AISI 416 hardenability 1

[israelkk]

What will be the maximum section thickness to harden and temper 416 to 34-48 RC.

What is the maximum bar diameter for AISI 416H per ASTM-A-582 (pre hardened bars to 34-48RC)

 

[TVP]

ASTM A 582 specifies a hardness range of 248-302 for Type 416 in the hardened and tempered condition. Data from Carpenter Stainless Steels book shows as-quenched hardness to be 36-41 HRC (~ 340-385 HB). Tempering in the range of 150-370 C yields ~ 375-390 HB. Neither reference contains any information related to hardenability. ASM Handbook Volume 4 mentions martensitic stainless steels having sufficient hardenability with air cooling up to 300 mm sections, but I think this applies to higher C grades like 420 and 440, and not necessarily to 416. Try contacting someone at Carpenter or Crucible. Maui may have some first hand knowledge on the subject.

 

[metengr]

In one of the lecture series (Lecture 13, Mmat380) on martensitic stainless steels that I had downloaded from the internet some time ago, it was reported that an AISI Type 410 SS shaft can be quench hardened up to 4" in diameter.

 

[swall]

There is a very interesting figure in Heat Treater's Guide--shows end quench hardenability of 410ss. The plot is essentially a horizontal line at Rc 42 all the way to J32. I went to do a round bar conversion on a J32 Jominy value, but my chart stopped at J28, which is equivalent to a 3.75" round bar.But in my experience with 416 and 410, you just can't get 416 to the same hardness level. We could count on Rc 45 max for 410, but 416, in the same section sizes, would max out around 40 or 41. These were relatively small sections, gas quenched in a vacuum furnace.

 

[Metalguy]

The max. hardness of both 410 and 416 depends on the C and C/Cr ratio. But why such a huge range of Rc? Many/most heats of either SS will not get harder than RC45 or 46.

Hope your application is real dry and hot, because using these steels wet at those Rc levels is just begging for HE cracking. Also be aware of how many failures there are when using 416 instead of 410 or 403.

 

[israelkk]

Sorry for the typo error it should have 34-38RC. I actually checked in my previous company warehouse and they have up to 4" diameter of 416H according to ASTM A 582 the bars are at 34-38RC. I do not know if larger diamters are avaiable.

We use 416H for many years for fine pitch pinions and gears for aerospace actuators with no problems. Usually those gears are dry of greased.

 

[Metalguy]

416 is the free-machining grade of 410. It has a lot of S, so it is full of MnS non-metallic inclusions. It's used in most SS rifle barrels, but the stresses must be pretty low. You'll never find it in highly-stressed parts, such as steam turbine blades. The very low S 403 is what's used instead of "regular" 410 for these blades.

In any event, all that Cr means it will through-harden in very large sizes.

 

[Maui]

We have successfully through-hardened 416 rounds as large as 14" diameter. The upper limit in terms of bar diameter that we will quote for heat treated orders is 16". If handeled properly, you should not run into any significant problems in heat treating large rounds of 416.


Maui

 

[israelkk]

Maui

Thanks for the info. Can you refer me to a public data conforming it?

 

[Maui]

Israelkk, the information provided above was obtained from the experience of processing this grade in our Heat Treat department. I do not have a reference that I can give you to a public website that will confirm this information.


Maui