Rolling is the steel industry of the material process, is the mass production of steel material process, is the most important steel material forming method, more than 90% of the smelting steel through the rolling process to become available steel. The rolling sector directly faces various industries of the national economy, and is closely related to pillar industries of the national economy such as automobiles, construction, energy, transportation and machinery manufacturing, and is also closely related to people's lives. Due to the large number of steel production, variety, widely used in various sectors of the national economy, the rolling industry is one of the basic industries of national economic development.

In the rolling process, the metal billet is drawn between the rotating rolls, compressed and plastic deformation occurs. This process not only increases the length of the material and reduces the cross-section, but also gives the metal a certain size, shape and properties.

Hot rolling and cold rolling

Metal rolling can also be divided into hot rolling and cold rolling according to the state of the metal. Hot rolling is carried out at high temperatures, which can destroy the casting structure of the ingot, refine the grain of the steel, and eliminate the defects of the microstructure. Cold rolling is carried out at room temperature, usually with hot-rolled steel coil as raw material, after pickling to remove the oxide, continuous rolling, the finished product is rolled hard coil, with high strength and hardness, but poor toughness.

Product characteristics

Due to the action of high temperature and pressure, the structure of hot-rolled products is dense and the mechanical properties are improved. However, hot rolled steel may have problems with delamination and non-metallic inclusions. Cold-rolled products are cold hardening caused by continuous cold deformation, resulting in increased strength and hardness, decreased toughness and plastic index, and deterioration of stamping performance.

The equipment and tools of the metal rolling process are the key to ensure efficient and high quality production. Here is some basic information about metal rolling equipment and tools, including mill types and characteristics, roll design and material selection, and the functions of auxiliary equipment.

Common types of rolling mills

Two-high mill

This is the simplest and most widely used type of mill, consisting of two rolls placed horizontally. It is suitable for small operations and initial thinning of metal materials.

Four-high mill

There are two large diameter work rolls and two small diameter support rolls. This structure can provide higher rigidity and precision, suitable for thinner materials and high-precision applications.

Six-high mill

It combines the characteristics of a four-high mill and adds more back-up rolls to enhance the stiffness of the overall structure, mainly for high-precision product manufacturing processes.

Multi-roll mill

For example, 12-high, 20-high mills, they are used for specific applications, such as very thin foil or materials requiring extremely high flatness.

Parameter control of metal rolling

In metal rolling process, parameter control is the key factor to ensure product quality and improve production efficiency. The following is an overview of several main rolling parameters and their control methods:

Rolling speed

Rolling speed directly affects production efficiency and product quality. Excessive speed may lead to changes in the internal structure of the material and affect the mechanical properties of the product; Too low a speed will reduce production efficiency.

Adjust the rolling speed according to the properties of the metal material, the thickness and the requirements of the final product. For example, for materials prone to cracking, a lower rolling speed should be selected to reduce defects.

Rolling temperature

The deformation capacity, mechanical properties and surface quality of the material are significantly affected by the rolling temperature. The appropriate temperature can improve the plasticity of the material and reduce cracks and defects.

Control the heating and cooling process to ensure that the material remains at the right temperature throughout the rolling process. For hot rolling, a higher temperature is usually required to increase the plasticity of the material; For cold rolling, it needs to be carried out at a lower temperature to maintain the strength of the material.

Rolling pressure

Rolling pressure determines the degree of deformation of metal materials. Improper pressure may cause the material to deform unevenly or produce cracks.

Select the appropriate rolling pressure according to the hardness and thickness of the material. Use force sensors and feedback control systems to monitor and adjust rolling pressures in real time to ensure uniform material deformation.

Rolling pass and reduction amount

The rolling pass and the reduction amount of each pass directly affect the dimensional accuracy and surface quality of the final product. Multiple passes with a small reduction usually result in better surface quality, but may reduce production efficiency.

Optimize the rolling strategy, and determine the best pass number and reduction distribution through experiments to achieve the dual goals of efficient production and high quality output.

The control of these parameters not only relies on modern automation equipment and precise sensing technology, but also requires the operator to adjust according to the actual production situation. By precisely controlling these parameters, the efficiency of the metal rolling process and product quality can be significantly improved to meet the strict requirements of different industrial applications.

Quality control of rolling

The quality control of metal rolling process is the key link to ensure that the products meet the technical specifications and customer needs. The following are the main quality control methods:

Surface quality inspection

Surface defects such as scratches, oxide, wrinkles, etc., are usually caused by poor roll surface quality or improper rolling lubricants.

Use visual inspection and non-destructive testing techniques, such as eddy current inspection, infrared inspection, etc., to assess and guarantee the quality of material surfaces.

Dimensional accuracy detection

Dimensional accuracy includes thickness, width, flatness and other parameters, and its control is very important for the subsequent processing of the product.

High-precision instruments such as thickness gauge, laser width gauge and flat plate degree detector are used for online monitoring and control to ensure that the product size meets the standard.

Mechanical property test

Mechanical properties (such as tensile strength, yield strength, elongation, etc.) directly affect the performance of the material.

The mechanical properties of materials are regularly tested by tensile test, hardness test and other methods to ensure that they meet engineering and design requirements.

Metallographic tissue testing

The microstructure determines the microstructure and macroscopic properties of metal materials, such as grain size and phase composition.

Metallographic analysis is performed using optical or electron microscopy to evaluate the microstructure and heat treatment effect of the material.

Articulation

In this paper, the metal rolling process is briefly introduced, and the next article will be based on the characteristics of the rolled metal.