2 pieces of stainless steel kept pressed to each other for over 200 days. It was found stuck. What caused it?

Question

Two pices of austenetic stainless steel were kept pressed for over 200 days. After which it was flound that they could not be seperated. The peices had not magnetised, later using a wedge they were seperated. Can any one tell what caused it to stick? Somebody suggested it ws du to poor hardening

Answer 1

Suction.

Answer 2

Certain stainless steels are prone to galling because surface protective films break down and pure metal particles weld together under pressure. It is like two bars of soap sticking together when they dry. When a stainless steel bolt thread contacts say brass threads the metals are different enough not to self weld. Lubricants must often be used to keep stainless steel parts from self welding. In outer space (vacuum) there is no oxygen to make oxide films and many parts that rub off their protective films (such a vibrating hatches?) may stick shut.

Answer 3

The both pieces created a bond between the atoms connected. The same bond, which exists in the material - metallic bond. In other words - atoms connected and the matherial became one single. To do this, the surfaces must be perfect clean plus in this case a pressure was also applied for a long period of time which helped atoms to be close enough to form a bond.

Answer 4

I was told that it was due to compression welding. When 2 pipes are mated very tightly without Teflon tape on the threads to prevent galling, the two pieces of pipe essentially become one. The atoms on the edges of one pipe are compressed close to atoms on the other pipe. Bonds form, and you'll have trouble breaking the pipes loose.

Answer 5

Is it possible that you created a vaccum between the surfaces during pressing? If so consider Stainless steel Diffusion Bonding

This link better explains:
http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/MMTA-0202-437/$FILE/MMTA-0202-437F.pdf

This info was originally told to me by my Metallurgy teacher back in college. The link was a quick hit I found