As you say royhall, it's going to be high carbon to make it heat treatable. In that though you've got the method to change material hardness.
To harden steel you heat to red then fast quench in water or slightly more controlled with oil.
To go the other way, you heat to red and cool as slowly as possible to anneal.
So if for example you used something like that spot welder I've posted above it will heat the whole pin probably to cherry Red without much heat being put into the surrounding component. Then leave to cool naturally before trying to get a slide hammer effect to withdraw it. You'd have been able to insulate that post weld process inuthis past with asbestos blanket, but we're not allowed such dangerous materials now!
You get a more competent tension/impact resistant joint by using the rod material as the conductor, that's why they do it like that in body shops.
If the joint comes apart, then it'll most likely be soft enough just to drill it as it'll have been annealed during the process.
