Question I need answered is: What kind of steel to they make car frames out of?



Back Story:
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I'm pretty new to welding and a guy at work asked me if I'd fix a small crack in his car frame. Claimed the auto repair shop wouldn't do it citing liability. I haven't seen the crack yet but his description goes like this:

Backed into something with his bike carry attached and the force carried through the carry and the class II receiver enough that it snapped one of the bolts that hold the hitch to the frame and craked the frame around the hole.

As described it doesn't sound bad but I've been around long enough that that might also mean he should not say anything to a dealer and trade this car in for a new one. :-)

If it IS just a small crack out of the bolt hole I don't think it's a big deal to drill the end of the crack and then weld back to the hole. Maybe even weld on a small patch.

Any experienced thoughts out there?