The welded joint coefficient refers to the ratio of the strength of the butt welded joint to the strength of the base metal. It is used to reflect the extent to which the strength of the welded joint is weakened due to factors such as welding materials, welding defects and welding residual stress, and is a comprehensive reflection of the mechanical properties of the welded joint.
Welding joint coefficient selection method
The welded joint coefficient is only used for the calculation of the strength of the pressure vessel and should be selected according to the weld type and non-destructive testing requirements. The strength of the weld deposit metal should not be lower than the lower limit of the strength of the base material on the lower strength side. The specified coefficient value is based on the premise that the design and manufacturing requirements of the welded joint meet the requirements of Chapter 10 of GB150. E.g:
(1) There shall be no defects such as cracks, delamination and slag inclusion on the surface of the weld bevel;
(2) The surface of the groove before welding and adjacent areas should be removed from oil and so on;
(3). Control the amount of misalignment of the weld seam;
(4) The unequal thickness steel plates are butted, the plate thickness difference is over-limit, and the single and double-sided thinning;
(5) The distance between any Class A welded joints shall be greater than three times the nominal thickness and not less than 100 mm;
(6) Requirements for the remaining height of the welded joint; shall not be more than twice the diameter of the welded rod;
(7) Containers with tensile strength >540 MPa and Cr-Mo and austenitic stainless steels and containers with a weld coefficient of 1 shall not have undercuts on the surface of welded joints; the undercut depth of welded joints of other containers shall not exceed 0.5 mm, which is continuous The length shall not exceed 100mm, and the total length of the undercuts shall not exceed 10% of the length of the weld;
(8) Limit the number of repairs of welded joints to not exceed the regulations and ensure the original corrosion resistance;
(9). The thickness limit shall be heat treated as specified;
(10). If the type A welded joint of the low temperature container is made of a backing plate, it must be removed after welding. If the type B welded joint is restricted by the structure, the backing plate may not be removed;
(11). The cryogenic vessel shall be strictly controlled by the welding process.
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