JPS5937157B2 - Single-sided welding method for stainless steel fittings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for single-sided welding of stainless-clad steel joints.

Fe-C with excellent corrosion resistance, high temperature oxidation resistance, high temperature strength, etc.
Clad steels made of r-series and Fe-Cr-Ni stainless steels have traditionally been widely used in structures exposed to corrosive environments.

Conventionally, the above-mentioned clad steel joint welding method has generally been the first method.
This is carried out by the method shown in Figure a and Figure 1b.

That is, in FIG. 1a, a V-shaped groove is provided with the opening on the composite material 1 side, and weld metal 3 having the same composition as the base material 2 is inserted from the bottom of the groove.
After welding the base metal part, weld the composite part on top of the base metal weld metal 3 using a welding material whose alloy composition is equivalent to or higher than that of composite material 1. A weld metal 4 having a performance higher than or equal to the above was obtained. Also the first
In Figure b, an X-shaped groove is provided, and the base metal 2 is first welded from the base metal 2 side with a weld metal 3a equivalent to the base metal 2, and then the base metal 2 is welded from the composite material 1 side with a weld metal 3a equivalent to the base metal 2. A good welded joint was obtained by welding a weld metal 3b and then welding a weld metal 4 of a high alloy equal to or higher than the composite material 1 on top of the weld metal 3b. If joint welding of stainless clad steel can be carried out from the composite material side in this way, the method shown in Figure 1 a and b can be used without any problems, but in the case of longitudinal welding or circumferential joint welding of small diameter internal stainless clad steel pipes Since the welding equipment and welding operator cannot enter inside the steel pipe, welding must be done from the outside of the steel pipe, that is, from the base metal side. In this case, the conventional welding method is to create a V-shaped groove with the opening on the base metal 2 side as shown in Fig. 2, and the part of the base metal 2 is Until now, weld metal 4 was obtained by using a welding material containing a larger amount of alloy components than composite material 1 in terms of the total thickness of clad steel. This is because when welding is performed using a welding material of the same type of low carbon steel or low alloy steel as the base metal on a high alloy weld metal of the composite material, a part of the weld metal of the base metal will be mixed with the weld metal of the composite material. As a result, the components of the cladding steel become concentrated, which causes a part of the base weld metal to harden, resulting in a significant decrease in ductility and toughness, as well as cracking. This is because the welding metal of the material must be welded. When welding a single-sided joint from the base metal side in this way, the thicker the base metal, the more welding material will be used, and since the welding material is a stainless steel high alloy, the material cost will increase, and welding Since the joint is made of stainless steel material, it may not be possible to ensure the required strength and toughness of the base material. An object of the present invention is to provide a new welding method for solving the above-mentioned problems that occur in single-sided welding of clad steel from the base metal side.

In the present invention, the welded part of the composite material has performance such as corrosion resistance that is equal to or better than that of the composite material, and the welded part of the base metal is welded with a welding material that has mechanical properties equal to or better than that of the base material. However, by providing an intermediate layer between the welded part of the base metal and the welded composite material, the problem that occurs at the boundary part is solved.

The details of the present invention will be explained with reference to the drawings.

FIG. 3 is an explanatory diagram of the welding method of the present invention, in which a V-shaped groove with an opening on the base metal 2 side is provided, and the composite material 1 has a protruding part, and the welding parts are butted at that part. In addition to V-shaped grooves, U-shaped grooves can also be used. First, only the composite material is welded and joined with weld metal 4. In this case, if only the composite material can be melted, there is no need to use a filler metal, but if there is a risk of melting part of the base metal, use a filler metal with a higher alloy content than the composite material. However, it is necessary to ensure that the chemical composition of the weld metal falls within a predetermined composition range. Next, one or more intermediate layers are welded onto the composite weld metal 4 using a welding material such as low carbon steel. At this time, the composition of the intermediate layer weld metal 5 is CO in weight% due to the dissolution of alloying elements from the composite weld metal.
．． 15% or less, Sil. 0% or less, Mn2. 0% or less,
It must be composed of 2% or less Crl, 2% or less Nil, and the balance Fe and unavoidable impurity elements. Next, the entire thickness of the base metal portion 2 is joined by the weld metal 3 on the intermediate layer weld metal 5 using a welding material containing an alloy element equal to or higher than that of the base metal.

The chemical composition of the intermediate layer weld metal 5 is CO. 15% or less, Si
l. 0% or less, Mn2. O% or less, Crl2% or less, N
The reason why il is defined as 2% or less, the balance being Fe and unavoidable impurity elements is as follows. If C exceeds 0.15%, it will harden due to the heat effect of the next welding, that is, the weld metal 3, and the ductility will decrease. When Si is 1.0% or more, tensile strength increases, but ductility and toughness decrease. 12% Cr and Ni
When the Cr content of the intermediate layer is increased, the base metal weld metal 3 placed on the intermediate layer weld metal 5 contains Cr. Alloying elements such as Ni dissolve and harden, creating a structure with significantly reduced ductility and toughness. In other words, if the chemical content of the intermediate layer weld metal 5 following the welded part of the composite material is within the above range, the mechanical properties of the intermediate layer weld metal 5 are good, and furthermore, the mechanical properties of the base metal weld metal 3 following it are good. The properties are also good. As a result, it is possible to obtain stainless clad steel welded joints in which the composite material welded part has performance such as corrosion resistance equal to or better than that of the composite material, and the base metal welded part has mechanical properties equal to or superior to the base metal. . Next, examples of the present invention will be shown.

Example 1 The sample material was SUS3O4 with a thickness of 2.5 mm.
The base material used was SS4L stainless clad steel with a thickness of 10 mm.

The groove shape is as shown in Fig. 4a, and the groove angle of the base material 2 is α=α5=45, and the protrusion of the composite material is l=l″=2 mm.
It is. The welding conditions for the composite material are shown in Table 1-(1), and the welding conditions for the intermediate layer and base metal are shown in Table 1-(support). Using these welding conditions, welding of the composite material part with the groove shape shown in Fig. 4a is performed in 1.
Using Type 31O filler metal with a diameter of 0 mm, welding was performed by pulsed TIG automatic welding as shown in FIG. 4b, and only the composite part 2 was joined with weld metal 4. Subsequently, CO. One layer of intermediate layer weld metal 5 was welded by TIG automatic welding using 1.6 m of light low carbon steel filler metal at O2% as shown in FIG. 4c. Furthermore, weld metal 6 was welded to the final layer on intermediate layer weld metal 5 by mild steel covered arc welding as shown in FIG. 4d. Table 2 shows the chemical composition of the intermediate layer weld metal 5 obtained by the above procedure.

Table 3 also shows the mechanical test results for the joint welds. As shown in the results, the tensile strength and toughness of the welded joint according to the present invention were superior to those of the clad steel material, and moreover, good ductility was obtained. Example 2 The sample material was the same as in Example 1, the groove shape and the welding of the composite part were also the same as in Example 1, and the top of the weld metal 4 of the composite part as shown in Fig. 4c'' was used. Two layers of intermediate layer weld metal 5 were welded by TIG automatic welding using a low carbon steel filler metal containing 2% CO.O.

Thereafter, the weld metal 6 was welded to the final layer by mild steel covered arc welding as shown in Fig. 4 d". Table 4 shows the chemical composition of the weld metal 5 of the second layer of the intermediate layer welded part obtained by the above procedure. Shown below.

Table 5 also shows the mechanical test results for the joint welds. As shown in the results, as in Example 1, the tensile strength and toughness of the welded joint were superior to those of the clad steel raw material, and good ductility was obtained. As described above, according to the present invention, it has become possible to perform joint welding in which the composite material and the base metal welded portion have performance equal to or better than that of the raw material of the clad steel by single-sided welding of stainless clad steel from the base metal side.

[Brief explanation of the drawings] Figures 1A and b are explanatory diagrams of the conventional welding method from the composite material side;
Figure 2 is an explanatory diagram of the conventional welding method from the base metal side, Figure 3 is an explanatory diagram of the welding method of the present invention, and Figures 4A, b, c, c',
D and d'' are explanatory diagrams of examples of the present invention. 1... composite material, 2... base material, 3...
...Base metal weld metal, 4... Composite weld metal, 5.
...Intermediate layer weld metal, 6...Base metal weld metal.

Claims (1)

[Claims] 1. In single-sided welding of stainless clad steel joints made of Fe-Cr or Fe-Cr-Ni stainless steel and mild steel or low-alloy steel as the base material, a groove with an opening on the base metal side is provided, First, the composite part is welded using a filler metal with approximately the same chemical composition as the composite material, and a low carbon steel filler metal is used on top of this composite weld metal, using the TIG welding method.
One side of a stainless clad steel joint characterized in that one or more intermediate layers are welded, and the final layer is further welded onto the intermediate layer with a welding material containing an alloy element equal to or higher than that of the base metal. Welding method.