longitudinal weld refers to the weld along the length of the component. The weld along the length of the member is the longitudinal weld. Movable mouth, that is, groove, is a profile that is machined by machining method in general to weld the workpiece and ensure the welding degree.
when the requirements are not high, gas cutting can also be used (if it is a kind of weld and needs ultrasonic flaw detection, only machining method can be used), but the oxide slag needs to be removed, and there are K-groove, V-groove, U-groove, etc. as required, but most of them require to keep a certain blunt edge.
welding of metal storage tanks-welding sequence and technological measures of tank bottom?
1. welding principle.
The welding process and welding sequence with minimum shrinkage deformation are adopted, and the welding test plate is made at the same time when the pressure vessel is welded. ?
2, tank bottom welding.
welding seam of middle plate: firstly, weld the butt weld 3mm near the edge of the tank bottom edge plate, then weld the fillet weld connecting the wall plate with the tank bottom, then weld the butt weld of the remaining edge plate, and finally weld the shrinkage joint (between the edge plate and the middle plate). ?
3. Welding sequence and welding deformation control measures. ?
middle plate welding: covered electrode arc welding can be used on lap welded joints. Short weld should be welded first, and long weld should be welded later. Step-by-step back welding or skip welding method is suitable for the first pass. ?
welding of edge plate: welders are evenly distributed and symmetrically welded, which is suitable for the first layer welding of butt weld; Segmented retreat welding or skip welding method is suitable for tank wall and tank bottom welding: several pairs of welders are evenly and symmetrically distributed, and segmented fillet welding is carried out in the same direction from the inside and outside of the tank. For the initial layer of weld bead, adopt the method of subsection back welding or skip welding.
Extended information:
Inspection and acceptance of metal storage tanks?
welding residual stress and deformation affect the bearing capacity and manufacturing accuracy of metal storage tanks. In order to reduce welding stress and residual deformation, effective measures should be taken from welding methods, welding processes and assembly procedures. According to the principles of safety, economy, advancement and applicability.
experienced welding quality engineers shall conduct welding procedure qualification, and qualified and effective welders shall conduct welding according to the qualified welding procedure operation manual. Single and comprehensive inspections are carried out on the composite factors of man, machine, material, method and environment, forming pre-welding, during-welding and post-welding inspections. ?
1. Pre-welding inspection
Pre-welding inspection includes but is not limited to the following five points:
(1) Welder qualification matches the actual welding and is within the validity period. In particular, it is emphasized that the welding work is interrupted for 6 months within the validity period of the welder's operation certificate, and the welder's qualification examination needs to be re-conducted;
(2) The welding machine model and power polarity meet the process requirements, and the welding distance, cables, gas pipes, auxiliary tools and safety protection are fully equipped.
(3) The base material, covered electrode, flux, shielding gas and electrode meet the national standards;
(4) The welding structure design, technical documents and process requirements are reasonable, complete and clear, easy to weld and guide, and ensure the quality. Welding process tests should be carried out before welding new materials, new products and new processes;
(5) Reliable protective measures should be taken in welding places with harsh environment.
2. inspection during welding?
(1) During the welding process, relevant requirements of welding process should be implemented, including welding method, material properties, specification requirements, welding sequence, deformation and temperature control;
(2) If there are cracks, bubbles, slag inclusions and other defects between multi-layer welding layers, how to remove the defects;
(3) whether the welding equipment such as welding power supply, wire feeding (walking) mechanism, roller frame, flux bracket and cooling device are operating normally. ?
3. Post-weld inspection?
1) visual inspection.
a, observe the surface defects with a low magnification magnifying glass or naked eyes: undercut, slag inclusion, pores, cracks, etc.
b, inspection of welding inspection ruler: weld excess height, welding burr, depression, staggered mouth, etc.;
c, check the degree of deformation of weldment. ?
2) Irrigation experiment. Water injection test is used to check the tightness and leakage of weldments. Use clean fresh warm water test (≥5℃) (for stainless steel tanks, the requirement for water is higher, and the chloride ion content in water is ≤25PPM). During the test, the foundation settlement should be observed at intervals of about 1m at the lower part of the tank wall (the number of observation points should be a multiple of 4). In case of settlement that does not conform to the design documents, water filling should be suspended, and the next test can be carried out after treatment.