INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

4000 Series Steel vs 1144 Fatigue Proof

4000 Series Steel vs 1144 Fatigue Proof

(OP)
We are currently designing a rather large stationary axle, that has a large moment on the ends of it. The axle is stationary but will see large forces, repeatedly applied, fluctuating from small nominal (almost 0) to a large value. Because of this loading the design is ok in normal loading but fatigue added to a stress concentration at one of the many step downs, fatigue is our limiting factor. We are trying to keep weight and size down for this axle. Currently we are considering using 1144 Fatigue proof or, maybe using a 4000 steel that is heat treated, we are looking for the best cost option betweeen some sort of heat treating and buying the stronger material so that we have 120ksi Yield, and 145ksi tensile, (or similar) anyone have experience making a similar decision? There is a lot of machining that has to happen to this axle which starts around 3.5" diameter down to about 1.5" at the ends, and it is almost 4 ft long, so machine-ability is important.

RE: 4000 Series Steel vs 1144 Fatigue Proof

From the information above, I would consider a 4340 alloy steel, quenched and tempered.

RE: 4000 Series Steel vs 1144 Fatigue Proof

It is difficult to buy small amounts of material with special properties, but in your case a stand-in for fatigue resistance might be transverse impact toughness.
Higher strength will improve fatigue life, but if the structure isn't clean you may not gain much. The are Ca treated steels (for inclusion shape control) that are used for high toughness applications. These would be appropriate for this application.
I would look at 4335 (maybe V mod, or Impact 7) or 4340, and look for some with high transverse toughness. I would go to higher strength also, 140-160ksi yield is easy in these alloys and delivers a good balance of strength, toughness, and fatigue resistance.
If you could find some Timken Impact 7 that would be a great option.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: 4000 Series Steel vs 1144 Fatigue Proof

Why would you even consider using 1144 "Fatigue Proof" for this application? This resulfurized steel is loaded with internal stress risers from all of the sulfides that make cracking easier to initiate and propagate over a properly heat treated 4000-series. Think about it: you would be using a steel that effectively has large numbers of internal longitudinal flaws in it since the sulfides do not do anything for structure. I would be very careful in utilizing such steels in applications such as this stationary axle.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close