Tempering time from quench for W2

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Shipshores

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Apr 2, 2016
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I recently read that W2 should cool to room temp prior to tempering because it needs a little more time to harden fully. Anybody have more info on this?
 
First comment is that W2 is a vary wide ranging steel class. It can be from as low as .60% carbon to 1.50%. It requires a fairly long soak in HT. 10-30 minutes depending on size and thickness. Knives need 10-15 minutes minimum. It is a must that you know the exact makeup of your W2 to get good HT results. Just knowing it is W2 is insufficient.

Another peculiarity of W2 is that it hardens very high when the HT is done right. Rc 65-68 is the normal range as-quenched. The austenitization temp is determined by the carbon content. Go at the lower range ( start about 1440F) for higher carbon, and the upper range ( about 1550F) for lower carbon. The austenitization should be smooth and slow. Rapid heating is to be avoided.

Since temperature control is critical for a good HT on W2, a forge is not really the best ide. If you use a forge, the results will be less than what W2 offers. You will likely get a 1084 type product .... at best. A programmable HT oven will do the best for this steel.

W2 is a shallow hardening steel that reaches Mf around 200F - well before room temp. In a proper metallurgical HT, place it immediately in the per warmed temper oven as soon as it has cooled to 120F. This is to prevent cracking. Additionally, W2 needs higher tempers that one would think. 350F is an absolute minimum or it will crack. Normal tempering ranges for knives are between 425F and 500F. 450F is a good target for tempering knives in my opinion.
 
What happens if the steel is heated too rapidly? (and how slow is slow?) Previously I have put W2 into a preheated oven at ~ 1440 F (780C), give it 5 misn to equalise, then start heating it (initially faster, slowing down heating to usually at a rate of 300F (150C) /hour from 1350F onwards). I feel like this is relatively slow but its a recent thing Ive come across regarding heating rate during heat treat and any extra infor would be great :D
 
IMO - assuming you would like a fine grain aust matrix by using some cementites in conjunction with small% of V to pin/nucleate grain.

For Aldo's W2 use

Slow heating when pre-harden matrix is heavily martensitic - a slow trip toward critical will precip and coarsen cementite <= aha grain pinners.

Fast heating when pre-harden is mostly pearlitics and or fine spheroidized <= already have grain pinners on hand.

Soak to release just enough/eutectic-point C for aust matrix while leaving cementites as co-pinner with V -> quench. Quite simple, right ;) ok ok, simplistically speaking, that's it.
 
ndp_2010 said:
What happens if the steel is heated too rapidly? (and how slow is slow?) Previously I have put W2 into a preheated oven at ~ 1440 F (780C), give it 5 misn to equalise, then start heating it (initially faster, slowing down heating to usually at a rate of 300F (150C) /hour from 1350F onwards). I feel like this is relatively slow but its a recent thing Ive come across regarding heating rate during heat treat and any extra infor would be great :D
Click to expand...

Blunt cut pretty much showed the what and why.

In heating steel, it is the trip across Ac1 that you want to control. The 300° area before that is where you want things to be eased. Most HT regimes for complex steels have you place the blade in a pre-heated oven at 1200°F and then heat at a more leisurely pace (300°/hr is good) up through Ac1.

So, if the steel has been run through cycles that would possibly harden it and form martensite ( any cycle with a quench from above 1400°F), I would go with the slower HT. If it has been forged and normalized, or is in a known pearlitic state ( annealed by you), go with a faster rate.
 
thanks for the info! all very interesting and hopefully help me get the best out of the steel :)
 
I'm having a tough time tempering my w2 and the suggestion of 350° being minimum will help tremendously I imagine. I was also wondering if a draw temper is a good idea for w2 and if used will it diminish a hamon?

I've been getting beautiful hamons, but my temper isn't making them soft enough to prevent micro-chipping when sharpening. I'll heat to 425-450 and see if I have any luck, but a draw temper after one low cycle seems like it could work.

Suggestions?
 
Assuming that you are getting the austenizing and hardening right, you will be surprised at how hard those blades wills still be a 425-450. The lowest I have gone with a W2 blade was 375 for a kitchen knife IIRC,and it was screaming hard, but still had the things that you like about W2. I am using Don Hanson round bar which by all accounts is the best W2 out people have seen. You never need to let that stuff leave your shop any softer than 60Rc at the edge and you really don't have to worry about drawing back the spine or edge quenching, especially with a big knife, The spine is going is be tough whether you want it to be or not. I know form my own experience that at 450 temper is gong to leave you in the good zone with room to spare.
Theproduct said:
I'm having a tough time tempering my w2 and the suggestion of 350° being minimum will help tremendously I imagine. I was also wondering if a draw temper is a good idea for w2 and if used will it diminish a hamon?

I've been getting beautiful hamons, but my temper isn't making them soft enough to prevent micro-chipping when sharpening. I'll heat to 425-450 and see if I have any luck, but a draw temper after one low cycle seems like it could work.

Suggestions?
Click to expand...
 
Thanks, I'll try 450. Have you had any problems with edge chipping? They're tiny but absolutely terrible and are preventing me from raising a burr for a proper sharpen. Is this problem caused by the steel being too hard or something else entirely?
 
Edge chipping is what tells you the blade isn't tempered high enough. It can also indicate too acute an edge angle. When I get edge chipping in testing the blade, first I temper again at 10-20 degrees higher. If the edge was very acute, as on a yanagi-ba, I re-sharpen the edge at 5 degrees higher angle. That combo will likely take care of the chipping problem.
 
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