A method for controlling the grain size uniformity of hot-rolled high-carbon austenitic stainless steel

Abstract

A method for controlling the uniformity of grain size of hot-rolled high-carbon austenitic stainless steel, which is carried out according to the following steps: (1) preparing hot-rolled medium and heavy plates of high-carbon austenitic stainless steel; (2) placing them in a heating furnace for 900~ Preheat at 920°C, preheating time t1=(0.4~0.6)h; (3) The preheating plate heats up to 1000~1010°C with the furnace for recrystallization treatment; ℃, and then put the preheating plate in the heating furnace for recrystallization treatment; (4) the recrystallization plate heats up with the furnace at 50-100 ℃ for solid solution treatment; or takes it out and cools slowly, heats the heating furnace at 50-90 ℃, and The crystal plate is placed in a heating furnace for solid solution treatment; (5) The solid solution plate is water quenched to normal temperature. The method of the present invention focuses on recrystallization kinetics and thermodynamics, adopts a multi-stage stepped annealing process to gradually release the deformation storage energy, and obtains a medium-thick steel plate with uniform grain size and adjustable grain size, which has strong operability , can realize industrial application.

Description

technical field [0001] The invention belongs to the technical field of iron and steel alloy materials, and in particular relates to a method for controlling the grain size uniformity of hot-rolled high-carbon austenitic stainless steel. Background technique [0002] For austenitic stainless steels with special requirements, such as austenitic stainless steels for nuclear power fast reactors, they have long-term service in harsh high-temperature environments and have high requirements for microstructures. They want to obtain stable austenitic microstructures and require better mechanical properties. and high temperature performance, generally more C elements are added; high-carbon (C content is about double that of conventional) austenitic stainless steel generally has a stable single-phase austenite structure, and the grain size and uniformity can only be obtained through recrystallization Behavioral control; however, due to the sensitive diffusion of C with temperature chan...

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Problems solved by technology

[0002] For austenitic stainless steels with special requirements, such as austenitic stainless steels for nuclear power fast reactors, they have long-term service in harsh high-temperature environments and have high requirements for microstructures. They want to obtain stable austenitic microstructures and require better mechanical properties. and high temperature performance, generally more C elements are added; high-carbon (C content is about double that of conventional) austenitic stainless steel generally has a stable single-phase austenite structure, and the grain size and uniformity can only be obtained through recrystallization Behavioral control; however, due to the sensitive diffusion of C with temperature changes and the characteristics of high alloy composition, it will cause obvious recrystallization differences in the hot rolling process, especially for medium and thick plates. The difference in recrystallization or dynamic recovery will form an uneven structure in the rolling state, which will easily cause mixed crystals during annealing, which will deteriorate the mechanical properties and corrosion resistance.

[0003] In the traditional medium and heavy plate hot rolling process, high temperature continuous large reduction hot rolling is generally adopted, the final rolling temperature is ≥ 900 ℃, and natural cooling is adopted after rolling; but for high carbon stainless steel, due to the different deformation temperatures in the thickness direction of the slab , and the distribution of deformation is also quite different, so it will lead to different degrees of dynamic recrystallization and dynamic recovery at different positions. At the same time, some static recrystallization or precipitation of carbides will also occur during the cooling process after rolling, resulting in different microstructures at different positions of plate thickness. Uniform; if the hot rolling process forms an inhomogeneous structure, the subsequent heat treatment will cause static recrystallization and grain growth rates to be different due to the difference in the distribution of deformation storage energy, which will cause the grain boundaries to annex each other, resulting in mixed crystals, and mixed crystals It will greatly deteriorate the high-temperature strength and fatigue properties of the material, which is a very difficult problem in high-carbon stainless steel plates with high performance requirements

[0004] For this reason, relevant personnel have made great improvements to the hot-rolling process; patent CN101724789A has announced a hot-rolled medium-thick plate process, which adopts two stages, and adopts gradual deformation from large to small in the recrystallization zone and non-grain boundary zone respectively. However, it mainly focuses on the change of the mechanical properties of the material, and does not discuss the uniformity of the structure in the hot-rolled state and the full-thickness direction after solution, and the materials used are mainly low-carbon Stainless steel, the comparative example is also low-carbon austenitic stainless steel; in addition, patent CN101748342 has announced a kind of manufacturing method of high-strength 18Cr-8Ni stainless steel hot-rolled medium and thick plate, mainly adopts the mode of high-temperature continuous hot-rolling and on-line solid solution, similarly, The manufacturing method also mainly focuses on the mechanical properties of the material, and does not consider the deformation behavior and structure of the stainless steel in the direction of the entire thickness; The solid solution process or annealing process should be adjusted emphatically, because the final delivery is in a solid solution state, and the structure of the rolled state needs to be adjusted through static recrystallization and grain growth processes

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