Keyword: product type; location; function; material; manufacturing method
The main working parts and tools on a rolling mill that cause continuous plastic deformation of metals. The roll is mainly composed of three parts: roll body, roll neck and shaft head. The roll body is the middle part of the roll that actually participates in rolling the metal. It has a smooth cylindrical or grooved surface. The roll neck is installed in the bearing, and the rolling force is transmitted to the stand through the bearing seat and the pressing device. The shaft head of the transmission end is connected with the gear seat through the connecting shaft, and transmits the rotating torque of the motor to the roller. The rolls can be arranged in the form of two rolls, three rolls, four rolls or multiple rolls in the rolling stand.
A large number of alloying elements were used in the rolls after the Second World War. This is the development of large-scale, continuous, high-speed, and automated steel rolling equipment, as well as the improvement of rolling material strength and deformation resistance. Higher requirements for roll performance the result of. During this period, semi-steel rolls and ductile iron rolls appeared successively. After the 1960s, powdered tungsten carbide rolls were successfully developed. In the early 1970s, the centrifugal casting technology and differential temperature heat treatment technology of rolls, which were widely promoted in Japan and Europe, significantly improved the comprehensive performance of strip rolls. Composite high-chromium cast iron rolls are also successfully used in hot-strip mills. During the same period, forged white iron and semi-steel rolls were applied in Japan. In the 1980s, Europe introduced high-chromium steel rolls and cold rolls with ultra-deep hardened layers, as well as special alloy cast iron rolls for finishing small sections and wire rods. The development of contemporary steel rolling technology has prompted the development of higher performance rolls. The cores produced by centrifugal casting method and new composite methods such as continuous casting composite method (CPC method), spray deposition method (Osprey method), electroslag welding method and hot isostatic pressing method are forged steel or ductile graphite with good strength and toughness Cast iron, composite rolls with high-speed steel outer layers and cermet rolls have been applied in new-generation profile, wire and strip mills in Europe and Japan, respectively.
The variety and manufacturing process of rolls are constantly developing with the advancement of metallurgical technology and the evolution of rolling equipment. Low-strength grey cast iron rolls were used for rolling soft non-ferrous metals in the Middle Ages. In the middle of the 18th century, Britain mastered the production technology of chilled cast iron rolls for rolling steel plates. The progress of European steelmaking technology in the second half of the 19th century required the rolling of larger tonnage ingots, and the strength of either gray cast iron or chilled cast iron rolls could no longer meet the requirements. Ordinary cast steel rolls with a carbon content of 0.4% to 0.6% were born accordingly. The appearance of heavy forging equipment has further improved the strength and toughness of forging rolls of this composition. The use of alloying elements and the introduction of heat treatment in the early 20th century significantly improved the wear resistance and toughness of cast and forged steel hot and cold rolls. The addition of molybdenum to cast iron rolls for hot-rolled strip improves the surface quality of the rolled material. The composite casting by the flushing method significantly increases the core strength of the casting roll.
China began to mass-produce casting rolls in the 1930s, but there were very few varieties. In the late 1950s, China’s first professional roll factory was established in Xingtai, Hebei. In 1958, Anshan Iron and Steel Company first trial-manufactured and used 1050 large ductile iron rolls for blooming. In the 1960s, it successfully manufactured cold-rolled work rolls and large-scale forged steel rolls. In the late 1970s, Taiyuan Iron and Steel Company and Beijing Iron and Steel Research Institute jointly successfully trial-produced centrifugally cast cast iron rolls for furnace coil mills and hot continuous rolling strip mills, and Xingtai Metallurgical Machinery Roll Co., Ltd. successfully trial-produced semi-steel work rolls for hot strip rolling mills. and work rolls for cold-rolled wide-band steel mills. In the 1980s, China successively developed new varieties of large forged steel backup rolls, forged semi-steel and forged white cast iron rolls, powdered tungsten carbide roll rings, and high chromium cast iron rolls. By the 1990s, China’s roll production had basically met domestic needs and some were exported, but the varieties needed to be increased and the quality had to be improved.
There are many classification methods of rolls, mainly:
(1) According to the product type, there are strip steel rolls, section steel rolls, wire rod rolls, etc.;
(2) According to the position of the rolls in the rolling mill series, there are billet rolls, rough rolls, finishing rolls, etc.;
(3) According to the functions of the rolls, there are scale breaking rolls, perforation rolls, leveling rolls, etc.;
(4) According to the roll material, there are steel rolls, cast iron rolls, cemented carbide rolls, ceramic rolls, etc.;
(5) According to the manufacturing method, there are casting rolls, forging rolls, surfacing rolls, sleeve rolls, etc.;
(6) According to the state of the rolled steel, there are hot rolls and cold rolls. Various classifications can be combined to make the rolls have more specific meanings, such as centrifugally cast high-chromium cast iron work rolls for hot-rolled strip.