High-wear-resistance nodular cast iron for roller, heat treatment process and roller

Abstract

The invention discloses high-wear-resistance nodular cast iron for a roller, a heat treatment process and the roller. The high-wear-resistance nodular cast iron for the roller comprises the following components in percentage by mass: 2.0-3.2% of C, 0.6-0.8% of Si, 0.4-0.8% of Mn, 1.2-2.0% of Cr, 0.8-1.0% of Ni, 0.1-0.3% of Mo and the balance of iron and inevitable impurities. The microstructure of the high-wear-resistance nodular cast iron for the roller comprises bainite, martensite and retained austenite. By designing and optimizing the heat treatment process, the matrix structure of the nodular cast iron is improved, and the obdurability, wear resistance and hot crack resistance of the matrix are improved, the roller made of the nodular cast iron can meet the rolling requirement of high-strength steel, the problems that the service life of the roller on a machine at a time is short, and peeling often occurs are solved, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of ductile iron and its heat treatment process, and more specifically, to a high wear-resistant ductile iron for rolling mill rolls, a heat treatment process, and rolling mill rolls, particularly to a ductile iron for long-life rolling mill rolls in round bar mills and its heat treatment process. Background Technology

[0002] In recent years, round bar production lines have mainly adopted short stress line rolling mills and developed continuous rolling and low-temperature rolling technologies. As the product specifications of wire rod production lines have become more diversified, the demand for small-sized products has continued to increase, and the mechanical properties have continued to improve, the mechanical properties of processing tools have also been continuously improved. Round bar production lines are required to achieve low-temperature furnace exit and low-temperature controlled rolling throughout the entire line, so as to improve the microstructure, yield strength and toughness of the products at the same time.

[0003] Currently, the rolls used for round bars are mainly made of traditional high-nickel-chromium pearlitic ductile iron. Recent usage shows that their wear resistance, anti-spading, and other accident resistance properties are poor, often resulting in wear-intolerant roll grooves, spalling, pitting, low single-groove rolling yield, and frequent roll changes, becoming a bottleneck for further increasing production capacity. As rolling mills move towards high-speed and high-quality development, the rolls made of this material have a short service life per run due to the above defects, affecting the production line efficiency. This necessitates a significant improvement in the thermal crack resistance and wear resistance of the working layer of the rolls in round bar rolling mills, while maintaining good strength and toughness in the matrix.

[0004] Based on existing technology retrieval and analysis, the following are the material and heat treatment processes, manufacturing processes, and surface strengthening technologies involved in the optimization and upgrading of ductile iron:

[0005] Chinese patent application CN200710115805.0 discloses a method for bainitrification treatment of ductile iron, including heating the ductile iron to the austenitic region, controlled cooling with water as the cooling medium, temperature equalization adjustment, isothermal treatment, and tempering. In the controlled cooling stage, the controlled cooling process parameters are determined based on the cooling parameter R. In the temperature equalization stage, the controlled temperature is adjusted so that the workpiece enters the isothermal treatment at a temperature closest to the isothermal treatment temperature, ensuring process stability. The obtained ductile iron, mainly composed of supercooled troostite, has properties close to bainitic ductile iron, with lower notch sensitivity and higher performance stability. In particular, the performance of small-sized parts of the workpiece treated by this method is higher than that of large-sized parts, providing assistance in solving some difficult-to-process workpieces. However, the performance of the ductile iron obtained by this technology is lower than that of bainitic ductile iron, and its notch sensitivity is high, resulting in insufficient accident resistance when used for high-speed wire rod rolls.

[0006] Chinese patent application CN00135192.3 discloses vanadium-containing bainitic ductile iron material and its production process. This technology belongs to the field of metallic materials technology. The technology provides a vanadium-containing bainitic ductile iron material with the following main chemical composition (%): C 2.5–3.8, Si 1.5–3.5, Mn 2.0–4.0, V 0.2–0.6. Its microstructure is bainite + graphite + a small amount of martensite + a small amount of retained austenite. Its performance characteristics are σb ≥ 350 MPa, HRC ≥ 45, and ak ≥ 8 J / cm³. 2 This material can be used to produce castings with high strength and wear resistance. Its advantage lies in the significant refinement of bainite, which improves mechanical and wear resistance properties. However, the microstructure of the ductile iron material in this technology is bainite, which cannot meet the requirements of wear resistance, i.e., long service life, for high-strength wire rod rolling.

[0007] Chinese patent application CN201410222612.5 discloses a method for casting grooved ductile iron rolls, comprising: Step 1, molding; Step 2, assembling the chilling ring and the cold mold; suspending the equally divided chilling rings on a platform and polishing the surface of the chilling rings to a metallic luster; then arranging the equally divided chilling rings into a circular shape, connecting adjacent equally divided chilling rings with bolts to form a circular integral chilling ring, adjusting the integral chilling ring so that its inner and outer circles are on the same center, tightening the connecting bolts, and installing the integral chilling ring into the cold mold; Step 3, baking the mold; Step 4, spraying the cold mold; Step 5, sealing the mold; Step 6, melting; Step 7, casting; Step 8, removing the positioning pins; after casting, cooling for 20-30 minutes, removing the positioning pins from the cold mold; Step 9, opening the mold to obtain the semi-finished product. The groove shape is cast directly at the original chiller ring, avoiding the impact of machining and grooving on the roll's wear resistance, while also reducing machining workload; the entire manufacturing process has low production costs, and the blank groove shape is smooth and flat. However, this technology is only an innovation in roll structure and manufacturing method, and does not involve improving roll performance.

[0008] Chinese patent application CN201720737279.0 discloses a heat-dissipating alloy ductile iron roll. This technology introduces cooling oil through a water inlet. The cooling oil enters and fills a receiving groove, then flows through a water outlet into the through-hole of the roller. The cooling oil eventually fills each receiving groove and each roller's through-hole. During use, the roller absorbs heat from the roll surface, effectively cooling it. The rollers in the receiving groove are tangent to the bottoms of both the first and second annular grooves. Through the roller support sleeve, the roll surface can withstand greater forces during use, effectively preventing surface deformation. This invention cools the roll while preventing deformation under significant external forces, improving its service life and steel rolling efficiency. However, this technology focuses on the roll's operation and cooling, and does not involve material selection or heat treatment processes. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a high-wear-resistant ductile iron for rolling mill rolls, along with a heat treatment process and the roll itself. By optimizing the heat treatment process, the microstructure of the ductile iron is improved, enhancing its strength, toughness, wear resistance, and resistance to hot cracking. This ductile iron roll can meet the rolling requirements of high-strength steel, solving problems such as short service life per machine run and frequent spalling, thereby improving production efficiency and reducing production costs.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The first aspect of the present invention provides a highly wear-resistant ductile iron comprising the following components by mass percentage: C: 2.0-3.2%, Si: 0.6-0.8%, Mn: 0.4-0.8%, Cr: 1.2-2.0%, Ni: 0.8-1.0%, Mo: 0.1-0.3%, with the balance being iron and unavoidable impurities;

[0012] The microstructure of the high wear-resistant ductile iron used for the rolls includes bainite, martensite, and retained austenite.

[0013] Preferably, the bainite accounts for 80-90% of the area in the ductile iron;

[0014] The martensite in the ductile iron accounts for 8-15% of the total area.

[0015] The area ratio of the retained austenite in the ductile iron is 2-5%.

[0016] Preferably, the high wear-resistant ductile iron for the rolls has a graphite content of 4-8 wt% and a carbide content of 12-18 wt%.

[0017] Preferably, the high wear-resistant ductile iron for the rolls has the following room temperature properties: hardness HSD 45-48, hardness drop ≤3HSD, tensile strength 500-600MPa, and room temperature impact toughness 4-5MPa.

[0018] Preferably, the high-wear-resistant ductile iron used for the rolls has the following high-temperature performance at 600℃: tensile strength of 450-530 MPa and hardness of HSD30-35.

[0019] A second aspect of the present invention provides a heat treatment process for high wear-resistant ductile iron for rolling mills as described in the first aspect of the present invention, comprising the following steps:

[0020] S1, annealing the ductile iron roll blank during the casting cooling process;

[0021] S2, the annealed ductile iron roll blank is then subjected to quenching and tempering treatment.

[0022] Preferably, in step S1, when the temperature of the ductile iron roll blank during the cooling process after casting is cooled to 850-960°C, it undergoes a furnace holding annealing treatment for 2-3 hours. After that, heating is stopped, and the roll blank is slowly cooled to 550°C before being removed from the furnace and air-cooled to room temperature.

[0023] Preferably, step S2 includes the following steps:

[0024] S21, the annealed ductile iron roll blank is heated at a heating rate of 100-130℃ / h, and held at 500±10℃ for 8-10 minutes to achieve uniform temperature.

[0025] S22, continue to heat up at a rate of 100-130℃ / h, and maintain the temperature at 800±10℃ for 8-10 minutes.

[0026] S23, continue heating to 900-980℃ and then quench, hold for 60-90 minutes, after taking it out of the furnace, perform oil quenching treatment, then blow air onto the roll body of the ductile iron roll blank until the roll body temperature is 130-150℃ and then stop blowing air, air cool until the roll body temperature is 95-100℃ and then temper within 2 hours.

[0027] S24. Preheat the tempering furnace to 90-110℃, heat at a heating rate of 180-200℃ / h, temper at 460-580℃, hold for 120-180min, cool with the furnace to ≤200℃, and air cool to room temperature; repeat this process 2-3 times.

[0028] Preferably, in step S23, the oil temperature used for the oil quenching treatment is 70-80°C, and the treatment time is 10-25 minutes.

[0029] Preferably, during the oil quenching treatment, the cooling rate of the ductile iron roll blank is 2.5 to 4.5 °C / s.

[0030] A third aspect of the present invention provides a roll whose body is made of high wear-resistant ductile iron as described in the first aspect of the present invention.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. The high wear-resistant ductile iron for rolls and the heat treatment process of the present invention can improve the matrix structure, carbide morphology and distribution of ductile iron to obtain round bar rolls with advantages such as resistance to hot cracking, high wear resistance, small turning amount and high single groove rolling amount.

[0033] 2. This invention optimizes the heat treatment process to develop bainitic + martensitic spheroidal cast iron without significantly increasing costs. This results in rolls with high matrix strength, small hardness difference, and improved accident resistance, wear resistance, and single-use service life of rolls in continuous rolling mills.

[0034] 3. Compared with traditional pearlitic rolls, the rolls made of spheroidal cast iron of the present invention have a 2-fold increase in steel throughput, no peeling or micro-cracks on the roll surface after finishing, and a 28-40% reduction in grinding requirements.

[0035] 4. This invention improves the heat treatment process, adjusts the microstructure of the continuous rolling mill rolls, and controls the content of graphite and carbides, thereby significantly enhancing the strength, toughness, oxidation resistance, and resistance to hot cracking of the matrix. This meets the rolling requirements of high-strength steels such as T91 and Cr13, solves problems such as short service life per roll and frequent spalling, improves production efficiency, and reduces production costs. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the microstructure of high wear-resistant ductile iron for rolling mills according to Embodiment 1 of the present invention. Detailed Implementation

[0037] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] In existing technology, the rolls of continuous rolling mills for section steel round bars are generally made of pearlitic ductile iron. During use, this results in issues such as deep groove cracks, large single-pass steel throughput, large machining allowances, and significant hardness variations. The rolls have a hardness of HSD 38-45, a hardness drop of ≤3HSD, a tensile strength ≥450MPa, and an impact toughness of 3-4.5MPa. The conventional heat treatment process for ductile iron is: softening annealing at 980-1000℃, quenching at 920-980℃, and tempering at 480-550℃.

[0039] This invention, based on the original ductile iron material, designs the most suitable heat treatment process to improve the original microstructure from pearlite to bainite, further enhancing the matrix's resistance to accidents and meeting the requirements for improved wear resistance, thermal crack resistance, and prevention of spalling. This invention develops a high-wear-resistant ductile iron for rolling mill rolls, along with a heat treatment process and the rolls themselves, suitable for continuous rolling of round bars. By designing and optimizing its heat treatment process, this invention develops a bainitic + martensitic high-wear-resistant ductile iron for rolling mill rolls without significantly increasing costs. This results in rolls with high matrix strength, a large hardness difference with small size, and improved accident resistance, wear resistance, and single-cycle service life of rolling mill rolls.

[0040] The high wear-resistant ductile iron for rolling mill rolls provided by the present invention comprises the following components by mass percentage: C: 2.0-3.2%, Si: 0.6-0.8%, Mn: 0.4-0.8%, Cr: 1.2-2.0%, Ni: 0.8-1.0%, Mo: 0.1-0.3%, with the balance being iron and unavoidable impurities;

[0041] The microstructure of high wear-resistant ductile iron for rolling mill rolls includes bainite, martensite, and retained austenite. In specific embodiments, bainite accounts for 80-90% of the area of ​​the ductile iron; martensite accounts for 8-15%; and retained austenite accounts for 2-5%.

[0042] The microstructure of high wear-resistant ductile iron for rolling mill rolls contains 4–8 wt% graphite and 12–18 wt% carbides, specifically MC-type, M6C-type, M7C3-type, and M... 23 The sum of C6 type carbides.

[0043] The room temperature properties of high wear-resistant ductile iron for rolling mill rolls are as follows: hardness HSD 45~48, hardness reduction ≤3HSD (i.e., hardness reduction ≤3HSD), tensile strength 500~600MPa, and room temperature impact toughness 4~5MPa.

[0044] The high-temperature performance of high wear-resistant ductile iron for rolling mill rolls at 600℃ is as follows: tensile strength is 450~530MPa, and hardness is HSD30~35.

[0045] The heat treatment process for the high wear-resistant ductile iron used in rolling mill rolls described above includes the following steps:

[0046] S1, annealing the ductile iron roll blank during the casting cooling process;

[0047] To save time, energy and other production costs, annealing is performed during the cooling process after casting. That is, when the temperature of the ductile iron roll blank cools to 850-960℃ during the cooling process after casting, it is subjected to furnace holding annealing for 2-3 hours. After that, heating is stopped, and it is slowly cooled to 550℃ in the furnace before being taken out of the furnace and air-cooled to room temperature.

[0048] This process eliminates residual stress generated during casting, ensuring sufficient decomposition of carbides and pearlite to form a spheroidized matrix, thus preparing for subsequent quenching and tempering. Furthermore, one of the most significant features of this invention is the annealing process during casting cooling, which greatly reduces time and energy costs.

[0049] S2 involves quenching and tempering the annealed ductile iron roll blank, including the isothermal holding stage, the quenching stage, and the tempering stage.

[0050] S21, the annealed ductile iron roll blank is heated at a heating rate of 100-130℃ / h, and held at 500±10℃ for 8-10 minutes to achieve uniform temperature.

[0051] S22, continue to heat up at a rate of 100-130℃ / h, and maintain the temperature at 800±10℃ for 8-10 minutes.

[0052] Multiple temperature equalization and holding processes are required during the quenching and tempering process. This is because when the heating rate is fast and the quenching temperature is high, short-term temperature equalization and holding can ensure that the roll is heated evenly. Therefore, in steps S1 and S2 of the technical solution of this invention, two temperature equalization and holding processes of 8 to 10 minutes are performed at 500±10℃ and 800±10℃.

[0053] S23, continue heating to 900-980℃ and then quench, hold for 60-90 minutes, after taking it out of the furnace, perform oil quenching treatment, then blow air onto the roll body of the ductile iron roll blank until the roll body temperature is 130-150℃ and then stop blowing air, air cool until the roll body temperature is 95-100℃ and then temper within 2 hours.

[0054] This process is the quenching stage. First, quench at 900-980℃ and hold for 60-90 minutes. Then, remove from the furnace and undergo oil quenching for 10-25 minutes. Through experimental research, the optimal oil temperature for quenching and cooling is designed to be 70-80℃, so that the cooling rate of the roller body is 2.5-4.5℃ / s. After oil quenching for 10-25 minutes, blow air onto the roller body. During the blowing stage, the highest temperature return is 280-300℃, until the roller temperature reaches 130-150℃. Stop blowing air and air cool until the roller body temperature stabilizes at 95-100℃, and then temper in time.

[0055] The quenching process uses cold oil to cool the austenite to slightly below the Ms point (Ms point is the starting temperature of the martensitic phase transformation in steel), and then isothermally cools it slightly above the Ms point. After isothermal treatment, it transforms into lower bainite. After a specified holding time, it is cooled to room temperature.

[0056] High-temperature quenching at 900–980℃ is performed because the alloy composition of ductile iron is optimized in this invention, resulting in an increase in high-melting-point carbides. MC is a V carbide with fine and uniformly distributed VC particles. M6C is a W and Mo carbide, which is quite stable and does not easily aggregate and grow, thus increasing the material's hardness and wear resistance. M7C3 is a Cr carbide, either a primary eutectic carbide or a secondary carbide precipitated from austenite. It can dissolve elements such as W, Mo, and V, increasing wear resistance and reducing the coefficient of friction. Secondary M7C3 dissolves into austenite at 950–1150℃; M… 23 C6 is another Cr carbide that begins to dissolve at 1000–1020°C, but requires 1150–1200°C to fully dissolve in austenite. Therefore, a higher quenching temperature of 900–980°C is necessary to ensure that the carbide is fully dissolved into the matrix.

[0057] S24. Preheat the tempering furnace to 90-110℃, heat at a heating rate of 180-200℃ / h, temper at 460-580℃, hold for 120-180min, cool with the furnace to ≤200℃, and air cool to room temperature; repeat this process 2-3 times.

[0058] This process is a high-temperature tempering process, with the tempering temperature controlled between 460 and 580℃ and the tempering holding time controlled within 120 to 180 minutes. This is because the microstructure and properties of ductile iron undergo significant changes during thermal fatigue; therefore, thermal cycling stability has a significant impact on thermal fatigue resistance. To obtain excellent thermal cycling stability, the heat treatment process must be designed to ensure that its microstructure and properties remain stable during thermal cycling. This mainly involves improving the tempering resistance of the rolls under cycling temperature conditions. Therefore, the high tempering resistance requirements and high quenching temperature both necessitate a high tempering temperature. Simultaneously, experiments show that MC-type carbides in this material precipitate during high-temperature tempering and cooling at temperatures above 500–600℃, exhibiting high dispersion, increasing hardness and wear resistance, and improving tempering stability. M7C3-type carbides only precipitate during high-temperature tempering, increasing the thermal stability of the matrix; M… 23 At tempering temperatures above 400–500℃, C6 can be transformed from Cr-saturated Fe3C or precipitated directly from the quenched steel matrix. It does not easily aggregate and grow, and its precipitation can slightly increase the tempering hardness. When the tempering temperature is above 580℃, the final hardness will be low; when the tempering temperature is below 460℃, the amount of precipitated carbides will be insufficient, resulting in insufficient roll strength. Therefore, it is necessary to ensure that the tempering temperature is between 460–580℃ and the tempering holding time is controlled within 2–3 hours to obtain a certain amount of lower bainite structure. This can essentially guarantee a significant improvement in the toughness of the matrix while maintaining the same hardness and strength, thereby improving thermal fatigue resistance and service life. Through experimental optimization, the bainite and martensite content in the obtained matrix reached the optimal value. Statistical measurements showed that at this point, the bainite area accounted for 80-90% of the ductile iron matrix area, the martensite area accounted for 8-15% of the ductile iron matrix area, and the retained austenite accounted for 2-5% of the ductile iron matrix area. At this point, the comprehensive mechanical properties of the roll were optimal. In the microstructure of ductile iron, the graphite area content was 4-8%, and the carbide content was 12-18%.

[0059] The high wear-resistant ductile iron for rolls obtained by the heat treatment process described above has a hardness of HSD45-48, a hardness drop of ≤3HSD, a roll body tensile strength of 500-600MPa, and a room temperature impact toughness of 4-5MPa.

[0060] The present invention also provides a roll whose roll body is made of the aforementioned high wear-resistant ductile iron for rolls. Compared with traditional pearlitic rolls, it increases the steel throughput by 2 times, and the roll surface after the machine is free from peeling and micro-cracks, and the amount of grinding is reduced by 28-40%.

[0061] Example

[0062] The embodiments employ the heat treatment process of the high wear-resistant ductile iron for rolling mill rolls of the present invention. The composition of the ductile iron and roll blank used in the embodiments is shown in Table 1, the parameters of the heat treatment process are shown in Table 2, and the room temperature and high temperature mechanical properties of the finally obtained high wear-resistant ductile iron for rolling mill rolls are shown in Table 3.

[0063] Table 1. Composition of ductile iron used in the examples.

[0064]

[0065] Table 2 Parameters of the heat treatment processes in Examples 1-5

[0066]

[0067] Table 3 shows the properties of high wear-resistant ductile iron for rolling mill rolls in Examples 1-5.

[0068]

[0069]

[0070] As shown in Tables 2 and 3, the high wear-resistant ductile iron for rolling mills prepared in Examples 1-5 of this invention has a room temperature hardness of HSD 45-48, a hardness drop of ≤3HSD, a roll body tensile strength of 500-600MPa, and a room temperature impact toughness of 4-5MPa. At a high temperature of 600℃, the tensile strength is 450-528MPa, and the hardness HSD is 30-35.

[0071] Combination Figure 1 The microstructure of the high wear-resistant ductile iron for rolling mills prepared in Example 1 is as follows: bainite accounts for 82% of the matrix area, martensite accounts for 11% of the matrix area, and the retained austenite content is 3%. In the microstructure of the high wear-resistant ductile iron for rolling mills, the graphite content is 5 wt% and the carbide content is 14 wt%.

[0072] The wear resistance of the high wear-resistant ductile iron of the present invention is reflected in two aspects: the average rolling tonnage per roll run and the amount of grinding. The data are shown in Table 4. The average rolling tonnage per roll run of the roll prepared in Example 1 of the present invention is 5000t, which is 2 times higher than the average rolling tonnage of 2500t per roll run of the original process ductile iron roll. The grinding amount of the present invention is 6mm, which is 3mm less than the grinding amount of 9mm of the original process ductile iron roll, a reduction of 33%.

[0073] Table 4. Comparison of the average rolling yield per run of the rolls of this invention and the original process ductile iron rolls.

[0074]

[0075] In summary, this invention, through heat treatment process design, employs a high-quenching and high-resilience heat treatment process, rapid cooling, and bainitrification, combined with high-temperature tempering and the incorporation of a lower bainite transformation process. By comprehensively considering the reasonable combination of hardness, strength, and toughness of the rolls, it aims to improve the rolls' resistance to thermal cracking and extend their service life. The heat treatment process of this invention can be extended to fields such as wire rod, seamless steel pipe, and precision steel pipe, and can meet the service requirements under high-temperature conditions of 600–650℃.

[0076] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A high wear-resistant ductile iron for rolling mill rolls, characterized in that, It includes the following components by mass percentage: C: 2.0–3.2%, Si: 0.6–0.8%, Mn: 0.4–0.8%, Cr: 1.2–2.0%, Ni: 0.8–1.0%, Mo: 0.1–0.3%, with the balance being iron and unavoidable impurities; The microstructure of the high wear-resistant ductile iron used for the rolls includes bainite, martensite, and retained austenite.

2. The high wear-resistant ductile iron for rolling mill rolls according to claim 1, characterized in that, The bainite accounts for 80-90% of the area in ductile iron; The martensite in the ductile iron accounts for 8-15% of the total area. The area ratio of the retained austenite in the ductile iron is 2-5%.

3. The high wear-resistant ductile iron for rolling mill rolls according to claim 1, characterized in that, The microstructure of the high wear-resistant ductile iron for the rolls contains 4-8 wt% graphite and 12-18 wt% carbide.

4. The high wear-resistant ductile iron for rolling mill rolls according to claim 1, characterized in that, The high wear-resistant ductile iron for the rolls has the following room temperature properties: hardness HSD 45~48, hardness drop ≤3HSD, tensile strength 500~600MPa, and room temperature impact toughness 4~5MPa.

5. The high wear-resistant ductile iron for rolling mill rolls according to claim 1, characterized in that, The high-wear-resistant ductile iron used for the rolls has the following high-temperature performance at 600℃: tensile strength of 450-530 MPa and hardness of HSD30-35.

6. A heat treatment process for high wear-resistant ductile iron for rolling mills as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1, annealing the ductile iron roll blank during the casting cooling process; S2, the annealed ductile iron roll blank is then subjected to quenching and tempering treatment.

7. The heat treatment process for high wear-resistant ductile iron for rolling mill rolls according to claim 6, characterized in that, In step S1, when the temperature of the ductile iron roll blank during the cooling process after casting is cooled to 850-960°C, it undergoes a furnace holding annealing treatment for 2-3 hours. After that, heating is stopped, and the roll blank is slowly cooled to 550°C before being removed from the furnace and air-cooled to room temperature.

8. The heat treatment process for high wear-resistant ductile iron for rolling mill rolls according to claim 6, characterized in that, Step S2 includes the following steps: S21, the annealed ductile iron roll blank is heated at a heating rate of 100-130℃ / h, and held at 500±10℃ for 8-10 minutes to achieve uniform temperature. S22, continue to heat up at a rate of 100-130℃ / h, and maintain the temperature at 800±10℃ for 8-10 minutes. S23, continue heating to 900-980℃ and then quench, hold for 60-90 minutes, after taking it out of the furnace, perform oil quenching treatment, then blow air onto the roll body of the ductile iron roll blank until the roll body temperature is 130-150℃ and then stop blowing air, air cool until the roll body temperature is 95-100℃ and then temper within 2 hours. S24. Preheat the tempering furnace to 90-110℃, heat at a heating rate of 180-200℃ / h, temper at 460-580℃, hold for 120-180min, cool with the furnace to ≤200℃, and air cool to room temperature; repeat this process 2-3 times.

9. The heat treatment process for high wear-resistant ductile iron for rolling mill rolls according to claim 8, characterized in that, In step S23, the oil temperature used for the oil quenching treatment is 70-80℃, and the treatment time is 10-25 minutes.

10. The heat treatment process for high wear-resistant ductile iron for rolling mill rolls according to claim 8, characterized in that, During the oil quenching treatment, the cooling rate of the ductile iron roll blank is 2.5 to 4.5 °C / s.

11. A rolling mill roll, characterized in that, The roll body is made of high wear-resistant ductile iron for rolls as described in any one of claims 1 to 5.

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