Fillet Welding 400 Series SS to Cr-Mo-V Alloy Steel

This should work, but bear in mind that MG600 work hardens to achieve its full strength. Also, certain grades of 400, like 405, don't like to be welded at all. You may wish to overlay the 400 with nickel to act as a cushion from the subsequent stresses of joining.

If this were my project, I would preheat the 400 to 300F minimum, and overlay with nickel at as low a temperature as I could. Cool as slowly as possible. Grind overlay to desired shape. Heat again and join to heated body. Continue heat for an hour or more and cool very slowly. The higher the temperature (up to 600F) the more likely your chances of success provided no shock cooling occurs.

A better joining alloy for this type of application that I have used is Super Alloy made by Selectrode Industries. Very strong and non work hardening. Very low temperature application. Not too tolerant of contamination. Contact them for local availibility.