Rolling Process Notes

Overview of Rolling Process

• Involves drawing workpiece through regulated opening of two rotating cylindrical rolls.
• Achieves reduction in thickness of the workpiece.
• Workpiece is subjected to compressive forces, leading to plastic deformation.
• Cross-section decreases while length increases; total volume remains constant.
• Main metalworking process, suitable for mass production.
• Close control of final product is possible.

Key Components

• Cylindrical Rollers:
  • Supported on bearings.
  • Driven by a powerful motor.
  • Gap between rolls is adjustable (referred to as roll gap or regulated opening).
• Friction: Dominates the rolling process, inducing direct compressive stress.

Conditions for Rolling

• Hot Rolling:
  • Conducted above the recrystallization temperature of the metal.
• Cold Rolling:
  • Conducted below the recrystallization temperature of the metal.

Products of Rolling

• Components produced have higher mechanical properties than cast products.
• Examples include:
  • Slabs, Sheets, Bars, Rods
  • Structural Components: I, U, and L sections in long lengths.

Steps in the Rolling Process

1. Starting Material:
   • Ingot obtained via metal die.
   • Ingot prepared by melting metal in a furnace, pouring molten metal into a die, and allowing it to cool.
2. Processing Ingot:
   • Ingot is then passed through rolls to produce final products.

Classification of Rolling Process

1. Based on Temperature:

   • Hot Rolling:
     • Converts ingot to slab, bloom, and billet.
     • Slab to plates, sheets, strips; bloom to channels, rails, beams; billet to rods and bars.
     • Used for heavy/thick sections with poor surface finish but uniform mechanical properties.
   • Cold Rolling:
     • Converts small sections (plates to sheets, sheets to foils, bars to wires).
     • Achieves good surface finish and enhanced properties.

2. Based on Roll Arrangement:

   • Minimum of 2 rolls required for rolling.
   • Types of roll arrangements:
     • 2 High Roll Mill: 2 rolls used.
     • 3 High Roll Mill: 3 rolls used.
     • 4 High Roll Mill: 4 rolls used.
     • Cluster Roll Mill: Several rolls used together.
     • Planetary Roll Mill: Rolls arranged in planetary motion.
     • Tandem Roll Mill: Continuous arrangement for continuous rolling.
     • Sendzimir Roll Mill: Similar to cluster mill but with more rolls for greater reduction.

Conclusion

• Understanding of rolling process is essential for metalworking.
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