5160 heat treat

I heat treated my first batch of 5160 blades. Brought them up to 1525 degrees, oil quenched, cooled down slowly in the oil, did a 350 degree draw three times and got a rockwell C of 33. What went wrong? It was suggested to bring it up to hardening temp slowly, so I put the blades in a cold oven and brought it up to temp-was this wrong? Tested three blades, all between 30 and 33. Checked Rockwell cal-right on.

Never worked with 5160, and do not know what critical temp. is for 5160, but sonds like you didnt get it hot enough.

That said, I havent had a problem with my two favorites, 52100 and L-6. I heat with torch to non-magnetic, let temp climb a little, and emediatly quench in oil. I check critical with a magnet.

One other posibilty is your quench oil is too slow, had some problems myself with quench being to fast. Warped a few blades on that one.

Also, if your useing an oven, the steel may be cooling below critical befor you get it to the quench.

The only thing else I can think of is that you don't have 5160. Take a small piece and heat to nonmagnetic and quench in water. Then try to bend the piece in a vise, if it breaks like glass, it has enough carbon to make a servisable knife. If it doesn't, it's a low carbon steel.

I asume that you got the steel from auto springs, most are 5160, but some are medeium carbon. If you bought steel of known value, it should get hard.

hope this helps, all the ideas my poor little brain can come up with.

Bill, are you sure you've got 5160 or are you using leaf springs. I've found that not all leaf springs are 5160. When I first got started thats all I used. Thought I got a deal one time on some smaller leaf springs, can't remember the make of the vehicle they were off of but an oil quench didn't work. l525 is plenty hot to get real 5l60 hard. Try quenching in water, if that doesn't work, I'd toss them. Ray

take some scrap 5160? and use a torch to heat it up to non-magnetic and plunge in the oil and leave it in there for 30 seconds at least. then check hardness. If it isn't hard its time to get some different steel. If it is hard your oven controller may need calibration check.

Jonesy