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Technical realization of cast iron roll

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Technical realization of cast iron roll

  • Time of issue:2022-04-30 12:32

Technical realization of cast iron roll

  • Time of issue:2022-04-30 12:32
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The present invention relates to a process for producing cast iron rolls  for rolling mills with excellent durability , and to rolls produced by the process. More specifically, cast iron rolls can introduce sulfur as a connecting element into high-chromium white cast iron and multi - component white cast iron, controllably form sulfide phase particles in the microstructure, and use these materials to manufacture high-use rolling mill cast rolls, So, let's learn about the technical realization of cast iron rolls!

  Technical implementation of cast iron rolls:

  Cast iron rolls are tools used in the rolling process to form flat, long articles of metallic material, mainly steel. Like any forming tool, the cast iron rolls, which are in direct contact with these formed products, increase in surface aging during use and then return to the surface's initial condition after a period of use. This restoration is achieved by mechanically removing the aged surface layer, requiring the aged rolls to be pulled out and the mill stopped for replacement with newly repaired rolls. Therefore, the qual ity and productivity of the rolling process are closely related to the performance of the rolling mill rolls. The quality of rolled products is primarily determined by the accuracy and reproducibility of the shape, and of the roll surface.

  Stages of cast iron rolls use linearly arranged roll assemblies. This is also known as the finishing mill. The number of rolling mill stands can vary according to the function of the design and the significance of the rolling mill itself. Rolls of different materials were all so used due to the difference in aging coefficient between the upper roll and the end roll bracket. Cast iron roll aging is a process characterized by several distinct wear modes of wear, oxidation, adhesion and thermal fatigue acting simultaneously. However, one or both of these Loss modes in each stand of cast iron rolls are evident in the top stand, where friction and sticking are evident.Another disadvantage of existing finishing mills with rolls is that, at the same time as the aging of the cast iron roll surfaces, unexpected damages due to operational accidents of the finishing mill, such as adhesion of the rolling strip to the rollers, unstable surfaces Diffusion or cracking of the surface layer of the last roll, mill operation stopped and roll removed

  Due to the two working characteristics of the cast iron roll stand, the upper roll determines the lower rolling temperature susceptible to this damage, the low kinetics of the oxide structure on the roll surface, which compromises the performance of the roll by anti-adhesion; rolling Low thickness of the belt. Mill rolls designed for finishing mills tend to be bimetallic castings consisting of an "outer cover" of wear-resistant alloy and a "core" of ductile or gray iron. Generally, the process used in this bimetallic roller product is centrifugal casting in the mold, so that the protective layer material flows into the mold, under the action of centrifugal force,

  Cast iron rolls are necessary to prevent the formation of pearlite during cooling after casting. The long life of roll chilled cast iron suitable for rolling mill stands is due to the fact that its microstructure exhibits, as of date, a coordinated scheme of die wear resist ance , anti-sticking, and unstable propagation of graphite-induced microcracks. It can be seen that graphite acts as a lubricant on the contact surface of the roll or rolling strip, which reduces the stress concentration at the end of the micro-crack and reduces its diffusion speed. Some notable developments have been implemented in the line/process of hot strip mill end stand rolls. Materials based on the same concept, typically chilled cast iron, can be used.This involves the addition of alloying elements to form hard secondary phase particles that contain only dispersed fine carbides. There are also variations in cast iron roll consolidation techniques to achieve finer structures. Manufacturers strive to meet the high wear resistance needs of users of this roll by using hard alloying elements to form eutectics and/or secondary carbides harder than M3C, while maintaining other characteristic parameters. However, it has been found that reducing the fixation resistance and unstable diffusion of microcracks has the opposite effect in order to promo te the reduction of the graphite structure.

  The presence of niobium in cast iron rolls promotes the formation of primary carbide NbC free particles, increasing hardness without affecting the graphite structure, thereby increasing wear resistance, maintaining resistance to adhesion and unstable diffusion of microcracks (carbide NbC Structure formation occurs at higher temperatures than the formation of graphitic structures, so there is no competition between them). However, since the addition of niobium is actually about 0.6%, a high content means that the pouring temperature needs to be increased when casting the roll, which is unrealistic.This is because the addition limits the increase in wear resistance, the volume ratio of eutectic carbide NbC in the microstructure is limited to less than 1%, and there is a lack of precipitation of carbide NbC in the mold.

  The above is the technical realization of cast iron rolls . If you want to know more, please feel free to contact us!

 

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