High Mn Steels 1

[ibfmining1]

Hello !

Two Questions:

1. Many customers are now ordering min. 20% Mn for Hadfield steels, as opposed to the traditional 11%/14% as per ASTM A128. Is there any literature and/or study which explains and actually confirms a better performance for the 18/20% Mn steel?

2. For Mn Hadfield steels I always prefer Molly addition as opposed to Cr because Mo suppresses the formation of pearlite during quenching and also minimizes the likelihood of coarse carbide precipitation at GB in case of a slack quench. For a 1.5% C, and 18% Mn alloy, where 2% Cr is required by the customer, would you (if you had the option) add molly in lieu of Cr, or could 0.5% - 1% Molly + 2% Cr suffice the risks of premature cracking ?

Hope I have made myself understood (?)
Thx.

 

[gtaw]

A lot would depend on the application and what is expected of the steel.

Best regards - Al

 

[arunmrao]

@ibfmining1,

I begin with a caveat, my experience is limited to high impact wear resistant castings weighing 100-5000kgs.

I regularly produce 18% Mn grade castings, the reports are mixed, ranging from very good to nothing better than 14% Mn grade. However, all OE parts contain 18% Mn and thus the trend.

Addition of Mo is welcome, if your cost permits .Reduce the Carbon to 1.2% max(preferably 0.9-1.0%) for 18% grade, perhaps you may not need any Mo. I produce this grade with no Mo and Cr upto 2.5%, the microstructure, I get each time is free of any carbides.

Do you add any grain refiners?

Hope it helps.


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[metengr]

Sound advice from our resident high-Mn castings expert!

 

[EdStainless]

I haven't poured any of these for 20 years, what grain refiners are preferred?
I remember trying to get uniform fine grain material.

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P.E. Metallurgy, Plymouth Tube

 

[ibfmining1]

Thank you all for the comments.

1. The application is for crushers (mantles and concaves)- weight range 1 to 3 metric tons.

2. The biggest challenge is to deal with different suppliers (each one of them has a different way to "skin the cat").

3. We will try now 1.15% C max when 2% Cr is added (maybe 1% would fit better as mentioned by arunmrao). However, pouring temperature is also an important essential variable. If too high, the grains will remain coarse, regardless how good and accurate your quenching process is.

4. We also noticed that Si as high as 1.0 % is also critical for embrittlement.

5. Impact values also go from "heaven to hell" when test coupon thicknesses vary from 1 inch to 3 inches (all other variables kept constant).

Anyhow, thanks again to all your answers. Appreciate that.