Thermal treatment method for preventing stainless steel from being sensitized in water chamber of high-pressure heater

Abstract

The invention relates to the technical field of heat treatment, in particular relates to a thermal treatment method for preventing stainless steel from being sensitized in a water chamber of a high-pressure heater, and aims at solving the problems that the stainless steel is sensitized and the expanding quality is bad caused by the large difference of linear expansion factors since materials of a pipe are different during the heat treatment after the girth welding of the water chamber of the high-pressure heater. The thermal treatment method is characterized in that the thermal treatment method is carried out on an outer housing, a thick pipe plate and a U-shaped pipe of the high-pressure heater, a welding line and a heat affected zone of the water chamber are annealed by the local heat treatment, and a thermal insulation carpet is arranged at the welding line side of the stainless steel to prevent heat energy to be directly radiated to a stainless steel part, so that the temperature of the stainless steel part can not be risen to the sensitization temperature. The temperature of the stainless steel part can not be risen to the sensitization temperature, the anti-scouring function of the U-shaped pipe can be improved, the pipe exposure accident rate of the equipment can be reduced, and the service life of the equipment can be prolonged.

Description

technical field [0001] The invention relates to the technical field of heat treatment, in particular to a heat treatment method for preventing sensitization of stainless steel in a water chamber of a high-pressure heater. Background technique [0002] The high-pressure heater uses the steam that has been worked in the high and medium pressure cylinders of the steam turbine to heat the boiler feed water, and is an important power station auxiliary equipment to improve the efficiency of the power plant. The high-pressure heater is a surface heat exchanger, and its biggest feature is the high water side pressure and high manufacturing requirements. It is generally a welded structure, mainly composed of a water chamber, a shell, a thick tube sheet and a U-shaped tube. According to the requirements of the high-pressure heater specification, the heat treatment temperature after girth welding is in the sensitization temperature range of stainless steel. If no measures are taken, ...

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Problems solved by technology

[0004] The purpose of the present invention is to solve the problem of preventing the sensitization of stainless steel pipes and the expansion joint quality caused by the large difference in the linear expansion coefficients of different tube and tube sheet materials in the post-welding heat

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