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I Forge Iron

Heat treat issues chat april 10,09

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[steve sells] What you guys been doing lately, any blade work? happy results? problems ?
[brucegodlesky] etching cable, lotsa cusswords
[jeremy k] no blade work but I built a mini hydraulic press that would work good for knife makers and less that $130.00 to build if you have steel laying around
[steve sells] : I have 2 slabs of rough cut fiddle back walnut drying under the Exhaust fan
[markb] I've got one ready to quench and treat but afaid to screw it up
[steve sells]why do you think you wil screw it up ?
[markb] I haven't done it before
[steve sells] wanna cover heat treat again ?
[markb] Well i did one and got a soft tip
[steve sells] I already wrote stickys YOU guys help Markb out,.... this chat should be a group effort.
[markb] I've spent so much time a t file and sand
[jeremy k] what steels is it?
[markb] 1084
[steve sells] 1 good start
[markb]obsessing on imperfections
[jeremy k] is that a water or oil quench steel?
[markb] oil
[jeremy k]what color is a temper color for knives - like hammers - straw?
[steve sells] that good for most. 325F to 350 is plenty for a small blade that temp barely shows color
[markb] Do you think triple quench is necessary
[steve sells] water for 1050 or lower is ok
[steve sells] I always double temper,
[markb] room temp between?
[steve sells] over night in freezer between, just top help retained austinite brealk into martensite
[steve sells] room is fine Mark and I are far enough north to let it cool
[markb] Thanks simple first
[steve sells] people like Rich Hale dont need a H/T oven they just wave the bvlade out the window and it heats up
[markb] Too hot down there
[steve sells] yup no snow either over there, weird place to live
[jeremy k] I think Rich has been having his cryo treated
[steve sells] yes but he is using high tech Stainless also
[steve sells] I low tech cryro 5160
[jeremy k] Steve is the oven the safest bet on tempering for consistency?
[steve sells] steel tube, cruched dry ice packed around the blade in the pipe, cover in acitone I get -170
[steve sells] I use wife kitchen oven for blades up to 26 inches with tang
[jeremy k] 2-3 hrs?
[steve sells] 1 to 2, I turn on oven to get to temp before hardening
[jeremy k] are the temp knobs fairly accurate?
[steve sells] after the oil quench, I wipe it off ( mainly to keep wife from killing me) and place in over before it can cool below the 400F
[steve sells] Dont trust them I use candy thermometer
[jeremy k] ahh
[steve sells] after 1 hour, I let cool in over, then place in House freezer over night then 1 more hour the next night, the retained Austine will convert to untempered martensite over time,. the cooling speeds this time up
[jeremy k] correct me - could you heat up till oil burns off a few times - is that a close temp - burning oil?
[steve sells] its not real cryo, true cryo needs a lot colder than this lol
[steve sells] oil for tempering ? I use oil at 450F for Austempering large blades so lower for normal tempering is safe
[jeremy k] ?? can't remember were I heard something about burning the oil off
[steve sells] IF you know what temp the oil burns, that can be a temp indiactor
[steve sells]if oils, and mixes, have dif flash points
[jeremy k] 1rue they do
[steve sells] mine burns at a little over 500F, I found out hard way
[jeremy k] that doesn't sound good
[steve sells] about the tempering Some people say it must come to room temp before tempering. thats only when they temper once, to help get some retained austenite to convert nefore temper, BUT I have had blades crack from getting too cold and not tempering soon enough so I temper first, at low temp 350 or so, to relax stress from the quench and temper some of the steel. after the freezer I temper again at desired temp for the target Hardness. normally 375 to 400 for hand knives, this also tempers the martensite that formed during my cold rest period by tempering right after the quench I have not had a broken blade :) like I used to get by waiting till it cooled a bit first
[jeremy k] I know a few that have broken blades by not tempering them soon enough - before dropping them
[steve sells] dropping un tempered steel >? OUCH I made 3 nice boots knives, from what should have been a left hand blade for a fencer
[jeremy k] no me - someone I know - I probably would though if I made one
[steve sells] it was a 15 inch blade, after getting bumped (by me) becauwe 3 boot knives,and some small pieces I was able to salvage something from it
[jeremy k] inside every knife is a smaller one crying to get out
[steve sells] lol if ya hear it cry during quench>? forget it lol
[jeremy k] high pitched cry?
[steve sells] pm: like a off key song the ends in a higher pitch crack, There are many way to temper some use a hot plate, some heat a bar of steel.. I am talking simple tempering small blades don't usually need differential tempering
[m_brothers] with differential tempering, how soft do you really want the spine to be?
[steve sells] if ya even done oil quench steel in water, you have heard this sound
[m_brothers] I've heard of people putting the edge of their knives in water, and using a blow torch to heat the spine to a dull red, is that to soft? like mushrooming from use over the years?
[m_brothers] i've heard and witnessed it steve :)
[steve sells] why heat spine to red ? most I have done is purple spine for a sword, cutting edge in water to keep cool
[m_brothers] it's super soft then, but i was just wondering why you would do that instead of drawing like a blue or purple for a spine
[steve sells] to red you are basically converting the back to austenite, I get asked to cover advanced things, but too many complain at mid level topics being over their heads..
[steve sells] actually this is basic heat treating anyone SHOULD know to make blades not advanced at all I have tried to build up and post notes for later reference to help people follow
[jeremy k] I don't do enough heat treating so it's always good to hear again fro me
[steve sells] MARK,, one reason your tip may be soft after H/T if you over heat is causes other problems. heat from the spine, and hear the tip/edges last to keep from over heating
[markb] why?
[steve sells] the heat will travel from back to the edge anyway, and the thinner edge heats faster than thick spine. over heating causes large grain growth, and to hot before quench also casues plate rather than lathe forms of martensite
[markb] I put that one in the forge , mistake
[steve sells] lathe is much more brittle too,

Edited by mod07
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