JPS6247112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for butting and fillet welding stainless clad steel plates used for reaction vessels, tanks, pipes, etc. of general chemical and various industrial machines.

If we look at the conventional butt welding method of stainless steel clad steel plates with reference to Figures 1 to 4, when conventionally butt welding a stainless steel clad steel plate in which stainless steel 2 is clad on the surface of carbon steel 1, first the welding process shown in Figure 1 is performed. As shown in Fig. 2, a groove 3 is provided on the carbon steel 1 side, and after welding is performed using a welding rod made of the same material as the carbon steel 1 as shown in the welded part 4 in Fig. 2, as shown in Fig. 3. carbon steel 1 from the stainless steel 2 side
Dig into the side and perform Ura-dori 5. Next, as shown in Fig. 4, the carbon steel part 1 is welded with a welding rod made of the same material as welding part 6, and then the welding part 7 is welded with a welding rod made of the same material as stainless steel 2. A method of welding and finishing is used.

However, with the above method, stainless steel 2
If the wall thickness of the stainless steel 2 is less than 3 mm, the penetration of the welded part 6 of the carbon steel 1 and the base metal carbon steel 1 will affect the surface of the welded part 7 of the stainless steel 2, and the welded part of the stainless steel 2 will be damaged due to the increase in carbon content. The intergranular corrosion resistance of No. 7 decreases. For this reason, in the conventional welding method, there are major restrictions on the use of stainless steel clad steel plates where the wall thickness of the stainless steel 2 is 3 mm or less.

Furthermore, welding methods as shown in FIGS. 5 and 6 have been proposed to solve the above-mentioned problems, but each method has its own drawbacks.

In Fig. 5, in the butt weld of stainless clad steel plates, stainless steel 2 is first welded to carbon steel 1.
Peel it off to an appropriate width, weld only the carbon steel 1, and then insert a small stainless steel plate 8 made of the same material as the stainless steel 2 so as to wrap it around the welded part. Stainless steel 2 is welded to eliminate the influence of penetration.
However, in this welding method, it is difficult to separate the stainless steel 2 of the welded part and the base material carbon steel 1, which increases the cost.Also, welding is performed from above with a gap 10 remaining in the welded part, so welding defects are likely to occur. There are drawbacks such as.

The welding method shown in Fig. 6 involves cutting an appropriate gap between the stainless steel 2 and carbon steel 1 in the welding part, and especially cutting the stainless steel piece 1 made of the same material as the stainless steel.
This is a welding method in which the carbon steel 1 is inserted to eliminate the influence from the carbon steel 1 side during welding, but this method requires a troublesome groove preparation and increases costs. It has the disadvantage of being prone to defects.

In view of the above, the present invention is made of stainless steel with a wall thickness of 3 mm.
When welding the following stainless clad steel plates,
The purpose is to provide a welding method for stainless steel clad steel plates that does not reduce the corrosion resistance of molten stainless metal parts due to penetration from the base carbon steel side, is simple to work with, and has no welding gaps. The thickness of the stainless steel clad on the steel plate is 3
When performing butt welding or fillet welding of stainless steel clad steel plates with a thickness of 2 mm or less, weld a stainless steel welding rod of the same quality from the stainless steel side along the weld line of the two stainless clad steel plates to a thickness of 2 mm. A build-up welding is performed to form a build-up part, and then a groove is machined from the stainless steel side and the carbon steel side along each build-up part formed on the weld line, and the same groove is machined from the stainless steel side. Therefore, we propose a stainless steel clad steel plate welding method that is characterized in that welding is performed from the carbon steel side using a stainless steel welding rod of the same quality as this, and a carbon steel welding rod of the same quality as this.

An embodiment of the welding method of the present invention will be described with reference to FIGS. 7 and 8.

In FIG. 7, a built-up portion 13 having a thickness of about 2 mm and a width of about 50 mm is formed on the stainless steel 2 of the butt welded portion of the stainless clad steel plate using a stainless steel welding rod of the same quality. At this time, the build-up part 13 is formed with a low current so that the penetration into the stainless steel 2 does not reach the base material carbon steel 1.The thickness of the build-up part 13 is 2 mm.
This means that even if the wall thickness of stainless steel 2 is thin (about 1.5 to 2.0 mm), the wall thickness near the weld is the same as that of conventional stainless steel clad steel (about 3.0 mm). This is to ensure a certain level of wall thickness. Overlay part 1 formed in this way
After machining the groove 14 as shown by broken lines in FIGS. 3 to 8, stainless steel 2 of stainless clad steel and carbon steel 1 are welded from the base material carbon steel 1 using a carbon steel welding rod of the same quality as before. The base metal is welded as close as possible to the boundary of the stainless steel 2 and does not touch the stainless steel 2 to form a welded part 15, and then the carbon steel that was previously welded is welded from the stainless steel 2 side with a stainless steel welding rod of the same quality. A welded portion 16 is formed to slightly intersect portion 15.

Thus, in the welding method of the present invention, since the built-up portion 13 is formed in advance along the weld line,
Even in a stainless steel clad steel plate with a thin stainless steel wall, the stainless steel weld 16 does not penetrate deeply into the carbon steel 1 and carbon steel weld 15, and the influence of penetration from the carbon steel side can be reduced by conventional welding methods. It can be made to the same extent. Therefore, by the welding method of the present invention, there is no problem with the corrosion resistance of the welded part, and a thin stainless steel clad steel can be used as the stainless steel 2, so that the product cost can be reduced. Further, since the built-up portion 13 is simply formed on the surface of the stainless steel 2, the work is simple and no gaps remain at the welded portion.

A specific experimental example will be explained.

In the experiment, SUS 316L stainless steel plates with a wall thickness of 2 mm were butt welded. The welded portion of the stainless clad steel plate had a wall thickness of 4 mm because a 2 mm thick built-up portion of stainless steel was formed from the stainless steel side before beveling. After welding, the surface of the stainless steel welded part was chemically analyzed using the countback method, and the results showed that C: 0.028%, Cr: 17.83
%, Ni: 12.43%, Mo: 2.29%, almost unchanged from the analytical values for the stainless steel material, and it was judged that there was no influence of penetration from the carbon steel side due to welding. In addition, in order to compare with the welding method of the present invention, chemical analysis was performed after welding using the conventional welding method using the same materials, and the results were as follows: C: 0.045%, Cr: 17.10%, Ni: 13.30%.
Mo: 2.55%, clearly influenced by penetration from the carbon steel side, and it was thought that intergranular corrosion resistance decreased as the C content increased.

[Brief explanation of the drawing]

Figures 1 to 4 are flowcharts of the conventional welding process for stainless clad steel, and Figures 5 and 6 are
The diagrams are schematic diagrams of other conventional welding methods, Figures 7 and 8.
The figures are schematic diagrams of the welding method of the present invention, the former being before welding and the latter being after welding. 1...Carbon steel, 2...Stainless steel, 13...
Overlay part, 14...Bevel, 15...Carbon steel welded part,
16... Stainless steel welded part.

Claims (1)

[Claims] 1. When performing butt welding or fillet welding of stainless steel clad steel plates with a wall thickness of 3 mm or less on a carbon steel plate that is the base material, the weld line of the two stainless steel clad steel plates to be welded Using a stainless steel welding rod of the same quality as the stainless steel welding rod, welded the stainless steel to a thickness of about 2 mm from the stainless steel side of the stainless steel clad steel to the carbon steel side, taking care not to melt the stainless steel side. The thickness is increased locally, and then a groove is machined from the stainless steel side and the carbon steel side along each overlay formed on the weld line, and the same groove is machined from the stainless steel side using a stainless steel welding rod of the same quality. This is a stainless clad steel plate welding method that is characterized by welding from the carbon steel side with a carbon steel welding rod of the same quality.