Looking for example heat treat cycles for: 1

[NickE]

A2, D2, O2, M2, W2 tool steels.

What I know already: obviously tools are formed from bar stock in the "dead soft" annealed condition. Geometry is machined into the steel, weather using grinders, CNC, EDM, etc...

Now the hard part: Take the tool above the respective austinatization temp, hold till completly x-formed, but not too long to cause extensive grain growth. Quench in Air, Oil, Water, etc. However the quench has to be controlled properly to prevent dimensional change.

My questions:

1) Is the goal in the quench to form martinsite?

2) If so with the alloying present in these steels won't I have to cryo-quench to pass below the Mf temp?

3) Now do I have to temper the steel to prevent brittleness?

4) Should the steel be austinitized in an inert atmosphere to prevent de-carburization?

5) What are the quantitative answers to the fundamental questions? ([t]ime, [T]emp)

(I think <I mean who really completely does anyway>)
I understand the kinetics and thermo of why and how, but I have no practical knowledge or information on quantitative industrial practice.

Our die tooling shop would like to do some of their own heat treating and since I'm the local metallurgist I said that I would do a bit of research and see what I could find. Yeah In school they taught me this, but industry and most certainly the &quot;old heat-treater&quot; has some tricks that use the thermodynamics/kinetics to a more effictive result.

It may be that there is no savings in doing small heat treat jobs ourselves.

Thanks
Nick

 

[metrat]

You pose a lot of good questions, perhaps I can shed some light on at least some of them. You reference a number of different tool steels, which will react somewhat differently.

A2 for example is an air hardening tool steel, therefore the &quot;quench&quot; step is essentially to cool it in air rather than a conventional oil quench. This makes the transformation less &quot;stressful&quot; and aids in minimizing distortion, cracks, etc. D2 is similar.

M2 will require a more sever quench, oil or salt down to about 1000F or so, then air cool to room tempo.

Siffice it to say, there are general tool steel categories, all will react somewhat differently.

1. Generally the goal is to transform to martensite, to gain the max. hardness.

2. If stability is a prome concern, then a sub zero step would be improtant. If you are working with cutting tools and the like, it may not be critical. My experience is that for most conventional tool applications the cryo. step is not necessary.

3. Temper will be improtant. It will improve toughness over the as-quenched condition, thus makeing the tools more use-friendly. Be aware you will alos lose some hardness as a resilt of the temper. It will be a balancing act, hardness(good wear resistance) vs. toughness (less fracture and chipping). Select temper temperature to achieve the balance you need.

4. Generally tool steel will need to be protected (inert atmosphere, vacuum, etc.) due to relatively high hardening temps. Some perople place tools inside a stainless bag to provide some protection in an air furnace.

5. Time will be generall be determine by material and section thickness (long enough to make sure the entire section is at temp., not too long to cause grain growth, decarb, etc.)

Temperatures will be governed by alloy type.

Hope this helps some.

Mike

 

[CoryPad]

If you need actual time and temperature information for heat treating tool steels, you should purchase some books. Some recommendations are:

ASM Handbook Volume 1 Properties and Selection: Irons, Steels, and High-Performance Alloys

ASM Handbook Volume 4 Heat Treating

Heat Treater's Guide: Practices and Procedures for Irons and Steels, 2nd Edition

These are available from ASM International at:

http://www.asminternational.org

 

[NickE]

Metrat-
Thanks, thats a good expansion of my qualitative knowledge.

CoryPad-
Ahh.. references, I'll reccomend that we purchase some if I get the go-ahead. I'm unsure of the feasability yet. I may get just the heat-treaters guide for myself.

nick
(more responses always welcome)

 

[TVP]

There are several tool steel producers that provide a large amount of technical information on their websites. Crucible, Timken Latrobe, and Carpenter have the most extensive information, including details about heat treating. The following links should be useful for you:

http://www.crucibleservice.com/products.cfm

(click on Mold Steels, High Speed Steels, etc.)

http://www.timken.com/products/specialtysteel/engineering/tech_info/highspeedfax.asp

http://www.timken.com/products/specialtysteel/engineering/tech_info/coldworktoolsteel.asp

http://www.timken.com/products/specialtysteel/engineering/tech_info/techtips.asp

http://www.cartech.com

(You must register to view the Technical Information section, but it is free. Then click on Tooling Selector, then Matched Tool & Die Steels. Alternatively, you can select Alloy Category from the Technical Information menu, and then Tool & Die Steels.)

 

[rd400guy]

Nick,
Depending on the size of the dies your company uses, the required kilns/furnaces and quench tanks could be a relatively inexpensive purchase when compared to outside heat treating costs, over the long term. In addition, by learning about the various heat treating processes (and adjusting them with some experimentation) you may be able to attain better physical properties, specific to your application, than your heat treater currently provides you with.
Although heat treaters do try to meet their customer's needs, they generally have a lot of customers, and probably do larger batch heat treatments, so a bunch of parts get the same cycle, and depending on your particular die's location in the batch, variation will occur. By heat treating very small batches in your own furnaces, you may be able to see more consistent properties, and therefore longer die life.
Just a few points to consider when trying to sell your bosses on the idea. I hope it helps. One other thing, though, considering the possible conflict looming on the horizon, energy costs have already started to rise, and depending on how things go, they may jump up to or past where they were a few years ago, so the bean counters may not like the idea of investing in something that will further increase energy costs.

Ben

 

[carlosf]

I suggest The apraiz book, i know that is in spanish, but in english, i dont know. There is all your question response, Time vs. temperature for tools steel, and the best condition for make the heat treatment in diferents steels.

P.D> Sorry for my english, i'm still learning.

 

[EngineerDave]

Carlosf,

What is the exact title of the book by Apraiz? I read enough Spanish that I may be able to utilize it. It'd be interesting.

Thanks for the info in advance

 

[TVP]

I believe this is the book to which carlosf was referring:

APRAIZ BARREIRO, José. Aceros Especiales y Otras Aplicaciones. Editorial Dossat, 4 Ed. Madrid, 1971.

 

[EngineerDave]

Gracias
I'll look for it, but it might be tough to find around here.