For more than ten years, high-speed steel rolls have been widely used in plate and strip rolling mills in industrially developed countries, and my country’s Baosteel 1580mm rolling mill F1 ~ F5 stand work rolls have all used high-speed steel rolls, and the roll consumption of this rolling line has been reduced. to 0.4kg/t.
Subsequently, Angang Iron and Steel’s 1780mm rolling mill and Handan Iron and Steel’s 2100mm CSP rolling mill also used high-speed steel rolls, and both achieved good results. The grinding cycle of the rolls was three times that of the previous rolls. At present, many hot-rolled strip steel production lines in my country have successfully used high-speed steel rolls.
Although high-speed steel has become an ideal material for roll manufacturing today, various problems in the use of high-speed steel rolls in hot-rolled plates and strip mills have attracted attention.
For example, the high expansion coefficient and elastic modulus of high-speed steel cause the change of roll shape; high-speed steel has a large thermal conductivity and small specific heat capacity, which causes thermal stress and thermal cracks on the roll surface; high-speed steel rolls cause slippage during rolling questions etc.
It took nearly 5 years for Canada’s Dofasco Company and South Korea’s Pohang Company to summarize a complete set of experience in using high-speed steel rolls. It also took Baosteel 4 years to master the usage rules of high-speed steel rolls.
There are many hot-rolled narrow-strip mills in my country at this stage, but the effect of using high-speed steel rolls by most manufacturers is not ideal.
The main reasons are as follows: First, the narrow strip steel manufacturers use high-speed steel rolls for the finished product racks, unlike wide-band steel rolling mills, which are used in the first few stands of the finishing mill. Because the finished product racks are rolled at a low temperature, the roll surface is not very good. to form an oxide film;
The second is that the finished product rack is thin and the temperature of the rolled material is low, which is more prone to rolling accidents such as slippage and stacked steel;
The third is that the narrow strip steel manufacturer does not have a CNC grinding machine, and the original roll shape cannot meet the negative crown requirement;
The fourth is that after the rolls are put on the rolling mill, the amount of steel rolled at one time will be increased by 3 to 5 times; while the wide-band steel rolling mill is to cool down the rolls every rolling cycle, and continue to use the machine after the roll shape is restored. When rolling 3 Grind the roll after the cycle.
The high-speed steel roll produced by a certain company was once used in the finished frame of the medium and wide band rolling mill. Although the gradient distribution of the cooling water on the roll surface differs by more than 3 times, after one shift of rolling, the strip steel has obvious mid-waves. At this time, stop the machine immediately and change the roll. After the roll is cooled down, the roll surface is measured, and the convexity and concaveness of the steel surface have been restored to the state of the new roll, while the wear of the steel surface is only 0.01mm.
It can be seen that although the wear of the roll is very small, the roll cannot continue to be used. Therefore, in order to achieve the ideal use effect of high-speed steel rolls, it is necessary to change the concept of roll use and create the necessary conditions so that the advantages of high-speed steel rolls can be truly brought into play.