Cold drawn material mechanical properties 1

[Jguili]

Is there a formula for determining the difference in the tensile, yield, elongation and reduction of area, as measured on a cold drawn blank, from that of finished product after it has been cold headed?

We know that if the mechanical properites are measured on the cold drawn blank that these properties will change after cold heading. To date I have only found "experience" as the factor which can determine whether a finished product will meet the required mechanical specifications based on the mechanical properties of the cold drawn blank. If there is some imperical method that may make this a more percice indicator I would greatly appreciate the information.

 

[CoryPad]

Do you have data for flow stress vs. strain (or upset ratio or reduction, etc.)? If so, then calculate how much strain your heading operation produces and compare with your data.

If you don't have data and/or cannot pay to have the testing done, then you can try the technical literature. There are several sources for flow stress data, though they tend to be less-known specialized references. You can try the following:

Wire Journal International

http://www.wirenet.org

International Cold Forging Group

http://www.icfg.info

“New Developments in Forging Technology”, Institute for Metal Forming Technology, University of Stuttgart

http://www.uni-stuttgart.de/ifu/index.en.html

“International Cold Forging Conference”, IMfT & VDI

http://www.imft.co.uk

http://www.vdi.de

 

[Jguili]

Cory,

Thank you for your response. Yes, we have historical (30yrs) data that we developed to determine the required mechanical properties of the drawn material before cold heading to assure that the finished product meets the required mechanical standards.

I sit on a standards committee for some products we manufacture and there are minimum mechanical standards for the product. However, in our standard specification it allows the mechanical properties to be tested either on the cold drawn blank or the finished product. The question was recently raised that if mechanical properties of the drawn blank change during cold heading could the finished part be under the minimum standards. We old timers said we know this from historical reference. That raised the question for some imperical means of calculation or to eliminiate the acceptance of the testing of the drawn blank as acceptable.

Regards,
John