×
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

EDM Cracking_ columnar vs equiaxed structure

EDM Cracking_ columnar vs equiaxed structure

EDM Cracking_ columnar vs equiaxed structure

(OP)
We have an EDM cracking issue to solve. The material was a chill casted alloy with a columnar structure perpendicular to the cutting plane. The alloy is very brittle in nature, we have tried different casting methods to make it cracking free before EDM to cut into slices, using copper mold for a directional solidification. I was wondering if a ceramic mold, or even a sand mold for an equiaxed (but coarser)grain structure could be a better option.

RE: EDM Cracking_ columnar vs equiaxed structure

If you don't need the columnar structure why are you casting on a chill?
We used to cast and slice A9 all of the time.
We cast onto steel chills with exothermic sand molds.
We had to use less S in the material that we sliced than in block material.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: EDM Cracking_ columnar vs equiaxed structure

(OP)
Thanks Ed! Chill was my former colleague idea, I do not like this idea very much because 1. chill caused big thermal stress which led to cracking even on casting during solidification. 2. columnar structure might be the reason material cracked at EDM slicing (for that I am not sure). Mechanical strength and magnetics are not my concerns as long as it does not crack. By the way this is not AlNiCo9, and so anisotropy is not something needed.

RE: EDM Cracking_ columnar vs equiaxed structure

(OP)
Perhaps this is a general question: EDM cut along the grain growth direction is better than cutting across in terms of preventing cracking?!

RE: EDM Cracking_ columnar vs equiaxed structure

I an guessing that this was done because they wanted to cast larger blocks and try to avoid internal shrinkage voids.
I would use standard sand molds.
Are these a simple shape? like round or rectangular
You could line the mold cavities with some ceramic paper/felt to slow cooling, and hot top them.
This will require larger risers though (lower yield).
This should help prevent shrinkage but avoid directional solidification.
We occasionally saw issues cutting large blocks of A9 in either direction.
This was true with both wire EDM and diamond saw.
We tried to not wire EDM, we either plunge EDM cut or simply ground

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

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