CN103331308B - Energy-saving carbon manganese steel rolling method based on critical temperature - Google Patents

Abstract

The energy-saving rolling method of carbon-manganese steel based on critical temperature designed by the present invention includes preheating the carbon-manganese steel slab through the heating furnace, heating the heating furnace, soaking the heating furnace, descaling before rough rolling, Steps of rough rolling, finish rolling, laminar cooling and coiling process. The preheating time of carbon-manganese steel slab is 50-100min, the temperature is 800-1000℃; the heating time is 40-70min, the temperature is 1150-1220℃; the soaking time is 20-40min, the temperature is 1140-1180℃; The outlet temperature is 1000~1050℃; the finish rolling inlet temperature is 980~1020℃, the finish rolling outlet temperature is 850~880℃; the coiling temperature is 620~680℃. The invention can not only ensure good structure and mechanical property level of the carbon-manganese steel slab, but also effectively reduce heating energy consumption.

Description

Energy-saving rolling method of carbon-manganese steel based on critical temperature

technical field

The invention relates to the technical field of hot-rolled strip production, in particular to an energy-saving rolling method for carbon-manganese steel based on a critical temperature.

technical background

In the hot rolling production process, billet heating energy consumption generally accounts for 70% to 80% of process energy consumption, and energy consumption for rolling only accounts for 20% to 30%. Therefore, the potential to reduce hot rolling energy consumption mainly comes from heating. Furnace energy consumption. In the existing production process of hot-rolled strip steel, before rolling the billet, the raw material should be heated to improve the plasticity of the steel, reduce the deformation resistance and improve the internal structure and performance of the metal, so as to facilitate the rolling process. However, high temperature and incorrect heating system may cause strong oxidation, decarburization, over-burning and other defects of steel, reduce the quality of steel, and even lead to waste products. Therefore, the heating temperature of the steel should be determined according to the characteristics of various steels and the requirements of the rolling process to ensure the quality and output of the steel.

In the actual production process, the temperature of the strip steel is measured by the infrared thermometer distributed on the rolling line, which can accurately measure the temperature of the heating furnace (RH), the exit temperature of the rough rolling (RT), and the entrance temperature of the finishing rolling (FT0 ), finishing rolling temperature (FT7), and coiling temperature (CT), these temperature points constitute the online actual temperature history of hot continuous strip steel, and the online actual process temperature is significantly higher than various critical temperatures, such as hot embrittlement temperature, Solution temperature, precipitation temperature, phase transition temperature, descaling temperature, starting rolling temperature and coiling temperature, etc. The critical temperature is the lowest allowable temperature in each link of the production process. Excessively high actual process temperature will cause excess heating temperature and excess capacity of rolling mill equipment.

In the existing production technology of hot-rolled strips, there are also related reports on reducing the heating temperature. For example, the document "Huang Chuanqing, Chen Jianrong, etc., Baosteel 2050mm Hot Continuous Rolling Low-temperature Rolling Technology Application Brief Analysis, "Baosteel Technology" introduces the application of Baosteel's low-temperature rolling technology, which reduces the heating temperature to 1200 °C and optimizes the rough rolling process. Rolling procedures and descaling passes, adding measures such as descaling water retaining chains, reduce the temperature drop in the rough rolling stage, and ensure the entrance temperature of the finish rolling. However, in this low-temperature rolling method, although the heating temperature is lower than the original conventional heating temperature of 1250°C, the heating temperature is mainly considered, and the overall and systematic consideration of the entire rolling process is not considered. The Chinese patent "Warm Rolling Method" with the patent number CN200480013648.7 introduces a new type of multi-directional warm rolling method, which is mainly used for rolling rods and wires to manufacture ultrafine grain structures with an average particle size of less than 3 μm. For grain steel, pass rolling is carried out at a temperature range of 350°C to 800°C. The Chinese patent "Warm Rolling Method for Threaded Steel Bars" with the patent number CN94105678.2 also proposes a production method for warm-rolling threaded steel bars by using the waste heat after hot rolling, and cooling the hot-rolled steel to 600°C on a cooling bed ~300°C, the steel is sent to the rough rolling mill by the heat preservation device for rolling, and the rolled wire rod is then subjected to finish rolling, reducing and engraving. The above two patents are mainly used in the production of wire and bar, and only consider the temperature of the rolling process, and also do not make a global and systematic consideration of the low temperature rolling of the whole rolling process.

In addition, the Chinese patent No. CN201010607955.5 "A Method for Temperature-Controlled Rolling of Q345 Steel Plate" proposed that the Q345 steel slab should be rolled out of the furnace in the preheating section, heating section, and soaking section in the pusher type heating furnace. Remove the iron scale, carry out the first-stage rolling at 1000°C~1050°C, air-cool or water-cool and wait until the temperature reaches 900°C-950°C for the second-stage rolling. This rolling method still adopts the idea of controlled rolling and air-cooling process to ensure the mechanical properties of Q345 steel plate. It does not adopt the idea of critical temperature, nor does it consider the heating temperature and energy saving in the entire rolling process. Therefore, it is also a non-systematic and localized steel rolling production process.

In summary, the existing production methods of hot-rolled strips are mainly conventional high-temperature heating and then rolling. There are also attempts to lower the heating temperature in consideration of reducing energy consumption, but they are all based on heating, or Each isolated point in the steel rolling process such as rolling is considered. The effect is not very obvious.

Contents of the invention

The purpose of the present invention is to provide a carbon-manganese steel energy-saving rolling method based on the critical temperature. This rolling method proposes a systematic and overall low-temperature rolling production method aimed at the characteristics of carbon-manganese steel, which can ensure The carbon-manganese steel has good structure and mechanical properties after rolling, and can effectively reduce heating energy consumption and production costs.

In order to achieve this goal, the energy-saving rolling method of carbon-manganese steel based on the critical temperature designed by the present invention includes preheating the carbon-manganese steel slab through the heating furnace, heating the heating furnace, soaking the heating furnace, and pre-rough rolling. The steps of descaling, rough rolling, finish rolling, laminar cooling and coiling process are characterized by:

The preheating time of the carbon-manganese steel slab during the preheating treatment in the heating furnace is 50-100min, and the preheating temperature is 800-1000°C;

The heating time of the carbon-manganese steel slab during the heating furnace heating treatment is 40-70min, and the heating temperature is 1150-1220°C;

The soaking time of the carbon-manganese steel slab during the soaking treatment in the heating furnace is 20-40min, and the soaking temperature is 1140-1180°C;

The rough rolling outlet temperature of the carbon-manganese steel slab during rough rolling is 1000-1050°C;

The finish rolling inlet temperature of the carbon-manganese steel slab during finish rolling is 980-1020°C, and the finish-rolling outlet temperature is 850-880°C;

The temperature of the carbon-manganese steel slab during coiling is 620-680°C.

Further, the chemical composition of the carbon-manganese steel slab is C: 0.01-0.08%, Si: 0.01-0.20%, Mn: 0.01-0.5%, S≤0.030%, P≤0.030%, and the rest For iron and unavoidable impurities.

Further, the air-fuel ratio of the carbon-manganese steel slab during preheating treatment in the heating furnace is 1.0-1.2; the air-fuel ratio of the carbon-manganese steel slab during heating treatment in the heating furnace is 0.9-1.1; the carbon-manganese steel slab The air-fuel ratio is 1.0~1.4 during the soaking treatment in the heating furnace.

Further, the total furnace time of the carbon-manganese steel slab in the heating furnace is 150 minutes to 180 minutes.

Further, the furnace pressure of the heating furnace is 10-25Pa.

Further, the number of descaling passes in the descaling process before rough rolling is 4 to 8 passes.

Furthermore, the rolling speed of the carbon-manganese steel slab during finish rolling is 5.5m/s-14m/s.

In the present invention, when rolling carbon-manganese steel slabs, the rolling temperature history is between the conventional rolling temperature history and the rolling critical temperature, and is considered systematically on the basis of being closer to the rolling critical temperature curve. At the same time, the above-mentioned rolling method proposed by the present invention is different from the second-generation TMCP (Thermo Mechanical Control Process) technology aimed at fine-grain rolling under low temperature and high pressure. This technology does not reduce the heating temperature , but in the finish rolling section, a large reduction at a lower temperature is used to refine the crystal grains, but in the present invention, the temperature of the finish rolling section is lower than that of conventional rolling due to the lowering of the heating temperature, and the reduction is not greatly adjusted. In addition, the present invention is different from the low-temperature ferrite rolling technology studied at home and abroad. When rolling the hot-rolled strips of carbon-manganese steel slabs, it is still rolled in the single-phase austenite zone, which reduces the heating temperature and other processes. The temperature has achieved the technical effect of reducing the energy consumption of the heating furnace. Moreover, the structure of the rolled hot-rolled strip is still ferrite+pearlite, and the mechanical properties are good.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

In the rolling process of conventional hot-rolled strips, only issues such as deformation reduction and equipment safety are considered, and the heating temperature and rolling process temperature are generally high. Therefore, in the actual hot-rolled strip production process, the capacity utilization rate of the rolling mill equipment is not high, and due to the high heating temperature, the energy consumption of the slab during the heating process of the heating furnace is relatively high. The present invention proposes an energy-saving rolling method of carbon-manganese steel based on the critical temperature. On the basis of ensuring the original mechanical properties of the carbon-manganese steel, the method calculates and verifies the critical temperature of the carbon-manganese steel in the required rolling process , and formulate the rolling method of carbon-manganese steel on the basis of the critical temperature. The critical temperature of carbon-manganese steel rolling process is determined by the following formula:

RH=Max[T (hot brittle), T (C solid solution), T (Mn solid solution), T (descaled)]

RT=Max[T (power of roughing mill), T (bite of rolling mill), T (FT0+ΔT temperature drop during transportation + ΔT descaling temperature drop)]

FT0=Max[T(FT7+ΔT temperature drop during rolling), T(finishing mill capacity), T(recrystallization fraction)]

FT7=T(Ar3)

CT=T (phase transition temperature)

In the above formula: T is the temperature, RH is the critical heating temperature in the soaking section, RT is the critical exit temperature of rough rolling, FT0 is the critical entrance temperature of finishing rolling, FT7 is the critical exit temperature of finishing rolling, and CT is the critical coiling temperature. T (hot brittleness) represents the hot brittleness temperature of the hot brittle slab, and the slab is easier to break at this temperature; T (roughing mill force) represents the temperature under the rolling force and power of the roughing mill rolling process; T( The bite of the rolling mill) represents the temperature required for the rolling mill to bite into the slab; the temperature drop during transportation represents the temperature loss of the rough rolling to the finishing rolling slab on the roller table; T (recrystallization fraction) represents the temperature loss after the controlled rolling The temperature required for microstructure and mechanical properties; T (phase transition temperature) represents the temperature point at which low carbon steel undergoes phase transition. T(C solid solution) represents the temperature required for C solid solution, T(Mn solid solution) represents the temperature required for Mn solid solution, T(descale) represents the heating temperature required to achieve a good descaling effect, and ΔT descaling temperature drop represents The temperature drop caused by high pressure water descaling, T(Ar3) represents the austenite transformation temperature.

The energy-saving rolling method of carbon-manganese steel based on the critical temperature designed by the present invention includes preheating the carbon-manganese steel slab through the heating furnace, heating the heating furnace, soaking the heating furnace, descaling before rough rolling, rough rolling, The steps of finish rolling, laminar cooling and coiling process, characterized by:

The preheating time of the carbon-manganese steel slab during the preheating treatment in the heating furnace is 50-100min, and the preheating temperature is 800-1000°C;

The heating time of the carbon-manganese steel slab during the heating furnace heating treatment is 40-70min, and the heating temperature is 1150-1220°C;

The soaking time of the carbon-manganese steel slab during the soaking treatment in the heating furnace is 20-40min, and the soaking temperature is 1140-1180°C;

The rough rolling outlet temperature of the carbon-manganese steel slab during rough rolling is 1000-1050°C;

The finish rolling entrance temperature of the carbon-manganese steel slab during finish rolling is 980~1020°C, and the finish rolling exit temperature is 850~880°C; the finish rolling entrance basically remains unchanged or slightly reduce;

The temperature of the carbon-manganese steel slab during coiling is 620-680°C.

In the above technical scheme, during the low-temperature rolling process of carbon-manganese steel slabs, due to the reduction of deformation temperature, the mechanical properties of the strip will be improved to a certain extent; at the same time, considering that the low-temperature process will cause difficulties in descaling, so in the comprehensive mechanics The chemical composition of carbon-manganese steel slabs is specified as follows on the basis of properties and surface quality. The chemical composition of the carbon-manganese steel slab is C: 0.01-0.08%, Si: 0.01-0.20%, Mn: 0.01-0.5%, S≤0.030%, P≤0.030%, and the rest is iron and unavoidable impurities.

In the above technical solution, the air-fuel ratio of the carbon-manganese steel slab during preheating treatment in the heating furnace is 1.0-1.2; the air-fuel ratio of the carbon-manganese steel slab during heating treatment in the heating furnace is 0.9-1.1; The air-fuel ratio of the steel slab is 1.0~1.4 when soaking in the heating furnace.

In the above technical solution, the total furnace time of the carbon-manganese steel slab in the heating furnace is 150 minutes to 180 minutes.

In the above technical solution, the furnace inner pressure of the heating furnace is a slight positive pressure of 10-25 Pa, which prevents the heating furnace from inhaling cold wind.

In the above technical solution, the number of descaling passes in the descaling process before rough rolling is 4-8. During the rough rolling process, it is necessary to ensure the surface quality of the carbon-manganese steel slab, and use a heat preservation cover to reduce the temperature drop during the rough rolling process.

In the above technical solution, the rolling speed of the carbon-manganese steel slab during finish rolling is 5.5m/s-14m/s. By increasing the rolling speed, it is ensured that the finish rolling exit temperature and coiling temperature remain unchanged in the original conventional hot rolling process,

In the above technical solution, the edge shielding technology is adopted during the laminar flow cooling process of the carbon-manganese steel slab to reduce the edge temperature drop of the hot-rolled strip during the cooling process.

Example 1

According to the requirements of the present invention, the carbon-manganese steel slabs of low-carbon and low-manganese steel components have been rolled and produced, and the production conditions of 3 carbon-manganese steel slabs are selected for illustration. The chemical composition of the carbon-manganese steel slabs is shown in Table 1. The process temperature is shown in Table 2.

Table 1 Smelting composition

Table 2 Example 1 rolling process temperature

The total furnace time of the slab 1 during the heating process was 156 minutes. The furnace maintains a slight positive pressure of 25Pa, the air-fuel ratio of the preheating section is kept at 1.09, the preheating time is 72min, the air-fuel ratio of the heating section is kept at 0.98, the heating time is 68min, the air-fuel ratio of the soaking section is kept at 1.14, and the soaking temperature is controlled at 1172 ℃, soaking time is 26min. During rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 3 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, and the total number of descaling passes is 5. The heat preservation cover is used to reduce the temperature drop in the roughing process. The hourly rolling speed is 9.67m/s, the finish rolling outlet temperature is 874°C, and the coiling temperature is 650°C. The edge shielding technology is adopted in the laminar cooling process to reduce the edge temperature drop of the hot-rolled strip during the cooling process.

The total furnace time of slab 2 during the heating process was 177 minutes. The furnace maintains a slightly positive pressure of 20Pa, the air-fuel ratio in the preheating section is kept at 1.2, the preheating time is 83min, the air-fuel ratio in the heating section is kept at 1.01, the heating time is 70min, the air-fuel ratio in the soaking section is kept at 1.18, and the soaking temperature is controlled at 1180°C, soaking time is 24min. During rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 3 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, the total number of descaling passes is 5, and heat preservation covers are used to reduce the temperature drop in the roughing process. The rolling speed during rolling is 9.33m/s, the finish rolling exit temperature is 880°C, and the coiling temperature is 648°C. The edge shielding technology is adopted in the laminar cooling process to reduce the edge temperature of the hot-rolled strip during the cooling process. drop.

The total time in the furnace of the slab 3 during the heating process was 160 minutes. The furnace maintains a slightly positive pressure of 22Pa, the air-fuel ratio in the preheating section is kept at 1.15, the preheating time is 79min, the air-fuel ratio in the heating section is kept at 0.95, the heating time is 58min, the air-fuel ratio in the soaking section is kept at 1.23, and the soaking temperature is controlled at 1172°C, soaking time is 23min. During rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 3 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, and the total number of descaling passes is 5. The heat preservation cover is used to reduce the temperature drop in the roughing process, and the roughing exit temperature is 1034°C. The entrance temperature of finish rolling is 1008°C, the rolling speed during finish rolling is 9.82m/S, the exit temperature of finish rolling is 861°C, and the coiling temperature is 651°C. During the laminar cooling process, edge shielding technology is adopted to reduce heat loss. The temperature drop at the edge of the rolled strip during the cooling process.

The comparison of the mechanical properties of the hot-rolled coils rolled from the above three slabs is shown in Table 3

Table 3 Comparison of organization and mechanical properties

It can be seen that the microstructure and mechanical properties of the steel coils rolled from the above three slabs all meet the requirements of the standard.

Example 2

According to the requirements of the present invention, carbon-manganese steel slabs with slightly higher carbon and manganese components than the carbon-manganese steel in Example 1 were rolled and produced, and the production conditions of 3 slabs were selected for illustration. The carbon-manganese steel slabs The chemical composition is shown in Table 4, and the temperature of the low-temperature rolling process is shown in Table 5

Table 4 Smelting composition

Table 5 embodiment 2 rolling process temperature

The total furnace time of the slab 1 during the heating process was 170 minutes. The furnace maintains a slightly positive pressure of 25Pa, the air-fuel ratio in the preheating section is kept at 1.2, the preheating time is 78min, the air-fuel ratio in the heating section is kept at 1.08, the heating time is 70min, the air-fuel ratio in the soaking section is kept at 1.11, and the soaking temperature is controlled at 1172°C, soaking time is 22min. During rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 2 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, and the total descaling passes are 4 passes. The heat preservation cover is used to reduce the temperature drop in the roughing process, and the roughing exit temperature is 1048°C. The entrance temperature of finish rolling is 1020°C, the rolling speed of finish rolling is 5.7m/s, the exit temperature of finish rolling is 871°C, and the coiling temperature is 670°C. The edge shielding technology is adopted in the laminar cooling process to reduce hot rolling The temperature drop at the edge of the strip during the cooling process.

The total furnace time of slab 2 during the heating process was 179 minutes. The furnace maintains a slightly positive pressure of 20Pa, the air-fuel ratio in the preheating section is kept at 1.08, the preheating time is 100min, the air-fuel ratio in the heating section is kept at 1.09, the heating time is 53min, the air-fuel ratio in the soaking section is kept at 1.29, and the soaking temperature is controlled at 1180°C, soaking time is 26min. During rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 2 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, and the total number of descaling passes is 4. The heat preservation cover is used to reduce the temperature drop in the roughing process. The rolling speed is 7.5m/S, the finish rolling outlet temperature is 879°C, and the coiling temperature is 680°C. The edge shielding technology is adopted in the laminar cooling process to reduce the edge temperature drop of the hot-rolled strip during the cooling process.

The total furnace time of the slab 3 during the heating process was 153 minutes. The furnace maintains a slight positive pressure of 22Pa, the air-fuel ratio in the preheating section is kept at 1.09, the preheating time is 61min, the air-fuel ratio in the heating section is kept at 1.1, the heating time is 68min, the air-fuel ratio in the soaking section is kept at 1.29, and the soaking temperature is controlled at 1172°C, soaking time is 24min. In rough rolling, 3/4 continuous mill rolling is adopted, the first group of rough rolling mill descaling 1 pass, the second group of rough rolling mill rolling 5 passes, descaling 2 passes, the third group of rough rolling mill descaling 1 pass The fourth group of roughing mills does not descale, and the total number of descaling passes is 4. The heat preservation cover is used to reduce the temperature drop in the roughing process, and the roughing exit temperature is 1040°C. The entrance temperature of finish rolling is 1020°C, the rolling speed of finish rolling is 7.83m/s, the exit temperature of finish rolling is 872°C, and the coiling temperature is 675°C. During the laminar cooling process, edge shielding technology is adopted to reduce hot rolling The temperature drop at the edge of the strip during the cooling process.

The comparison of the mechanical properties of the hot-rolled coils rolled from the above three slabs is shown in Table 6.

Table 6 Comparison of structure and mechanical properties

It can be seen that the microstructure and mechanical properties of the steel coils rolled from the above three slabs all meet the standard requirements.

It can be seen from this embodiment that the present invention proposes a systematic and overall low-temperature rolling production method aimed at the characteristics of carbon-manganese steel slabs, and comprehensively considers the entire heating and rolling production process, which can ensure that the carbon-manganese steel slabs are in good condition. The microstructure and mechanical performance level can effectively reduce heating energy consumption.

The content not described in detail in the specification belongs to the prior art known to those skilled in the art.

Claims (6)

1. An energy-saving rolling method for carbon-manganese steel based on a critical temperature, comprising: preheating a carbon-manganese steel slab through a heating furnace, heating a heating furnace, soaking a heating furnace, descaling before rough rolling, rough rolling, The steps of finish rolling, laminar cooling and coiling process, characterized by: The preheating time of the carbon-manganese steel slab during the preheating treatment in the heating furnace is 50 to 100 minutes, and the preheating temperature is 800 to 1000°C; The heating time of the carbon-manganese steel slab during the heating furnace heating treatment is 40-70 minutes, and the heating temperature is 1150-1220 °C; The soaking time of the carbon-manganese steel slab during the soaking treatment in the heating furnace is 20 to 40 minutes, and the soaking temperature is 1140 to 1180°C; The rough rolling outlet temperature of the carbon-manganese steel slab during rough rolling is 1000-1050°C; The finish rolling inlet temperature of the carbon-manganese steel slab during finish rolling is 980-1020°C, and the finish-rolling outlet temperature is 850-880°C; The temperature of the carbon-manganese steel slab during coiling is 620-680°C; The air-fuel ratio of the carbon-manganese steel slab during preheating treatment in the heating furnace is 1.0-1.2; the air-fuel ratio of the carbon-manganese steel slab during the heating treatment in the heating furnace is 0.9-1.1; The air-fuel ratio during soaking treatment is 1.0-1.4; The critical temperature of carbon-manganese steel rolling process is determined by the following formula: RH＝Max[T (hot brittle), T (C solid solution), T (Mn solid solution), T (descaled)] RT＝Max[T (power of roughing mill), T (bite of rolling mill), T (FT0+ΔT temperature drop during transportation+ΔT descaling temperature drop)] FT0＝Max[T(FT7+ΔT temperature drop during rolling), T(finishing mill capacity), T(recrystallization fraction)] FT7=T(Ar3) CT=T (phase transition temperature) In the above formula: T is the temperature, RH is the critical heating temperature in the soaking section, RT is the critical temperature at the exit of rough rolling, FT0 is the critical temperature at the entrance of finish rolling, FT7 is the critical temperature at the exit of finish rolling, CT is the critical temperature at coiling, T( Hot brittle) represents the hot brittle temperature of the hot brittle slab, at which the slab is more likely to break; T (rough mill force) represents the temperature under the rolling force and power of the rough rolling mill; T (rolling mill Bite) represents the temperature required for the rolling mill to bite into the slab; ΔT temperature drop during transportation represents the temperature loss of rough rolling to finish rolling slab transportation on the roller table; T (recrystallization fraction) represents the microstructure after controlled rolling and the temperature required for mechanical properties; T (phase transition temperature) represents the temperature point at which low carbon steel undergoes phase transition, T (C solid solution) represents the temperature required for C solid solution, and T (Mn solid solution) represents the temperature required for Mn solid solution T (Descaling) represents the heating temperature required to achieve a good descaling effect, ΔT descaling temperature drop represents the temperature drop caused by high-pressure water descaling, T(Ar3) represents the austenite transformation temperature. 2. The energy-saving rolling method of carbon-manganese steel based on critical temperature according to claim 1, characterized in that: the chemical composition of the carbon-manganese steel slab is C: 0.01-0.08%, Si: 0.01-0.20%, Mn: 0.01-0.5%, S≤0.030%, P≤0.030%, and the rest are iron and unavoidable impurities. 3. The critical temperature-based energy-saving rolling method for carbon-manganese steel according to claim 1 or 2, characterized in that: the total furnace time of the carbon-manganese steel slab in the heating furnace is 150 minutes to 180 minutes. 4. The critical temperature-based energy-saving rolling method for carbon-manganese steel according to claim 1 or 2, characterized in that: the furnace pressure in the heating furnace is 10-25Pa. 5. The energy-saving rolling method for carbon-manganese steel based on critical temperature according to claim 1 or 2, characterized in that: the number of descaling passes in the descaling process before rough rolling is 4-8. 6. The energy-saving rolling method of carbon-manganese steel based on critical temperature according to claim 1 or 2, characterized in that: the rolling speed of the carbon-manganese steel slab during finish rolling is 5.5m/s-14m/s s.