CN118699062A - A cold-rolled raw material coil and a method for controlling surface quality defects thereof - Google Patents

Abstract

The invention discloses a cold-rolled raw material roll and a control method of surface quality defects thereof, and belongs to the technical field of cold rolling; comprising the following steps: and (3) temperature control: the tapping temperature of the heating furnace is controlled to be 1210-1230 ℃, and the finish rolling temperature of the intermediate billet entering the finishing mill is controlled to be 960-1020 ℃; and (3) width reduction control: when the width of the plate blank is not smaller than 30mm of the width of the finished product, setting the side pressure; dephosphorization: dephosphorization is carried out before the roughing mill and before the finishing mill, and meanwhile, dephosphorization is carried out in the process of the fourth pass of the roughing mill; and (3) controlling finish rolling process water: the roll anti-stripping water function is used, and reverse water spray between the frames is synchronously started to purge impurities on the surface of the strip steel in time. The invention can reduce or eliminate the surface quality defect of the cold-rolled raw material coil by comprehensively controlling the temperature, the width reduction, the dephosphorization and the finish rolling process water in the production process.

Description

A cold-rolled raw material coil and a method for controlling surface quality defects thereof

Technical Field

The invention belongs to the technical field of cold rolling, and in particular relates to a cold-rolled raw material coil and a method for controlling surface quality defects thereof.

Background Art

In the field of steel manufacturing, especially in the cold rolling process, the surface quality of the raw coil is placed in a crucial position. This high requirement is mainly focused on the defect control of surface oxide scale. In all aspects of steel rolling production, whether it is the furnace oxide scale generated in the heating process, the secondary oxide scale formed in the rough rolling and finishing rolling processes, or the press-in defects caused by the peeling of the oxide film on the surface of the roll, these factors will have a significant negative impact on the surface quality of the strip. Therefore, these issues must be strictly controlled and managed throughout the rolling process to ensure that the surface quality of the final product can meet the high standards of industry requirements.

Summary of the invention

In order to solve the technical problems existing in the known technology, the present invention provides a method for controlling a cold-rolled raw material coil and its surface quality defects, which can reduce or eliminate the surface quality defects of the cold-rolled raw material coil by comprehensively controlling the temperature, width reduction, phosphorus removal and finishing process water control in the production process of the cold-rolled raw material coil.

The first object of the present invention is to provide a method for controlling surface quality defects of a cold-rolled raw material coil, wherein the production process equipment of the cold-rolled raw material coil includes a heating furnace, a rough rolling mill, a finishing rolling mill, a laminar cooling device and a coiling device; the control method includes:

Temperature control: The tapping temperature of the heating furnace is controlled at 1210℃～1230℃, and the finishing temperature of the intermediate billet entering the finishing mill is controlled at 960℃～1020℃;

Width reduction control: When the slab width is not less than 30mm of the finished product width, the side pressure is set;

Phosphorus removal: Phosphorus removal is carried out before the roughing mill and the finishing mill, and also during the fourth pass of roughing;

Finishing rolling process water control: Use the roller anti-stripping water function and simultaneously start the reverse water spray between the stands to blow away impurities on the strip surface in time.

Preferably, in the roughing mill, the fourth pass speed is controlled at 3.8 m/s to 4.0 m/s.

Preferably, the steel tapping temperature of the heating furnace is controlled to be 1210°C or 1230°C.

Preferably, the finishing rolling temperature of the intermediate billet entering the finishing mill is controlled to be 960°C or 1020°C.

Preferably, the coiling temperature is controlled at 620°C to 650°C.

The second object of the present invention is to provide a cold-rolled raw material coil obtained by the above-mentioned control method.

The advantages and positive effects of the present invention are:

The present invention can effectively reduce or eliminate surface quality defects of the cold-rolled raw material coil and improve the overall quality of the product by comprehensively controlling the temperature, width reduction, phosphorus removal and use of finishing rolling process water of the cold-rolled raw material coil in the production process.

In view of the problem of surface quality defects of cold-rolled raw material coils, the present invention mainly solves it by optimizing the temperature system, the side pressure system, the phosphorus removal system and the use of process water in the finishing area. In the production process, in order to improve the stability of rolling, the temperature at the finishing entrance usually needs to be controlled between 1000°C and 1050°C. However, when the intermediate slab enters the finishing temperature range between 1030°C and 1080°C, it is the stage where iron oxide scale is most seriously generated. Therefore, after comprehensively considering the safety of the finishing equipment and the stability of rolling, it is necessary to reduce the temperature entering the finishing rolling to between 960°C and 1020°C.

In terms of the dephosphorization system, the conventional practice is to perform dephosphorization after the furnace, before the roughing mill and before the finishing mill. On this basis, the present invention adds a dephosphorization treatment in the fourth pass of rough rolling. This is mainly because the rolling time of the third and fourth passes is relatively long, and more iron oxide scale will be generated in this process. Therefore, adding a dephosphorization treatment in the fourth pass of rough rolling can effectively remove these iron oxide scales.

In addition, the use of anti-stripping water for finishing rolls can protect the rolls and prevent the oxide film on the roll surface from peeling off. The reverse water spray between the stands can promptly blow away the debris on the strip surface to prevent these debris from causing surface defects when the strip enters the next stand for rolling.

Through the above-mentioned comprehensive control measures, the present invention can greatly improve the surface quality of the cold-rolled raw material coil, eliminate or reduce surface quality defects, thereby improving the quality and market competitiveness of the product.

DETAILED DESCRIPTION

In order to make the above-mentioned purpose and design advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

The technical solution of the present invention is:

A method for effectively controlling surface quality defects of cold-rolled raw material coils involves a production process path of cold-rolled raw materials, which mainly includes key links such as a heating furnace, a roughing mill, a finishing mill, a laminar cooling device and a coiling device.

The control method mainly covers the following aspects:

The first is temperature control, which is a key step. The steel-out temperature of the heating furnace must be strictly controlled within the range of 1230℃~1250℃ according to internal control standards, and the temperature of the intermediate billet when entering the finishing rolling must be between 960℃~1020℃. This is the basis for ensuring the surface quality of the cold-rolled raw material coil.

The second is width reduction control. By applying large side pressure, the furnace-generated iron oxide scale on the surface of the slab can be effectively loosened. When the slab is dephosphorized again after side pressure, the iron oxide scale on the surface of the slab is more likely to fall off. Therefore, the side pressure setting needs to be based on the principle that the slab width is not less than 30mm of the finished product width.

Next is the dephosphorization system. This is to ensure the effect of high-pressure water dephosphorization. It is necessary to strengthen the inspection of the dephosphorization nozzles. Once they are blocked or worn, they need to be replaced in time. For steel grades with higher surface quality requirements, it is necessary to reduce the rolling speed of the odd-numbered rough rolling passes, extend the slab dephosphorization time, and simultaneously increase the dephosphorization of the fourth rough rolling pass.

Then there is the finishing rolling process water system. Establishing and maintaining the oxide film is the key to preventing the strip steel from having oxide scale defects. In order to prevent the oxide film of the rolls of the first four rolling mills from peeling off and pressing into the strip steel, causing surface defects, the roll anti-stripping water function needs to be activated, and the reverse water spray between the stands should be turned on simultaneously to blow away the impurities on the strip steel surface in time to prevent defects on the strip steel surface.

Speed control is for the rough rolling mill process, and the rough rolling speed needs to be accurately controlled to ensure surface quality.

Side pressure control is also aimed at the rough rolling mill process. By applying large side pressure, the iron oxide scale on the surface of the slab can be effectively loosened.

Finally, dephosphorization is carried out after the heating furnace, at the rough rolling mill, and at the entrance of the finishing mill. These need to be carried out in their respective processes to ensure the surface quality of the cold-rolled raw material coils.

The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims (6)

1. A method for controlling surface quality defects of a cold-rolled raw material coil, wherein the production process equipment of the cold-rolled raw material coil comprises a heating furnace, a roughing mill, a finishing mill, a laminar cooling device and a coiling device; characterized in that the control method comprises: Temperature control: The tapping temperature of the heating furnace is controlled at 1210℃～1230℃, and the finishing temperature of the intermediate billet entering the finishing mill is controlled at 960℃～1020℃; Width reduction control: When the slab width is not less than 30mm of the finished product width, the side pressure setting is performed; Phosphorus removal: Phosphorus removal is carried out before the roughing mill and the finishing mill, and also during the fourth pass of roughing; Finishing rolling process water control: Use the roller anti-stripping water function and simultaneously start the reverse water spray between the racks to blow away impurities on the strip surface in time. 2. The method for controlling surface quality defects of cold-rolled raw material coils according to claim 1 is characterized in that, in the rough rolling mill, a dephosphorization is added to the fourth pass and the speed is controlled at 3.8 m/s to 4.0 m/s. 3. The method for controlling surface quality defects of a cold-rolled raw material coil according to claim 1, characterized in that the steel tapping temperature of the heating furnace is controlled to be 1210°C or 1230°C. 4. The method for controlling surface quality defects of cold-rolled raw material coils according to claim 1, characterized in that the finishing temperature of the intermediate billet entering the finishing mill is controlled to be 960°C or 1020°C. 5. The method for controlling surface quality defects of cold-rolled raw material coil according to claim 1, characterized in that the coiling temperature is controlled at 620°C to 650°C. 6. A cold-rolled raw material coil, characterized in that it is obtained by the method for controlling surface quality defects of a cold-rolled raw material coil according to any one of claims 1 to 5.