Rolling

• METHOD: stock metal (/material) is passed through sets of rollers to reduce the thickness of the material.
• 2 types of rolling: hot rolling and cold rolling
• What is the difference between hot and rolling?

  Hot rolling – metal is heated above recrystallisation temperature

  Cold rolling – metal heated below crystallisation temperature.
• Uses: structural steel members – I beams for construction industry, metal stock forms – angle, bar plate and channel, or rail for the railway.  
• Effect / benefits of hot rolling:

  -          mechanical properties are uniform throughout the material

  -          no deformation or stresses that could lead to faults
• Effect/ benefits of cold rolling:

  Tighter tolerance due to lack to lack of carbon deposits formed, which also provide a better finish.
• Disadvantages of hot rolling:

  Surface is generally covered with carbon deposits which are removed via aid pickling, more generous tolerances.
• Uses of cold-rolled materials: home appliances, filling cabinets, chairs, steel, drums, electrical cabinet, container and sauce pans.
• What do schools and colleges use cold-rolled metal for?

  Bench roller – tubes from sheet metal

  -          hoops from small diameter