In the mid-20th century, due to war and post-war reconstruction, industrial countries needed a large amount of wire, which led to the rapid development of wire rolling mills. In the mid-1960s, the emergence of high-speed non twisted wire rod finishing mills and the Stelmo controlled cooling process pushed the world’s wire rod production technology to a new stage.
In 1987, the high-speed wire rod production line of Ma Steel was completed and put into operation, marking the farewell of China’s wire rod production to the “double double” and the path towards a high-speed and irreversible world common development. Afterwards, the equipment level and rolling technology of wire rod mills underwent fundamental changes, and high-speed torsion free mills became the mainstream of wire rod production in China.
High speed wire rod rolling mill has the characteristics of fast rolling speed, high product accuracy, good surface quality, large rolling disc, and no torsion or slight tension on the entire rolling line. High speed wire rod rolling mill is composed of rough rolling unit, intermediate rolling unit, pre finishing rolling unit, and finishing rolling unit, usually with a total rolling line of 28-30 frames.
The roughing mill unit is generally composed of 4-8 stands. Due to the high starting temperature, large cross-section, and deep rolling grooves of the rolling rolls, the rolling rolls used for the roughing mill stand should have good resistance to breakage, thermal cracking, wear resistance, and good biting performance. Usually, the rough rolling mill adopts pearlite ductile iron rollers with a hardness of HSD 45-55 or alloy semi-steel rollers with a hardness of HSD 45-50.
The rollers of the intermediate rolling mill generally require good wear resistance and surface roughness resistance, and there is not much difference in material selection. Therefore, the rolling mill in high-speed wire rod rolling mills generally uses pearlite ductile iron rolls with a hardness of HSD 60-70 or alloy infinitely chilled ductile iron rolls, which is both economical and practical.
The pre precision rolling unit of the high-speed wire rod mill can reduce rolling accidents during precision rolling and improve the dimensional accuracy of the finished wire rod. Therefore, the principle of selecting roll materials for the pre precision rolling unit should be that the rolls used for the unit can play a role in connecting the past and the future, and the main advantage should be to ensure the wear resistance of the rolls.
Foreign high-speed wire rod mills have a wide selection of materials for the roll rings of pre finishing rolling units. Some manufacturers use tungsten carbide hard alloy roll rings, which have good wear resistance but low strength and may also cause fracture. The wear resistance of centrifugal composite rings and high-speed steel rolling rings is three times higher than that of high nickel chromium platinum infinite cold hard cast iron, and their strength is higher than that of tungsten carbide hard alloy rolling rings, while their prices are lower. Therefore, centrifugal composite rolling rings and high-speed steel rolling rings will be the preferred materials for pre precision rolling mill rolls or rolling rings in the future.
The precision rolling unit of high-speed wire rolling mill is an important factor to ensure high-precision rolling of wire. Therefore, the precision rolling unit of high-speed wire rolling mill must use tungsten carbide hard alloy roller rings, otherwise the rolling speed and wear resistance of the roller rings will not be guaranteed. So far, there is no material that can replace the tungsten carbide hard alloy roller rings of the high-speed wire rod rolling mill finishing mill.
