We’ve been MIG welding for years, but TIG is still relatively new to us. Fortunately much of the same ideas carry over. One thing that’s different when you’re TIG welding to cast steel is that you should both pre- and post-heat the cast metal with an oxyacetylene torch. You want the metal to be at 400-500 degrees while welding. Heat with a rosebud tip, and check the metal’s temp with a digital temp gun or an old oily glove. When your axle is hot enough, the oil should smoke off the metal instantly and residue should burn off. If the welds and axle cool too quickly, cracks may appear in your welds.