Cold Rolling Fracture of Steel Billets Surface
Cold rolling is a major steel forming process used to produce sheet and strip product. The process consists of reducing the thickness and/or changing the cross section of a material. The cold rolling process is usually used to improve the mechanical properties of steel, particularly its surface properties, which are important for many end-use applications. However, the process also has certain drawbacks, such as the possibility of generating fractures on steel billets surfaces. This paper discusses the causes and consequences of cold rolling fracture of steel billets.
When steel billets are cold rolled, the surface area is greatly reduced. The metal must be strained so that the necessary surface area is achieved. This causes strain, resulting in both macro and micro-deformations. These deformations can create strain-induced micro-cracks in the material. This phenomena is known as cold rolling fracture.
Cold rolling fracture occurs when the material is deformed beyond its elastic limit. This results in micro-cracks on the surface and in the pockets of the billet. These fractures range in size and depth, depending on the severity of the cold rolling. The micro-cracks reduce the strength and ductility of the material and can be detrimental to the structural integrity of the billet. Furthermore, these cracks also affect the surface properties as they decrease the adhesive properties of the material.
In order to address these problems, steel manufacturers use various treatments to reduce the occurrence of cold rolling fracture. These treatments range from simpler processes such as annealing to more complex treatments like carburizing. Annealing is a heat treatment process in which the material is heated and then allowed to cool slowly. This process increases the ductility of the material, which reduces the risk of fractures. Carburizing is a process in which a carbon-bearing gas is applied on the material. This gas binds with the metal, forming a hard and strong shell on the surface, which increases the strength and reduces the risk of fractures.
Cold rolling fracture of steel billets is a common problem that can have a significant effect on the strength and ductility of the material. The risk of fractures can be reduced by using treatments such as annealing and carburizing. These treatments help to improve the surface properties of the material, which in turn helps to reduce the risk of cold rolling fracture and improve the strength of the billet.
