JPS62275578A - Welding method for clad steel - Google Patents

Abstract

PURPOSE:To avoid a stress concentration on weld zones to require a seal and to improve the strength of the weld zones by forming a spot facing groove penetrating up to the lower part of clad layers and covering a strap plate in a state with filler metals inserted into the spot facing groove to weld the strap plate to the clad layers. CONSTITUTION:A part of the clad layers 1 is removed and base metals 2 are exposed to form a welding groove and the spot facing groove penetrating up to the lower part of the clad layers 1 is formed. Then, after a welded joint 4 to connect base metals 2 mutually by the welding groove is formed, the filler metals 5 in a split state is inserted into the spot facing groove and a spacer 10 is inserted between both the filler metals 5 and intervals between the filler metals 5 and the spacer 10 are tack-welded. Next, the strap plate 6 is inserted between the clad layers 1 in an opposed state and the butt welding is performed by the welding groove 3 to constitute the sealing structure by the weld zones 7. Since both the clad layers 1 are connected with the strap plate 6 almost rectilinearly, the concentrated stress does not take place on the clad layers and the strength can be improved.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method for welding clad steel, and in particular to the formation of a welded joint when the clad steel is titanium or a titanium alloy. This relates to an effective welding method.

"Prior Art" Generally, clad steel is made of low alloy steel such as carbon steel as a base material, and the surface is coated with corrosion-resistant material such as titanium, stainless steel, etc.
Products with wear-resistant metals bonded to them, especially those whose cladding layer is made of titanium or titanium alloys, have excellent corrosion resistance and are therefore used in important applications such as nuclear power plants, thermal power plants, and chemical plants. used in parts.

Conventionally, when welding titanium clad steel, the method shown in Figures 2 (A) to D) has been adopted because direct welding between titanium or titanium alloy and carbon steel is not possible. There is.

That is, when the cladding layer l in the clad steel is titanium or a titanium alloy, a part of the cladding layer l is removed to expose the base metal 2, and a welding groove 3 is formed in the exposed base metal 2, First, weld the welding groove 3, as shown in Figure 2 (
A welded joint 4 shown in A) is formed. And weld joint 4
A filler metal 5 made of titanium or a titanium alloy is inserted between the cladding layers l on both sides of the cladding layer l as shown by the arrow in FIG. 2(A) to cover the weld joint 4. As shown in FIG. 2(B), the filling metal 5 and the cladding layer 1 are temporarily welded. Next, as shown in FIG. 2(C), a patch plate 6 having a width larger than this and made of -titanium or a titanium alloy is placed on top of the filler metal 5 to cover it, and a second As shown in Figure (D), fillet welding is performed between the side portion of the plate 6 and the surface of the clad layer 1 to form a welded joint of the entire clad steel.

With such a welding method, the Crabt layer 1 is attached to the backing plate 6.
In addition, when pressure is applied to the support 6 in a direction perpendicular to the surface, it is received by the base material 2 via the filler metal 5, so it is possible to suppress a decrease in pressure resistance strength. .

"Problem to be solved by the invention" However, because the difference in linear expansion coefficient between carbon steel and titanium is relatively large (for example, about 30% difference), the filler metal 5 is temporarily welded. , since the cladding layer 1 is not substantially connected, the lines of force when thermal displacement such as expansion occurs will extend from the cladding layer l to the welding part 7, as shown by the chain line R in FIG. 2(D). It reaches the caul plate 6 via the welding part 7, and a large bend occurs in the vicinity of the welded part 7. Therefore, a problem arises in that stress tends to concentrate on the welded portion 7.

The present invention aims to solve the problems of the prior art, and aims to avoid stress concentration on welded parts that require sealing, improve the strength of welded parts, and improve safety. It is intended for such purposes.

"Means for solving the problem" A counterbore groove that penetrates to the bottom of the cladding layer is formed in the exposed part of the base material where a part of the cladding has been removed, and a welded joint is formed in the exposed part of the base material, With the filler metal inserted into the counterbore groove, insert a backing plate between the cladding layers to cover the filler metal, weld the corresponding gates between the plate and the cladding layer, and align the cladding layer and the backing plate in a straight line. Place it on top,
By welding them together, the line of force of the displacement force is made substantially straight, thereby suppressing stress concentration at the welded portion.

"Example" Hereinafter, an example of the clad steel welding method according to the present invention will be described based on FIGS. 1(A) to D).

In this embodiment, if the cladding layer 1 is made of clad steel or titanium or a titanium alloy, part of the cladding layer I is removed to expose the base material 2, and the exposed portion 8 of the base material 2 is , the above-mentioned welding groove 3 is formed, and a countersink groove 9 that penetrates into the lower part of the cladding layer 1 is also formed. That is, the portion shown by the chain line in FIG. 1(A) is removed. Then, after forming a weld joint 4 for interconnecting the base metals 2 and 2 with the weld groove 3, as shown in FIG.
As shown by the chain line arrows in B), the split filler metals 5 are inserted into the counterbore grooves 9, and between the two filler metals 5, as shown by the solid line arrows in FIG. 1B, A spacer IO is inserted to cover the filler metal 5 and the spacer IO. In this case, the filler metal 4 and the spacer 10 are both made of titanium or a titanium alloy, and the filler metal 5 and the spacer 10 are temporarily welded.

Next, as shown by the arrow in FIG. 1(C), a patch plate 6 made of titanium or titanium alloy is inserted between the facing cladding layers l to cover the filler metal 5 and the spacer [0], and to cover the cladding layer l. Butt welding is performed using the welding groove 3 previously formed on the layer 3 and the backing plate 6, as shown in FIG. 1(D).
As shown in FIG. 2, the welded portion 7 constitutes a sole structure and smoothly connects the cladding surfaces of the welded portion.

When the clad steels are connected by such a welding method, the two clad layers l.1 are connected in a substantially straight line by the backing plate 6, and the welded portion 7 is arranged in a straight line. Therefore, the lines of force when a displacement force due to thermal expansion is applied to the cladding layer 1 are approximated to straight lines, as shown by the chain line Ra in FIG. A simple stress of 100% is applied, and so-called concentrated stress does not occur.

In the description of one embodiment, the cladding layer is made of titanium or a titanium alloy, but the material is not limited to these materials, and may include materials in which there is a difference in linear expansion coefficient between the base material and the cladding layer. This can be applied to large objects.

In addition, since the counterbore groove 9 is theoretically more advantageous as it increases in depth, it may be set in consideration of workability.

"Effects of the Invention" As explained above, according to the clad steel welding method of the present invention, ■ a countersunk groove that penetrates to the bottom of the clad layer is formed;
Since the caul plate and the cladding layer are welded by placing the filler metal into the counterbore groove and welding the caul plate and the cladding layer, a welded joint of clad steel is constructed by making the caul plate and the cladding layer almost in a straight line. can do.

■Based on the above, the displacement force is transmitted almost linearly, suppressing stress concentration and improving strength.

It is the second one that has the same effect.

[Brief explanation of drawings]

Figures 1 (A) to D) are explanatory diagrams of the process order in an embodiment of the clad steel welding method according to the present invention, and Figure 2 (
A) to D) are explanatory views of the process order in a conventional example of a welding method. ■...Clad layer, 2...Base material, 3...
...Welding groove, 4...Welding joint, 5...
...Filling metal, 6...Passing plate, 7...
Welded part, 8...Exposed part, 9...Counterbore groove, IO...Spacer. Applicant Ishikawajima-Harima Heavy Industries Co., Ltd. Figure 1 (A) Figure 1 (D) Figure 2 (B) Figure 2- (D)

Claims (1)

[Claims] A counterbore groove that penetrates to the bottom of the cladding layer is formed in the exposed part of the base material where a part of the cladding has been removed, a welded joint is formed in the exposed part of the base metal, and a filler metal is inserted into the counterbore groove. A method for welding clad steel, characterized by inserting a patch plate between the clad layers to cover the filler metal, and welding between the corresponding plate and the clad layer.