Fabrication of 316 1.4401 316L 1.4404 Stainless Steel

The austenitic stainless steel, including the Alloys 316 and 317L, are routinely fabricated into a variety of shapes ranging from the very simple to very complex. These alloys are blanked, pierced, and formed on equipment essentially the same as used for carbon steel.

The excellent ductility of the austenitic alloys allows them to be readily formed by bending, stretching, deep drawing, and spinning. However, because of their greater strength and work hardenability, the power requirements for the austenitic grades during forming operations are considerably greater than for carbon steel. Attention to lubrication during forming of the austenitic alloys is essential to accommodate the high strength and galling tendency of these alloys.

Welding
The austenitic stainless steel are considered to be the most weldable of the stainless steel tubing. They are routinely joined by all fusion and resistance welding processes. Two important considerations for weld joints in these alloys are avoidance of solidification cracking, and preservation of corrosion resistance of the weld and heat-affected zones.

Fully austenitic weld deposits are more susceptible to cracking during welding. For this reason, Alloys 316, 316L, and 317L "matching" filler metals are formulated to solidify with a small amount of ferrite in the microstructure to minimize cracking susceptibility. For weldments to be used in the as-welded condition in corrosive environments, it is advisable to utilize the low carbon Alloys 316L and 317L base metal and filler metals. The higher the carbon level of the material being welded, the greater the likelihood the welding thermal cycles will allow chromium carbide precipitation (sensitization), which could result in intergranular corrosion. The low carbon "L" grades are designed to minimize or avoid sensitization.

High-molybdenum weld deposits may experience degraded corrosion resistance in severe environments due to micro-segregation of molybdenum. to overcome this effect, the molybdenum content of the weld filler metal should be increased. For some severe application for the 317L alloys, weld deposits containing 4 percent or more of molybdenum may be desirable. Alloy 904L (AWS ER 385, 4.5% Mo) or Alloy 625 (AWS ERNiCrMo-3, 9% Mo) filler metals have been used for this purpose.

Be careful to avoid copper or zinc contamination in the weld zone since these elements can form low melting point compounds which in turn can create weld cracking.

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