my metals class is making some cromoly punches and need advice on heat treating

Good Morning,

Look up the 'Heat Treating' Charts. Pay attention to the "Blue Brittle Warning" or you will get hurt.

Neil

Great............ so happy for you.   Punches for what?  What sort of facilities do you have to HT?  What size are they?  Are they 4140 or are they just "chrome moly" (which could also be spring steel).  More info and maybe we can help you.

Phil

 

we dont have much for heat treating we got oxy torches and im bringing my forge from home

the steel is 4140

Honestly the intended use would tell us the most as far as how to treat them,depending on what they will be used for and the size of them the answer could vary a lot.4140 is "supposed" to be hardened in oil...but in thick sections can be water quenched...then the application? if they are simple blacksmithing punches they may not need to be hardened at all.

the punches are just normal old center punches and are 25mm diameter

Sounds like you could oil quench them and temper to straw,then experiment from there IF they didnt get hard enough from the oil quench.

Try heating one with the oxy to dull red for about an inch back from the end, oil quench till cold, then burn the oil off with the oxy.  Test.  If Ok do the rest the same way.

Phil