Determining the weld stress in steel.

Date 10-25-2005 16:52

A question from a machinist about weld stresses and varying degrees of hardness left me wondering can we determine the stress in welded steel? The piece in question is a gun barrel with the lock piece welded near the chamber. The machinist said he hits hard and soft spots while reaming the bores or reboring the barrels. Would it be possible to heat treat this afterwards to relieve the stress without effecting the steel? The gunsmith claims that with different stresses, the point of impact will be different every shot.
A few barrel makers do weld the action piece to the bottom of the barrel. The welds look terrible (automated welds?). It's generally a hit or miss(no pun intended) on getting a good barrel.
Any suggestions?

By Shane Feder (****)

Date 10-25-2005 21:43

Labtechy,
The company I work for in Australia is using a device called Stress Vision (developed by Dimenstest) to measure residual stresses in welded structures and heat treated components for the mining industry.
It uses the principle of magnetic - anisotropy and by using a special probe and downloading the captured data it can be shown in a 3D picture exactly where the stresses are.
I don't know if this would be of any use for your gun barrels but you can see more about the process at www.stressvision.com
Regards,
Shane

By jwright650 (*****)

Date 10-28-2005 10:40

Shane,
Thanks for sharing, I found this to be very interesting.

Here is what the instrument looks like:
http://www.stressvision.com/images/stories/intro.jpg

Here's where it has mapped out areas of a welded joint:
http://www.stressvision.com/images/stories/defects_in.jpg

John Wright

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

Date 10-27-2005 21:57

Residual stresses in steel are measured also by X-ray difractometry. Until a few years ago, difractometers were large machines located in laboratories, too heavy to be taken to the jobsite for "in loco" (in place) measurements.
Now, they have developed portable machines, suitable to be moved to the jobsite or workshop.
A well known manufacturer is Rigaku, from Japan: www.rigaku.com
I didn't know about the method explained by Shane. I'll enter the website he mentioned and take a look. For sure I'll learn somenthing new.
Giovanni S. Crisi
Sao Paulo - Brazil

By unomike2 Date 11-14-2005 22:42

I know this is late inreplying to this post. But for firearm barrels, I found a process that eliminates stress on the barrel and receivers. I have provided a link to a company for you to check out.

Unomike2

http://www.cryogenicsinternational.com/shooting.htm