A bar rolling production process considering surface temperature drop compensation

Abstract

This invention discloses a bar rolling production process that considers surface temperature drop compensation, including continuous casting, heat preservation conveying, heating, descaling, continuous rolling under surface temperature control, cooling, shearing, and bundling and collection. By adding induction heating devices between rolling mills, the uniformity of the overall temperature during continuous rolling is controlled, improving the surface hot working performance of bars under high-temperature rolling processes. The distinction between roughing, intermediate, and finishing rolling is eliminated, and a tightly connected continuous rolling mill unit with a short-flow, near-net-shape process layout is adopted, shortening the process flow. Through a combination of rolling deformation and inter-pass induction heating, a uniform temperature field is formed throughout the bar rolling process. After rolling, air cooling ensures a uniform transformation of the microstructure into a ferrite-pearlite microstructure. The produced bar products have excellent surface quality, and the production line features a short production flow, high production efficiency, and low energy consumption, aligning with the green development direction of the iron and steel metallurgical industry.

Description

Technical Field

[0001] The invention relates to the field of iron and steel metallurgy, and in particular to a bar rolling production process taking into account surface temperature drop compensation. Background Art

[0002] As an important intermediate product in the steel industry, round bars are further processed into key supporting parts and connectors in the fields of machinery, hydraulics, automobiles, ships, etc. The product quality of round bars plays an important role in improving the competitiveness of steel companies. In actual production, there are strict requirements for the surface quality of round bars, especially the control of surface cracks. If the round bars produced through a series of processing and manufacturing processes cannot pass the surface flaw detection, they need to be further polished, and in serious cases, they will be directly scrapped. This is because the surface cracks of round bars will further expand during secondary processing such as drawing and forging, affecting the service life of the product, accelerating the failure of the product during use, and even directly breaking during processing, causing major safety accidents. The continuous casting-heating-continuous rolling-cooling process is the most widely used mass production mode for round bar products. Since the intermediate billet is continuously in a high temperature state during the production process, the oxidation behavior of the entire processing and manufacturing process seriously affects the surface quality of the round bars.

[0003] Based on the above considerations, a low-temperature rolling process that reduces oxidation behavior has been proposed and widely used in the field of bar production, that is, reducing the starting rolling temperature to 900-950℃ to reduce surface oxidation behavior during heating and hot rolling, and improve surface quality. However, under the low rolling temperature process, the surface temperature drop caused by multiple continuous heat exchanges between the workpiece and the roller is more prominent. At the same time, the high strain rate caused by the forced deformation of the workpiece surface seriously affects the hot processing performance of the bar surface, resulting in cracking of the bar surface during the rolling process. In addition, the current bar production model has the characteristics of long process and high energy consumption. For example, the energy utilization efficiency in the heating furnace heating mode is low and the pollution problem is serious, the core and surface temperature of the continuous rolling process is uneven, and the phase change of the cooling process is not synchronized, which restricts enterprises from improving quality and efficiency. Summary of the invention

[0004] Based on the above-mentioned deficiencies in the prior art, the present invention provides a bar rolling production process that takes into account surface temperature drop compensation. By adding a regional induction heating device between the frames and adopting a rolling mill-induction heating-rolling mill close connection layout, the overall temperature of the continuous rolling process is maintained at 950-980°C, ensuring that the core and surface microstructures are austenitic, improving the surface hot processing performance, and through air cooling and slow cooling, the organization is fully and evenly transformed. The process method shortens the process flow, improves product quality, reduces energy consumption, and improves production efficiency, and has the characteristics of green manufacturing.

[0005] Specifically, the present invention provides a bar rolling production process taking into account surface temperature drop compensation, comprising the following steps:

[0006] S1: continuous casting, heat preservation and transportation, heating;

[0007] S2: Phosphorus removal;

[0008] S3: continuous rolling under surface temperature control;

[0009] S4: cooling, cutting, baling and collection;

[0010] The continuous rolling under surface temperature control is achieved by closely alternating the rolling mill-induction heating-rolling mill. The specific form is: a continuous rolling mill group is composed of multiple horizontal and vertical alternately arranged pass-type rolling mills, and induction heating devices are arranged between the rolling mills. The core and surface temperature of the rolled piece is uniformly maintained between 950-980°C.

[0011] Furthermore, the cooling method is air cooling to room temperature.

[0012] Furthermore, after the heating or supplementary heat treatment, the surface temperature of the ingot is ensured to be 980-1000°C and the core-surface temperature is ensured to be 950-980°C.

[0013] Furthermore, the induction heating device is a regional induction heating device designed to match the roll pass profile, and the induction heating coil is arranged in the area where the workpiece is in direct contact with the roll.

[0014] Furthermore, the bar rolling production process considering the surface temperature drop compensation includes a single billet rolling mode and a headless rolling mode.

[0015] Furthermore, in the single-bill rolling production mode, the continuous casting machine casts liquid iron to form a solid continuous casting square billet, which is sheared to a certain size by a swing shear and slowly cooled to room temperature. When the subsequent production task begins, it is sent to a heating furnace through a conveyor roller for heating treatment to make the billet reach 950-980°C. After the billet is taken out of the furnace, it is dephosphorized with high-pressure water before entering the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature and are sheared to a certain size by a flying shear before being bundled and collected.

[0016] Furthermore, in the headless rolling production mode, the continuous casting machine casts liquid iron to form solid continuous casting billets, which are quickly transported by an insulated conveyor roller and subjected to surface heating by an induction heating device. After reaching 950-980°C, high-pressure water dephosphorization is carried out, and then the billets enter the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature, and are sheared by a fixed-size flying shear before being bundled and collected.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention achieves close connection of the continuous rolling mill by adding an induction heating device between the frames, thereby reducing the production line space and shortening the process flow. At the same time, the induction heating area is used to supplement the heat, thereby improving the surface thermal processing performance under low-temperature rolling, reducing oxidation and burning, and further controlling the generation of surface cracks.

[0019] (2) The present invention provides a bar rolling production process that takes into account surface temperature drop compensation. Aiming at the existing bar production technology, the present invention adopts advanced production technology to optimize the process path, realizes effective control of hot rolling surface oxidation and crack generation, improves product surface quality, and at the same time reduces cooling time and improves production efficiency, meeting the high-quality, high-efficiency and low-cost development needs of steel metallurgy, and is of great significance in terms of capacity optimization, green manufacturing, and intelligent manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a process flow chart of bar rolling production taking into account surface temperature drop compensation.

[0021] Figure 2 This is the controlled rolling and controlled cooling process diagram of the present invention.

[0022] Figure 3 It is a comparison of the temperature distribution from the surface to the core before and after the heating in a certain pass of the rolling process of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0024] Example: Figure 1-Figure 3 A bar rolling production process considering surface temperature drop compensation is shown, and its process flow includes a continuous casting process, a heating process, a continuous rolling process under surface temperature control, a cooling process and a collection process, including the following steps:

[0025] S1: continuous casting, heat preservation and transportation, heating;

[0026] S2: Descaling: Use high-pressure water descaling box to remove oxides on the surface of continuous casting billet;

[0027] S3: Continuous rolling under surface temperature control: It is realized by closely alternating the rolling mill-induction heating-rolling mill. The specific form is: the continuous rolling mill group is a horizontal and vertical alternately arranged pass type rolling mill, and an induction heating device is arranged between the rolling mills to control the temperature of the area where the rolled piece is in direct contact with the rollers, ensuring that the core and surface temperature of the rolled piece is uniformly maintained between 950-980℃, and ensuring that the core and surface microstructure is austenite;

[0028] S4: Cooling, shearing, bundling and collection; the cooling process is air cooling to room temperature, and the rolled piece structure is evenly transformed into ferrite + pearlite structure through air cooling, and then sheared by a fixed-size flying shear and bundled and collected.

[0029] After heating or supplementary heat treatment, the surface temperature of the ingot is guaranteed to be 980-1000℃, and the core-surface temperature is 950-980℃, which is guaranteed to be above the austenite recrystallization temperature, reducing oxidation and burning while ensuring the hot processing performance of carbon steel.

[0030] The induction heating device is a regional induction heating device designed to match the roll hole shape. The induction heating coil is arranged in the area where the workpiece is in direct contact with the roll, so as to achieve targeted heating in the area where the temperature of the workpiece drops sharply.

[0031] In single billet rolling production mode: the continuous casting machine casts liquid iron to form solid continuous casting square billets, which are sheared to a certain size by a swing shear and slowly cooled to room temperature. When the subsequent production task begins, the billets are sent to the heating furnace through the conveyor roller for heating treatment to make the billets reach 950-980℃. After the billets are taken out of the furnace, they are dephosphorized with high-pressure water before entering the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature and are sheared by a fixed-size flying shear before being bundled and collected.

[0032] In the headless rolling production mode, the continuous casting machine casts liquid iron to form solid continuous casting billets, which are quickly transported by an insulated conveyor roller and heated on the surface by an induction heating device. After reaching 950-980°C, high-pressure water is used for dephosphorization. The billets then enter the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature and are sheared by a fixed-size flying shear before being bundled and collected.

[0033] In a specific embodiment, the material element composition and content are shown in Table 1, and the process flow chart is shown in Figure 1 As shown, the temperature-deformation-structure control process is as follows Figure 2 shown.

[0034] Table 1

[0035] Element Type C Mn Si S P Fe Mass percentage 0.12 0.124 0.065 0.016 0.025 99.67

[0036] In the production process of this embodiment, a single billet rolling production mode is adopted. After the continuous casting process of the ingot, it is sheared to a certain size by a swing shear and then centrally cooled to room temperature. The ingot has a length of 12000 mm, a width of 220 mm and a height of 220 mm. At the beginning of rolling production, the ingot is sent to a walking beam heating furnace for centralized heating treatment. After being taken out of the furnace, the overall temperature of the ingot is 1000°C, and the core and surface temperatures are uniform. Subsequently, after being fully descaled by a high-pressure water descaling box and warmed up during the transportation process, the surface temperature before entering the continuous rolling unit is 960°C, and the core and surface temperature is 980°C.

[0037] During the continuous rolling process, the ingot passes through the box-shaped, elliptical and circular hole system of the rolling mills, and its shape changes from square to circular. Due to the heat exchange between the ingot and the rollers, the surface temperature of the ingot is reduced to 790℃, and the core-surface temperature is maintained at 980℃ basically unchanged. The induction heating device between the rolling mills is used to supplement the heat in the area where the surface is in direct contact with the rollers. Before entering the next rolling mill, the surface temperature of the rolled piece is heated to 980℃, and the core-surface temperature is maintained at 980℃. The above process is repeated in sequence until the continuous rolling process is completed.

[0038] Then the rolled piece enters the cooling bed and is air-cooled to room temperature, where the structure is uniformly transformed into a ferrite plus pearlite structure.

[0039] After the above process, oxidation burning and crack formation in the bar rolling process are reduced, which improves product quality. At the same time, it ensures sufficient organizational transformation, reduces cooling time, and improves production efficiency. The resulting high-quality bars do not require grinding. After secondary processing, they can be used as key supporting parts and connecting parts and are widely used in various fields such as engineering, infrastructure, and the automotive industry.

[0040] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope of the present invention.

Claims

1. A bar rolling production process taking into account surface temperature drop compensation, characterized in that: The process includes: S1: continuous casting, heat preservation and transportation, heating; S2: Phosphorus removal; S3: continuous rolling under surface temperature control; S4: cooling, cutting, baling and collection; The continuous rolling under surface temperature control is realized by closely and alternately connecting the rolling mill, induction heating and rolling mill, and the specific form is: The continuous rolling mill consists of multiple horizontal and vertical groove rolling mills, with induction heating devices arranged between the rolling mills. The core and surface temperature of the rolled piece is evenly maintained between 950-980℃. The induction heating device is a regional induction heating device designed to match the roll pass, and the induction heating coil is arranged in the contact area between the rolled piece and the roll; During the continuous rolling process, the ingot passes through the box-shaped, elliptical and circular hole system of the rolling mills, and its shape changes from square to circular. Due to the heat exchange between the ingot and the rollers, the surface temperature of the ingot is reduced to 790℃, and the core-surface temperature is maintained at 980℃ basically unchanged. The induction heating device between the rolling mills is used to supplement the heat in the area where the surface is in direct contact with the rollers. Before entering the next rolling mill, the surface temperature of the rolled piece is heated to 980℃, and the core-surface temperature is maintained at 980℃. The above process is repeated in sequence until the continuous rolling process is completed.

2. A bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: The cooling method is air cooling to room temperature.

3. A bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: After heating or supplementary heat treatment, the surface temperature of the ingot is guaranteed to be 980-1000℃ and the core temperature is 950-980℃.

4. The bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: The bar rolling production process considering the surface temperature drop compensation includes a single billet rolling mode or an endless rolling mode.

5. The bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: In the single billet rolling production mode, the continuous casting machine casts liquid iron to form a solid continuous casting square billet, which is sheared to a certain size by a swing shear and slowly cooled to room temperature. When the subsequent production task begins, it is sent to the heating furnace through a conveyor roller for heating treatment to make the billet reach 950-980℃. After the billet is taken out of the furnace, it is dephosphorized with high-pressure water before entering the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature and are sheared to a certain size by a flying shear before being bundled and collected.

6. The bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: In the headless rolling production mode, the continuous casting machine casts liquid iron to form solid continuous casting billets, which are quickly transported by an insulated conveyor roller and heated on the surface by an induction heating device. After reaching 950-980°C, high-pressure water is used for dephosphorization. The billets then enter the continuous rolling unit. An induction heating device is added between the rolling mills in the continuous rolling unit to achieve a close alternation of rolling mill-induction heating-rolling mill to ensure uniform core and surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to slowly cool to room temperature and are sheared by a fixed-size flying shear before being bundled and collected.

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