現代焊接技術已能焊出無內外缺陷的、機械性能等于甚高于被連接體的焊縫。被焊接體在空間的相互位置稱為焊接接頭，接頭處的強度除受焊縫質量影響外，還與其幾何形狀、尺寸、受力情況和工作條件等有關。

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.

接頭的基本形式：有對接、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.

對接接頭焊縫的橫截面形狀，決定于被焊接體在焊接前的厚度和兩接邊的坡口形式。焊接較厚的鋼板時，為了焊透而在接邊處開出各種形狀的坡口，以便較容易地送入焊條或焊絲。

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.

坡口形式有單面施焊的坡口和兩面施焊的坡口。選擇坡口形式時，除保證焊透外還應考慮施焊方便，填充金屬量少，焊接變形小和坡口加工費用低等因素。厚度不同的兩塊鋼板對接時，為避免截面急劇變化引起嚴重的應力集中，常把較厚的板邊逐漸削薄，達到兩接邊處等厚。對接接頭的靜強度和疲勞強度比其他接頭高。在交變、沖擊載荷下或在低溫高壓容器中工作的聯接，常優先采用對接接頭的焊接。

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.

搭接接頭的焊前準備工作簡單，裝配方便，焊接變形和殘余應力較小，因而在工地安裝接頭和不重要的結構上時常采用。一般來說，搭接接頭不適于在交變載荷、腐蝕介質、高溫或低溫等條件下工作。

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.

采用丁字接頭和角接頭通常是由于結構上的需要。丁字接頭上未焊透的角焊縫工作特點與搭接接頭的角焊縫相似。當焊縫與外力方向垂直時便成為正面角焊縫，這時焊縫表面形狀會引起不同程度的應力集中；焊透的角焊縫受力情況與對接接頭相似。角接頭承載能力低，一般不單獨使用，只有在焊透時，或在內外均有角焊縫時才有所改善，多用于封閉形結構的拐角處。焊接產品比鉚接件、鑄件和鍛件重量輕，對于交通運輸工具來說可以減輕自重，節約能量。焊接的密封性好，適于制造各類容器。

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.