One-side welding with back formation welding method for large double-layer cylinder of nuclear power station

Abstract

The invention discloses a one-side welding with back formation welding method for a large double-layer cylinder of a nuclear power station. Gas metal arc welding is used, proper bevel angles and welding process parameters are adopted, a backing weld is subjected to semi-automatic welding, filling and capping welds are subjected to automatic welding, and efficient one-side welding with back formation is realized. According to the welding method, argon-rich mixed gas is used as protective gas, backing welding adopts small current parameters, the transient mode of controlling molten drops includes short-circuit transition and spray transition, a welding gun swings and temporarily stays at a truncated edge in backing welding, and through welding is ensured. The molten drop transient mode of the filling and capping welds includes pulsed spray transition, welding efficiency can be effectively improved, welding heat input is reduced, and welding deformation is decreased. The welding method is suitable for field welding, and stable welding quality can be ensured when local assembling alignment tolerance or clearance of a weldment is large and cannot be adjusted.

Description

technical field [0001] The invention relates to a single-side welding and double-side forming welding method for a large-scale double-layer cylinder of a nuclear power plant, which belongs to the technical field of steel structure welding of nuclear power plants. Background technique [0002] The reactor building of the large-scale advanced pressurized water reactor nuclear power plant CAP1400 nuclear power plant has a double-layer containment structure, the inner shell is a steel containment CV, and the outer shell is a shielding wall composed of a concrete structure and an SC structure. The SC structure of the shielding wall is a double-layer cylinder structure. The distance between the inner and outer cylinders is about 1.1m, the outer radius is 23.985m, the inner radius is 22.885m, and the total height is about 50m. The thickness of steel plates at different elevations are 20, 25, 40mm, the steel plate material is Q345B, the total length of SC structural welds is about 2...

AI Technical Summary

Problems solved by technology

Manual arc welding to achieve single-sided welding and double-sided forming requires very high skill requirements for welders, and the welding efficiency is low; the welding efficiency of argon tungsten arc welding is also low, and argon tungsten arc welding has very high requirements for the assembly of weldments. The invention patent "High-efficiency combined automatic TIG welding process for thick plate butt joint" (application publication number CN 106378516A) discloses a high-efficiency combined automatic TIG welding process for thick plate butt joint. 0~2mm, but in the construction process of large-scale cylinder structures, there will often be cases where the local assembly gap and misalignment exceed the above range, so the above assembly requirements cannot be met

[0004] The invention patent "A Method for Single-sided Welding of Thick Plates" (application publication number CN 105643066A) discloses a single-sided welding method for thick plates. The grooves created by this welding method include the first groove and the second groove. The mouth processing is more complicated, and it is necessary to lay flux on the groove for multi-wire submerged arc welding. For the horizontal seam and vertical seam welding of the nuclear power plant shell structure, special equipment is required to protect the flux, which increases the cost

The invention patent "A high-efficiency welding method for single-pass single-side welding and double-sided forming of medium-thick plates" (authorized announcement number CN 103551711B) provides a high-efficiency welding method for medium-thick plate single-pass single-side welding and double-sided forming. However, this welding method requires a double-arc composite heat source as a primer, and requires multiple welding machines and multiple welding torches, resulting in a large number of power lines for welding machines, which increases the complexity of the nuclear power plant site

Invention patent "Fully-automatic melting extremely rich argon mixed gas shielded welding single-sided welding double-sided forming bottoming method" (application publication number CN 104096957A) announced a fully automatic melting extremely rich argon mixed gas shielded single-sided welding double-sided forming Bottom method, this method uses a welding robot for welding, the equipment cost is high, and the robot welding method has very high requirements on the gap between the weldment assembly and the amount of misalignment of the assembly, and there is a large gap that cannot be adjusted locally in the large cylinder structure of the nuclear power plant And the amount of misalignment can not guarantee the welding quality

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