4340 QTSR Class BD, After Machining

[gase]

4340 QTSR Class BD 7.5" dia through hardened shaft

Will the machining process, after treated, change any properties or weaken the shaft?

 

[redpicker]

Not enough information, but the answer is probably.

It depends on the specification the material is produced to meet. 7.5" is pretty large, and the mechanical properties with Q&T low alloy steel in these large sections is going to be dependent on depth below the surface. The material specification should detail the test location; either 1/2 radius or 1/4 radius are common. The point is, at depths below the location the material was tested, mechanical properties will generally be less. How much you machine from the surface is important.

So, it depends on what material specification the material was produced to meet and how much you are going to machine from the surface. Of course, it also depends on what you mean be weaken, since simply maching the OD will reduce the cross section, which, in the most general sense, weaken the shaft.

rp

 

[EdStainless]

It is not uncommon for the test reports on large diameter heat treated bar to contain properties for near surface and mid-radius locations.
Your machining won't change anything, but you may cut away higher strength material.

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