Technology for welding carbon steel overlaying welding layer of tube plate of high pressure heat exchanger with low carbon steel tube in sealing way

Abstract

The invention discloses a technology for welding a carbon steel overlaying welding layer of a tube plate of a high pressure heat exchanger with a low carbon steel tube in a sealing way, comprising the following technological processes, i.e. a step one of welding carbon steel on the tube plate of the high pressure heat exchanger in a submerged arc overlaying way, thermally treating the overlaying welding layer and the tube plate under the condition of passing 100% UT (Ultrasonic Test) and 100% MT (Magnetic Test) flow detection, and increasing the overlaying welding layer to the range of 6mm to 8mm in a machining way, wherein the groove structure of the tube plate is in the form of an aligned groove, the low carbon steel tube is aligned with the overlaying welding layer of the tube plate, and the sealing welding groove of the overlaying welding layer of the tube plate is chamfered at 2*45 degrees; a step two of preheating to 80 DEG to 100 DEG before welding, and welding the low carbon steel tube in the groove of the overlaying welding layer of the tube plate in a point way before welding as well, wherein the point welding enables the root part to be thoroughly welded without welding sticks; a step three of implementing sealing welding on the groove by adopting an automatic argon arc welding, implementing 100% PT (Penetration Test) flow detection on the welded junction after the completion of sealing welding, and eliminating surface defects of the welding line. According to the technology for welding the carbon steel overlaying welding layer of the tube plate of the high pressure heat exchanger with the low carbon steel tube in the sealing way, the surface of the welding line of the carbon steel subjected to the sealing welding is smooth and flat, and no needle-like air holes are formed in the near surface and the surface of the welding line; therefore, the long-term scour by supplied water can be completely withstood.

Description

technical field [0001] The invention relates to a sealing welding process between a surfacing layer and a low-carbon steel pipe, in particular to a sealing welding process between a carbon steel surfacing layer of a high-pressure heat exchanger tube plate and a low-carbon steel pipe, and belongs to the field of welding technology. [0002] Background technique [0003] 300-600MW high-pressure heater (hereinafter referred to as high-pressure heater) low-carbon steel tube plate is sealed and welded, and its function is to ensure that the water in the high-pressure water chamber flows into the U-shaped tube to exchange heat with the steam on the shell side. The working pressure of the 300MW high-pressure water heater is 18-20MPa, more than 3,000 welding joints, 600MW supercritical supercritical water supply pressure is 29-32MPa, more than 6,000 welding joints, such as the original high-plus low-carbon steel pipe plate structure is a low-carbon steel pipe extension pipe The pla...

AI Technical Summary

Problems solved by technology

[0004] Due to the above two reasons, sealing welding leakage often occurs during the operation of the power plant. As long as one welding joint has pores on the surface or near the surface, and due to the high water supply pressure of the high water adding chamber and the high resistance of the sealing welding structure to the water supply, In a short period of time, the weld seam is flushed into a small hole and the sealing weld leaks