Method for controlling size uniformity of hot rolled high-carbon austenitic stainless steel grains

Abstract

The invention discloses a method for controlling the size uniformity of hot rolled high-carbon austenitic stainless steel grains. The method comprises the following steps: 1, preparing a high-carbon austenitic stainless steel hot rolled medium plate; 2, putting the medium plate in a heating furnace of 900-920 DEG C for preheating, wherein the preheating time t1 is equal to 0.4-0.6 hour; 3, raisingthe temperature of the preheated plate to 1000-1010 DEG C along with the furnace for recrystallization treatment, or taking the preheated plate out for slow cooling, warming the heating furnace to 1000-1010 DEG C, and then putting the preheated plate in the heating furnace for recrystallization treatment; 4, raising the temperature of the recrystallization plate by 50-100 DEG C along with the furnace for solution treatment, or taking the recrystallization plate out for slow cooling, raising the temperature of the heating furnace by 50-90 DEG C, and then putting the recrystallization plate inthe heating furnace for solution treatment; and 5, carrying out water quenching on a solid solution plate to the normal temperature. According to the method, the recrystallization kinetics and the thermodynamics are taken as the acting points, the multi-stage stepped type annealing technology is adopted to release deformation stored energy step by step, the medium plate with uniform grains and adjustable and controllable grain size is obtained, the maneuverability is high, and industrial application can be realized.

Description

technical field [0001] The invention belongs to the technical field of iron and steel alloy materials, in particular 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 changes and the ...

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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 rolled structure, 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 greatly improved the hot-rolling process; patent CN101724789 A has announced a kind of hot-rolled plate process, which adopts two stages, in the recrystallization zone and in the non-grain boundary zone respectively adopts step by step from large to small The way of deformation, and then a solid solution at a certain temperature; but 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, 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 plate, mainly adopts the mode of high-temperature continuous hot-rolling and on-line solid solution, same , its manufacturing method also mainly focuses on the mechanical properties of the material, without considering the deformation behavior and microstructure of the stainless steel in the direction of the entire thickness; More emphasis should be placed on regulating the solid solution process or annealing process, because the final delivery is in a solid solution state, and the structure in the rolling state needs to be adjusted through static recrystallization and grain growth processes

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