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Cold welding or contact welding is a solid-state welding process in which joining takes place without fusion/heating at the interface of the two parts to be welded. Unlike in the fusion-welding processes, no liquid or molten phase is present in the joint. Cold welding was first recognized as a general materials phenomenon in the 1940s. It was then discovered that two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum. Newly discovered micro-〔''Contact Adhesion of Thin Gold Films on Elastomeric Supports: Cold Welding Under Ambient Conditions'', Science, 253, 5021 (16 Aug. 1991), p. 776〕 and nano-scale cold welding〔''Cold welding of ultrathin gold nanowires'', Nature Nanotechnology, Y. Lu et al. 5, (14 Feb. 2010, ), p. 213-224〕 has already shown great potential in the latest nanofabrication processes. Applications include wire stock and electrical connections (such as insulation-displacement connectors). == In space == Mechanical problems in early satellites were sometimes attributed to cold welding. In 2006 the European Space Agency published a peer reviewed paper detailing why cold welding is a significant issue that spacecraft designers need to carefully consider. The conclusions of this study can be found on page 25 of "Assessment of Cold Welding between Separable Contact Surfaces due to Impact and Fretting under Vacuum". The paper also cites a documented example from 1991 with the Galileo spacecraft high-gain antenna (see page 2; the technical source document from NASA regarding the Galileo spacecraft is also provided in a link here). One source of difficulty is that cold welding does not exclude relative motion between the surfaces that are to be joined. This allows the broadly defined notions of galling, fretting, sticking, stiction and adhesion to overlap in some instances. For example, it is possible for a joint to be the result of both cold (or "vacuum") welding and galling (and/or fretting and/or impact). Galling and cold welding, therefore, are not mutually exclusive. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cold welding」の詳細全文を読む スポンサード リンク
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