Thread: 4140 confusion

I bought A Short length of 4140 which I think is what they call " pre-hard" the seller says it's hardness is RK 32 or therabouts, the surface finish is very smooth and shiny .

There are various terms used to describe the state of 4140 - annealed or tempered and cold rolled and hardened

So if the the shiny smooth finish is achieved by cold rolling . Do they roll it after it has been tempered and quenched or before the tempering has been done ?

The cold rolling process does surface harden it to some degree I think .

You may have material that is hardened then "peeled and polished" and sold under that description. I have bought it from Bohler, don't know what their finishing process is.

Probably peeled and polished as stated. I have some here in 65mm for a special project. Bought from Bohler as well.

Originally Posted by SurfinNev

Probably peeled and polished as stated. I have some here in 65mm for a special project. Bought from Bohler as well.

OK. I found this info useful as a general guide http://www.atlassteels.com.au/docume...Oct%202011.pdf

Pretty much all 4140 barstock sold here in Aus is pre hardened. i have only encountered annealed 4140 in a forging i had to proof machine, and it was gummy and horrible to machine. The smooth finish is from the burnishing effect when they cold roll the bar.