Thermanit 620 is a high recovery nickel base covered electrode of the E Ni 6620 / ENiCrMo-6 type. The manufacturer developed it primarily for steels with 9 percent nickel for liquefied natural gas tanks and for steels with 5 percent nickel for liquefied ethylene. Typical applications are cryogenic storage tanks and gas carriers.
The base materials are 1.5662 (X8Ni9), 1.5680 (X12Ni5) and 1.5663 (X7Ni9). There is little spatter, the slag is easy to remove, the arc burns steadily and the bead comes out even. The electrode was adapted for work on alternating current, in order to limit the magnetic arc blow that can make work difficult when nickel steels are welded on DC.
- Classification EN ISO 14172-A: E Ni 6620 (NiCr14Mo7Fe)
- AWS classification A5.11 / SFA-5.11: ENiCrMo-6
- Current: AC/DC+
- Diameters: 2.0 / 2.5 / 3.2 / 4.0 / 6.0 mm
- Lengths: 350 mm
If the arc wanders to the side, switch to alternating current and check where the return clamp is fixed, because on 9Ni steel that is the commonest cause of trouble. A nickel alloy needs a low current and a short arc, and the pool has to be kept narrow, without weaving. Hold the interpass temperature low, because cryogenic tanks are accepted after impact testing at very low temperature. Clean the groove and the edges dry, free of grease and moisture.
