A rolling mill material and its preparation method

Abstract

This invention belongs to the field of metallic materials and relates to a roll material and its preparation method. The preparation method provided by this invention includes the following steps: a) sequentially melting, casting, and forging the roll raw material to obtain a roll blank; the composition of the roll raw material includes: C 0.6-1%, Mn 1.5-3.5%, Cr 0.8-3%, Cu 0.1-0.4%, and Fe 93-96%; b) quenching the roll blank; c) tempering the quenched roll blank, then twisting both ends of the roll blank and holding it for a period of time, followed by cooling to obtain a deformed heat-treated roll blank; d) turning the deformed heat-treated roll blank to obtain a semi-finished roll product; e) performing surface nano-sizing treatment on the semi-finished roll product to obtain the roll material. The method provided by this invention can reduce the amount of alloy used in preparing the roll material and improve the overall performance of the roll material.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials and relates to a roll material and its preparation method. Background Technology

[0002] As a core component of the metal rolling process, the wear resistance, spalling resistance, and fatigue life of rolling rolls directly determine the stability of the rolling process, product quality, and production efficiency. Traditional cold rolling roll material design primarily follows a high-chromium (Cr) alloying approach. The design concept has gradually increased from the initial 2% Cr to 3%, 5%, 8%, and even 12% Cr. This high chromium content forms a large number of carbides in the matrix to improve wear resistance and hot hardness, meeting the manufacturing requirements of large-size, high-load rolls. For example, the Cr12MoV material commonly used in 20-roll mills achieves this through the synergistic effect of high carbon (1.4%–1.7%) and high chromium (11%–13%), resulting in the precipitation of a large number of carbides in the alloy. These include primary carbides, which are detrimental to overall performance, as well as fine, uniformly distributed carbides formed after the addition of microalloying elements such as Mo and V. These carbides not only improve wear resistance but also inhibit austenite grain growth. High-speed steel rolls are also based on the basic idea of ​​generating carbides through extensive alloying. They utilize the super-hard carbides precipitated in large quantities by elements such as tungsten (W), molybdenum (Mo), and vanadium (V) to strengthen the roll surface, significantly improving wear resistance and hot hardness at high temperatures.

[0003] However, as rolling processes continue to evolve towards higher loads and higher precision, traditional high-chromium or high-alloy designs have revealed the following major problems: ① Decreased toughness and increased fracture risk: While excessive carbides can significantly improve wear resistance, they also reduce the toughness of the material, forming brittle regions, thus increasing the risk of crack propagation or even fracture of the rolls under high loads and impact loads. ② Complex and difficult-to-control heat treatment process: In high-chromium or high-alloy materials, alloying elements such as chromium shrink the austenite region, increasing the quenching temperature. The heat treatment process has stringent requirements for parameters such as temperature, holding time, and cooling rate. If the process is not precisely controlled, it can easily lead to uneven microstructure, excessive residual austenite, excessive residual stress, or even hot cracks, thereby affecting the final mechanical properties and service life. ③ Difficulty in achieving comprehensive performance: While pursuing high wear resistance and hot hardness, traditional high-alloy rolls often sacrifice impact toughness and fatigue performance, making it difficult to meet the multiple requirements of modern rolling processes for high pressure, high wear resistance, and high fatigue resistance. ④ Huge cost and environmental pressures: High-chromium, high-tungsten and other alloying elements are scarce and expensive. Their high-energy-consuming smelting process not only leads to soaring costs, but also faces strict supervision and high treatment costs for the environmental treatment of Cr- and W-containing wastewater and other harmful substances, which further limits their large-scale application.

[0004] In order to reduce the manufacturing and use costs of rolls, while meeting the stringent requirements of high-load, high-precision rolling processes for wear resistance, spalling resistance and fatigue life, it is urgent to develop a new type of roll material and preparation method. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a roll material and a method for preparing the same, which can reduce the amount of alloy used in preparing the roll material and improve the overall performance of the roll material.

[0006] This invention provides a method for preparing a roll material, comprising the following steps:

[0007] a) The raw material for the rolls is successively smelted, cast, and forged to obtain the roll blank;

[0008] In step a), the composition of the roll raw material includes: C 0.6-1wt%, Mn 1.5-3.5wt%, Cr 0.8-3wt%, Cu 0.1-0.4wt%, Fe 93-96wt%;

[0009] b) The roll blank is quenched to obtain a quenched roll blank;

[0010] c) The quenched roll blank is tempered and held at a certain temperature for a period of time. The two ends of the roll blank are twisted and held for a period of time, and then cooled to obtain the deformed heat-treated roll blank.

[0011] d) The heat-treated roll blank is machined to obtain a semi-finished roll;

[0012] e) The semi-finished roll is subjected to surface nano-processing to obtain roll material.

[0013] Preferably, in step a), the composition of the roll raw material further includes one or more of Si, Mo, V, Ni and Nb.

[0014] Preferably, the Si content of the raw material for the roll is 0.5 to 1 wt%.

[0015] And / or, the V content of the roll material is 0.1 to 0.2 wt%;

[0016] And / or, the Ni content of the roll material is 0.3 to 0.8 wt%;

[0017] And / or, the Nb content of the roll material is 0.01 to 0.1 wt%.

[0018] Preferably, in step b), the quenching temperature is 850–1000°C.

[0019] Preferably, in step c), the tempering temperature is 450–550°C, and the tempering holding time is 30 minutes or more.

[0020] Preferably, in step c), the torsion angle at each end of the roll blank is 3° to 5°; and the torsion holding time is 10 to 15 seconds.

[0021] Preferably, in step d), the roughness of the semi-finished roll is ≤0.8μm and the radial runout is ≤0.05mm.

[0022] Preferably, in step e), the surface nano-treatment method includes at least one or more of the following: shot peening, surface mechanical grinding, surface mechanical rolling, surface mechanical pressing, dynamic plastic deformation, mechanical ball milling, equal channel corner extrusion, and high-energy beam heat treatment.

[0023] Preferably, in step e), the surface grain size of the roll material is <200nm.

[0024] This invention provides a roll material, which is prepared according to the preparation method described in the above technical solution.

[0025] Compared with the prior art, the present invention provides a roll material and its preparation method. The preparation method provided by the present invention includes the following steps: a) melting, casting and forging the roll raw material in sequence to obtain a roll blank; in step a), the composition of the roll raw material includes: C 0.6-1wt%, Mn 1.5-3.5wt%, Cr 0.8-3wt%, Cu 0.1-0.4wt%, Fe 93-96wt%; b) quenching the roll blank to obtain a quenched roll blank; c) tempering the quenched roll blank, holding it at a tempering temperature for a period of time, twisting both ends of the roll blank and holding it for a period of time, cooling it to obtain a deformed heat-treated roll blank; d) turning the deformed heat-treated roll blank to obtain a roll semi-finished product; e) performing surface nano-sizing treatment on the roll semi-finished product to obtain the roll material. The preparation method provided by this invention overcomes the limitations of traditional high-alloying processes. By optimizing the alloy composition, deformation heat treatment, and introducing surface nano-sizing technology, the hardness and wear resistance of the roll surface are improved while maintaining sufficient rigidity of the roll core. This provides better performance assurance and lower cost for the rolling process. More specifically, the preparation method provided by this invention has at least the following beneficial effects:

[0026] ① This invention changes the traditional development approach of rolling mill rolls, which involves adding high alloys to increase the wear resistance of the rolls. By adopting a low alloy composition design, combined with deformation heat treatment and surface nano-sizing, the overall performance of the rolling mill rolls is improved.

[0027] ② Reduce the production cost of existing high alloy rolls by reducing the Cr content (5-12%) of traditional Cr5-Cr8 rolls to 0.8-3%, and by combining the synergistic effect of Cu (0.1-0.4%), Mn (1.5-3.5%) and trace amounts of other alloying elements, to achieve a reduction of 18-25% in raw material costs.

[0028] ③ The introduction of Mn into the alloy raw materials will expand the austenite phase region, reduce the martensite transformation temperature, and form a considerable amount of retained austenite. These retained austenite can reduce the difficulty of nano-sizing the roll surface. After surface nano-sizing, the retained austenite on the surface will be transformed into nanoscale martensite or nanotwins, which will greatly improve the hardness and wear resistance of the roll surface.

[0029] ④ The introduction of Cu into the alloy raw materials will reduce the stacking fault energy of the alloy, reduce the difficulty of dislocation slip, reduce the difficulty of surface nano-sizing, and improve the surface nano-sizing effect.

[0030] ⑤ Deformation heat treatment can increase the dislocation density of the roll, strengthen the roll body, improve the basic hardness and rigidity of the roll, and promote subsequent surface nano-sizing.

[0031] ⑥ Surface nanoforming can introduce very high surface compressive stress (up to 1000 MPa), which can suppress the adverse effects of residual stress caused by deformation heat treatment, control the roll shape, and at the same time, surface compressive stress can effectively improve the fatigue resistance of the roll surface. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a method for preparing a roll material, comprising the following steps:

[0034] a) The raw material for the rolls is successively smelted, cast, and forged to obtain the roll blank;

[0035] In step a), the composition of the roll raw material includes: C 0.6-1wt%, Mn 1.5-3.5wt%, Cr 0.8-3wt%, Cu 0.1-0.4wt%, Fe 93-96wt%;

[0036] b) The roll blank is quenched to obtain a quenched roll blank;

[0037] c) The quenched roll blank is tempered and held at a certain temperature for a period of time. The two ends of the roll blank are twisted and held for a period of time, and then cooled to obtain the deformed heat-treated roll blank.

[0038] d) The heat-treated roll blank is machined to obtain a semi-finished roll;

[0039] e) The semi-finished roll is subjected to surface nano-processing to obtain roll material.

[0040] In the preparation method provided by this invention, in step a), the carbon (C) in the roll raw material is the basis for the formation of carbides. The roll needs to maintain basic hardness and rigidity; the carbon content cannot be too low, but too high a content will reduce toughness. A C content of 0.6–1 wt% can ensure that the roll has sufficient hardness and rigidity while maintaining appropriate toughness to prevent brittle fracture. If the C content is <0.6 wt%, the wear resistance is insufficient; if it is >1 wt%, the roll may be too brittle, and its impact resistance will decrease. In this invention, the C content in the roll raw material can specifically be 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, or 1 wt%.

[0041] In the preparation method provided by this invention, in step a), the main function of Mn in the roll raw material is to improve toughness, expand the austenite phase region, and improve hardenability. During the quenching process, Mn lowers the martensitic transformation temperature and increases retained austenite (RA), which helps reduce the difficulty of surface nano-sizing. Traditional roll production processes are very sensitive to retained austenite, and it is desirable to have as little retained austenite as possible. However, this invention requires a certain amount of retained austenite, which helps improve the toughness of the roll and reduces the difficulty of surface nano-sizing. At the same time, the surface hardness and wear resistance can also be guaranteed in subsequent production processes. In this invention, the Mn content in the roll raw material can specifically be 1.5wt%, 1.8wt%, 2wt%, 2.3wt%, 2.5wt%, 2.7wt%, 3wt%, 3.2wt%, or 3.5wt%.

[0042] In the preparation method provided by this invention, in step a), the main function of Cr in the roll raw material is to form Cr7C3 carbides, which improves wear resistance and hardness, enhances hardenability, and improves the uniformity of the steel's microstructure. Excessive Cr (>3%) will lead to an excessive number of carbides, making the matrix brittle and reducing impact resistance. In this invention, the Cr content in the roll raw material can specifically be 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.7wt%, 2wt%, 2.2wt%, 2.5wt%, 2.7wt%, or 3wt%.

[0043] In the preparation method provided by this invention, in step a), the main function of Cu in the roll raw material is to reduce stacking fault energy, improve dislocation slip capability, and facilitate surface nanostructuring. During tempering, Cu forms nano-precipitates, improving tempering strength and wear resistance. Excessive Cu content may lead to hot working cracks; it is more appropriate to control it within the range of 0.1–0.4 wt%. In this invention, the Cu content in the roll raw material can specifically be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, or 0.4 wt%.

[0044] In the preparation method provided by this invention, in step a), the composition of the roll raw material preferably includes one or more of Si, Mo, V, Ni, and Nb. Si can increase hardenability, while Mo, V, Ni, and Nb can form finer carbides, improve the hardness of the roll, and refine the austenite grains. In this invention, the Si content of the roll material is preferably 0.5–1 wt%, specifically 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%; the V content of the roll material is preferably 0.1–0.2 wt%, specifically 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.17 wt%, or 0.2 wt%; the Ni content of the roll material is preferably 0.3–0.8 wt%, specifically 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, or 0.8 wt%; and the Nb content of the roll material is preferably 0.01–0.1 wt%, specifically 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, or 0.1 wt%.

[0045] In the preparation method provided by the present invention, in step a), the Fe content in the roll raw material is preferably a balance.

[0046] In the preparation method provided by the present invention, in step a), the smelting can be carried out using conventional processes, including but not limited to converter steelmaking, ladle refining, etc.

[0047] In the preparation method provided by the present invention, in step a), the casting can be carried out using conventional processes, including but not limited to continuous casting, die casting, precision casting, etc.

[0048] In the preparation method provided by the present invention, in step a), the forging can be carried out using conventional processes, including but not limited to multi-directional forging, multi-stage forging, and multi-directional die forging.

[0049] In the preparation method provided by the present invention, in step b), the quenching temperature is preferably 850-1000℃, specifically 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃ or 1000℃; the cooling method of the quenching is preferably oil cooling, water cooling or air cooling.

[0050] In the preparation method provided by the present invention, in step c), the tempering temperature is preferably 450-550℃, specifically 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃ or 550℃; the tempering holding time is preferably 30 min or more, more preferably 30-60 min, specifically 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0051] In the preparation method provided by the present invention, in step c), the torsional loading rate of each end of the roll blank is preferably 0.1 to 1° / s, specifically 0.1° / s, 0.2° / s, 0.3° / s, 0.4° / s, 0.5° / s, 0.6° / s, 0.7° / s, 0.8° / s, 0.9° / s or 1° / s; the torsion angle of each end of the roll blank is preferably 3° to 5°, specifically 3°, 3.5°, 4°, 4.5° or 5°; the torsion holding time is preferably 10 to 15 s, specifically 10 s, 11 s, 12 s, 13 s, 14 s or 15 s.

[0052] In the preparation method provided by the present invention, in step c), the cooling method is preferably water cooling.

[0053] In the preparation method provided by the present invention, in step d), the turning process preferably includes rough turning and finish turning; the roughness of the roll semi-finished product obtained after turning is preferably ≤0.8μm, more preferably ≤0.6μm, even more preferably ≤0.4μm, and most preferably ≤0.2μm; the radial runout of the roll semi-finished product obtained after turning is preferably ≤0.05mm, more preferably ≤0.03mm, and even more preferably ≤0.02mm.

[0054] In the preparation method provided by the present invention, in step e), the surface nano-treatment includes one or more of the following: shot peening, surface mechanical grinding, surface mechanical rolling, surface mechanical pressing, dynamic plastic deformation, mechanical ball milling, equal channel corner extrusion, and high-energy beam heat treatment.

[0055] In the preparation method provided by the present invention, in step e), the surface grain size of the roll material obtained after the surface nano-treatment is preferably <200nm, specifically 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm or 180nm.

[0056] In the preparation method provided by the present invention, in step e), after the surface nano-sizing treatment is completed, the resulting roll material exhibits a gradient increase in grain size from the surface to the interior, namely, nanocrystals (<200nm), submicron crystals (200nm to <1μm), micron crystals (1 to 10μm), and coarse crystals (>10μm). The depth of the nanocrystalline layer is preferably 0.005–0.05 mm, specifically 0.005 mm, 0.01 mm, 0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm, or 0.05 mm; the depth of the submicron crystalline layer is preferably 0.1–1 mm, specifically 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.53 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm; the depth of the micron crystalline layer is preferably 0.1–1 mm, specifically 0.1 mm, 0.2 mm, 0.3 mm, 0.38 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.67 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm.

[0057] The present invention also provides a roll material, which is prepared according to the preparation method described in the above technical solution.

[0058] The technical solution provided by this invention breaks through the limitations of traditional high-alloying processes. By optimizing alloy composition, deformation heat treatment, and introducing surface nano-processing, it improves the hardness and wear resistance of the roll surface while maintaining sufficient rigidity of the roll core, thereby providing better performance assurance and lower cost for the rolling process. More specifically, the technical solution provided by this invention has at least the following beneficial effects:

[0059] ① This invention changes the traditional development approach of rolling mill rolls, which involves adding high alloys to increase the wear resistance of the rolls. By adopting a low alloy composition design, combined with deformation heat treatment and surface nano-sizing, the overall performance of the rolling mill rolls is improved.

[0060] ② Reduce the production cost of existing high alloy rolls by reducing the Cr content (5-12%) of traditional Cr5-Cr8 rolls to 0.8-3%, and by combining the synergistic effect of Cu (0.1-0.4%), Mn (1.5-3.5%) and trace amounts of other alloying elements, to achieve a reduction of 18-25% in raw material costs.

[0061] ③ The introduction of Mn into the alloy raw materials will expand the austenite phase region, reduce the martensite transformation temperature, and form a considerable amount of retained austenite. These retained austenite can reduce the difficulty of nano-sizing the roll surface. After surface nano-sizing, the retained austenite on the surface will be transformed into nanoscale martensite or nanotwins, which will greatly improve the hardness and wear resistance of the roll surface.

[0062] ④ The introduction of Cu into the alloy raw materials will reduce the stacking fault energy of the alloy, reduce the difficulty of dislocation slip, reduce the difficulty of surface nano-sizing, and improve the surface nano-sizing effect.

[0063] ⑤ Deformation heat treatment can increase the dislocation density of the roll, strengthen the roll body, improve the basic hardness and rigidity of the roll, and promote subsequent surface nano-sizing.

[0064] ⑥ Surface nanoforming can introduce very high surface compressive stress (up to 1000 MPa), which can suppress the adverse effects of residual stress caused by deformation heat treatment, control the roll shape, and at the same time, surface compressive stress can effectively improve the fatigue resistance of the roll surface.

[0065] For clarity, the following examples will be used to provide a detailed description.

[0066] Example 1

[0067] I. Composition Design (wt.%)

[0068] C 0.8%, Mn 2.5%, Cr 1.5%, Cu 0.3%, balance Fe.

[0069] II. Preparation Process

[0070] (1) Smelting and casting

[0071] Electric furnace smelting: The raw material ratio is scrap steel (60%), pig iron (30%), and alloy material (10%). The alloying elements are precisely proportioned according to the target composition. The smelting temperature is 1550-1600℃. The alloying elements are added in stages. Cr and Cu are added in the later stage of smelting to reduce burn-off.

[0072] Ladle refining: refining temperature 1580~1620℃, refining time ≥20 minutes, vacuum degree ≤67Pa (degassing treatment).

[0073] Continuous casting: superheat control 35℃±5℃, casting speed 1.2~1.5m / min, continuous casting billet diameter Φ300mm, surface quality requirements: no cracks or shrinkage cavities.

[0074] (2) Forging

[0075] Heating temperature 1150℃±10℃, heating time 8 hours, holding time 180 minutes; forging ratio 4:1, multi-directional forging (three upsetting and three drawing process), upsetting deformation amount 30% each time, final forging temperature ≥900℃; air cooling to room temperature after forging.

[0076] (3) Quenching treatment

[0077] Quenching temperature 920℃±10℃, heating rate 3~5℃ / min, holding time 200 minutes; cooling medium is rapid quenching oil, oil temperature 60~80℃, stirring speed 0.8m / s, cooling to room temperature.

[0078] (4) Deformation heat treatment

[0079] Tempering treatment: Tempering temperature 500℃±5℃, hold for 40 minutes.

[0080] Torsional loading: At the tempering temperature, a 4° torsion angle is simultaneously applied to both ends of the roll at a loading rate of 0.5° / s, held for 12 seconds, and then water-cooled (cooling rate ≥300℃ / s).

[0081] (5) Turning

[0082] Roughing parameters: single-sided allowance 5mm, feed rate 0.3mm / r, cutting speed 80m / min, surface roughness Ra 3.2μm.

[0083] Finishing parameters: feed rate 0.1 mm / r, cutting speed 120 m / min, radial runout ≤0.03 mm, surface roughness Ra 0.6 μm.

[0084] (6) Surface nano-sizing (shot peening)

[0085] Shot peening parameters: steel shot diameter 5mm (hardness 60-63HRC), shot peening pressure 0.4MPa, shot peening time 30 minutes.

[0086] Gradient structure: surface grain size 150nm, nanocrystalline layer depth 0.01mm, submicron crystal layer depth 0.3mm, micron crystal layer depth 0.5mm, total gradient layer depth 0.81mm.

[0087] Performance evaluation:

[0088] The total alloy content is 4.3%, which is 64% less than that of conventional high-chromium rolls (calculated at 12%); the grain size on the roll surface is 150nm, the surface hardness of the roll reaches 95-97HSD, and the surface compressive stress is 780MPa.

[0089] Example 2

[0090] I. Composition Design (wt.%)

[0091] C 0.6%, Mn 3.2%, Cr 0.8%, Cu 0.1%, V 0.15%, Nb 0.05%, balance Fe.

[0092] II. Preparation Process

[0093] (1) Smelting and casting

[0094] Vacuum induction melting: The raw material is pure scrap steel (S≤0.010%, P≤0.015%), the melting temperature is 1600~1650℃, the vacuum degree is ≤10Pa, and Mn, Cu, V and Nb alloys are added in the later stage of melting.

[0095] Ingot casting process: molten steel pouring temperature 1550℃, mold preheating temperature 600℃, billet diameter Φ250mm.

[0096] (2) Forging (two-stage forging)

[0097] First stage: rough forging at 1150℃ (deformation amount 50%), final forging temperature ≥1000℃;

[0098] Second stage: 900℃ precision forging (30% deformation), final forging temperature ≥800℃, forging ratio 3.5:1.

[0099] (3) Quenching treatment

[0100] Quenching temperature 950℃±10℃, heating rate 5℃ / min, holding time 1.5 minutes per millimeter of thickness (300 minutes for 200mm thickness); cooling process is water cooling, cooling rate ≥50℃ / s, hardness after quenching HRC 55±1.

[0101] (4) Deformation heat treatment

[0102] Tempering treatment: Tempering temperature 450℃±5℃, hold for 60 minutes, nitrogen protection in the furnace (oxygen content ≤0.3%).

[0103] Torsional loading: Torsional force is applied synchronously to both ends of the roll at the tempering temperature. The torsional force is applied in two stages. The first torsion loading rate is 0.3° / s, the torsion angle is 1.5°, and it is held for 5s. After a 5s interval, the second torsion is performed with a loading rate of 0.3° / s and a torsion angle of 1.5° (i.e., the total torsion angle is 3°). It is held for 10s and then water-cooled (cooling rate ≥15℃ / s).

[0104] (5) Turning

[0105] Roughing parameters: single-sided allowance 3mm, feed rate 0.4mm / r, cutting speed 60m / min, surface roughness Ra 6.3μm.

[0106] Finishing parameters: feed rate 0.08 mm / r, cutting speed 150 m / min, radial runout ≤0.02 mm, surface roughness Ra 0.4 μm.

[0107] (6) Surface nano-sizing (mechanical compaction)

[0108] Mechanical compaction parameters: rotation speed 300 r / min, pressure 10 kN, reciprocating compaction 10 times.

[0109] Gradient structure: surface grain size 100nm, nanocrystalline layer depth 0.03mm, submicron crystal layer depth 0.53mm, micron crystal layer depth 0.67mm, total gradient layer depth 1.23mm.

[0110] Performance evaluation:

[0111] The total alloy content is 4.3%, which is 64% less than that of conventional high-chromium rolls (calculated at 12%); the grain size on the roll surface is 100nm, the surface hardness of the roll reaches 100-102HSD, and the surface compressive stress is 980MPa.

[0112] Example 3

[0113] I. Composition Design (wt.%)

[0114] C 1.0%, Mn 1.8%, Cr 2.2%, Cu 0.4%, Ni 0.5%, Si 0.8%, balance Fe.

[0115] II. Preparation Process

[0116] (1) Smelting and casting

[0117] Converter + LF furnace refining: desulfurization rate ≥90% (final sulfur ≤0.008%); Ni and Cu alloying stage temperature 1600℃, wire feeding alloying.

[0118] Precision casting: Graphite mold material, preheating temperature 800℃, pouring temperature 1520℃, near-net-shape allowance ≤2mm.

[0119] (2) Forging (multi-directional die forging)

[0120] Die temperature 400℃, billet heating temperature 1100℃, deformation 70% (triaxial compression ratio 2:1:2); final forging temperature ≥850℃, post-forging spray cooling (cooling rate 20℃ / s) to eliminate casting shrinkage cavities, billet diameter Φ450mm.

[0121] (3) Quenching treatment (graded quenching)

[0122] Heating temperature 850℃±10℃, holding time 450 minutes; first stage water cooling to 300℃ (cooling rate ≥30℃ / s), second stage air cooling to room temperature.

[0123] (4) Deformation heat treatment

[0124] Tempering treatment: Tempering temperature 550℃±5℃, hold for 30 minutes.

[0125] Torsional loading: Apply a 5° torsion angle to both ends of the roll simultaneously at the tempering temperature, with a loading rate of 1° / s, hold for 15 seconds, and then water cool (cooling rate ≥25℃ / s).

[0126] (5) Turning

[0127] Roughing parameters: single-sided allowance 2mm, feed rate 0.2mm / r, cutting speed 100m / min, surface roughness Ra 3.2μm.

[0128] Finishing parameters: feed rate 0.05 mm / r, cutting speed 200 m / min, radial runout ≤0.02 mm, surface roughness ≤0.2 μm.

[0129] (6) Surface nano-sizing (laser shock peening + mechanical ball milling)

[0130] Laser shock parameters: wavelength 1064nm, energy density 10J / cm² 2 The pulse width is 20ns, the impact is repeated 3 times, and the surface pre-stress is ≥800MPa.

[0131] Mechanical ball milling parameters: zirconia ball milling media (Φ3mm), ball-to-material ratio 10:1, rotation speed 300rpm, ball milling time 4h, surface grain size 80nm.

[0132] Gradient layer depth: surface grain size 120nm, nanocrystalline layer 0.02mm, submicron crystalline layer 0.8mm, micron crystalline layer 0.38mm, total depth 1.2mm.

[0133] Performance evaluation:

[0134] The total alloy content is 5.7%, which is 52.5% less than that of conventional high-chromium rolls (calculated at 12%); the grain size on the roll surface is 120nm, the surface hardness of the roll reaches 102-104HSD, and the surface compressive stress is 1080MPa.

[0135] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a roll material, characterized in that, Includes the following steps: a) The raw material for the rolls is successively smelted, cast, and forged to obtain the roll blank; In step a), the raw material for the roll consists of the following components: C 0.6~1wt%, Mn 1.5~3.5wt%, Cr 0.8~3wt%, Cu 0.1~0.4wt%, with the balance being Fe; b) The roll blank is quenched to obtain a quenched roll blank; In step b), the quenching temperature is 850~1000℃; c) The quenched roll blank is tempered, and after tempering and holding for a period of time, the two ends of the roll blank are twisted and held for a period of time, and then cooled to obtain the deformed heat-treated roll blank. In step c), the tempering temperature is 450~550℃; the tempering holding time is more than 30 minutes; the torsion loading rate at each end of the roll blank is 0.1~1° / s; the torsion angle at each end of the roll blank is 3°~5°; and the torsion holding time is 10~15s. d) The heat-treated roll blank is machined to obtain a semi-finished roll; e) Perform surface nano-sizing treatment on the semi-finished roll to obtain the roll material; In step e), the surface grain size of the roll material is <200nm; the grain size of the roll material increases in a gradient from the surface to the interior, in the order of nanocrystals, submicron crystals, micron crystals, and coarse grains, wherein the depth of the nanocrystal layer is 0.005~0.05mm, the depth of the submicron crystal layer is 0.1~1mm, and the depth of the micron crystal layer is 0.1~1mm.

2. The preparation method according to claim 1, characterized in that, In step a), the composition of the roll raw material also includes one or more of Si, Mo, V, Ni and Nb.

3. The roll material according to claim 2, characterized in that, The Si content of the raw material for the rolls is 0.5~1wt%; And / or, the V content of the roll material is 0.1~0.2wt%; And / or, the Ni content of the roll material is 0.3~0.8 wt%; And / or, the Nb content of the roll material is 0.01~0.1wt%.

4. The preparation method according to claim 1, characterized in that, In step d), the roughness of the semi-finished roll is ≤0.8μm and the radial runout is ≤0.05mm.

5. The preparation method according to claim 1, characterized in that, In step e), the surface nano-treatment method includes one or more of the following: shot peening, surface mechanical grinding, surface mechanical rolling, surface mechanical rolling, dynamic plastic deformation, mechanical ball milling, equal channel corner extrusion, and high-energy beam heat treatment.

6. A roll material, characterized in that, The roll material is prepared according to the preparation method described in any one of claims 1 to 5.