A work roll for an aluminum plate rolling mill and its heat treatment method
By combining differential temperature furnace heating and spray cooling with tempering treatment, the problems of uneven hardness and excessive hardened layer depth in the heat treatment of work rolls of aluminum plate rolling mills were solved, and the uniformity of hardness and resistance to accidents were improved, with the grain size reaching grade 5.5 or above.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN HEAVY EQUIP ENG RES
- Filing Date
- 2024-01-31
- Publication Date
- 2026-06-30
AI Technical Summary
Existing aluminum plate rolling mills suffer from problems such as poor control of hardness uniformity, excessively deep hardened layer, and poor accident resistance during the heat treatment process of work rolls.
The roller is heated rapidly to 1120–1200℃ using a differential temperature furnace and held for 60–90 minutes. Then, it is spray-cooled to 150–200℃ and tempered. The heating rate is controlled at 500–800℃/h and the holding time is d/10-5 to ensure a large temperature difference between the inside and outside of the roller body and a hardened layer depth of 35–50mm.
It achieves good uniformity of roll body hardness, appropriate hardened layer depth, strong resistance to accidents, and fine and uniform grains, meeting the requirement that the hardness difference at different locations is ≤3HSD, thus improving the performance of the work rolls of aluminum plate rolling mills.
Smart Images
Figure CN118006882B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of large forged steel work rolls, and particularly to an aluminum plate rolling mill work roll and its heat treatment method. Background Technology
[0002] Rolls are important spare parts in steel rolling equipment. The surface of the roll body is subjected to long-term friction and wear, contact stress, and fatigue caused by rapid cooling and heating. Therefore, the working layer of the roll body is required to have excellent wear resistance, high contact fatigue strength, and fracture resistance. Cr5 forged steel has superior hardenability, hardenability, good wear resistance and fracture resistance due to its high alloy content, making it the mainstream material for work rolls of aluminum plate rolling mills.
[0003] The final heat treatment of aluminum plate rolling mill work rolls is a surface quenching and tempering heat treatment of the roll body. It is a key process that determines the structure, hardness, stress distribution and performance of the working layer of the roll. The existing aluminum plate rolling mill work rolls are mainly produced by the following three processes: differential temperature heat treatment, bogie furnace incomplete heating and quenching, and power frequency induction heating and quenching. The existing large aluminum plate rolling mill work roll heat treatment manufacturing has the following difficulties: (1) The diameter of the aluminum plate rolling mill work roll is small and the length is large, with a length-to-diameter ratio of more than 3.5. The height of the existing power frequency induction equipment is lower than the length of the workpiece, so it cannot be produced. (2) When using the bogie furnace incomplete heating method, the workpiece is heated unevenly, so the uniformity of the roll body hardness cannot be guaranteed. When using the traditional differential temperature furnace heating process, it is not easy to achieve a large temperature difference between the inside and outside of the roll body, which results in an excessively deep hardened layer in the cross section of the roll body, causing excessive residual stress and poor accident resistance. Summary of the Invention
[0004] In view of the above, the present invention aims to provide an aluminum plate rolling mill work roll and its heat treatment method, which solves one of the problems of poor control of hardness uniformity, excessive hardened layer depth and poor accident resistance in the heat treatment process of existing aluminum plate rolling mill work rolls.
[0005] The objective of this invention is mainly achieved through the following technical solutions:
[0006] This invention improves a heat treatment method for work rolls of aluminum plate rolling mills, the heat treatment method for work rolls of aluminum plate rolling mills includes:
[0007] Step 1: Preheat the entire work roll of the aluminum plate rolling mill;
[0008] Step 2: Transfer the aluminum plate rolling mill work roll into the differential temperature furnace, heat only the roll body, and quickly raise the furnace temperature to 1120-1200℃ at a rate of 500-800℃ / h.
[0009] Step 3: Keep the temperature at 1120-1200℃ for 60-90 minutes; then spray the roller body for cooling.
[0010] Furthermore, the diameter d of the work roll of the aluminum plate rolling mill is 650-900mm, and the length of the roll is 2300-3300mm.
[0011] Furthermore, the length-to-diameter ratio of the work roll body of the aluminum plate rolling mill is 3.5 or higher.
[0012] Furthermore, in step 1, the work rolls of the aluminum plate rolling mill are preheated as a whole at 500-600℃.
[0013] Furthermore, in step 1, the heat preservation time is 2d / 100, where d is the roller diameter in mm and the heat preservation time is in hours.
[0014] Furthermore, in step 3, the heat preservation time is d / 10-5, where d is the roller diameter in mm and the heat preservation time is in min.
[0015] Furthermore, in step 3, the roller body is spray-cooled to 150-200°C and then tempered.
[0016] Furthermore, in step 2, the heating rate is 572–742 °C / h.
[0017] Furthermore, the composition of the work rolls of the aluminum plate rolling mill, by mass percentage, includes: C 0.4%–0.6%, Si 0.4%–0.8%, Mn 0.4%–0.8%, Cr 4.5%–5.5%, Mo 0.4%–0.8%, Ni 0.2%–0.6%, V 0.1%–0.3%, with the balance being Fe and unavoidable impurities.
[0018] The present invention also provides a work roll for an aluminum plate rolling mill, which is prepared by the above-described heat treatment method.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] a) In the heat treatment method of the aluminum plate rolling mill work roll of the present invention, the heating rate is accelerated in the quenching process, the heat conduction time is effectively shortened, and the internal temperature of the work roll is kept as low as possible, so as to ensure that the inner and outer parts of the roll body reach a large temperature difference, so as to achieve the purpose of accurately controlling the depth of the hardened layer to 35-50mm.
[0021] b) In the heat treatment method of the aluminum plate rolling mill work roll of the present invention, by controlling the precise preheating temperature, not only can the workpiece enter the plastic state to withstand the subsequent rapid heating, but the core temperature should also be kept as low as possible to achieve the effect of a large temperature difference between the inside and outside.
[0022] c) In the heat treatment method of the aluminum plate rolling mill work roll of the present invention, by increasing the furnace temperature and shortening the holding time, the internal temperature of the workpiece is kept as low as possible when the temperature in the working layer depth reaches the set quenching temperature, so as to achieve the purpose of accurately controlling the depth of the hardened layer.
[0023] d) The roll body hardness of the aluminum plate rolling mill work roll of the present invention is 70-80 HSD, for example 72-80 HSD; the roll body hardness uniformity is good, and the hardness difference between different positions is ≤3 HSD, for example ≤2 HSD; the hardened layer depth is appropriate, which is 35-50 mm; the hardness reduction at the working layer depth is ≤2 HSD, and the accident resistance is good.
[0024] e) The work rolls of the aluminum plate rolling mill of the present invention have fine and uniform grains with a grain size of 5.5 or higher.
[0025] Other features and advantages of the invention will be set forth in the description which follows, 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 and the accompanying drawings. Attached Figure Description
[0026] 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.
[0027] Figure 1 This is a schematic diagram of the work rolls of the aluminum plate rolling mill of the present invention;
[0028] Figure 2 This is a schematic diagram of the heat treatment method of the present invention;
[0029] Figure 3 The hardened layer curve of Embodiment 1 of the present invention;
[0030] Figure 4 The hardened layer curve of Embodiment 2 of the present invention;
[0031] Figure 5 This is a schematic diagram of the heat treatment method of Comparative Example 1 of the present invention. Detailed Implementation
[0032] 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.
[0033] As attached Figure 1As shown, this invention provides a work roll for an aluminum plate rolling mill. The work roll has a roll body diameter d of 650–900 mm and a roll body length of 2300–3300 mm. The work roll has a small roll body diameter and a large length, with a length-to-diameter ratio of over 3.5. Through in-depth research, the inventors discovered that: existing power frequency induction equipment is shorter than the workpiece length, making production impossible; the bogie furnace method, which involves incomplete heating, cannot guarantee the uniformity of roll body hardness due to uneven heating of the workpiece; and the traditional differential temperature furnace heating process makes it difficult to achieve a large temperature difference between the inside and outside of the roll body, resulting in an excessively deep hardened layer in the roll body cross-section, causing excessive residual stress and poor accident resistance.
[0034] Specifically, the components of the aluminum plate rolling mill work roll of the present invention, by mass percentage, include: C 0.4% to 0.6%, Si 0.4% to 0.8%, Mn 0.4% to 0.8%, Cr 4.5% to 5.5%, Mo 0.4% to 0.8%, Ni 0.2% to 0.6%, V 0.1% to 0.3%, with the balance being Fe and unavoidable impurities.
[0035] like Figure 2 As shown, the present invention provides a heat treatment method for work rolls of an aluminum plate rolling mill, comprising:
[0036] Step 1: Preheat the aluminum plate rolling mill work rolls as a whole at 500-600℃;
[0037] Step 2: Transfer the aluminum plate rolling mill work roll into the differential temperature furnace, heat only the roll body, and quickly raise the furnace temperature to 1120-1200℃ at a rate of 500-800℃ / h.
[0038] Step 3: Keep the roller body at 1120-1200℃ to rapidly heat the surface for 60-90 minutes; then spray the roller body to cool it to 150-200℃ and then temper it.
[0039] Specifically, in step 1 above, considering that excessively high preheating temperatures can lead to excessive hardened layer depth and residual stress, which is detrimental to safe use; excessively low preheating temperatures or short holding times result in low core temperatures and a still elastic state, making the core unable to withstand subsequent rapid heating and prone to cracking; and excessively long holding times lead to both energy waste and excessively long production cycles. Therefore, the aluminum plate rolling mill work rolls are preheated at 500–600℃, with a holding time of 2d / 100, where d is the roll diameter in mm and the holding time is in hours.
[0040] Specifically, in step 2 above, rapid heating is used to ensure a large temperature difference between the inside and outside of the roller body, thereby shortening the heating time and effectively shortening the heat conduction time, so that the internal temperature of the roller body is as low as possible; therefore, the heating rate is controlled at 500-800℃ / h, for example: 572-742℃ / h.
[0041] Specifically, in step 2 above, if the furnace temperature is too low, the quenching temperature of the roller surface will be too low; if the furnace temperature is too high, it will exceed the heating capacity of the equipment. Therefore, the furnace temperature is rapidly raised to 1120-1200℃.
[0042] Specifically, in step 3 above, considering that excessively long holding time can easily lead to excessively high core temperature, resulting in an excessively deep hardened layer, a small internal and external temperature difference, and excessive residual stress; and that excessively short holding time can easily lead to an excessively low heating temperature from the surface to the working layer, resulting in an excessively shallow hardened layer that fails to meet technical requirements, the holding time is controlled to d / 10⁻⁵, where d is the roller diameter in mm and the holding time is in minutes. This ensures that the roller surface reaches the predetermined quenching temperature of 950–990℃, and the temperature difference between the roller surface and the core reaches at least 350℃.
[0043] Specifically, in step 3 above, in order to ensure that the hardened layer achieves a fully martensitic structure, the temperature in the hardened layer needs to be reduced to below Ms point (300℃) during the cooling stage. Therefore, the roller body is controlled to be cooled by spray cooling to 150-200℃ before tempering.
[0044] Specifically, in step 3 above, the tempering treatment includes: maintaining the temperature at 250-300℃ for 10 hours, then raising the temperature to 450-520℃ at a rate of ≤30℃ / h, holding at 450-520℃ for 40-55 hours, cooling the furnace to 150℃, and then removing the furnace.
[0045] Specifically, in step 3 above, the hardness of the work roll of the aluminum plate rolling mill after tempering is 70-80 HSD, for example 72-80 HSD; the uniformity of the roll body hardness is good, and the hardness difference between different positions is ≤3 HSD, for example ≤2 HSD; the hardened layer depth is 35-50 mm; and the hardness reduction at the working layer depth is ≤2 HSD.
[0046] Specifically, in step 3 above, the work rolls of the aluminum plate rolling mill after tempering have fine and uniform grains with a grain size of 5.5 or higher, for example, a grain size of 6 to 6.5.
[0047] The advantages of precise control of process parameters of the present invention will be demonstrated below with specific embodiments and comparative examples.
[0048] Example 1
[0049] This embodiment provides a heat treatment method for work rolls of an aluminum plate rolling mill; the diameter of the work roll body of this invention is... The working roll of this invention has a diameter of 3200 mm and a roll body length of 3200 mm. Technical requirements include: roll body hardness of 70–75 HSD, working layer depth of 35 mm, and hardness drop ≤ 2 HSD. The composition of the working roll of this invention includes C 0.48%, Si 0.60%, Mn 0.52%, Cr 4.71%, Mo 0.51%, Ni 0.38%, V 0.15%, with the balance being Fe and unavoidable impurities.
[0050] The heat treatment method in this embodiment includes:
[0051] Step 1: Before differential heating of the rolls, preheat the entire roll body to 520℃ for 17 hours to bring the entire roll body cross section into a plastic state.
[0052] Step 2: Transfer the roll into the differential temperature furnace, heat only the roll body and air cool the roll neck; use maximum power to rapidly raise the furnace temperature to 1140℃, heating time 65min, heating rate 572℃ / h;
[0053] Step 3: Hold at 1140℃ for 80 minutes, the temperature difference between the roller surface and the core reaches more than 350℃, spray the roller body to 150℃ and then perform tempering treatment; the tempering treatment includes: holding at 280℃ for 10 hours, then raising the temperature to 515℃ at a rate of 20℃ / h, holding at 515℃ for 45 hours, furnace cooling to 150℃, and then removing from the furnace.
[0054] The working roller in this embodiment has fine and uniform grains with a grain size of 6.0 grade.
[0055] The surface hardness and hardened layer curve of the roller body in this embodiment were tested. The roller body hardness was 72-74 HSD, the hardness at a depth of 40 mm from the roller body surface was 70-72 HSD, the hardened layer depth was about 50 mm, the hardness difference at different positions was ≤2 HSD, and the hardness reduction at the working layer depth was ≤2 HSD. All performance indicators met the technical requirements.
[0056] Specifically, the surface hardness of the roller body in this embodiment is shown in Table 1 below, and the hardened layer curve of this embodiment is as follows: Figure 3 As shown.
[0057] Table 1. Roller body hardness (HSD) of Example 1
[0058] Busbar 1 72 72 73 73 72 Busbar 2 72 73 74 73 72 Busbar 3 72 74 73 73 72 Busbar 4 72 72 73 74 72
[0059] Example 2:
[0060] This embodiment provides a heat treatment method for work rolls of an aluminum plate rolling mill; the diameter of the work roll body of this invention is... The working roll of this invention has a diameter of 20 mm and a roll body length of 2300 mm. Technical requirements include: roll body hardness of 72–78 HSD, working layer depth of 30 mm, and hardness drop ≤ 2 HSD. The composition of the working roll of this invention includes: C 0.52%, Si 0.42%, Mn 0.45%, Cr 4.88%, Mo 0.48%, Ni 0.52%, V 0.18%, with the balance being Fe and unavoidable impurities.
[0061] The heat treatment method in this embodiment includes:
[0062] Step 1: Before differential heating of the rolls, preheat the entire roll body to 510℃ for 13 hours to bring it into a plastic state.
[0063] Step 2: Transfer the roll into the differential temperature furnace, heat only the roll body and air cool the roll neck; use maximum power to rapidly raise the furnace temperature to 1180℃, heating time 55min, heating rate 742℃ / h;
[0064] Step 3: Hold at 1180℃ for 60 minutes, the temperature difference between the roller surface and the core reaches more than 350℃, spray the roller body to 180℃ and then perform tempering treatment; the tempering treatment includes: holding at 290℃ for 10 hours, then raising the temperature to 495℃ at a rate of 30℃ / h, holding at 495℃ for 40 hours, furnace cooling to 150℃, and then removing from the furnace.
[0065] The working roller in this embodiment has fine and uniform grains with a grain size of 6.5.
[0066] The surface hardness and hardened layer curve of the roller body in this embodiment were tested. The roller body hardness was 75-77 HSD, the hardness at a depth of 35 mm from the roller body surface was 73-76 HSD, the hardened layer depth was about 40 mm, the hardness difference at different positions was ≤2 HSD, and the hardness reduction at the working layer depth was ≤2 HSD. All performance indicators met the technical requirements.
[0067] Specifically, the surface hardness of the roller body in this embodiment is shown in Table 2 below, and the hardened layer curve of this embodiment is as follows. Figure 4 As shown.
[0068] Table 2. Roller body hardness (HSD) of Example 2
[0069] Busbar 1 75 75 77 76 75 Busbar 2 76 76 77 76 75 Busbar 3 75 76 76 76 75 Busbar 4 75 76 77 76 75
[0070] Example 3:
[0071] This embodiment provides a heat treatment method for work rolls of an aluminum plate rolling mill; the diameter of the work roll body of this invention is... The working roll of this invention has a diameter of 2880 mm and a roll body length of 2880 mm. Technical requirements include: roll body hardness of 75–80 HSD, working layer depth of 35 mm, and hardness drop ≤ 2 HSD. The composition of the working roll of this invention includes: C 0.58%, Si 0.52%, Mn 0.48%, Cr 5.01%, Mo 0.45%, Ni 0.42%, V 0.21%, with the balance being Fe and unavoidable impurities.
[0072] The heat treatment method in this embodiment includes:
[0073] Step 1: Before differential heating of the rolls, preheat the entire roll body to 500℃ for 15 hours to bring it into a plastic state.
[0074] Step 2: Transfer the roll into the differential temperature furnace, heat only the roll body and air cool the roll neck; use maximum power to rapidly raise the furnace temperature to 1160℃, heating time 60min, heating rate 660℃ / h;
[0075] Step 3: Hold at 1160℃ for 70 minutes, so that the temperature difference between the roller surface and the core reaches more than 350℃; spray the roller body to 170℃ and then perform tempering treatment; the tempering treatment includes: holding at 260℃ for 10 hours, then raising the temperature to 465℃ at a rate of 25℃ / h, holding at 465℃ for 42 hours, furnace cooling to 150℃, and then removing from the furnace.
[0076] The working roller in this embodiment has fine and uniform grains with a grain size of 6.5.
[0077] The surface hardness and hardened layer of the roller body in this embodiment were tested. The roller body hardness was 78-80 HSD, the hardness at a depth of 40 mm from the roller body surface was 76-78 HSD, the hardened layer depth was about 50 mm, the hardness difference at different locations was ≤2 HSD, and the hardness reduction at the working layer depth was ≤2 HSD. All performance indicators met the technical requirements.
[0078] The inventors conducted extensive research during the research process, and some poorly performing solutions are now presented as comparative examples.
[0079] Comparative Example 1
[0080] This comparative example provides a heat treatment method for work rolls in an aluminum plate rolling mill, wherein the work roll body diameter... The roller has a diameter of 20 mm and a length of 2600 mm. Technical requirements include a roller body hardness of 72–78 HSD, a working layer depth of 30 mm, and a hardness drop of ≤2 HSD. The material of the working roller is the same as in Example 1 and will not be repeated here.
[0081] like Figure 5 As shown, this comparative example uses a traditional differential temperature heating process, and the steps are as follows:
[0082] Step 1: Before differential heating of the rolls, preheat the entire roll body to 500℃ for 14 hours to bring it into a plastic state.
[0083] Step 2: Transfer the roll into the differential temperature furnace, heat only the roll body and air cool the roll neck; raise the furnace temperature to 1070℃, raise the temperature for 90 minutes, and raise the temperature rate at 380℃ / h.
[0084] Step 3: Maintain at 1070℃ for 80 minutes;
[0085] Step 4: Reduce the furnace temperature to 990℃, and the cooling time is 40 minutes;
[0086] Step 5: Hold at 990℃ for 40 minutes; spray the roller body to 170℃ and then temper at 505℃.
[0087] The surface hardness and hardened layer curve of the roller body were tested. The roller body hardness was 74-76 HSD, and the hardness at a depth of 120 mm from the roller body surface was 70-75 HSD. The hardened layer depth was much greater than the technical requirements, which poses a safety hazard in use.
[0088] Comparative Example 2
[0089] This comparative example provides a heat treatment method for work rolls in an aluminum plate rolling mill. The material and dimensions of the work rolls are the same as in Example 2, and will not be repeated here. The preparation method of this comparative example is consistent with the overall steps of Example 2, except that:
[0090] In step 1, the entire system is preheated at 350℃ for 13 hours.
[0091] The work roll in this comparative example has a surface hardness of 73-75 HSD and a hardened layer depth of 30mm after heat treatment, which meets the technical requirements. However, after finishing and flaw detection, it was found that the core of the work roll has no bottom and the defect is a crack.
[0092] The workpiece was scrapped. After research and analysis, it was found that the preheating temperature was too low and the core area had not yet reached the plastic state, resulting in weak plastic deformation capacity. When the temperature was subsequently increased to 1180℃ at a rate of 742℃ / h, the core area failed due to excessive tensile stress.
[0093] Comparative Example 3
[0094] This comparative example provides a heat treatment method for work rolls in an aluminum plate rolling mill. The material and dimensions of the work rolls are the same as in Example 3, and will not be repeated here. The preparation method of this comparative example is consistent with the overall steps of Example 3, except that:
[0095] In step 3, maintain at 1160℃ for 50 minutes.
[0096] The hardness at a depth of 35mm from the roller surface is 73-76HSD, the hardened layer depth is about 40mm, the hardness difference at different locations is ≤2HSD, the hardness decrease at the working layer depth is ≤2HSD, and all performance indicators meet the technical requirements.
[0097] The work roll in this comparative example has a surface hardness of 72-75 HSD after heat treatment, a hardness of 65-68 HSD at a depth of 35mm from the surface, and a hardened layer depth of 28mm, which does not meet the technical requirements.
[0098] The workpiece underwent differential temperature heat treatment for repair. Analysis revealed that the holding time at 1160℃ was too short, and the quenching temperature within the hardened layer was too low, resulting in insufficient hardened layer and a significant decrease in hardness.
[0099] 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 heat treatment method for work rolls of an aluminum sheet rolling mill, characterized by, The heat treatment method for the work rolls of the aluminum plate rolling mill includes: Step 1: Preheat the aluminum plate rolling mill work rolls as a whole at 500~600℃; Step 2: Transfer the aluminum plate rolling mill work roll into the differential temperature furnace, heat only the roll body, and quickly raise the furnace temperature to 1120~1200℃ at a rate of 500~800℃ / h. Step 3: Keep the temperature at 1120~1200℃ for 60~90 min; then spray the roller body for cooling.
2. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, The working roll of the aluminum plate rolling mill has a roll diameter d of 650~900mm and a roll length of 2300~3300mm.
3. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, The length-to-diameter ratio of the work roll of the aluminum plate rolling mill is 3.5 or higher.
4. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, In step 1, the work rolls of the aluminum plate rolling mill are preheated as a whole at 500~520℃.
5. The heat treatment method of aluminum plate rolling mill work rolls according to claim 4, characterized in that, In step 1, the heat preservation time is 2d / 100, where d is the roller diameter in mm and the heat preservation time is in hours.
6. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, In step 3, the heat preservation time is d / 10-5, where d is the roller diameter in mm and the heat preservation time is in min.
7. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, In step 3, the roller body is spray-cooled to 150~200℃ and then tempered.
8. The heat treatment method of aluminum plate rolling mill work rolls according to claim 1, characterized by, In step 2, the heating rate is 572~742℃ / h.
9. The heat treatment method of aluminum sheet rolling mill work rolls according to any one of claims 1 to 8, characterized in that, The composition of the aluminum plate rolling mill work rolls, by mass percentage, includes: C 0.4%~0.6%, Si 0.4%~0.8%, Mn 0.4%~0.8%, Cr 4.5%~5.5%, Mo 0.4%~0.8%, Ni 0.2%~0.6%, V 0.1%~0.3%, with the balance being Fe and unavoidable impurities.
10. A work roll for an aluminum plate rolling mill, characterized in that, It is prepared by the heat treatment method according to any one of claims 1 to 9.