Rolling is a process used in the metalworking industry that shapes the material by applying a compressive force through a set of rolls, transforming the material into desired forms cross sectional shape. Rolling is used to manufacture several products, such as sheet and plate metals, wire, railroad rails, pipes, tubes, bars, and more.
The process of rolling a material into a desired shape begins with the selection of the appropriate rolling mill, which can range in size from small units that can only handle a few sectors of material, to large rolling mills capable of producing hundreds of tons of product per day. The rolling mill can contain three, four, or five rolls, with each roll having a different business profile. Depending on the product to be rolled, the rolls are typically made of either steel or cast iron.
The importance of roll profile lies in the fact that the roll profile affects the shape of the material as it passes through the mill. Prior to the rolling process, the roll profile is determined based on what the desired end product must look like. By changing the roll profile, the product can be given different shapes such as tube or rectangle, as well as different surface textures, such as rough or finished.
Once the end product is determined and the roll profile is chosen, the material is placed in the rolling mill. Here, the material is sent between the rolls, where it is subjected to a series of compressive forces that deform it into the desired shape, as set by the roll profile. In addition to changing the shape of the material, rolling also increases the strength and hardness of the material, improving its overall quality.
During the rolling process, temperature control is essential, as the material must be properly heated in order to ensure the desired properties and cross sectional shape are realized. To this end, the rolls are often heated to temperatures between 750° - 850° Celsius to ensure an even spread of heat, and thus uniformity, throughout the material.
Once the material has been properly heated and rolled, it is often necessary to carry out a process known as post-rolling. This is done to ensure the product has achieved the desired shape and properties, and also removes inconsistencies such as folds that may have been created during the initial rolling process.
The post-rolling process typically begins with a series of grinding operations. Here, the material is put through a fine grinding procedure to further equalize the grain size of the product and remove any remaining folds. The material is then threaded and draw-formed to give the desired grain boundaries and finally, the cross-sectional shape is finished before the material is subjected to annealing.
Annealing is a process wherein the material is heated and cooled in order to relieve internal stresses and bring about even further improvement in strength, as well as increase the hardness of the product. Once complete, the difference between the cross-sectional shapes of the pre- and post-rolled material are evident, with the post-rolled product being smoother, stronger, and more consistent in terms of grain size than the pre-processed material.
In conclusion, rolling metal is a complex process which involves a precise combination of roll profile selection, temperature control, and post-rolling operations in order to produce the desired end product. By carefully controlling the parameters of the rolling process, a range of products with different shapes, textures, and strengths can be created.
