As a core consumable in industrial surface treatment, the toughness of ferrous metal steel maru directly determines cleaning efficiency, equipment lifespan, and workpiece surface quality. Tempering, a crucial step in the heat treatment process, precisely controls temperature and time to reconstruct the internal microstructure of steel maru, achieving a significant increase in toughness while maintaining hardness. This process involves three core mechanisms: stress relief, microstructure transformation, and grain refinement.
While quenched steel maru possesses high hardness, residual tensile stress and brittle martensite create an imbalance of "hard and brittle." The primary task of tempering is to eliminate these internal stresses—by heating to an appropriate temperature and holding it, atoms gain energy to rearrange themselves, and carbon atoms in the martensite gradually precipitate, forming carbide particles. This process not only releases stress accumulated during machining or quenching but also prevents crack initiation caused by stress concentration, laying the foundation for improved toughness. For example, during the quenching stage of Steel Maru after centrifugal atomization granulation, the rapidly cooled martensitic structure, while exhibiting high hardness, is also brittle. Tempering treatment, through a stress relaxation mechanism, significantly improves its toughness.
Tempering temperature is the core parameter for controlling the toughness of Steel Maru. In the low-temperature tempering stage, martensite begins to decompose into tempered martensite, and carbides are dispersed in the form of fine particles. At this stage, toughness increases with increasing temperature because residual stress is continuously eliminated and brittle phases do not accumulate in large quantities. During medium-temperature tempering, the structure transforms into tempered troostite, and carbides further coarsen, reaching peak toughness. At this stage, Steel Maru maintains sufficient hardness while significantly enhancing its impact resistance. High-temperature tempering transforms the structure into tempered sorbite. Although toughness decreases slightly due to grain growth, plasticity is greatly improved, making it suitable for processes with strict surface roughness requirements. Different particle sizes of Steel Maru require corresponding tempering temperatures. For example, fine-grained pellets, due to their large specific surface area, require more stringent temperature control during tempering to avoid overheating and softening.
Grain refinement is another key pathway for tempering to improve toughness. During tempering, the precipitation and distribution of carbides directly affect the grain boundary structure—fine, uniform carbide particles can pin grain boundaries, inhibiting abnormal grain growth, and simultaneously enhancing the material's resistance to fracture by hindering dislocation movement. For example, steel maru with added vanadium, titanium, and other strong carbide-forming elements can effectively refine grains through the high-melting-point carbides formed during tempering, resulting in a toughness increase of over 30%. Furthermore, the residual austenite film formed at the grain boundaries of tempered steel maru can absorb energy through phase transformation-induced plasticity during crack propagation, further enhancing toughness.
From an application perspective, the optimization of steel maru toughness through tempering is directly related to surface treatment effectiveness. In shot peening of aero-engine blades, high-toughness steel maru can withstand high-speed impacts without breaking, ensuring uniform reinforcement layer depth. In the cleaning process of automotive gears, shot with moderate toughness can effectively remove oxide scale without causing downtime for maintenance due to excessive equipment wear. Steel Maru that is not tempered or insufficiently tempered is prone to developing microcracks during impact. These cracks propagate with repeated use, not only shortening the lifespan of the shot but also potentially scratching the workpiece surface. Shot that has undergone precise tempering treatment, however, achieves a balance between toughness and hardness, extending its service life by 2-3 times.
The improvement in toughness of steel Maru in ferrous metal products through tempering treatment is essentially achieved through the synergistic effect of thermodynamics and kinetics, enabling precise control of its microstructure and mechanical properties. This process not only solves the problem of quenching brittleness but also endows steel Maru with a "hardness-flexibility balance" through grain refinement, stress relief, and optimized carbide distribution, making it an indispensable high-performance consumable in the field of industrial surface treatment.
