1. Overview of Blooming Mill

A Blooming Mill is a type of heavy-duty Rolling Mill used in steel and metal production plants for converting ingots or continuous cast slabs into semi-finished products such as blooms, billets, or slabs.
It serves as the primary stage of metal forming in the rolling process, where large ingots are broken down into smaller, more manageable shapes for further processing in intermediate or finishing mills.

Blooming mills are typically characterized by large rolling forces, heavy-duty stands, and high torque transmission systems. They play a fundamental role in improving the homogeneity, mechanical properties, and dimensional accuracy of steel products.

2. Working Principle of Blooming Mill

The blooming mill works based on the rolling deformation principle, where the ingot or cast slab passes repeatedly between rotating rolls to reduce its thickness and increase its length.

1. Heating:
   The ingot is first heated in a reheating furnace to 1200–1300°C to achieve sufficient plasticity.

2. Rolling Process:
   The red-hot metal is then fed into the rolling stand, where two or three high rolls compress it alternately in longitudinal and transverse directions.

3. Reduction and Elongation:
   Each pass reduces the cross-sectional area of the metal, increasing its length and refining its internal grain structure.

4. Reversing Mechanism:
   In reversible blooming mills, the rolls rotate alternately in both directions, enabling multiple passes without changing the metal’s feeding direction manually.

5. Output:
   The final rolled piece, known as a bloom, typically has a square or rectangular cross-section and is sent to billet or plate mills for further rolling.

3. Structural Composition of Blooming Mill

A typical blooming mill consists of the following main components:

1. Mill Stand (Frame):
   Heavy welded or cast structure that holds the working rolls and withstands rolling forces.

2. Working Rolls:
   Large-diameter forged steel rolls that deform the heated metal.

3. Roll Drive System:
   Includes a main motor, gearboxes, couplings, and spindles to transmit torque.

4. Screw-Down Mechanism:
   Controls the gap between rolls and ensures precise reduction.

5. Reversing Mechanism:
   Allows bidirectional rolling to minimize material handling.

6. Roll Table and Transfer Devices:
   Feed and receive hot metal between passes.

7. Hydraulic or Electro-Mechanical Systems:
   Used for roll positioning and automatic control.

8. Cooling and Lubrication System:
   Maintains roll temperature and prolongs service life.

4. Technical Characteristics and Performance Advantages

1. High Rolling Force:
   Can reach several thousand tons to handle large steel ingots.

2. Reversible Operation:
   Enables multiple passes without manual repositioning.

3. Precise Reduction Control:
   Advanced hydraulic systems ensure accurate roll gaps.

4. Improved Metal Quality:
   Enhances grain uniformity, density, and mechanical properties.

5. High Productivity:
   Suitable for continuous heavy-duty operation.

6. Automation and Digital Control:
   Modern blooming mills feature PLC or computer-based control systems.

7. Durability:
   Heavy-duty construction for long-term industrial use.

5. Classification of Blooming Mills

Blooming mills can be classified according to different criteria:

1. By Number of Rolls:

• Two-high blooming mill (most common)

• Three-high blooming mill (allows continuous rolling without reversing)

2. By Operation Mode:

• Reversible type

• Non-reversible (continuous) type

3. By Automation Level:

• Manual

• Semi-automatic

• Fully automatic

4. By Product Type:

• Bloom mills (for square blooms)

• Slabbing mills (for flat slabs)

6. Application Fields

Blooming mills are essential in the following industries:

• Steel and Metallurgical Plants — production of blooms and billets;

• Heavy Machinery Manufacturing — large forgings and shafts;

• Shipbuilding Industry — structural steel production;

• Automotive Industry — producing raw materials for axles and frames;

• Aerospace and Defense — high-grade alloy steel processing;

• Railway Industry — rail and wheel steel preforms.

7. Maintenance and Operation Guidelines

To ensure long service life and safety:

• Regularly inspect rolls, bearings, and gearboxes for wear.

• Maintain lubrication and cooling systems in good condition.

• Calibrate screw-down and hydraulic systems periodically.

• Ensure temperature uniformity of reheated ingots.

• Avoid overload or unbalanced rolling.

• Schedule maintenance shutdowns every 1,000–2,000 hours of operation.

Conclusion

The Blooming Mill represents the core equipment in primary steel rolling production.
It transforms heavy ingots into high-quality blooms and slabs, forming the foundation for subsequent manufacturing stages.

With the progress of automation, digital control, and intelligent manufacturing, modern blooming mills will continue to evolve toward higher efficiency, precision, and sustainability, becoming an indispensable part of the future metallurgical industry.