In the Rebar Rolling Line, How to Cool the Products?

In the steel rolling production line, the cooling bed is the main cooling equipment for rolled bar products, and the cooling wheel is the main cooling equipment for wire products. The role of the cooling bed and the cooling roller is to cool the high-temperature rolled piece above 800°C to below 150-100°C, so as to restore the inherent physical properties of the steel and facilitate the shear quality and subsequent operation.

For different products, cooling equipment and cooling methods are also different. So, in the steel rolling production line, what are the cooling methods of the product?

Cooling methods the following cooling methods are determined according to the chemical composition, structural state, usage, and possible defects after cooling the steel.

Natural Air Cooling

Natural air cooling refers to the natural cooling of hot-rolled steel in the atmosphere, usually on a special cooling bed. Natural air cooling is a cooling method commonly used in carbon structural steel, low alloy structural steel, high-quality carbon structural steel, and austenitic stainless steel. This cooling method generally does not affect the physical properties of the steel. However, it should be noted that the rolled material moves forward while cooling on the cooling bed, and it is required to minimize bending and scratches caused by the relative friction between the rolled material and the cooling bed.

Forced Rapid Cooling

However, forced rapid cooling generally adopts blowing, spraying, water spraying, and other methods, and its technological feature is to make the steel rapidly cool to a certain temperature within a certain period of time and then perform natural cooling. Accelerated cooling was first used to shorten the cooling time to reduce the area of the cooling bed, and later also had the following effects.

1. Refining the grains of hypoeutectoid steel and improving the comprehensive performance of materials;

2. Reduce or even eliminate the network structure of hypoeutectoid steel and hypereutectoid steel;

3. Use the high temperature after rolling and the processed grain structure to replace the quenching process or quenching self-tempering process of quenched and tempered steel to save energy and improve material properties;

4. Replace the heat treatment process before further processing of some steel materials, such as replacing the lead bath quenching before steel wire drawing (see sorbite treatment), etc.;

5. Use rapid cooling to remove or reduce the oxide scale on the surface of the rolled material, improve the surface quality of the rolled material and the metal yield, and reduce the pickling time and acid consumption before secondary processing.

Controlled Slow Cooling

Steels with strong stress sensitivity after cooling are generally cooled by controlled slow cooling, such as high-speed tool steel, martensitic stainless steel, high-alloy tool steel, and high-alloy structural steel. This cooling method can prevent steel structure changes and stress concentration to cause crack defects.

The post-rolling cooling process is a complex heat transfer process. During the cooling process, the production conditions such as cooling water flow state, water temperature, water level and ambient temperature, and other parameters are constantly changing, as well as the error of the measuring equipment, etc., will affect the temperature control accuracy of the cooling process.

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Created on Mar 6th 2023 00:11. Viewed 127 times.

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