Heat treatment of steels 1

[mw1st]

We supply 4140 and 4340 castings in normalized condition. Customer Q&T parts to obtain desired properties (hardness, strength).
My question is: what difference would it make, if these alloys, and plain carbon steel ie. 1045 for that matter, were Q&T without normalizing? How microstructure thus properties would be affected? Is it necessary/ beneficial to normalized first?

Thank you
Mark

 

[metengr]

Mark;
The answer to your question can be found in ASM Metals Handbook, Volume 4 Heat Treating section, which is an authoritative source. Typically, for low alloy steels normalization is done to remove the effects of prior forming or processing of low alloy steel. The primary benefit of normalizing prior to hardening is to provide grain refinement, which ultimately results to more uniform hardening and mechanical properties (less variability). See the excerpt below from ASM Handbook. Volume 4.

Alloy Steels. For alloy steel forgings, rolled products, and castings, normalizing is commonly used as a conditioning treatment before final heat treatment. Normalizing also refines the structures of forgings, rolled products, and castings that have cooled nonuniformly from high temperatures. Table 1 lists typical normalizing temperatures for some standard alloy steels.

 

[mw1st]

Thanks metengr, all makes sense, I should've known that.