AISI 1141 for driveline application 2

[texag]

Recently I discovered that a large manufacturer of commercial and industrial driveline components machines companion flanges out of AISI 1141 resulfurized steel. The part in question is something we would like to manufacture in house but I have doubts about using the same material based on the chemistry and mechanical strengths. ASTM A311 only mentions mechanical requirement up to 3" diameter for Type A and 4.5" diameter for Type B cold drawn steel. Our need would be for 7" diameter and larger.

From the research I have done, resulphurized steel is generally not suitable for fatigue applications due to the poor toughness and high sulfur content. Does anyone have any knowledge of using this steel for high torque (approx 9000ft-lbf) driveline applications?

If anyone has any experience with this steel and its applications I would appreciate the information or knowledge.

 

[metman]

texag,

I do not have direct experience with this application therefore will offer an opinion based on general failure analysis experience and some strength of materials understanding.

If the application were for the torque tube/shaft, I would stay away from resulphurized steel for the reasons found through your research. Torsional stresses in shafts or tubes essentially resolve to patterns of helical tensile stresses and sulfide inclusions can provide initiation sites for fatigue cracks. And everyone knows that we should just say NO to crack (sorry about that crack -- just couldna resist).

On the other hand, for a flange the stress is pure shear if it is a good coupling and I believe would be less sensitive to fatigue provided you design for a large margin below the fatigue limit because localized yielding in shear mode tends to blunt crack leading edges in fatigue.

You are wise to use caution and should wait for some more input from those who understand steel making practice and what effects those practices have on the metallurgy of larger sections that you are proposing.

 

[arunmrao]

The purpose of using sulfurized steel is because of good machinability,however,mechanical properties tend to take a back seat.

I have a doubt,if 1141 steel was accidentally employed and the change unnoticed so far. Please confirm. Else your concerns are very valid and need to take a hard look at using 1141 grade.

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[swall]

Texag--yes, very common to use SAE 1144 for companion flanges for drivelines. But, I do share the concerns of yourself and others about using such for a 7" diameter component. Can you give more detail--will this part start out as a forging or will it be machined from bar? At this point, I am leaning to something more like SAE 4140 or 4150 steel.

 

[dbooker630]

SAE 1141 has been used to make forged connecting rods for many years. You may have them in your vehicle. To some extent it has been replaced by PM in many engines but not for fatigue reasons.

The key with forging is to have sharp trim dies as it is prone to tearing due to the inclusion content. As long as the sulfides are uniformly dispersed, this material typically responds well to forging. It is often microalloyed with Cb or V so that you can use it without subsequent heat treatment.

 

[texag]

swall,

Hypothetically this part would start as annealed or normalized barstock. The companion flange would have a circular bolt pattern on one end to connect to the driveshaft and an internal spline for connecting to a gear. They are rather bell shaped if you are familiar with common commercial driveline flanges, usually called companion flanges. We use a smaller size of this part that is made by the same vendor and out of 1141 and have never had a failure related to that companion flange.

We do use 4140 quite extensively and that would be my material of choice. When I received the information about the manufacturer of these components using 1141 it struck my curiosity as to why. Economics? Availability?


arunmrao,

I am positive of the use of 1141 by this vendor, however there was no indication as to what state it is used in.

 

[CoryPad]

The ONLY reason to use 1141 is to improve machinability, and hence, production economics.

Steels like 1141 can be used in fatigue applications if the loading is primarily along the direction of primary forming. The sulfide stringers are oriented parallel to this direction. However, if you have stresses that are perpendicular to the sulfide stringers, the fatigue resistance is greatly reduced. There is plenty of research in this area, most recently by Fatemi at the University of Toledo.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

There will be a HUGE cost difference between 1141 and 4140 if the production method is turning a 7 inch diameter bar into a flanged shaft. The alloy cost is fairly significant now for anything containing Mo, meaning that instead of paying ~ $800/ton (carbon steels like 1010, 1144, etc.) you will pay ~ $ 940/ton for 4140. Then there is the more significant manufacturing cost. 1141 will machine about 1.6x as fast as 4140, which means that the machining time, labor cost, etc. will be much higher for 4140.

Just my personal opinion here, but I would not specify anything with Mo if it does not really require it. I would look at an alloy grade like 51B40 instead of 4140 for applications requiring quenching and tempering.

 

[texag]

CoryPad,

The loading is primarily torque (torsion), 0-2100RPM, and light to moderate shock loads. Assuming the sulfide stringers are oriented along the axis of the bar a torsion application would be loading perpendicular to those inclusions and thus not recommended based on fatigue failure analysis.

At any rate, thank you all for sharing your knowledge, this has been an informative discussion.

texag

 

[arunmrao]

Corypad,

Earlier we would avoid, Ni and Mo in any alloy to rreduce cost,and add some Mn,Cr,Si,little Va etc.

But now with the current prices of Cr,Mn,and Si alloys what alternatives can be suggested?

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[swall]

Texag--If you wanted to start with a clean sheet of paper, you could make this part incorporating friction welding. You could make the flange out of a disc, of say SAE 1018 and weld it to the bell shaped section made from a medium carbon or low alloy steel. Final machine after friction welding.

 

[CoryPad]

Boron-alloyed steels are a good bargain if you are looking for hardenability for smaller diameter parts. For larger diameter parts, there really aren't great substitutes for Cr, Mo, and Ni. Probably best to use as much Cr as necessary and avoid Mo & Ni. My company is looking to move from 41XX and 43XX into 86XX, 51XX, and 20MnCr5.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dbooker630]

My company is also looking at the 51xx series on certain parts. Toughness is a concern with some applications. The biggest concern that I have was heat-to-heat consistency. It may be necessary to specify a restricted hardenability range to assure consistent heat treatment.

 

[unclesyd]

The largest I've seen 1141 bar is 6" x 60" long.

If anyone knows what happened to the large rotary forge
that was in the Armco Mill in Baltimore you could get any size bar almost any length you need and have upset flanges to boot.


Dbooker630,
You might want to look at 4150 in lieu of 51xx as it has a much smoother hardening curve and is a little stronger.

4150 is available as Maxel 3 1/2 from Crucible Steel. This material has been a workhorse in industry for years. This is all that's left from the Maxel Series from Bethlehem Steel. It was our mainstay for any shafts above 2 1/2".

 

[dbooker630]

Unclesyd,

Yes, we are looking at the 41xx to replace some 43xx applications.

 

[texag]

I am looking at using AISI 1050 annealed for this component. The 10XX series steels are readily available and inexpensive due to lack of high cost alloying elements such as Ni, Cr, and Mo. The higher carbon content allows me to get the required mechanical properties in either the annealed or normalized condition.

Again, thanks all.

texag