CN114085970B - Manufacturing method for overcoming hot-rolled soft and hard edges of ferrite stainless steel - Google Patents

Abstract

A manufacturing method for overcoming the soft and hard edges of hot-rolled ferritic stainless steel. The method is to slowly cool the hot-rolled steel coils in a heat preservation pit, and at the same time use the heat provided by other hot coils to make the hot-rolled steel coils in the area where the hot-rolled steel coils are located The temperature drops slowly, so that the steel coil can be heated evenly and cool down slowly. The invention adopts special slow cooling measures, utilizes the heat preservation function of the heat preservation pit, and provides heat from other hot coils, so that the temperature in a certain area drops slowly, so that the steel coils can be evenly heated and slowly cooled, which is beneficial to the phase transition of the γ phase. In the process, the α phase is transformed, which effectively improves its mechanical properties and solves the problem of poor forming performance of 430\White.

Description

A manufacturing method for overcoming hot-rolled soft and hard edges of ferritic stainless steel

technical field

The invention belongs to the technical field of metallurgical steel rolling, in particular to a manufacturing method for overcoming soft and hard edges in ferritic stainless steel hot rolling.

Background technique

The existing 430\White products are placed in the storage area after hot rolling, the temperature continues to drop, the temperature difference between the inside and outside is getting bigger and bigger, the cooling speed of each part is uneven, and the mechanical properties are uneven, resulting in concave and convex stripes in the downstream formed products. Poor performance issue.

Contents of the invention

The purpose of the present invention is to provide a manufacturing method that overcomes the soft and hard edges of ferritic stainless steel hot rolling, so as to reduce a series of cost problems caused by poor performance through the control of forming performance. The present invention is easy to operate and suitable for factories Large-scale production can eliminate the problem of uneven mechanical properties of steel coils to the greatest extent. After slow cooling, the surface and internal quality of steel coils are excellent, reducing the occurrence of defective products.

To achieve the above object, the present invention adopts the following technical solutions:

A manufacturing method for overcoming the soft and hard edges of hot-rolled ferritic stainless steel. The method is to slowly cool the hot-rolled steel coils in a heat preservation pit, and at the same time use the heat provided by other hot coils to make the hot-rolled steel coils in the area where the hot-rolled steel coils are located The temperature drops slowly, so that the steel coil can be heated evenly and cool down slowly.

Specifically include the following methods:

1) Heating process of the heat preservation pit: According to the production time, the heat preservation pit should be prepared in advance, and the black steel coils produced by hot rolling with a temperature between 840-900°C are hoisted to the heat preservation pit, and the heat of the black steel coils is used. Raise the temperature of the heat preservation pit, arrange the black steel coils in columns, and set intervals between the columns, so that the temperature in the heat preservation pit rises to 400-500°C;

2) Furnace loading process with temperature: The hot-rolled steel coils that need to overcome the soft and hard edges are lifted to the heat preservation pit immediately after output, and arranged in rows between the black skin preheated steel coils, and the heat preservation pit is closed at the same time to form a closed space ;

3) Heat preservation process: the steel coils need to be stacked in the heat preservation pit for more than 24 hours, and the steel coils cool down slowly;

4) Cooling process: Open the upper cover of the heat preservation pit and contact with the outside world. The cooling rate is 20-60°C/h, so that the temperature drops to 40°C, and then it is taken out of the furnace for the next process.

The hot-rolled steel coil has a thickness of 2.5-10mm and a width of 800-1500mm.

The coiling temperature of the hot-rolled steel coil is 800-1000°C.

Compared with prior art, the beneficial effect of the present invention is:

1) The present invention adopts special slow cooling measures, utilizes the heat preservation function of the heat preservation pit, and provides heat from other hot coils, so that the temperature in a certain area drops slowly, so that the steel coils can be evenly heated and slowly cooled, which is beneficial to the γ phase During the phase change process, the α phase is transformed, which effectively improves its mechanical properties and solves the problem of poor forming performance of 430\White.

2) The coil temperature of the slow cooling steel coil is set at 880°C, which is not only beneficial to the pickling downstream of the steel coil, but also takes into account a sufficiently high output temperature, and cooperates with slow cooling to improve mechanical properties.

3) Adopting the present invention can effectively solve the problem of poor formability of 430\White, the HRB of slow-cooled rolls with black skin is 4-8 lower than that of ordinary rolls, and the elongation of slow-cooled rolls is increased by about 3%-17%.

Description of drawings

Fig. 1 is a comparative diagram of the tensile strength of the embodiment of the present invention and ordinary steel grades without special slow cooling.

Fig. 2 is a comparison chart of the yield strength of the embodiment of the present invention and the common steel grade without special slow cooling.

Fig. 3 is a comparison chart of the elongation of the embodiment of the present invention and the ordinary steel grade without special slow cooling.

Fig. 4 is a comparison diagram of the hardness and strength of the embodiment of the present invention and ordinary steel grades without special slow cooling.

Detailed ways

Below in conjunction with specific embodiment the embodiment of the present invention is further described:

In the embodiment of the present invention, the production of black-skinned steel coils without soft and hard edges and the hot-rolled steel coils of the present invention with soft and hard edges should be scheduled sequentially, and the black-skinned steel coils should be scheduled 3-4 hours in advance.

See Table 1 for the steel composition of the embodiment; see Table 2 for the hot-rolling process parameters of the embodiment;

Table 1 embodiment steel composition (wt%)

C Si mn P S Ni Cr Mo Cu N 0.04 0.35 0.334 0.026 0.003 0.141 16.15 0.008 0.045 0.045

Table 2 embodiment hot rolling process parameter

Table 3 Placement of heat preservation pit

1) Heating process of the heat preservation pit: According to the production time, the heat preservation pit should be prepared in advance, and the ordinary black steel coils should be hoisted to the heat preservation pit immediately after they are produced. The black steel coils are arranged in columns, with intervals between columns , so that the temperature in the heat preservation pit rises to 400-500°C;

According to the rate of black steel coils produced by hot rolling (4-6 minutes/coil), as more and more black steel coils are preheated in the heat preservation pit, the temperature in the heat preservation pit will become higher and higher. It takes 3-4 hours to fill it up, and the temperature in the pit will reach 400-500°C.

2) Furnace loading process with temperature: the hot-rolled steel coil that needs to overcome the soft and hard edges of the present invention is immediately lifted to the heat preservation pit after being produced, and arranged in a row between the black skin preheated steel coils, and the heat preservation pit is closed at the same time , forming a closed space;

3) Heat preservation process: the steel coils need to be stacked in the heat preservation pit for more than 24 hours, and the steel coils cool down slowly;

4) Cooling process: Open the upper cover of the heat preservation pit, and the cooling rate is 20-60°C/h, so that the temperature drops to 40°C, and then it is taken out of the furnace for the next process.

During the hot rolling process, the invention effectively controls the uniform and slow temperature drop of the steel coil through the heat preservation pit, and achieves the effect of the annealing process of the black skin. The comparison with the effect of the prior art is shown in Fig. 1-Fig. 4 .

Claims (2)

1. A manufacturing method for overcoming hot-rolled soft and hard edges of ferrite stainless steel is characterized in that a heat preservation pit slow cooling mode is adopted for a hot-rolled steel coil, and meanwhile, the heat provided by other hot coils is utilized to enable the temperature in the area of the hot-rolled steel coil to be slowly lowered, so that the steel coil can be uniformly heated and slowly cooled;

1) And (3) heating the heat preservation pit: lifting black steel coils which are produced by hot rolling and have the temperature of 840-900 ℃ into a heat preservation pit, and lifting the temperature of the heat preservation pit by using the heat of the black steel coils, wherein the black steel coils are arranged in rows, and intervals are arranged between the rows, so that the temperature in the heat preservation pit is raised to 400-500 ℃;

2) And (3) charging at a temperature: the hot rolled steel coils needing to overcome the soft and hard edges are immediately lifted into the heat preservation pits after being produced, and are arranged between the black-skin preheating steel coils in rows, and meanwhile, the heat preservation pits are closed to form a closed space;

3) The heat preservation process comprises the following steps: stacking the steel coils in the heat preservation pit for more than 24 hours, and slowly cooling the steel coils;

4) And (3) a cooling process: opening an upper cover of the heat preservation pit, wherein the cooling rate is 20-60 ℃/h, so that the temperature is reduced to 40 ℃, and then discharging the pit for the next procedure treatment;

the coil temperature of the hot rolled steel coil is 800-1000 ℃.

2. The method for manufacturing hot rolled soft and hard edges of ferritic stainless steel according to claim 1, wherein the thickness of the hot rolled steel coil is 2.5-10 mm and the width is 800-1500mm.

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