Introduction
Composite rolls, particularly those made from tungsten carbide (TC), are widely used in steel rolling mills due to their durability and resistance to wear. However, cracks can develop under certain conditions, leading to premature failure. In this article, we analyze the causes of cracks in composite rolls during the rolling of φ12 rebar and discuss effective solutions to prevent them.
Case Overview: Cracks in Composite Rolls
Image & Situation Description
The composite roll in question consists of four tungsten carbide (YGR60 grade) roll rings (70% WC, 30% Co+Ni+Cr) with dimensions φ380×φ260×110. These rings are mounted on a mandrel and secured with a hydraulic locknut.
During operation in a steel rolling plant:
Line A: Operated smoothly at 922°C (measured at the looper).
Line B: Experienced cracks at 845°C, leading to roll failure.
Root Cause Analysis
The cracks were identified as fatigue failures, primarily caused by:
Unstable Billet Temperature – Lower temperatures increase rolling force, exceeding the roll’s capacity.
Excessive Rolling Force – When billets enter at suboptimal temperatures, stress accumulates, leading to cracks.
Temperature Variations – Line B’s lower temperature (845°C vs. Line A’s 922°C) made the rolls more susceptible to cracking.
Solution Implemented
To resolve the issue, the following measures were taken:
- Adjusted Billet Temperature – Ensured billets entered at 920±20°C for uniform rolling conditions.
- Modified Roll Pass Design – Optimized to distribute stress more evenly.
- Post-Crack Maintenance – Cracked areas were ground off, though this reduced the roll’s lifespan.
After implementation, no further cracks occurred, confirming the effectiveness of temperature control and roll design adjustments.
Preventing Cracks in Composite Rolls
To maximize the lifespan of composite rolls, consider:
Strict Temperature Control – Maintain consistent billet temperatures to avoid excessive rolling forces.
Regular Inspections – Detect early signs of wear or micro-cracks before they propagate.
Proper Roll Pass Design – Optimize geometry to minimize stress concentrations.
Material Selection – Use high-grade tungsten carbide (e.g., YGR60) with optimal binder composition.
Conclusion
Cracks in composite rolls during the rolling of φ12 rebar are often linked to temperature instability and excessive rolling forces. By ensuring proper billet heating and optimizing roll pass design, mills can prevent premature failures and extend roll life.
Need Expert Advice on Composite Rolls?
If you’re facing issues with composite roll maintenance, procurement, or performance optimization, feel free to reach out for professional guidance.
Contact：cykc@cykcgroup.com.cn