CN-115522041-B - Process for accelerating high-temperature tissue stabilization of 9Cr heat-resistant steel weld joint

Abstract

The invention discloses a process method for accelerating high-temperature tissue stabilization of a 9Cr heat-resistant steel weld joint, and belongs to the technical field of heat treatment of metal materials. And heating the welded 9Cr heat-resistant steel weld joint to 720-780 ℃ by adopting a post-welding heat treatment process for the 9Cr heat-resistant steel weld joint which needs to be in service under the long-term high temperature condition, preserving heat for 1-4 hours, cooling to below 200 ℃ along with a furnace, discharging from the furnace, air cooling to room temperature, and performing subsequent high-temperature long-term aging treatment. The process can lead the weld joint structure of the 9Cr heat-resistant steel to reach a stable state before aging treatment, has small performance change under the subsequent long-term high-temperature service condition, ensures the stability and the safety of the whole structure of the part, and avoids obvious deterioration of the performance caused by the structural change of the weld joint under the long-term high-temperature condition due to direct use under the welding state condition, and the possibility of accident occurrence is increased due to the damage of the stability of the whole structure.

Inventors

• XU HAITAO
• LU SHANPING
• YAN CHUNGUANG
• WEI SHITONG
• HAN LIQING
• RONG LIJIAN
• YANG HONGYI
• LI YIYI

Assignees

• 中国原子能科学研究院
• 中国科学院金属研究所

Dates

Publication Date

20260512

Application Date

20221012

Claims (2)

1. 1. A process for accelerating the high-temperature tissue stabilization of a 9Cr heat-resistant steel welding seam is characterized in that the process is used for carrying out heat treatment on the 9Cr heat-resistant steel welding seam which needs to be put into service under the condition of long-term high temperature; The heat treatment process comprises heating the welded 9Cr heat-resistant steel weld seam to 720-750deg.C with a heat treatment furnace, maintaining the temperature for 2.5-4 hr, cooling to below 200deg.C, and air cooling to room temperature; The 9Cr heat-resistant steel comprises the following chemical components in percentage by mass ：C 1.0%、Si 1.1%、Mn 1.2%、Nb 0.08%、 V 0.20% 、Cr 9.0%、 Ni 1.0%、 Mo 0.8%、 N 0.04%、 P<0.005%、 S 0.003%、Fe as the rest.
2. 2. The process for accelerating the high-temperature tissue stabilization of the 9Cr heat-resistant steel weld seam according to claim 1, wherein the mechanical property of the 9Cr heat-resistant steel weld seam after heat treatment is that the tensile strength is more than or equal to 600MPa, the yield strength is more than or equal to 500MPa and the elongation is more than or equal to 17 percent after aging at 550 ℃ for 3000 hours.

Description

Process for accelerating high-temperature tissue stabilization of 9Cr heat-resistant steel weld joint Technical Field The invention relates to the technical field of material heat treatment, in particular to a process for accelerating the high-temperature tissue stabilization of a 9Cr heat-resistant steel weld joint. Background The development of new materials is one of main bottlenecks for restricting the development of advanced nuclear energy, determines the feasibility, safety and economy of a nuclear energy system, and the 9Cr heat-resistant steel is a structural material for nuclear power parts which is widely applied due to the excellent mechanical property, good low activation and low thermal expansion rate. As a structural material for nuclear power, the 9Cr heat-resistant steel has the advantages that when the 9Cr heat-resistant steel is in long-term service at high temperature, the structure is aged, and meanwhile, the mechanical property of the 9Cr heat-resistant steel is obviously degraded. And the evolution of the microstructure in the creep process determines the degradation of mechanical properties. The degradation mechanism of the 9Cr heat-resistant steel in the long-term high-temperature service process mainly comprises the change of dislocation substructure and the change of precipitated phase, the dislocation density is obviously reduced after the long-term service, a large number of dislocations are mutually counteracted, or are absorbed by grain boundaries and subgrain boundaries, or are mutually entangled into dislocation walls to be converted into subgrain boundaries, so that lath martensite is broken and recrystallized, and meanwhile, the subgrain is coarsened and gradually becomes an equiaxial structure from an initial lath shape. In addition, the precipitation has very important roles in relation to the high-temperature endurance strength of 9Cr heat-resistant steel, some of the precipitation phases in the steel coarsen along with the extension of time, some of the precipitation phases dissolve and turn into other thermodynamically more stable coarse precipitation phases, and even the solid solution strengthening elements in the matrix are consumed to precipitate new precipitation phases. These structural and performance changes in the material can disrupt the overall structural stability of the component and increase the likelihood of an accident. The 9Cr heat-resistant steel weld joint also has the problems that the structure of the 9Cr heat-resistant steel weld joint needs to be stabilized before use, so that the 9Cr heat-resistant steel weld joint is ensured to have smaller performance change under the subsequent long-term high-temperature service condition, and the stability of the whole structure of the part is ensured. Disclosure of Invention In order to solve the problems that the structural change of the welding seam under the condition of a welding state causes obvious deterioration of performance, the stability of the whole structure is destroyed, the possibility of accident occurrence is increased and the like when the 9Cr heat-resistant steel welding seam is directly used under the condition of a welding state, the invention aims to provide a process for accelerating the high-temperature structural stabilization of the 9Cr heat-resistant steel welding seam, the process can lead the 9Cr heat-resistant steel welding seam structure to reach a stabilized state before aging treatment, the performance change is smaller under the condition of subsequent long-term high-temperature service, and the stability and the safety of the whole structure of a part are ensured. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: A technology for accelerating the high-temperature tissue stabilization of 9Cr heat-resistant steel welding seams is to heat treat the 9Cr heat-resistant steel welding seams which are required to be in service under the long-term high-temperature condition. The heat treatment process is that a heat treatment furnace is used for heating the welding seam of the 9Cr heat-resistant steel in a welded state to 720-780 ℃ after welding, and the heat is preserved for 1-4 hours. In the heat treatment process, a 9Cr heat-resistant steel welding seam adopts a furnace-following heating mode, and the heating rate is more than or equal to 1 ℃ per minute. And after the heat preservation is finished, cooling to below 200 ℃ along with the furnace, discharging from the furnace, and air cooling to room temperature. So that the weld joint structure of the 9Cr heat-resistant steel reaches a stable state, and the performance of the 9Cr heat-resistant steel has small change under the subsequent long-term high-temperature service condition. The mechanical property of the 9Cr heat-resistant steel weld joint after heat treatment is that the tensile strength is more than or equal to 600MPa, the yield strength is more than or equal to 500MPa an