Nickel alloy welding, what are the matters needing attention!

1 Welding method

TIG welding, MIG welding and plasma welding and other non active gas arc welding is more suitable, can also use manual arc welding or electron beam welding. Gas welding due to carbon immersion, oxidation, it can not be used. The heat affected zone of submerged arc welding is too large and should not be used as much as possible.

2 Welding rod

The welding rod used shall be of the same material as the base metal. See Table 6 for the specifications of welding rods. When welding with dissimilar metals. The welding rod is usually made of the same material as the Hastelloy side. Specific according to the welding process qualification test to determine.

3 Preparation before welding

1) Before welding, the wrong side and groove form of the plate shall be confirmed.

2) Whether it is positioning welding or real welding, acetone should be used to remove grease, dirt and other foreign matter on the surface of the groove and the base metal near the groove.

3) The welding rod should also be cleaned before welding.

4) In principle, the groove processing adopts the form of mechanical processing, and the plasma cutting is to use a grinding wheel to remove the oxide skin or heat-affected zone. Heat affected zone to cut off more than 3mm.

5) Compared with austenitic stainless steel, the fluidity of molten metal is poor, so the groove opening should be larger.

Table 6 Welding Materials of Hastelloy Alloy

4 Welding construction

1) Tack welding is the same as real welding. It is necessary to fully remove the oxide scale and other attachments or harmful defects generated during tack welding.

2) If the inactive gas back protection is not carried out, the weld on the reverse side will be strongly oxidized and the weld formation will not be good. Depending on the shape of the base material, a tool for protecting the back surface is used.

3) The welding position shall be flat welding as far as possible. Horizontal welding and vertical welding can be used for difficulties in flat welding, and overhead welding should be avoided.

4) Preheating is not required, and the temperature between layers should be controlled below 150°C as much as possible. Each layer shall use stainless steel brush or soft grinding wheel to remove oxidation slope, etc.

5) In order to control the welding heat, the welding rod cannot swing back and forth, and try to run straight.

6) Due to the possibility of high temperature solidification and cracking, attention should be paid to crater treatment.

Representative examples of welding conditions are shown in Table 7.

Table 7 Welding process of Hastelloy alloy

5 Post-weld heat treatment

Hastelloy alloys other than Hastelloy B and C can be used in the welded state except in special cases. The post-weld heat treatment is carried out by solid melting treatment.

6 Inspection of weld

Welder qualification and welding procedure evaluation shall be carried out, and the test results shall be recorded in WQR and PQR.

Although welds can be inspected like stainless steel, penetrant testing and radiographic testing can be used as non-destructive testing, but magnetic particle testing or ultrasonic testing cannot be used.