A circular semi-steel vertical roller and its preparation method

Abstract

This invention discloses a disc-shaped semi-steel vertical roller and its preparation method, belonging to the field of semi-steel roller technology, and solves the problems of difficult-to-achieve hardness and uneven hardness in existing disc-shaped semi-steel vertical rollers. The preparation method of the disc-shaped semi-steel vertical roller includes: holding at the blue brittleness temperature range; holding at 650-700℃ for 5-10 hours; holding at 850-900℃ for 6-15 hours; removing the disc-shaped semi-steel vertical roller forging and air-cooling for 10-15 minutes; then immersing the entire disc-shaped semi-steel vertical roller forging in an oil bath for circulating oil cooling until the surface temperature of the disc-shaped semi-steel vertical roller forging reaches 200±10℃, and then immediately removing it from the oil; holding at the bainitic transformation temperature; holding at 500-600℃; cooling to 400±10℃; cooling to below 120℃; then removing it from the furnace and air-cooling to obtain the disc-shaped semi-steel vertical roller; the disc-shaped semi-steel vertical roller prepared by the method of this invention has high hardness and good hardness uniformity.

Description

Technical Field

[0001] This invention relates to the field of semi-steel roller technology, and in particular to a disc-shaped semi-steel vertical roller and its preparation method. Background Technology

[0002] Roll products are mostly shaft-type components (see...) Figure 1 In conjunction with the product characteristics, a rotatable idler roller device is provided, which allows the workpiece to rotate and cool during performance heat treatment, ensuring uniform cooling across the entire workpiece surface. The semi-steel vertical roller with a disc-shaped shape (see...) Figure 2 and Figure 3 The inability to achieve uniform rotating spray cooling results in: (1) uneven hardness on the outer circumference of the working layer due to uneven cooling; (2) poor cooling effect in the "cavities" on the upper and lower surfaces, resulting in substandard hardness.

[0003] Therefore, how to provide a circular semi-steel vertical roller with satisfactory hardness, uniform hardness, and excellent performance, and its preparation method, has become an urgent problem to be solved. Summary of the Invention

[0004] In view of the above, the present invention aims to provide a disc-shaped semi-steel vertical roller and its preparation method, so as to solve the problems of the existing disc-shaped semi-steel vertical roller having difficulty in achieving the required hardness and uneven hardness.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] On one hand, the present invention provides a method for preparing a disc-shaped semi-steel vertical roller, the method comprising the following steps:

[0007] Step 1: Place the round, semi-steel vertical roll forging in the furnace and hold it at the blue brittleness temperature range;

[0008] Step 2: Increase the temperature to 650-700℃ at the first heating rate;

[0009] Step 3: Keep warm at 650-700℃ for 5-10 hours;

[0010] Step 4: Increase the temperature to 850-900℃ at a second heating rate; the second heating rate is greater than the first heating rate.

[0011] Step 5: Keep warm at 850-900℃ for 6-15 hours;

[0012] Step 6: Lift out the disc-shaped semi-steel vertical roller forging and air cool for 10-15 minutes. Then immerse the entire disc-shaped semi-steel vertical roller forging in an oil tank and circulate oil to cool it until the surface temperature of the disc-shaped semi-steel vertical roller forging reaches 200±10℃. Then, remove the oil immediately.

[0013] Step 7: After the oil has dried, immediately place the sample in the tempering furnace and hold it at the bainitic transformation temperature.

[0014] Step 8: Heat to 500-600℃ at a third heating rate and hold at that temperature; the third heating rate should be lower than the second heating rate.

[0015] Step 9: Cool down to 400±10℃ at the first cooling rate;

[0016] Step 10: Cool down to below 120°C at the second cooling rate, then remove from the furnace and air cool to obtain a round, disc-shaped semi-steel vertical roller; the second cooling rate is less than the first cooling rate.

[0017] Furthermore, the outer contour of the disc-shaped semi-steel vertical roller is cylindrical, with a height-to-diameter ratio of ≤0.5, and the upper and lower circular surfaces are symmetrically opened with annular grooves.

[0018] Furthermore, the composition of the disc-shaped semi-steel vertical roller, by mass percentage, includes: C 1.5%–2.1%, Si 0.4%–0.7%, Mn 0.4%–0.7%, Cr 0.8%–1.5%, Mo 0.1%–0.4%, Ni 0.4%–1.0%, with the balance being Fe and unavoidable trace impurities.

[0019] Furthermore, in step 1, the blue brittleness temperature range is 250–300°C.

[0020] Furthermore, in step 2, the first heating rate is 18–21 °C / h.

[0021] Furthermore, in step 4, the second heating rate is controlled to be 38–41 °C / h.

[0022] Furthermore, in step 6, the disc-shaped semi-steel vertical roll forging should be placed upright on the material tray during heating and cooling.

[0023] Furthermore, in step 9, the first cooling rate is no more than 20℃ / h.

[0024] On the other hand, the present invention provides a disc-shaped semi-steel vertical roller, which is prepared by the above-described preparation method.

[0025] Furthermore, the surface microstructure of the disc-shaped semi-steel vertical roller within 100 mm consists of fine lamellar troostite and granular carbides.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] a) In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, the disc-shaped semi-steel vertical roller is first air-cooled for an appropriate time before oil cooling to appropriately reduce the surface quenching temperature of the disc-shaped semi-steel vertical roller forging to reduce the risk of surface cracking; after air cooling, the entire disc-shaped semi-steel vertical roller forging is immersed in an oil bath for circulating oil cooling, and by precisely controlling the circulation time of oil cooling, the entire workpiece surface is in contact with the coolant to obtain a uniform phase transformation structure, ensuring the uniformity of hardness, and also reducing the risk of oil bath combustion and forging cracking.

[0028] (b) In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, the disc-shaped semi-steel vertical roller forging is placed upright on the material tray during oil cooling, which ensures the circulation effect of oil cooling, reduces the risk of fire when oil is discharged, and has good process safety.

[0029] c) In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, multi-stage heating is adopted and the heating rate of each stage is precisely controlled, which reduces the internal and external temperature difference and instantaneous internal stress in the semi-steel vertical roller, greatly reduces the risk of cracking, and provides a suitable basis for oil cooling.

[0030] d) In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, in the tempering process after oil cooling, different cooling rates are controlled in different temperature ranges to avoid cracking and reduce instantaneous stress, thereby improving product yield.

[0031] e) The microstructure of the disc-shaped semi-steel vertical roller of the present invention within 100 mm of its surface consists of fine lamellar troostite and granular carbides. The granular carbides are small in size, ≤5 μm, and mainly 1-2 μm in size. The disc-shaped semi-steel vertical roller of the present invention has fine and uniform grains, for example, grain size of 6-9. The comprehensive mechanical properties of the disc-shaped semi-steel vertical roller of the present invention are greatly improved, with high hardness and good hardness uniformity, which improves the thermal crack resistance of the material. The granular carbides dispersed on the matrix have a positive effect on improving the wear resistance in the working layer.

[0032] f) The outer surface of the disc-shaped semi-steel vertical roller of the present invention has a hardness of 47-50 HSD, the hardness difference between different parts of the outer circumference is ≤3 HSD, the tensile strength of the outer surface of the disc-shaped semi-steel vertical roller is 1280 MPa or more (e.g., 1283-1356 MPa), the yield strength is 860 MPa or more (e.g., 866-909 MPa), the impact energy AKU is 9 J or more (e.g., 9-10 J), and the elongation is 5% or more. The core of the disc-shaped semi-steel vertical roller has a hardness of 43-46 HSD, the tensile strength of the core is 850 MPa or more (e.g., 854-871 MPa), the yield strength is 480 MPa or more (e.g., 480-507 MPa), the impact energy AKU is 8 J or more (e.g., 8-10 J), and the elongation is 5% or more (e.g., 5%-6%).

[0033] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0034] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0035] Figure 1 This is a cross-sectional schematic diagram of a shaft-type component;

[0036] Figure 2 A schematic diagram of the overall structure of a semi-steel vertical roller with a circular disc shape;

[0037] Figure 3 A schematic diagram of the cross-section of a semi-steel vertical roller with a disc-like shape;

[0038] Figure 4 One of the microstructure images of the semi-steel vertical roller with a disc-shaped shape in Example 1;

[0039] Figure 5 One of the microstructure images of the semi-steel vertical roller with a disc-shaped shape in Example 1;

[0040] Figure 6 The grain size diagram of the semi-steel vertical roller with the disc-shaped shape of Example 1;

[0041] Figure 7 Microstructure diagram of the semi-steel vertical roller with a disc-shaped shape in Example 2;

[0042] Figure 8 The grain size diagram shows the semi-steel vertical roller with a disc-shaped shape as shown in Example 2. Detailed Implementation

[0043] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0044] A schematic diagram of the overall structure of the disc-shaped semi-steel vertical roller is shown below. Figure 2 As shown, the outer contour of the disc-shaped semi-steel vertical roller is cylindrical, with a height-to-diameter ratio ≤ 0.5. Several irregularly shaped annular grooves (also called "cavities") are symmetrically opened on the upper and lower circular surfaces. A cross-sectional diagram of the disc-shaped semi-steel vertical roller is shown below. Figure 3As shown. The above-mentioned disc-shaped semi-steel vertical roller cannot achieve uniform rotating spray cooling, resulting in: (1) the hardness of the outer circumference of the working layer is seriously uneven due to uneven cooling; (2) the cooling effect in the "cavities" on the upper and lower surfaces is poor, and the hardness does not meet the standard; therefore, the present invention provides a method for preparing a disc-shaped semi-steel vertical roller to solve the problems of the existing disc-shaped semi-steel vertical roller having difficulty in meeting the hardness standard and uneven hardness.

[0045] The components of the disc-shaped semi-steel vertical roller of the present invention, by mass percentage, include: C 1.5% to 2.1%, Si 0.4% to 0.7%, Mn 0.4% to 0.7%, Cr 0.8% to 1.5%, Mo 0.1% to 0.4%, Ni 0.4% to 1.0%, with the balance being Fe and unavoidable trace impurities.

[0046] This invention provides a method for preparing a circular semi-steel vertical roller, comprising the following steps:

[0047] Step 1: Place the round, semi-steel vertical roll forging in the furnace and hold it at the blue brittleness temperature range;

[0048] Step 2: Increase the temperature to 650-700℃ at the first heating rate;

[0049] Step 3: Keep warm at 650-700℃ for 5-10 hours;

[0050] Step 4: Increase the temperature to 850-900℃ at a second heating rate; the second heating rate is greater than the first heating rate.

[0051] Step 5: Keep warm at 850-900℃ for 6-15 hours;

[0052] Step 6: Lift out the disc-shaped semi-steel vertical roller forging and air cool for 10-15 minutes. Then immerse the entire disc-shaped semi-steel vertical roller forging in an oil tank and circulate oil to cool it until the surface temperature of the disc-shaped semi-steel vertical roller forging reaches 200±10℃. Then, remove the oil immediately.

[0053] Step 7: After the oil has dried, immediately place the sample in the tempering furnace and hold it at the bainitic transformation temperature.

[0054] Step 8: Heat to 500-600℃ at a third heating rate and hold at that temperature; the third heating rate should be lower than the second heating rate.

[0055] Step 9: Cool down to 400±10℃ at the first cooling rate;

[0056] Step 10: Cool the product to below 120°C at a second cooling rate, then remove it from the furnace and air-cool it to obtain a round, disc-shaped semi-steel vertical roller. The second cooling rate is less than the first cooling rate.

[0057] Specifically, before step 1 above, the surface quality of the disc-shaped semi-steel vertical roll forging needs to be carefully checked to ensure that there are no defects such as sharp corners or cracks.

[0058] Specifically, the main purpose of step 1 above is to reduce the internal and external temperature difference of the disc-shaped semi-steel vertical roll forging. 250–300℃ is the blue brittleness temperature range for this steel grade, where internal stress poses a significant risk of cracking. Therefore, this temperature range is chosen for heat preservation. Excessive heat preservation time leads to unnecessary energy waste; insufficient heat preservation time results in a large internal stress due to the large internal and external temperature difference, causing danger. Therefore, heat preservation at 250–300℃ for 5–10 hours is maintained to ensure the internal and external temperature difference of the workpiece is ≤50℃.

[0059] Specifically, in step 2 above, considering that the semi-steel vertical roller of the present invention has poor plasticity and toughness and is under tension in the core during the heating process, the heating speed is limited in this step to minimize the internal and external temperature difference and instantaneous internal stress in the semi-steel vertical roller. Excessive temperature difference can easily cause excessive thermal stress and lead to cracking of the forging. Therefore, the first heating rate is controlled at 18 to 21°C / h, for example 19°C / h or 20°C / h.

[0060] Specifically, in step 3 above, in order to minimize the temperature difference between the inside and outside of the forging during the heating transformation and the non-simultaneity of the transformation, and to further reduce the stress and deformation in the workpiece, the temperature is controlled at 650-700℃ for 5-10 hours, so that the temperature difference between the inside and outside of the workpiece is ≤50℃.

[0061] Specifically, in step 4 above, considering that the internal and external temperatures of the workpiece reach above 600℃ before heating, and the material is in a state of good plasticity, the heating rate should be increased as soon as possible to achieve the effect of refining the grains. Considering the capacity of the heating furnace equipment, the second heating rate is controlled to be 38-41℃ / h, for example, 39℃ / h or 40℃ / h.

[0062] Specifically, step 5 above aims to re-austenite the austenite. Considering that excessively high holding temperatures or long holding times promote grain coarsening, while excessively low holding temperatures or short holding times hinder recrystallization, resulting in insufficient refinement of the original coarse austenite grains, the holding temperature is controlled at 850–900℃. The holding time can be calculated based on the effective cross-sectional dimension (mm), i.e., 2–3.5 h / 100 mm. For example, the holding time is 6–15 h.

[0063] Specifically, in step 6 above, the air-cooling step of removing the workpiece is crucial. This step aims to appropriately lower the surface quenching temperature of the disc-shaped semi-steel vertical roll forging, thereby reducing the risk of surface cracks. Considering that excessively long air-cooling times and relatively slow cooling rates can easily promote the transformation of coarse lamellar pearlite structures, while excessively short air-cooling times can lead to increased quenching cracks due to excessively high quenching temperatures, the air-cooling time should be controlled to 10–15 minutes.

[0064] Specifically, in step 6 above, considering that too short an oil cooling time can easily lead to oil tank combustion, and too long an oil cooling time can lead to a greater risk of cracking in the disc-shaped semi-steel vertical roll forging, after in-depth research, this invention controls the circulating oil cooling time according to the effective cross-section of the workpiece, with an oil cooling time of 16-18 min / 100 mm, ensuring that the surface temperature of the disc-shaped semi-steel vertical roll forging reaches about 200°C, at which point oil can be discharged immediately, which not only avoids oil tank combustion but also reduces the risk of forging cracking.

[0065] Specifically, in step 6 above, considering the presence of "cavities" in the disc-shaped semi-steel vertical roll forging, if it is laid flat and immersed in oil, it will lead to: ① weakening the circulation of cooling oil, and ② the retention of cooling oil in the "cavities," which can easily cause fires when the oil is discharged. Therefore, the disc-shaped semi-steel vertical roll forging should be placed upright on a tray (e.g., ...) during heating and cooling. Figure 2 As shown, the pads should be compacted to prevent tipping.

[0066] Specifically, in step 6 above, when immersing the disc-shaped semi-steel vertical roller forging into the oil tank, the disc-shaped semi-steel vertical roller forging should be made to sink in the oil tank as much as possible to avoid damage to the oil tank equipment due to the risk of quenching cracks.

[0067] Specifically, in step 7 above, the oil should be drained and the product should be immediately placed in the tempering furnace to avoid cracking due to excessive stress.

[0068] Specifically, in step 7 above, in order to fully transform the austenite in the core of the forging and reduce the temperature difference between the inside and outside of the workpiece, the disc-shaped semi-steel vertical roll forging is held at 350-450℃ for 10-20 hours. 350-450℃ is the bainite transformation temperature range of this material. Holding it at 350-450℃ for 10-20 hours can allow the retained austenite to complete the transformation of the structure as much as possible.

[0069] Specifically, in step 8 above, considering that an excessively high heating rate can easily lead to a large temperature difference between the inside and outside of the workpiece, resulting in excessive thermal stress and the risk of internal cracking, the third heating rate is controlled to be no greater than 30℃ / h, for example, 29℃ / h, 27℃ / h, 25℃ / h, or 20℃ / h.

[0070] Specifically, step 8 above aims to further reduce the stress in the forging. Considering that the holding temperature is the most important factor affecting the workpiece's hardness, excessively high temperatures result in workpiece hardness below the technical requirements, while low temperatures lead to excessively high hardness. Excessive holding time not only wastes resources but may also reduce workpiece hardness; conversely, insufficient holding time fails to effectively eliminate residual stress. Therefore, the holding temperature is controlled at 500–600℃, and the holding time can be calculated based on the effective cross-sectional dimension (mm), i.e., 3.5–5 h / 100 mm. For example, holding time of 10–40 h.

[0071] Specifically, in step 9 above, in order to reduce the residual stress of the forging during the cooling process, the temperature is controlled to be lowered to 400°C at a first cooling rate not exceeding 20°C / h. For example, the first cooling rate is 12–19°C / h.

[0072] Specifically, in step 10 above, since the disc-shaped semi-steel vertical roll forging has entered a range of high cold hardness and brittleness below 400℃, a slower cooling rate is adopted to avoid cracking and reduce instantaneous stress. For example, the second cooling rate is 5-10℃ / h.

[0073] This invention provides a disc-shaped semi-steel vertical roller, prepared using the above-described method. The microstructure of the disc-shaped semi-steel vertical roller within 100 mm of its surface consists of fine lamellar troostite and granular carbides. The granular carbides are small, with a size ≤5 μm, and predominantly 1–2 μm. The disc-shaped semi-steel vertical roller of this invention exhibits fine and uniform grains, for example, a grain size of 6–9. This significantly improves the overall mechanical properties of the disc-shaped semi-steel vertical roller, enhancing the material's resistance to thermal cracking. The dispersed granular carbides on the matrix also play a positive role in improving the wear resistance within the working layer.

[0074] Specifically, the outer surface hardness of the disc-shaped semi-steel vertical roller of the present invention is 47-50 HSD, the hardness difference between different parts of the outer circumference is ≤3 HSD, the tensile strength of the outer surface of the disc-shaped semi-steel vertical roller is 1280 MPa or more (e.g., 1283-1356 MPa), the yield strength is 860 MPa or more (e.g., 866-909 MPa), the impact energy AKU is 9 J or more (e.g., 9-10 J), and the elongation is 5% or more. The core of the disc-shaped semi-steel vertical roller has a hardness of 43-46 HSD, the tensile strength of the core is 850 MPa or more (e.g., 854-871 MPa), the yield strength is 480 MPa or more (e.g., 480-507 MPa), the impact energy AKU is 8 J or more (e.g., 8-10 J), and the elongation is 5% or more (e.g., 5%-6%).

[0075] Specifically, the working layer of the disc-shaped semi-steel vertical roller of the present invention has a tensile strength of up to 1200MPa and an impact energy of ≥9J, which far exceeds the technical requirements of semi-steel vertical rollers (tensile strength >750MPa, impact energy ≥4J), greatly increasing the vertical roller's resistance to thermal cracking and impact.

[0076] Compared with the prior art, in the preparation method of the disc-shaped semi-steel vertical roller of the present invention, the disc-shaped semi-steel vertical roller is first air-cooled for an appropriate time before oil cooling to appropriately reduce the surface quenching temperature of the disc-shaped semi-steel vertical roller forging, so as to reduce the risk of surface cracking. After air cooling, the entire disc-shaped semi-steel vertical roller forging is immersed in an oil bath for circulating oil cooling. By precisely controlling the circulation time of oil cooling, the entire surface of the workpiece is in contact with the coolant, resulting in a uniform phase transformation structure, ensuring uniform hardness, and reducing the risk of oil bath combustion and forging cracking.

[0077] Compared with the prior art, in the preparation method of the disc-shaped semi-steel vertical roller of the present invention, the disc-shaped semi-steel vertical roller forging is placed upright on the material tray during oil cooling, which ensures the circulation effect of oil cooling, reduces the risk of fire when oil is discharged, and has good process safety.

[0078] In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, multi-stage heating is adopted and the heating rate of each stage is precisely controlled, which reduces the internal and external temperature difference and instantaneous internal stress in the semi-steel vertical roller, greatly reduces the risk of cracking, and provides a suitable basis for oil cooling.

[0079] In the preparation method of the disc-shaped semi-steel vertical roller of the present invention, in the tempering process after oil cooling, different cooling rates are controlled in different temperature ranges to avoid cracking and reduce instantaneous stress, thereby improving product yield.

[0080] The following specific embodiments and comparative examples demonstrate the advantages of precise control of the steps and process parameters in the preparation method of the disc-shaped semi-steel vertical roller of the present invention.

[0081] Example 1

[0082] This embodiment provides a disc-shaped semi-steel vertical roller, and the overall structural schematic diagram of the disc-shaped semi-steel vertical roller is shown below. Figure 2 As shown, the outer contour of the disc-shaped semi-steel vertical roller is cylindrical, with a height-to-diameter ratio of 0.45. Several irregularly shaped annular grooves ("cavities") are symmetrically opened on the upper and lower circular surfaces. A cross-sectional schematic diagram of the disc-shaped semi-steel vertical roller is shown below. Figure 3 As shown, the effective cross-section of the disc-shaped semi-steel vertical roller is 300 mm. The components of the disc-shaped semi-steel vertical roller, by mass percentage, include: C 1.5%, Si 0.5%, Mn 0.6%, Cr 0.8%, Mo 0.2%, Ni 0.4%, with the balance being Fe and unavoidable trace impurities.

[0083] The method for preparing the disc-shaped semi-steel vertical roller in this embodiment includes:

[0084] Step 1: Keep warm at 300℃ for 6 hours;

[0085] Step 2: Increase the temperature to 660℃ at a rate of 20℃ / h;

[0086] Step 3: Keep warm at 660℃ for 5 hours;

[0087] Step 4: Increase the temperature to 860℃ at a rate of 40℃ / h;

[0088] Step 5: Hold at 860℃ for 7 hours to austenitize;

[0089] Step 6: Lift the workpiece out and cool it in the air for 10 minutes; put it into the oil tank, making sure the workpiece sinks to the bottom of the tank as much as possible, and circulate the oil for 51 minutes before removing the oil.

[0090] Step 7: After the oil has dried, immediately place the furnace into the tempering furnace and keep it at 430℃ for 10 hours;

[0091] Step 8: Increase the temperature to 550℃ at a rate of 30℃ / h and hold for 15 hours;

[0092] Step 9: Cool down to 400℃ at a rate of 15℃ / h;

[0093] Step 10: Cool down to 120°C at a rate of 8°C / h, then remove from the furnace and air cool to obtain a round, disc-shaped semi-steel vertical roller.

[0094] In this embodiment, the disc-shaped semi-steel vertical roller did not ignite when oil was discharged. The infrared detection showed that the temperature of the outer circumference of the workpiece was 195°C, and no defects such as cracks appeared in the workpiece, so it was safe.

[0095] The disc-shaped semi-steel vertical roller of this embodiment was dissected and analyzed. The test results of its microstructure, hardness, and mechanical properties are as follows:

[0096] like Figure 4 and Figure 5 The microstructure of the disc-shaped semi-steel vertical roller of this embodiment is shown. Within 100 mm from the surface, the microstructure consists of fine lamellar troostite and granular carbides. The granular carbides are relatively small, with a size ≤5 μm, and predominantly 1–2 μm. The grain size of the disc-shaped semi-steel vertical roller of this embodiment is as follows: Figure 6 As shown, the grain size is grade 8, and the grains are fine and uniform.

[0097] The test results of the hardness, mechanical properties, etc. of the disc-shaped semi-steel vertical roller in this embodiment are shown in Table 1 below.

[0098] Table 1. Detection data from Example 1

[0099]

[0100] Example 2

[0101] This embodiment provides a disc-shaped semi-steel vertical roller. The overall structure of the disc-shaped semi-steel vertical roller is the same as that of Embodiment 1. The effective cross-section of the disc-shaped semi-steel vertical roller is 550 mm. The components of the disc-shaped semi-steel vertical roller, by mass percentage, include: C 1.6%, Si 0.7%, Mn 0.4%, Cr 1.0%, Mo 0.3%, Ni 0.5%, with the balance being Fe and unavoidable trace impurities.

[0102] The method for preparing the disc-shaped semi-steel vertical roller in this embodiment includes:

[0103] Step 1: Keep warm at 280℃ for 9 hours;

[0104] Step 2: Increase the temperature to 680℃ at a rate of 20℃ / h;

[0105] Step 3: Keep warm at 680℃ for 9 hours;

[0106] Step 4: Increase the temperature to 880℃ at a rate of 40℃ / h;

[0107] Step 5: Hold at 880℃ for 18 hours to austenitize;

[0108] Step 6: Lift the workpiece out and cool it in the air for 12 minutes; then place it in the oil tank, making sure the workpiece sinks to the bottom of the tank as much as possible, and circulate the oil for 95 minutes.

[0109] Step 7: After the oil has dried, immediately place the furnace into the tempering furnace and keep it at 380℃ for 15 hours;

[0110] Step 8: Increase the temperature to 560℃ at a rate of 26℃ / h and hold for 24 hours;

[0111] Step 9: Cool down to 400℃ at a rate of 18℃ / h;

[0112] Step 10: Cool down to 120°C at a rate of 8°C / h, then remove from the furnace and air cool to obtain a round, disc-shaped semi-steel vertical roller.

[0113] In this embodiment, the disc-shaped semi-steel vertical roller did not ignite when oil was discharged. The infrared detection showed that the temperature of the outer circumference of the workpiece was 190°C, and no defects such as cracks appeared in the workpiece, indicating that it was safe.

[0114] The disc-shaped semi-steel vertical roller of this embodiment was dissected and analyzed. The test results of its microstructure, hardness, and mechanical properties are as follows:

[0115] like Figure 7 The microstructure shown is that of the disc-shaped semi-steel vertical roller of this embodiment. It consists of fine lamellar troostite and granular carbides. The granular carbides are relatively small, with a size ≤5μm, and are predominantly 1-2μm in size. The grain size of the disc-shaped semi-steel vertical roller of this embodiment is as follows: Figure 8 As shown, the grain size is grade 7.5, and the grains are fine and uniform.

[0116] The test results of the hardness, mechanical properties, etc. of the disc-shaped semi-steel vertical roller in this embodiment are shown in Table 2 below.

[0117] Table 2 Detection data from Example 2

[0118]

[0119] The inventors conducted extensive experimental research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0120] Comparative Example 1

[0121] This comparative example provides a method for preparing a circular semi-steel vertical roller with an effective cross-section of 420 mm, including:

[0122] The method for preparing the disc-shaped semi-steel vertical roller in this embodiment includes:

[0123] Step 1: Keep warm at 280℃ for 7 hours;

[0124] Step 2: Increase the temperature to 660℃ at a rate of 20℃ / h;

[0125] Step 3: Keep warm at 660℃ for 8 hours;

[0126] Step 4: Increase the temperature to 890℃ at a rate of 38℃ / h;

[0127] Step 5: Hold at 890℃ for 10 hours to austenitize;

[0128] Step 6: Lift the workpiece out and spray it for cooling;

[0129] Step 7: Stop spray cooling when the surface temperature of the workpiece reaches 350℃, and immediately put it into the tempering furnace and keep it at 360℃ for 19 hours.

[0130] Step 8: Increase the temperature to 560℃ at a rate not exceeding 30℃ / h;

[0131] Step 9: Keep warm at 560℃ for 15 hours;

[0132] Step 10: Cool down to 400℃ at a rate not exceeding 20℃ / h;

[0133] Step 11: Cool down to 120℃ at a rate not exceeding 10℃ / h.

[0134] The hardness test results of the disc-shaped semi-steel vertical roller in this embodiment are shown in Table 3 below.

[0135] Table 3 shows the detection data for Comparative Example 1.

[0136] Circumferential roller surface hardness (HSD) 42 43 48 52 56 49 45 43 Technical requirements: The hardness of the outer circumferential surface of the roll is 46-52 HSD, and the hardness uniformity is ≤3 HSD.

[0137] In the preparation process of this comparative example, spray cooling was used. Due to the inability of the workpiece to rotate, the cooling was uneven, and the surface hardness uniformity was seriously exceeded.

[0138] Comparative Example 2

[0139] This comparative example provides a method for preparing a circular semi-steel vertical roller with an effective cross-section of 450 mm, including:

[0140] The method for preparing the disc-shaped semi-steel vertical roller in this embodiment includes:

[0141] Step 1: Keep warm at 290℃ for 8 hours;

[0142] Step 2: Increase the temperature to 670℃ at a rate of 20℃ / h, with a process time of 19 hours;

[0143] Step 3: Keep warm at 670℃ for 8 hours;

[0144] Step 4: Increase the temperature to 910℃ at a rate of 40℃ / h, taking 6 hours;

[0145] Step 5: Hold at 910℃ for 15 hours to austenitize;

[0146] Step 6: Remove the workpiece and cool it in the air for 5 minutes; then place it in an oil bath and circulate the oil for 90 minutes.

[0147] Step 7: After the oil is drained, two main cracks are found on the surface of the workpiece.

[0148] The workpiece was scrapped. After research and analysis, it was found that the quenching temperature was too high and the heating time was too long, resulting in coarse grains with a grain size of level 4 and reduced matrix strength. The oil cooling time was too long, which led to the surface temperature of the workpiece being too low and the quenching stress being too high, resulting in cracks.

[0149] Comparative Example 3

[0150] This comparative example provides a method for preparing a circular semi-steel vertical roller with an effective cross-section of 360 mm, including:

[0151] The method for preparing the disc-shaped semi-steel vertical roller in this embodiment includes:

[0152] Step 1: Keep warm at 260℃ for 6 hours;

[0153] Step 2: Increase the temperature to 660℃ at a rate of 20℃ / h, with a process time of 20h;

[0154] Step 3: Keep warm at 660℃ for 7 hours;

[0155] Step 4: Increase the temperature to 860℃ at a rate of 40℃ / h, taking 5 hours;

[0156] Step 5: Hold at 860℃ for 8 hours to austenitize;

[0157] Step 6: Remove the workpiece and cool it in the air for 10 minutes; then place it in an oil tank and circulate the oil for 45 minutes.

[0158] Step 7: Oil is released, and the oil tank catches fire.

[0159] Research and analysis revealed that the oil cooling time was too short during the preparation process of this comparative example, resulting in a workpiece surface temperature >200℃, which caused the oil bath to catch fire.

[0160] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of manufacturing a semi-steel round-pan roll, characterized in that, The method for preparing the disc-shaped semi-steel vertical roller includes the following steps: Step 1: Place the round, semi-steel vertical roll forging in a furnace and hold it at the blue brittleness temperature range for 5-10 hours; the blue brittleness temperature range is 250-300℃. Step 2: Heat to 650~700℃ at a first heating rate; the first heating rate is 18~21℃ / h; Step 3: Keep warm at 650~700℃ for 5~10 hours; Step 4: Increase the temperature to 850~900℃ at a second heating rate; the second heating rate is greater than the first heating rate; Step 5: Keep warm at 850~900℃ for 6~15 hours; Step 6: Lift out the disc-shaped semi-steel vertical roller forging and air cool for 10-15 minutes. Then immerse the entire disc-shaped semi-steel vertical roller forging in an oil tank and circulate oil to cool it until the surface temperature of the disc-shaped semi-steel vertical roller forging reaches 200±10℃. Then, remove the oil immediately. Step 7: After the oil has dried, immediately place the sample in the tempering furnace and hold it at the bainitic transformation temperature. Step 8: Heat to 500~600℃ at the third heating rate and hold at that temperature; the third heating rate should be less than the second heating rate. Step 9: Cool down to 400±10℃ at the first cooling rate; Step 10: Cool down to below 120°C at the second cooling rate, then remove from the furnace and air cool to obtain a round, disc-shaped semi-steel vertical roller; The second cooling rate is less than the first cooling rate; The components of the disc-shaped semi-steel vertical roller, by mass percentage, include: C 1.5%~2.1%, Si 0.4%~0.7%, Mn 0.4%~0.7%, Cr 0.8%~1.5%, Mo 0.1%~0.4%, Ni 0.4%~1.0%, with the balance being Fe and unavoidable trace impurities; The outer contour of the disc-shaped semi-steel vertical roller is cylindrical with a height-to-diameter ratio ≤0.5, and the upper and lower circular surfaces are symmetrically opened with annular grooves. The microstructure of the disc-shaped semi-steel vertical roller prepared by the above preparation method is fine lamellar troostite and granular carbides within 100 mm of the surface, with the size of the granular carbides ≤5 μm; The circular semi-steel vertical roller prepared by the method has an outer surface hardness of 47~50 HSD, a hardness difference of ≤3HSD between different parts of the outer circumference, a tensile strength of ≥1280MPa on the outer surface of the circular semi-steel vertical roller, and an impact energy AKU of ≥9J.

2. The method of manufacturing a round-pie-shaped semi-steel vertical roll according to claim 1, characterized by, The components of the disc-shaped semi-steel vertical roller, by mass percentage, include: C 1.5%~2.1%, Si 0.5%~0.7%, Mn 0.4%~0.6%, Cr 0.8%~1%, Mo 0.1%~0.3%, Ni 0.4%~1.0%, with the balance being Fe and unavoidable trace impurities.

3. The method of manufacturing a round pie-shaped semi-steel vertical roll according to claim 1, characterized in that, In step 2, the first heating rate is 18~20℃ / h.

4. The method of claim 1, wherein the semi-steel roll is a round disc-shaped semi-steel roll. In step 4, the second heating rate is controlled to be 38~41℃ / h.

5. The method of claim 1, wherein the semi-steel roll is a round pie-shaped semi-steel roll. In step 6, during oil cooling, the disc-shaped semi-steel vertical roll forging should be placed upright on the material tray.

6. The method for preparing a disc-shaped semi-steel vertical roller according to claim 1, characterized in that, In step 9, the first cooling rate is no more than 20℃ / h.

7. A circular, disc-shaped semi-steel vertical roller, characterized in that, The disc-shaped semi-steel vertical roller is prepared using the preparation method described in any one of claims 1 to 6.

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