Anyone Knowledgeable About Heat Treating?

[HEMI®Dart]

Maybe someone can figure out this problem.



The Company I work for makes Rotary Dies. Like the one below.



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The problem we are having is that some (1. 5%) of the tooling will warp during the heat treat process. When it warps, most of the time it goes into the scrap barrel.



I'm not sure who makes the heat treating machines, but they are electrical. The die goes in-between centers verticaly and a copper ring a little bigger than the body of the tool is placed around it. When the heat switch is pressed the ring turns the tool red hot then it automatically lowers it into the Quenchant. Then it raises back up after 5 minutes.



These are the things that were checked, and made no difference:



1. ) Die blank cut from the middle of the bar stock v. end of bar stock.



2. ) Use 6" bar stock to make a 3" die. In other words make sure the burnt layer or outside of the bar stock is totally gone.



3. ) Quenchant Ratio, Quenchent Temp, Amps v. Die size are all right on the money.



4. ) Operator makes no difference.



5. ) Humidity and plant air temp make no difference.

 

[RonaldLarson]

Check

to see how the die is being held while it's heated. Improper holding will sink heat away from the die and cause uneven heating, and warpage. Is this a new problem with the same old heat treater, or a new problem with a new heat treater?

This is a difficult part to restrain during heat treat, so you may have to semi-finish, heat treat, then grind and EDM to final shape and figure. Seems to me this part should be heated without being held, that is, in a basket in a relaxed state.

Ron

 

[fest3er]

Two other things to look at:

• quality/consistency of raw material
• temperature of tool after it's heated.

I would suspect that variances in the quality of the bar stock would allow warpage to happen. For a SWAG, have you tried something like drop-forged bar stock (if it isn't already)? IIRC, DF metal is more consistent throughout. Have you tried cutting open warped pieces to see if the metal is consistent throughout?

Also, have you checked the heating rate and duration, as well as the spacing of the tool from the heater? Minor variances likely won't make much difference, but large variances might.

If I had to hazard a guess, I would say you should look for a metallurgist in addition to a heat-treating expert.

Good luck!
Fest3er

 

[Extreme1]

Originally posted by fest3er

I would suspect that variances in the quality of the bar stock would allow warpage to happen. [/B]

I am pretty sure that a forged bar is going to be worse than a hot rolled bar because the material ends up being less homogeneous. A very consistantly cooled casting would make a good blank (depending on the material you are using).



We ended up getting the material (in powder form) placed into a steel case a little bigger than the finish shape and then it is heates and pressureized so when it melts and cools it produces a very dense, consistant blank. This isn't cheap but in our case it's worth the expense. It looks like it would be for you too. The process is called HIP casting. E-mail me if you would like a contact.

 

[HEMI®Dart]

Ron,



It's an old problem with fairly new Heat Treating machines.



Only 1-2% of Dies will warp. They heated 510 last month. 7 warped.



Thanks for the tips you guys.

 

[me4osu]

We use these guys a lot

They are very good at analysis of metallurgical problems and failures. If the other solutions don't work, try them.



Anderson & Assoc. Inc

919 Fm 1959 Rd,Houston,TX 77034

Phone: (281) 481-5840