During the cold rolling process, any influence on the rolling pressure, original roll gap, tension and oil film thickness of the rolling equipment will affect the actual strip thickness difference. The main reasons for the increase throughout the year are as follows.
The influence of temperature change
The influence of spare parts temperature change on the thickness fluctuation of the strip of the rolling equipment is essentially the influence of temperature difference on thickness fluctuation. The temperature fluctuation mainly causes the thickness difference by affecting the metal deformation resistance and friction factor.
The influence of tension change
Tension changes the metal deformation resistance of the rolling equipment by affecting the tensile state, thereby causing the thickness to change. In addition to affecting the thickness of the steel head and tail, the change of metallurgical spare parts tension also affects the thickness of other parts. When the tension is too large, it will not only affect the thickness, but also change the width. Therefore, in the hot rolling process, continuous small tension rolling of micro-loop is generally used, while cold rolling is carried out in a cold state, and the material processing causes great deformation resistance.
It is difficult to obtain the corresponding reduction rate by only adjusting the tension of the rolling roll equipment to change the rolling force, and it is necessary to increase the tension between the rolling mills for rolling. High tension is the characteristic of cold rolling production tension. The functions of tension include: reducing the rolling force and rolling tension; preventing the strip from running off; controlling the strip rolling shape and controlling the strip thickness.
The influence of speed change
The speed mainly changes the rolling pressure and the amount of pressure reduction through the rib force, deformation resistance and bearing oil film thickness.
The influence of roll gap change
When rolling strip, the roll gap of the rolling equipment will change due to the thermal expansion of the rolling mill components, the fatigue of the roll gap and the eccentricity of the rolls, which directly affects the actual rolling thickness change. The periodic change of the roll gap caused by the eccentricity of the rolls and bearings of the metallurgical spare parts will cause the rolling thickness of the rolling equipment to change under high-speed rolling.
In addition to the influencing factors, the fluctuation of the incoming material thickness and mechanical properties also causes the strip thickness to change through the change of rolling pressure. In addition, the calculation error of the metallurgical spare parts model setting, the accuracy of the measuring instrument and the design of the above system structure and control parameters also affect the thickness accuracy of the strip.
In addition, the users of medium and thick plate mill rolls can also conduct research on the rolling products, rolls and mill operating parameters of the steel rolling equipment under the existing conditions, and adopt equipment and process means to eliminate or reduce roll spalling. For example, a 2800 medium and thick plate mill uses the variable contact rolling technology principle and independently develops the automatic variable contact support roll P volume R technology and the positioning special work roll PWR technology, which eliminates roll spalling, reduces roll consumption, and improves product quality and mill productivity.
