Gas welding

A method of joining metals using the heat of combustion of a mixture of fuel gas and oxygen. The weld may or may not be pressurized during welding, and may be performed using a welding rod depending on the type of workpiece, plate thickness, and shape of the joint. Gas welding is the general term for methods of welding metals using various gas flames, but the most common method is to use an oxy-acetylene flame to melt the workpiece and weld it, so gas welding generally refers to oxy-acetylene welding. Oxyhydrogen welding has a lower flame temperature than the former, so it is used for metals with low melting points, while oxypropane welding is inexpensive and safe, but because the flame temperature is low it is not often used for welding, and is used for brazing.

On the other hand, gas pressure welding is a method in which two objects to be welded are heated with a gas flame and compressed perpendicularly to the joint surface to join them. The method in which the objects to be welded are heated and compressed while first pressing them together is called the closed method, while the method in which the welded surfaces are first separated and heated separately, and then when they melt, they are brought together by impact to join them under pressure is called the open method. In this case, an oxy-acetylene flame is generally used for heating.

[Takeshi Kuwana]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

燃料ガスと酸素との混合物の燃焼熱を利用して金属を接合する方法。溶接に際し溶接部を加圧することもあり、また被溶接物の種類、板厚、継手(つぎて)の形状によって、溶接棒を用いる場合と用いない場合とがある。各種のガス炎を用いて金属を溶接する方法をガス溶接と総称するが、酸素アセチレン炎を用い被溶接物を溶融して溶接することがもっとも多く、一般にガス溶接といえば酸素アセチレン溶接をさすと考えてよい。酸水素溶接は前者に比して火炎温度が低いため低融点の金属に用いられ、酸素プロパン溶接は安価で安全性は高いが、炎の温度が低いため溶接としては多用されず、ろう付けに用いられる。

　一方、ガス圧接法は、二つの被圧縮物をガス炎で加熱し、接合面に垂直に圧縮力を加えて接合する方法である。あらかじめ被圧接物を互いに加圧しながら加熱圧縮して接合する方法をクローズ法といい、また、初め圧接面を離して別々に加熱し、溶融したところで衝撃的に両者をあわせて加圧接合する方法をオープン法という。この場合、加熱には一般に酸素アセチレン炎を用いる。

［桑名　武］

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