Shaft Mat'l - ANSI 4140 vs 4150 ? 1

[sprintcar]

I'll post this in a couple forums.
We're looking at pump shafts, under 6" bar size. Other than the 10 points difference in Carbon content (per ASTM A29), I can't find an appreciable difference between 4140 and 4150 until you get around 8" bar size where tensile differs a little.

Assuming non-resulfurized, is there any reason - such as machining - that makes one better?
Thanks! Keep the wheels on the ground
Bob
showshine@aol.com

 

[Carburize]

The higher carbon content of the 4150 gives the potential for higher hardness but this comes with the penalty of a material which is more prone to quench cracking. If you can get the hardness/strength that you need from the 4140 then in my opinion there is no benefit in using the 4150.
I use a lot of 4145 which develops good properties up to 10-inch diameter and, when oil quenched, few problems of quench cracking.

 

[GearmanPE]

sprintcar (Mechanical)

Response from carburize is right on. Be very careful if the part is heat treated after machining and has any groves , small radii or rapid section change. A 6 in shaft is quite large, if highest performance is needed, consider 4340 which is deep hardening.

 

[sprintcar]

Generally the parts are not post-machined heat treated, since some are made offshore. We estimated about 4% lower strength for the 4140 in the larger sizes.
Gearman is right, but the cost increase for 4340 creates a problem.
Thanks guys! Keep the wheels on the ground
Bob
showshine@aol.com