8620 to 11 - 14 Hatfield comparison

[RLJ]

I am reviewing the manufacturing process of a cone shaped piece currently made of 8620 material. The material is cut flat and rolled into the cone shape, cold working the 8620. @28" large diameter, 16" small diameter. Then a mild steel mounting ring and base are welded to it. The piece is then fully annealed and the 8620 is carburized and drawn back to approximately 40 Rc. The end result being a piece with high strength and good abrasion resistance.

A suggestion has been made to change the material to 11% - 14% Hatfield Manganese steel. I have spoken with local steel suppliers and heat treaters but would like input from this forum as well. What advantages/disadvantages would there be to making this change?

Thanks in advance... RLJ s-)

 

[mcguire]

At the same hardness Hadfield would have poorer wear resistance because it derives its hardness primarily from cold work as well as partly from transformation, gamma to alpha prime. It gets its wear resistance from isolated carbides which is not as good as the uniformly high hardness carburized surface.

 

[RLJ]

mcquire,

Thanks for the response. Do you know of a good web source for chemical composition and performance data on these two materials? RLJ s-)

 

[arunmrao]

One point to be considered is the useful life of the part. In the case of 8620 carburized steel after the case has worn out there would be very little wear resistance left in the material and the component will have to be prematurely discarded. However, you can continue to use the Hadfield steel component for a longer time as the next layer replaces the worn out layer. I hope I have expressed clearly.Hence replacement can be deferred.
Also the ease of manufacturing a component with Hadfield steel will have to be compared with 8620 steel

 

[RLJ]

arunmrao,

We currently case harden the 8620 to a depth of 0.120" with a total material thickness of 0.500". If the manufacturing benefits favor the 8620 we could always increase the depth of case hardening.

Which material is easier to cold work? RLJ s-)

 

[arunmrao]

8620 steel is certainly easy to coldwork or machine.

 

[mcguire]

The Metals Handbook from ASM, desk edition, has information on these materials.