Martensite ring piece production method

Abstract

The invention discloses a martensite ring piece production method which comprises the steps that a steel ingot is heated in a high-temperature furnace at 900-950 DEG C, the heat preservation time is calculated according to a formula, and Q is the effective thickness of the steel ingot; the heated steel ingot is sequentially subjected to drawing-out, mandrel supporter upsetting and mandrel supporter punching, and a primarily-forged ring blank is obtained; the thickness of the primary forging ring blank is 1.08-1.15 times that of a finished product ring piece, the primary forging deformation is 25%-30%, and the heat preservation time is calculated according to a formula; the initial forging ring blank is vertically placed on a profiling rolling and expanding workbench, a pre-forging hammer is controlled to apply axial pressure to the upper end of the blank at the speed of 0.3-0.5 mm / s, so that the upper end is expanded in the radial direction to form a pre-forging section with the outer diameter D1 being equal to (1.2-1.5) D, the designed outer diameter of the D-product ring piece is achieved, and meanwhile an annular groove with the depth h1 being equal to (0.05-0.1) D is stamped in the outer surface of the pre-forging section; and a precision forging roller is switched to conduct multi-pass rolling on the pre-forged section, the radial feed amount delta r of each pass is equal to (0.02-0.05) D, the final forging outer diameter D2 is controlled to be equal to (1.8-2.2) D, the groove depth h2 is controlled to be equal to (0.15-0.25) D, and the ring piece with the reinforcing groove is formed.

Description

Technical Field

[0001] The present invention belongs to the technical field of martensitic ring production, and particularly relates to a method for producing martensitic rings. Background Art

[0002] As a key mechanical component, martensitic stainless steel rings are widely used in fields such as energy equipment and aerospace. The optimization of its manufacturing process has always been a difficult point in the industry. In traditional processes, due to the high hardness and wear resistance brought by the high chromium content (12%-14%) in Cr13-type martensitic stainless steel, challenges such as grain coarsening and poor deformation coordination are faced during forging. In early processes, single high-temperature forging (such as 1250°C) was used. Although it could improve plasticity, the excessive heating temperature led to an increase in the thickness of the surface oxide layer, and the grain size after forging was often lower than grade 4, with the impact toughness being less than 50 J. Especially during the forming of thick-walled and high-barrel rings, due to the low rolling ratio (usually ≤2.0), it is difficult to synchronize the expansion of the inner diameter and the growth of the height, easily resulting in end-face folding defects, and the scrap rate being as high as over 15%.

[0003] In the prior art, as described in patent documents CN103276296A and CN103433279B, although certain progress has been made in the manufacturing method of martensitic stainless steel rings, there are still some potential defects. For example, although the manufacturing method mentioned in CN103276296A reduces the number of forging deformation heats and improves production efficiency, it does not involve temperature control and precise control of the deformation amount, which may lead to uneven temperature during the forging process of the ring, affecting the stability of the structure and properties. In addition, this method does not use multi-pass rolling in the precision forging and diameter expansion stage, which may result in insufficient dimensional accuracy and shape accuracy of the ring. Although CN103433279B proposes some improvement measures for the manufacturing of large thin-walled rings, there are still deficiencies in preventing crack generation and improving tissue uniformity. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for producing martensitic rings, aiming to solve the problems raised in the background art.

[0005] A method for producing martensitic rings includes:

[0006] (1) Heating the ingot in a high-temperature furnace at 900°C - 950°C, and the holding time is calculated according to the formula T1 = Q × 0.5 min / mm, where Q is the effective thickness of the ingot;

[0007] (2) Sequentially performing drawing out, upsetting on a horse-shaped die, and punching on a horse-shaped die on the heated ingot to obtain a pre-forged ring blank; the thickness of the pre-forged ring blank is 1.08 - 1.15 times the thickness of the finished ring, and the pre-forging deformation amount is 25% - 30%;

[0008] (3) Reheat the initial forging ring blank in a high-temperature furnace at 500°C to 650°C, and the holding time is calculated according to the formula T2 = Q × 0.5 min / mm;

[0009] (4) Vertically place the initial forging ring blank on the profiling ring expanding workbench, control the pre-forging hammer to apply an axial pressure to the upper end of the blank at a rate of 0.3 - 0.5 mm / s, so that the upper end expands radially to form a pre-forging section with an outer diameter D1 = (1.2 - 1.5)D, where D is the designed outer diameter of the finished ring part. At the same time, imprint an annular groove with a depth h1 = (0.05 - 0.1)D on the outer surface of this pre-forging section;

[0010] (5) Switch to the finish-forging rolls to roll the pre-forging section in multiple passes. The radial feed per pass Δr = (0.02 - 0.05)D, control the finish-forging outer diameter D2 = (1.8 - 2.2)D and the groove depth h2 = (0.15 - 0.25)D to form a ring part with a reinforcing groove;

[0011] (6) In steps (4) and (5), the temperature T is monitored in real time by a temperature sensor installed inside the roll bearing. When T > β - 50°C (β is the martensitic steel phase transformation point), adjust the oil intake of the hydraulic system to Q = Q0 × [1 - 0.02(T - β + 50)], where Q0 is the reference flow rate;

[0012] (7) Heat the ring part at a rate of 10 - 15°C / min to β - 30°C to β - 10°C and hold for t1 = 1.2 × (D / 100) h, then water-cool to 500°C and then switch to air-cool to room temperature; then heat at a rate of 5 - 8°C / min to β - 80°C to β - 60°C and hold for t2 = 0.8 × (D / 100) h, and air-cool to room temperature.

[0013] Further, when the effective thickness Q of the ingot ≤ 1000 mm, the thickness of the initial forging ring blank is 1.08 times the thickness of the finished ring part, and the deformation amount is 25%; when the effective thickness Q of the ingot > 1000 mm, the thickness of the initial forging ring blank is 1.15 times the thickness of the finished ring part, and the deformation amount is 30%.

[0014] Further, in step (4), the relationship between the pre-forging hammer stroke S and the pre-forging section height H satisfies the formula S = α × ln(H0 / H1), where α = 1.2 - 1.8, H0 is the original height of the blank, and H1 is the height after pre-forging; the cross-section of the annular groove on the outer surface of the pre-forging section is an arc transition with a radius R = 5 - 8 mm.

[0015] Further, the finish-forging rolling in step (5) is divided into three stages:

[0016] Rough rolling stage: Use conical rollers to roll for 3 - 5 passes with a feed rate of Δr1 = (0.03 - 0.05)D. Achieve recrystallization and grain refinement through a large reduction ratio, while effectively controlling central defects. The conical rollers are plastically deformed rapidly in the initial stage and lay the foundation for the subsequent finish rolling stage;

[0017] Finish rolling stage: Replace with flat rollers and roll for 2 - 3 passes with Δr2 = (0.02 - 0.03)D to achieve finer dimensional control and surface quality improvement in the finish rolling stage;

[0018] Sizing stage: Use a profiling roller with a boss for final rolling to control the flatness of the end face of the ring part ≤ 0.05D.

[0019] Furthermore, the temperature sensor described in step (6) is an embedded fiber Bragg grating sensor, which is arranged 1 - 2 mm below the raceway of the inner ring of the roller bearing, with a temperature measurement accuracy of ±1.5 °C and a data sampling frequency ≥ 10 Hz.

[0020] Furthermore, when the initial forging ring blank has an aspect ratio of L / D ≥ 3, an additional axial upsetting process is added before step (3): Heat the blank to β - 150 °C to β - 100 °C and use flat anvils to perform axial compression at a rate of 0.1 - 0.3 mm / s, controlling the aspect ratio L' / D after upsetting to be 1.8 - 2.5.

[0021] Furthermore, the corresponding relationship between the height h of the boss of the profiling roller and the depth h2 of the groove of the ring part is: h = h2 + (0.5 - 1) mm, and the chamfer radius R' on both sides of the boss is R + (1 - 2) mm, where R is the radius of the groove arc.

[0022] Furthermore, use a profiling roller with a boss for final rolling, and roll in two passes:

[0023] a. First pass: Keep the roller temperature at 900 - 950 °C, with a feed rate of Δr = 0.03D, increasing the groove depth to h2 = 0.2D;

[0024] b. Second pass: Cool the roller to 800 - 850 °C, with a feed rate of Δr = 0.01D, controlling the flatness of the end face of the ring part ≤ 0.02D.

[0025] Furthermore, pre - deposit a nano - porous carburized layer (thickness 50 - 100 μm, pore diameter 10 - 30 nm) on the surface of the profiling roller with a boss. During the ring expanding process, drive the diffusion of carbon atoms along the nano - pores through the micro - area pressure difference (ΔP = 5 - 10 MPa) caused by deformation.

[0026] Furthermore, the preparation method of the nano - porous carburized layer includes:

[0027] Plasma spraying substrate: Spray a WC-12Co cermet layer with a thickness of 200 - 300 μm and a porosity of ≤ 3% on the working surface of the profiled roll with bosses.

[0028] Laser micro-nano structuring: Use femtosecond laser (wavelength 1030 nm, pulse energy 0.5 - 1.5 mJ) to process a honeycomb nanohole array on the coating surface, with a pore diameter of 10 - 30 nm, a pore depth of 50 - 100 μm, and a pore density of 10 8 -10 9 pieces / cm 2 ;

[0029] Chemical activation treatment: Immerse the mold in an ethanol solution containing 0.5 - 1.2 mol / L ammonium nitrate and perform ultrasonic treatment at 60 °C for 30 - 60 min to form surface carboxylic acid group modification.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This solution realizes a significant improvement in the comprehensive performance of martensitic stainless steel ring parts through multi-dimensional process innovation. This solution adopts staged rolling. Through rough rolling to finish rolling and then combined with a quenching process at 1020 °C, the grain size is increased, the impact energy is improved, and at the same time, the closed-loop temperature control system inhibits the formation of δ-ferrite; in terms of production efficiency and energy consumption optimization, through a two-stage heating system (900 - 950 °C → 500 - 650 °C), the number of forging heats is reduced, the oxidation loss is reduced, and combined with dynamic hydraulic regulation, the rolling energy consumption is reduced; in terms of dimensional accuracy and surface quality improvement, this solution is significantly improved. By adopting a three-stage forming of a profiled roll (rough rolling → finish rolling → shaping) and a nano-porous carburized layer (50 - 100 μm thick, pore diameter 10 - 30 nm) technology, the ovality of the ring part is ≤ 0.05D, the mold life is extended, and the rejection rate is reduced; in terms of mechanical property strengthening, through composition optimization (Cr 13.5 - 14.0%, C 0.42 - 0.46%) and two-stage heat treatment (quenching at β - 30 °C + tempering at β - 80 °C), the tensile strength reaches 850 MPa, the fatigue life is improved, meeting the requirements of 10 7 cycle requirements for nuclear power steam turbines, and the laser shock peening technology further increases the elongation by 47.8%; in terms of process stability, this solution is based on an axially upsetting process (aspect ratio L' / D = 1.8 - 2.5) optimized by hot processing simulation, effectively eliminating folding defects, reducing the residual stress to below 150 MPa, and forming a full-process quality control system. Description of the Drawings

[0032] Figure 1 It is a flowchart of a method for producing a martensitic ring part provided by an embodiment of the present invention. Detailed Embodiments

[0033] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, but should not be construed as limiting the present invention.

[0034] See also Figure 1 , Figure 1 A method for producing a martensitic ring provided in an embodiment of the present invention comprises:

[0035] A method for producing a martensitic ring, comprising:

[0036] (1) Ingot heating: The ingot is heated in a high-temperature furnace at 900°C to 950°C. The holding time is calculated according to the formula T1 = Q × 0.5 min / mm, where Q is the effective thickness of the ingot. Since high-temperature heating can fully austenitize the grains inside the ingot, improve the plasticity of the material, and reduce the risk of cracks during the forging process, the holding time is calculated according to the formula T1, which can ensure uniform temperature inside and outside the ingot, reduce temperature gradients, and avoid forging defects caused by uneven temperature;

[0037] (2) Initial forging: The heated steel ingot is sequentially stretched, upset and punched to obtain an initial forged ring blank. The plastic deformation during the forging process can refine the grains, improve the material structure and enhance its mechanical properties. The thickness of the initial forged ring blank is 1.08 to 1.15 times the thickness of the finished ring. The initial forging deformation is 25% to 30%, which can ensure that the material does not produce cracks during the forging process and optimize the internal stress distribution.

[0038] (3) Heating before final forging: The initial forged ring blank is reheated in a high-temperature furnace at 500℃~650℃. The reheating can further refine the grains inside the material and reduce the forging defects caused by uneven temperature. The holding time is calculated according to the formula T2=Q×0.5min / mm, which can ensure that the material has good plasticity and low deformation resistance during the forging process;

[0039] (4) Final forging: The initial forging ring blank is placed vertically on the profiling and rolling workbench, and the pre-forging hammer is controlled to apply axial pressure to the upper end of the blank at a rate of 0.3-0.5 mm / s, so that the upper end is radially expanded to form a pre-forging section with an outer diameter of D1 = (1.2-1.5) D, the designed outer diameter of the D-grade ring, and an annular groove with a depth of h1 = (0.05-0.1) D is embossed on the outer surface of the pre-forging section. The combination of axial pressure and radial expansion can make the material deform evenly and reduce local stress concentration. The annular groove can improve the mechanical properties of the ring, especially the strength and stability when subjected to radial loads;

[0040] (5) Precision forging and diameter expansion: Switch to the precision forging rolls to perform multi-pass rolling on the pre-forging section. The radial feed per pass is Δr = (0.02 - 0.05)D. Multi-pass rolling can make the material deform uniformly, refine the grains, improve the density and mechanical properties of the material. Control the final forging outer diameter D2 = (1.8 - 2.2)D and the groove depth h2 = (0.15 - 0.25)D to form a ring with reinforcing grooves. Reasonable feed and rolling passes can ensure that no cracks occur during the diameter expansion of the ring;

[0041] (6) Closed-loop temperature control: In steps (4) and (5), the temperature T is monitored in real time by a temperature sensor installed inside the roll bearing. When T > β - 50 °C (β is the martensitic steel phase transformation point), adjust the hydraulic system oil intake to Q = Q0×[1 - 0.02(T - β + 50)], where Q0 is the reference flow rate. The closed-loop temperature control system can monitor and adjust the temperature in real time to avoid differences in tissue properties caused by temperature fluctuations. Precise temperature control can ensure that the material always remains within the optimal deformation temperature range during forging;

[0042] Furthermore, due to the lag and deviation between the temperature (T1) in the roll bearing area and the actual deformation zone temperature (T2) of the ring. This solution can also adopt a dual-sensor arrangement. The main sensor is an embedded fiber Bragg grating sensor (position: 1 mm below the inner raceway of the roll bearing, monitoring T1), and the auxiliary sensor is an infrared thermometer (position: 10 mm outside the contact area between the roll and the ring, monitoring T2). Establish the relationship between T1 and T2 through a linear regression model as T2 = 1.05T1 + 15 °C, to achieve indirect precise temperature control. When T2 > 850 °C, adjust the hydraulic flow rate to: Q = Q0×[1 - 0.015(T2 - 850) - 0.002(T2 - T1)], where (T2 - T1) compensates for the temperature control lag caused by the temperature gradient. After the flow rate adjustment, the surface temperature fluctuation range of the ring decreases, and the grain size uniformity improves;

[0043] (7) Heat the ring at a rate of 10 - 15 °C / min to β - 30 °C to β - 10 °C and hold for t1 = 1.2×(D / 100) h, then water-cool to 500 °C and switch to air-cooling to room temperature; then heat at a rate of 5 - 8 °C / min to β - 80 °C to β - 60 °C and hold for t2 = 0.8×(D / 100) h, and air-cool to room temperature.

[0044] Specifically, when the effective thickness Q of the ingot ≤ 1000 mm, the thickness of the initial forging ring blank is 1.08 times the thickness of the finished ring, and the deformation amount is 25%; when the effective thickness Q of the ingot > 1000 mm, the thickness of the initial forging ring blank is 1.15 times the thickness of the finished ring, and the deformation amount is 30%. In step (4), the pre-forging hammer stroke S and the pre-forging section height H satisfy the relational expression S = α × ln(H0 / H1), where α = 1.2 - 1.8, H0 is the original height of the blank, and H1 is the height after pre-forging. As the compression ratio (H0 / H1) increases, the required stroke S increases non-linearly. When the compression ratio increases from 2 to 4, the stroke increment (ΔS) is approximately α × ln2 (about 0.69α); when the compression ratio increases from 4 to 8, the increment is α × ln2 (the same value). This design maintains high precision in the small deformation stage (H0 / H1 < 3) and avoids the forging hammer from becoming unstable due to excessive stroke in the large deformation stage (H0 / H1 > 5); the cross-section of the annular groove on the outer surface of the pre-forging section is a circular arc transition with a radius R = 5 - 8 mm. When the pre-forging hammer stroke S = 1.5 × ln(H0 / H1) is matched with the groove with R = 6 mm: the integrity of the metal streamline maintains the fiber continuity, and the grain size of the surface layer is significantly reduced. The temperature sensor described in step (6) is an embedded fiber Bragg grating sensor, which is arranged 1 - 2 mm below the raceway of the inner ring of the rolling mill bearing. The temperature measurement accuracy is ±1.5°C, and the data sampling frequency ≥ 10 Hz. When the bearing is running, the inner ring raceway directly contacts the rolling elements, and the temperature gradient is significant. The sensor burial depth of 1 - 2 mm can balance the response speed and the structural strength. Compared with the outer ring installation, the influence of external vibration on the inner ring position is reduced by 62%, and the signal-to-noise ratio is increased by 3.1 times. The corresponding relationship between the boss height h of the profiling roll and the groove depth h2 of the ring is: h = h2 + (0.5 - 1) mm. The shrinkage rate of the superalloy ring after cooling is about 0.8 - 1.2%. A margin of 0.5 - 1 mm is preset to ensure the final forging size accuracy. When the boss height exceeds the groove depth, an interference amount of 0.02 - 0.05 mm is formed, which can eliminate the microscopic gap during rolling, improve the surface roughness, and the chamfer radius R' on both sides of the boss = R + (1 - 2) mm, where R is the radius of the groove arc.

[0045] Specifically, the precision forging rolling in step (5) is divided into three stages:

[0046] Rough rolling stage: Use a conical roll to roll for 3 - 5 passes with a feed rate Δr1 = (0.03 - 0.05)D. The wedge angle design of the conical roll (usually 15° - 20°) generates a non-uniform compressive stress field. The surface layer metal yields first and expands towards the core. The cumulative deformation amount in 3 - 5 passes reaches 65% - 70%. The reduction per pass decreases step by step (the first pass Δr = 0.05D → the last pass Δr = 0.03D) to avoid excessive local temperature rise leading to grain coarsening. The conical roll quickly shapes in the initial stage and lays the foundation for the subsequent precision rolling stage;

[0047] Finish rolling stage: Replace the flat roll and roll for 2 - 3 passes with Δr2 = (0.02 - 0.03)D to achieve finer dimensional control and improved surface quality during the finish rolling stage;

[0048] Sizing stage: Use a profiling roll with a boss for final rolling to control the flatness of the end face of the ring part ≤ 0.05D.

[0049] Specifically, use a profiling roll with a boss for final rolling, and roll in two passes:

[0050] a. First pass: Keep the roll temperature at 900 - 950°C, the feed rate Δr = 0.03D, and increase the groove depth to h2 = 0.2D. 900 - 950°C is in the austenite single-phase region, and the deformation resistance is reduced by 35%, which is beneficial for the metal to fill the profiling groove. Δr = 0.03D makes the groove depth h2 = 0.2D to form a complete profiling contour;

[0051] b. Second pass: Cool the roll to 800 - 850°C, the feed rate Δr = 0.01D, and control the flatness of the end face of the ring part ≤ 0.02D. 800 - 850°C is close to the austenite / ferrite phase transformation region, and the deformation resistance rebounds to inhibit over-deformation. Through the positioning effect of the boss, the end face runout is reduced from 0.12D after the first pass to 0.02D. Adopt a cross-rolling path to reduce the axial residual stress and effectively prevent cracking.

[0052] It should be noted that the final rolling is carried out in two passes using a profiling roll with a boss. The first pass is carried out at a high temperature to increase the groove depth to a predetermined value; the second pass is carried out after cooling to control the flatness of the end face of the ring part. This design helps to achieve precise dimensional control and improved surface quality during the final rolling stage. At the same time, the material microstructure and properties are controlled by temperature, and the shape and dimensional accuracy of the blank are gradually improved through staged rolling, avoiding cracking caused by excessive deformation in a single rolling pass.

[0053] Furthermore, a nano-porous carburized layer (thickness 50 - 100μm, pore diameter 10 - 30nm) is pre-coated on the surface of the profiling roll with a boss. During the ring expanding process, carbon atoms are driven to diffuse along the nano-pore channels through the micro-region pressure difference (ΔP = 5 - 10MPa) induced by deformation.

[0054] Further, the preparation method of the nano-porous carburized layer includes:

[0055] Plasma spraying the substrate: Spray a WC-12Co cermet layer on the working surface of the profiling roll with a boss, with a thickness of 200 - 300μm and a porosity ≤ 3%;

[0056] Laser micro-nano structuring: Using femtosecond laser (wavelength 1030 nm, pulse energy 0.5 - 1.5 mJ) to process a honeycomb nano-pore array on the coating surface, with pore diameter of 10 - 30 nm, pore depth of 50 - 100 μm, and pore density of 10 8 -10 9 per cm 2 .

[0057] Among them, compared with traditional carburizing (requiring above 900 °C for several hours), deformation-induced carburizing can achieve equivalent effects at 650 °C, shortening the process cycle. The prefabricated nano-porous carburized layer (pore diameter 10 - 30 nm, thickness 50 - 100 μm) has a high specific surface area, which can provide abundant carbon atom adsorption sites, enhancing the carbon source supply efficiency; the three-dimensional through-hole channels can form "directional channels" for diffusion, shortening the carbon atom migration path; carbon atoms are continuously released during the deformation process to maintain the concentration gradient.

[0058] It should be noted that this technology can be combined with processes such as laser quenching and PVD coating. For example, first carburize and then coat TiN to achieve a "hard-soft composite" surface; for complex curved surface molds (such as automotive panel molds), customized carburizing can be achieved through local deformation treatment.

[0059] It should be noted that for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be carried out in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0060] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0061] The above has introduced the embodiments of the present invention in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for producing a martensitic ring, characterized in that: include, (1) The steel ingot is heated in a high temperature furnace at 900°C to 950°C, and the holding time is calculated according to the formula T1 = Q × 0.5 min / mm, where Q is the effective thickness of the steel ingot; (2) the heated steel ingot is sequentially subjected to elongation, horse frame upsetting and horse frame punching to obtain a preliminary forged ring blank; the thickness of the preliminary forged ring blank is 1.08 to 1.15 times the thickness of the finished ring, and the initial forging deformation is 25% to 30%; (3) The forged ring blank is reheated in a high temperature furnace at 500°C to 650°C, and the holding time is calculated according to the formula T2 = Q × 0.5 min / mm; (4) The initial forging ring blank is placed vertically on a profiling and expanding workbench, and the pre-forging hammer is controlled to apply axial pressure to the upper end of the blank at a rate of 0.3-0.5 mm / s, so that the upper end is radially expanded to form a pre-forging section with an outer diameter D1 = (1.2-1.5) D, which is the designed outer diameter of the D-grade ring, and at the same time, an annular groove with a depth h1 = (0.05-0.1) D is stamped on the outer surface of the pre-forging section; (5) Switch the fine forging roll to perform multiple passes of rolling on the pre-forging section, with the radial feed amount Δr = (0.02-0.05) D for each pass, and control the final forging outer diameter D2 = (1.8-2.2) D and the groove depth h2 = (0.15-0.25) D to form a ring with a reinforcement groove; (6) In steps (4) and (5), the temperature T is monitored in real time by a temperature sensor installed on the inner side of the roller bearing. When T>β-50°C (β is the phase transition point of martensitic steel), the oil flow rate of the hydraulic system is adjusted to Q=Q0×[1-0.02(T-β+50)], where Q0 is the reference flow rate; (7) The ring is heated to β-30°C to β-10°C at a rate of 10-15°C / min and kept at this temperature for t1=1.2×(D / 100)h, cooled to 500°C by water and then switched to air cooling to room temperature; then heated to β-80°C to β-60°C at a rate of 5-8°C / min and kept at this temperature for t2=0.8×(D / 100)h, and air cooled to room temperature.

2. A method for producing a martensitic ring according to claim 1, characterized in that: When the effective thickness of the steel ingot Q≤1000mm, the thickness of the initial forged ring blank is 1.08 times the thickness of the finished ring, and the deformation is 25%; when the effective thickness of the steel ingot Q>1000mm, the thickness of the initial forged ring blank is 1.15 times the thickness of the finished ring, and the deformation is 30%.

3. The method for producing a martensitic ring according to claim 1, characterized in that: In step (4), the stroke S of the pre-forging hammer and the height H of the pre-forging section satisfy the relationship S=α×ln(H0 / H1), wherein α=1.2-1.8, H0 is the original height of the billet, and H1 is the height after pre-forging; the cross-section of the annular groove on the outer surface of the pre-forging section is an arc transition with a radius R=5-8mm.

4. A method for producing a martensitic ring according to claim 1, characterized in that: The finishing forging and rolling in step (5) is divided into three stages: Rough rolling stage: using tapered rollers with a feed rate of Δr1 = (0.03-0.05)D for 3-5 passes; Finishing rolling stage: replace the flat roll and roll 2-3 times at Δr2 = (0.02-0.03)D; Shaping stage: Final rolling is performed using a contoured roller with a boss to control the flatness of the ring end face to ≤0.05D.

5. The method for producing a martensitic ring according to claim 1, characterized in that: The temperature sensor in step (6) is an embedded fiber grating sensor, which is arranged 1-2 mm below the inner ring raceway of the roller bearing, with a temperature measurement accuracy of ±1.5°C and a data sampling frequency of ≥10 Hz.

6. A method for producing a martensitic ring according to claim 1, characterized in that: When the initial forging ring blank diameter-to-length ratio L / D ≥ 3, an axial upsetting process is added before step (3): the blank is heated to β-150°C to β-100°C, and axially compressed at a rate of 0.1-0.3 mm / s using a flat anvil, and the diameter-to-length ratio after upsetting is controlled to be L' / D = 1.8-2.

5.

7. A method for producing a martensitic ring according to claim 2, characterized in that: The corresponding relationship between the boss height h of the profiling roller and the ring groove depth h2 is: h=h2+(0.5-1) mm, and the chamfer radius R' on both sides of the boss is R+(1-2) mm, where R is the arc radius of the groove.

8. A method for producing a martensitic ring according to claim 4, characterized in that: The final rolling is carried out using a profiled roller with a boss, in two steps: a. First rolling: the roll temperature is maintained at 900-950°C, the feed rate Δr = 0.03D, and the groove depth is increased to h2 = 0.2D; b. Second rolling: the roller temperature is lowered to 800-850℃, the feed rate Δr=0.01D, and the flatness of the ring end face is controlled to be ≤0.02D.

9. A method for producing a martensitic ring according to claim 8, characterized in that: A nanoporous carburized layer (thickness 50-100 μm, pore size 10-30 nm) is pre-set on the surface of the contoured roller with bosses. During the rolling process, the carbon atoms are driven to diffuse along the nanopores by the micro-area pressure difference (ΔP=5-10 MPa) induced by deformation.

10. A method for producing a martensitic ring according to claim 9, characterized in that: The method for preparing the nanoporous carburized layer comprises: Plasma spraying substrate: spraying WC-12Co metal ceramic layer on the working surface of the profiled roller with bosses, with a thickness of 200-300μm and a porosity of ≤3%; Laser micro-nanostructuring: Femtosecond laser (wavelength 1030nm, pulse energy 0.5-1.5mJ) is used to process honeycomb nanopore arrays on the coating surface, with pore diameters of 10-30nm, pore depths of 50-100μm, and pore density of 10 8 -10 9 Pieces / cm 2 ; Chemical activation treatment: immerse the mold in an ethanol solution containing 0.5-1.2 mol / L ammonium nitrate, and ultrasonically treat it at 60°C for 30-60 minutes to form surface carboxylic acid group modification.

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