High-speed steel roll ring manufacturers: common failure forms and causes of rolls
The roll is a tool for plastic deformation of metal (rolled material), and it is also an important wearing part that determines the efficiency of the rolling mill and the quality of the rolled material. Rolls are an important part of rolling mills, which use the pressure generated by a pair or group of rolls to roll and grind steel. It mainly bears the influence of dynamic and static loads, wear and temperature changes during the rolling process.
There are two types of rolls we usually use, cold rolls and hot rolls.
There are many kinds of materials for cold rolled rolls, such as 9Cr, 9Cr2, 9Crv, 8CrMoV, etc. There are two requirements for this type of roller
1. The surface of the roller should be quenched.
2. The surface hardness should be HS45~105.
The material of hot rolling roll is generally 60CrMnMo, 55Mn2 and so on. Rollers of this type can be used in a wide range of fields. It can be used for the processing of section steel, bar, rebar, high-speed wire, seamless steel pipe, billet, etc. It withstands strong rolling forces, severe wear and thermal fatigue. In addition, hot rolls work at high temperatures, allowing diameter wear per unit of work, so surface hardness is not required, only high strength, toughness, and heat resistance are required. Hot rolling only adopts overall normalizing or quenching, and the surface hardness requires HB190~270 hardness.
The common failure forms and causes of rolls are as follows:
High-speed steel roll ring manufacturers: cracks.
The cracks of the rolls are mainly caused by the excessive local pressure of the rolls and the rapid cooling and heating of the rolls. On rolling mills, cracks can occur if the emulsion nozzles are clogged, resulting in poor local cooling of the rolls. Cracks are more likely to develop than in summer due to lower temperatures in winter.
High-speed steel roll ring manufacturers: peeling.
If the cracks continue to develop, lumps or flakes will form. Those with light peeling can be re-polished and reused, while those with severe peeling can be scrapped.
Manufacturer of high-speed steel roller rings: pitting.
The pit marking is mainly due to the fact that the strip welds or other impurities enter the rolling mill, so that the surface of the roll is marked with pits of different shapes. Generally scratched rollers should be replaced. When the quality of the strip weld is not good, it should be lifted and pressed down as the rolling operation passes the weld to prevent pitting.
High-speed steel roll ring manufacturers: sticky rolls.
The reason for the sticking of the roll is that there are broken parts, broken waves, broken edges and other phenomena during the cold rolling process, and due to the high pressure and high temperature, it is easy to form adhesion between the steel strip and the roll, resulting in less area damage to the roll. Through grinding, the roll surface can continue to be used after the cracks are eliminated, but the service life is obviously reduced, and the peeling accident is prone to occur in the future use.
High-speed steel roll ring manufacturers: Le roll.
The pull roll is mainly due to the excessive reduction of the strip steel thickness or slight folding, and the strip steel deviation caused by the thickness. When the roll is severely squeezed, it will stick to the roll and the strip will crack. When the rolls are light, there are marks on the strip and rolls.
High-speed steel roll ring manufacturers: Broken rolls.
The main reasons for roll breakage are overpressure (that is, excessive rolling pressure) and internal defects of the roll (non-metallic inclusions, air bubbles, etc.). ) and the stress field caused by the uneven temperature of the rollers.