CN115430712A - A Bar Rolling Production Process Considering Surface Temperature Drop Compensation - Google Patents

Abstract

The invention discloses a bar rolling production process considering surface temperature drop compensation, which comprises continuous casting, heat preservation and transportation, heating, dephosphorization, surface temperature control and continuous rolling, cooling, shearing, bundling and collection. The induction heating device is additionally arranged between rolling mills, the uniformity of the whole temperature in the continuous rolling process is controlled, the surface hot processing performance of the bar under the high-temperature rolling process is improved, the distinction of rough rolling, intermediate rolling and finish rolling is cancelled, the continuous rolling mill set is adopted for tight connection, the short-flow and near-net-shape process arrangement is adopted, the process flow is shortened, the bar rolling process is realized through the combination mode of rolling deformation and inter-pass induction heating, the uniform temperature field is integrally formed, and the air cooling is carried out after rolling, so that the microstructure is ensured to be uniformly converted into the ferrite plus pearlite structure. The produced bar product has good surface quality, and the production line has the characteristics of short production flow, high production efficiency and low energy consumption, and accords with the green development direction of the ferrous metallurgy industry.

Description

A Bar Rolling Production Process Considering Surface Temperature Drop Compensation

technical field

The invention relates to the field of iron and steel metallurgy, in particular to a bar rolling production process considering surface temperature drop compensation.

Background technique

As an important intermediate product in the iron and steel industry, round bars are further processed into key supports 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 iron and steel enterprises. In actual production, there are strict requirements on 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 test, further grinding is required, and in serious cases, they will be scrapped directly. . This is because the cracks on the surface of the round bar will further expand and affect the service life of the product during secondary processing such as drawing and forging, accelerate product failure during use, and even break directly during processing, causing major safety accidents. The continuous casting-heating-rolling-cooling process is the most widely used mass production mode for round bar products. Since the intermediate billet is continuously at high temperature during the production process, the oxidation behavior in the whole process of manufacturing process seriously affects the surface of the round bar. quality.

Based on the above considerations, a low-temperature rolling process to reduce oxidation behavior has been proposed and widely used in the field of bar production, that is, reducing the rolling start temperature to 900-950°C to reduce surface oxidation during heating and hot rolling, and improve surface quality. However, under the lower rolling temperature process, the surface temperature drop caused by the direct contact between the rolled piece and the roll with multiple passes of continuous heat exchange is more prominent. At the same time, the high strain rate caused by the forced deformation of the rolled piece surface seriously affects the surface of the bar. Hot workability, resulting in cracking of the bar surface during rolling. Moreover, the current bar production mode has the characteristics of long process and high energy consumption. For example, in the heating mode of the heating furnace, the energy utilization efficiency is not high and the pollution problem is serious. Enterprises improve quality and efficiency.

Contents of the invention

Based on the deficiencies of the above-mentioned prior art, the present invention provides a bar rolling production process that considers surface temperature drop compensation, by adding a regional induction heating device between the racks, and adopting the arrangement form of rolling mill-induction heating-rolling mill close connection, to realize The overall temperature of the continuous rolling process is maintained at 950-980°C to ensure that the microstructure of the core surface is austenitic, improve the surface thermal processing performance, and ensure the sufficient and uniform transformation of the structure through air cooling and slow cooling. This process shortens the process flow and improves the Product quality, reduced energy consumption, improved production efficiency, has the characteristics of green manufacturing.

Specifically, the present invention provides a bar rolling production process considering surface temperature drop compensation, comprising the following steps:

S1: Continuous casting, insulation conveying, heating;

S2: phosphorus removal;

S3: continuous rolling under surface temperature control;

S4: cooling, shearing, bundling and collecting;

The continuous rolling under surface temperature control is realized through the close alternate connection of rolling mill-induction heating-rolling mill. The specific form is: a continuous rolling unit is composed of a plurality of alternately arranged horizontal and vertical pass rolling mills, and induction heating is arranged between the rolling mills. device, and the surface temperature of the rolled piece is kept uniformly between 950-980°C.

Further, the cooling method is air cooling to room temperature.

Further, after the heating or supplementary heat treatment, the surface temperature of the slab is guaranteed to be 980-1000°C, and the core surface temperature is 950-980°C.

Further, the induction heating device is an area induction heating device matched with the roll pass design, and the induction heating coil is arranged in the direct contact area between the rolled piece and the roll.

Further, the bar rolling production process considering surface temperature drop compensation includes a single billet rolling mode and an endless rolling mode.

Further, in the single billet rolling production mode, the continuous casting machine casts molten iron to form a solid continuous casting billet, which is cut to size by pendulum shears, and slowly cooled to room temperature. The roller table is sent into the heating furnace for heating treatment, so that the cast slab reaches 950-980°C. After the cast slab is released from the furnace, it is dephosphorized by high-pressure water before entering the continuous rolling mill. Induction heating-rolling mills are arranged closely and alternately to ensure uniform core surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to cool slowly to room temperature, and are bundled and collected after being cut by fixed-size flying shears.

Furthermore, in the endless rolling production mode, the continuous casting machine casts the molten iron to form a solid continuous casting billet, which is quickly conveyed through the heat preservation conveying roller table and the surface is supplemented by an induction heating device. After reaching 950-980°C, the The high-pressure water removes phosphorus, and then enters the continuous rolling unit. In the continuous rolling unit, an induction heating device is added between the rolling mills to realize the close alternate arrangement of the rolling mill-induction heating-rolling mill, to ensure the uniform temperature of the core surface during the continuous rolling production process. After continuous rolling, the bar enters the cold The bed was cooled slowly to room temperature, and then collected in bundles after being cut by flying shears to a certain size.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The present invention realizes the close connection of continuous rolling units by adding induction heating devices between racks, compresses the space of the production line, shortens the process flow, and at the same time supplements heat through the induction heating area to improve the thermal processing performance of the lower surface of low-temperature rolling , to further control the generation of surface cracks while reducing oxidation burning loss.

(2) A bar rolling production process considering surface temperature drop compensation provided by the present invention aims at the existing bar production technology, adopts advanced production technology to optimize the process path, and realizes effective control of hot rolling surface oxidation and crack generation , improve the surface quality of the product, at the same time, reduce the cooling time, improve the production efficiency, meet the development needs of high-quality, high-efficiency, and low-cost iron and steel metallurgy, and are of great significance in terms of production capacity optimization, green manufacturing, and intelligent manufacturing.

Description of drawings

Fig. 1 is a flow chart of a bar rolling production process considering surface temperature drop compensation in the present invention.

Fig. 2 is a process diagram of controlled rolling and controlled cooling in the present invention.

Fig. 3 is a comparison of the temperature distribution from the surface to the core of a certain pass of the rolling process of the present invention, before and after the heat supplement.

detailed description

The present invention will be further described below in conjunction with specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not as a limitation to the present invention.

Embodiment: a kind of bar rolling production process that considers surface temperature drop compensation as shown in Fig. 1-Fig. process, including the following steps:

S1: Continuous casting, insulation conveying, heating;

S2: Descaling: Use a high-pressure water descaling box to remove oxides on the surface of the continuous casting slab;

S3: Continuous rolling under surface temperature control: It is realized through the close alternate connection of rolling mill-induction heating-rolling mill. The specific form is: the continuous rolling mill is a horizontal-vertical rolling mill, and an induction heating device is arranged between the rolling mills. Regional temperature control is carried out at the direct contact position between the rolled piece and the roll to ensure that the surface temperature of the rolled piece is uniformly maintained between 950-980°C, and the microstructure of the core surface is austenite;

S4: Cooling, shearing, bundling and collection; the cooling process is air cooling to room temperature, after air cooling, the structure of the rolled piece is uniformly transformed into a ferrite + pearlite structure, and then bundled and collected after being cut by a fixed-size flying shear.

After heating or supplementary heat treatment, the surface temperature of the casting slab is guaranteed to be 980-1000°C, and the core surface temperature is 950-980°C, which is guaranteed to be above the austenite recrystallization temperature, reducing oxidation and burning loss and ensuring the thermal processing performance of carbon steel.

The induction heating device is a regional induction heating device that matches the design of the roll pass. The induction heating coil is arranged in the direct contact area between the rolled piece and the roll to achieve targeted supplementary heating in the area of severe temperature drop of the rolled piece.

In the production mode of single billet rolling: the continuous casting machine casts molten iron into a solid continuous casting billet, cuts it to a fixed size through the pendulum shear, and after cooling slowly to room temperature, when the subsequent production task starts, it is sent to the billet through the conveyor roller table. Put it into the heating furnace for heating treatment, so that the cast slab reaches 950-980 ℃. After the cast slab is released from the furnace, it will be dephosphorized by high-pressure water before entering the continuous rolling mill. The rolling mills are closely arranged alternately to ensure that the temperature of the core surface is uniform during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to cool slowly to room temperature, and are bundled and collected after being cut by fixed-size flying shears.

In the endless rolling production mode, the continuous casting machine casts the molten iron into a solid continuous casting billet, which is quickly conveyed through the heat preservation conveying roller table, and the surface is supplemented by an induction heating device. After reaching 950-980°C, high-pressure water removal is performed. Phosphorus, and then enter the continuous rolling unit, in the continuous rolling unit, an induction heating device is added between the rolling mills to realize the close alternate arrangement of the rolling mill-induction heating-rolling mill, to ensure the uniform temperature of the core surface during the continuous rolling production process, and the bar enters the cooling bed for slow cooling after continuous rolling to room temperature, and bundled and collected after being cut to a certain size by flying shears.

In a specific embodiment, the composition and content of material elements are shown in Table 1, the process flow chart is shown in Figure 1, and the temperature-deformation-structure control process is shown in Figure 2.

Table 1

Element type C mn Si S P Fe mass percentage 0.12 0.124 0.065 0.016 0.025 99.67

In the production process of this embodiment, the single slab rolling production mode is adopted. After the slab is continuously cast, it is cut to size by pendulum shears and then cooled to room temperature. The length of the slab is 12000mm, the width is 220mm, and the height is 220mm. At the beginning of rolling production, the cast slab is sent into the walking beam heating furnace for centralized heating treatment. After being released from the furnace, the overall temperature of the cast slab is 1000°C, and the core surface temperature is uniform. After that, it is fully descaled by the high-pressure water descaling box and After returning to temperature during the conveying process, the surface temperature before entering the continuous rolling mill is 960°C, and the core surface temperature is 980°C.

During the continuous rolling process, the casting slab passes through the box-ellipse-circular pass system, which is alternately arranged horizontally and vertically, and the shape changes from square to circular. Due to the heat exchange between the slab and the roll, the surface temperature drops to 790 ℃, the core surface temperature remains basically unchanged at 980°C, and the surface temperature of the rolled piece is raised to 980°C before entering the next rolling mill, and the core surface temperature is maintained at 980°C , repeat the above process in turn until the end of the continuous rolling process.

Then it enters the cooling bed and air cools to room temperature, and the structure of the rolled piece is uniformly transformed into a ferrite plus pearlite structure.

Through the above process, the oxidation burning loss and crack formation in the bar rolling process are reduced, the product quality is improved, and at the same time, the structure is fully transformed, the cooling time is reduced, and the production efficiency is improved. Afterwards, it can be widely used in various fields such as engineering, infrastructure, and automobile industry as key supports and connectors.

The above embodiments are only descriptions of preferred implementations 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, those skilled in the art may make various modifications to the technical solutions of the present invention. and improvements should fall within the protection scope of the present invention.

Claims (7)

1. A bar rolling production process considering surface temperature drop compensation, characterized in that: comprising the following processes: S1: Continuous casting, insulation conveying, heating; S2: phosphorus removal; S3: continuous rolling under surface temperature control; S4: cooling, shearing, bundling and collecting; The continuous rolling under the surface temperature control is realized by closely alternately connecting the rolling mill-induction heating-rolling mill, and the specific form is: The continuous rolling unit is composed of multiple horizontal and vertical pass rolling mills, and an induction heating device is arranged between the rolling mills. The core surface temperature of the rolled piece is uniformly maintained between 950-980°C. 2. A bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: the cooling method is air cooling and cooled 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 slab is guaranteed to be 980-1000°C, and the core surface temperature is 950-1000°C. 980°C. 4. A bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: the induction heating device is an area induction heating device matching the roll pass design, and the induction heating coil is arranged in The contact area between the rolled piece and the roll. 5. A bar rolling production process considering surface temperature drop compensation according to claim 1, characterized in that: the bar rolling production process considering surface temperature drop compensation includes single billet rolling mode or endless rolling control mode. 6. A bar rolling production process considering surface temperature drop compensation according to claim 5, characterized in that: during the single billet rolling production mode, the continuous casting machine casts liquid molten iron to form a solid continuous casting billet, Cut to size by pendulum shears, after slow cooling to room temperature, when the subsequent production task starts, it will be sent to the heating furnace for heating treatment through the conveying roller table, so that the casting billet reaches 950-980 °C, and the casting billet is in the Before entering the continuous rolling unit, high-pressure water dephosphorization is carried out. In the continuous rolling unit, an induction heating device is added between the rolling mills to realize the close alternate arrangement of the rolling mill-induction heating-rolling mill, to ensure that the core surface temperature is uniform during the continuous rolling production process. After continuous rolling, the bar enters the cold The bed was cooled slowly to room temperature, and then collected in bundles after being cut by flying shears to a certain size. 7. A bar rolling production process considering surface temperature drop compensation according to claim 5, characterized in that: in the endless rolling production mode, the continuous casting machine casts liquid molten iron to form a solid continuous casting billet, It is quickly conveyed through the heat preservation conveying roller table and the surface is supplemented by an induction heating device. After reaching 950-980°C, high-pressure water dephosphorization is carried out, and then enters the continuous rolling unit. In the continuous rolling unit, an induction heating device is added between the rolling mills to realize rolling mill- Induction heating-rolling mills are arranged closely and alternately to ensure uniform core surface temperature during the continuous rolling production process. After continuous rolling, the bars enter the cooling bed to cool slowly to room temperature, and are bundled and collected after being cut by fixed-size flying shears.

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