"Preheat temperatures may be 150 F (83 C) less than given above for carbon steel
weld materials, however, should not be less than 60 F (16.C).
"Austenitic Stainless Steel Weld Material on Austenitic Stainless Steel. A nominal
60 F (16 C) preheat is necessary.
"Austenitic Stainless Steel Weld Material on M@rtensitic Stainless Steel (CA6NM).
The minimum preheat should be as follows:
4 in. (102 mm) material thickness ............................150 F (66 C)
4 in. (102 mm) material thickness ............................250 F (121 C)
In restricted areas, preheat should be increased by 100 F (56 C).
Stellite 21 Weld Material. A nominal 60 F (16 C) preheat is necessary.
Preheating may be done using:
Oxy-acetylene torches (for small areas)
Propane or butane
Electric strip heaters with insulating blanket
Where there are large areas to be preheated, insulating blankets are needed to
protect personnel during the subsequent welding. Preheat temperature should be
monitored using a contact pyrometer or temperature-indicating crayons.
During preheating, care should be taken that the center of a blade is not heated in a
small concentrated area. To allow for expansion of the material, heat should be
applied starting from the outer edge of the blade.
Weld Application. Weld application should be aimed at achieving good quality weld
with minimum residual stressing and also at keeping distortion to an absolute
minimum. This can be accomplished by:
Apply no more than 1/8 inch (3 mm) weld material per pass.
Limit heat input to the runner. The maximum interpass temperature should
be within 200 F (111 C) of the minimum preheat temperature. Temperature
should be monitored with a contact pyrometer or temperature-indicating
crayons. In addition, the area about 4 inches (102 mm) from the weld should
not become to warm to touch.