The classification of welded joints and seams
Welded connection as a structural element called the plot structure in which some of its elements are joined by welding. In the welded joint are welded joint, the adjacent area of the base metal to structural and other changes as a result of the welding thermal (heat affected zone) and the adjacent parts of the base metal. weld metal is crystallized, which was in the process of welding in the molten condition. separation of these concepts is necessary because the weld seam as a connecting portion connected elements defines the geometric shape, continuity, stability and other properties of the metal in the place of welding. The properties of welded joints is determined by properties of the weld metal and base metal zone, adjacent to the seam, restructured, and in many cases with altered properties - heat-affected zone. Must take into account some of the base metal adjacent to the heat-affected zone and determining the stress concentration at the junction of the weld metal to base metal plastic deformation in the second heat-affected zone, thus affecting the nature and distribution of forces acting in the welded joint. The form interface welded elements are the following basic types of welds: Butt (Fig. 1 a), T-(Fig. 1, b and c), angle (Fig. 1d), overlap (Fig. 1 d). Welds divided by the cross-sectional shape in the Butt (Fig. 2a) and angle (Fig. 2b). A variety of these types of joints are cork (Fig. 2c) and the welt (Fig. 2d), performed in the lap joints. The shape of the longitudinal seams distinguish continuous and discontinuous. With the help of butt welds in the main form butt joints (Fig. 1a), with fillet welds - T, cross, corner, and overlap of the compound (Fig. 1b-d) , with cork and slash joints can be formed by overlap and sometimes T-joints. Butt joints tend to perform continuous, the hallmark for them is usually a form of cutting edges of the joined parts in cross section. On this basis distinguish the following basic types of butt welds: Flare the edges (Fig. 3a), without cutting edges - one-sided and bilateral (Fig. 3b), with one edge of butchering - unilateral, bilateral, with a straight or curved shape cuts (Fig. 3, e) with one-sided edges of butchering two, with a V-shaped cut (Fig. 3d), with two edges of butchering two-way, X-shaped cut (Fig. 3e). Cutting can be formed by straight lines (edges beveled) or have a curved shape (U-shaped cutting, Fig. 3, e). Corner joints are distinguished by the form of preparation welded edges in cross section and the continuity of the seam along the length. The shape cross-section of joints may be no cutting edges (Fig. 4a), with one-sided butchering edge (Fig. 4b), with bilateral cutting edges (Fig. 4c). By the length of fillet welds may be continuous (Fig. 5a) and intermittent (Fig. 5b), with a checkerboard (Fig. 5c) and chain (Figure 5d) is the joint-Niemi segments. Fillet, lap and corner joints may be performed by segments of the small extent of seams - seams point (Fig. 5e). cork joints in shape in plan (top view) usually have a round shape and are the result of complete melting of the upper and lower partial melting sheets - they are often called plug lap joint, or by penetration through the top sheet of pre-done on the upper sheet of the hole. welt seams, usually of elongated form, obtained by welding the upper (covering) of the sheet to the bottom fillet weld around the perimeter of the slot. In some cases, the slot can be filled and completely. form cutting edges and assembly welding is characterized by four main structural elements: the gap b, a blunting of the angle beta and bevel angle cutting edges alfa, beta or equal to 2 beta Existing methods of arc welding without cutting edges can be welded metal thickness for a limited one-sided welding hand - up to 4 mm, mechanized submerged arc - up to 18 mm). Therefore, the welding of thick metal edge to carve. The angle of bevel angle provides a certain amount of cutting edges that need to access the arc into the compound and complete penetration on all edges of their thickness. Standard corner cutting edges, depending on the method of cooking and type of connections varies from 60 ± 5 to 20 ± 5 degrees . Type and size of cutting angle cutting edges determine the amount needed to fill the additional metal cutting, and hence the productivity of welding. For example, the X-shaped cutting edge in comparison with the V-shaped to reduce the amount of weld metal in the 1.6 - 1.7 times. Reduced time to process the edges. However, in this case there is a need to weld on one side 1VA in an uncomfortable position, or turn over the overhead workpiece. Dullness is usually from 2 ± 1 mm. Its purpose is to provide the correct formation and prevent burn marks in the top of the seam. The gap b is usually equal to 1.5-2 mm, since the angles of cutting edges taken a gap is necessary for the top seam penetration, but in some cases, a technology gap may be zero or up to 8-10 mm or more. to all types of joints are important edges of a complete penetration of connected elements and the external form of the joint as a front side (the so-called joint gain) and on the reverse side, ie the form of so-called reverse roller. In the butt, especially the joints is difficult to boil thoroughly one-sided edge blunting at full depth without special techniques that prevent burn-through and provide a good reverse bead formation. Also important are the formation of a smooth transition of the metal front and rear rollers to the base metal, as it provides high bond strength under dynamic loads. In the corner seams as it is difficult to boil the root of the weld to the whole of its thickness (see Fig. A, b and c), especially when welding electrode inclined. For these joints is recommended to the concave shape of the cross section of the seam with a smooth transition to the base metal, which reduces stress concentration at the junction and increases the bond strength under dynamic loads.
See also:
Weld Seams and Joints
Laser Welding
Classification of welded joints and seams
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