JPH01210171A - Method for welding stainless steel or nickel alloy and carbon steel - Google Patents

Abstract

PURPOSE:To reduce the cost in welding and to improve the quality by forming a build-up layer by the welding material contg. Cr, Mo, Ni, C and N at specified rate on the groove face at high alloy side and executing continuous welding by the welding material for carbon steel in the space with the carbon steel. CONSTITUTION:A build-up layer 3 is formed on the groove face at a high alloy 1 side by the ferrous welding material contg. 20-30wt.% Cr, 2-4.5% Mo, 4-13% Ni, <=0.06% C and <=0.02% N and whose (Ni+30C+20N)/(Cr+Mo) is within 0.20-0.70 range. Welding is then performed by the welding material for carbon steel between build-up layer 3 and carbon steel 2 side. The welding cost is reduced because welding is executed by an ordinary carbon steel welding material after forming the build-up layer 3 in advance at the high alloy 1 side. The quality of the weld zone is improved due to the generation of the crack and defect accompanied by a high alloy melting being prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to stainless steels, nickel-based alloys, mild steels, low-alloy steels, etc., which are used in chemical plants, atomic couplants, etc. due to their excellent properties such as corrosion resistance and heat resistance. The present invention relates to a welding method for welding stainless steel or nickel-based alloy to carbon steel (hereinafter referred to as carbon steel), and more specifically to welding stainless steel or nickel-based alloy and carbon steel economically and efficiently, and to obtain a high-quality welded part. The present invention relates to a method for welding dissimilar metals.

(Prior technology) Stainless steel and nickel-based alloys with excellent corrosion resistance, heat resistance, high-temperature strength, low-temperature toughness, etc. are used in chemical plants, atomic couplants, etc., depending on the use and required characteristics of the structure. Used in various ways and in large quantities. However, stainless steel and nickel-based alloys are mostly used in parts of structures that are exposed to harsh environments, and in most other parts, they are used for reasons such as economy, workability, and strength. Carbon steel has been used since then. Therefore, as a structure, it is necessary to weld dissimilar metals such as stainless steel or nickel-based alloy and carbon steel.

The conventional method for joining stainless steel or nickel-based alloy to carbon steel is as shown in Figures 2 (a) and (b).

This is done as shown in (g) and (c). That is, the second
In figure (a), stainless steel or nickel-based alloy (
A V-shaped opening is provided on both the 1 side (hereinafter referred to as high alloy) and the carbon steel 2 side, and in (b), high alloy type austenitic stainless steel or Ni
The weld metal 4 was obtained using a welding material such as a so-called Inconel-based -Cr-Fe alloy. Alternatively, for the purpose of obtaining a higher quality welded part, after forming a build-up layer 3 on the groove surface of the carbon steel 2 side with the welding material such as the Inconel type as shown in (c), as shown in (c). The weld metal 4 was obtained using a high alloy type welding material in accordance with the material of the high alloy 1 side. The main reason for adopting such a welding method is to prevent weld cracking and ensure the ductility and toughness of the welded part.

In the conventional method as described above, a large amount of expensive welding material with poor weldability is used for welding, and a large sacrifice has to be made in terms of economy and efficiency.

Furthermore, the high Cr, high Ni weld metal 4 has a large coefficient of thermal expansion, so there are problems such as deformation and a large difference in strength compared to carbon steel 2.1. Moreover, the selection of suitable welding materials according to the materials of the high alloy 1 side and the carbon steel 2 side requires specialized and extensive knowledge, and there are many design difficulties.

In addition, JP-A-51-40345 discloses that in welding martensitic stainless steel and mild steel, the initial welding area and the final welding area on the martensitic stainless steel side are made of austenitic stainless steel containing 5 to 15% ferrite. A welding method has been disclosed that prevents weld cracking and reduces weld deformation by welding with a steel welding rod and welding other parts with a chromium-molybdenum steel welding rod, but the steel materials to be welded are The scope of application is limited to martensitic stainless steel and mild steel, and the main welding is limited to chrome molyden steel welding rods, so weldability,
Issues still remained regarding welding deformation and compatibility of weld metal properties with the base metal.

In addition, JP-A-59-10478 discloses that in welding stainless steel and low alloy steel, TIG welding or plasma welding is performed in advance on the groove surface on the low alloy side of the stainless steel at the location corresponding to the first layer weld. By overlaying Inconel welding material, then attaching a backing metal and overlaying Inconel welding material using a welding method with high welding heat input, high temperature cracking of dissimilar metal welded joints is prevented and reliability is improved. Although a welding method for obtaining dissimilar metal welded joints with high dissimilar metal properties has been disclosed, there is a problem in terms of economic efficiency because an expensive Inconel-based welding material is used as the welding material. Problems also remained in compatibility with the base material.

As described above, in welding stainless steel or nickel-based alloy and carbon steel, there is a strong demand for a welding method that is simple in design, economical, and highly efficient in welding, and that can yield high-quality welds.

(Problems to be Solved by the Invention) That is, the present invention solves the problems of conventional methods of welding stainless steel or nickel-based alloys with carbon steel, such as design difficulties and sacrifices in terms of economy and efficiency.

This was done to resolve incompatibility in the quality of welded parts, and its purpose is to weld dissimilar metals between stainless steel or nickel-based alloy and carbon steel.
To provide a welding method that enables economical and highly efficient welding without impairing the properties of stainless steel, nickel-based alloys, and carbon steel, and that makes it possible to easily obtain sound and high-quality welds. It's about doing.

(Means for Solving the Problem) The present inventors have proposed a method for welding stainless steel or nickel-based alloy and carbon steel without impairing the properties of the stainless steel or nickel-based alloy base material and the carbon steel base material. In addition, we conducted extensive studies with the aim of finding a method that would enable economical and highly efficient welding without causing harmful defects such as weld cracks. The details of the resulting method of welding stainless steel or nickel-based alloy and carbon steel according to the present invention will be explained with reference to the drawings.

In Figure 1 (a), a V-shaped aperture is provided on the high alloy 1 side and the carbon steel 2 side, and in (b), a Cr
20-30%, Mo2-4.5%, Ni4-13%, C
0.06% or less, N0.20% or less, and (Ni +
30C+20N)/(Cr+Na) is 0.20 to 0.
One or more overlay layers 3 are formed using a welding material which is in the range of 70% and the balance is Fe and unavoidable impurities.

If the material of the high alloy 1 is stainless steel or a nickel-based alloy, the build-up layer 3 obtained from the welding material in this composition range will be able to withstand the composition fluctuations caused by melting the high alloy 1 regardless of its composition. It has high cracking resistance and sufficient ductility, and in (c), the high alloy 1 and the carbon steel 2 on which the build-up layer 3 is formed are butted together and welded with a welding material normally used for welding the carbon steel 2 together. By doing so, it is possible to obtain a weld metal 4 that does not cause weld cracks or other harmful defects, has good ductility, and has mechanical properties equivalent to or better than carbon steel 2. In other words, it is inexpensive, has good welding workability, and has high strength, etc. It has become clear that it is possible to use a welding material for carbon steel whose characteristics are compatible with carbon steel 2 and whose deformation due to welding is small.

The present invention is based on the above new knowledge, and the gist thereof is that in welding stainless steel or nickel-based alloy and carbon steel, welding of Cr20 to Cr20 on the groove surface on the stainless steel or nickel-based alloy side 30%, Mo2~4
．． 5%, Ni4-13%, C0006% or less, N0.2
0% or less and (Ni +30G +20N) / (
Cr + Mo) is in the range of 0.20 to 0.70,
Stainless steel or nickel-based alloy characterized by forming one or more overlay layers with a welding material consisting of the remainder Fe and unavoidable impurities, and then butt welding with carbon steel using a welding material for carbon steel. It is in the welding method with carbon steel.

Note that the stainless steel referred to here refers to Japanese Industrial Standard JI.
Refers to austenitic, austenitic/ferritic, ferritic, martensitic, precipitation hardening stainless steels, etc. specified in sG 4305, etc.

In addition, the ASME (American
5oc-iety of Mechanical E
Refers to the so-called Inconel-based and Hastelloy-based alloys, which are standardized by NGINEERS and others, and whose main component is nickel.

Furthermore, carbon steel refers to mild steel, high-strength steel, low-alloy steel such as heat-resistant steel and low-temperature steel.

(Function) First, the high alloy side of stainless steel or nickel-based alloy should be selected according to the required characteristics of the structure to which it is applied, and it is economical to compare stainless steel or nickel-based alloy with carbon steel. Another major feature of the present invention is that it enables efficient welding of dissimilar materials.

Next, regarding the composition of the welding material for forming a build-up layer on the high-alloy side groove of stainless steel or nickel-based alloy, if the Cr content is less than 20%, the stainless steel or nickel-based alloy of the high-alloy side base material will be melted. The high-temperature cracking resistance of the build-up layer weld metal becomes insufficient due to component fluctuations caused by this. When the Cr content exceeds 30%, the heat-affected zone generated in butt welding using the welding material for carbon steel becomes brittle, and the ductility and toughness of the build-up layer deteriorate, and at the same time, the amount of Cr in the butt welding metal using the welding material for carbon steel decreases. Excessive amount leads to deterioration of ductility. Therefore C
r is 20 to 30%.

If Mo is less than 2%, the hot cracking resistance and susceptibility of the butt weld metal made by the welding material for carbon steel will be insufficient.

If it exceeds 4.5%, the build-up layer weld metal becomes brittle. Therefore, Mo is set at 2 to 4.5%.

If Ni is less than 4%, the heat-affected zone that occurs during butt welding with carbon steel welding materials becomes brittle, and the ductility and toughness of the overlay layer deteriorate.
At the same time, the butt weld metal made of the carbon steel welding material becomes brittle and has a low ductility. If it exceeds 13%, the high-temperature cracking resistance of the build-up layer weld metal will be insufficient against component fluctuations due to dilution from the high-alloy side base metal. Therefore, Ni should be 4 to 13%.

If C exceeds 0.06%, the heat-affected zone produced in butt welding using the carbon steel welding material becomes brittle, and at the same time, the ductility of the butt weld metal using the carbon steel welding material deteriorates.
Limit to 0.6% or less.

If N exceeds 0.20%, welding defects such as blowholes will occur in butt welding using carbon steel welding materials, and welding workability will deteriorate, so the N content should be 0.20% or less.

Next, if the value of (Ni + 30C + 20N) / (Cr amount - 〇) is less than 0.20, the overlay weld metal itself becomes brittle and has low ductility, and at the same time, the butt weld metal made of welding material for carbon steel also becomes brittle and ductile. It becomes a low organization.

If it exceeds 0.70, the susceptibility to hot cracking of the build-up layer and butt weld metal becomes extremely large. Therefore 0.20-0.7
The range is 0.

Furthermore, in order to perform butt welding with carbon steel welding materials and ensure the soundness of the butt weld metal, a single overlay layer is sufficient and the effect remains the same even with two or more layers. .

In addition, for butt welding of a high-alloy base material of stainless steel or nickel-based alloy with a built-up layer formed thereon, and a carbon steel base material, it is possible to perform economical, high-efficiency welding with little deformation. In order to maintain the same or better properties, JTS or 8WS (American
Use appropriate welding materials as stipulated by the Welding 5 Specification. Furthermore, in order to prevent cracks from occurring in the butt weld metal, and to ensure other properties such as ductility, toughness, and strength, it is desirable to keep the dilution rate from the overlay weld metal to 30% or less. . In order to keep the dilution ratio below 30%, it is necessary to control welding conditions such as current and speed. Note that the dilution rate from the build-up layer referred to here refers to the percentage of the area of the weld build-up layer melted in the butt weld metal using a welding material for carbon steel, and is expressed by the following formula.

D = -X 100 D unit %; Dilution rate A unit -; Area of butt weld metal by carbon steel welding material B unit -; Melted area of build-up layer weld metal. One or more build-up layers are formed on the high-alloy side groove surface of stainless steel or nickel-based alloy using a welding material with a specific composition range, and then a final round of butt welding with carbon steel is performed using a welding material for carbon steel. By employing this welding method, high-quality welds can be obtained economically and with high efficiency in welding a wide range of stainless steels or nickel-based alloys with carbon steel.

The effects of the present invention will be specifically explained below using Examples.

(Example) Table 1 shows the base materials tested. Base material symbol A in the table.

B, C, D, E, F, and G are high-alloy base materials of stainless steel or nickel-based alloy, and base metal symbols H, I, J, and K are carbon steel base materials such as mild steel or low-alloy steel. It is. All of these base materials have a plate thickness of 25 mm.

Table 2 shows the welding materials used for forming the built-up layer.

These welding materials with internal symbol f have a C content of more than 0.06% and a Cr content of more than 30%, and are outside the scope of the present invention.

The welding material with symbol g is (Ni+30C+20N)/(C
r + Mo) less than 0.20, which is outside the scope of the present invention.

In addition, the welding material with the symbol has less than 20% Cr and (Ni+
The value of 30C+20N)/(Cr+Mo) exceeds 0.70 and is outside the scope of the present invention. Furthermore, the welding material with symbol i is a Ni-Cr-Fe-based so-called Inconel alloy, which contains less than 20% Cr and more than 13% Ni and 2% Mo.
less than and (Ni +30C+ 20N) / (Cr
+Mo) exceeds 0.70 and is outside the scope of the present invention.

Table 3 shows the results of dissimilar metal butt welding tests using combinations of these base materials and welding materials for forming overlay layers.

The groove shape is v-shaped as shown in Figure 1 (a), and firstly, as shown in Figure 1 (b), the groove surface of the base material on the high alloy side is used for forming a build-up layer as shown in Table 3. Overlay welding was performed using the welding material, and overlay layer weld metal 3 was obtained. In the case of welding using a covered arc, the build-up layer is formed using a rod diameter of 4. Omm, welding current 12
Manual welding was performed at 0 A, welding voltage of 24 cm, and welding speed of 15 cm/min.

In the case of TIG welding, the wire diameter is 2.4 mm, the welding current is 120 A, the welding voltage is 12 cm, and the welding speed is 10 cm/m.
Manual welding was performed using an Ar shielding gas flow rate of 20 f/min. In addition, in the case of MIG welding, the wire diameter is 1.2
Body, welding current 220A, welding voltage 22V, welding speed 20
cm/min, Ar shielding gas flow ff1201/
Semi-automatic welding of min. Furthermore, in the case of CO□ welding using flux-cored wire, the wire diameter is 1.2 mm.

Welding current 220A, welding voltage 20■, welding speed 20cm
/min, Cot shield gas flow rate 201! /m
In semi-automatic welding was performed.

Second, as shown in Figure 1 (C), the high alloy side base material and the carbon mesh side base material on which the build-up layer was formed are compatible with the carbon steel base material, except for test Nα24, as shown in Table 3. Weld metal 4 was laminated using carbon steel welding material and welded to the final stage. In the case of covered arc welding, the rod diameter is 5. Omm, welding current 190
~240A, welding voltage 24~28V, welding speed 14~2
Manual welding of 5CIII/ll1in was performed. For MIG welding, wire 1.2mm, welding current 220-29
0A, welding voltage 18~22v, welding speed 20~30c
Semi-automatic welding was performed at a flow rate of 201 m/min and an Ar+10% CO2 shielding gas flow rate of 201 m/min. For CO□ welding with flux-cored wire, the wire diameter is 1.2
Welding current 200~28OA, welding voltage 18~22■
Semi-automatic welding was performed at a welding speed of 20 to 30 cm/min and a COz shielding gas flow rate of 20j2/min.

In order to evaluate the soundness of the build-up layer, a color check inspection of the first layer weld metal was performed to check for cracks.

In addition, in order to evaluate the soundness of the butt weld metal, a color check inspection was performed on the first layer weld metal to check for cracks.

Furthermore, after all welding was completed, a side bending test based on JIS Z 3122 and a joint tensile test based on JIS Z 3121 were conducted in order to evaluate the soundness of the entire butt weld of dissimilar materials.

As a result of these dissimilar metal butt welding tests, the welding method test results of the present invention were as follows:
14,16,17.18,20゜21.22.23.2
In No. 5 and No. 26, no cracks were observed in the first layer of the overlay layer or the first layer of butt weld metal, and there were no defects in the side bending test, showing sufficient ductility. Furthermore, in the joint tensile test, the base metal original It is clear that the material has a strength greater than that of the base material, as it is broken in the mass part.

On the other hand, in test No. 3, the build-up layer was welded (Ni
+30C+20N)/(Cr +Na) value is 0.20
Since the welding material for forming the build-up layer was used in the test, cracks occurred in the build-up layer and the first layer of butt weld metal, and cracks also occurred in the side bending test. Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

In test No. 6, the build-up layer was welded using Ni-Cr-Fe.
Since an alloy welding material rod was used, no cracks occurred in the build-up layer, but cracks occurred in the initial layer of butt weld metal, and cracks also occurred in the side bending test.

Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

In test No. 12, the build-up layer was welded using a welding material for forming the build-up layer with a C content exceeding 0.06% and a Cr content exceeding 30%, so cracks occurred in the build-up layer and the first layer of butt weld metal. However, cracking also occurred in the side bending test. Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

In test No. 15, the welding of the build-up layer was performed with less than 20% Cr and (Ni + 30C + 20N) / (Cr
Since the welding material for forming the build-up layer had a value of +Mo) exceeding 0.70, cracks occurred in the build-up layer and the initial layer of butt weld metal, and cracks also occurred in the side bending test. Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

In test Nα19, dissimilar metal butt welding was performed directly with the welding material for the base metal on the carbon steel side without forming an overlay layer, so cracks occurred in the first layer of the butt weld metal, and cracks also occurred in the side bending test. did. Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

Test Nα24 was conducted using Ni-Cr-Mo alloy coated arc welding rod AWS ENi for butt welding of dissimilar materials without forming a built-up layer.
CrM.

-3 was used, cracks occurred in the first layer of butt weld metal, deformation due to welding was large, and weldability was poor, resulting in cracks or welding defects in the side bending test.

Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

In test No. 27, the build-up layer was welded using a welding material for forming the build-up layer with a Cr content of less than 20% and a value of (Ni+30C+20N)/(Cr+Mo) exceeding 0.70. Cracks occurred in the first layer of butt weld metal, and cracks also occurred in the side bending test. Furthermore, in the joint tensile test, the weld metal broke and there was also a problem with the strength.

(Effects of the Invention) As described above, the present invention enables welding of stainless steel or nickel-based alloy and carbon steel by applying a welding material having a specific composition range to the groove surface on the high-alloy side of stainless steel or nickel-based alloy. By forming a built-up layer, then butting it with carbon steel and welding it to the final stage with a welding material for carbon steel, it is possible to economically and efficiently produce an extremely sound welded part with little deformation and properties equal to or better than those of the base metal. Structures such as chemical plants and atomic couplants that require dissimilar metal welding between a wide range of stainless steels or nickel-based alloys and a wide range of carbon steels such as mild steel and low alloy steel. This will greatly improve overall soundness and economic efficiency.

[Brief explanation of the drawing]

Figures 1 (a), (b), and (c) are explanatory diagrams of the welding method of the present invention;
FIGS. 2(A), 2(B), 2(C) are explanatory diagrams of the conventional welding method. 1...High alloy, 2...Carbon steel, 3...Build-up layer, 4
...butt weld metal. Figure 1 (A) 1' (High alloy) Figure 2 (A) Procedural amendment (method) % formula % 1. Indication of the case Patent Application No. 32477 of 1988 2. Name of the invention Stainless steel or nickel base Welding method for alloys and carbon steel 3, relationship with the amended case Patent applicant 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Companywide representative Yutaka Saito 4, acting Person 〒100 2-4-1-5 Marunouchi, Chiyoda-ku, Tokyo Date of amendment order May 31, 1985 (all date of sending) 6 Column for detailed description of the invention in the specification subject to amendment, drawings Brief explanation column and Drawing 7, contents of amendment /″゛″：″
+,,. (1) The line 2 from the bottom of page 2 to line 15 of page 3 of the specification, "This stainless steel... is secured, etc." is amended as follows. ``The joining of stainless steel or nickel-based alloy and carbon steel has conventionally been carried out as shown in Figures 2 (A) and (B). (C) and (D). In other words, Figure 2 (A) In (c), a type opening is provided on both the stainless steel or nickel-based alloy (hereinafter referred to as high alloy) 1 side and the carbon steel 2 side, and in (c), a high alloy type austenitic stainless steel is provided to match the material of the high alloy l side. Or Ni-
The weld metal 4 was obtained using a welding material such as a so-called Inconel-based Cr-Fe alloy. Alternatively, in order to obtain a welded part of higher quality, after forming a build-up layer 3 on the groove surface of the carbon steel 2 side with the welding material such as the Inconel type as shown in (d), Weld metal 4 was obtained using a high alloy type welding material in accordance with the material of alloy 1 side. The main reason for adopting such a welding method is to prevent weld cracking and ensure the ductility and toughness of the welded part. ", ';, 31-ko (2) 4 lines from the bottom of page 23 [Figure 2 (a) (b) (mouth'
) (c)” is changed to “Figure 2 (a) (b) (c) (d)”. (3) Amend Figure 2 as shown in the attached sheet.

Claims (1)

[Claims] In welding stainless steel or nickel-based alloy and carbon steel, Cr20-30% (wt%, same hereinafter) Mo2-4 is added to the groove surface on the stainless steel or nickel-based alloy side.
．． 5%, Ni4-13%, C0.06% or less, N0.2
0% or less and (Ni+30C+20N)/(Cr+M
o) is in the range of 0.20 to 0.70, one or more build-up layers are formed with a welding material consisting of Fe and unavoidable impurities, and then welding with carbon steel using a welding material for carbon steel. A method for welding stainless steel or nickel-based alloy and carbon steel, characterized by butt welding.