In high-speed rebar production, wave bending is a persistent defect that can derail production efficiency. Even with consistent water pressure (1.2MPa) and flow rates (540m³/h), many steel mills find that single-meter bending still exceeds national standards.
When frequent replacement of guides fails, the root cause often lies within the rolling mill groove geometry and the uneven metal deformation during the engraving process.
The Core Cause: Uneven Metal Deformation
The primary reason for wave bending in Φ16mm rebar is the speed difference in metal flow. During the finishing pass, the metal deformation on the engraved surface (containing identification marks like “ZG” or steel grades) is often inconsistent with the opposite surface.
Research indicates that the forward slip on the literal side is significantly greater because the engraved characters are typically 0.6mm shallower than the transverse ribs. This slight difference causes the metal to flow faster on one side, leading to a protrusion that manifests as a wave bend.
3 Technical Solutions for Rebar Straightness
To solve this, we tested three optimization schemes focusing on the engraving area parameters within the rolling mill groove.
1. Adjusting Engraving Area Length
By increasing the total length of the engraving area to 13L (horizontal rib spacing), we can redistribute the plastic flow. Reducing the number of ribs occupied per character allows for a more gradual transition of metal deformation.
2. Increasing Horizontal Ribs Between Characters (Recommended)
Our experiments show that the most stable solution is increasing the number of horizontal ribs between markings (e.g., between “ZG” and “16”) from 1 to 2-3 ribs. This rebar rolling process optimization balances the cooling rate and prevents the “protrusion effect” during the forced water-cooling phase.
3. Stroke Width Adjustment
While adjusting the character stroke width (e.g., from 3.4mm to 3.0mm) can slightly alter the pressure distribution, our tests showed this method has a less significant impact on single-meter bending compared to rib adjustment.
Experimental Results and Production Impact
By implementing Scheme 2 (increasing rib spacing in the groove), the maximum bending degree was successfully controlled within 0.2%, meeting strict national standards.
The benefits of this optimization include:
Reducing Scrap: Eliminated the previous 10-ton daily scrap rate caused by wave bending.
Boosting Operation Rate: Saved 3-4 hours of unplanned downtime previously spent on troubleshooting rolling errors.
Cost Efficiency: Improved billet consumption and overall production cost indicators.
Conclusion
Successfully eliminating wave bending requires looking beyond water cooling. By focusing on the precision of the rolling mill groove engraving, manufacturers can achieve superior rebar straightness and operational stability.