The welding of copper and stainless steel is very common.
There are some difficulties in welding, mainly as follows:
Welding is very sensitive to copper penetration cracks.
To prevent penetration cracks:
Firstly, the process should be reasonably selected and the welding line energy should be small;
Secondly, select appropriate filler materials, control the elements that are easy to produce low melting eutectic, such as S, P, O, etc., and add Al, Si, Mn, V, Mo, Ni and other elements to the weld.
Manual arc welding
When manual arc welding is used for copper and stainless steel, it shall be noted that if austenitic stainless steel electrode is selected, it is easy to cause thermal crack;
It is better to choose nickel copper welding rod (70% nickel + 30% copper), or nickel base alloy electrode, and copper welding rod (T237) can also be used;
During welding, the welding process of small diameter and small current fast welding without swing shall be adopted, and the arc shall be biased to the copper side to avoid penetration cracks. See Fig. 1 for welding process parameters.
Submerged arc welding
When submerged arc welding is used for copper and stainless steel, the main problems are cracks and pores;
Before welding, the surfaces of weldments and welding wires shall be strictly cleaned.
For weldments with a thickness of 8 ~ 10mm, a 70 ° V-shaped groove is generally opened;
The groove angle on one side of pure copper is 40 °, and the groove angle on one side of stainless steel (1Cr18Ni9Ti) is 30 °;
The flux is HJ431 or HJ430 (baked at 200 ℃ 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;
Select larger welding line energy and use cooling water type copper inch pad.
The welding wire points to the copper side and is 5 ~ 6mm away from the groove center.
See Fig. 2 for the process parameters of common submerged arc welding of pure copper and stainless steel.
Fig. 2 process parameters of submerged arc welding of pure copper and stainless steel
|Weldment||Joint form||Thickness mm||Welding wire diameter mm||Welding current A||Welding voltage
|welding speed mm/s||Wire feeding speed cm/min|
Argon tungsten arc welding (TIG)
Good welding joints can be obtained when TIG welding is used for copper, its alloys and stainless steel, but satisfactory results can be achieved only by mastering appropriate processes;
Their welded joints are basically butt joint and corner joint on the groove.
There is no groove on the copper side, and it is best to open half a V groove on the stainless steel side.
Before welding, clean the surface of the weldment, apply flux (70% H3BO3, 21% Na2B4O2, 9% CaF2) on the front and back sides, and conduct welding after drying.
Try to use Monel alloy (70% Ni, 30% Cu) or copper alloy welding wire containing silicon and aluminum, such as HS221, QAI9-2, QAI9-4, QSi3-1, QSn4-3, etc;
During TIG welding, the tungsten arc is biased to the copper side, and the distance from the groove center is about 5 ~ 8mm to control the melting amount of stainless steel;
Most welding materials are copper welding wire or copper nickel welding wire, or bronze welding wire containing aluminum, which is to improve the mechanical properties of weld metal and prevent copper penetration crack;
Fast welding without swinging is usually adopted; When argon arc welding brazing process is adopted, the melting amount on one side of stainless steel shall be reduced as much as possible, which is equivalent to a brazing connection for stainless steel and a fusion welding connection for copper side.
The process parameters of TIG welding between brass and stainless steel are shown in Fig. 3.
Fig. 3 TIG welding of brass H62Sn-1 and stainless steel 1Cr18Ni9Ti
|Weldment thickness mm||Tungsten electrode diameter mm||Tungsten electrode extension length||Nozzle diameter mm||Welding current a||Argon flow L / min|
When gas welding is used for copper and stainless steel, the flame temperature of gas welding is not as high as that of arc, which may lead to uneven melting of base metals on both sides due to different melting points, widening of heat affected zone, increased deformation and even non fusion;
When welding pure copper and 18-8 stainless steel, welding wires such as HSCuZn-2, HSCuZn3 and HSCuZnNi are usually selected, and 301 welding powder (brazing powder) or borax are used for neutral flame welding;
If the weld is long, a layer of brass can be deposited on the groove surface on one side of stainless steel before welding.
When copper and stainless steel are brazed, the solder used is mainly silver based solder, such as HL302, HL309, HL312, etc.
The process method is similar to that of general brazing.
It should be noted that the temperature on one side of stainless steel should not be too high, and the heat source is biased towards the copper side during heating.