Nitrogen alloyed Hadfield steel

[berkrefik]

Hi, I am working on increasing the lifetime of abrasion resistant parts manufactured with Hadfield steel ( austenitic manganese steel ). I've read some articles about nitrogen gas purging into the melt while alloying with Ti or Nb which produces hard carbides and nitrides inside the austenitic grains thus increasing abrasion resistance. But i haven't heard of any foundry applying this technique, does anyone have information if any foundry uses this technique? And any other recommendations about improving abrasion resistance of manganese steels are appreciated

 

[EdStainless]

Adding N alone will increase hardness and the work hardening factors.

Have you worked with different pre-hardening methods? Some of the explosive surface hardening methods are impressive.

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Plymouth Tube

 

[arunmrao]

Addition of Ti and Nb is a good practice to produce fine grains, yet the results are not consistent in shop practice. I have reviewed a few technical papers on this topic, but the technical details were disappointing.

Some had suggested a bizarre addition of 2%Mg !!

 

[NickE]

arunmrao- maybe they figured if it was good enough for ductile iron, it's good enough for hadfields.


Nick

 

[berkrefik]

Thanks for the valuable answers,
EdStainless- I haven't worked with pre hardening methods like explosive hardening. But i've had some lab trials like heating the austenitized steel to 650C, hold for 8 hours, furnace cool and get some pearlite within the grains and some in the boundaries. Then heat it up to 800C, hold for 3 hours, furnace cool and get those pearlites little bit spherodized. I've some doubts about its toughness compared to austenitized steel so I didn't apply it to my customers parts.

arunmrao- I've read the following article, its like they had good results in laboratory. But its a mystery in shop practice.

http://files.engineering.com/getfil...gh_Manganese_Steel_Alloying_With_Nitrogen.pdf

 

[arunmrao]

Thanks for the reference, foundries claim that 24% Mn steel gives better life. I have worked to 20% , and the results did not justify,increase in Mn content.

What parts are you studying for improved wear life?

 

[EdStainless]

Using sensitization to increase hardness is probably not a good practice as the toughness will be very low (and the corrosion resistance will be terrible).

I have looked (unsuccessfully) for an old reference that was talking about 20% Mn grades.
They had added Ni (maybe 2-4%) and N (a lot, like 0.5%) and Mo(I think, or maybe Cr).
I don't recall C levels. You would need to look at the phase balance and estimate how much of the C will be in carbides.
Given that the Mn, Ni, N, and C are all austenite stabilizers I am not sure where you end up.

I do recall that pre-hardening (explosive or hammer forge) significantly reduced overall wear of parts.

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Plymouth Tube

 

[arunmrao]

Spheroidization of carbides improves toughness in low alloy steel, but the reverse happens in Mn steel. It is not proper to have carbides precipitated, within or on the grain boundaries.

Ed, 20% Mn grade has a nominal C content of 0.8-1.0, though Ni may be present, Cr is 1.5-2.5 and Mo about 0.5.

Each manufacturer claims that his recipe is the best and the debate remains inconclusive.

 

[Guest102023]

Nitrogen is an austenite stabilizer but will happily combine with players like Ti and Nb. There is a practical limit to the percentage that can be added to the melt, I'm guessing 0.25%, so it could not have a very great effect.

Abrasion resistance is improved by the use of second-phase carbides of V, Nb, etc., but always at the expense of Hadfield's classic properties.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[Guest102023]

p.s., Anyone know the ASTM standard for the plate form of this alloy?

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[EdStainless]

With 20% Mn you could easily keep 0.50% N in solution with no nitrides.
Look at the Nitronic stainless grades with about half this Mn and they have 0.40% N.

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Plymouth Tube

 

[mrfailure]

Brimstoner,

I am only aware of ASTM standards for Hadfield steel for castings - ASTM A128.

 

[berkrefik]

arunmrao- i'm studying for cone crushers. We use 18%Mn, 1,2%C steel for that parts but our customer claims that they get %20 to %40 longer lifetime with different suppliers. I thought they've done some special treatment like pre-hardening or N, Ti, Nb alloying but I analyzed those castings and they had 12%Mn, 1,1%C, 0,50%Mo.

 

[arunmrao]

berkreflik,

I face no issues with cones and mantle castings, but some variance in jaw plate castings. A 18% Mn steel has yielded no improvement in a few cases.

What is the grain refiner that you are using?

 

[berkrefik]

I am not using a grain refiner,
my melting practice is using 50% scrap, deoxidize with 0,1% Al then Argon purging for 1 to 2 minutes.

 

[arunmrao]

I suggest you use Ti + Va and possibly maintain Nitrogen at 0.04-0.05% . Also, important is the pouring temperature, do not pour high.Hope it helps.

 

[berkrefik]

Thanks arunmrao, i will try Ti+Va.