Local solution treatment method and device for austenitic stainless steel tube elbow

Abstract

The invention discloses an austenitic stainless steel pipe piece elbow local solid solution treatment method and device. The treatment method is characterized in that a hydraulic manual flatcar is used for feeding a stainless steel pipe piece elbow into an electric heating furnace for heating, homogenizing and heat preservation, the stainless steel pipe piece is quickly far away from the electricheating furnace through the hydraulic manual flatcar after heat preservation, and rapid cooling is achieved through air blowing of a cooling fan. According to the austenitic stainless steel pipe pieceelbow local solid solution treatment method, the deformation temperature and the deformation amount are controlled, so that austenitic stainless steel is uniformly recrystallized, residual stress generated in cold working of a stainless steel pipe is eliminated, and elbow fracture due to stress corrosion and intergranular corrosion is prevented; control is simple, the working procedures are short, and grain refinement efficiency can be greatly improved; and an elbow is continuously bent on one pipe piece, and the elbow on the pip piece is subjected to solid solution treatment at the same time, so that the problems the working amount is large, the flaw detection cost is high and welding deformation is difficult to control due to the fact that the elbow is independently subjected to solid solution and then is welded with the pipe piece are solved.

Description

technical field [0001] The invention relates to a solid solution treatment method and a device thereof, more specifically, to a local solution treatment method and a device for an austenitic stainless steel tube elbow. Background technique [0002] In the boiler industry, there are a large number of U-shaped elbows at both ends of the tube sheet and tube screen. The quality of the U-shaped elbows is related to the normal operation of the entire boiler. At present, the treatment method for U-shaped elbows is mainly solid solution treatment. The treatment is specifically divided into furnace heating treatment, high frequency induction treatment, and electric heating treatment. At present, the treatment method for U-shaped elbows basically adopts furnace-type heating treatment. This method separately heats several U-shaped elbows. The solid solution treatment in the furnace is done, and then it is butt welded with the straight pipe to form the segment. The advantage of this met...

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Problems solved by technology

[0002] In the boiler industry, there are a large number of U-shaped elbows at both ends of the tube sheet and tube screen. The quality of the U-shaped elbows is related to the normal operation of the entire boiler. At present, the treatment method for U-shaped elbows is mainly solid solution treatment. The treatment is specifically divided into furnace heating treatment, high frequency induction treatment, and electric heating treatment. At present, the treatment method for U-shaped elbows basically adopts furnace-type heating treatment. This method separately heats several U-shaped elbows. The solid solution treatment in the furnace is done, and then it is butt welded with the straight pipe to form the segment. The advantage of this method is that it can effectively avoid the sensitization temperature zone, but the manufacturing process is complicated, and the segment needs to be manufactured by hand. The cost is high, and the welding deformation of the segment is difficult to control. For high-frequency induction treatment, the investment cost of the device is large, and the clamping accuracy is high during solution treatment. High-frequency heating treatment is prone to the risk of breakdown of the tube. For electric heating treatment, It is designed using the characteristics of high resistivity of stainless steel tubes, but there is no special power supply for electric heating in the market, and there is no supporting device for stable forming in operation.

[0003] Austenitic stainless steel has high thermal strength, oxidation resistance, corrosion resistance, and good welding performance, so the reheater tube sheet made of it can increase the steam temperature and metal surface temperature of the boiler, but Austenitic stainless steel is sensitive to intergranular corrosion and stress corrosion when the design temperature and forming strain exceed the limit range after cold forming. When the workpiece is subjected to stress in a certain corrosive medium At the same time, the stress corrosion sensitivity of the elbow is greatly increased, and stress corrosion cracks are easily generated, which seriously affects the operation of the boiler. In order to avoid this situation, most domestic boiler manufacturers use austenitic stainless steel to produce stainless steel pipes. After cold forming, solution treatment at 1050°C to 1100°C is carried out to achieve the purpose of repairing the internal structure of the crystal, eliminate the residual stress generated in the process of cold working, and prevent the elbow from breaking due to stress corrosion and intergranular corrosion. However, it is easy to cause overheating, resulting in coarse structure and ferrite structure.

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