We need to understand the purpose of rolling steel，most of which are to obtain the steel of the required shape and size, and secondly to change the internal structural quality of the steel and improve its mechanical processing performance.

Secondly, we need to understand the rolling method. According to the different rolling temperatures, it can be divided into hot rolling and cold rolling; according to the relative motion relationship between rolling piece and mill roll during rolling, it can be divided into vertical rolling, horizontal rolling and skew rolling. According to the forming characteristics of the rolled products, it can be divided into general rolling and special rolling. Due to the variety of rolling products, there are also a small number of products that need to be rolled over several times. 　

From the metallurgical point of view, the boundary between hot rolling and cold rolling should be from the metal recrystallization temperature is generally between 450℃ to 600℃, even if it is higher than 450℃ to 600℃, it also belongs to the range of hot rolling. The rolling temperature is less than 450 to 6 Baidu and the rolling is in the range of cold rolling. In the rolling steel production, the rolling is generally performed by heating the rolled piece to 1,100℃ to 1,250℃, and the rolling is called hot rolling, while rolling at normal temperature is called cold rolling. Cold rolling is suitable for rolling steels that require precise dimensions, smooth surface, and good mechanical processing properties. It uses hot-rolled semi-finished products or finished products as raw materials, and is rolled and produced by cold rolling at room temperature. 　　

1) Vertical rolling: The rolled piece is obtained by rolling two mill rolls in opposite directions. During rolling, the rolled piece moves forward through the gap (or hole type) between the rolls, and its moving direction is perpendicular to the roll axis. Longitudinal rolling is the most common method of rolling. 　　

2) Horizontal rolling: The rolled piece is rolled between two rolls of the same direction of rotation, parallel to the axis of the roll and opposite to the direction of rotation of the rolls, and the rolling piece is subjected to pressure processing only in the radial direction. Horizontal rolling can produce shaft products in various shapes. 　　

3) Skew rolling: The rolled piece is processed between two rolls having the same direction of rotation and an angle of the axis. The rolling stock is rotated forward during the rolling process. Skew rolling is used to produce seamless steel pipes (perforations) and steel balls.