Case Hardening

In days of yore I seem to remember that RS did two kinds of iron bar, EN1A which was not case hardenable and the one with the green paint on the end that was. Taxing my brain here, didn't the EN1A contain lead to make it free cutting and that precluded case hardening?

68 years may have weakened my brain but it comes with nearly a full tin of Kasenit No. 1 so it's not all bad

Some, but not all EN1a had lead, tellurium or antimony in it to improve the machineability. These tended to make it no good for case hardening or welding. It also tends to rust if you look at it cross eyed. It's lovely stuff to machine, but pretty useless for anything else (No, I'm not bitter and twisted, far worse than that )

What's the cheapest medium carbon steel which could be heat treated rather than case hardened, to make it less complicated.

En8, 0.40% carbon steel is my suggestion. It can be hardened by oil or water quenching from red heat, and then tempered, rather like silver steel.

Thanks Clive, do you know if it machines well on a mill? is that the equivalent to key steel?

The modest amout of machining that I've done with En8 has shown it to be good in that respect. Google suggests that key steel is similar material. Also brings up a free-machining version, En8M, but maybe that isn't so good for hardening.

I emailed a local supplier and enquired about EN8 keysteel, and they quoted back for Bright mild steel. Is BMS a generic term for various grades of steel?

BMS should mean Bright Mild Steel, not a carbon steel.

Hi all. Can Kasenit be reused? i.e. once its turned into an ash looking state can it be crumbled down again and reused or has the carbon been transformed into something else?

If it has been open to air (oxygen), while at red heat, it will be like charcoal - after being used on the barbeque.

Edited By not done it yet on 30/01/2020 10:56:42

Some suppliers see it that way. Steel from some vendors goes entirely to structural trades rather than machinists. Although these chaps sell 'steel', they may not stock anything out of the ordinary or recognise any type of steel outside their usual remit. (There are over 2000 different steels available, many of them specialised...)

If a local stockist can't supply what you want try a bigger outfit, or the Internet, or one of the Model Engineering suppliers.

'BMS' is a low carbon steel, heated and rolled to be reasonably flat and fairly accurately dimensioned with clean edges. It's a structural steel, where being finished saves time and effort when building frameworks etc. Black steel is pretty much the same stuff, but it's left covered in black scale, has poorly defined edges, and only approximate dimensions. Being cheaper, it's used in place of Bright when appearance doesn't matter. Rolling makes Bright slightly stronger and tougher than Black, but Bright is more likely to be internally stressed such that it bends when cut. Mild steels, like BMS and Black, are very common because they're cheap, moderately strong, and easily sawn, drilled and welded. Soft and bendy, no good for knives or springs, can't be heat hardened, and not as tough as a high-carbon steel like EN8. It machines reasonably well, but EN1A is distinctly friendlier, and leaded better again. If a specification calls for EN8, mild-steel isn't a good alternative.

Dave

Edited By SillyOldDuffer on 30/01/2020 12:17:15