1.Overview

The welding of copper and stainless steel is often met, the welding is difficult, the main performance is: when it is welded, it is very sensitive to the penetration crack of copper, in order to prevent the formation of the penetration crack, first of all, we must choose reasonable technology, secondly, the suitable filler material is selected to control the low-melting eutectic elements such as S, P, O and so on. AL, SI, MN, V, Mo, Ni and so on are added to the weld.

2.Welding method

1)When shielded metal arc welding copper and stainless steel use shielded metal arc welding, pay attention to if choose AUSTENITIC stainless steel welding rod easy to cause hot crack; Best Choice nickel-copper welding Rod (70% nickel + 30% copper) , or nickel-based alloy welding Rod, can also be used copper welding Rod (T237) ; Small-diameter, low-current, fast, non-oscillating welding process is adopted, and the ARC is biased to the copper side to avoid the formation of penetrating cracks.

2)The main problems of submerged arc welding of copper and stainless steel are cracks and blowholes, the surface of welding parts and welding wires should be cleaned strictly before welding, 8 ~ 10mm thick welding parts should have 70 ° v Groove, the angle of breakage of pure copper side should be 40 ° , the groove angle of one side of stainless steel (1Cr18Ni9Ti) is 30 ° , the welding flux is HJ431 or HJ430(200 °C for 2H) , the welding wire is generally copper welding wire, and 1 ~ 3 nickel wires or nickel-copper alloy wires are placed in the groove, cooling water type copper inch pad is used. The welding wire points to the copper side and is 5 ~ 6 mm from the center of Groove. The Common Technical Parameters of submerged arc welding of pure copper and stainless steel are shown in figure 2.

3)Tig Welding of copper and its alloy to stainless steel can obtain good welding joint, but we should master proper technology to get satisfactory results Their welded joint form of basic groove with Butt and angle connection two, copper side not open groove, stainless steel side had better open half V groove. Before welding, clean the surface of the welding piece and apply flux (70% h3bo3,21% NA2B4O2,9% CAF2) on the front and back of the welding piece. After drying, use the welding wire as far as possible (70% NI, 30% cu) , or the copper alloy welding wire containing silicon and aluminum, such as: HS221, QAl9-2, QAl9-4, QSi3-1, QSn4-3, etc. In Tig welding, the tungsten arc is inclined to the copper side about 5 ~ 8 mm from the center of Groove to control the melting of stainless steel, and the welding materials are mostly copper wire or copper-nickel wire, or bronze wire containing aluminum, this is to improve the Mechanical Properties of the Weld Metal and to prevent penetration cracks in the copper. Fast welding is usually used without swinging. When Argon Arc welding-brazing is used, the melting of the stainless steel side is minimized, equivalent to a brazing joint for stainless steel and a fusion joint for copper. The technological parameters of TIG welding of brass and stainless steel are shown in Fig. 3.

4. When gas welding copper and stainless steel, because the flame temperature of gas welding is not as high as that of arc welding, the base metal on both sides may not melt evenly due to different melting points, the heat-affected zone becomes wider, the deformation becomes larger, and even the base metal is not fused When welding pure copper to 18-8 stainless steel, wire such as HSCuZn-2, Hscuzn3, Hscuznni is usually used, and neutral flame welding with 301 welding powder (brazing powder) or borax is used, and then we weld it.

5. When brazing copper and stainless steel, the brazing filler metals used are mainly silver-based filler metals, such as HL302, HL309, HL312, etc. . The processing method is similar to that of general brazing. 

Source: Welding Technology