A method for producing martensitic rings

Abstract

This invention discloses a method for producing martensitic rings. The method includes heating a steel ingot in a high-temperature furnace at 900℃~950℃, calculating the holding time according to a formula, where Q is the effective thickness of the steel ingot; sequentially drawing, upsetting, and punching the heated steel ingot to obtain a preliminary forged ring blank; the thickness of the preliminary forged ring blank is 1.08~1.15 times the thickness of the finished ring, the preliminary forging deformation is 25%~30%, and the holding time is calculated according to a formula; the preliminary forged ring blank is vertically placed on a contour rolling and expanding worktable, and the pre-forging hammer is controlled at a speed of 0.3-0.5mm / s. An axial pressure is applied to the upper end of the billet, causing the upper end to expand radially to form a pre-forged section with an outer diameter D1 = (1.2-1.5)D, which is the designed outer diameter of the ring part. At the same time, an annular groove with a depth h1 = (0.05-0.1)D is imprinted on the outer surface of the pre-forged section. The pre-forged section is then rolled in multiple passes using precision forging rolls, with a radial feed amount Δr = (0.02-0.05)D per pass. The final forging outer diameter D2 = (1.8-2.2)D and the groove depth h2 = (0.15-0.25)D are controlled to form a ring part with a reinforcing groove.

Description

Technical Field

[0001] This invention belongs to the field of martensitic ring manufacturing technology, and specifically relates to a method for manufacturing martensitic rings. Background Technology

[0002] Martensitic stainless steel rings are key mechanical components widely used in energy equipment, aerospace, and other fields. Optimizing their manufacturing process has always been a challenge for the industry. In traditional processes, Cr13 type martensitic stainless steel, due to its high chromium content (12%-14%), exhibits high hardness and wear resistance, but faces challenges such as grain coarsening and poor deformation coordination during forging. Early processes used a single high-temperature forging method (e.g., 1250℃), which improved plasticity, but the excessively high heating temperature led to a thicker surface oxide layer, and the post-forging grain size was often below grade 4, with an impact toughness of less than 50J. Especially in the forming of thick-walled, high-cylinder rings, due to the low rolling ratio (usually ≤2.0), the inner diameter expansion and height increase are difficult to synchronize, easily resulting in end-face folding defects, with a scrap rate as high as 15% or more.

[0003] While prior art, as described in patent documents CN103276296A and CN103433279B, has made some progress in the manufacturing methods of martensitic stainless steel rings, some potential defects still exist. For example, although the manufacturing method mentioned in CN103276296A reduces the number of forging deformation passes and improves production efficiency, it does not involve precise control of temperature and deformation amount, which may lead to uneven temperature of the ring during forging, affecting the stability of its microstructure and properties. Furthermore, the method does not employ multi-pass rolling in the precision forging and diameter expansion stage, which may result in insufficient dimensional and shape accuracy of the ring. Although CN103433279B proposes some improvements for the manufacturing of large, thin-walled rings, it still has shortcomings in preventing crack initiation and improving microstructure uniformity. Summary of the Invention

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

[0005] A method for manufacturing martensitic rings, comprising,

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

[0007] (2) The heated steel ingot is sequentially drawn, upset and punched to obtain a preliminary forging ring blank; the thickness of the preliminary forging ring blank is 1.08 to 1.15 times the thickness of the finished ring, and the preliminary forging deformation is 25% to 30%.

[0008] (3) The initial forging ring billet is heated a second time in a high-temperature furnace at 500℃~650℃, and the holding time is calculated according to the formula T2=Q×0.5min / mm;

[0009] (4) The initial forging ring blank is placed vertically on the contour rolling and expanding worktable. 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 design outer diameter of the ring part. At the same time, an annular groove with a depth h1 = (0.05-0.1)D is imprinted on the outer surface of the pre-forging section.

[0010] (5) Switch the precision forging rolls to perform multiple passes of rolling on the pre-forging section. The radial feed amount Δr = (0.02-0.05)D per pass, 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 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℃ (β is the phase transformation point of martensitic steel), the oil inlet of the hydraulic system is adjusted to Q = Q0 × [1 - 0.02(T - β + 50)], where Q0 is the reference flow rate;

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

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

[0014] Furthermore, in step (4), the pre-forging hammer stroke S and the pre-forging section height H satisfy the relationship S=α×ln(H0 / H1), where 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 a circular arc transition with a radius R=5-8mm.

[0015] Furthermore, the precision forging and rolling in step (5) is divided into three stages:

[0016] Roughing stage: Using tapered rolls with a feed rate Δr1 = (0.03-0.05)D, 3-5 passes are rolled. A large reduction is used to achieve recrystallization and grain refinement, while effectively controlling center defects. The tapered rolls rapidly shape the grain in the initial stage and lay the foundation for the subsequent finishing stage.

[0017] Finishing stage: Replace with flat rolls and roll 2-3 times with Δr2=(0.02-0.03)D to achieve finer dimensional control and improved surface quality in the finishing stage;

[0018] Shaping stage: Use profile rolling mills with bosses for final rolling, and control the flatness of the ring end face to be ≤0.05D.

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

[0020] Furthermore, when the diameter-to-length ratio L / D of the forged ring billet is ≥3, an axial upsetting process is added before step (3): the billet is heated to β-150℃~β-100℃, and axial compression is performed using a flat anvil at a rate of 0.1-0.3mm / s, and the diameter-to-length ratio L' / D after upsetting is controlled to be 1.8-2.5.

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

[0022] Furthermore, a contour roll with a boss is used for final rolling, which is performed in two stages:

[0023] a. First rolling: The roll temperature is maintained at 900-950℃, and the feed rate Δr = 0.03D, so that the groove depth is increased to h2 = 0.2D;

[0024] b. Second rolling: The roll temperature is reduced to 800-850℃, the feed rate Δr=0.01D, and the flatness of the ring end face is controlled to be ≤0.02D.

[0025] Furthermore, a nanoporous carburized layer (thickness 50-100μm, pore size 10-30nm) is pre-placed on the surface of the contour roll with protrusions. During the rolling process, carbon atoms are driven to diffuse along the nanopores by the micro-area pressure difference (ΔP=5-10MPa) induced by deformation.

[0026] Furthermore, the preparation method of the nanoporous carburized layer includes:

[0027] Plasma-sprayed substrate: A WC-12Co metal ceramic layer with a thickness of 200-300μm and a porosity of ≤3% is sprayed onto the working surface of the contour roll with bosses.

[0028] Laser-based micro / nano structuring: A honeycomb-like nanopore array is fabricated on the coating surface using a femtosecond laser (wavelength 1030 nm, pulse energy 0.5-1.5 mJ). The pore size is 10-30 nm, the pore depth is 50-100 μm, and the pore density is 10-1. 8 -10 9 pcs / cm 2 ;

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

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

[0031] This solution achieves a significant improvement in the overall performance of martensitic stainless steel rings through multi-dimensional process innovation. It employs a staged rolling process, combining rough rolling to finish rolling with a 1020℃ quenching process to improve grain size and impact energy. Simultaneously, a closed-loop temperature control system suppresses the formation of δ-ferrite. Regarding production efficiency and energy consumption optimization, a two-stage heating regime (900-950℃ → 500-650℃) reduces the number of forging passes and oxidation losses, while dynamic hydraulic adjustment further reduces rolling energy consumption. This solution also improves dimensional accuracy and surface quality. Significant improvements have been achieved through the use of a three-stage forming process with contour rolls (roughing → finishing → shaping) and a nanoporous carburized layer (50-100μm thick, pore size 10-30nm), resulting in an ellipticity of ≤0.05D for the rings, extended die life, and reduced scrap rate. In terms of mechanical property enhancement, composition optimization (Cr 13.5-14.0%, C 0.42-0.46%) and two-stage heat treatment (β-30℃ quenching + β-80℃ tempering) have resulted in a tensile strength of 850MPa and improved fatigue life, meeting the requirements for 10-year lifespan in nuclear power turbines. 7 The laser shock peening technology further improves the elongation rate by 47.8% in the second cycle requirement; in terms of process stability, this solution is based on the axial upsetting process (diameter-to-length ratio L' / D = 1.8-2.5) optimized by thermal processing simulation, which effectively eliminates folding defects and reduces residual stress to below 150MPa, forming a full-process quality control system. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for producing martensitic rings according to an embodiment of the present invention. Detailed Implementation

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

[0034] See Figure 1 , Figure 1 A method for producing martensitic rings according to an embodiment of the present invention includes:

[0035] A method for manufacturing martensitic rings, comprising,

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

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

[0038] (3) Pre-forging heating: The initial forging ring billet is heated twice in a high-temperature furnace at 500℃~650℃. The second heating can further refine the grains inside the material and reduce 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 a contour rolling and expanding worktable. 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, causing the upper end to expand radially to form a pre-forging section with an outer diameter D1 = (1.2-1.5)D, which is the designed outer diameter of the ring part. At the same time, an annular groove with a depth h1 = (0.05-0.1)D is imprinted on the outer surface of the pre-forging section. The combination of axial pressure and radial expansion can make the material deform uniformly and reduce local stress concentration. The annular groove can improve the mechanical properties of the ring part, especially its strength and stability under radial load.

[0040] (5) Precision forging and diameter expansion: The precision forging rolls are switched to perform multi-pass rolling on the pre-forging section. The radial feed amount per pass is Δr = (0.02-0.05)D. Multi-pass rolling can make the material deform uniformly, refine the grains, and improve the density and mechanical properties of the material. The final forging outer diameter D2 = (1.8-2.2)D and the groove depth h2 = (0.15-0.25)D are controlled to form a ring with a reinforcing groove. Reasonable feed amount and rolling passes can ensure that the ring does not crack during the diameter expansion process.

[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℃ (β is the phase transformation point of martensitic steel), the oil inlet of the hydraulic system is adjusted 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 microstructure and properties caused by temperature fluctuations. Precise temperature control can ensure that the material is always kept within the optimal deformation temperature range during the forging process;

[0042] Furthermore, due to the lag and deviation between the temperature in the roll bearing area (T1) and the actual deformation zone temperature of the ring (T2), this solution can also employ a dual-sensor arrangement. The main sensor is an embedded fiber optic grating sensor (located 1mm below the inner ring raceway of the roll bearing, monitoring T1), and the auxiliary sensor is an infrared thermometer (located 10mm outside the contact area between the roll and the ring, monitoring T2). A linear regression model is used to establish the relationship between T1 and T2: T2 = 1.05T1 + 15℃, achieving indirect and precise temperature control. When T2 > 850℃, the hydraulic flow rate is adjusted to: Q = Q0 × [1 - 0.015(T2 - 850) - 0.002(T2 - T1)], where (T2 - T1) compensates for the temperature lag caused by the temperature gradient. After flow rate adjustment, the surface temperature fluctuation range of the ring is reduced, and the grain size uniformity is improved.

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

[0044] Specifically, when the effective thickness of the steel ingot Q ≤ 1000 mm, the initial forging ring billet thickness is 1.08 times the finished ring thickness, and the deformation is 25%; when the effective thickness of the steel ingot Q > 1000 mm, the initial forging ring billet thickness is 1.15 times the finished ring thickness, and the deformation is 30%. In step (4), the pre-forging hammer stroke S and the pre-forging section height H satisfy the relationship S = α × ln(H0 / H1), where α = 1.2-1.8, H0 is the original height of the billet, 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 (approximately 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 instability of the forging hammer 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 = 5-8mm. When the pre-forging hammer stroke S = 1.5 × ln(H0 / H1) matches the groove with R = 6mm: the integrity of the metal flow lines is maintained, the fiber continuity is maintained, and the surface layer grain size is significantly reduced. The temperature sensor mentioned in step (6) is an embedded fiber optic grating sensor, which is arranged 1-2mm below the inner ring raceway of the roll bearing. The temperature measurement accuracy is ±1.5℃, and the data sampling frequency is ≥10Hz. When the bearing is running, the inner ring raceway directly contacts the rolling element, and the temperature gradient... Significant improvement: The sensor burial depth of 1-2mm can balance response speed and structural strength. Compared with the outer ring installation, the inner ring position is less affected by external vibration by 62%, and the signal-to-noise ratio is improved by 3.1 times. The corresponding relationship between the boss height h and the groove depth h2 of the conforming roll is: h = h2 + (0.5-1)mm. The shrinkage rate of the high-temperature alloy ring after cooling is about 0.8-1.2%. A 0.5-1mm allowance is set to ensure the final forging dimensional accuracy. When the boss height exceeds the groove depth, an interference of 0.02-0.05mm is formed, which can eliminate the micro gaps in the rolling process and improve the surface roughness. The chamfer radius R' on both sides of the boss is R + (1-2)mm, where R is the radius of the groove arc.

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

[0046] In the roughing stage: tapered rolls are used with a feed rate Δr1 = (0.03-0.05)D for 3-5 passes. The wedge angle design of the tapered rolls (usually 15°-20°) generates a non-uniform compressive stress field, causing the surface metal to yield preferentially and extend towards the core. The cumulative deformation in 3-5 passes reaches 65%-70%, and the reduction in each pass decreases in a stepwise manner (first pass Δr = 0.05D → last pass Δr = 0.03D), avoiding excessively rapid local temperature rise that could lead to grain coarsening. The tapered rolls rapidly shape the grain in the initial stage and lay the foundation for the subsequent finishing rolling stage.

[0047] Finishing stage: Replace with flat rolls and roll 2-3 times with Δr2=(0.02-0.03)D to achieve finer dimensional control and improved surface quality in the finishing stage;

[0048] Shaping stage: Use profile rolling mills with bosses for final rolling, and control the flatness of the ring end face to be ≤0.05D.

[0049] Specifically, a contour roll with a boss is used for final rolling, which is performed in two stages:

[0050] a. First rolling: The roll temperature is maintained at 900-950℃, and the feed rate Δr = 0.03D, so that the groove depth increases to h2 = 0.2D. 900-950℃ is in the austenitic single-phase region, and the deformation resistance is reduced by 35%, which is conducive to the metal filling the contour groove. Δr = 0.03D makes the groove depth h2 = 0.2D, forming a complete contour.

[0051] b. Second rolling: The roll temperature is reduced to 800-850℃, the feed rate Δr=0.01D, the flatness of the ring end face is controlled to be ≤0.02D, 800-850℃ is close to the austenite / ferrite phase transformation zone, the deformation resistance is increased, and over-deformation is suppressed. Through the positioning effect of the boss, the end face runout is reduced from 0.12D after the first rolling to 0.02D. The cross rolling path is adopted, the axial residual stress is reduced, and cracking is effectively prevented.

[0052] It should be noted that the final rolling process involves two stages using contour rolls with bosses. The first rolling is performed at high temperature to increase the groove depth to a predetermined value; the second rolling is performed after cooling to control the flatness of the ring end face. This design helps achieve precise dimensional control and improved surface quality in the final rolling stage. Simultaneously, temperature control of material microstructure and properties allows for phased rolling to gradually improve the shape and dimensional accuracy of the billet, avoiding excessive deformation in a single rolling cycle that could lead to material cracking.

[0053] Furthermore, a nanoporous carburized layer (thickness 50-100μm, pore size 10-30nm) is pre-placed on the surface of the contour roll with protrusions. During the rolling process, carbon atoms are driven to diffuse along the nanopores by the micro-area pressure difference (ΔP=5-10MPa) induced by deformation.

[0054] Furthermore, the preparation method of the nanoporous carburized layer includes:

[0055] Plasma-sprayed substrate: A WC-12Co metal ceramic layer with a thickness of 200-300μm and a porosity of ≤3% is sprayed onto the working surface of the contour roll with bosses.

[0056] Laser-based micro / nano structuring: A honeycomb-like nanopore array is fabricated on the coating surface using a femtosecond laser (wavelength 1030 nm, pulse energy 0.5-1.5 mJ). The pore size is 10-30 nm, the pore depth is 50-100 μm, and the pore density is 10-1. 8 -10 9 pcs / cm 2 .

[0057] Compared to traditional carburizing (which requires temperatures above 900℃ and several hours), deformation-induced carburizing can achieve equivalent results at 650℃, shortening the process cycle. The pre-placed nanoporous carburizing layer (pore size 10-30nm, thickness 50-100μm) has a high specific surface area, providing abundant carbon atom adsorption sites and enhancing carbon source supply efficiency. The three-dimensional through-pores can form diffusion "directional channels," shortening the carbon atom migration path. Carbon atoms are continuously released during the deformation process, maintaining the concentration gradient.

[0058] It should be noted that this technology can be combined with processes such as laser hardening and PVD coating. For example, carburizing followed by TiN coating can achieve a "soft-hard composite" surface. For complex curved molds (such as automotive body panel molds), customized carburizing can be achieved through local deformation treatment.

[0059] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are 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 different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0061] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for producing martensitic rings, characterized in that, include, (1) Heat the steel ingot in a high-temperature furnace at 900℃~950℃, and hold it for the specified time according to the formula. Calculate, where Q is the effective thickness of the steel ingot; (2) The heated steel ingot is sequentially drawn, upset, and punched to obtain a preliminary forging ring blank; the thickness of the preliminary forging ring blank is 1.08 to 1.15 times the thickness of the finished ring, and the preliminary forging deformation is 25% to 30%; (3) The initial forged ring billet is reheated in a high-temperature furnace at 500℃~650℃, and the holding time is calculated according to the formula. calculate; (4) The initial forging ring blank is placed vertically on the contour rolling and expanding worktable. 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 design outer diameter of the ring part. At the same time, an annular groove with a depth h1 = (0.05-0.1)D is imprinted on the outer surface of the pre-forging section. (5) Switch the precision forging rolls to perform multiple passes of rolling on the pre-forging section. The radial feed amount Δr = (0.02-0.05)D per pass, 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 groove; (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℃ (β is the phase transformation point of martensitic steel), the oil inlet of the hydraulic system is adjusted to Q = Q0 × [1 - 0.02(T - β + 50)], where Q0 is the reference flow rate; (7) Heat the ring to β-30℃~β-10℃ at a rate of 10-15℃ / min and hold for t1=1.2×(D / 100)h, water cool to 500℃ and then switch to air cooling to room temperature; then heat to β-80℃~β-60℃ at a rate of 5-8℃ / min and hold for t2=0.8×(D / 100)h, and air cool to room temperature.

2. The method for producing a martensitic ring according to claim 1, characterized in that, When the effective thickness of the steel ingot Q ≤ 1000 mm, the initial forging ring blank thickness is 1.08 times the thickness of the finished ring, and the deformation is 25%; when the effective thickness of the steel ingot Q > 1000 mm, the initial forging ring blank thickness 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 following relationship: Where 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 a circular arc transition with a radius R = 5-8 mm.

4. The method for producing a martensitic ring according to claim 1, characterized in that, Step (5) involves three stages of precision forging and rolling: Roughing stage: Use tapered rolls to roll 3-5 times with a feed rate Δr1 = (0.03-0.05)D; Finishing stage: Replace with flat rolls and roll 2-3 times with Δr2 = (0.02-0.03)D; Shaping stage: Use profile rolling mills with bosses for final rolling, and control the flatness of the ring end face to be ≤0.05D.

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

6. A method for producing martensitic rings according to claim 1, characterized in that, When the diameter-to-length ratio L / D of the forging ring billet is greater than or equal to 3, an axial upsetting process is added before step (3): the billet is heated to β-150℃~β-100℃, and axial compression is performed using a flat anvil at a rate of 0.1-0.3mm / s, and the diameter-to-length ratio L' / D after upsetting is controlled to be 1.8-2.

5.

7. A method for producing martensitic rings according to claim 4, characterized in that, The correspondence between the boss height h of the conforming roller and the groove depth h2 of the ring is as follows: h = h2 + (0.5-1) mm, and the chamfer radius R' on both sides of the boss = R + (1-2) mm, where R is the radius of the groove arc.

8. A method for producing martensitic rings according to claim 4, characterized in that, The final rolling is performed using contour rolls with bosses, and is done in two stages: a. First rolling: The roll temperature is maintained at 900-950℃, and the feed rate Δr=0.03D, so that the groove depth is increased to h2=0.2D; b. Second rolling: The roll temperature is reduced 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 50-100μm, pore size 10-30nm) is pre-placed on the surface of a contour roll with bosses. During the rolling process, carbon atoms are driven to diffuse along the nanopores by the micro-area pressure difference (ΔP=5-10MPa) induced by deformation.

10. A method for producing a martensitic ring according to claim 9, characterized in that, Methods for preparing nanoporous carburized layers include: Plasma-sprayed substrate: A WC-12Co cermet layer with a thickness of 200-300 μm and a porosity of ≤3% is sprayed onto the working surface of the contour roll with bosses; Laser micro / nano structuring: A honeycomb-like nanopore array is fabricated on the coating surface using a femtosecond laser (wavelength 1030nm, pulse energy 0.5-1.5mJ). The pore size is 10-30nm, the pore depth is 50-100μm, and the pore density is [not specified]. pcs / cm²; Chemical activation treatment: Immerse the mold in an ethanol solution containing 0.5-1.2 mol / L ammonium nitrate and sonicate at 60°C for 30-60 min to form surface carboxylic acid groups.

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