Welding process restrictions may be needed for certain materials. For example,
welded fabrications are not normally used for cast irons due to their hardenability
and tendency to crack during welding. Other examples include quenched and
tempered alloy steels, which may need restrictive heat input limitations during
welding to maintain adequate strength.
Some welding processes may not be suitable for certain materials or material
thicknesses. An example is restriction of the gas metal arc welding process used
on thin materials when the short circuit mode of transfer is used. This limitation
reduces the possibility of lack of fusion defects caused by this low heat, input
When welding is required on austenitic stainless steels, it may be advisable to
use only the low-carbon grades (e.g., 304L, 316L, etc.) or controlled heat input
weld processes to reduce susceptibility to intergranular-corrosion or
Certain contaminants on materials may be harmful during welding and should be
controlled. Zinc and other low-melting-point metals embrittle austenitic stainless
steel and nickel-based alloys during welding. Welding of zinc-coated materials
to austenitic stainless steels or nickel-based alloys will lead to weld-metal or
base-metal cracking. This problem may occur even if the zinc coating has been
mechanically removed. Use of an uncoated transition piece is recommended.
Special welding techniques to provide oxide-free welds should be considered for
materials in tritium service. The technique may include special cleaning prior to
and after welding and adhering to special welding parameters.
It is a good practice to use qualified welding procedures and qualified welding
personnel for all welded fabrication. Additionally, it is good practice to use
written procedures to perform other special processes, such as heat treating,
forming, bending, nondestructive examinations, and leak testing.
Material Corrosion and Material Degradation by Radiation . Corrosion and radiation
degradation of materials can be a serious problem. Mitigation of corrosion and material
susceptibility to radiation degradation is an important design consideration. Factors to
be considered for the control of corrosion and radiation degradation are as follows: