Production process of Hastelloy C-22

Wrought forms of alloy C-22 are delivered in solution heat processed conditions as a standard production. The standard solution heat processing comprising of heating at 2050oF after quick air cooling or by water. Components that have been hot formed or vigorously cold developed must be solution heat processed before further development or installation.

Alloy C-22 offers supreme forming properties. Cold forming is a recommended procedure of forming. Due to its good ductility, it can be easily cold processed. The alloy is normally stiffer than austenitic stainless steels. Hence more energy is needed during cold forming.

Welding

Hastelloy C-22 is readily welded by gas tungsten arc, gas metal arc and shielded metal arc welding methods. It offers welding properties equivalent to Hastelloy C276 and Alloy C4. It is not fit to work with submerged arc welding due to large heat supply to the base metal and slow quenching of the weld. Base metal development includes complete cleaning of joint surface and neighbor area prior to welding. Grease, oil, crayon marks, sulfur compounds and other foreign matter must be eradicated.

Similar composition filler metal is preferred for welding of Hastelloy C22. For gas tungsten arc and gas metal arc welding, Hastelloy C22 filler wire is preferred. For shielded metal arc welding, C-22 covered electrodes are preferred.

Various corrosion damages are connected with welds. Consistent, economical and practical solutions to corrosion weld problems involve the use of Hastelloy C-22 filler metal. Tests were performed in a simulated incinerator off-gas scrub solution for a month. Inconel 625 received vigorous base metal and weld metal corrosion in this condition. Average corrosion of the base metal was noticed on Al-6XN alloy. Hastelloy C22 didn’t receive any corrosion.

A concern about alloy’s sensitivity to intergranular corrosion is the heat affected region of weldments. Welded test coupons of alloy C-276 and C22 were subjected to an oxidizing sulfuric acid process solution. Alloy C276 experienced unusually severe base metal, weld metal and heat affected region corrosion in this specific environment. Actually just 1/3^rd of the sample thickness in the heat affected region could withstand the corrosion. Alloy C276 alloy is nominally corroded to this level in other environment. There was nominal corrosion on the alloy C22 specimen.

For machining of Hastelloy C22 bar, following guidelines should be used. Specific details may vary depending on circumstances of the job.

Drilling- Carbide tools of C2 alloy should be not be used however tipped drills may be significant on rigid setup of moderate depth. The web should be thinned to decrease thrust. Use 135o included angle on point, gun drill can be used.  Oil or water base coolant can be used. Coolant feed carbide tipped drills may be suitable in some processes.

Normal Roughing, Turning or Facing- Grades C2 and C3, negative rake square insert, 45 degree SCEA, 1/32 inch nose radius.

Finishing, Turning or Facing- Grade C2 or C3, positive rake square insert, if feasible, 45 degree SCEA, 1/32 inch nose radius.