Welding process of ferritic stainless steel

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Steel grades that belong to ferritic stainless steels include 0Cr13A1, 1Cr17, 1Cr28, 0Cr17Ti, 1Cr25Ti, 1Cr17Mo2Ti, etc. The welding process for ferritic stainless steel is as follows: (1) Weldability – When welding ferritic stainless steel, the rapid growth of grains in the heat-affected zone, the brittleness at 475°C, and the precipitation of σ-phase not only cause brittleness in the joint but also increase the tendency for cold cracking. Intergranular corrosion occurs when rapid cooling takes place near the fusion line at temperatures above 1000°C, but it can be eliminated by heating to 650–850°C and then cooling slowly. Since ferritic steel does not undergo phase transformation during heating and cooling, once the grains have grown, they cannot be refined through heat treatment. ⑵Welding process 1) Preheat the welded parts to 100–150°C during welding; the higher the chromium content, the higher the preheating temperature required. 2) Chromium stainless steel electrodes or chromium-nickel austenitic electrodes can be selected separately. When using chromium-nickel austenitic welding electrodes, pre-welding heating and post-weld heat treatment are not required. Welding electrodes for ferritic stainless steel are shown in Table 22. Table 22: Selection of electrode types for welding ferritic stainless steels – requirements for joint properties, as well as electrode types for preheating and post-weld heat treatment.
Types: 1Cr17, Cr17Ti – resistant to nitric acid and heat; Electrodes: E0-17-16, E0-17-15, G302, G307. Preheating before welding: 120–200°C; post-weld tempering at 750–800°C.
Cr17, Cr17Ti, 1Cr17Mo2Ti – to improve weld plasticity; Electrodes: E0-19-10-15, E0-18-12, Mo2-15, A107, A207. No preheating or heat treatment required.
1Cr25Ti – for oxidation resistance; Electrode: E1-23-13-15, A307. No preheating required; post-weld tempering at 760–780°C.
1Cr28, 1Cr28Ti – to improve weld plasticity; Electrodes: E2-26-21-16, E2-26-21-15, A402, A407. No preheating or heat treatment required.
3) Use a low welding energy input and weld without oscillation. During multi-layer welding, the interlayer temperature should be maintained above 150°C. Continuous welding should be avoided. 4) After welding, tempering at 750–800°C is carried out to improve plasticity and enhance corrosion resistance. Rapid cooling after tempering can prevent the formation of the σ phase and brittleness at 475°C. For ultra-low carbon, high chromium ferritic stainless steels such as 00Cr26Mo1 and 00Cr30Mo, there are no specialized welding electrodes available at present; welding can be carried out using E1-23-13-26 (A302) and E2-26-21-16 (A402) electrodes.