Flatness Tolerance after Heat Treatment 1

[som1973]

Hi All,
We are in process of producing a heat treated flat bar made from Cast Iron(FG260).

This cast iron bar is used for supporting the conveyor belt in an Industrial oven.

The cast iron bar is machined as per the drawing & heat treated by Induction hardening to 1.5 mm case depth.

The length of the cast iron bar is 1200mm, width of the bar is around 70mm.

After the heat treatment, the flatness measured is up to 3mm along the length of the cast iron bar.

Can anyone advice Flatness tolerance after heat treatment(Induction hardening)?

We are unable to decide whether to accept or reject the part.

Thank you

 

[Tmoose]

What was you original flatness tolerance?
How many parts are affected?
Is just one side of the bar hardened? Is the intent of hardening better wear resistance?
What is the "depth" dimension of the bar?

I'm guessing the bar curved with the induction hardened portion on the convex side.

RE:Flatness tolerance after heat treatment.
The residual compressive stress from induction hardening ( and I guess many hardening processes, and even shot peening) is pretty darned high, so if the process was on just one face of the bar, and the bar is not mighty "thick", I am not surprised at all the bar curled downward a bit.

http://shodhganga.inflibnet.ac.in/bitstream/10603/1259/15/15_chapter 6.pdf

Was the required final flatness on the paperwork sent to the heat treater?
If it was, I'd be surprised they did not warn you some distortion was to be expected.
It the RFQ was just "induction harden this face of these parts to XXX" then I guess the heat treater could not have known X flatness was needed.

**??>> IF <<??** I envision the gray cast iron parts correctly as simple rectangular bar, I would not attempt to straighten them , for fear of them snapping.
I expect they could be successfully straightened by mechanically peening the the concave side.

 

[MintJulep]

. We are unable to decide whether to accept or reject the part.

If you, presumably the designer, don't know how do you expect us to know?