Rolling process for improving surface quality and cooling uniformity of Sn-containing steel plate

Abstract

The invention belongs to the technical field of metallurgical medium plate rolling, and particularly relates to a rolling process for improving the surface quality and cooling uniformity of a Sn-containing steel plate, which is characterized in that the Sn-containing (Sn > = 0.02%) steel plate with the rolling length of 40-60m is subjected to three-stage controlled rolling, the temperature difference between the head and the tail of the steel plate is controlled to be 20-50 DEG C, and the cooling rate is more than 10 DEG C / s; and the shape and surface quality of the steel plate meet standard technical requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical medium and thick plate rolling, in particular to a rolling process for improving the surface quality and cooling uniformity of Sn-containing steel plates. Background Art

[0002] Under the national background of “carbon peak” and “carbon neutrality”, the steel industry is also developing in the direction of greening and intelligence. A large number of thermomechanical rolled medium and thick plate products and production processes have been developed and applied, and scrap steel resources are widely used due to their unique green and low-carbon advantages. However, the recycling of scrap steel resources will inevitably involve the enrichment of residual elements in steel, especially elements with low oxidation potential such as Cu, Sn and As. At present, the existing smelting process of steel enterprises cannot effectively remove Sn with low oxidation potential. When the slab enters the next heating process, Sn is enriched on the surface of the steel plate due to the formation of iron oxide scale, which affects the smooth progress of the rolling production process, especially the surface quality of the steel plate, which greatly reduces the cooling uniformity of the steel plate. When the Sn content exceeds 0.02%, the final cooling temperature of the thermomechanical rolled steel plate with a rolling length of 40-60m is increased by 100-150℃, and the cooling of the head and tail of the steel plate is very uneven, with the temperature difference between the head and tail even reaching 150℃. Strip-shaped black substances appear on the surface, which ultimately affects the performance of the product. Summary of the invention

[0003] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a rolling process for improving the surface quality and cooling uniformity of Sn-containing steel plates. The technical solution to the problem is that the present invention discloses a rolling process for improving the surface quality and cooling uniformity of Sn-containing steel plates. The present invention optimizes the controlled rolling and controlled cooling process of Sn-containing steel plates (especially Sn reaching more than 0.02%) in a targeted manner, so that the temperature difference of the same steel plate is accurately controlled at 20-50°C, the surface quality is good, and the product image of thermomechanical rolled steel is greatly improved.

[0004] A rolling process for improving the surface quality and cooling uniformity of Sn-containing steel plates, characterized in that: Sn-containing (Sn≥0.02%) steel plates with a rolling length of 40-60m are rolled in three stages, the temperature difference between the head and tail of the steel plates is controlled at 20-50°C, the cooling rate is above 10°C / s, and the steel plate shape and surface quality meet standard technical requirements.

[0005] In the heating process, the continuous casting billet produced by steelmaking and continuous casting enters the heating process after slow cooling, and the heating temperature in the walking beam heating furnace is controlled at 1180-1250° C., and the time in the furnace is ≤120 min.

[0006] In the rolling process, the ingot produced by steelmaking continuous casting is subjected to three-stage controlled rolling in the rolling mill after slow cooling, heating and descaling, with 11 rolling passes, 3 passes in the first stage, 1 pass in the second stage, and 7 passes in the third stage. The cumulative reduction rate of the first stage controlled rolling is ≥35%. After the first stage controlled rolling is completed, the intermediate cooling process is reasonably used to cool the temperature of the intermediate billet to below 950°C, and the second stage controlled rolling is carried out. The single-pass reduction rate of the second stage is ≥10%. After the temperature is warmed, the third stage controlled rolling is carried out, and the final rolling temperature is ≤800°C.

[0007] In the controlled cooling process, the ingot produced by the steelmaking continuous casting undergoes slow cooling, heating and descaling, and then is subjected to three-stage controlled rolling in the rolling mill for controlled cooling. The final cooling temperature is controlled at 350-550°C according to the grade of steel, so that the head and tail temperature difference of the steel plate with a rolling length of 40-60m is stably controlled at 20-50°C, and the cooling rate reaches more than 10°C / s, which greatly improves the cooling uniformity of the steel plate.

[0008] By reducing the temperature of Sn-containing (Sn≥0.02%) steel plates with a rolling length of 40-60m to 20-50℃, the cooling rate reaches more than 10℃ / s, and the final cooling temperature is controlled at 350-550℃ according to the steel grade, the cooling uniformity of the steel plate is guaranteed, the plate shape hit rate of Sn-containing (Sn≥0.02%) steel plates is as high as 98.50%, and the surface quality and performance meet the standard requirements.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention greatly reduces the enrichment of Sn content with low oxidation potential on the surface of Sn-containing (Sn ≥ 0.02%) steel plates by optimizing existing controlled rolling and controlled cooling, improves the surface quality of Sn-containing steel plates and the plate shape hit rate up to 98.50%, and improves the overall cooling uniformity of the steel plates.

[0010] 2. The present invention solves the problem of removing Sn by steelmaking process, and replaces the need to rely on high-cost high-quality iron ore resources to control the source of Sn from the source to solve the adverse effects of high Sn in steel. It has low cost, high efficiency and increases enterprise benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Graphs showing key rolling process parameters and cooling effects of various embodiments of the present invention. DETAILED DESCRIPTION

[0012] The following is combined with Figure 1 The specific implementation modes of the present invention are further described in detail.

[0013] Embodiment 1: The steel plate with a thickness of 30mm is rolled. The rolling process includes: after the continuous casting billet is heated at high temperature, the primary iron oxide scale on the surface of the steel plate is removed by a descaling machine, and then it enters the furnace coil mill for two-stage controlled rolling. After the first stage of controlled rolling is completed, the temperature of the intermediate billet is reduced to below 950°C by laminar cooling, and then the second stage of controlled rolling is carried out. After the temperature is warmed, the third stage of rolling is carried out, and the laminar flow is used for controlled cooling of thermomechanical rolled steel. The final cooling temperature is precisely controlled at 350-550°C according to the requirements, the head and tail temperature difference is controlled at 20-50°C, the cooling rate reaches more than 10°C, and the surface quality is good. The key rolling process parameters and cooling effects of each embodiment are shown as follows Figure 1 shown.

[0014] Embodiment 2: Another steel plate with a thickness of 30mm is rolled. The rolling process includes: after the continuous casting billet is heated at high temperature, the primary iron oxide scale on the surface of the steel plate is removed by a descaling machine, and then it enters the furnace coil mill for two-stage controlled rolling. After the first stage of controlled rolling is completed, the temperature of the intermediate billet is reduced to below 950°C by laminar cooling, and then the second stage of controlled rolling is carried out. After the temperature is warmed, the third stage of rolling is carried out, and laminar flow is used for controlled cooling of thermomechanical rolled steel. The final cooling temperature is accurately controlled at 350-550°C according to requirements, the head and tail temperature difference is controlled at 20-50°C, the cooling rate reaches more than 10°C, and the surface quality is good. The key rolling process parameters and cooling effects of each embodiment are shown as follows Figure 1 shown.

Claims

1. A rolling process for improving the surface quality and cooling uniformity of Sn-containing steel sheets, characterized in that: The steel plates with Sn≥0.02% and rolling length of 40-60m are rolled in three stages. The temperature difference between the head and tail of the steel plates is controlled at 20-50℃, the cooling rate is above 10℃ / s, and the plate shape and surface quality meet the standard technical requirements.

2. The rolling process according to claim 1, wherein the ingot produced by smelting and continuous casting is subjected to three-stage controlled rolling in a rolling mill after slow cooling, heating and descaling; characterized in that: There are 11 rolling passes, 3 passes in the first stage, and the cumulative rolling reduction rate is controlled to be ≥35%. After rolling, the intermediate billet temperature is cooled to below 950℃ using the intermediate layer flow cooling equipment; there is 1 pass in the second stage, and the single pass reduction rate is ≥10%; after waiting for temperature, the third stage is carried out with 7 controlled rolling passes, and the final rolling temperature is ≤800℃.

3. In the controlled cooling process described in claim 1, the continuous casting ingot is subjected to controlled cooling after three-stage controlled rolling, so that the temperature difference between the head and tail of the steel plate with a rolling length of 40-60m is controlled at 20-50°C, and the cooling rate reaches more than 10°C / s. The final cooling temperature is controlled at 350-550°C according to the steel grade, and the cooling uniformity of the steel plate is guaranteed.

4. A rolling process for improving the surface quality and cooling uniformity of Sn-containing steel sheets according to claims 1-3, characterized in that: By reducing the temperature of steel plates with a content of Sn ≥ 0.02% and a rolling length of 40-60m to 20-50℃, the cooling rate reaches more than 10℃ / s, and the final cooling temperature is controlled at 350-550℃ according to the steel grade, the cooling uniformity of the steel plates is guaranteed, the plate type hit rate of steel plates with a content of Sn ≥ 0.02% is as high as 98.50%, and the surface quality and performance meet the standard requirements.

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