JP2000343270A - Method and device for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce tensile residual stress by simple constitution by utilizing thermal shock strain. SOLUTION: By rapidly cooling a surface region whose temperature is raised by heat input of welding by jetting a coolant from a nozzle 11 to a region of the surface of a weld zone which is in the state of tensile stress, transient temperature difference is generated between the surface and a layer just under a surface layer. In this way, the tensile thermal shock stress is added on the surface layer, tensile strain is generated and also the surface layer is partially yielded. Next, by stopping cooling and raising the temperature, the thermal shock stress is eliminated. The surface of the weld zone is improved into a state where deformation is elastically recovered from the partially yield state and tensile stress is mitigated, or a compressive residual stress state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method for reducing the residual tensile stress on the surface of a metal, and more particularly to a welding method and apparatus suitable for reducing the residual tensile stress on the surface of a weld. is there.

[0002]

2. Description of the Related Art Generally, when a metal material such as austenitic stainless steel used for an internal structure of a reactor pressure vessel is placed in high-temperature water of a nuclear reactor, stress corrosion cracking occurs at or near a welded portion thereof. It has been known.
Stress corrosion cracking occurs under a condition in which three factors such as material sensitization, tensile residual stress, and corrosive environment are superimposed. The sensitization of the material is caused by the precipitation of Cr carbide at the crystal grain boundaries due to welding heat, etc., resulting in the formation of a Cr-depleted layer in the immediate vicinity of the grain boundaries, and the Cr-depleted portions near the grain boundaries become sensitive to corrosion. Get up. Tensile stress is generated by superimposing a stress due to external force and a tensile residual stress generated on a material surface by welding and processing. A corrosive environment is created by hot water containing dissolved oxygen. Stress corrosion cracking is one of these three factors.
Can be prevented by removing two factors. In order to prevent the stress corrosion cracking, there are, for example, the following known examples of known techniques for improving the residual stress on the material surface that causes the generation of tensile stress.

Japanese Patent Application Laid-Open No. Sho 53-21021 discloses a known technique in which a coil is provided on the outer periphery of an austenitic stainless steel pipe, which is heated and then cooled by jetting cooling water onto the inner surface of the pipe to thereby rapidly pull the inner surface of the pipe. It converts residual stress into compressive residual stress.

[0004]

However, the above-mentioned prior art is difficult to apply to large structures and plate materials because the piping is an application object and a heating coil is wound around the outer periphery of the object. Was.

A first object of the present invention is to provide a welding method capable of reducing the residual tensile stress in a welded portion with a simple structure by utilizing thermal shock strain, and a second object of the present invention is to provide a welding method. It is to provide an apparatus suitable for implementing the method.

[0006]

According to the present invention, in order to achieve the first object, a first procedure for cooling a surface region heated by the heat input of welding, and a second procedure for stopping the cooling. And a welding method.

Preferably, in the welding method,
The first procedure is a procedure in which a low-temperature coolant is jetted from a nozzle to a heated surface area to cool an area where the coolant is in contact, and the second procedure is to cool the surface area. A procedure for stopping the application of the material.

[0008] More preferably, in the welding method, the second step is a step of moving the area where the coolant contacts, so as to apply the area to another heated surface area of the welded part surface. A welding method is provided.

[0009] More preferably, in the above-mentioned welding method, the second step is a step of stopping the ejection of the coolant from the nozzle.

Preferably, in the above-mentioned welding method, the first step includes arranging a plurality of nozzles in a row to form a row of a coolant in a curtain shape, and passing the row of the coolant along a path through which a welding electrode has passed. A welding method is provided, wherein the welding method is a procedure for applying the welding along.

[0011] Preferably, in the above welding method, there is provided a welding method characterized in that the coolant is sprayed in a mist state by a nozzle for spraying the coolant in a mist state.

Preferably, in the above-mentioned welding method, the coolant jetted from the nozzle is pressurized by pressurizing means.

[0013] More preferably, in the above welding method, there is provided a welding method characterized in that a coolant jetted from a nozzle is cooled by cooling means.

[0014] More preferably, in the above welding method, the periphery of the welding path is covered with a heat insulating material, and the first step is characterized in that the periphery of the welding path is covered with a heat insulating material and then a coolant is sprayed. A welding method is provided.

Preferably, in the above welding method, a shielding gas is injected in a curtain shape between a position of a welding electrode and a position of a region where a mist-like coolant is applied. You.

More preferably, in the above-mentioned welding method, there is provided a welding method, wherein a shield is provided between a position of a welding electrode and a position of a region where a mist-like coolant is applied.

Preferably, in the above welding method, a welding method is provided, wherein water is used as a coolant.

More preferably, in the above welding method, the coolant is water and the average flow rate is 40 ml / min.
A welding method characterized by being pressurized so as to be at least 800 ml or less.

More preferably, in the above welding method, the coolant is water and the average flow rate is 40 ml / min.
The welding method is characterized by being pressurized so as to be 80 ml or less.

Preferably, in the above welding method, when the steel material to be welded is carbon steel or low alloy steel, cooling is started when the temperature of the heated surface region is 600 ° C. or more. Is provided.

Preferably, in the above welding method, when the steel material to be welded is stainless steel, cooling is started when the temperature of the heated surface region is 800 ° C. or more. .

In order to achieve the second object of the present invention, a welding apparatus, a low-temperature gas and a container for storing the same, a gas pressurizing means, a means for transporting a gas to a welding electrode, and a gas blowout And a welding device equipped with the nozzle.

.. Generally, the reactor pressure vessel structure includes:
A tensile residual stress close to the yield stress often exists from the beginning due to machining or welding. In the present invention, by cooling the surface area in the first step with respect to the area of the welded part surface in the tensile stress state, only the surface layer that is hit by the water flow in this area has a low temperature, and the area just below the surface layer is reduced. Meanwhile, a transient temperature difference ΔT occurs. Therefore, a tensile thermal shock stress is applied to the surface layer to generate tensile strain, and the surface layer partially yields. Then, when the cooling is stopped and the temperature is raised in the second procedure, the temperature difference ΔT disappears and the thermal shock stress disappears, so that the surface of the welded portion is elastically deformed from a partially yielded state and the tensile stress is reduced. Is reduced to a relaxed state or a compressive residual stress state.

Further, a low-temperature coolant is ejected from the nozzle to the surface region heated in the first procedure to cool the region where the coolant is in contact, thereby enabling rapid cooling to a predetermined temperature. By stopping the application of the coolant to the surface area in the second procedure, it is possible to stop the rapid cooling when the temperature reaches a predetermined temperature.

In the second procedure, the nozzle is moved while jetting low-temperature water, and is applied to another heated surface area of the surface of the welded portion, so that the jet of low-temperature water from the nozzle is not stopped. A second procedure for stopping the application of the low-temperature water to the surface region can be realized.

Further, by stopping the jetting of the low-temperature water from the nozzle in the second procedure, the second procedure of stopping the application of the low-temperature water to the surface area without moving the nozzle can be realized.

Further, in the first procedure, a plurality of nozzles are arranged in a line to form a curtain-shaped row of water drops, the row of water drops is applied along the path through which the welding electrode has passed, and
By moving the area where the row of the water droplets hits, it is possible to realize that the cooling of the surface of the welded portion is maintained for a certain period of time by moving it to another heated surface area of the surface of the welded portion.

Further, by spraying the low-temperature water in the form of mist by means of the above-mentioned nozzle for spraying the low-temperature water in the form of mist, it is possible to suppress the diffusion of the low-temperature water to the surroundings during the welding operation and to improve the workability. .

The low-temperature water jetted from the nozzle is pressurized by the pressurizing means, so that the low-temperature water jetted from the nozzle in the surface region of the welded portion where the temperature has risen causes film boiling and cooling. It is possible to prevent a decrease in efficiency.

Further, by cooling the low-temperature water jetted from the nozzle by the cooling means, in addition to the latent heat of vaporization in the heated surface region of the surface of the weld, the heat required to raise the temperature from low temperature to the boiling point is obtained. Can be absorbed, and local quenching can be realized.

Further, the periphery of the welding path is covered with a heat insulating material,
By limiting the area to which the low-temperature water spouted from the nozzle is applied, local rapid cooling can be realized in the heated surface area of the welded part surface.

Further, by injecting a shielding gas in a curtain shape between the position of the welding electrode and the position of the region where the mist-like coolant is applied, it is possible to prevent the coolant from being caught in the electrode. it can.

Further, by providing a shield between the position of the welding electrode and the position of the region where the mist-like coolant is applied,
It is possible to reduce the frequency at which the coolant is caught in the welding electrode.

Further, by using water as the coolant, it is possible to prepare the coolant inexpensively.

Further, since the coolant is water and is pressurized so that the average flow rate is 40 ml or more and 800 ml or less per minute, a sufficient cooling effect can be exhibited.

Further, the average flow rate is 40 ml / min.
By being pressurized so as to be equal to or less than ml, it is possible to reduce excess water scattered around the welding while maintaining a sufficient cooling function.

When the material to be welded is carbon steel or low alloy steel, cooling is started at a stage where the temperature of the heated surface region is 600 ° C. or higher, whereby the effect of quenching can be generated. .

Further, when the material to be welded is stainless steel,
By starting the cooling at the stage where the temperature of the heated surface region is 800 ° C. or more, it is possible to reduce the sensitivity of the surface region.

The invention of the apparatus includes a welding electrode, a drive mechanism for the welding electrode, a nozzle for injecting low-temperature water, a cooling means for low-temperature water, a means for pressurizing low-temperature water, and a shielding gas around the low-temperature water. The effect of generating thermal shock stress can be obtained by means for spraying the material in a curtain shape and means for covering a region sandwiching the position where the welding path passes with a heat insulating material.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, an embodiment for illustrating the principle of the present invention will be described with reference to FIG. FIG. 2 shows a grooved steel material 2
No. 1 was butt-welded. The cross section immediately after the electrode for laminating the final pass 23 has been passed after performing the welding of a plurality of passes is shown. Assuming that the welding target is austenitic stainless steel, with a heat input of about 30 kJ / cm, the temperature of the final pass rises to 800 ° C or more. When a time interval of 50 seconds is passed after the welding electrode passes through the cross section, the cross section has a substantially uniform temperature distribution at about 300 ° C. At a time interval of 50 seconds after the passage of the welding electrode, a water stream is ejected from the nozzle 11 to make the cross-section have a substantially uniform temperature distribution and hit the surface. Here, the water jetted from the nozzle 11 is cooled by the cooling means 32 and is further pressurized by the high-pressure pump 31. After 30 seconds, stop the water from the nozzle. FIG. 3 shows a transient temperature distribution in the plate thickness direction in this process. Immediately before the water flow hits, there is no temperature distribution in the plate thickness direction as shown by the straight line a. When a water stream hits the surface, the surface is cooled and the temperature drops, and the temperature distribution in the plate thickness direction becomes the distribution shown by the curve b. By stopping the flow of the water flow, the temperature distribution in the plate thickness direction becomes d via the curve c.

Next, the action of the present embodiment for improving the residual stress is shown in FIG.
This will be described with reference to FIG. FIG. 4 is a stress σ-strain ε curve of a material. The stress on the vertical axis indicates tensile stress on the upper side and compressive stress on the lower side, and the strain on the horizontal axis indicates tensile strain in the right direction and compressive strain in the left direction. Generally, in welding, a tensile residual stress such as a yield stress is often present on the surface of a metal body. This initial state is represented by a point on the stress-strain curve of FIG. The surface of the welding area has a high temperature immediately after the end of welding, but a certain area to which the water flow from the nozzle is applied is subjected to a transient temperature between immediately below the surface layer by being rapidly cooled by the water flow as described above. Generates the difference ΔT. Then, tensile stress and tensile strain due to thermal shock are generated in this surface layer. At this time, the tensile strain Δε and the tensile stress Δσ are respectively

[0043]

Δ１ = {α × ΔT / (1-ν)} × F Δσ = E × Δε α: linear expansion coefficient ν: Poisson's ratio F: strain constraint factor E: longitudinal elastic modulus Here, in the case of welding of austenitic stainless steel, the coefficient of linear expansion α = 17 × 10 to 6, the Poisson's ratio ν = 0.3,
Assuming that the strain constraint factor F = 1 and E = 2 × 105 MPa, and ΔT is 200 ° C., the generated tensile strain Δε = 4.9 × 1
0 to 3, and the tensile stress Δσ = 980 MPa. At this time, if there is no initial residual stress due to processing etc. in the metal body, a thermal shock stress of about 980 MPa will be generated in the metal body as it is, but as described above, a tensile stress close to the yield stress already In this case, the stress does not increase so much because the surface layer partially yields while the strain of Δε is applied, that is, it moves from point to point in FIG. Thereafter, the quenched region is stopped from being exposed to the water flow, so that the temperature is raised by heat conduction from the surrounding high-temperature region, and the transiently generated temperature difference ΔT disappears. Therefore, the previously generated thermal shock stress disappears, and the collision region of the surface layer is elastically deformed by the elastic constraint from the partial yield state, and moves to the left in FIG. That is, in the method for improving residual stress according to the present embodiment, the initial residual tensile stress state can be reduced to the compressive residual stress according to the above principle. Even if the temperature of the water droplet to be sprayed is not very low, or if the transient temperature difference ΔT between the surface layer and immediately below the surface layer is relatively low, the points in FIG. From the point, which is the initial tensile residual stress, to the state of lower tensile stress.

FIG. 5 shows a transient change in the stress distribution in the plate thickness direction when a water flow is ejected from the nozzle and applied to the surface without leaving a time interval after the welding electrode passes through the cross section.
Shown in Also in this case, a temperature difference ΔT can be generated between the surface region and the region immediately below the surface layer, and therefore, the state where the initial tensile residual stress is large can be improved to a state where the tensile stress is small.

Next, an embodiment of the present invention based on the above principle will be described with reference to FIGS. This embodiment uses an automatic TIG
When welding is performed by a welding machine, the residual stress is improved based on the above principle. In this embodiment, a rail guide 44 is provided on a guide rail 43 for guiding a welding device.
A moving module is provided via a driving motor 41. The moving speed of the drive motor 41 is controlled by the electrode movement control means 36. An example of the electrode movement control means 36 is a personal computer equipped with a dedicated processing unit for controlling the number of rotations of the drive motor. From the moving module, the welding electrode 1 and the cooling water jet nozzle 11
Are provided via support members 45, respectively.

As shown in detail in FIG.
A tungsten electrode 1, an inert gas nozzle 3, and a welding wire supply mechanism 6 are provided. A current and a voltage corresponding to welding conditions are supplied to the tungsten electrode 1 from a welding power source 7. From the inert gas nozzle 3, an inert gas such as argon is jetted from an inert gas supply means 34 such as a gas cylinder. From the welding wire supply mechanism 6, the welding wire 2 is supplied by the wire supply control means at a feed rate corresponding to the welding conditions. The process of placing a welding path is performed by the above mechanism.

The cooling water jetting nozzle 11 is provided from the moving module via a support member 45. The cooling water jet nozzle 11 is provided behind the electrode 1 with respect to the traveling direction of the moving module. Cooling water is supplied to the cooling water jet nozzle 11 by a cooling water supply means 30 via a conduit, and is applied to a welding path or a region around the welding path heated by welding heat input. In this way, the moving module travels on the drive rail 43 while applying the jet of the water flow to the high-temperature region after the welding heat input.

According to the present embodiment, the cooling water jet nozzle 11
The area from which the water flow hits is quenched because the water flow from the water flow is applied. The quenching applies a thermal shock stress to generate tensile strain and partially yield the surface layer. Thereafter, the nozzle 11 is moved and the water flow does not hit the partially yielded area, and the temperature difference becomes the same as the surrounding area, so that the thermal shock stress disappears. Therefore, the deformation is not elastic and the tensile stress is relaxed. It can be a residual stress distribution in a state where a compression stress is generated or in a state where the compression stress is generated.

In the above embodiment, the temperature of the water jetted from the cooling water jetting nozzle 11 was set to 20 ° C. However, the lower the temperature of the water, the quicker the surface area can be cooled. Since a sufficient effect of reduction can be expected,
The temperature of water is preferably about 0 to 10 ° C. As a means for cooling water, a method in which ice is put in a supply container and cooled to 0 ° C. by the latent heat of melting of ice is mentioned as an easy means.

In the above embodiment, the water jetted from the cooling water jet nozzle 11 boils and evaporates in the heated surface area. The surface area is rapidly cooled by the amount of heat for raising the temperature from the initial temperature to the boiling point and the latent heat of evaporation. Therefore, when the flow rate of the water flow ejected from the nozzle is sufficiently larger than the amount that evaporates, a stress reduction effect can be expected. In addition, when the flow rate is sufficiently high, it is possible to avoid a state in which water is in a film boiling state in the surface region and the surface region cannot be sufficiently cooled.

In order to secure a flow rate for sufficiently performing the above-mentioned surface cooling, the amount of water jetted from the nozzle is increased by the pressurizing means 31 so as to be 40 ml or more and 800 ml or less per minute. Is desirable.

Further, in order to maintain a sufficient quenching capacity and minimize the amount of cooling water scattered to the surroundings, the pressure from the nozzle 11 is increased by 40% to 80 ml per minute by the pressure means 31. It is desirable to squirt.

After the heat input of the welding, when the quenching is started by applying the water jet spouting from the nozzle 11, when the material to be welded is stainless steel,
When quenching is started at 800 ° C. or more, sensitization can be reduced. When the material to be welded is a low alloy steel or a carbon steel, the surface region can be hardened when the surface region starts quenching at 600 ° C. or higher.

In the above embodiment, the water stream is jetted from the nozzle 11 to cool it. However, the water jet is jetted in the form of a mist using the nozzle 17 shown in FIG. Is also good. By spraying in the form of a mist and hitting the surface area, it becomes possible to reduce the amount of water scattered to the surroundings and to perform rapid cooling as compared with the case where a water flow is used.

FIG. 8 shows a modification of the above embodiment. In the present embodiment, the nozzles ejected in the form of a mist are arranged in a line to form a curtain, and the nozzle is cooled against the heated surface area. The area to which the cooling water is applied becomes longer along the traveling direction, so that even when the speed of the moving module is constant, the cooling water can be applied to the section to be quenched for a long time.

In the above-described modified embodiment, the nozzles 17 ejected in the form of a mist are arranged in a line and are moved together with the moving module, while being rapidly cooled by being ejected in the form of a mist ejected from the nozzles 17, but the welding path is increased. If the length is short, perform welding first, then apply a mist of water to the heated surface area after stopping the transfer module,
Thereafter, the effect of reducing the residual tensile stress can be expected by stopping the mist-like water flow.

In the above-described embodiment and its modified embodiments, water used for quenching may scatter to the welding electrode or the molten pool immediately below the electrode and be involved therein. An embodiment in which this is prevented will be described with reference to FIGS. 9 and 10. FIG. A shield 19 is provided between the welding electrode 1 and the nozzle 17 for jetting cooling water, and a shielding gas is arranged in a line in a direction perpendicular to a straight line connecting the welding electrode and the nozzle to form a curtain-shaped flow. Thus, the scattered cooling water flow and water droplets can be kept away from the electrode. It is most desirable to use both the installation of the shield and the curtain-like flow of the shielding gas, but the effect can be expected even if each is used alone. It is an easy method to use a stainless thin plate having a thickness of 0.1 mm as an example of the shield. It is an easy method to use pressurized air to form a curtain-like flow.

In the above embodiment, thermal shock stress is generated on the surface by applying a water flow or a mist-like water flow to the surface region heated by the welding heat input, thereby reducing the tensile residual stress. By limiting the region to be cooled, an effect of efficiently generating thermal shock stress can be expected. In order to limit the area to be cooled, a predetermined effect can be achieved by performing welding heat input after covering the periphery of the welding path with a heat insulating material and then rapidly cooling.

[0059]

According to the first aspect of the present invention, the following effects can be obtained. That is, in the first procedure, since cooling is performed on the area of the welded portion surface in the residual state of the tensile stress, tensile thermal shock stress is applied to the surface layer to generate tensile strain and the surface layer partially yields . Then, in the second step, cooling is completed and the temperature is increased by heat conduction from the surroundings,
The thermal shock stress disappears, and the surface layer in the quenched region is elastically deformed from a partially yielded state, and is improved to a state where the tensile stress is relaxed or a state of the compressive residual stress.

According to the second aspect of the present invention, a low-temperature coolant is jetted from the nozzle to the surface area heated in the first procedure, and the area where the coolant is hit is cooled to a predetermined temperature. Rapid cooling becomes possible. By stopping the application of the coolant to the surface area in the second procedure, it is possible to stop the rapid cooling when the temperature reaches a predetermined temperature.

According to the third aspect of the present invention, the nozzle is moved while jetting the low-temperature water in the second procedure, and is applied to another heated surface region of the surface of the welded portion. A second procedure for stopping the application of the low-temperature water to the surface region without stopping the ejection of the water can be realized. In addition, since the work can be continuously performed, the work can be performed in a short time.

According to the fourth aspect of the present invention, the step of stopping the jetting of the low-temperature water from the nozzle in the second step to stop the application of the low-temperature water to the surface area without moving the nozzle. Can be easily realized.

According to the fifth aspect of the present invention, a plurality of nozzles are arranged in a row in the first procedure to form a row of curtain-shaped water droplets, and the row of water drops is applied along the path through which the welding electrode has passed. And the second procedure realizes maintaining the cooling of the welded part surface for a certain period of time by moving the area where the row of the water droplets hits and hitting it to another heated surface area of the welded part surface. it can.

According to the invention of claim 6, by spraying the low-temperature water in the form of a mist by spraying the low-temperature water in the form of a mist, the scattering of the low-temperature water to the surroundings during the welding operation is suppressed.
Workability can be improved.

According to the seventh aspect of the present invention, the low-temperature water jetted from the nozzle is pressurized by the pressurizing means, so that the low-temperature water jetted from the nozzle in the surface region where the temperature of the welded portion is increased. According to the invention of claim 8, it is possible to prevent a decrease in cooling efficiency by causing film boiling, thereby cooling the low-temperature water jetted from the nozzle by the cooling means, thereby increasing the temperature of the surface of the welded portion. In addition to the latent heat of vaporization, the heat required for the temperature rise from a low temperature to the boiling point can be absorbed in the surface region thus set, and local rapid cooling can be realized.

According to the ninth aspect of the invention, the periphery of the welding path is covered with a heat insulating material, and the area to which the low-temperature water spouted from the nozzle is applied is limited, so that the surface of the welding portion is locally heated at the heated surface area. According to the invention of claim 10, which can realize rapid cooling, the coolant is injected in a curtain shape between the position of the welding electrode and the position of the region to which the mist-like coolant is applied, so that the coolant can be cooled. Can be prevented from being caught in the device. It is possible to prevent deterioration of welding quality such as hydrogen cracking.

According to the eleventh aspect of the present invention, by providing a shield between the position of the welding electrode and the position of the region where the mist-like coolant is applied, the frequency with which the coolant is caught in the welding electrode is reduced. Can be realized. Claim 10
By using in combination with the invention of the above, it is possible to prevent the deterioration of the quality of the welded portion.

According to the twelfth aspect of the invention, the use of water as the coolant makes it possible to prepare the coolant at low cost. According to the thirteenth aspect of the invention, the coolant is water, By being pressurized so that the average flow rate is 40 ml or more and 800 ml or less per minute, a sufficient cooling effect can be exhibited.

According to the fourteenth aspect of the present invention, the welding is performed while maintaining a sufficient cooling function by being pressurized so that the average flow rate is 40 ml or more and 80 ml or less per minute. According to the invention of claim 15, it is possible to reduce excess water scattered to the surroundings, and when the material to be welded is carbon steel or low alloy steel, the temperature of the heated surface region is 600 ° C. or more. By starting the cooling at, the effect of quenching can be generated.

According to the sixteenth aspect of the present invention, when the material to be welded is stainless steel, the temperature of the heated surface region is 800 ° C.
By starting the cooling at the above stage, it becomes possible to reduce the sensitization of the surface region.

According to the seventeenth aspect of the present invention, the invention of the apparatus includes a welding electrode, a driving mechanism of the welding electrode, a nozzle for injecting low-temperature water, a cooling means for low-temperature water, and a means for pressurizing the low-temperature water. In addition, the effect of generating thermal shock stress can be obtained by means for spraying the shielding gas around the low-temperature water in a curtain shape and means for covering the region sandwiching the position where the welding path passes with the heat insulating material.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment illustrating the principle of the present invention.

FIG. 2 is a sectional view illustrating the principle of a cooling method according to an embodiment illustrating the principle of the present invention.

FIG. 3 is a cross-sectional view showing a transitional temperature distribution when a cross section having a uniform temperature distribution in a sheet thickness direction is cooled by a cooling method according to an embodiment illustrating the principle of the present invention.

FIG. 4 is a stress-strain curve diagram of the steel material shown in FIG.

FIG. 5 is a cross-sectional view showing a transitional temperature distribution when cooling is performed at a stage where a temperature distribution is generated in a sheet thickness direction by a cooling method according to an embodiment illustrating the principle of the present invention.

FIG. 6 is a configuration diagram of a welding method according to an embodiment of the present invention.

FIG. 7 is a view showing a nozzle for spraying cooling water in a mist state according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a cooling method using a plurality of nozzles that spray in a mist state according to an embodiment of the present invention.

FIG. 9 is a diagram illustrating a shielding method for preventing cooling water from being involved in a welding electrode according to an embodiment of the present invention.

FIG. 10 is a view showing a shielding gas nozzle and a shielding plate for preventing cooling water from being involved in a welding electrode according to an embodiment of the present invention.

[Explanation of symbols]

1 welding electrode, 2 welding wire, 3 inert gas nozzle, 4 inert gas conduit, 5 conducting wire, 6 welding wire supply device, 7 welding power source, 11 nozzle, 12 coolant channel, 13: nozzle cap for fog spraying, 14: nozzle hole,
15 ... Inner nozzle hole, 16 ... Rubber packing, 17 ... Mist spray nozzle, 18 ... Pressurized air nozzle, 19 ... Shield plate,
21 ... steel material, 22 ... weld metal, 23 ... final pass, 30 ...
Cooling water supply means, 31: cooling water pressurizing device, 32, water cooling means, 33, water supply means, 34, inert gas supply means,
35: wire supply control means, 36: electrode movement control means,
37: temperature measuring device, 38: temperature sensor, 39: pressurized air supply means, 41: driving device, 42: guide, 43: rail, 44: both ends guide, 45: support material.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 103: 04 (72) Inventor Kunio Enomoto 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi Engineering Consulting, Ltd. (72) Inventor Toshio Ishizuki 3-2-1 Sachimachi, Hitachi-shi, Ibaraki Prefecture Within Hitachi Engineering Co., Ltd. (72) Inventor Sadato Shimizu 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Stock Hitachi Hitachi, Ltd. Hitachi Plant (72) Inventor Satoshi Kanno 502, Kandachi-cho, Tsuchiura-shi, Ibaraki F-term in Machinery Research Laboratory, Hitachi, Ltd.

Claims (17)

[Claims] 1. A welding method comprising: a first procedure for cooling a surface region heated by the heat input of welding; and a second procedure for stopping cooling. 2. The welding method according to claim 1, wherein the first step is a step in which a low-temperature coolant is jetted from a nozzle to a surface region where the temperature is raised to cool a region where the coolant is in contact. And a second step of stopping the application of the coolant to the surface area. 3. The welding method according to claim 2, wherein the second step is to move a region where the coolant is applied, so that the region is brought into contact with another heated surface region of the surface of the welded portion. A welding method, characterized in that: 4. The welding method according to claim 2, wherein the second step is a step of stopping the ejection of the coolant from the nozzle. 5. The welding method according to claim 2, wherein the first step includes arranging a plurality of nozzles in a row to form a curtain-shaped coolant row, and A welding method characterized by a procedure in which a row is applied along a path through which a welding electrode has passed. 6. The welding method according to claim 1, wherein the coolant is applied in a mist state by a nozzle that ejects the coolant in a mist state. 7. The welding method according to claim 1, wherein the coolant ejected from the nozzle is pressurized by pressurizing means. 8. The welding method according to claim 1, wherein the coolant ejected from the nozzle is cooled by cooling means. 9. The welding method according to claim 1, wherein the periphery of the welding path is covered with a heat insulating material, and the first step is to cover the periphery of the welding path with a heat insulating material. A welding method characterized in that a coolant is sprayed on the surface. 10. The welding method according to claim 1, wherein a shielding gas is injected in a curtain shape between a position of the welding electrode and a position of a region to which the mist-like coolant is applied. A welding method characterized by the following. 11. The welding method according to claim 1, wherein a shield is provided between a position of the welding electrode and a position of a region to which the mist-like coolant is applied. Welding method. 12. The welding method according to claim 1, wherein water is used as a coolant. 13. The welding method according to claim 7, wherein
A welding method, wherein the coolant is water and the coolant is pressurized so that the average flow rate is 40 ml or more and 800 ml or less per minute. 14. The welding method according to claim 7, wherein
A welding method, wherein the coolant is water and the coolant is pressurized so that the average flow rate is 40 ml or more and 80 ml or less per minute. 15. The welding method according to claim 1, wherein, when the steel material to be welded is carbon steel or low alloy steel, the cooling is started when the temperature of the heated surface region is 600 ° C. or more. Welding method characterized by performing. 16. The welding method according to claim 1, wherein when the steel material to be welded is stainless steel, the cooling is started when the temperature of the surface region where the temperature is raised is 800 ° C. or more. And welding method. 17. A welding electrode, a nozzle for ejecting a coolant, a means for supplying a coolant, a means for cooling the coolant, a means for pressurizing the coolant, and a direction for ejecting the coolant from the welding electrode. Welding equipment equipped with a nozzle that creates a gas flow.