25 January 2017

Advantages and disadvantages of hot rolling

Rolling is classified by the temperature of the metal rolled. The hot rolling process is only done when working at extremely high temperatures, hence the name is "hot rolling". It is used to break down imperfections from flat-rolled steel coils such as billets and ingots. Following the process, the hot coils can either be sold immediately as is or moved to the next cold rolling process due to technology advances.

The hot rolling process begins at high-temperature ranges and is generally used for the development of large deformations. As opposed to cold rolling mills which are processed with four vertical oriented rolls, hot rolling is done with two vertical rolls. The pressure and fast speed and high temperature are applied between these two rolls to reduce the material and make it stronger. Unfortunately, dimensions are not accurately obtained to the way this process occurs. Here, in this article, you can check it out the pros and cons of the hot rolling process one by one below.

Advantages of hot rolling :

  • Hot rolling can reduce energy consumption and costs considerably.
  • Hot rolling can improve the processing performance of metals and alloys because coarse grains during foundry are broken, the cracks are healed, casting defects are reduced and eliminated hence, cast microstructure is transformed into a deformed structure to improve processing properties. 
  • Hot rolling not only improves the efficiency of production but also creates conditions for increasing rolling speed and achieving continuous and automated rolling.
  • A porosity of metal is considerably minimized. 
  • Flow stresses are low so forces are relatively lower. 

Disadvantages of hot rolling :

  • Non-metallic inclusions inside the steel are pressed into thin sheets after hot rolling, causing delamination that deteriorates the tensile properties of the steel in the direction of thickness. 
  • The hot-rolled steel of various sections has residual stress caused by uneven cooling that has some influence on the performance of steel member under external force. Such as stability, deformation, fatigue and other aspects may have adverse effects.  
  • Hot rolling does not accurately control the mechanical properties required for the product, and microstructure and properties of the hot rolled product are not uniform. 
  • The strength index is lower than that of the cold working products and higher than fully annealed products. The plastic index is higher than cold working products and lower than fully annealed products. 
  • The thickness and dimension of the hot rolled product are difficult to control therefore, hot rolled products are generally used as blanks for cold rolling.