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Recommended Techniques: 13% Mn Steel

04/04/2020 3:29 PM

I'm seeking some general advice for specifying finishes & tolerances for parts I wish to have made from the demon-spawn alloy known as Hadfield steel.

In case someone forgot, t's an Austenitic, work hardening, impact & abrasion resistant steel. Usually cast to near net shape, including the holes, because drilling the stuff is a nightmare. When a part calls for threaded holes, cores of an 'easily' machinable material (like 'Inconel' or 'Stellite') are inserted into the mould. You know the stuff with a machinability score of "0". The stuff they make rock crusher cones & jaws out of, and the teeth for earth-moving buckets and hard-rock scrapers.

I'm trying to get an idea of what is 'practical' to machine vs what is just copied down because that's what the bearing spec sheet says is expected.

There is a lot of anecdotal lore concerning this material. I cannot tell which of those stories are 'true, but obsolete', 'false, to scare competition', 'still applicable, when using 80 year-old techniques & setups', and 'contemporary fact still not to be ignored without consequences'.

Thanks in advance,

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#1

Re: Recommended techniques: 13% Mn steel

04/04/2020 4:16 PM

Here is a link that states the Hadfield Steel is heated to 500C and water quenched before machining to make it easier to work.

As with all work harden able materials it is advisable to keep the machining tools in motion before contact with the metal and use low pressure in order to try to "outrun" the work hardening characteristics.

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#2

Re: Recommended techniques: 13% Mn steel

04/04/2020 6:15 PM

I would think this is item specific, in other words each application may call for a customized approach...there are many ceramic coating or metal coating technologies that might apply, diamond grinding tools, water jet with silicon carbide, laser powered cutting and surface glazing machines, electrical discharge machining....etc

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#3

Re: Recommended Techniques: 13% Mn Steel

04/07/2020 11:35 AM

Because of the material in question, High Manganese..

Your tolerance should be compatible to the fabricator's capability.

Your Ra should be adjusted by the fabrication (i.e. center grind-vs-shot as well) dependent on material dimensions

Don't stress tight tolerance beyond the need.

Remember: the tighter the tol, the more open your wallet.

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