korkeamihiilisiä

Korkeamihiillisiä, or high-carbon steels, are steels with higher carbon content than low-carbon structural steels. They typically contain about 0.6 to 1.0 percent carbon by weight, with some grades reaching 1.2 to 1.5 percent. The elevated carbon content enables hardening by heat treatment and yields a hard, wear-resistant surface after quenching, but reduces ductility and weldability compared with lower-carbon grades.

Properties: When properly heat treated, high-carbon steels can achieve high hardness (often 60–66 HRC for knife steels), excellent wear resistance, and good edge retention. They tend to be more brittle than lower-carbon steels, with lower toughness in thick sections, and their machinability is limited. They are also more prone to quenching cracks if not carefully processed.

Heat treatment and processing: Hardenability is enhanced by alloying elements such as chromium, vanadium, molybdenum and tungsten. Typical treatment includes austenitizing at high temperatures, quenching to martensite, and tempering to balance hardness and toughness. Knife and tool steels may undergo multiple tempering cycles and precise cooling control.

Applications and examples: High-carbon steels are used for cutting tools, knives, saw blades, springs and high-strength wires. Common Western grades include 1095 (about 0.95% C) and 1080 (about 0.80% C); other grades blend carbon with alloying elements to improve wear resistance or toughness.

Welding and fabrication: Welding high-carbon steel is challenging due to the tendency to harden near joints. Preheating, post-weld heat treatment, and suitable filler metals are often required. In practice, korkeamihiilisiä denotes a category that trades ductility for hardness and wear resistance.