Distortion During Induction Hardening
Distortion During Induction Hardening
(OP)
We are attempting to induction harden shafts in a vertical scanning operation, and we are getting so much distortion that the shafts cannot be straightened, (without breaking) after hardening. The shafts are 1.875” diameter, 1547 continues cast material, (Mac Steel, formerly North Star, Monroe) 2.5 DI, 43” long. The spec is Rc 40 at .400”. We are heating with a 1khz, 250 kw power supply, and quenching with 12% Ucon Quenchant A at 95 degrees Fahrenheit. We are running the case depth at the minimum. Does anyone have any suggestions how to reduce the distortion and still meet the case depth requirements.





RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
Is it quenched and tempered? If so, what process is used for the heat treatment.
Assuming taht the IH process is being done uniformly it would appear that there is a lot of residual stress in the parts.
RE: Distortion During Induction Hardening
Unfortunately, the spec is Rc40 @ .400.
Carburize
The material is hot rolled material with no pretreatment. I agree that there seems to be a lot of residual stress in the parts. I suspect that that it has something to do with the way the material is cast, in that it has a bend as they cast the billet, 6”X6” I think. I would think that these stresses would be relieved when the material is reheated for rolling, so I guess that I am lost at this point. We are going to normalize a test batch of the material to see if that helps, but it will be a few days before we know.
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
According to "Induction Heat Treatment of Steel", by Semiatin and Stutz, ASM publication, part distortion during induction heat treatment can be caused by too high of an austenitizing temperature, improper induction scan rates, uneven heating, nonuniformity of quenching, and relief of residual stresses.
The book mentioned possible rotation of the part to enhance uniform heating. Regarding quenching, sizing of the quench ring holes (orifices) and angle of spray were listed as important variables. A 30 degree angle between the axis of the spray holes and the axis of the part was suggested for single-shot spray quench devices used for induction scanning setups.
This book contains very practical information. You might want to consider purchasing it for future reference.
RE: Distortion During Induction Hardening
from my own experience in the field of hardening, quenching is the proces which can cause the distortion.
As a tool and die maker, i dont surface-harden my parts, so i'm not really familliar whith that proces, but for any hardening proces a couple of things are to be kept in mind:
Heating uniformly, and not to fast, giving the material time to form austenite
Quenching should be done in such a way that the workpiece also cools uniformly.
we quench our parts ( 1.2379 / D2 ) in a salt bath at 230 degrees celsius /446 Fahrenheit after heating to 1030 degrees celcius / 1886 Fahrenheit for hardening
the parts are put in quickly, and for instance long and thin parts ( like shafts ) are put in vertically to minimize distortion.
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
We are rotating the shaft during hardening. We have tried different rotation speeds, the slower speeds distort less, but the shafts still have excessive distortion.
RE: Distortion During Induction Hardening
And what the physical configuration of the heating looks like?
Does the shaft go immediately into a max heating region? Is there or should there be a transition?
TTFN
RE: Distortion During Induction Hardening
How did you optimize your induction scan rate? In the ASM book that I mentioned above, they do list recommended induction scan rates based on material and diameter.
RE: Distortion During Induction Hardening
Have you considered hot straightening just below the tempereing temperature immediately after quench?
Jesus is THE life,
Leonard
RE: Distortion During Induction Hardening
HEAT TREATING PROGRESS - MARCH 2003 - AN ASM PUBLICATION.
The article was written by Mr. Fred Specht and refers to distortion control by using a two-turn inductor and retracting idler rolls to minimize distortion (horizontal scanner though).
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening
RE: Distortion During Induction Hardening