In recent years, cold rolled steel sheet and strip have been developed greatly. The outlet speed of the end stand of the tandem cold mill can reach 25-41.7m/s. In order to increase production, the volume of cold coil has reached 60t. A tandem cold mill can produce 2.5 million tons annually.
In the strip cold tandem rolling mill, the hydraulic bending roll device or the pumping work roll device are widely used to improve the shape of the strip. Due to the high requirement of thickness tolerance of cold rolling strip, in order to increase the corresponding speed of the press device of the mill, the full hydraulic press device and automatic thickness control device are adopted in the cold rolling machine. Computer control is realized for high speed and high output strip cold tandem mill.
It should be noted that since 1979, there has been a total continuous cold tandem mill (figure 1-6). This kind of rolling mill can realize continuous rolling as long as the first time the material is put through the belt. The head of the subsequent coil is welded together with the tail of the previous coil by welding machine. After being rolled, it is separated by flying shear machine and the strip is rolled alternately by two coiler machines. Even when the roller is changed, the strip remains in the mill and can be rolled immediately. The use of full continuous cold rolling mill can increase productivity by 30%-50%, product quality and audience rating are also improved.
In the past 10 years, the production technology and equipment of cold rolled strip have a new development:
1) pickling and cold rolling combined unit. This kind of unit changed the traditional cold rolling production to separate the pickling and steel rolling processes, and combined into a unit. Which can improve the yield of 1% 3% acid pickling, cold rolling process, improve the machine production 30% to 50%, the decrease of the intermediate warehouse, 5000-5000 ㎡, and reduce the investment and production cost, etc.
2) shape control technology. Hydraulic bending roll technology is widely applied in tandem cold rolling mill, and plate shape instrument and sensitive hydraulic system are set up to improve the technology of cold running.
3) the application of continuous annealing and full-hydrogen cover annealing with the rapid development of various coating and plating production technologies, as well as the emergence of many new production lines and new equipment, has led to the development of steel rolling machinery in these fields.
4) strip continuous casting - cold rolling process. The strip casting machine can enter the cold rolling mill to produce cold rolled strip without hot rolling or slightly hot rolling (1-2 racks). This process will be further improved and popularized in the future.