Method for lowering weld seam cracking risk in heat treatment process after welding of large inserting plate of extra-high pressure container

Abstract

The invention discloses a method for lowering a weld seam cracking risk in the heat treatment process after welding of a large inserting plate of an extra-high pressure container, and relates to the technical field of pressure container welding. The method includes the following steps of increasing the width of a weld seam cover; grinding the weld seam cover; determining a heating region, and arranging heating sheets and heat preservation cotton; and carrying out post-welding heat treatment by adopting a six-section three-times symmetric heating mode. The method has the beneficial effects thatby increasing the width of the weld seam cover and combining a mechanical grinding method, the weld seam cover and a base material are made to in smooth transition, stress concentration and tensile welding residual stress at weld seams and weld toes of the large inserting plate of the extra-high pressure container are remarkably lowered, the six-section three-times symmetric heating mode is adopted for post-welding heat treatment, large discordant deformation in the post-welding heat treatment process is avoided, deformation coordination on two sides of the weld seams is improved, and the weld seam cracking risk is effectively lowered.

Description

technical field [0001] The invention relates to the technical field of pressure vessel welding, in particular to a method for reducing the risk of weld seam cracking during post-welding heat treatment of a large insert plate of an ultra-large pressure vessel. Background technique [0002] At present, with the intensification of energy and environmental problems in the world, pressure vessels need to be enlarged. However, due to uneven heating and cooling during the welding process of super-large pressure vessels, residual stress that seriously affects the structural integrity will be generated inside. , it is verified by experiments and numerical simulations that the tensile welding residual stress mainly exists near the surface of the weld, especially at the weld toe. For example, for the welding of large insert plates such as gates on super-large pressure vessels and cylinders, since the thickness of the former is much greater than that of the latter, it is difficult to co...

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Problems solved by technology

However, during post-weld heat treatment, severe longitudinal cracks are likely to occur near the weld toe on the outer surface of the insert plate, and most of the longitudinal cracks exist in the upper and lower parts of the insert plate

Both on-site testing and numerical simulation have proved that the welds at the insert plate and the lower part have large deformations, and because the stiffness of the insert plate is much greater than that of the cylinder, its deformation is much smaller than that of the cylinder, resulting in uncoordinated deformation of the welds The problem is more prominent

[0004] In summary, during the heat treatment process of the large insert plate of a super-large pressure vessel, due to the serious stress concentration at the weld toe, the combined effect of excessive uncoordinated deformation and tensile residual stress, the stress at the weld toe is very fast. Reach the breaking strength of the material at a certain temperature (usually the insulation stage), which eventually leads to cracking of the weld

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