Reply To: Advice on Heat Treating

[Ramon WilsonParticipant @ramonwilson3]

Well, as I said I spent quite a lot of time at work responsible for the heat treating and grinding of small parts from Uddeholm 'Arne' B01 as well as other tool steels from the same supplier.

That was twenty plus years ago but to my surprise the heat treatment sheet for Arne as provided by Uddeholm then was identical to the one I have just looked at now here – page 4

We followed this procedure to the letter heating in Wild Barfield ovens to very controlled temperatures before quenching to room temperature in (whale) oil and carried out the tempering in a separate oven designed for that express purpose. When we began this process at first the initial batch went into the tempering oven with residue oil on it which created a considerable amount of smoke. From that point, after the initial quenching, these parts – they were mainly punches and anvils for small press tools and would be done as batches of twenty hanging in a mild steel carrier, four carriers to a load so eighty parts in all – would be dropped into very hot water and a product called Citri Kleen. This was a potent degreaser, the oil being rapidly dispersed and the parts were allowed a short time to dry off then placed in the tempering oven. As previously said that would be done twice so the parts would see a Citri kleen bath three times before grinding.

Arne B01 is basically the same as guage plate and is ideal for home based heat treatment. What is difficult to obtain and be aware of when flame hardening is the actually temperature at which to quench. 'Cherry Red' is an oft quoted state but that can vary as much as the amount of different people attempting it. What I can say – with certainty – is that when these parts came out of the oven having been at the correct temperature 800-850 depending on harness required they came out a very dull red indeed. Over heating then to a bright red or leaning toward orange is too much and will, if overdone, lead to a crystaline and brittle metal structure.

As Dave S has just remarked, time at temperature does not affect the degree of temper but a variation of temperature most certainly does which brings me right back to the beginning – the best thing outside an oven in the home workshop is a tray of hot sand for about as best control as you can expect

Tug