Thanks, metengr for your additional input.
I have looked at the fracture surface on the SEM. Some small areas near the center are ductile (microvoid coalescence - dimpled) and all of the shear lip around the OD is the same. The majority of the surface with the radially oriented ridges are...
Here is the link to the photograph of the fracture. All of my fractures, whether drawn, heat treated and roll threaded or only cold drawn appear as this one does.
<a href="http://tinypic.com" target="_blank"><img src="http://i18.tinypic.com/6czjy8y.jpg" border="0" alt="Image and video hosting...
Based on CoryPad's response, I did some web searching and based on the information I found, combined with the processes my client is using, I think that CoryPad hit the nail on the head. I'm trying to get in touch with who appears to be the expert in central burst defects to get his opinion...
I am investigating a couple of failures in 4140 cold drawn round bar. One material was hot rolled 1-3/8" diameter, the other 1-3/4" diameter. Both were cold drawn to pitch diameter for subsequent thread rolling. After drawing and before threading, the bars were induction heat treated to...
