Ground Flat Stock

[BazyleParticipant @bazyle]

If the tools are going to be hand held so that round would do it might be worth trying car bits like half shafts and track rods.

[Anonymous]

Posted by Dinosaur Engineer on 03/08/2015 02:25:17:

I notice that this steel in this link is oil hardening

Quite so, and I agree that the ideal would be to use a proper quenching oil. However, I suspect that using some random oil from the local supermarket chain isn't any better than brine. So I'll stick to brine. As of yet I haven't had any cracking problems. Here is the last item I made from gauge plate and quenched in brine:

Andrew

[jaCK HobsonParticipant @jackhobson50760]

Posted by Martin Kyte on 03/08/2015 11:45:24:

I understand it is the faster the quench the more Martensite is produced

A generalisation that hides some truly useful behavior.

It depends on the steel and the quench rate. You need to look at the TTT curve for the particular steel. For many steels, if you quench quick enough at the start then you will get metastable austenite which will turn to martensite once a low enough temp is reached. You can quench to black heat, austenite (which is sort of ductile) and hit it with a hammer to straighten, then quench to room temp to convert to martensite (which will now shatter like glass if you hit it with a hammer).

If you quench at at least a minimum rate, then the % martensite produced is more dependent on final lowest temp, than any increase in quench rate.

[VicParticipant @vic]

So which will yield a harder tool, brine or oil? Have to say I've used both in the past and brine is obviously cleaner and doesn't catch fire! Also should both quenchants be cold (how cold is cold!) or warm before the steel is put in it.

Thanks in advance.

[egaParticipant @ega]

Andrew Johnston:

Great-looking cutter! Might you give a little more information? I'm intrigued by the apparent Rippa effect on the relieved flanks of the teeth.

[jaCK HobsonParticipant @jackhobson50760]

It depends on lots of things

For 01, which is your most common flat tool stock, oil quench is fast enough to get you past the pearlite nose in the TTT diagram. So oil is all you need.

Faster quench will just introduce risk of distortion or cracking. That risk is less for small parts.

Cold water quenches faster than hot.

Hot oil quenches faster than cold.

For O1 and smaller or thinner parts, cheap veg oil will do fine.

Low temp heat treat salts are often best of all (similar to hot blue salt and similar to chemicals you might need for explosives). These are at high temp when you quench – just above the temp at which martensite starts to form – but they quench really fast. So quench, hold a little while to even out the temp (and stresses) then cool further.

Molten lead baths were used no so long ago. Pure lead melts a little high so it was probably some alloy. Lead doesn't quench as fast as salt, and it is a bit more risky from health and safety point of view.

Heat treating develops a pragmatic view of heath and safety!

O1 is designed to be easy to heat treat. You can get something hard with a wide range of treatments. For best results, do exactly what it says on the tin/packaging paper (I've spent many hours of research to come to that conclusion).

Edited By jaCK Hobson on 05/09/2015 10:56:13

Edited By jaCK Hobson on 05/09/2015 11:01:38

[David HaleyParticipant @davidhaley39295]

Posted by jaCK Hobson on 05/09/2015 10:53:49:

It depends on lots of things

For 01, which is your most common flat tool stock, oil quench is fast enough to get you past the pearlite nose in the TTT diagram. So oil is all you need.

Faster quench will just introduce risk of distortion or cracking. That risk is less for small parts.

Cold water quenches faster than hot.

Hot oil quenches faster than cold.

For O1 and smaller or thinner parts, cheap veg oil will do fine.

Low temp heat treat salts are often best of all (similar to hot blue salt and similar to chemicals you might need for explosives). These are at high temp when you quench – just above the temp at which martensite starts to form – but they quench really fast. So quench, hold a little while to even out the temp (and stresses) then cool further.

Molten lead baths were used no so long ago. Pure lead melts a little high so it was probably some alloy. Lead doesn't quench as fast as salt, and it is a bit more risky from health and safety point of view.

Heat treating develops a pragmatic view of heath and safety!

O1 is designed to be easy to heat treat. You can get something hard with a wide range of treatments. For best results, do exactly what it says on the tin/packaging paper (I've spent many hours of research to come to that conclusion).

Edited By jaCK Hobson on 05/09/2015 10:56:13

Edited By jaCK Hobson on 05/09/2015 11:01:38

Some very sound advice! The instructions on the packaging we try to keep as simple as possible to ensure you get good results with minimal distortion and ease of use at home. It starts to get a bit more complicated when you start heat treating some the D2 and Niolox at home as more sensitive equipment is needed to get accurate results.

[VicParticipant @vic]

Oil it is then, Sunflower or Olive?

[Peter TuckerParticipant @petertucker86088]

Posted by Vic on 05/09/2015 15:05:59:

Oil it is then, Sunflower or Olive?

Olive; quenching would be the only thing it could be good for!

Peter.

[VicParticipant @vic]

Well I emptied what was left in the sunflower oil bottle and topped up with olive. Seemed to work well, just a quick pop and a flame and then just lots of bubbles. Smelt a lot nicer than engine oil! First blade cleaned off easily enough and seems pretty hard.

[jaCK HobsonParticipant @jackhobson50760]

This may be interesting… supposed to be a talk about material science and heat treat of steel:

http://slbbhi.co.uk/?p=1289

The bloke has no credentials, doesn't work in any relevant industry, and has never given a public talk of any sort before so it could be a disaster – maybe you could just go along and have fun heckling and picking holes in it. You also have to listen to some club's AGM summary and there is a small entry fee. I bet he's going to come to the same conclusion though… just follow the directions on the pack.

(OK, so I may have some connection to the event)

[jaCK HobsonParticipant @jackhobson50760]

oops, I can't even post a link properly: **LINK**

[BazyleParticipant @bazyle]

Jack, would you be amenable to giving your talk at other clubs near London sometime next year?

If using Olive oil does the hardness increase if spinach is added?

[David Clark 13Participant @davidclark13]

I think it has to be hard to insert it in olive oil!

[jaCK HobsonParticipant @jackhobson50760]

Posted by Bazyle on 08/09/2015 08:47:46:

Jack, would you be amenable to giving your talk at other clubs near London sometime next year?

 

Let's see how it goes… everything I said about the bloke is true, and he is incredibly lazy – it really could be a disaster. He can't even type his forum name in correctly when registering an account.

Edited By jaCK Hobson on 08/09/2015 16:47:38

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