Hot rolled steel production process

Hot rolling is a metal processing technology, which is relative to cold rolling. Cold rolling is rolling below the recrystallization temperature, while hot rolling is rolling above the recrystallization temperature. To put it simply, a piece of steel billet is heated and rolled several times, then trimmed and straightened into a steel plate. This is called hot rolling.

Hot rolling feature

1. Low energy consumption, good plastic processing, low deformation resistance, work hardening is not obvious, easy rolling, reducing the energy consumption required for metal deformation.

2. Hot rolling usually adopts large ingot and large reduction rolling, which has fast production rhythm and large output, which creates conditions for large-scale production.

3. Through hot rolling, the cast structure is transformed into a processing structure, and the plasticity of the material is greatly improved through the transformation of the structure.

4. The characteristics of the rolling method determine the anisotropy of the properties of the rolled sheet. First, the longitudinal, transverse and high direction of the material have obvious performance differences, and second, there is a deformation texture and recrystallization texture, and there is an obvious direction in the punching performance.

Production technology

There are many ways of hot rolling, but our common is longitudinal rolling, that is, rolling along the length of the ingot, in the rolling process is mainly the interaction between the roll, the rolled piece and the emulsion process, in addition to the vertical roll edge rolling outside the roll gap, coiling tension control.

Factors affecting rolling

1. Parameters

The main parameters affected by this factor are roll shape and surface roughness, and the formulation of these two parameters can be determined according to actual experience, according to the production process requirements of the mill, such as the selection of the roughness of the roll surface of the hot mill, which is conducive to biting into the rolling process to prevent slipping, but also to prevent the roughness of the roll surface from affecting the surface quality of the product.

2. Hot rolling temperature

The hot rolling temperature includes the opening rolling temperature and the final rolling temperature. The opening rolling temperature is determined mainly according to about 80% of the solid phase line temperature in the alloy phase diagram, and the final rolling temperature is determined according to the plastic diagram of the alloy, which is generally required to be controlled above the recrystallization temperature of the alloy.

3. Rolling speed

In general, in order to improve production efficiency and ensure a reasonable final rolling temperature, high-speed rolling should be used as far as possible within the scope allowed by the equipment, and in the actual production, different rolling speeds should be determined according to different rolling stages, such as the beginning of rolling stage, tiling stage, coiling stage, etc., different stages can be rolled at different speeds.

4. Hot rolling reduction system

The determination of the hot rolling reduction system mainly includes the determination of the total hot rolling processing rate and the pass processing rate, and the determination principle of the total hot rolling processing rate is:

1) The properties of alloy materials, such as pure aluminum, high temperature plastic range is wide, hot rolling brittleness is small, deformation resistance is low, so the total processing rate is large, but hard aluminum alloy, hot rolling temperature range is narrow, hot brittleness tendency is large, its total processing rate is usually smaller than soft aluminum alloy.

2) To meet the requirements of product surface quality and performance, such as the supply of cold-rolled billets, the total processing rate of hot rolling should be enough cold deformation to help control product performance and obtain good cold-rolled surface quality.

3) Mill capacity and equipment conditions, the greater the difference between rolling thickness and working opening of the mill, the thicker the ingot, the greater the total processing rate of hot rolling, but the thickness of the ingot is limited by the opening of the mill and the length of the roller table.

Hot rolling applications

1. Suitable for general structural steel and engineering hot-rolled steel plates and steel strips, and can be used for welded pipes, cold-rolled materials, bicycle parts, and important welding, riveting, and bolting components.

2. Used for cold-rolled and deep-drawn products.

3. Make stamping and structural parts for automobiles, engineering hoisting machinery, and small light industrial and civil machinery.

4. Make containers and exposed metal structural parts.

5. Welded pipes and steel structures.

6. Pipelines for transporting oil and natural gas.

7. Automobile beams and beams.

8. Special steel belt for automobile wheels.

9. Structural anti-skid plates, stairs, ladder treads, etc.