Microstructure and Properties of High Speed Steel Rolls

With advancements in high-speed steel roll technology, rolling mills have seen significant improvements in speed and automation. These advancements demand higher quality rolls, particularly in terms of wear resistance, strength, and toughness. Enhancing roll performance to meet these demands poses a new challenge for roll developers. High-speed steel composite rolls address this by using high-hardness materials with excellent red hardness, wear resistance, and hardenability as the working layer. The core is made from materials like forged steel, alloy cast steel, high-strength grey cast iron, or high-strength ductile iron to meet toughness requirements, creating a high-performance roll through a metallurgical combination of the working layer and core.

Researchers have designed five types of high-speed steel roll materials. Using analysis methods such as optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), they conducted tests on impact toughness and wear resistance. They systematically studied the structure, performance, and wear resistance of high-boron low-alloy high-speed steel roll materials in both as-cast and tempered states. Results show that the as-cast structure of these materials includes a martensitic matrix, retained austenite, and various carbon-boron compounds, with hardness exceeding HRC64. The carbon-boron compounds form a network along the grain boundaries.

 

High Speed Steel Rolls

 

After RE-Mg-Ti composite modification, the grain boundaries exhibit significant necking and disconnection.

Tempering studies revealed that increasing the tempering temperature gradually decreases roll hardness. Under identical conditions, the toughness of unmodified roll material is slightly lower than that of modified material. However, excessive modifiers reduce the toughness. Wear tests indicated that the wear resistance of high-boron high-speed steel modified by the RE-Mg-Ti compound is superior to that of high-carbon high-vanadium high-speed steel in the comparison sample.

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