Injecting bars into a bar mill (also known as a rolling mill for bars) involves feeding raw material (billets or blooms) into the rolling process to produce finished bar products. Here’s a step-by-step guide on how to properly inject bars into a bar mill:
1. Preparation of Billets/Blooms
– Ensure the raw material (billets or blooms) is of the correct size, chemical composition, and temperature.
– Heat the billets in a reheating furnace to the optimal rolling temperature (typically between 1000°C–1200°C, depending on steel grade).
2. Feeding the Billet into the Mill
– Use a pusher or extractor to move the heated billet from the furnace to the entry roller table.
– The billet is then aligned and guided toward the first rolling stand.
3. Entry into Roughing Stands
– The first rolling stand (roughing mill) reduces the billet’s cross-section.
– A bar injector system (if automated) or manual feeding may be used to push the billet into subsequent stands.
4. Continuous Rolling Process
– After roughing, intermediate and finishing stands further shape the bar.
– Proper alignment is critical—misalignment can cause cobbles (jams) or defects.
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5. Automation & Control Systems
– Modern mills use automated bar injectors with sensors and hydraulic pushers for smooth entry.
– The system ensures consistent speed and prevents jamming.
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6. Cooling & Cutting
– After rolling, bars pass through a cooling bed.
– They are then cut to required lengths by a shear or saw.
Key Considerations for Smooth Injection:
✔ Billet Temperature: Must be uniform to avoid uneven rolling.
✔ Alignment: Proper centering prevents cobbles.
✔ Rolling Speed: Must match entry speed to avoid tension issues.
✔ Lubrication/Cooling: Prevents sticking in guides and rollers.
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