9310 Bolt Data

[lysander]

The biggest issues I’ve seen with 9310 is the result of improper heat treat, and 9310 is much less forgiving with the treatment temperature range. 9310 is harder than C158 but it’s also more brittle, it’s fatigue life is also notably shorter than C158.

I have a number of reports that stated that 9310 is actually a very forgiving steel to heat treat compared to say 8620 which no one has every accused of being a difficult steel to treat. If fact, 9310 response to thin section quenching is better that Carpenter 158.

And, taking the leap between this statement:

". . . by comparison to Carpenter 158, AISI 9310 has several elements present in its composition that are detrimental to fatigue while not being evident in the physical properties . . ."

and this statement:

". . . 9310 is harder than C158 but it’s also more brittle, it’s fatigue life is also notably shorter than C158 . . . "

Is an unsupportable leap.

First, I am going to take issue with "several elements present in its composition that are detrimental to fatigue", the only element in 9310 that is not in 158 is molybdenum which is not "detrimental to fatigue", the other two elements , as stated earlier are impurities that will be present to some degree in all alloys.

Second, 9310 is not "harder". It is hardened to achieve the proper strength, and that happens to be the same hardness as Carpenter 158, around 36-40 HRc.

And last, I have not seen any study of 9310 that states it has a short fatigue life. In fact one of the reasons it is popular as a gear material is because it can withstand high cyclic loading over a long period of time.

So, stop requoting the myth that 9310 is "harder to heat treat", "is harder and more brittle", and unless you can cite a study that shows 9310 has a poor fatigue behavior, stop that too.