How to balance wear resistance and fracture resistance requirements in steel machinery roller tables for strip mills and rolling mills?
Publish Time: 2025-12-17
In industrial settings such as steel metallurgy, rolling, heat treatment, and heavy manufacturing, roller tables for strip mills and rolling mills, as core conveying and support equipment, endure multiple harsh tests under high temperature, high load, impact, friction, and thermal fatigue for extended periods. Their roller surfaces must resist the scraping of hot steel billets, the abrasion of iron oxide scale, and the thermal shock of cooling water, while the internal structure must possess sufficient toughness to prevent sudden fracture. Wear resistance and fracture resistance seem contradictory—the former requires high material hardness, while the latter relies on good toughness—achieving a delicate balance between the two is a key technical challenge in the design and manufacture of roller tables for strip mills and rolling mills. Modern engineering has successfully achieved this dual goal through gradient material design, advanced heat treatment processes, structural optimization, and surface strengthening technologies.
1. Material Selection: Laying the Foundation for Performance
Rollers for strip mills and rolling mills are typically made of high-quality alloy structural steel or special hot-work die steel. These materials inherently possess both high hardenability and tempering stability, achieving ideal comprehensive mechanical properties after heat treatment. More importantly, their chemical composition is precisely controlled—the addition of elements such as chromium, molybdenum, and vanadium enhances high-temperature strength and wear resistance while refining grains and suppressing the precipitation of brittle phases, providing a material foundation for achieving the desired "hard yet not brittle" performance.
2. Gradient Hardness Design: A Smart Structure of Outer Hardness and Inner Toughness
The core balancing strategy lies in constructing a hardness gradient distribution: the roller surface requires extremely high hardness to resist wear, while the core retains lower hardness to absorb impact energy and prevent crack propagation. This goal is primarily achieved through integral quenching combined with low-temperature tempering or induction hardening processes.
Integral heat treatment is suitable for small and medium-sized rollers. By controlling the quenching cooling rate and tempering temperature, sufficient toughness is maintained in the core while ensuring surface hardness.
Induction hardening is even more precise: only the roller surface is rapidly heated and hardened, leaving the core unaffected by heat, naturally preserving high toughness. This "surface-hardened, core-toughened" structure acts like armor, providing both wear resistance and fracture resistance.
3. Residual Compressive Stress: Inhibiting Crack Initiation and Propagation
Advanced heat treatment not only regulates hardness but also actively introduces beneficial residual compressive stress on the surface. For example, shot peening or rolling can form a micron-level compressive stress layer on the roll surface. Since cracks are difficult to initiate and propagate under compressive stress, this technology significantly improves the fatigue life of the roll. In hot rolling mills, this compressive stress can also offset some thermal stress, reducing the generation of hot cracks and further enhancing fracture resistance.
4. Surface Strengthening Technology: Surpassing Traditional Limits
Faced with extreme wear conditions, traditional heat treatment is no longer sufficient. At this point, surface engineering technologies such as laser cladding, plasma spraying, or physical vapor deposition are widely used. For example, cladding a layer of tungsten carbide or ceramic composite material on the roll surface can achieve a hardness of HRA 85 or higher, increasing wear resistance several times over; while the underlying layer remains a tough matrix, ensuring that the overall structure does not fail due to the peeling of a brittle coating. This concept of "functionally graded materials" pushes wear resistance and fracture resistance to new heights.
5. Synergistic Structure and Lubrication: System-Level Protection
Besides materials and processes, the structural design of roller tables for strip mills and rolling mills also helps balance these dual requirements. A reasonable roller diameter to wall thickness ratio avoids stress concentration; rounded corners reduce fatigue sources; and sealed bearings prevent impurities from causing abnormal wear. Simultaneously, an efficient dry oil or oil-air lubrication system continuously forms an oil film between the roller neck and bearing, reducing frictional heat and fretting wear, indirectly mitigating the roller's thermal load and mechanical impact, and extending its service life.
The balance between wear resistance and fracture resistance in steel mechanical components like roller tables for strip mills and rolling mills is a precise symphony of materials science, thermodynamics, and mechanical engineering. It doesn't pursue the ultimate in a single performance metric, but rather seeks the optimal solution between "rigidity" and "flexibility," "hardness" and "toughness." It is this systematic thinking and technological innovation that allows roller tables for strip mills and rolling mills to operate steadily under intense heat and pressure, becoming the silent but indispensable backbone of the modern steel industry.
