2007-02-02 04:18:23 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
It is now known that the force of adhesion following first contact can be augmented by pressing the metals tightly together, increasing the duration of contact, raising the temperature of the workpieces, or any combination of the above. Research has shown that even for very smooth metals, only the high points of each surface, called asperities, touch the opposing piece. Perhaps as little as a few thousandths of a percent of the total surface is involved. However, these small areas of taction develop powerful molecular connections; electron microscope investigations of contact points reveal that an actual welding of the two surfaces takes place after which it is impossible to discern the former asperitic interface. If the original surfaces are sufficiently smooth the subatomic attractions between contact points eventually draw the two pieces completely together and eliminate even the macroscopic interface.
Exposure to oxygen or certain other reactive compounds produces surface layers which reduce or completely eliminate the cold welding effect. This is especially true if, say, a metal oxide has mechanical properties similar to those of the parent element (or softer), in which case surface deformations do not crack the oxide film.
2007-02-02 18:14:51 · answer #1 · answered by Einstein 2 · 0⤊ 0⤋
Welding two metals without heating them or without fusing them. Friction welding probably comes close to being called a cold welding technique. If you describe the actual welding process, may be I can clarify or comment more.
2007-02-02 04:22:53 · answer #2 · answered by Swamy 7 · 0⤊ 0⤋
In this process when two flat ,clean surfaces of similar metal are brought in contact in vacuum then they strongly adhere to each other. Adhesion between two metal surface occurs by pressing them tightly together, increasing the duration of contact , raising the temperature or any combination of the above. In cold welding pressure is used instead of temperature(heating).
Powders in powder metallurgy use cold welding to best advantage because they present large surface areas over which vacuum contact can occur.
2007-02-02 04:29:55 · answer #3 · answered by vivek 2 · 0⤊ 0⤋
Bonding of two metals together by use of pressure rather than heat. Cleanliness is important to secure a good bond.
2007-02-02 04:21:27 · answer #4 · answered by Anonymous · 0⤊ 0⤋