Forge versus Cast Structure

Date 06-07-2012 20:07

I have a 16" dia. forged round shaft part. Among other things, our purchasing specification requires that the cast microstructure must be removed by the forging process.

We have sectioned the "forging" received from the forging supplier longitudinally down the centerline and did a macroetch.

The macroetch showed that the 1-1/2" perimeter (shaft exterior) volume of the etched cross section of the shaft has some worked grain refinement but the center volume of the shaft exhibited a classic "as-cast" etch with extensive large dendritic type fingers / structures evident visually.

The Microetch analysis (100X) exhibits various grain size of less than, greater than, and equal to 5.

We suspect inadequate forging reduction was applied and contend the part is still a casting versus a true forging. Are there standards that would apply to define what is a cast or wrought structure? Are there reference macroetch photographs, etc.?

By G.S.Crisi (****)

Date 06-13-2012 17:49

We must recognize that forging a solid 16 inches (400 millimeters) diameter shaft in its entirety and not just on the periphery, as is your case, is not an easy task.
16 inches is the diameter of a ship's propeller shaft, or a huge Diesel engine crankshaft or a 100 MW steam or gas turbine shaft. Few metalworking shops in the world, shipyards among them, are able to do that.
Sorry, I can't be of any help to you. What I suggest is that you make a search into the ASM site. ASM is the American Society for Metals. They may have some standard or book with the information you're looking for. Their site is: www.asminternational.org
Good luck.
Giovanni S. Crisi
Sao Paulo - Brazil

By DaveBoyer (*****)

Date 06-14-2012 03:16

You should post this question to Patrick Nowak on forgemagic.com. He is a metalurgist at Scott Forge, they do large work.

My guess is You are right about the inadequate reduction, what diameter was the shaft cast to?

By Bill M

Date 06-14-2012 14:06

Thanks for the good leads on this!

By 803056

Date 07-02-2012 15:18

I am not sure where I heard it, but I recollect hearing that the cross section of a casting must be reduced by at least 30% in order to ensure the cast structure is removed.

If my recollection is correct, the question must be asked, "What was the "as cast diameter" that was your starting point?"

Best regards - Al

By DaveBoyer (*****)

Date 07-04-2012 04:12

I don't recall the percentage, but that is where I was going with the second line in My post.

This is a similar problem to that of reduced tensil strength in the Z axis of thick steel plate.

By Len Andersen (***)

Date 07-03-2012 13:20

Ladies and Gentlemen,
I have a background as an engineer in metallurgy five patents welding - new steel. Ran my addresses on your inquiry and found

Forging Industry Association

Forging Industry Educational and Research Foundation
25 W. Prospect Avenue, Suite 300
Cleveland, Ohio 44115

216-781-5040

216-781-0102 FAX

George Mochnal
Technical Man

239-394-5717

info@forgings.org

. What you are contracted to provide would be the determinate of the "matter".
I hope this helpful.
Sincerely
Len Andersen weld@spemail.org
914-536-7101 , 212-839-6599 8-4 New York Time , 914-237-7689 (H) www.lenandersen.com