Fabrication of 347 347H 1.4550 Stainless Steel

Austenitic stainless steel are considered to be the most weldable of the high-alloy steel and can be welded by all fusion and resistance welding processes. Two important considerations in producing weld joints in the austenitic stainless steel pipe are preservation of corrosion resistance and avoidance of cracking.

It is important to maintain the level of stabilizing element present in Alloys 321 and 347 during welding. Alloy 321 is more prone to loss of titanium. Alloy 347 is more resistant to loss of columbium. Care needs to be exercised to avoid pickup of carbon from oils and other sources and nitrogen from air. Weld practices which include attention to cleanliness and good inert gas shielding are recommended for these stabilized grades as well as other non-stabilized austenitic alloys.

Weld metal with a fully austenitic structure is more susceptible to cracking during the welding operation. For this reason, Alloys 321 and 347 are designed to resolidify with a small amount of ferrite to minimize cracking susceptibility. Columbium stabilized stainless steel are more prone to hot cracking than titanium stabilized stainless steel.

Matching filler metals are available for welding Alloys 321 and 347 stabilized stainless steel tube. The Alloy 347 filler metal is sometimes used to weld the 321 alloy. These stabilized alloys may be joined to other stainless steel or carbon steel. Alloy 309 (23% Cr-13.5% Ni) or nickel-base filler metals have been used for this purpose.

Machining grade 347H stainless steel is slightly tougher than that of grade 304 steel. However, the hardenability of this steel can be minimized by the use of constant positive feeds and slow speeds.Grade 347H stainless steel can be welded using most of the resistance and fusion methods. Oxyacetylene welding is not preferred for this steel.

SA 213 TP 347 347H