现代焊接技术已能焊出无内外缺陷的、机械性能等于甚高于被连接体的焊缝。被焊接体在空间的相互位置称为焊接接头，接头处的强度除受焊缝质量影响外，还与其几何形状、尺寸、受力情况和工作条件等有关。

Modern welding technology has been able to weld the weld without internal and external defects, whose mechanical properties are equal to or even higher than the connected body. The mutual position of the welded body in space is called welded joint. The strength of the joint is not only affected by the quality of the weld, but also related to its geometry, size, stress and working conditions.

接头的基本形式：有对接、搭接、丁字接(正交接)和角接等。

The basic forms of joints are butt joint, lap joint, T-joint (forward joint) and corner joint.

对接接头焊缝的横截面形状，决定于被焊接体在焊接前的厚度和两接边的坡口形式。焊接较厚的钢板时，为了焊透而在接边处开出各种形状的坡口，以便较容易地送入焊条或焊丝。

The cross section shape of butt joint depends on the thickness of the welded body before welding and the groove form of the two edges. When welding thick steel plate, in order to weld through, the groove of various shapes is made at the edge, so that the welding rod or welding wire can be easily put in.

坡口形式有单面施焊的坡口和两面施焊的坡口。选择坡口形式时，除保证焊透外还应考虑施焊方便，填充金属量少，焊接变形小和坡口加工费用低等因素。厚度不同的两块钢板对接时，为避免截面急剧变化引起严重的应力集中，常把较厚的板边逐渐削薄，达到两接边处等厚。对接接头的静强度和疲劳强度比其他接头高。在交变、冲击载荷下或在低温高压容器中工作的联接，常优先采用对接接头的焊接。

There are two types of groove: one side welding groove and two sides welding groove. When selecting the groove form, in addition to ensuring the penetration, the factors such as convenient welding, less filler metal, small welding deformation and low groove processing cost should also be considered. When two steel plates with different thickness butt joint, in order to avoid the serious stress concentration caused by the sharp change of cross section, the thicker plate edge is often gradually thinned to achieve the same thickness at the two joint edges. The static strength and fatigue strength of butt joint are higher than other joints. Butt joint welding is often preferred for joints working under alternating and impact loads or in low temperature and high pressure vessels.

搭接接头的焊前准备工作简单，装配方便，焊接变形和残余应力较小，因而在工地安装接头和不重要的结构上时常采用。一般来说，搭接接头不适于在交变载荷、腐蚀介质、高温或低温等条件下工作。

The lap joint has the advantages of simple preparation before welding, convenient assembly, small welding deformation and residual stress, so it is often used in the field installation of joints and unimportant structures. Generally speaking, lap joints are not suitable for working under alternating load, corrosive medium, high temperature or low temperature.

采用丁字接头和角接头通常是由于结构上的需要。丁字接头上未焊透的角焊缝工作特点与搭接接头的角焊缝相似。当焊缝与外力方向垂直时便成为正面角焊缝，这时焊缝表面形状会引起不同程度的应力集中；焊透的角焊缝受力情况与对接接头相似。角接头承载能力低，一般不单独使用，只有在焊透时，或在内外均有角焊缝时才有所改善，多用于封闭形结构的拐角处。焊接产品比铆接件、铸件和锻件重量轻，对于交通运输工具来说可以减轻自重，节约能量。焊接的密封性好，适于制造各类容器。

The use of T-joints and corner joints is usually due to structural needs. The working characteristics of fillet weld with incomplete penetration on T-joint are similar to those of lap joint. When the weld is perpendicular to the direction of the external force, it becomes a positive fillet weld, and the shape of the weld surface will cause different degrees of stress concentration; the stress condition of the penetrated fillet weld is similar to that of the butt joint. The bearing capacity of fillet joint is low, so it is not used alone. It can be improved only when it is fully welded or when there are fillet welds inside and outside. It is mostly used in the corner of closed structure. Welding products are lighter than riveting parts, castings and forgings, which can reduce self weight and save energy for transportation vehicles. The sealing performance of welding is good, which is suitable for manufacturing all kinds of containers.