W is preferably 1.2 m/min or more and 2.5 m/min or less. The energization distance of the welding wire W is determined by the specifications of the welding device 1, and is, for example, 57 mm. The hot wire current value flowing through the welding wire W is preferably 30 A or more and 45 A or less, for example. The reason for setting the wire feeding speed, the energization distance, and the range of the current value of the hot wire current is the same as that of the welding condition in the above-mentioned first welding step, and thus the description thereof is omitted.

The relative position between the TIG electrode 12 and the welding wire W is such that the welding wire W is prevented from being melted by the heat of the arc generated between the TIG electrode 12 and the small thin metal sheets P21 and P22. The tip of the is set to be directly inserted into the molten pool. For example, the tip of the TIG electrode 12 is arranged so as to be positioned about 2 mm to 5 mm behind the tip of the welding wire W in the welding line direction. In addition, the tip of the TIG electrode 12 is arranged so as to be, in the direction orthogonal to the welding line, from the same position as the tip of the welding wire W to a position 1 mm smaller than the tip of the welding wire W on the side of the small thin metal sheet P21. To be done. The relative position between the TIG electrode 12 and the welding wire W is not limited to the above.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

As Example 1, the welding conditions were changed, the base material P1 and the small thin metal sheet P21 were welded in the first welding step, and the pass/fail of the welded portion was determined based on the results of the visual inspection and the fluorescent penetrant inspection. As the base material P1, SM490YA having a size of 3550 mm×1950 mm and a plate thickness of 12 mm was used. As the small thin metal sheet P21 (thin metal sheet P2), SUS312L having a size of 200 mm×1550 mm and a plate thickness of 1 mm was used.

FIG. 6 shows the welding conditions and the determination results of Examples 1-1 to 1-10 and Comparative examples 1-1 to 1-8. The welding conditions not shown in FIG. 6 were the same in all of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-8. Specifically, the average welding voltage was 12.0 V and the energization distance was 57 mm. Further, the tip of the TIG electrode 12 was located 3 mm behind the tip of the welding wire W in the welding line direction, and was arranged so as to be at the same position as the tip of the welding wire W in the direction orthogonal to the welding line.

In Examples 1-1 to 1-10 in which welding was performed while satisfying the proper welding condition range shown in FIG. 4, good results were shown in both the visual inspection and the fluorescent penetrant inspection, and the results were judged to be acceptable. In Examples 1-1 to 1-10, the operation of melting the base material P1 and the small thin metal sheet P21 at the peak current and solidifying the melted base material P1 and the small thin metal sheet P21 at the base current is performed. Since it was performed reliably, it is considered that good results were shown in both the visual inspection and the fluorescent penetrant inspection.

On the other hand, with respect to Comparative Examples 1-1 to 1-8 that did not satisfy the welding conditions, they were defective in at least one of the visual inspection and the fluorescent penetrant inspection, and were rejected.

Specifically, in Comparative Examples 1-1 and 1-2, both the visual inspection and the fluorescent penetrant inspection were defective. As a cause of this, in Comparative Examples 1-1 and 1-2, the peak current value I _P is larger than the welding condition (200 A or more and 250 A or less) and the base current value I _B is larger than the welding condition (20 A or more and 40 A or less). Therefore, it is considered that the amount of heat input is large and the small thin metal sheet P21 is torn.

In Comparative Examples 1-3 to 1-7, a large number of instruction patterns were generated in the fluorescent penetrant inspection, and they were rejected. As a cause of this, in Comparative Examples 1-3 to 1-7, the peak current value I _P satisfied the predetermined welding condition, but the base current value I _B was larger than the predetermined welding condition, so that the small size was achieved even at the base current. It is conceivable that the thin metal sheet P21 was melted and the small thin metal sheet P21 was torn or a welding defect (overlap) occurred. In particular, in Comparative Example 1-7, even though other than the base current I _B is satisfied the welding conditions, greater than the welding condition-based current I _B is a 42.0A, determination result and rejected became.

Further, in Comparative Example 1-8, welding could not be performed because the arc was not stable. As this reason, in Comparative Example 1-8, since the base current I _B is smaller than the welding conditions and 19.0A, it is conceivable that an arc is lost.

Further, in Comparative Examples 1-1 to 1-5, the input current amount S at the peak current per second used as a parameter for managing the heat input amount in the present embodiment is the welding condition (115 A or more and 120 A or less). ) Was greater than. That is, in Comparative Examples 1-1 to 1-5, it is considered that the heat input amount was not properly managed, and the small thin metal sheet P21 was torn due to the increase in the heat input amount.

As Example 2, the welding conditions were changed, the small thin metal sheets P21 and P22 were welded in the second welding step, and the pass/fail of the welded portion was determined based on the results of the visual inspection and the fluorescent penetrant inspection. As the small thin metal sheets P21 and P22 (thin metal sheet P2), SUS312L having a size of 200 mm×1550 mm and a plate thickness of 1 mm was used.

FIG. 7 shows welding conditions of Examples 2-1 to 2-17 and Comparative examples 2-1 to 2-10, and determination results. The welding conditions not shown in FIG. 7 are the same in all of Examples 2-1 to 2-17 and Comparative examples 2-1 to 2-10. Specifically, the average welding voltage was 11.0 V and the energization distance was 57 mm. Further, the tip of the TIG electrode 12 was positioned 5 mm behind the tip of the welding wire W in the welding line direction, and was arranged so as to be at the same position as the tip of the welding wire W in the direction orthogonal to the welding line.

In Examples 2-1 to 2-17 in which welding was performed while satisfying the proper welding condition range shown in FIG. 5, good results were shown in both the visual inspection and the fluorescent penetrant inspection, and passed. In Examples 2-1 to 2-17, the operation of melting the small thin metal sheets P21 and P22 at the peak current and solidifying the small thin metal sheets P21 and P22 melted at the base current is reliably performed. Therefore, it is considered that good results were shown in both the visual inspection and the fluorescent penetrant inspection.

On the other hand, for Comparative Examples 2-1 to 2-10 that did not satisfy the welding conditions, a large number of instruction patterns were generated in the fluorescent penetrant inspection (that is, the fluorescent penetrant inspection was defective), and the judgment was rejected. ..

In Comparative Examples 2-1 and 2-2, since the peak current value I _P was larger than the welding condition (200 A or more and 250 A or less) and the base current value I _B was larger than the welding condition (20 A or more and 40 A or less), the heat input amount And the small thin metal sheets P21 and P22 are torn.

In Comparative Examples 2-3 to 2-9, the applied current amount S at the peak current per second, which was used as a parameter for managing the heat input amount in the present embodiment, was determined from the welding conditions (68 A or more and 72 A or less). Was also great. That is, in Comparative Examples 2-3 to 2-9, it is considered that the heat input amount was not properly managed, and the small thin metal sheets P21 and P22 were torn due to the increase in the heat input amount.

In Comparative Example 2-10, argon gas was used as the shield gas. That is, since the shield gas did not contain hydrogen and the arc energy was not absorbed by the shield gas, the heat input to the small thin metal sheets P21, P22 increased and the small thin metal sheets P21, P22 were torn. Conceivable.

The welding method according to the present embodiment includes a first welding step of welding the small thin metal sheet P21 on the surface of the base material P1. In the first welding step, a hot wire is used as the welding wire W and a welding current is used. Pulse TIG welding using pulse current is performed.

By the pulse TIG welding, at the peak current, an arc having high energy capable of melting the base material P1 and the small thin metal sheet P21 is generated to increase the heat input amount to the base material P1 and the small thin metal sheet P21. The material P1 and the small thin metal sheet P21 are melted. At the time of the base current, a base current having a current value significantly lower than the peak current is flowed to suppress the arc energy while maintaining the generation of the arc and reduce the heat input to the base material P1 and the small thin metal sheet P21. Then, the base material P1 and the small thin metal sheet P21 melted at the peak current are solidified. By repeating the melting of the base material P1 and the small thin metal sheet P21 at the peak current and the solidification of the molten metal at the base current as described above, the total heat input to the small thin metal sheet P21 is reduced and the small thin metal sheet P21 is reduced. The small thin metal sheet P21 can be welded to the base material P1 by TIG welding which is a kind of arc welding while preventing the metal sheet P21 from breaking. That is, the small thin metal sheet P21 can be welded to the base material P1 by arc welding without performing resistance seam welding or resistance spot welding at a narrow pitch. Further, by using a hot wire as the welding wire W, it is possible to prevent the unmelted residue of the welding wire W even when the arc energy (that is, the amount of heat input to the base material P1 and the small thin metal sheet P21) is low. You can

In the first welding step, the pulse current has a peak current value I _P of 200 A or more and 250 A or less and a base current value I _B of 20 A or more and 40 A or less. By setting the peak current value I _P and the base current value I _B in the above ranges, the base material P1 and the small thin metal sheet P21 are melted at the peak current, and the base material P1 and the small thin metal sheet P21 are melted at the base current. It is possible to reliably perform the operation of solidifying the.

In the first welding step, the ratio of the peak current time T _P per cycle of the pulse current to the pulse cycle T _C of the pulse current is 40% or more and 60% or less. By setting the ratio of the peak current time T _{P in} the above range, the base material P1 and the small thin metal sheet P21 are melted at the peak current, and the melted base material P1 and the small thin metal sheet P21 are solidified at the base current. It is possible to perform the operation of more reliably.

In the first welding step, the peak current value I _P , the peak current time T _P per cycle of the pulse current, and the peak current per second obtained by the product of the pulse frequency f of the pulse current The applied current amount S is 115 A or more and 120 A or less, the welding speed of pulse TIG welding is 35 cm/min or more and 60 cm/min or less, and the average welding voltage of pulse TIG welding is 11.5 V or more and 13.7 V or less. By setting the input current amount S at the peak current per second, the average welding voltage, and the welding speed within the above ranges, the heat input amount to the base material P1 and the small thin metal sheet P21 at the peak current is adjusted, and the peak It is possible to melt the base material P1 and the small thin metal sheet P21 while preventing breakage of the small thin metal sheet P21 when an electric current is applied.

In the first welding process, the pulse frequency f of the pulse current is 8 Hz or more and 12 Hz or less. By setting the pulse frequency f within the above range, the operation of melting the base material P1 and the small thin metal sheet P21 at the peak current and solidifying the melted base material P1 and the small thin metal sheet P21 at the base current is ensured. It becomes possible to do it.

In the first welding step, the wire feeding speed for supplying the welding wire W is 1.5 m/min or more and 2.6 m/min or less, and the hot wire current value flowing in the welding wire W is 30 A or more and 45 A or less. .. By setting the wire feeding speed in the above range, the amount of welding wire W to be used can be suppressed, and the welded portion between the base material P1 and the small thin metal sheet P21 can be made large enough to secure the yield strength of the welded portion. can do. Further, by setting the wire feeding speed and the hot wire current value within the above ranges, the temperature of the welding wire W immediately before being supplied to the molten portion of the base material P1 and the small thin metal sheet P21 is directly below the melting point. W can be heated.

Further, after the first welding step, a second welding step of welding the small thin metal sheet P21 to the small thin metal sheet P22 is further provided, and in the second welding step, a hot wire is used as the welding wire W and a welding current is used. As a result, pulse TIG welding using a pulse current is performed. By the pulse TIG welding, at the peak current, an arc having high energy capable of melting the small thin metal sheets P21 and P22 is generated to increase the heat input to the small thin metal sheets P21 and P22. , P22 is melted. At the time of the base current, by flowing a base current whose current value is significantly lower than the peak current, the arc energy is suppressed while maintaining the arc generation, and the heat input to the small thin metal sheets P21, P22 is reduced. The small thin metal sheets P21 and P22 melted at the peak current are solidified. By repeating the melting of the small thin metal sheets P21 and P22 at the peak current and the solidification of the molten metal at the base current as described above, the total heat input to the small thin metal sheets P21 and P22 is reduced, and the small thin metal sheets P21 and P22 are reduced. The small thin metal sheet P22 can be welded to the small thin metal sheet P21 by using TIG welding which is a kind of arc welding while preventing the metal sheet P21 from breaking.

In the second welding step, the pulse current has a peak current value I _P of 200 A or more and 250 A or less and a base current value I _B of 20 A or more and 40 A or less. By setting the peak current value I _P and the base current value I _B in the above ranges, the small thin metal sheet P21 and the small thin metal sheet P22 are melted at the peak current, and the small thin metal sheet P21 and the small size are melted at the base current. The operation of solidifying the thin metal sheet P22 can be reliably performed.

In the second welding step, the ratio of the peak current time T _P per one cycle of the pulse current to the pulse cycle T _C of the pulse current is 20% or more and 30% or less. By setting the ratio of the peak current time T _{P in} the above range, the small thin metal sheet P21 and the small thin metal sheet P22 are melted at the peak current, and the small thin metal sheet P21 and the small thin metal sheet P22 are melted at the base current. It is possible to more reliably perform the operation of solidifying the.

In the second welding step, the peak current value I _P , the peak current time T _P per cycle of the pulse current, and the peak current per second obtained by the product of the pulse frequency f of the pulse current The applied current amount S is 68 A or more and 72 A or less, the welding speed of pulse TIG welding is 36 cm/min or more and 65 cm/min or less, and the average welding voltage of pulse TIG welding is 10.5 V or more and 12.2 V or less. By adjusting the input current amount S at the peak current per second, the average welding voltage, and the welding speed within the above ranges, the heat input amount to the small thin metal sheet P21 and the small thin metal sheet P22 at the peak current is adjusted. The small thin metal sheet P21 and the small thin metal sheet P22 can be melted while preventing the small thin metal sheet P21 and the small thin metal sheet P22 from breaking at the peak current.

In the second welding process, the pulse frequency f of the pulse current is 8 Hz or more and 12 Hz or less. By setting the pulse frequency f in the above range, the small thin metal sheet P21 and the small thin metal sheet P22 are melted at the peak current, and the small thin metal sheet P21 and the small thin metal sheet P22 melted at the base current are solidified. It is possible to reliably perform the operation of.

In the second welding step, the wire feeding speed for supplying the welding wire is 1.2 m/min or more and 2.5 m/min or less, and the current value of the hot wire current flowing through the welding wire is 30 A or more and 45 A or less. .. By setting the wire feeding speed in the above range, the amount of welding wire W to be used can be suppressed, and the surplus of the welded portion between the small thin metal sheet P21 and the small thin metal sheet P22 can be made sufficiently large so that the yield strength of the welded portion can be increased. Can be secured. Further, by setting the wire feeding speed and the hot wire current value within the above ranges, the temperature of the welding wire W immediately before being supplied to the molten portion of the small thin metal sheet P21 and the small thin metal sheet P22 is directly below the melting point. The welding wire W can be heated.

A gas containing hydrogen is used as the shield gas. Hydrogen promotes an endothermic reaction in an arc atmosphere and absorbs arc energy. Therefore, by using a gas containing hydrogen as the shield gas, the heat input to the small thin metal sheets P21, P22 can be reduced and the small thin metal sheets P21, P22 can be more effectively prevented from breaking.

In the first welding step, the base material P1 and the small thin metal sheet P21 are resistance spot welded before the pulse TIG welding. The heat input to the small thin metal sheet P21 at the time of pulse TIG welding is released to the base material P1 via the resistance spot welding portion, whereby the small thin metal sheet P21 can be more reliably prevented from breaking.

The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications can be considered within the technical scope thereof.

For example, when the thin metal sheet P2 (small thin metal sheet P21) having the same shape as the substrate P1 in a plan view is used, the second welding step and the third welding step may be omitted.

Welding other than TIG welding may be used for temporary attachment of the small thin metal sheet P21 onto the base material P1 and temporary attachment of the small thin metal sheet P22 onto the small thin metal sheet P21 and the base material P1. Further, the installation intervals of the tack welded portions W1 and W3 are not limited to the above.

In the embodiment described above, a plurality of end portions of the small thin metal sheet P21 are fixed to the base material P1 by resistance spot welding. However, resistance spot welding may be omitted.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiments with known constituent elements within the scope of the present invention, and the above-described modified examples may be combined as appropriate.

P1... Thick metal base material P2... Thin metal sheet P21... Small thin metal sheet (first thin metal sheet) P22... Small thin metal sheet (second thin metal sheet) W... Welding wire

Claims (17)

A first welding step of welding a stainless steel first thin metal sheet having a thickness of 0.1 mm or more and 1.0 mm or less to the surface of a carbon steel thick metal base material;
A method for welding a thin metal sheet to a surface of a thick metal substrate, wherein in the first welding step, a hot wire is used as a welding wire, and pulse TIG welding is performed using a pulse current as a welding current. In the first welding step, the pulse current has a peak current value of 200 A or more and 250 A or less and a base current value of 20 A or more and 40 A or less, to the surface of the thick metal base material according to claim 1. Welding method for thin metal sheets. The thickness according to claim 2, wherein in the first welding step, a ratio of a peak current time per cycle of the pulse current to a pulse cycle of the pulse current is 40% or more and 60% or less. A method for welding a thin metal sheet to a surface of a metal substrate. In the first welding step,
The peak current input current amount per second obtained by the product of the peak current value of the pulse current, the time of the peak current per cycle of the pulse current, and the pulse frequency of the pulse current is 115 A or more. 120A or less,
The welding speed of the pulse TIG welding is 35 cm/min or more and 60 cm/min or less,
An average welding voltage of the pulse TIG welding is 11.5 V or more and 13.7 V or less, The method of welding a thin metal sheet to a surface of a thick metal substrate according to claim 1, wherein .. In the first welding step, the pulse frequency of the pulse current is 8 Hz or higher and 12 Hz or lower, and the welding of the thin metal sheet to the surface of the thick metal base material according to any one of claims 1 to 4 is performed. Method. In the first welding step, the wire feeding speed for supplying the welding wire is 1.5 m/min or more and 2.6 m/min or less, and the current value of the hot wire current flowing in the welding wire is 30 A or more and 45 A or less. The method for welding a thin metal sheet to a surface of a thick metal substrate according to any one of claims 1 to 5, wherein In the first welding step, a gas containing hydrogen is used as a shielding gas, and the method for welding a thin metal sheet to the surface of a thick metal substrate according to any one of claims 1 to 6, wherein. After the first welding step, further comprising a second welding step of welding a second thin metal sheet made of stainless steel having a thickness of 0.1 mm or more and 1.0 mm or less to the first thin metal sheet,
In the said 2nd welding process, while using a hot wire as a welding wire, pulse TIG welding which uses a pulse current as a welding current is performed, The thick metal base as described in any one of Claims 1-7 characterized by the above-mentioned. Welding method for thin metal sheet on material surface. In the second welding step, the pulse current has a peak current value of 200 A or more and 250 A or less, and a base current value of 20 A or more and 40 A or less, to the surface of the thick metal substrate according to claim 8. Welding method for thin metal sheets. 10. The thickness according to claim 9, wherein in the second welding step, the ratio of the peak current time per cycle of the pulse current to the pulse cycle of the pulse current is 20% or more and 30% or less. A method for welding a thin metal sheet to a surface of a metal substrate. In the second welding step,
The peak current input current amount per second obtained by the product of the peak current value of the pulse current, the peak current time per cycle of the pulse current, and the pulse frequency of the pulse current is 68 A or more. 72A or less,
The welding speed of the pulse TIG welding is 36 cm/min or more and 65 cm/min or less,
The welding method of a thin metal sheet onto a surface of a thick metal substrate according to any one of claims 8 to 10, wherein the average welding voltage of the pulse TIG welding is 10.5 V or more and 12.2 V or less. .. In the second welding step, the pulse frequency of the pulse current is 8 Hz or more and 12 Hz or less, and the welding of the thin metal sheet to the surface of the thick metal substrate according to any one of claims 8 to 11. Method. In the second welding step, the wire feed rate for supplying the welding wire is 1.2 m/min or more and 2.5 m/min or less, and the current value of the hot wire current flowing in the welding wire is 30 A or more and 45 A or less. The method for welding a thin metal sheet to a surface of a thick metal substrate according to any one of claims 8 to 12, characterized in that there is. The method of welding a thin metal sheet to a surface of a thick metal substrate according to claim 8, wherein a gas containing hydrogen is used as a shielding gas in the second welding step. The said 1st welding process WHEREIN: Before the said pulse TIG welding, the said thick metal base material and the said 1st thin metal sheet are resistance spot welded, It is characterized by the above-mentioned. A method for welding a thin metal sheet to the surface of a thick metal substrate as described above. The method for welding a thin metal sheet to a surface of a thick metal substrate according to any one of claims 1 to 15, wherein the thick metal substrate has a flat plate shape. In the first welding step, the first thin metal sheet is arranged on the thick metal substrate, and at least one of the thick metal substrate and the first thin metal sheet, or the thick metal substrate. A rail is disposed around the rail, and a welding device is moved on the rail to automatically perform pulse TIG welding between the thick metal base material and the first thin metal sheet. 17. A method for welding a thin metal sheet to the surface of a thick metal substrate according to any one of 16 above.

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