How to weld build and reshape a backhoe

Have a fabrication shop and have been asked to weld build and reshape a pair of badly worn backhoe 4" diameter chisels. What is the alloy steel that they are made of?? I have 5/32 "case hardening" rod that I've used on grader blades with a preheat of 400-450 degrees and a slow cooling packed in sand for 48 hours. Is that the way to go with these chisels?

Thanks for any help,
Wayne