A high yield straight rolling, controlled rolling and controlled cooling method

Abstract

The application relates to the technical field of steel metallurgy, and discloses a high-productivity straight rolling, controlled rolling and controlled cooling method. In the straight rolling, controlled rolling and controlled cooling process, the proportion of niobium, vanadium and titanium elements is optimized, and graphite is added, so that the strength, toughness, corrosion resistance and welding performance of the steel are enhanced; the rolling mill temperature, time length, speed and tension are adjusted to refine the crystal grains, improve the precipitate distribution, increase the dislocation density and promote the phase change, so that the mechanical properties of the steel are enhanced; an online system controls a constant-temperature and constant-humidity room, a changing cooling temperature and humidity are adopted to generate fine ferrite and dispersed bainite, the strength and toughness are improved, the heating, rolling and cooling conditions in the process are accurately controlled, the production cost is reduced, the operation process is simplified, the technical requirements of workers are reduced, the wear resistance and fatigue life of the steel are significantly improved, so that the processed steel has the beneficial effects of higher strength, better hardness, better welding performance and better low-temperature toughness.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a high-yield direct rolling controlled rolling and controlled cooling method. Background Technology

[0002] The high-yield direct rolling controlled rolling and controlled cooling technology benefits from China's abundant microalloy resources, technological innovation, domestic and international technical exchanges, and strong national policy support. These factors have jointly promoted the development and application of this technology.

[0003] This technology, through precise control of rolling and cooling temperature and speed, can significantly improve the microstructure and properties of steel. For example, for high-strength low-alloy steel, this technology can refine the grain structure and reduce the interlamellar spacing of pearlite, thereby improving the material's strength and toughness. Furthermore, this technology can significantly improve production efficiency without increasing additional equipment investment. For instance, the application of post-processing ultra-fast cooling technology in hot continuous rolling lines can effectively reduce production cycles and increase output. Simultaneously, controlled rolling and controlled cooling technology also provides a technical approach for developing new steels with superior properties, such as duplex and multiphase steels. Overall, high-yield direct rolling controlled rolling and controlled cooling technology not only improves the performance and quality of steel but also brings considerable economic and social benefits. With continuous innovation and improvement of this technology, its application areas are expected to continue to expand.

[0004] The high-yield direct rolling controlled rolling and cooling technology currently suffers from several drawbacks: Complex process control: Controlled rolling and cooling requires precise control of multiple parameters, including heating temperature, rolling process, and cooling conditions, demanding high skill levels from process control and operators; High technical difficulty: The application of controlled rolling and cooling technology requires in-depth understanding and research into the microstructure, properties, and production processes of steel. This necessitates significant research investment and highly qualified technical personnel and engineers; improper control may affect the performance and quality of the steel; High equipment investment: While controlled rolling and cooling technology can save energy and reduce production costs, the initial equipment investment is substantial, especially for the renovation of older production lines, which may require replacing or upgrading some equipment, increasing investment costs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-yield direct rolling controlled rolling and controlled cooling method, which possesses multiple excellent properties and high overall steel quality, and has the advantages of simple process control, low cost, and low technical difficulty. It solves the problems of low steel performance and quality, complex process control, high cost, and high technical difficulty.

[0006] To achieve the goals of simple process control, low equipment investment, and low technical difficulty in the above-mentioned high-yield direct rolling controlled rolling and cooling technology, this invention provides the following technical solution: The direct rolling controlled rolling and cooling process includes the following steps: Step 1: Heating temperature control: Optimize the composition ratio of steel raw materials, set the processing temperature of the rolling mill to 800-1120℃, and feed the steel into the rolling mill for processing for 10-60 minutes; Step 2: Rolling process control: Adjust parameters such as rolling speed and continuous rolling tension; Step 3: Cooling Condition Control: After repeating the above process four times, perform four cooling cycles, each lasting 30 minutes, with different cooling temperatures and humidity levels each time.

[0007] Preferably, in step one, microalloying elements and other elements are added to the tempering raw materials, wherein the proportion of niobium added is 0.02%, the proportion of vanadium added is 0.02%, the proportion of titanium added is 0.01%, and 0.03% of graphite is added.

[0008] Preferably, in step two, an online intelligent system is installed to control the constant temperature and humidity room. The entire operation is carried out in the constant temperature and humidity room. This system can change the temperature and humidity in a short time and is easy to operate.

[0009] Preferably, in step two, the rolling rate is increased by 10% on the original basis, the rolling tension is increased by 5%, and the rolling pressure is increased by 200MPa on the original basis.

[0010] Preferably, in step three, the first heating is performed at a mill temperature of 1120°C for a processing time of 60 minutes. After the first heating, the cooling temperature is 25°C and the humidity is 55%.

[0011] Preferably, in step three, the secondary heating mill temperature is 1000℃, the hot rolling time is 1 hour, the cooling temperature is 10℃, and the humidity is 45%.

[0012] Preferably, in step three, the secondary heating mill temperature is 900°C, the hot rolling time is 30 min, the cooling temperature is 5°C, and the humidity is 40%.

[0013] Preferably, in step three, the secondary heating mill temperature is 850°C, the hot rolling time is 20 min, the cooling temperature is 0°C, and the humidity is 40%.

[0014] Preferably, in step three, the secondary heating mill temperature is 800℃, the hot rolling time is 10 minutes, the cooling temperature is -5℃, and the humidity is 40%.

[0015] Preferably, in step three, the secondary heating mill temperature is 980℃, the hot rolling time is 30 min, the cooling temperature is 20℃, and the humidity is 50%.

[0016] Compared with the prior art, the present invention provides a high yield direct rolling controlled rolling and controlled cooling method, which has the following beneficial effects: 1. This invention improves the properties of steel in multiple ways by adding optimized proportions of microalloying elements such as niobium, vanadium, and titanium, as well as graphite. The addition of niobium significantly increases the yield strength of steel, and by inducing precipitation and controlling the cooling rate, it achieves dispersed distribution of precipitates, thereby improving the toughness of the steel. The addition of vanadium refines the grain structure, improving both the strength and toughness of the steel. The carbides formed by vanadium and carbon enhance resistance to hydrogen corrosion under high temperature and pressure. The addition of titanium prevents intergranular corrosion and improves the weldability of the steel. During controlled rolling and cooling, the addition of microalloying elements helps improve the physical, chemical, and mechanical properties of steel materials through the dissolution and precipitation mechanisms of C and N compounds under thermal cycling or strain. Yes; the traditional role of microalloying elements niobium, vanadium, and titanium is to refine grains, thereby improving the strength and toughness of steel; while the presence of graphite helps prevent crack propagation, thus compensating for the lack of thermal crack resistance in steel by microalloying elements; graphite can also improve the toughness of steel, making it less prone to fracture and improving its reliability in use. Moreover, as a natural resource, graphite is relatively inexpensive compared to other alloying elements, so it can reduce the production cost of steel to a certain extent. By optimizing the proportion of niobium, vanadium, and titanium and adding graphite, the direct rolling controlled rolling and controlled cooling method has achieved beneficial effects such as improving strength and toughness, improving corrosion resistance, improving weldability, enhancing wear resistance, increasing yield, optimizing the heat treatment process, refining grains, and reducing costs.

[0017] 2. This invention increases the rolling rate by 10%, the rolling tension by 5%, and the rolling pressure by 200 MPa. The 10% increase in rolling rate shortens the rolling time, reduces the time the steel spends at high temperatures, helps control austenite grain growth, and maintains a fine-grained structure. A fine-grained structure helps improve the material's yield strength and toughness. Simultaneously, rapid rolling reduces material temperature rise, optimizes the cooling process and precipitation behavior, reduces the need for manual operation, lowers the technical requirements, and simplifies the operation process. The 5% increase in rolling tension promotes the transformation of austenite to martensite, which helps improve the strength of the steel. Increasing rolling pressure by 200 MPa: Increasing rolling pressure can promote an increase in dislocation density within the material, which helps improve the yield strength. Simultaneously, high pressure also helps break down coarse precipitates, making them more dispersed, thereby improving the material's toughness. Overall effect: The above adjustments work together during controlled rolling and cooling to achieve more refined microstructure control. By increasing rolling rate, rolling tension, and rolling pressure, grain refinement, precipitate distribution optimization, dislocation density improvement, and phase transformation promotion can be achieved. These combined operations reduce production costs, lower worker skill requirements, simplify operating procedures, and simultaneously improve the steel's strength, toughness, wear resistance, and extend its fatigue life.

[0018] 3. In the direct rolling controlled rolling and cooling method of this invention, through four hot rolling and cold rolling processes, and with precise control of cooling conditions each time, the microstructure and properties of the steel can be significantly affected. Specifically, different heating and cooling conditions will affect the refinement of austenite grains, carbide precipitation behavior, and the microstructure and properties after phase transformation. First, the temperature selection during the heating process affects the hardening state of austenite; higher heating temperatures and longer holding times help to obtain more uniform and complete austenitization, providing good microstructure preparation for the subsequent cooling process and phase transformation. Second, the temperature and humidity during the cooling process affect the steel's microstructure and properties. The cooling temperature significantly impacts the microstructure and properties of the steel. Lower cooling temperatures help reduce the austenite transformation temperature and increase undercooling, thereby increasing the driving force for γ-α phase transformation and promoting ferrite grain refinement. Simultaneously, faster cooling rates suppress premature precipitation of carbides and nitrides, resulting in more dispersed precipitates and further improving the steel's strength and toughness. Furthermore, precise control of heating, rolling, and cooling conditions allows for direct rolling and controlled cooling in a constant temperature and humidity environment. This online intelligent system simplifies process control and can be repeated four times, contributing to the optimization of the steel's microstructure. Different combinations of cooling temperature and humidity lead to different microstructures and properties. Cooling at lower temperatures results in a mixed microstructure of fine-grained ferrite and finely dispersed bainite, which helps improve both strength and ductility. Cooling at even lower temperatures may form bainite or acicular ferrite, further improving the steel's strength and toughness. Therefore, this optimized process is not only simple and efficient but also achieves higher strength, better toughness, superior weldability, and better low-temperature toughness. Attached Figure Description

[0019] Figure 1 This is a process diagram of the direct rolling controlled rolling and controlled cooling of the present invention; Figure 2 Comparison of strength, toughness, weldability and hardness properties between Example 1 and Comparative Examples 1-3. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 Specifically, the process of direct rolling controlled rolling and controlled cooling includes the following steps: Step 1: Heating temperature control: Optimize the composition ratio of steel raw materials, set the processing temperature of the rolling mill to 800-1120℃, and feed the steel into the rolling mill for processing for 10-60 minutes; Step 2: Rolling process control: Adjust parameters such as rolling speed and continuous rolling tension; Step 3: Cooling Condition Control: After repeating the above process four times, perform four cooling cycles, each lasting 30 minutes, with different cooling temperatures and humidity levels each time.

[0022] Specifically, in step one, microalloying elements and other elements are added to the tempering raw materials, wherein the proportion of niobium added is 0.02%, the proportion of vanadium added is 0.02%, the proportion of titanium added is 0.01%, and 0.03% of graphite is added.

[0023] The advantages are that this invention achieves multifaceted improvements in steel properties by adding optimized proportions of microalloying elements such as niobium, vanadium, and titanium, as well as graphite. The addition of niobium significantly increases the yield strength of steel, and by inducing precipitation and controlling the cooling rate, it achieves dispersed distribution of precipitates, thereby improving the steel's toughness. The addition of vanadium refines the grain structure, improving both the strength and toughness of the steel. Vanadium carbides formed with carbon enhance resistance to hydrogen corrosion under high temperature and pressure. The addition of titanium prevents intergranular corrosion and improves the weldability of the steel. During controlled rolling and cooling processes, the addition of microalloying elements helps improve the physical, chemical, and mechanical properties of steel materials through the dissolution and precipitation mechanisms of C and N compounds under thermal cycling or strain. Performance; the traditional role of microalloying elements niobium, vanadium, and titanium is to refine grains, thereby improving the strength and toughness of steel; while the presence of graphite helps prevent crack propagation, thus compensating for the lack of thermal crack resistance in steel by microalloying elements; graphite can also improve the toughness of steel, making it less prone to fracture and improving its reliability in use. Moreover, as a natural resource, graphite is relatively inexpensive compared to other alloying elements, thus reducing the production cost of steel to a certain extent. By optimizing the proportion of niobium, vanadium, and titanium and adding graphite, the direct rolling controlled rolling and controlled cooling method has achieved beneficial effects such as improving strength and toughness, improving corrosion resistance, improving weldability, enhancing wear resistance, increasing yield, optimizing the heat treatment process, refining grains, and reducing costs.

[0024] Specifically, in step two, an online intelligent system is installed to control the constant temperature and humidity room. The entire operation is carried out in the constant temperature and humidity room. This system can change the temperature and humidity in a short time and is easy to operate.

[0025] Specifically, in step two, the rolling rate is increased by 10% on the original basis, the rolling tension is increased by 5%, and the rolling pressure is increased by 200MPa on the original basis.

[0026] The advantages are as follows: This invention increases the rolling rate by 10%, the rolling tension by 5%, and the rolling pressure by 200 MPa. The 10% increase in rolling rate shortens the rolling time, reduces the time the steel spends at high temperatures, helps control austenite grain growth, and maintains a fine-grained structure. A fine-grained structure helps improve the material's yield strength and toughness. Simultaneously, rapid rolling reduces material temperature rise, optimizes the cooling process and precipitation behavior, reduces the need for manual operation, lowers the technical requirements, and simplifies the operation process. The 5% increase in rolling tension promotes the transformation of austenite to martensite, which helps improve the strength of the steel. Increasing rolling pressure by 200 MPa: Increasing rolling pressure can promote an increase in dislocation density within the material, which helps improve the yield strength of the material. At the same time, high pressure also helps to break up coarse precipitates, making them more dispersed, thereby improving the toughness of the material. Overall effect: The above adjustments work together in the controlled rolling and controlled cooling process to achieve more refined microstructure control. By increasing the rolling rate, rolling tension, and rolling pressure, the grains can be further refined, the distribution of precipitates can be optimized, the dislocation density can be increased, and phase transformation can be promoted. These comprehensive operations achieve the beneficial effects of reducing production costs, lowering the technical requirements for workers, simplifying the operation process, and improving the strength, toughness, wear resistance, and fatigue life of steel.

[0027] Specifically, in step three, the first heating is performed at a mill temperature of 1120°C for 60 minutes. After the first heating, the cooling temperature is 25°C and the humidity is 55%.

[0028] Specifically, in step three, the secondary heating mill temperature is 1000℃, the hot rolling time is 1 hour, the cooling temperature is 10℃, and the humidity is 45%.

[0029] Specifically, in step three, the secondary heating mill temperature is 900℃, the hot rolling time is 30 minutes, the cooling temperature is 5℃, and the humidity is 40%.

[0030] Specifically, in step three, the secondary heating mill temperature is 850℃, the hot rolling time is 20 minutes, the cooling temperature is 0℃, and the humidity is 40%.

[0031] Specifically, in step three, the secondary heating mill temperature is 800℃, the hot rolling time is 10 minutes, the cooling temperature is -5℃, and the humidity is 40%.

[0032] Specifically, in step three, the secondary heating mill temperature is 980℃, the hot rolling time is 30 minutes, the cooling temperature is 20℃, and the humidity is 50%.

[0033] The advantages are that, in the direct rolling controlled rolling and cooling method of this invention, through four hot and cold rolling processes, and with precise control of cooling conditions each time, the microstructure and properties of the steel can be significantly affected. Specifically, different heating and cooling conditions will affect the refinement of austenite grains, carbide precipitation behavior, and the microstructure and properties after phase transformation. First, the temperature selection during the heating process affects the hardening state of austenite; higher heating temperatures and longer holding times help to obtain more uniform and complete austenitization, providing good microstructure preparation for the subsequent cooling process and phase transformation. Second, the temperature and humidity during the cooling process have a significant impact on... The microstructure and properties of steel are significantly affected by cooling temperatures. Lower cooling temperatures help reduce the austenite transformation temperature and increase undercooling, thereby increasing the driving force of the γ-α phase transformation and promoting ferrite grain refinement. Simultaneously, faster cooling rates can suppress premature precipitation of carbides and nitrides, resulting in more dispersed precipitates and further improving the steel's strength and toughness. Furthermore, by precisely controlling heating, rolling, and cooling conditions, the rolling and cooling process can be directly controlled in a constant temperature and humidity environment. This online intelligent system simplifies process control and can be repeated up to four times, helping to optimize the steel's microstructure. Different combinations of cooling temperature and humidity lead to different microstructures and properties. Cooling at lower temperatures results in a mixed microstructure of fine-grained ferrite and finely dispersed bainite, which helps improve both strength and ductility. Cooling at even lower temperatures may form bainite or acicular ferrite, further improving the steel's strength and toughness. Therefore, this optimized process is not only simple and efficient but also achieves the beneficial effects of higher strength, better toughness, superior weldability, and better low-temperature toughness.

[0034] Comparative Example 1 Specifically, the process of direct rolling controlled rolling and controlled cooling includes the following steps: Step 1: Heating temperature control: Optimize the composition ratio of steel raw materials, set the processing temperature of the rolling mill to 1000℃, and feed the steel into the rolling mill for 50 minutes; Step 2, Rolling process control: Do not change the original parameters such as rolling speed and continuous rolling tension; Step 3: Cooling conditions control: The cooling time is 30 minutes, the cooling temperature is 0℃ and the humidity is 50%.

[0035] Comparative Example 2 Specifically, the process of direct rolling controlled rolling and controlled cooling includes the following steps: Step 1: Heating temperature control: Repeat the above process twice to adjust the steel raw material composition ratio, set the mill processing temperature to 1200℃, and feed the steel into the mill for 20 minutes. Step 2, Rolling process control: Do not change the original parameters such as rolling speed and continuous rolling tension; Step 3: Cooling Condition Control: After cooling, two cooling cycles were performed, each lasting 30 minutes. The cooling temperature was set at 5°C and the humidity was maintained at 45%.

[0036] Comparative Example 3 Specifically, the process of direct rolling controlled rolling and controlled cooling includes the following steps: Step 1: Heating temperature control: Optimize the composition ratio of steel raw materials, set the processing temperature of the rolling mill to 800℃, and feed the steel into the rolling mill for 60 minutes; Step 2, Rolling process control: Do not change the original parameters such as rolling speed and continuous rolling tension; Step 3: Cooling conditions control: After repeating the above process three times, three cooling cycles were performed, each lasting 30 minutes, with a cooling temperature of 0°C and a humidity of 40%.

[0037] I. The laboratory conducted a performance evaluation of the steel after TMCP treatment in Example 1, as shown in Table 1 below: Table 1

[0038] As shown in Table 1, Example 1 exhibits stable performance in all aspects, and some aspects even exceed the standard.

[0039] II. The strength, toughness, weldability, and hardness properties of Example 1 were compared with those of Comparative Examples 1-3 in the laboratory. Figure 2 Information, from Figure 2 Based on the information available, Example 1 outperforms Comparative Examples 1-3 in all performance indicators, including strength, toughness, weldability, and hardness. Specifically, the average values ​​of these performance indicators for Example 1, as well as the comparisons of individual performance indicators, are significantly higher than those for Comparative Examples 1-3. This indicates that Example 1 exhibits superior performance in these aspects. For more detailed information, please refer to [link / reference needed]. Figure 2 : Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-yield direct rolling controlled rolling and controlled cooling method, characterized in that, The process of direct rolling controlled rolling and controlled cooling includes the following steps: Step 1: Heating temperature control: Optimize the composition ratio of steel raw materials, set the processing temperature of the rolling mill to 800-1120℃, and feed the steel into the rolling mill for processing for 10-60 minutes; Step 2: Rolling process control: Adjust rolling speed, continuous rolling tension, and rolling pressure parameters; Step 3: Cooling Condition Control: After repeating the above process four times, perform four cooling cycles, each lasting 30 minutes, with different cooling temperatures and humidity levels each time. Step one involves adding microalloying elements and other elements to the tempering raw materials, wherein the proportion of niobium added is 0.02%, the proportion of vanadium added is 0.02%, and the proportion of titanium added is 0.01%; additionally, 0.03% of graphite is added. In step two, an online intelligent system is installed to control the constant temperature and humidity room. The entire operation is carried out in the constant temperature and humidity room. This system can change the temperature and humidity in a short time and is easy to operate. In step two, the rolling speed is increased by 10% on the original basis, the rolling tension is increased by 5%, and the rolling pressure is increased by 200MPa on the original basis. In step three, the first heating is performed at a mill temperature of 1120°C for 60 minutes. After the first heating, the cooling temperature is 25°C and the humidity is 55%. In step three, the secondary heating mill temperature is 1000℃, the hot rolling time is 1 hour, the cooling temperature is 10℃, and the humidity is 45%. In step three, the secondary heating mill temperature is 900℃, the hot rolling time is 30 minutes, the cooling temperature is 5℃, and the humidity is 40%. In step three, the secondary heating mill temperature is 850℃, the hot rolling time is 20 minutes, the cooling temperature is 0℃, and the humidity is 40%. In step three, the secondary heating mill temperature is 800℃, the hot rolling time is 10 minutes, the cooling temperature is -5℃, and the humidity is 40%. In step three, the secondary heating mill temperature is 980℃, the hot rolling time is 30 minutes, the cooling temperature is 20℃, and the humidity is 50%.

Images