Cast SS Comparison

[49078]

I have been looking recently at different grades of ASTM A297. The product is used in application up to 1100 deg. C, and current grade HH is used. I just recently noticed that ASTM A743 CH20 has the same composition as the grade hh, except for the carbon content.

I was just wondering what the difference between these two materials are? I know the 743 undergoes heat treating, followed by a quench. I was told previously that the 297 are good for high temperature applications, but I don't understand why they would be any different then the 743. Could it be simply be a cost saving measure as 297 requires no heat treatment?

Any comments would be appreciated

 

[arunmrao]

ASTM A 297 is for cast articles for use in high temperature applications. ASTM A743 is for cast articles used for parts in corrosion applications. The carbon in ASTM A743 grades is kept lower to avoid formation of chromium carbides which is detrimental . Also these are heat treated to help dissolving the carbides and keep them in solution.

In the case of ASTM A 297 grades the carbon is kept intentionally high to encourage formation of carbides. The presence of these will improve the creep property and avoid grain growth at high temperatures.Normally heat treatment is not recommended for these alloys. But for castings that undergo extensive machining on CNC heat treatment is done.