Letter 26089

How do I harden cold rolled steel? [Alabama] 

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I HAVE MADE SOME PINS FOR A BACKHOE THAT I AM RESTORING .THEY ARE OUT OF COLD ROLL STEEL .HOW CAN I HARDEN THEM?

Janie Dean Moore
heating & cooling contractor & building contractor - Horton, Alabama

It depends on what type of steel it is. Cold rolled just refers to how it was worked at the mill, not what alloy it is. Some cold rolled steels are hardenable, others r not. If it is hardenable (high enough carbon content) heat it to about 1500 degrees (bright red color..heat til a magnet wont stick to it and then heat just a tad hotter) and dip it in either oil or water (water results in harder steel but more prone to cracking, oil may be the better choice).

If its a high carbon stainless they usually need to be heated to 2000 (very bright red/orange color)and cooled in fast moving air or oil these are just very rough guidelines since I don't have a clue what type of steel u have good luck.

Jason Aube
- Flint, MI, USA

Do you plan on putting this equipment back in service? Are these pins safety critical items? If so, think carefully about what you're doing.

Steve Bizub
- St Louis, MO

Please, have a heat treating shop handle this for you. After the hardening process described above, the part must be tempered properly to maximize the effect of the hardening. Depending on the alloy used to make the pin, any reputable shop can harden the part to your specifications, or application. If you only harden and do not temper the piece, you greatly increase the risk of stress fracture. The small amount a shop would charge is well worth the investment.

Michael Schneider
- Greer, South Carolina

Many heat treat shops wouldn't take this job unless you sign off on ANY potential liability. Some won't do it, period.

In my opinion, it would be better to buy OEM parts if you can still get them. Sometimes its good to be resourceful, but not in this instance, especially if its a safety critical part. Here's just a few of the problems I see with going "home made":

-You don't know the part specifications, so you don't know what type of heat treat is required. Heat treat is a broad term, just like plating. Does heat treat mean neutral harden and temper? Case harden and temper? Neutral harden, temper, selective induction harden and temper? Etc, etc? Unless you've got a part drawing or a list of specifications, you don't really know.
-If you picked the wrong alloy to make the pins, it won't harden, or it might be too hard after temper. Again, without a part drawing or list of specifications, you don't really know what steel to use.
-There could be post heat treat operations, such as shot peen, straightening, surface coating, or magnaflux testing required.

And is this part supposed to be machined from bar stock, or is it supposed to be cold formed or hot formed to minimize the potential for fatigue failure?

Steve Bizub
- St Louis, MO

My apologies, my view was too narrow. I saw the words "cold rolled steel, how to, harden" and didn't address the safety issue. Those gentlemen are right, have a professional do it, or better yet if possible get an oem part.

This thread is a month old but for future reference, the method I described will hopefully attain a full hardness(if its a hardenable steel)and may need to be tempered to a lower hardness to make it less prone to cracking, depending on the application. and as always, if its a critical part have a professional do it for you.

Jason Aube
- Flint, MI, USA

If it is a shaft or a pin you're looking for, you could go to a local machine shop and buy it. For farm equipment use I would suggest using a material called...C1045. It is a great material for wear and stress loads!

Robert Poirier
- Saint John, NB, Canada

If you need a pin of high surface hardness for wear resistance and a softer very tuff core try 8620 steel. Machine your pin then take it to a heat treater and have him carburized .030" deep and harden to R/C 60 surface hardness. The core should come up to R/C 35 or so. I have made many replacement parts for punch presses and other machines as well as pins and bushings for heavy equipment.

Wayne F Johnson
- Palmdale, CA, USA

If you want to do it properly you will need to get the parts case hardened. Passing it though a induction coil is how it normally is done. Takes a few seconds but you need the equipment. If you harden it straight though it will crack due to brittleness with any severe use.

Ronald Zeeman
Coil Coating - Brampton, ON, Canada

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