Welding of 304H Stainless Steel

The 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. The Alloys 304 and 304L are typical of the austenitic stainless steel. Two important considerations in producing weld joints in the austenitic stainless steel are: preservation of corrosion resistance, and avoidance of cracking.

A temperature gradient is produced in the material being welded which ranges from above the melting temperature in the molten pool to ambient temperature at some distance from the weld. The higher the carbon level of the material being welded, the greater the likelihood that the welding thermal cycle will result in the chromium carbide precipitation which is detrimental to corrosion resistance.

To provide material at the best level of corrosion resistance, low carbon material (Alloy 304L) should be used for material put in service in the welded condition. Alternately, full annealing dissolves the chromium carbide and restores a high level of corrosion resistance to the standard carbon content materials.

Weld metal with a fully austenitic stainless steel structure is more susceptible to cracking during the welding operation. For this reason, Alloys 304 and 304L are designed to resolidify with a small amount of ferrite to minimize cracking susceptibility.

Alloy 309 (23% Cr – 13.5% Ni) or nickel-base filler metals are used in joining the 18-8 austenitic alloys to carbon steel.