×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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.

Students Click Here

(Over)heating carburized parts for assembly

(Over)heating carburized parts for assembly

(Over)heating carburized parts for assembly

(OP)
Hello,

I have a bit of a technical challenge, in that we have some geartrain designs that were converted from nitrided helical gears to carburized and ground some years ago. The same diametral shrink fits were carried forward (for example, .0015T/.003T on a 2.75 nominal), which calculates to 440F delta T for a drop-on assembly. We've always heated the gears to expand the bores and fit over room temperature shaft journals.

For those who don't already see the problem, our company standard practice is to keep carburized parts at 325F maximum and nitrided at 600F max. The literature still echoes those numbers. So these shrink fits are easily managed by soaking nitrided parts in our 525F oven, but this is too hot for carburized parts.

I don't think Engineering ever considered that the shrink fits of the nitrided parts will require different assembly methods in carburized material. So the shop has been keeping their ovens at 525F and having no issues with assembly. Most parts aren't in there more than an hour but I've come to learn that some have soaked at 525F for much longer. Fortunately, no performance issues to report, but a situation that we need to address.

One obvious answer is to keep dry ice on hand and shrink the shaft journals. It does add complexity, equipment, and safety hazards to the shop processes, so I owe the company at least another option.

Does anyone have data or practices for how to heat carburized gears to 450-500F and limit the damage? I'm considering taking a handful of heat treat coupons and testing microhardness traverse and grain structure before/after various amounts of time in the 525F oven.

RE: (Over)heating carburized parts for assembly

In our gear heating for assembly operation we never exceed the tempering temperature after carburizing. Our practice is similar to yours for carburized product.

RE: (Over)heating carburized parts for assembly

Can you freeze the mating part, dry ice or liquid nitrogen?

RE: (Over)heating carburized parts for assembly

(OP)

Quote (geesamand)


One obvious answer is to keep dry ice on hand and shrink the shaft journals. It does add complexity, equipment, and safety hazards to the shop processes, so I owe the company at least another option.

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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