How to properly select welding materials when welding austenitic stainless steel
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Austenitic stainless steel has good weldability, and it can be welded using all common fusion welding methods. However, due to the characteristics of the electroslag welding heat process, the intergranular corrosion resistance of the joint is reduced, and severe knife-edge corrosion tends to occur near the weld line; as a result, it is rarely used. Gas shielded CO2 welding has not been widely adopted due to the strong oxidizing nature of CO2 gas, which causes severe loss of alloying elements; currently, the practical welding methods are shielded metal arc welding, submerged arc welding, and argon arc welding. The selection of welding materials for these methods is shown in Table 19. Table 19 Selection of welding materials for welding austenitic stainless steels – Welding processes: Manual arc welding, Submerged arc welding, Tungsten inert gas arc welding. Types of electrodes, wires, and fluxes; electrode/wire codes: 1Cr18Ni9TiE0-19-10-16, R0-19-10-15, E0-19-10Nb-16, R0-19-10Nb-15. A102, A107, A132, A137. H0Cr20Ni10Ti, HJ260, H0Cr20Ni10Ti. 0Cr19Ni9, E0-19-10-16, R0-19-10-15, A102, A107 ———— 0Cr18Ni9Ti, E0-19-10Nb-16, R0-19-10Nb-15, A132, A137, H0Cr20Ni10Ti, HJ260, H0Cr20Ni10Ti. 0Cr18Ni9Ti, E0-19-10Nb-16, R0-19-10Nb-15, A132, A137 ———— 00Cr18Ni10N, E00-19-10-16, A002, H00Cr21Ni10, HJ260, H00Cr21Ni10. 00Cr19Ni11, E00-19-10-16, A002 ———— 0Cr17Ni12Mo2, E0-18-12Mo2-16, E0-18-12Mo2-15, A202, A207, H00Cr19Ni12Mo2, HJ260, H00Cr19Ni12Mo2. 0Cr18Ni12Mo2Ti, E00-18-12Mo2-16, E00-18-12Mo2Nb-16, A022, A212, H00Cr19Ni12Mo2, HJ260, H00Cr19Ni12Mo2. 0Cr19Ni13Mo3, E0-19-13Mo3-16, A242 ———— 0Cr18Ni12Mo3Ti, E0-18-12MoNb-16, A022, A212, H0Cr20Ni14Mo3, HJ260, H0Cr20Ni14Mo3. 00Cr17Ni14Mo2, E00-18-12Mo2-16, A022, H0Cr20Ni14Mo3, HJ260, H0Cr20Ni14Mo3. Last edited by JLH on 2008-3-3 22:21.]
GMAW of austenitic stainless steel has the advantages of a small heat-affected zone, easy quality control, and suitability for various welding positions as well as different process requirements for sheet thickness. Welding electrodes are divided into two main categories: acidic titanium-calcium type and basic low-hydrogen sodium type. Low-hydrogen sodium-type stainless steel electrodes have high resistance to thermal cracking, but their formability is inferior to that of titanium-calcium type electrodes, and their corrosion resistance is also poorer. Titanium-calcium type electrodes have good processability and are widely used in production. Since the resistivity of austenitic stainless steel is more than 4 times that of low-carbon steel, the resistive heat generated during welding is high, causing the flux coating to turn red and crack easily. Therefore, for electrodes of the same diameter, the welding current should be reduced by about 20% compared to that used for low-carbon steel. The length of such electrodes should also be shorter than that of carbon steel electrodes of the same diameter; otherwise, the rapid reddening and cracking of the flux coating during welding will result in a loss of protection, making welding impossible. During welding, the welding rod should not be moved sideways; a low current and fast welding speed should be used. The weld formed in one pass should not be too wide, ideally not exceeding 3 times the diameter of the welding rod. During multi-layer welding, the slag must be completely removed after each layer is welded; the temperature between layers should be below 60°C. Welds that come into contact with corrosive substances should be welded last, in order to prevent a decrease in corrosion resistance due to repeated heating. After welding, forced cooling measures can be employed to accelerate the cooling of the joint. At the start of welding, do not initiate the arc randomly on the welded parts, to avoid damaging their surface and affecting their corrosion resistance.