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HOT ROLLING PROCESS• The starting material is usually large pieces of metal, like semi-finished casting products, such as slabs, blooms, and billets.• In continuous casting, rolling mill is mostly integrated to save energy.• for larger work pieces gas- or oil-fired soaking pit• for smaller work pieces induction heating.• a finishing temperature is defined (50 to 100 °C above the recrystallization temperature) If the temperature does drop below this temperature the material must be re-heated before more hot rolling.
HOT ROLLING PROCESS• Approximately 96% of steel is continuously cast (the remaining - ingots ).• After hot rolling the cooling should be done uniformly else residual stress is generated due to shrinkage that affects the mechanical properties.• Mill scale is the oxide layer formed on the surface due to reaction with atmosphere at high temperatures.• Pickling is done with HCl to remove this scale.
TERMS RELATED TO HR COIL• SPCC is a grade of commercial steel equivalent to JIS G3141. SPCC -SD/SB SD = standard dull finish SB = standard Bright finish• SPHC : Steel Plate Heat treated Commercial quality• HRB : Hot R• U- oxidation unspecified• A- aluminium killed• K- silicon aluminium killed• G- heat treatment and hot dipcoated