HT for 1050?

M

Martin Brandt

Active Member
Several yrs. back we came across some 3/16 x1 1/4x38"CR steel in quantity at our local scrap yard. We bought several pcs. and it sparked hicarbonish enough to test. Oil quench was disappointing, so I tried water and it hardened well. The price was right and large quantities were available so I bought a couple hundred lbs. Had it spectro tested and came up : C-.521,Mn-.628,Si-.061,Cr-.216,Ni-.047,B.0001,Fe98.35, everything else .0 to .00somethings. It gives a great Hamon, and seems to be 1050. Oil quenching in P50 doesn't seem to get as hard as water quenching with the frustrating tink just about when you are ready to pull it out of water. Any thoughts on getting more out of the P50, or safer water first and P50 endings?? Also in trying to make a couple of 9"Leuku's and using a torched edge I've ended up with 1/2" of tip lift in what should be straight back blades. I figured next to quench a fully heated blade and draw the back after quenching and tempers to avoid the curvature. Any thoughts on a nice quenchline but avoiding the samurai curve. P.S. I do have a Rc tester and if I remember correctly water gave a couple points more hardness on samples.:les:
 
It has a little more chromium than I would expect from 1050 but it should be able to make a tough knife blade, something like a big chopper or a sword. From what you have said the chromium isn't enough to pull the nose of the curve much to the right so you are probably in a situation where you have less than a second for the temperature to dwell at the nose of the curve. I take it by P50 you mean Parks #50. From what I understand that is about the fastest quenching oil out there. If that isn't giving a good hardness then you may have to just rely on water or brine and expect the occasional broken blade, though you can reduce that by sanding out to something like 400 grit and making sure there are no stress risers in the blade. Regardless of the quenchant something with only around 0.50% carbon in it is only going to form so much hardness through martensite formation and is really minimal for knife making.

Martensite will give a larger crystal than pearlite and it can force a curve away from the martensite in a blade so your idea of doing a full austinization and quench on the blade and then drawing the spine back would be the way to go if you wanted a softer and tougher spine. Personally I would do a full austinization and quench and temper at about 325°-350° and test the edge. Be aware also that depending on the thickness of the blade it may give you an "automatic" hamon and you'll be back to square one anyway with a soft spine, hard edge, and an upward turn at the tip.

Doug
 
You will probably get a hamon regardless of what you do based on the carbon content. If you are worried about broken blades, try three or 4 seconds in brine, then finish in oil. To avoid the curve in hardening, maybe try spine first and see how that works?
 
Me2, No I have tried forge heating the whole blade as well. When I torched the edge I was going for a hard edge/soft back. I quenched in hot water, and the blade split down the line between the hot edge and not hot back. The blade was a 9" Leuku, (a scandanavian chopper), which has a straight back and edge with a round skinning tip. The next one was same type blade, heated through, Quenched in hot water 3 sec. then into Parks 50. It had minimal tip lift, but cracked at the edge as I tried straightening out a little bit of warp. It was cooler than I thought it was. Haven't had time to try again yet, but I will as son as work slows down for the winter.
 
With either the torch or the forge, how are you judging the temperature to quench?
 
the steel you found has similar composition to the SAE1050M we use at the office. We forge it at 1800F, let it cool, shot blast, oil size, then cold forge it at room temperature. we then send to parts to the next building where they are machined and heat treated. heating before forging and after machining is my induction, after heat treat they are quenching in a water/polymer mix, then heated for temper. they wouldnt give me all the details, trade secrets and such. i know when water quenched the parts get very hard, will skate a file, and if they make it to the cold forge, they will explode.
 
me2, I am using the magnet test, then just a quick trip back to the forge for a few more degrees, then quench. Yes it will skate a file no problem when fully hard. And I wouldn't expect it to be a high performance skinner, but it should hold a fair edge and be useable. It does give a very nice hamon, and an even nicer one if clay quenching is done well.
 
If you're happy with the performance, then that's great. If you're after just a little more, and what knife maker isn't, you might try heating it just a little higher, like around 1475-1500. The magnet test is just at the fully austenized temperature for 1050 in ideal circumstances. Lower carbon contents than 0.8% need slightly higher temperatures to reach full hardness. Too low a temperature will leave ferrite in the mix. Again, not saying you have ferrite, but the magnet plus a few degrees is right on the line.
 
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