CN108906884B - Low-temperature rolling production method of high-performance 20CrMnTi gear steel - Google Patents
Low-temperature rolling production method of high-performance 20CrMnTi gear steel Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
- B21B1/18—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section in a continuous process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0224—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for wire, rods, rounds, bars
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
- B21B45/08—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing hydraulically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2201/00—Special rolling modes
- B21B2201/02—Austenitic rolling
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Abstract
The invention belongs to the field of special steel production and processing in metallurgical industry, and relates to a low-temperature rolling production method of high-performance 20CrMnTi gear steel, which takes a 20CrMnTi continuous casting billet as a raw material and sequentially comprises the following working procedures: heating, descaling, rough rolling, continuous rolling, water cooling, fine rolling of a bar reducing and sizing unit and cooling by a cooling bed to finally obtain a finished bar. The low-temperature rolling production method of the high-performance 20CrMnTi gear steel optimizes the heating process system of the heating furnace, reduces the heating energy consumption, saves the production cost and protects the environment; the high-performance 20CrMnTi gear steel is obtained, the grain size control, the hardness control and the mechanical property control are all superior to those of the conventional rolling process, the metallographic structure of the gear steel is ferrite plus pearlite, the hardness body is generally 170-plus-220 HBW, the grain size of the gear steel is fine and uniform, the grain size of rolled round steel can reach at least 9.0 grade, and the comprehensive mechanical property of the gear steel is superior to that of the conventional rolling process.
Description
Technical Field
The invention belongs to the field of special steel production and processing in the metallurgical industry, relates to a rolling process, and particularly relates to a low-temperature rolling production method of high-performance 20CrMnTi gear steel.
Background
In recent years, with the rapid development of economy in China, automobile manufacturing industry and machinery manufacturing industry in China are rapidly developed, and under the background, the use amount and variety of gear steel are increased day by day, and the quality requirement on the gear steel is gradually improved. The 20CrMnTi gear steel has mechanical properties of good hardenability, excellent low-temperature impact toughness, good fatigue resistance and the like, and the 20CrMnTi gear steel is always the leading variety of the steel for gears in China and is widely applied to gears, shafts and piston parts in China.
The patent with the publication number of CN106755869A and the name of 'a method for producing Q550D steel plate with low energy consumption' introduces a method for cutting off a cast continuous casting slab, directly putting the cast continuous casting slab into a heating furnace for reheating, and carrying out controlled rolling on the heated continuous casting slab. The method adopts a hot charging and hot conveying technology to reduce heating energy consumption, but does not substantially reduce the heating temperature of a heating furnace, and the method aims at common carbon steel and is not suitable for the process production of gear steel.
The document "practice of cooling and rolling process of 1580mm production line of wu steel" (xuxi, li shi, tan, wu steel 1580mm production line cooling and rolling process practice [ J ] steel rolling, 2014,31 (1): 24-29) introduces the cooling and rolling practice that the hot rolling temperature of part of commercial materials and strip steel for cold rolling is reduced from 1250 ℃ to 1170 ℃ against the pressure of higher energy consumption and higher production cost caused by overhigh heating temperature in the existing heating temperature system. Although the process is optimized from the heating temperature system, the steel grade mainly aims at common carbon steel, and the process production of gear steel is not mentioned.
In the document 42CrMo alloy bar cooling rolling process research (Weiliqun, Liuruou, Chenhanhui, and the like 42CrMo alloy bar cooling rolling process research [ J ] steel, 2009,44 (9): 53-57) in combination with on-site actual measurement parameters and theoretical calculation models, the fact that the heating temperature of 42CrMo steel is reduced from 1150 ℃ to 1030 ℃ is demonstrated, and the influence on the force energy parameters of a rolling mill and a main motor is realized, so that the heating energy consumption is reduced. The paper specifically describes the rolling process of the bonded steel, but does not specifically teach the temperature control and heating time of the heating stages, and the steel type is common bonded steel, and is not mentioned for the process production of gear steel.
The prior art has the following defects for the 20CrMnTi rolling production method for reducing the heating energy consumption: most of steel enterprises have no change to the heating process of 20CrMnTi gear steel, and adopt high-temperature heating (furnace temperature 1220-.
Through literature search and patent inquiry, the low-temperature rolling production process of the gear steel is not mentioned at present. The main reasons for producing the gear steel by adopting high-temperature heating and high-temperature rolling but not adopting a low-temperature rolling production process in the technical field are as follows: (1) the high-temperature heating is beneficial to the plastic deformation of metal, the deformation resistance of the rolling mill is reduced, and the production stability of the rolling mill is improved; (2) the high-temperature heating is beneficial to the homogenization of austenite structures and the improvement of the grain size of the gear steel. The main difficulty of the low-temperature heating and low-temperature rolling technology is as follows: (1) the requirement on the deformation resistance of main rolling line rolling mill equipment is high, and a common rolling mill is relatively difficult to work; (2) the low-temperature rolling technology is a technology raised in metallurgical industry in recent years, has the advantage of improving the comprehensive mechanical property of materials, but at present, domestic steel manufacturers are still in the groping stage.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-performance 20CrMnTi low-temperature rolling production method for reducing heating energy consumption. The process method can be used for producing the 20CrMnTi gear steel with excellent comprehensive mechanical properties, and simultaneously greatly reduces the energy consumption of the heating furnace, thereby saving the production cost and protecting the natural environment.
In order to achieve the purpose, the invention adopts the following technical scheme:
a low-temperature rolling production method of high-performance 20CrMnTi gear steel takes a 20CrMnTi continuous casting billet as a raw material, and the production method sequentially comprises the following working procedures: heating, descaling, rough rolling, continuous rolling, water cooling, fine rolling of a bar reducing and sizing unit and cooling by a cooling bed to finally obtain a finished bar.
The invention adopts the technical principle of reducing heating energy consumption and producing the 20CrMnTi steel grade by low-temperature rolling, and comprises the following steps: according to the 20CrMnTi gear steel grade, TiN (N forms TiN nitride with Ti element in the high-temperature smelting process) has the grain refining effect, in the heating process, the high-temperature melting point of the TiN reaches above 1300 ℃, so the sufficient solid solution of the TiN can not be achieved through the high-temperature heating of the heating furnace, and therefore the cooling and heating process is adopted, the TiN also has the tendency of inhibiting the austenite grain size from growing, the TiN is dispersed and separated out in the rolling process and has the effect of preventing austenite from recrystallizing, meanwhile, through controlling the rolling and controlling the cooling technology, in the rolling process, the grain size can be nucleated on a grain boundary and can be nucleated on a deformation zone through plastic deformation, the grain size is more refined, the mechanical property of the material can be improved, the grain size grade of the material can also be improved, and the comprehensive performance of the material is excellent. Therefore, through the mechanism, the heating energy consumption is reduced, and 20CrMnTi steel grade is produced by low-temperature rolling, so that the heating energy consumption can be reduced, and the 20CrMnTi gear steel with excellent mechanical property can be produced.
In the above rolling production method, as a preferred embodiment, in the heating step, the continuous cast slab is heated, and the temperature of the soaking section is 1100 to 1150 ℃ (for example, 1105 ℃, 1110 ℃, 1115 ℃, 1120 ℃, 1125 ℃, 1130 ℃, 1135 ℃, 1140 ℃ and 1145 ℃), and the soaking time of the soaking section is 30 to 80min (for example, 32min, 35min, 40min, 45min, 50min, 55min, 60min, 70min, 75min and 78 min).
In order to further reduce energy consumption and improve heating quality, the heating process is preferably divided into four sections of heating, namely a preheating section, a first heating section, a second heating section and a soaking section; wherein the content of the first and second substances,
the temperature of the preheating section is less than or equal to 800 ℃ (such as 600 ℃, 700 ℃, 750 ℃, 780 ℃ and 795 ℃); if the temperature of the preheating section is too high, the heat conduction rate of the steel billet is too high, and further surface cracks of the final rolled material can be caused;
the temperature of the heating section is 1000-1050 ℃ (such as 1005 ℃, 1010 ℃, 1020 ℃, 1030 ℃, 1040 ℃, 1145 ℃);
the temperature of the second heating stage is 1050-1100 ℃ (such as 1055 ℃, 1060 ℃, 1070 ℃, 1080 ℃, 1090 ℃, 1095 ℃); the heating first section and the heating second section have the main functions that: energy consumption is reduced, and oxidation burning loss of the steel billet is reduced;
the temperature of the soaking section is 1100-1150 ℃ (such as 1105 ℃, 1110 ℃, 1115 ℃, 1120 ℃, 1125 ℃, 1130 ℃, 1135 ℃, 1140 ℃ and 1145 ℃); the main functions of the soaking section are as follows: the energy consumption is reduced, the oxidation burning loss of the steel billet is reduced, and the decarburization of the steel billet is reduced;
more preferably, the total heating time in the heating step is 3 to 5 hours (such as 3.2 hours, 3.5 hours, 4 hours, 4.5 hours, 4.8 hours), and the soaking time in the soaking section is 30 to 80min (such as 32min, 35min, 40min, 45min, 50min, 55min, 60min, 70min, 75min, 78 min); so that the following four goals can be more fully realized: (1) energy consumption is reduced; (2) the oxidation burning loss of the steel billet is reduced; (3) the decarburization of the steel billet is reduced; (4) the surface cracks of the final rolled material caused by overlong heating time are reduced; more preferably, the heating process is performed in a four-stage step furnace.
In the rolling production method, as a preferred embodiment, in the descaling step, scale is removed by descaling with high-pressure water at a pressure of 25 to 30MPa (for example, 25.5MPa, 26MPa, 26.5MPa, 27MPa, 28MPa, 28.5MPa, 29MPa, 29.5 MPa); preferably 28 to 30 MPa.
In the above rolling production method, as a preferred embodiment, in the rough rolling step, the inlet temperature is 980 to 1050 ℃ (for example, 985 ℃, 990 ℃, 1000 ℃, 1010 ℃, 1020 ℃, 1030 ℃, 1040 ℃, 1045 ℃), and the rough rolling pass is 5 to 7 passes; preferably, the roughing mill used in the roughing step has 6 stands in total, and the number of roughing passes is 6. The low-temperature rolling technology adopted in the rough rolling process is beneficial to improving the comprehensive mechanical property of the gear steel, and if the temperature is too high, the grain size of the gear steel grows too large, thus being not beneficial to improving the comprehensive mechanical property of the material.
In the rolling production method, as a preferred embodiment, the continuous rolling process comprises an intermediate rolling process and a pre-finish rolling process, the incoming material suitable for entering the bar reducing and sizing mill set is obtained after the continuous rolling, the inlet temperature of the intermediate rolling process is 900-950 ℃ (such as 905 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃ and 945 ℃), and the intermediate rolling pass is 5-7 passes; in the pre-rolling procedure, the pre-rolling pass is 3-5 passes, and the pre-rolling outlet temperature is 870-950 ℃ (such as 875 ℃, 880 ℃, 890 ℃, 900 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃ and 945 ℃); preferably, 6 middle rolling mills are arranged in the middle rolling process, 4 pre-finishing rolling mills are arranged in the pre-finishing rolling process, the middle rolling pass is 6 passes, and the pre-finishing rolling pass is 4 passes.
In the above rolling production method, as a preferred embodiment, in the water-through-cooling step, the continuously rolled incoming material is water-through-cooled to 700 to 750 ℃ (for example, 702 ℃, 705 ℃, 710 ℃, 720 ℃, 730 ℃, 740 ℃, 745 ℃, 748 ℃); the water cooling temperature is controlled within the range, a sufficient temperature return distance can be reserved for the rolled material, if the temperature is not controlled within the temperature range, the subsequent rolling temperature is possibly too high or too low, and the grain size, the comprehensive mechanical property and the hardness of the gear steel grade are adversely affected to a certain extent; preferably, the water cooling speed of the water cooling is 35-100 ℃/s (such as 38 ℃/s, 42 ℃/s, 45 ℃/s, 50 ℃/s, 55 ℃/s, 60 ℃/s, 70 ℃/s, 80 ℃/s, 90 ℃/s, 95 ℃/s, 98 ℃/s), and the water pressure is 0.2-0.6 MPa (such as 0.25MPa, 0.3MPa, 0.35MPa, 0.4MPa, 0.45MPa, 0.5MPa, 0.55 MPa). The water cooling process aims at reducing the rolling temperature, realizing low-temperature rolling and improving the structure and the comprehensive mechanical property of the bar.
In the above rolling production method, as a preferred embodiment, in the finish rolling step of the bar reducing and sizing mill set, the inlet temperature is 800 to 830 ℃ (for example, 802 ℃, 805 ℃, 810 ℃, 815 ℃, 820 ℃, 825 ℃, 828 ℃); preferably, the bar reducing and sizing mill group finish rolling is KOCKS rolling. The low-temperature rolling can be better implemented by adopting a bar reducing sizing mill set for finish rolling, so that the grain size and the comprehensive mechanical property of the gear steel grade are improved, the hardness is reduced, and the excellent performance is provided for the production of the gear steel.
In the above rolling production method, as a preferred embodiment, the specific method of the cooling bed step is: firstly, slowly cooling the bar obtained after the bar is finely rolled by the bar reducing sizing mill set to 600 ℃ in a cooling bed heat-insulating cover, and then taking out the bar from the heat-insulating cover for cooling in a cooling bed; the hardness value of the gear steel can be better controlled by adopting slow cooling in the cover, the subsequent annealing cost of heat treatment is reduced, the process flow is shortened, and the gear steel is energy-saving and environment-friendly; preferably, the cooling speed of the slow cooling is less than or equal to 15 ℃/min (such as 14 ℃/min, 13 ℃/min, 12 ℃/min, 10 ℃/min, 8 ℃/min, 5 ℃/min, 3 ℃/min, 2 ℃/min and 1 ℃/min), so that the cooling speed of the slow cooling in the cover is limited below 15 ℃/min, the main purpose is to control the gear steel hardness value, and if the cooling is too fast, the hardness value or the metallographic structure can not meet the requirements of users.
In the rolling production method, as a preferred embodiment, the specification of the finished bar is 50-100 mm.
Compared with the prior art, the invention has the beneficial effects that:
(1) the low-temperature rolling production method of the high-performance 20CrMnTi gear steel optimizes the heating process system of the heating furnace, reduces the heating energy consumption, saves the production cost and protects the environment;
(2) the high-performance 20CrMnTi gear steel is obtained by an online low-temperature rolling technology, the grain size control, the hardness control and the mechanical property control of the gear steel are all superior to those of the conventional rolling technology, specifically, the metallographic structure of the gear steel is ferrite plus pearlite, the hardness body is generally 170 plus 220HBW, the grain size of the gear steel is fine and uniform, the grain size of the rolled round steel can reach at least 9.0 grade, and the comprehensive mechanical property of the gear steel is superior to that of the conventional rolling technology.
Drawings
FIG. 1 is a photograph of the metallographic structure of a 20CrMnTi steel grade rolled in example 1 of the present invention;
FIG. 2 is a grain size photograph of 20CrMnTi steel grade rolled in example 1 of the present invention;
FIG. 3 is a photograph of the metallographic structure of 20CrMnTi steel rolled in example 2 of the present invention;
FIG. 4 is a grain size photograph of 20CrMnTi steel grade rolled in example 2 of the present invention.
Detailed Description
The technical solution of the present invention is further described in detail by way of example with reference to the accompanying drawings.
The 20CrMnTi material prepared by the invention comprises the following chemical components in percentage by mass: c: 0.17 to 0.23; si: 0.17 to 0.37; mn: 0.80 to 1.10; cr: 1.00 to 1.30; ti: 0.04 to 0.10; p is less than or equal to 0.025; s is less than or equal to 0.020; al: 0.02 to 0.05; n is 0.0040-0.0060; the balance of Fe, the mass fraction is 100%. Chromium and manganese in the material are main additive elements of 20CrMnTi steel, and play roles in improving the body strength and enhancing the hardenability; the addition of titanium enables the crystal grains in the steel to be refined, can prevent the crystal grains from growing during carburization and improves the strength and the toughness of the steel; and N and Ti element form TiN nitride in the high-temperature smelting process.
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel takes a 20CrMnTi continuous casting billet as a raw material, and the raw material continuous casting billet is obtained through conventional smelting, refining and continuous casting processes, and is not described in detail herein.
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel sequentially comprises the following working procedures: heating, descaling, rough rolling, continuous rolling, water cooling, fine rolling of a bar reducing and sizing unit and cooling by a cooling bed to finally obtain a finished bar. The rolling method comprises the following specific steps:
(1) heating a steel billet: the heating procedure is carried out in a four-section stepping heating furnace, and the temperature of a preheating section is less than or equal to 800 ℃; the temperature of the first heating section is 1000-1050 ℃; the temperature of the second heating section is 1050-1100 ℃; the temperature of the soaking section is 1100-1150 ℃; further preferably, the total heating time (i.e. the time from charging to discharging) in the heating procedure is 3-5 h, and the soaking time of the soaking section is 30-80 min;
(2) descaling a steel billet: descaling the heated steel billet by adopting high-pressure water to remove iron scales, wherein the pressure of the high-pressure water is 25-30 MPa; preferably 28 to 30 MPa.
(3) Rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill 6 frames for roughing to obtain rough rolling billets; the preferred inlet temperature is 980-1050 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the temperature of a middle rolling inlet is 900-950 ℃, the middle rolling pass is 6 passes, and the pre-finish rolling pass is 4 passes.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; preferably, the water cooling is carried out to cool the temperature to 700-750 ℃; preferably, the water cooling speed of the through water cooling is 35-100 ℃/s, and the water pressure is 0.2-0.6 MPa. The rolled stock was red back after water cooling to obtain the temperature for KOCKS rolling.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material obtained in the step (5) to obtain a bar material; preferably, the inlet temperature of the KOCKS rolling is 800-830 ℃.
(7) Cooling by a cooling bed: slowly cooling the bar material to 600 ℃ in a cooling bed heat-insulating cover, and then taking the bar material out of the heat-insulating cover for cooling in a cooling bed; preferably, the cooling speed of the slow cooling is less than or equal to 15 ℃/min.
Example 1
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the embodiment needs the specification of the finished 20CrMnTi steel grade to be 50mm, and comprises the following steps:
(1) heating a steel billet: cutting off a 300X 400X 9000mm continuous casting billet, and then putting the continuous casting billet into a four-section stepping heating furnace in a cold delivery mode for reheating, wherein the continuous casting billet comprises the following components in percentage by mass: c: 0.191; si: 0.184; mn: 1.005; cr: 1.024; ti: 0.057; p: 0.015; s: 0.012; al: 0.023; n: 0.0055; the balance of Fe, the mass fraction is 100%;
the temperature of the preheating section is 660 ℃, the temperature of the heating section is 1025 ℃, the temperature of the heating section is 1080 ℃, and the temperature of the soaking section is 1128 ℃; the total heating time in the heating procedure is 3.5h, and the soaking time of the soaking section is 55 min;
(2) descaling a steel billet: descaling the heated billet by adopting high-pressure water to remove scale, wherein the pressure of the high-pressure water is 30 MPa;
(3) rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill (6 stands) for roughing rolling to obtain roughing rolling billets; the inlet temperature of rough rolling is 1020 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the inlet temperature of intermediate rolling is 930 ℃, the intermediate rolling pass is 6 passes, the outlet temperature of pre-finish rolling is 900 ℃, and the pre-finish rolling pass is 4 passes.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 735 ℃; the water cooling speed is 60 ℃/s, and the water pressure is 0.4 MPa.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material with the specification of 70mm obtained after the pre-finish rolling to obtain a bar material with the specification of 50 mm; the inlet temperature for the KOCKS rolling was 820 ℃.
(7) Cooling by a cooling bed: and (4) slowly cooling the bar material with the specification of 50mm obtained in the step (6) to 600 ℃ in a cooling bed heat-insulating cover at a cooling speed of 10 ℃/min, taking out the bar material from the heat-insulating cover, and carrying out cooling in a cooling bed to finally obtain a finished bar material.
Under the rolling production process, the 20CrMnTi hot rolling structure is ferrite plus pearlite (see figures 1 and 2), and the mechanical properties of the bar products are shown in Table 1.
Table 1 mechanical properties of the product prepared in example 1
Example 2
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the embodiment has the specification of the required finished 20CrMnTi steel grade of 80mm, and comprises the following steps:
(1) heating a steel billet: cutting a 300X 400X 9000mm continuous casting billet, and then putting the continuous casting billet into a heating furnace in a red delivery mode for reheating, wherein the continuous casting billet comprises the following components in percentage by mass: c: 0.195; si: 0.219; mn: 1.041; cr: 1.103; ti: 0.049; p: 0.012; s: 0.008; al: 0.034; n: 0.0050; the balance of Fe, the mass fraction is 100%;
the temperature of the preheating section is 620 ℃; heating to a first temperature of 1030 ℃; the temperature of the heating second section is 1065 ℃; the temperature of the soaking section is 1135 ℃; the total heating time in the heating procedure is 4.0h, and the soaking time in the soaking section is 62 min;
(2) descaling a steel billet: descaling the heated billet by adopting high-pressure water to remove scale, wherein the pressure of the high-pressure water is 29.5 MPa;
(3) rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill (6 stands) for roughing rolling to obtain rough rolling billets; the rough rolling inlet temperature is 1015 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the inlet temperature of intermediate rolling is 925 ℃, the intermediate rolling pass is 6 passes, the outlet temperature of pre-finish rolling is 880 ℃, and the pre-finish rolling pass is 4 passes.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 720 ℃; the water cooling speed is 55 ℃/s, and the water pressure is 0.35 MPa.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material with the specification of 95mm obtained after the pre-finish rolling to obtain a bar material with the specification of 80 mm; the inlet temperature for the KOCKS rolling was 812 ℃.
(7) Cooling by a cooling bed: and (4) slowly cooling the bar with the specification of 80mm obtained in the step (6) to 600 ℃ in a cooling bed heat-insulating cover at a cooling speed of 7 ℃/min, taking out the bar from the heat-insulating cover, and carrying out cooling in a cooling bed to finally obtain a finished bar.
Under the rolling production process, the 20CrMnTi hot rolling structure is ferrite plus pearlite (see figures 3 and 4), and the mechanical properties of the bar products are shown in Table 2.
Table 2 mechanical properties of the product prepared in example 2
Example 3
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the embodiment needs the specification of the finished 20CrMnTi steel grade to be 100mm, and comprises the following steps:
(1) heating a steel billet: cutting off a 300X 400X 9000mm continuous casting billet, and then putting the continuous casting billet into a heating furnace in a cold delivery mode for reheating, wherein the continuous casting billet comprises the following components in percentage by mass: c: 0.201; si: 0.196 parts of; mn: 1.025; cr: 1.054, respectively; ti: 0.068; p: 0.020; s: 0.006; al: 0.033; n: 0.0048; the balance of Fe, the mass fraction is 100%;
the temperature of the preheating section is 680 ℃; heating at a first temperature of 1040 ℃; the temperature of the second heating section is 1085 ℃; the temperature of the soaking section is 1125 ℃; the total heating time in the heating procedure is 4.2h, and the soaking time in the soaking section is 60 min;
(2) descaling a steel billet: descaling the heated billet by adopting high-pressure water to remove scale, wherein the pressure of the high-pressure water is 29.5 MPa;
(3) rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill 6 frames for roughing to obtain rough rolling billets; the inlet temperature of rough rolling is 1020 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the temperature of a middle rolling inlet is 925 ℃, the middle rolling pass is 6 passes, the temperature of a pre-finish rolling outlet is 870 ℃, and the pre-finish rolling pass is 4 passes.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 725 ℃; the water cooling speed is 45 ℃/s, and the water pressure is 0.40 MPa.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material with the specification of 125mm obtained after the pre-finish rolling to obtain a bar material with the specification of 100 mm; the inlet temperature for the KOCKS rolling was 807 ℃.
(7) Cooling by a cooling bed: and (4) slowly cooling the bar material with the specification of 100mm obtained in the step (6) to 600 ℃ in a cooling bed heat-insulating cover at a cooling speed of 6 ℃/min, taking out the bar material from the heat-insulating cover, and carrying out cooling in a cooling bed to finally obtain the finished bar material.
Under the rolling production process, the 20CrMnTi hot rolling structure is ferrite plus pearlite, and the mechanical properties of the bar products are shown in Table 3.
Table 3 mechanical properties of the product prepared in example 3
Example 4
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the embodiment has the specification of the required finished 20CrMnTi steel grade of 70mm, and comprises the following steps:
(1) heating a steel billet: cutting off a 300X 400X 9000mm continuous casting billet, and then putting the continuous casting billet into a heating furnace in a cold delivery mode for reheating, wherein the continuous casting billet comprises the following components in percentage by mass: c: 0.201; si: 0.196 parts of; mn: 1.025; cr: 1.054, respectively; ti: 0.068; p: 0.020; s: 0.006; al: 0.033; n: 0.0057; the balance of Fe, the mass fraction is 100%;
the temperature of the preheating section is 780 ℃; heating to 1050 ℃ for a first period; the temperature of the second heating section is 1100 ℃; the temperature of the soaking section is 1145 ℃; the total heating time in the heating procedure is 4.8h, and the soaking time in the soaking section is 80 min;
(2) descaling a steel billet: descaling the heated billet by adopting high-pressure water to remove scale, wherein the pressure of the high-pressure water is 27 MPa;
(3) rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill 6 frames for roughing to obtain rough rolling billets; the inlet temperature of rough rolling is 1045 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the inlet temperature of medium rolling is 945 ℃, the medium rolling pass is 6 passes, the outlet temperature of pre-finish rolling is 885 ℃, and the pre-finish rolling pass is 4 passes.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 745 deg.C; the water cooling speed is 75 ℃/s, and the water pressure is 0.55 MPa.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material with the specification of 95mm obtained after the pre-finish rolling to obtain a bar material with the specification of 70 mm; the inlet temperature for the KOCKS rolling was 828 ℃.
(7) Cooling by a cooling bed: and (4) slowly cooling the bar with the specification of 70mm obtained in the step (6) to 600 ℃ in a cooling bed heat-insulating cover at a cooling speed of 15 ℃/min, taking out the bar from the heat-insulating cover, and carrying out cooling in a cooling bed to finally obtain a finished bar.
Under the rolling production process, the 20CrMnTi hot rolling structure is ferrite plus pearlite, and the mechanical properties of the bar products are shown in Table 4.
Table 4 mechanical properties of the product prepared in example 4
Example 5
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the embodiment needs the specification of the finished 20CrMnTi steel grade to be 60mm, and comprises the following steps:
(1) heating a steel billet: cutting a 300X 400X 9000mm continuous casting billet, and then putting the continuous casting billet into a heating furnace in a red delivery mode for reheating, wherein the continuous casting billet comprises the following components in percentage by mass: c: 0.191; si: 0.184; mn: 1.005; cr: 1.024; ti: 0.057; p: 0.015; s: 0.012; al: 0.023; n: 0.0052; the balance of Fe, the mass fraction is 100%;
the temperature of the preheating section is 600 ℃, and the temperature of the heating section is 1000 ℃; the temperature of the second heating section is 1050 ℃, and the temperature of the soaking section is 1110 ℃; the total heating time in the heating procedure is 3h, and the soaking time of the soaking section is 40 min;
(2) descaling a steel billet: descaling the heated billet by adopting high-pressure water to remove scale, wherein the pressure of the high-pressure water is 26 MPa;
(3) rough rolling of a steel billet: sending the descaled steel billets into a high-rigidity roughing mill (6 stands) for roughing rolling to obtain roughing rolling billets; the inlet temperature of rough rolling is 985 ℃, and the rough rolling pass is 6.
(4) Continuous rolling by a continuous rolling unit: and (4) sending the rough rolling blank obtained in the step (3) into a continuous rolling unit, wherein the inlet temperature of medium rolling is 905 ℃, the pass of medium rolling is 6, the outlet temperature of pre-finish rolling is 945 ℃, and the pass of pre-finish rolling is 6.
(5) Cooling through water: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 700 ℃; the water cooling speed is 80 ℃/s, and the water pressure is 0.5 MPa.
(6) And (3) KOCKS rolling: performing KOCKS rolling on the rolled material with the specification of 75mm obtained after the pre-finish rolling to obtain a bar material with the specification of 60 mm; the inlet temperature for the KOCKS rolling was 825 ℃.
(7) Cooling by a cooling bed: and (4) slowly cooling the bar material with the specification of 60mm obtained in the step (6) to 600 ℃ in a cooling bed heat-insulating cover at a cooling speed of 12 ℃/min, taking out the bar material from the heat-insulating cover, and carrying out cooling in a cooling bed to finally obtain the finished bar material.
Under the rolling production process, the 20CrMnTi hot rolling structure is ferrite plus pearlite, and the mechanical properties of the bar products are shown in Table 5.
Table 5 mechanical properties of the product prepared in example 5
Example 6
In this example, the process conditions were the same as those in example 1 except that the heating schedule of the billet was different from that in example 1. In this example, the heating schedule of the billet in the step (1) is shown in table 6; the 20CrMnTi hot rolling structure of the finished bar is ferrite plus pearlite, and the mechanical properties of the bar product are shown in Table 7.
TABLE 6 Steel billet heating schedule in example 6
Table 7 properties of the product prepared in example 6
Example 7
In this example, the process conditions were the same as in example 1 except that the water cooling system was different from that in example 1. In this embodiment, the water cooling system in step (5) is as follows: carrying out water cooling on the rolled material subjected to pre-finish rolling; cooling to 765 deg.C; the water cooling speed is 30 ℃/s, and the water pressure is 0.20 MPa;
the 20CrMnTi hot rolling structure of the finished bar of the embodiment is ferrite plus pearlite, and the mechanical properties of the bar product are shown in Table 8.
Table 8 mechanical properties of the product prepared in example 7
Example 8
In this example, the process conditions were the same as those in example 1 except that the KOCKS rolling schedule was different from that in example 1. The KOCKS rolling schedule of step (6) in this example is shown in table 9.
TABLE 9 KOCKS Rolling schedule of example 8
| Entry temperature for KOCKS rolling | |
| Example 8-1 | 790℃ |
| Example 8 to 2 | 840℃ |
The finished bar 20CrMnTi obtained in this example has a hot-rolled structure of ferrite + pearlite, and the mechanical properties of the bar product are shown in Table 10.
TABLE 10 mechanical Properties of the product of example 8
While the preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art. Therefore, the appended claims should be construed to include preferred embodiments and all such variations and modifications as fall within the scope of the invention.
The low-temperature rolling production method of the high-performance 20CrMnTi gear steel provided by the invention is unique, and the production method can be used for producing the 20CrMnTi gear steel with excellent comprehensive mechanical properties, and simultaneously greatly reduces the energy consumption of a heating furnace, thereby saving the production cost and protecting the natural environment.
Claims (14)
1. The low-temperature rolling production method of the high-performance 20CrMnTi gear steel is characterized in that a 20CrMnTi continuous casting blank is used as a raw material, and the production method sequentially comprises the following working procedures: heating, descaling, rough rolling, continuous rolling, water cooling, fine rolling of a bar reducing and sizing unit and cooling by a cooling bed to finally obtain a finished bar;
in the heating procedure, four sections of heating are divided into a preheating section, a heating section and a soaking section in sequence; wherein the content of the first and second substances,
the temperature of the preheating section is less than or equal to 800 ℃;
the temperature of the first heating section is 1000-1050 ℃;
the temperature of the second heating section is 1050-1100 ℃;
the temperature of the soaking section is 1100-1150 ℃;
in the rough rolling procedure, the inlet temperature is 980-1045 ℃, and the rough rolling pass is 5-7;
in the finish rolling process of the bar reducing and sizing unit, the inlet temperature is 800-828 ℃.
2. The rolling production method according to claim 1, wherein the total heating time in the heating step is 3 to 5 hours, and the soaking time in the soaking section is 30 to 80 min.
3. The rolling production method according to claim 2, wherein the heating step is performed in a four-stage step furnace.
4. The rolling production method according to claim 1, wherein in the descaling step, scale is removed by using high-pressure water, and the pressure of the high-pressure water is 25 to 30 MPa.
5. The rolling production method according to claim 4, wherein the pressure of the high-pressure water is 28 to 30 MPa.
6. The rolling production method according to claim 1, wherein the roughing mill used in the roughing step has 6 stands in total, and the number of roughing passes is 6.
7. The rolling production method according to claim 1, wherein the continuous rolling process comprises an intermediate rolling process and a pre-finish rolling process, incoming materials suitable for entering the bar material reducing and sizing mill set are obtained after continuous rolling, the inlet temperature of the intermediate rolling process is 900-950 ℃, and the intermediate rolling pass is 5-7; in the pre-finish rolling procedure, the pre-finish rolling pass is 3-5 passes, and the pre-finish rolling outlet temperature is 870-950 ℃.
8. The rolling production method according to claim 7, wherein 6 intermediate rolling mills are provided in the intermediate rolling step, 4 pre-finishing rolling mills are provided in the pre-finishing rolling step, the intermediate pass is 6 passes, and the pre-finishing pass is 4 passes.
9. The rolling production method according to claim 1, wherein in the water-through cooling step, the incoming material after the continuous rolling is water-through cooled to 700 to 750 ℃.
10. The rolling production method according to claim 9, wherein the water cooling rate of the through-water cooling is 35-100 ℃/s, and the water pressure is 0.2-0.6 MPa.
11. The rolling production method of claim 1, wherein the bar reducing and sizing mill finish rolling is KOCKS rolling.
12. The rolling production method according to claim 1, wherein the specific method of the cooling bed cooling process is: firstly, slowly cooling the bar obtained after the bar is finely rolled by the bar reducing sizing mill set to 600 ℃ in a cooling bed heat-insulating cover, and then taking out the bar from the heat-insulating cover for cooling in a cooling bed.
13. The rolling production method according to claim 12, wherein the cooling rate of the slow cooling is 15 ℃/min or less.
14. The rolling production method of claim 1, wherein the finished bar has a gauge of 50-100 mm.
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