The main contribution of nickel in steel is the significant improvement of toughness and impact strength at cryogenic temperatures. Nickel is also very effective in improving the hardenability of steel because it reduces the critical cooling rate that is necessary to produce hardening on quenching. The welding of 9% Ni steel for liquefied gas applications determines to a great extent the structural integrity of the total construction. It is therefore very important to evaluate the welding processes that can be applied as well as the possibilities in type and chemical composition of the consumables. The optimum combination should provide the best mechanical properties to ensure the integrity in combination with a suitable economy. The welding processes suitable for welding 9% Ni steel are most of the arc welding processes, such as shielded metal are welding (SMAW) with covered electrodes, gas tungsten arc (GTAW) and gas metal arc welding (GMAW) with solid wire and gas, and submerged arc welding (SAW) with wire and flux. Although general information regarding the welding of 9% Ni steel has been given, a short summary is listed: Make sure that magnetism in the 9% Ni steel is not present or is as low as possible. Joint preparation on-site can be carried out by machining, plasma cutting, and oxygen cutting. If thermal cutting processes are used, all oxides and overheated material should by removed by grinding. The complete weld preparation should be cleaned with acetone or other organic solvent. Preheating is not required in general when ambient temperatures are above 15 deg C. Welding processes SMAW and SAW can be used effectively. Nyloid 2 electrodes give high productivity due to 150% recovery and 450 mm length. Use AC for SMAW to prevent arc blow. LNS NiCro 60/20 (1.6 mm)-P2000 provides good mechanical and economical results. Heat inputs from 0.5 kJ/mm to 3 kJ/mm can be used for all welding processes. An interpass temperature of maximum 150 deg C should be respected. Intermediate cleaning is recommended. The welding consumables should be handled and stored as per the supplier's recommendations.


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    Jointed Holder For Welding Electrodes

    Gilbert, Jeffrey L. | NTRS | 1991


    Steel Collet For Welding Electrodes

    Gilbert, Jeffrey L. / Gutow, David A. / Burley, Richard K. et al. | NTRS | 1992