焊接基础知识 BASIC KNOWLEDGE OF WELDING

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焊接基础知识
BASIC KNOWLEDGE OF WELDING

一、基本知识  Basic knowledge
1.什么叫焊接?   What is welding?
答：用加热或加压等手段，借助金属原子的结合与扩散作用，使分离的金属材料牢固地连接起来的方法。
Welding is one way to join separated metals strongly together through the combination and diffusion of atoms by means of heating and/or pressuring.  
金属焊接方法有40种以上，主要分为熔焊、压焊和钎焊三大类。  
There are more than 40 processes of metallic material welding which could be classified into three main kinds: fusion weld, pressure welding and brazing.
熔焊是在焊接过程中将工件接口加热至熔化状态，不加压力完成焊接的方法。熔焊时，热源将待焊两工件接口处迅速加热熔化，形成熔池。熔池随热源向前移动，冷却后形成连续焊缝而将两工件连接成为一体。
Fusion welding is to fuse the welding interface with heat in welding and without pressure. In fusion welding, the welding interfaces of two materials should be fused in a very short period to form a molten pool. As the heat moves forward, new molten pool forms and the old ones will cool down and form a continuous welding seam which is able to connect two parts firmly together.

在熔焊过程中，如果大气与高温的熔池直接接触，大气中的氧就会氧化金属和各种合金元素。大气中的氮、水蒸汽等进入熔池，还会在随后冷却过程中在焊缝中形成气孔、裂纹等缺陷，恶化焊缝的质量和性能。
However, if the air contacts the heated molten pool in fusion welding, oxygen existing in the air will make metal and other alloy elements oxidized and if nitrogen or steam get into the pool, they will cause porosity, crack and other defects in seam during cooling process and thus cause poor seam quality and property.

为了提高焊接质量，人们研究出了各种保护方法。例如，气体保护电弧焊就是用氩、二氧化碳等气体隔绝大气，以保护焊接时的熔池；又如钢材焊接时，在焊条药皮中加入对氧亲和力大的钛铁粉进行脱氧，就可以保护焊条中有益元素锰、硅等免于氧化而进入熔池，冷却后获得优质焊缝。
In order to improve welding quality, people have worked out many protection methods. For example, gas metal arc welding (GMAW) is to use gases such as argon and carbon oxygen to isolate the molten pool from the air in welding. Adding into the coating of welding wire ferrotitanium powder which could have reaction with oxygen easily will protect elements such as Mn and Si from being oxidized and getting into the pool and promise a high quality seam after it gets cooling down.  

压焊是在加压条件下，使两工件在固态下实现原子间结合，又称固态焊接。常用的压焊工艺是电阻对焊，当电流通过两工件的连接端时，该处因电阻很大而温度上升，当加热至塑性状态时，在压力作用下连接成为一体。
Pressure welding is to make two parts combined at atom level with pressure and without fusing the parts. Therefore it is also called solid-state welding. The most common pressure welding procedure is upset welding. When current flows through the connecting interfaces of two parts which have very high resistance, the temperature here will rise. The two parts will combine as one under pressure if the interfaces are heated into plastic state.
各种压焊方法的共同特点是在焊接过程中施加压力而不加填充材料。多数压焊方法如扩散焊、高频焊、冷压焊等都没有熔化过程，因而没有象熔焊那样的有益合金元素烧损，和有害元素侵入焊缝的问题，从而简化了焊接过程，也改善了焊接安全卫生条件。同时由于加热温度比熔焊低、加热时间短，因而热影响区小。许多难以用熔化焊焊接的材料，往往可以用压焊焊成与母材同等强度的优质接头

钎焊是使用比工件熔点低的金属材料作钎料，将工件和钎料加热到高于钎料熔点、低于工件熔点的温度，利用液态钎料润湿工件，填充接口间隙并与工件实现原子间的相互扩散，从而实现焊接的方法。
In brazing, metallic materials that have lower fusion points than that of the base parts are used as filler metal. When the base material and the filler material are heated to certain temperature that is higher than the fusion point of the filler metal and lower than that of the base material, the liquid filler fill the space between two parts and realize the atomic mutual diffusion between base materials and filler metal and thus join two parts together.
2.什么叫电弧？   What is electric arc?
答：由焊接电源供给的，在两极间产生强烈……


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