A rolling method of Cr12MoV flat steel
By combining continuous heating and reciprocating rolling with annealing, the problems of long process, high energy consumption and uneven microstructure in the rolling process of Cr12MoV flat steel were solved, and efficient and low-energy production of Cr12MoV flat steel was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG INST OF ADVANCED MATERIALS SHU
- Filing Date
- 2023-05-06
- Publication Date
- 2026-08-04
AI Technical Summary
Existing Cr12MoV flat steel rolling methods suffer from problems such as long manufacturing process, high energy consumption, low yield, and central porosity and uneven carbides in continuously cast billets.
The method of continuous heating and reciprocating rolling combined with annealing treatment is adopted, including preheating, heating, homogenization, reciprocating rolling and annealing. The reduction rate and temperature of each pass are controlled to ensure uniform heating and deformation of Cr12MoV continuous casting billets, eliminate structural defects and achieve one-fire forming.
The prepared Cr12MoV flat steel has a central porosity level of less than 1.5 and a carbide inhomogeneity level of less than 2.5. The manufacturing process is short and energy consumption is low, making it suitable for industrial production.
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Figure CN116511238B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cold work die steel processing technology, and in particular to a rolling method for Cr12MoV flat steel. Background Technology
[0002] Cr12MoV is a type of cold work die steel, widely used in the manufacture of cold extrusion dies, etc. It has a high carbon content and high degree of alloying, and belongs to ledeburitic steel. Due to the high carbon and high alloying of Cr12MoV, its thermal conductivity and thermoplasticity are poor, which can easily lead to cracking or excessive carbide levels when it is prepared by hot working.
[0003] The current mainstream process route is: ingot casting or continuous casting - ingot or billet annealing - billet preparation - annealing - furnace heating - flat steel rolling - annealing. This production route has problems such as long manufacturing process, high energy consumption and cost, and low yield. For example, the invention patent with publication number CN103316910A discloses "a method for rolling Cr12MoV flat steel". The rolling method of this patent uses ingot casting to prepare flat steel through a primary rolling mill. It requires ingot preparation first, followed by rolling, resulting in two heats and a long process with high energy consumption. The invention patent with publication number CN103909092A discloses "a one-heat rolling method for Cr12MoV cold work die steel". Although the rolling method of this patent has a short process and low energy consumption, it uses ingot casting instead of continuously cast billets. Due to dendrite bridging during the drawing and cooling processes, continuously cast billets have difficulty replenishing the solidified molten steel at the center, resulting in low density and defects such as porosity and voids. Even after rolling, it is difficult to effectively reduce the porosity level at the center of the microstructure. Moreover, continuously cast billets have worse thermoplasticity than ingots. Therefore, the rolling method disclosed in this patent is not suitable for one-fire rolling of continuously cast billets. Summary of the Invention
[0004] The purpose of this invention is to provide a rolling method for Cr12MoV flat steel. The rolling method provided by this invention enables the rolled Cr12MoV flat steel to have a low level of central porosity and carbide inhomogeneity, and it can be produced in one firing, with a short manufacturing process and low energy consumption.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0006] The present invention provides a rolling method for Cr12MoV flat steel, comprising the following steps:
[0007] (1) Cr12MoV continuous casting billet is continuously heated to obtain Cr12MoV ingot billet to be heated.
[0008] (2) The Cr12MoV ingot obtained in step (1) is subjected to reciprocating rolling to obtain Cr12MoV rolled billet;
[0009] (3) Anneal the Cr12MoV rolled billet obtained in step (2) to obtain Cr12MoV flat steel;
[0010] In step (2), the total number of reciprocating rolling passes is n, where n = 10 to 16. During the reciprocating rolling, the relative reduction rate of the first pass is 2 to 5%, the relative reduction rate of each pass of the second to fourth passes is independently 6 to 10%, the relative reduction rate of each pass of the fifth to (n-2) passes is independently 15 to 20%, and the relative reduction rate of each pass of the (n-1) to nth passes is independently 2 to 5%.
[0011] Preferably, the initial rolling temperature of the reciprocating rolling in step (2) is 1080-1130°C, and the temperature of the fifth rolling pass to the final rolling pass is independently 950-1000°C.
[0012] Preferably, before reciprocating rolling in step (2), high-pressure water descaling is performed, and the water pressure for high-pressure water descaling is 17-19 MPa.
[0013] Preferably, the cooling method after the reciprocating rolling in step (2) is air cooling to room temperature.
[0014] Preferably, the continuous heating in step (1) includes preheating, first-stage heating, second-stage heating and homogenization in sequence.
[0015] Preferably, the initial temperature of the preheating is room temperature, the final temperature of the preheating is 550-650°C, and the preheating time is 90-120 minutes.
[0016] Preferably, the final temperatures of the first-stage heating and the second-stage heating are independently 1100–1150°C, the heating times of the first-stage heating and the second-stage heating are independently 60–90 min, and the final temperature of the second-stage heating is 1–5°C higher than the final temperature of the first-stage heating.
[0017] Preferably, the heat-equalizing temperature is 1160–1190°C, and the heat-equalizing time is 30–60 min.
[0018] Preferably, the holding temperature for annealing in step (3) is 860-880°C, and the holding time for annealing is 5-6 hours.
[0019] Preferably, the cooling method for the annealing treatment is as follows: the temperature is reduced from the holding temperature of the annealing treatment to 300°C at a cooling rate of 70-80°C / h, and then air-cooled to room temperature.
[0020] This invention provides a rolling method for Cr12MoV flat steel, comprising the following steps: continuously heating a Cr12MoV continuous casting billet to obtain a Cr12MoV ingot billet awaiting heating; reciprocatingly rolling the Cr12MoV ingot billet awaiting heating to obtain a Cr12MoV rolled billet; annealing the Cr12MoV rolled billet to obtain Cr12MoV flat steel; the total number of reciprocating rolling passes is n, where n = 10 to 16; during the reciprocating rolling, the relative reduction rate of the first pass is 2 to 5%, the relative reduction rate of each pass in the second to fourth passes is independently 6 to 10%, the relative reduction rate of each pass in the fifth to (n-2)th passes is independently 15 to 20%, and the relative reduction rate of each pass in the (n-1) to nth passes is independently 2 to 5%. This invention uses Cr12MoV continuously cast billets as raw materials. Continuous heating of the billets ensures uniform heating of both the surface and central structures, maintaining consistent thermoplasticity throughout. This continuous heating process also improves or eliminates segregation, resulting in a more uniform microstructure. This allows for uniform deformation during reciprocating rolling, preventing rolling cracks and improving defects in the central microstructure. During reciprocating rolling, by controlling the number of rolling passes and the relative reduction rate per pass, the Cr12MoV billet undergoes gradual thermoplastic deformation, effectively closing defects such as porosity and voids in the central microstructure, resulting in a more uniform and dense microstructure. Simultaneously, it breaks down coarse carbides, causing them to redistribute and dynamically recrystallize under plastic deformation, effectively refining and uniformly distributing grain size. Finally, annealing eliminates rolling stress and induces static recrystallization of the deformed microstructure, further refining and uniformly distributing grain size.
[0021] The results of the embodiments show that the Cr12MoV flat steel prepared by the rolling method provided by the present invention has a central porosity level ≤1.5 and a carbide inhomogeneity level ≤2.5. Moreover, the rolled product can be obtained by only one annealing, that is, one-fire production, with a short manufacturing process and low energy consumption. Attached Figure Description
[0022] Figure 1 Low-magnification image of the interface morphology for rating the center porosity level of the Cr12MoV flat steel provided in Embodiment 1 of the present invention.
[0023] Figure 2 Low-magnification image of the interface morphology for rating the center porosity level of Cr12MoV flat steel provided in Embodiment 2 of the present invention.
[0024] Figure 3 Low magnification image of the interface morphology for rating the center porosity level of the Cr12MoV continuous casting billet provided in Comparative Example 1 of this invention.
[0025] Figure 4Low magnification image of the interface morphology for rating the center porosity level of the Cr12MoV continuous casting billet provided in Comparative Example 2 of this invention.
[0026] Figure 5 An optical micrograph of the carbide inhomogeneity rating at the 1 / 4 diagonal of the Cr12MoV flat steel provided in Embodiment 1 of the present invention.
[0027] Figure 6 An optical micrograph of the carbide inhomogeneity rating at the 1 / 4 diagonal of the Cr12MoV flat steel provided in Embodiment 2 of the present invention.
[0028] Figure 7 An optical micrograph of the carbide inhomogeneity rating at the 1 / 4 diagonal of the Cr12MoV continuous casting billet provided in Comparative Example 1 of this invention.
[0029] Figure 8 An optical micrograph of the carbide inhomogeneity rating at the 1 / 4 diagonal of the Cr12MoV continuous casting billet provided in Comparative Example 2 of this invention. Detailed Implementation
[0030] This invention provides a method for rolling Cr12MoV flat steel, comprising the following steps:
[0031] (1) Cr12MoV continuous casting billet is continuously heated to obtain Cr12MoV ingot billet to be heated.
[0032] (2) The Cr12MoV ingot obtained in step (1) is subjected to reciprocating rolling to obtain Cr12MoV rolled billet;
[0033] (3) Anneal the Cr12MoV rolled billet obtained in step (2) to obtain Cr12MoV flat steel;
[0034] In step (2), the total number of reciprocating rolling passes is n, where n = 10 to 16. During the reciprocating rolling, the relative reduction rate of the first pass is 2 to 5%, the relative reduction rate of each pass of the second to fourth passes is independently 6 to 10%, the relative reduction rate of each pass of the fifth to (n-2) passes is independently 15 to 20%, and the relative reduction rate of each pass of the (n-1) to nth passes is independently 2 to 5%.
[0035] This invention involves continuously heating a Cr12MoV continuous casting billet to obtain a Cr12MoV ingot billet awaiting heating.
[0036] The present invention does not have any special requirements on the source of the Cr12MoV continuous casting billet; any Cr12MoV continuous casting billet prepared by conventional commercial or conventional methods in the art can be used.
[0037] In this invention, the continuous heating preferably includes preheating, first-stage heating, second-stage heating, and homogenization in sequence.
[0038] In this invention, the initial preheating temperature is preferably room temperature, and the final preheating temperature is preferably 550–650°C, more preferably 560–600°C; the preheating time is preferably 90–120 min, more preferably 95–110 min. This invention, by preheating before continuous heating, allows the Cr12MoV continuous casting billet to gradually rise to a higher temperature from room temperature, and by controlling its final temperature and time, it enables a lower heating rate, resulting in more uniform heating of the billet's microstructure. In this invention, the preheating rate can be determined by room temperature, the final preheating temperature, and the preheating time.
[0039] In this invention, the final temperature of the first-stage heating is preferably 1100–1150°C, more preferably 1120–1140°C; the heating time of the first-stage heating is preferably 60–90 min, more preferably 70–80 min. By controlling the final temperature and time of the first-stage heating within the above ranges, this invention allows the Cr12MoV continuous casting billet to continue to be slowly heated. During the slow heating process, the surface and center of the Cr12MoV continuous casting billet are heated evenly, avoiding adverse effects caused by prolonged contact of the surface with high temperatures, while also ensuring that the central structure is fully heated. In this invention, the heating rate of the first-stage heating can be determined by the final preheating temperature, the final temperature of the first-stage heating, and the heating time.
[0040] In this invention, the final temperature of the second-stage heating is preferably 1100–1150°C, more preferably 1120–1140°C; the heating time of the second stage is preferably 60–90 min, more preferably 70–80 min. In this invention, the final temperature of the second-stage heating is preferably 1–5°C higher than the final temperature of the first-stage heating, more preferably 2–3°C. By controlling the final temperature and time of the second-stage heating within the above ranges, this invention enables the Cr12MoV continuous casting billet to have its central structure fully heated within a relatively stable temperature range. In this invention, the heating rate of the second-stage heating can be determined by the final temperature of the first-stage heating, the final temperature of the second-stage heating, and the heating time.
[0041] In this invention, the preferred heat-soaking temperature is 1160–1190°C, more preferably 1170–1180°C; the preferred heat-soaking time is 30–60 min, more preferably 40–50 min. By controlling the heat-soaking temperature and time within the above ranges, this invention allows the Cr12MoV continuously cast billet to be fully heated, improves segregation in the microstructure, facilitates subsequent reciprocating rolling, reduces deformation resistance during rolling, and avoids induced cracking.
[0042] In this invention, the continuous heating equipment is preferably a walking beam furnace; the total length of the walking beam furnace is preferably 29-37m, more preferably 32-34m; the preheating step distance is preferably 11-13m, more preferably 12m; and the step distances for the first-stage heating, second-stage heating, and homogenization are independently preferably 6-8m. By selecting the above-mentioned continuous heating equipment, this invention is more conducive to a slow temperature rise during the continuous heating process and to ensuring that the Cr12MoV continuous casting billet is heated uniformly and sufficiently.
[0043] After obtaining the Cr12MoV ingot blank to be heated, the present invention performs reciprocating rolling on the Cr12MoV ingot blank to obtain the Cr12MoV rolled blank.
[0044] In this invention, high-pressure water descaling is preferably performed before the reciprocating rolling. The water pressure for high-pressure water descaling is preferably 17-19 MPa, more preferably 18 MPa. This invention removes the oxide scale formed on the surface of the Cr12MoV ingot during the continuous heating process by performing high-pressure water descaling, which is more conducive to subsequent reciprocating rolling operations and ensures the surface quality of the Cr12MoV rolled ingot.
[0045] In this invention, the total number of passes in the reciprocating rolling is n, where n = 10 to 16; during the reciprocating rolling, the relative reduction rate of the first pass is 2 to 5%, preferably 3 to 4%; the relative reduction rate of each pass in the second to fourth passes is independently 6 to 10%, preferably 7 to 9%, more preferably 8%; the relative reduction rate of each pass in the fifth to (n-2)th passes is independently 15 to 20%, preferably 16 to 19%, more preferably 17 to 18%; and the relative reduction rate of each pass in the (n-1)th to nth passes is independently 2 to 5%, preferably 3 to 4%. This invention improves the central microstructure of Cr12MoV continuously cast billets during multi-pass rolling by controlling the total number of reciprocating rolling passes within the aforementioned range. Specifically, controlling the relative reduction rate of the first pass within this range is more conducive to the effective biting of the billet into the rolls at the start of rolling. During the initial rolling process, the center of the Cr12MoV continuously cast billet has many defects, and large deformation can easily induce cracks. Therefore, this invention controls the relative reduction rate of each pass from the 2nd to the 4th passes within the aforementioned range. In the subsequent 5th to (n-2)th passes, a larger deformation is used to ensure sufficient carbide breaking and core compaction, effectively closing defects such as porosity and voids. By controlling the relative reduction rate of the last two passes within the aforementioned range, the deformed microstructure can have higher precision, which is more conducive to obtaining Cr12MoV flat steel products with a high compression ratio.
[0046] In this invention, the initial rolling temperature of the reciprocating rolling is preferably 1080–1130°C, more preferably 1100–1120°C; the temperature from the fifth pass to the final rolling is independently preferably 950–1000°C, more preferably 960–990°C. By controlling the initial rolling temperature of the reciprocating rolling and the temperature from the fifth pass to the final rolling within the above ranges, this invention can ensure that the deformed microstructure has lower deformation resistance, better thermoplasticity, and is more conducive to microstructure flow and grain breakage, thereby achieving porosity, pore closure, and the breakage and uniform distribution of coarse carbides.
[0047] In this invention, the preferred cooling method after the reciprocating rolling is air cooling to room temperature.
[0048] After obtaining the Cr12MoV rolled billet, the present invention performs annealing treatment on the Cr12MoV rolled billet to obtain Cr12MoV flat steel.
[0049] In this invention, the Cr12MoV rolled billets are preferably placed in a stacked manner during the annealing process. This invention does not have special requirements regarding the number of layers or thickness of the stacked billets, as long as it ensures uniform heating of the Cr12MoV rolled billets. By placing the Cr12MoV rolled billets in a stacked manner for annealing, this invention saves more space, allows more Cr12MoV rolled billets to be annealed in the same batch, and reduces energy consumption.
[0050] In this invention, the holding temperature of the annealing treatment is preferably 860–880°C, more preferably 870°C; the holding time of the annealing treatment is preferably 5–6 hours, more preferably 5.5 hours. By controlling the holding temperature and holding time of the annealing treatment within the above ranges, this invention can eliminate rolling deformation stress and cause static recrystallization of the deformed structure, further refining the grain size and making it uniformly distributed.
[0051] In this invention, the heating rate from room temperature to the holding temperature of the annealing treatment is preferably 40–50 °C / h, more preferably 43–48 °C / h. By controlling the heating rate of the annealing treatment within the above range, this invention is more conducive to the uniform heating of the Cr12MoV rolled billet.
[0052] In this invention, the preferred cooling method for the annealing treatment is to cool the annealing temperature to 300°C at a cooling rate of 70-80°C / h, followed by air cooling to room temperature. By employing the above-mentioned cooling method for the annealing treatment, this invention can avoid excessive heating of the microstructure caused by residual heat from annealing during the cooling process of Cr12MoV flat steel.
[0053] In this invention, the height compression ratio of the Cr12MoV flat steel is preferably 2 to 8, more preferably 2.5 to 7.5. The rolling method provided by this invention enables the prepared Cr12MoV flat steel to have a high height compression ratio, which not only effectively closes the looseness and pores in the microstructure center, but also effectively refines the carbides and makes them evenly distributed.
[0054] The rolling method provided by this invention enables the rolled Cr12MoV flat steel to have a low level of central porosity and carbide inhomogeneity, and it is produced in one firing process with a short manufacturing process and low energy consumption, which is more conducive to the industrialization and large-scale production of Cr12MoV flat steel.
[0055] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0056] Example 1
[0057] A rolling method for Cr12MoV flat steel comprises the following steps:
[0058] (1) Cr12MoV continuous casting billet is continuously heated to obtain Cr12MoV ingot billet to be heated.
[0059] The dimensions of the continuously cast billet are: thickness 150mm, width 630mm, and length 3m.
[0060] The continuous heating process consists of preheating, first-stage heating, second-stage heating, and homogenization heating in sequence. The final temperature of the preheating is 561°C, and the time is 97 minutes. The final temperature of the first-stage heating is 1123°C, and the time is 76 minutes. The final temperature of the second-stage heating is 1125°C, and the time is 83 minutes. The holding temperature for homogenization heating is 1187°C, and the holding time is 41 minutes. The final temperature of the second-stage heating is 2°C higher than the final temperature of the first-stage heating.
[0061] The continuous heating equipment is a walking beam furnace with a total step length of 33m (the preheating step is 12m, and the step lengths for the first stage heating, second stage heating, and homogenization are 7m each).
[0062] (2) The Cr12MoV ingot obtained in step (1) is subjected to reciprocating rolling to obtain Cr12MoV rolled billet; wherein, before reciprocating rolling, high-pressure water dephosphorization is performed, and the water pressure for high-pressure water dephosphorization is 18MPa.
[0063] The initial rolling temperature during reciprocating rolling is 1100℃, and the total number of reciprocating rolling passes n is 14. The relative reduction rate of the first pass is 3%, the relative reduction rate of each pass of the 2nd to 4th passes is 8%, and the surface temperature is raised to 967℃ for rolling with a large relative reduction rate until the final rolling. The relative reduction rate of each pass of the 5th to 12th passes (i.e., the 5th to (n-2)th passes) is 16%, and the relative reduction rate of each pass of the 13th to 14th passes (i.e., the (n-1)th to nth passes) is 3%. After the reciprocating rolling is completed, the rolling is air-cooled to room temperature.
[0064] (3) Anneal the Cr12MoV rolled billet obtained in step (2) to obtain Cr12MoV flat steel;
[0065] The Cr12MoV rolled billets were stacked in an annealing furnace, heated from room temperature to 865℃ at 45℃ / h and held for 5.5h, then cooled to 300℃ at 75℃ / h and then the furnace door was opened for air cooling to room temperature.
[0066] The finished Cr12MoV flat steel has a thickness of 60mm and a height compression ratio of 2.5.
[0067] Example 2
[0068] A rolling method for Cr12MoV flat steel comprises the following steps:
[0069] (1) Cr12MoV continuous casting billet is continuously heated to obtain Cr12MoV ingot billet to be heated.
[0070] The dimensions of the continuously cast billet are: thickness 150mm, width 580mm, and length 3m.
[0071] The continuous heating process consists of preheating, first-stage heating, second-stage heating, and homogenization heating in sequence. The final temperature of the preheating stage is 581°C, and the time is 100 min. The final temperature of the first-stage heating stage is 1130°C, and the time is 80 min. The final temperature of the second-stage heating stage is 1133°C, and the time is 90 min. The holding temperature for homogenization heating is 1167°C, and the holding time is 35 min. The final temperature of the second-stage heating stage is 3°C higher than the final temperature of the first-stage heating stage.
[0072] The continuous heating equipment is a walking beam furnace with a total step length of 33m (the preheating step is 12m, and the step lengths for the first stage heating, second stage heating, and homogenization are 7m each).
[0073] (2) The Cr12MoV ingot obtained in step (1) is subjected to reciprocating rolling to obtain Cr12MoV rolled billet; wherein, before reciprocating rolling, high-pressure water dephosphorization is performed, and the water pressure for high-pressure water dephosphorization is 18MPa.
[0074] The initial rolling temperature during reciprocating rolling is 1120℃, and the total number of reciprocating rolling passes n is 16. The relative reduction rate of the first pass is 2%, the relative reduction rate of each pass from the 2nd to the 4th passes is 6%, and the surface temperature is raised to 973℃ for rolling with a large relative reduction rate until the final rolling. The relative reduction rate of each pass from the 5th to the 14th passes (i.e., the 5th to (n-2)th passes) is 17%, and the relative reduction rate of each pass from the 15th to the 16th passes (i.e., the (n-1)th to the nth passes) is 4%. After the reciprocating rolling is completed, the rolling is air-cooled to room temperature.
[0075] (3) Anneal the Cr12MoV rolled billet obtained in step (2) to obtain Cr12MoV flat steel;
[0076] The Cr12MoV rolled billets were stacked in an annealing furnace, heated from room temperature to 870℃ at a rate of 45℃ / h and held for 5 hours, then cooled to 300℃ at a rate of 71℃ / h and finally air-cooled to room temperature after the furnace door was opened.
[0077] The finished Cr12MoV flat steel has a thickness of 20mm and a height compression ratio of 7.5.
[0078] Comparative Example 1
[0079] The Cr12MoV continuous casting billet used in step (1) of Example 1 was taken as the sample of Comparative Example 1.
[0080] Comparative Example 2
[0081] The Cr12MoV continuous casting billet used in step (1) of Example 2 was taken as the sample of Comparative Example 2.
[0082] The Cr12MoV flat steels rolled in Examples 1 and 2 and the Cr12MoV continuous casting billets from Comparative Examples 1 and 2 were cut along their cross-sections. Based on the low-magnification microstructure and qualification level of flat steel in Table 29 of GB / T1299-2014, the porosity of the central microstructure was determined. The low-magnification photographs of the central microstructure of the samples used for determination were obtained from... Figures 1-4 As shown, the division results are shown in Table 1.
[0083] Depend on Figures 1-4 It can be seen that the central structure of the Cr12MoV flat steel rolled by the present invention is more compact than that of the Cr12MoV continuous casting billet in the comparative example, and the problems of porosity and voids have been significantly improved.
[0084] The Cr12MoV flat steels of Examples 1-2 and the Cr12MoV continuous casting billets of Comparative Examples 1-2 were classified according to the national standard GB / T14979-94, based on the carbide inhomogeneity levels at 1 / 4 of the cross-sectional angle of the samples. The optical micrographs of 1 / 4 of the cross-sectional angle used for classification were obtained from [the relevant sources]. Figures 5-8 As shown, the division results are shown in Table 1.
[0085] Depend on Figures 5-8 It can be seen that no coarse carbides appear at the 1 / 4 diagonal of the Cr12MoV flat steel rolled by the present invention, and the structure is uniform, indicating that the rolling method provided by the present invention can improve the problem of coarse and uneven carbides in Cr12MoV continuous casting billets.
[0086] Table 1. Levels of central tissue porosity and carbide inhomogeneity in samples from Examples 1-2 and Comparative Examples 1-2.
[0087] Central tissue looseness Level 1.5 Level 1.0 Level 2.5 Level 2.5 Carbide inhomogeneity at 1 / 4 diagonal Level 2.5 Level 1.0 Level 8.0 Level 8.0
[0088] As can be seen from Table 1, the Cr12MoV flat steel prepared by the rolling method provided by the present invention has a central porosity level ≤1.5 and a carbide inhomogeneity level ≤2.5, both of which are significantly lower than those of the Cr12MoV continuous casting billet. This indicates that the rolling method provided by the present invention can effectively improve the problems of central porosity in the Cr12MoV continuous casting billet and make the carbides uniformly distributed.
[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A rolling method for Cr12MoV flat steel, characterized in that, Includes the following steps: (1) Cr12MoV continuous casting billet is continuously heated to obtain Cr12MoV ingot billet to be heated. (2) The Cr12MoV ingot obtained in step (1) is subjected to reciprocating rolling to obtain Cr12MoV rolled billet; (3) Anneal the Cr12MoV rolled billet obtained in step (2) to obtain Cr12MoV flat steel; The continuous heating in step (1) includes preheating, first-stage heating, second-stage heating, and homogenization in sequence; the starting temperature of the preheating is room temperature, the final temperature of the preheating is 550~650℃, and the preheating time is 90~120min; the final temperatures of the first-stage heating and the second-stage heating are independently 1100~1150℃, the first-stage heating and the second-stage heating time are independently 60~90min, and the final temperature of the second-stage heating is 1~5℃ higher than the final temperature of the first-stage heating; the holding temperature of the homogenization is 1160~1190℃, and the holding time of the homogenization is 30~60min; In step (2), the total number of reciprocating rolling passes is n, where n = 10~16; during the reciprocating rolling, the relative reduction rate of the first pass is 2~5%, the relative reduction rate of each pass of the second to fourth passes is independently 6~10%, the relative reduction rate of each pass of the fifth to (n-2) passes is independently 15~20%, and the relative reduction rate of each pass of the (n-1) to nth passes is independently 2~5%; in step (2), the initial rolling temperature of the reciprocating rolling is 1080~1130℃, and the temperature from the fifth pass to the final rolling is independently 950~1000℃.
2. The rolling method as described in claim 1, characterized in that, Before reciprocating rolling in step (2), high-pressure water descaling is performed, and the water pressure for high-pressure water descaling is 17~19MPa.
3. The rolling method as described in claim 1, characterized in that, The cooling method after the reciprocating rolling in step (2) is air cooling to room temperature.
4. The rolling method as described in claim 1, characterized in that, The holding temperature for annealing in step (3) is 860~880℃, and the holding time for annealing is 5~6h.
5. The rolling method as described in claim 4, characterized in that, The cooling method for the annealing process is as follows: the temperature is reduced from the holding temperature of the annealing process to 300°C at a cooling rate of 70~80°C / h, and then air-cooled to room temperature.