Hardening of en8

[BrokenBiker]

Looking for the proper procedure for hardening and tempering en8.

Few parts to make that would do well to be hardened. Don't need to be glass hard, just enough to resist wearing against mild steel

I can regulate the forge temp pretty well and have a thermocouple that is good to 1300C

 

[dave h 2]

I think it might gall, though I may also be wrong. If there's room for a cast iron sleeve as a bearing surface.............

 

[BrokenBiker]

I think it might gall, though I may also be wrong. If there's room for a cast iron sleeve as a bearing surface.............

Should probably have mentioned, most of the parts will be bead roller dies

 

[Kram]

Heat to 800-850c and quench in brine, then temper at roughtly 220-250c. They say to hold the heating and tempering temperature for 1h per inch thickness

 

[BrokenBiker]

Cheers, 2 hours should do it then for both.

What is needed for the brine?

 

[RichardM]

Salt and water!

 

[BrokenBiker]

Salt and water!

Well I assumed that at first, but I've assumed in the past and got it wildly wrong

 

[Kram]

For plain carbon steels like EN8 they need to be cooled fast or they wont harden, so water or brine is needed. I've used plain water in the past.

For alloy steels - O1, silver steel, water is too much of a shock and can crack them, so they can be quenched in oil. Most of my hardened parts have been O1.

 

[BrokenBiker]

For plain carbon steels like EN8 they need to be cooled fast or they wont harden, so water or brine is needed. I've used plain water in the past.

For alloy steels - O1, silver steel, water is too much of a shock and can crack them, so they can be quenched in oil. Most of my hardened parts have been O1.

I use a reasonable amount of en8, never need anything cutting tool hard.

I may make some of the smaller stuff first and test them in the forge to see how they come out.

I can get salt 5kg at a time so will make brine up and keep it in milk bottles til needed

 

[Kram]

It only needs to be 10% brine, it prevents steam bubbles from insulating the part, so it cools quicker, giving a better hardness.

 

[oldbikedavey]

Note that EN.8 through-hardens, given the chance.
You could use case hardened EN1 , which might be a bit more friendly in some respects.

 

[BrokenBiker]

Note that EN.8 through-hardens, given the chance.
You could use case hardened EN1 , which might be a bit more friendly in some respects.

Through hardened isn't an issue. Plus I have a big chunk of 60mm dia en8 here that is the biggest diameter I will need for a while.

My only main concern is the M8 tapped cross hole for the grub screw that locks the die to the shaft, although as it's not a drive roller and both shafts are geared in not entirely sure it needs the grub screw

 

[Kram]

I'd think through hard is wanted to stop deformation. Case hard will only add some abrasion resistance.

Threads shouldnt be a problem if its tempered after.

 

[oldbikedavey]

I'd think through hard is wanted to stop deformation. Case hard will only add some abrasion resistance.

Threads shouldnt be a problem if its tempered after.

All a bit of a nest of vipers, but depends upon the intensity of use, I suppose.
My CMZ 5 has full-length keyed rollers, but only very,very occasional use, so a mild steel unhardened roller does well enough.

 

[BrokenBiker]

Tipping die and crisp bends are one of the main reasons I wanted one so the harder bottom die will see a decent amount for use compared to the others.

 

[oldbikedavey]

Tipping die and crisp bends are one of the main reasons I wanted one so the harder bottom die will see a decent amount for use compared to the others.

Salt hardening may be your friend there , but pack hardening may be easier to wangle.
The Case Hardening of Steels, by Harry Brearley is very informative and well-written.
Mostly, it's about diffusing enough carbon and/or nitrogen into the lattice structure, and 900C is about right for that.
I have a small heat treatment furnace, but might consider making a bigger one.....

 

[minimutly]

Salt hardening may be your friend there , but pack hardening may be easier to wangle.
The Case Hardening of Steels, by Harry Brearley is very informative and well-written.
Mostly, it's about diffusing enough carbon and/or nitrogen into the lattice structure, and 900C is about right for that.
I have a small heat treatment furnace, but might consider making a bigger one.....

From my limited knowledge, doesn't nitrogen hardening make the part grow? Plasma nitriding I think was the term if I recall?

 

[BrokenBiker]

Salt hardening may be your friend there , but pack hardening may be easier to wangle.
The Case Hardening of Steels, by Harry Brearley is very informative and well-written.
Mostly, it's about diffusing enough carbon and/or nitrogen into the lattice structure, and 900C is about right for that.
I have a small heat treatment furnace, but might consider making a bigger one.....

Sounds more complicated than letting it soak at 850 for 2 hours and dunking in brine...I'm a huge fan of simplicity and given I want wear resistance and as little deformation in use as possible through hardening seems to be the answer.

From what I can gather the commercially available bottom dies are through hardened and the upper end of the market are ground to look pretty, I won't be grinding but I will clean up with a wire wheel and if needs be touch it up with a ceramic tool in the lathe but as long as it's close enough to round it doesn't bind in use I'm calling it good

 

[whm_fab]

as a quick segwey as im interested very much in doing a bit of this this also, can you post a few details regarding your furnice / forge?
there seems to be tons of different designs / ways to get steel up to that temp and hold it relatively stable, cheers!

 

[Dr.Al]

For plain carbon steels like EN8 they need to be cooled fast or they wont harden, so water or brine is needed. I've used plain water in the past.

For alloy steels - O1, silver steel, water is too much of a shock and can crack them, so they can be quenched in oil. Most of my hardened parts have been O1.

Agree with most of that, except the inclusion of silver steel in the oil list. It is usually quenched in water (that's certainly what I do). It's what (I think) the Americans call Drill Rod or W1 tool steel (the "W" being water quenched).

Example data sheet: https://www.silver-steel.co.uk/wp-content/uploads/2024/10/BS1407-Technical-Specifications.pdf / https://www.coventry-grinders.co.uk/app/uploads/2014/03/Silver-Steel-Data-Sheet.pdf

Extract:

Another one: https://www.sanderson.co.za/download/silver-steel-data-sheet.pdf

Extract: