1144 carburized

[Steve898]

Man, I love 1144 questions. As usual, everyone that is not a metallurgist wants to use it for everything. I have induction hardened, flame hardened, marquenched, austempered (!), oil and water quenched, fixture tempered, carburized, unameitidunit. It just machines so well and is much cheaper than those expensive high-end alloys like 8620.

My question is this: Are you aware of a use for this material for gears that is carburized? What is your experience?

Thanks in advance for any information you can provide.

 

[Carburize]

It is not mentioned in AGMA 2004 "Gear Materials and Heat Treatment Manual" as a carburizing grade.
Typically carburized gear steels have maximum carbon contents of ~0.2%. The aim of the low carbon core is to provide a material with reasonable toughness after the low temperature temper of the case.

 

[Steve898]

Thank you for the prompt reply.

1144 carburized, hardened, tempered 350F will be very hard at the surface, and will be at or over 50 HRC in the core (not over 1/2" cross section). If toughness is not a requirement yet high wear properties are, then there seems to be no reason to avoid 1144.

 

[Carburize]

The gear rating standard AGMA 2001 gives a caution concerning "low ductility" material defined in that document as less than 10% elongation. I think the core of carburized 1144 probably falls under the caution!

 

[TVP]

I agree with Carburize. The core toughness will be extremely low, and if the gear has any substantial load, fatigue and fracture will be a concern. What does the inside of the gear mate against? What is the nature of the connection (spline, keyway, dog, etc.)?

 

[Steve898]

I have carburized 4140 and 4340 gears that, I was told at the time, were very demanding applications, probably military, since we certified to (obsolete)mil spec. Effective case depth was defined at 58 HRC instead of 50 HRC. I imagine the core toughness was extremely low for those gears, but it did not seem to be an issue.

keyway.

 

[unclesyd]

To get 50 Rc at the core of a 1/2" 1144 bar you will have to quench in water. The Izod impact for this material tempered at 325°F is "2". Tempering below 400°F isn't normally recommended for this material.

 

[Steve898]

Where did you find that information?

 

[unclesyd]

Modern Steels and Their Properties
Bethlehem Steel
Circa. 1952

 

[NickE]

YOu cna alos interpret and interpolate the information contained here:

http://www.timken.com/timken_ols/steel/handbook/

 

[Steve898]

Well, there is a real lack of real information on this material when used to carburize. At far as the hardenability, a 1/2" section will quench out to over 50 HRC since it quenches all over and not just from 1 direction. I've done it.

You must have my copies of the Bethlehem book, I used to have 3 of them and they disappeared. I've been looking for them.

 

[unclesyd]

No I don't, as I got mine from Bethlehem's Chief Metallurgist in 1959 or 1960 when we were arguing about the presence of lead causing cracking in some A2 Tool Steel that we had made some very complex parts from. Even though I won the argument he still gave me a copy of the book.

1144 as quenched (water):

Looking at the data for 1/2" round the surface is 58 RC, 1/2 radius is 53 RC, and the center is 50 Rc.

For 1" the surface is 57 RC, 1/2 radius is 33 RC, and the center is 29 RC.

 

[Steve898]

I had a friend that gave me his books when he passed away. Surprisingly there were 3 of the Bethlehem book, 2 were red hardbacks, 1 was a silver softcover.

There was some lead in some A2? That does not sound good.
Thank you for the info.