Form of welded joint: Butt joint; fillet joint; overlap joint

　　Three forms of welded joints

　　1. Butt joint structure: a joint where two interconnected parts are welded in the same plane or in the same arc surface at the joint.

　　Features: Uniform heating, symmetrical force, convenient for non-destructive testing, easy to ensure welding quality.

　　Application: The most common form of welding structure.

　　2. The structure of fillet jiont and T-jiont: The joint of two interconnected parts at the joint is perpendicular to each other or intersects at a certain angle for welding. The joint where the two members are welded together in a T-shape is called a T-joint. Fillet weld is formed in both the corner joint and the t-joint.

　　Features: The structure is discontinuous, the stress state after loading is not as good as the butt joint, the stress concentration is relatively serious, and the welding quality is not easy to be guaranteed.

　　Application: some special parts: welding of connecting pipe, flange, jacket, tube sheet and flange, etc.

　　3. Structure of overlap joint: a joint in which two interconnected parts are partially coincident at the joint and the middle surfaces are parallel to each other for welding.

　　Features: It belongs to fillet welds. Like fillet joints, the structure at the joint is obviously discontinuous, and the load on the joint is poor after loading.

　　Application: Mainly used for welding the reinforcement ring and the shell, the support pad and the wall, and the flange and the container.

　　The groove shapes

　　In order to ensure full penetration and welding quality, and reduce welding deformation, the joints of weldments are generally pre-processed into various shapes before welding.

　　Different welding grooves are suitable for different welding methods and weldment thickness.

　　The basic shapes of the groove: Ⅰ shape, V shape, unilateral V shape, U shape, J shape.

　　Special case of combined shape: general joints should be grooved, and lap joints can be welded without opening grooves.

　　Double V-shaped groove is composed of two V-shaped grooves and one I-shaped groove.