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Forming, machining, and welding of stainless steels

Hot and cold forming
Hot working should be carried out within the temperature ranges given in the table below.
Like other austenitic steels, heat-resistant steels can also be formed in cold condition.  However, as a result of their relatively high nitrogen content, the mechanical strength of certain steels is higher and consequently greater deformation forces will be required.

Machining
The relatively high hardness of austenitic steels and their ability to strain harden must be taken into consideration in connection with machining. For more detailed data on machining, please refer to the "Machining guidelines for …" series of brochures, which can be obtained on request.  Separate leaflets are available for all of the steels but 4828 and 4833. For these, the guidelines for 4845 are probably the most appropriate.

Welding
The steels have good or very good weldability and can be welded using the following methods:
· Shielded metal arc (SMA) welding with covered electrodes
· Gas shielded welding, e.g., GTA (TIG), plasma arc, and GMA (MIG).  Pure argon should be used as the shielding gas
· Submerged arc (SA) welding.

To ensure weld metal properties (e.g. strength, corrosion resistance) equivalent to those of the parent metal, a filler material with an identical composition should preferably be used.  In some cases, however, a differing composition may improve e.g. weldability or structural stability
Gas shielded welding has resulted in the best creep properties for welds.
In addition to documents covering welding issues of a general nature, more specialist information is available in the brochures entitled "How to weld Outokumpu stainless 253 MA" and "How to weld Outokumpu stainless 353 MA", which are also available on request from the company.

Heat treatment
Heat treatment after hot or cold forming, or welding will often not be needed, because the material will be exposed to high temperatures during service.
However, if that is not sufficient, the best option would be a proper solution annealing, with the second best choice being a stress relief annealing.  Suitable temperature ranges for both treatments are given in the table below.
Components, in which the material has become embrittled during service, will benefit from a "rejuvenating" solution anneal before any maintenance work, e.g. straightening or repair welding, is carried out.  This treatment will, however, not fully restore the original materials properties  -  certainly not if the embrittlement is caused by external carburization and/or nitridation.