How To Weld Cast Alloy. Cast iron can certainly be welded and brazed with TIG brazing included. Use only low current which will minimize residual stress and admixture.
You can heat the casting anywhere in the range of 500-1200 degrees before welding dont go beyond 1200 degrees Fahrenheit. Make short approximately 1 long welds. In this way we can avoid overheating as well as creating residual stresses which can cause a fracture in the cast iron.
The most important thing to remember when welding cast iron is to move low and slow.
For welds needing deeper penetration an. AC TIG weld the crack filling it with new metal. At a time work about an inch and wait for at least 45 seconds between two segments. If you preheated the part wrap the whole component up after welding to slow down cooling.