What steel bars should I order? in Blacksmithing, General Discussion Posted August 25, 2011 Concerning the rebar no holding heat: what I meant was the rebar cools WAY too fast. I also learned not to put a hammer to it when it's black heat. I also found that yes, quenching rebar leads to cracking and/or shattering. I was told about that, but had forgotten. It doesn't matter because I was just practicing anyway.