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A-Arm material

A-Arm material

(OP)
Is there any possible reason to use 4140 pre-hard to make the machined parts (that the spechrcals mount into) on a set of racecar A-arms.  The parts will be normalized, but not heat treated, I can't see how theyr'ed be ANY reason to use pre-hard, with the welding and normalizing.  

The prints for some of the parts have pre-hard as the material, but I don't understand why.

Thanks,
Chuck

RE: A-Arm material

If the only machining that would be done is light finish grinding, you can get a much higher strength from Q&T parts.

After welding the 4140 would have to be heat treated to remove the HAZ from welding, I dont know the specifics on the time and or temps thoug.

RE: A-Arm material

(OP)
well, I'm talking about some lathe turned parts that will be welded to some 4130 tube on a fixture.  It'd then get normalized afterwords, as opposed to heat treated.  I was wondering why parts in a weldment would be pre-hard.

RE: A-Arm material

Yeah, that is funny. sorry....

RE: A-Arm material

GTMule,

One idea is that the pre-hardened 4140 parts would not be welded, but instead would be low temperature brazed using a bronze alloy (often called TIG brazing).  Provided the brazing temperature is below the tempering temperature, you can have your cake and eat it too with regards to HT properties and ability to be joined.

RE: A-Arm material

Some sizes and shapes are commonly stocked pre-heat treated to around Rc 25 -35 or thereabouts. In thick sections the hardness was of very limited depth.

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