1045 vs. 4340

[brane23]

I have a client asking to use 1045 steel in place of our specified 4340 steel. We require 320-360 BHN and our client assures us he can achieve 280-320 BHN with 1045. From what I've read, this seems unlikely. What is a good source for this type of materials information? Thanks!

 

[swall]

You need to supply more information before any of us here can give you a good answer. What is the configuration and section size of the component in question? What is the application?

 

[brane23]

24" P.D.~18T~3/4" D.P. ~5" 4.188 Circ. Pitch

 

[brane23]

Spur Pinion - Industrial use

 

[TVP]

What is the maximum section size (thickness) for this component? I doubt that 1045 has the hardenability necessary for this, and certainly will reduced toughness and fatigue strength. I would not make the change unless the stresses are very low.

 

[brane23]

5"

 

[TVP]

1045 is completely inadequate for through hardening in this type of section size. Only steels with exceptional hardenability can sufficiently quench to near 100% martensite in that type of section size. Your "client" (do you mean vendor/supplier??) apparently does not know what they are doing. The center of a 5" section of 1045 will have a hardness of ~ 225 HB and a microstructure of pure ferrite + pearlite after any type of quench and temper treatment.

 

[unclesyd]

You can achieve your required hardness range from 1045 but it would require a water quench or possibly a polymer quench.
I would not recommend a water/polymer quench for a gear.

My sources are from information supplied by the Old Line Steel Companies for all the products they made. I would check with your supplier to see if he has tempering curves for the products he sells.

There are several books on heat treatment of steels that have tempering curves. I can recall any titles but you could search the ASM website for information.

 

[swall]

It is possible to harden the teeth of the 1045 gear by induction hardening. But as this is a major process and configuration change, the viability would have to be established by testing. Not exactly a "drop in replacement" for a 4340 gear.

 

[dbooker630]

For 1045 to have sufficient induction heat treat response, it is best that the chemistry is a high side composition, i.e. C=/.46-.49, Mn=.80-.90, with some residual Ni-Cr-Mo up to .20 combined. The chemistry still may not help the hardness much if you need 280HB in the core.

 

[lewtam]

I've seen a lot of gears and pinions in 1045 in that size range. All depends on the service - ie, is the normal failure mode wear or does it fail by spitting teeth?

If it is straight wear, then 1045 and 4340 (after suitable heat treatment) are going to behave in a similar fashion. If it is tooth fracture, then 4340 will be the far superior grade.

That said, I say that if it is a small run, just go for the 4340 and be done with it.

LewTam Inc.
Petrophysicist, Leading Hand, Natural Horseman, Prickle Farmer, Crack Shot, Venerable Yogi.