JPH08118024A - Electrogas arc welding equipment of stainless steel - Google Patents

Abstract

PURPOSE: To enable solution heat treatment of a butt weld zone of stainless steel thick plate even for large structure. CONSTITUTION: A welding equipment is provided with a rear backing strip 2 fixed to the rear side of a groove space 1a formed in the vertical direction between two base materials to be welded for butt welding, a front backing strip 3 arranged at the front side of the groove space 1a and sliding upward, a nozzle 4 to melt a welding wire 5 arranged in the groove space 1a and an injection outlet arranged at the lower part of the front backing strip and an injecting port injecting a cooling water 7 to the surface of the weld metal 6 which is solidified after the front backing strip 3 is passed. By this method, the weld metal 6 in high temp. right after welding is rapidly cooled by the cooling water 7 injected so as to prevent the weld zone between two base materials 1 to be welded from sensitization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel electrogas arc welding apparatus applied to welding stainless steel thick plate materials such as large structures and gas tanks.

[0002]

2. Description of the Related Art When a stainless steel thick plate is welded with a large heat input and the weld heat affected zone is gradually cooled, a sensitized region is generated there, which causes corrosion or stress corrosion cracking during use. To be damaged.

Therefore, in the conventional electrogas arc welding of stainless steel, the heat treatment for solution heat treatment has been performed after the welding. The sensitized region is more likely to occur when stainless steel is heated to 500 to 900 ° C. and the holding time is longer.

[0004]

In conventional electrogas arc welding, when austenitic stainless steel (particularly 18-8 stainless steel such as SUS304 and SUS316) is welded with a large heat input, as described above, the vicinity of the welded portion is A sensitized area in the weld heat affected zone (a situation in which the carbide is precipitated in the crystal grain boundaries of the metal due to the heat influence and the Cr concentration around it is reduced, making it susceptible to corrosion and stress corrosion cracking) Corrosion and stress corrosion cracking occur during use as an object, damaging the structure.

Therefore, the heat treatment for heat treatment is usually performed after welding, but in the case of a large structure, it is difficult to heat-treat the whole structure, and if it is partially heat-treated, a sensitized region may occur around it. The present invention is intended to solve the above problems.

[0006]

SUMMARY OF THE INVENTION A stainless steel electrogas arc welding apparatus of the present invention is a back fixed to a back side of a vertical groove space formed by abutting two stainless steel base materials to be welded. Metal plate, a metal plate provided on the front side of the groove space and sliding upward, a nozzle provided in the groove space for introducing and melting a welding wire into the space, and a metal plate provided below the metal plate An injection outlet for directly injecting cooling water is provided on the surface of the weld metal formed by solidifying the molten metal.

[0007]

In the above, in the groove space between the front and back plates, which slide upward, the welding wire is melted by the arc discharge formed by the nozzle to generate molten metal. Fill the space.

Since the molten metal is cooled by the front metal plate and the back metal plate, after the front metal plate has passed, the above-mentioned 2
Solidified weld metal is formed between the base materials to be welded, and cooling water is jetted from the jet outlet provided in the lower portion of the front cover metal to the surface of the weld metal.

Therefore, the weld metal immediately after welding in a high temperature state is rapidly cooled by the cooling water directly injected,
In the welded portion between the two base materials to be welded, formation of a sensitized region is prevented.

[0010]

1 and 2 show a welding apparatus according to an embodiment of the present invention. The present embodiment shown in FIGS. 1 and 2 is a water-cooled copper backing plate fixed to the back side of a groove space 1a in the vertical direction formed by abutting two base materials 1 to be welded, which are thick stainless steel plates. 2, a water-cooled copper front cover plate 3 provided on the front side of the groove space 1a and slid upward by a driving device (not shown), a nozzle 4 for introducing a welding wire 5 into the groove space 1a, and the water-cooled copper surface An injection outlet 12 is provided on the lower surface of the pad 3 for ejecting the cooling water 7.

In addition to the jet outlet 12 connected to the jet inlet 11 of the cooling water 7 as shown in FIG. A cooling water passage 9 communicating with the outlet 10 is provided. The cooling water passage 9 is also provided for the water-cooled copper backing metal 2.

Next, the electrogas arc welding performed using the above apparatus will be described. First, SUS304
The base materials 1 to be welded having a plate thickness of 45 mm were butt-jointed with each other, and a water-cooled copper backing metal 2 was placed on the back side of the groove space 1a, and a water-cooled copper fronting metal 3 was placed on the front side.

Next, the welding wire 5 is fed into the groove space 1a through the nozzle 4, and the wire 5 is heated by arc heat.
Is melted and the nozzle 4 is constantly moved in the front and back directions to fill the groove space 1a and weld it. At this time, the molten metal is cooled and solidified by the back and front metal plates 2, 3 and the welded base material 1 is joined to form the weld metal 6.

Further, the nozzle 4 is sequentially moved upward to perform welding. Since this welding is performed in a single process regardless of the thickness, the welding amount is large and a large heat input is generated. Become. The temperature of the molten metal that rises due to this heat input is 1500 ° C. or higher in the case of austenitic stainless steel, and the base metal 1 to be welded becomes higher in temperature as it gets closer to the welded portion.

Therefore, in the present embodiment, as shown in FIG. 1, cooling water 7 for quenching the base metal 1 to be welded from below the table pad 3 is provided separately from the cooling water for the table pad 3. It was sprayed directly onto the base material and cooled.

A sensitization test was conducted on the welded portion obtained as described above, but no sensitized region was detected.
The welding conditions in the above are current 380A, voltage 3
8V, speed 2.5cm, heat input 270KJ / cm, stroke 40mm. Sensitization area is detected by JISG0571.
A 10% oxalic acid etch test method for stainless steel was used.

For comparison with the above results, when the above-mentioned sensitization test was conducted on the welded portion of the base material 1 to be welded, which was welded under the same conditions as above without quenching with the cooling water 7, it was found that the A sensitized area having a width of about 7 mm was detected on the 12 mm base metal side. From this, it was confirmed that this example is effective as a countermeasure for sensitization.

[0018]

The electrogas arc welding apparatus for stainless steel of the present invention comprises a backing plate fixed to the back side of the groove space in the vertical direction formed between two base materials to be butt-welded, A table pad provided on the front side of the groove space and sliding upward, a nozzle provided in the groove space for melting the welding wire, and a nozzle provided below the table plate after passing the table pad. Since the injection port for injecting the cooling water is provided on the surface of the solidified weld metal of, the weld metal in the high temperature state immediately after welding is rapidly cooled by the injected cooling water. It becomes possible to prevent sensitization of the welded portion between.

[Brief description of drawings]

FIG. 1 is an explanatory view of an electrogas arc welding apparatus according to an embodiment of the present invention, in which (a) is a side sectional view and (b) is a view taken along the line AA of (a).

FIG. 2 is an explanatory diagram of a front cover metal according to the above embodiment,
(A) is a side cross-sectional view, (b) is a BB arrow view of (a),
(C) is a CC arrow view of (a).

[Explanation of symbols]

 1 Base material to be welded 1a Groove space 2 Backing metal 3 Front metal 4 Nozzle 5 Welding wire 6 Welding metal 7 Cooling water 9 Cooling water channel 11 Injection outlet

Claims (1)

[Claims] 1. A backing plate fixed to the back side of a groove space in the vertical direction formed by abutting two pieces of stainless steel base materials to be welded together, and provided on the front side of the groove space and sliding upward. Front cover metal, a nozzle provided in the groove space for introducing and melting a welding wire into the space, and a surface of the weld metal formed under the front cover metal by solidifying the molten metal. An electrogas arc welding apparatus for stainless steel, which is equipped with an injection outlet for directly injecting cooling water.