Induction hardening distortion
Induction hardening distortion
(OP)
Hello,
We have had some trouble with one of our spindle shafts.
1. I was hoping to learn how to estimate how much distortion/ dimensional growth I should expect after induction hardening a shaft (drawing attached). Material is 4140. Could someone provide a number, or means to calculate?
2. I would like to improve our drawing callout for heat treat. All we say now is induction harden, min. 45 HRc, and the location to be hardened. Could someone provide pointers, or reference material for specifying?
Thanks,
Mark
We have had some trouble with one of our spindle shafts.
1. I was hoping to learn how to estimate how much distortion/ dimensional growth I should expect after induction hardening a shaft (drawing attached). Material is 4140. Could someone provide a number, or means to calculate?
2. I would like to improve our drawing callout for heat treat. All we say now is induction harden, min. 45 HRc, and the location to be hardened. Could someone provide pointers, or reference material for specifying?
Thanks,
Mark





RE: Induction hardening distortion
Distortion will be tough to create a specific formula, since there are many factors that contribute... processing history, heat-up rate, quench rate...
As far as you call-out - you need to add a minimum temper say 300- 350F just to make sure you don't have a surface of virgin martensite. Most heat treaters will do this automatically.... but it is better to be safe-than-sorry. Other consideration...if you are concerned with distortion you may want to mandate an oil quench (or even warm oil).
RE: Induction hardening distortion
I don't like the practice of specifying the tempering temperature in this case. The problem with specifiying a tempering temperature is if there is a problem, at least part of the blame could be put on the tempering temperature that was specified. If you tell the baker how to make the cake, you can't complain about how it tastes.
Rather than specify a minimum temper, I would suggest you change the callout from just "induction harden" to "induction harden and temper", and then give a hardness range instead of just a minimum. That is, your note could say, Induction harden and temper to 45-50 HRC. Personally, I think 50 HRC is a bit high for 4140, but if you have too narrow of a hardness range, the heat treater will not be able to hit it. If you could accpet 42 HRC as a minimum, I'd be more comfortable with 42-47 HRC than 45-50. If you just have to maintain the 45 HRC minimum, I'd suggest a talk with your heat treater to see how narrow of a range he would be comfortable with.
rp
RE: Induction hardening distortion
RE: Induction hardening distortion
I'd agree with israelkk's comments. If all you need in that flange area is Rc45, rough machining and then a full oil quench and 800degF temper, followed by finish machine operations on the part would be more cost effective.
An induction heating and quenching of the flange area would leave you with a very hard and brittle material condition (>Rc55) unless it was subsequently tempered. Quenching the flange area with those small holes and sharp edges may also result in cracking.
Good luck.
riff_raff