Effect of a modified quenching on impact toughness of 52100 bearing steels

In this research, a new type of spring steel with ultra-high strength and toughness was designed, and its mechanical properties and microstructure under different heat treatment processes were studied. The results show that the optimal heat treatment process for the steel is oil quenching at 890 °C for 40 min, followed by tempering at 400 °C for 1 h. Its mechanical properties have an optimal combination of 1865MPa tensile strength, a yield strength of 1662 MPa, an elongation of 11.5%, a cross-sectional shrinkage of 51.5%, and a Charpy impact energy of 43.7 J at room temperature. With increasing austenitizing temperature, the austenite grain size increases, the martensite lath becomes thicker, and the strength decreases. With increasing tempering temperature, the lath boundary of martensite becomes blurred, the strength decreases, and the plasticity improves. In addition, it was found that during tempering at higher temperature (450 °C), large particle inclusions and secondary cracks appeared in the fractured surface, and a large number of carbides precipitated, leading to the brittleness of tempered martensite.

Section: Introductionmentioning

confidence: 99%

Heat Treatment Process, Microstructure, and Mechanical Properties of Spring Steel with Ultra-High Strength and Toughness

Shi,

Zheng,

Zhang

et al. 2024

“…Therefore, the relationship between adding Nb and reducing the sensitivity of bearing steel to cracks was not clear. In addition, the carbides in the bearing steel casting were dissolved through long-term insulation and high austenitizing temperatures [11][12][13][14]. However, even the coarse carbides formed during the solidification process after heat treatment cannot meet the performance requirements of high-quality bearing steel.…”

Section: Introductionmentioning

confidence: 99%

Effect of Carbides on Thermos-Plastic and Crack Initiation and Expansion of High-Carbon Chromium-Bearing Steel Castings

Feng,

Zeng,

et al. 2024

The bearing steel’s high-temperature brittle zone (1250 °C–1100 °C), second brittle zone (1100 °C–950 °C), and low-temperature brittle zone (800 °C–600 °C) were determined by the reduction in area and true fracture toughness. The crack sensitivity was strongest at temperatures of 1200 °C, 1000 °C, and 600 °C, respectively. Various experimental and computational methods were used to establish the phase type, microstructure, size, and mechanical properties of carbides in bearing steel. The critical conditions for crack initiation in the matrix (FCC-Fe, FCC-Fe, and BCC-Fe)/carbides (striped Fe0.875Cr0.125C, netted Fe2.36Cr0.64C, and spherical Fe5.25Cr1.75C3) were also investigated. The values for the high-temperature brittle zone, the second brittle zone, and the low-temperature brittle zone were 13.85 MPa and 8.21 × 10−3, 4.64 MPa and 6.52 × 10−3, and 17.86 MPa and 1.86 × 10−2, respectively. These were calculated using Eshelby’s theory and ABAQUS 2021 version software. The ability of the three carbides to cause crack propagation was measured quantitatively by energy diffusion: M3C > MC > M7C3. This study analyzed the mechanism of carbide precipitation on the formation of high-temperature cracks in bearing steel casting. It also provided the critical conditions for carbide/matrix interface cracks in bearing steel continuous casting, thus providing effective support for improving the quality of bearing steel casting.

“…Modified quenching heat treatment with different austenitisation processes can be used. The holding temperature of 740 • C (close to Ac 1 = 750 • C) makes the carbide and grain size of the steel uniform after quenching and low-temperature tempering, effectively reducing the stress concentration during impact loading, retarding crack growth and increasing impact toughness by 37% [17]. Besides, high-purity bearing steel is developed [18,19].…”

Section: Introductionmentioning

confidence: 99%

Effect of Rare Earth Y on Microstructure and Mechanical Properties of High-Carbon Chromium Bearing Steel

Xu,

Liu,

Yang

et al. 2024

The effect of rare earth Y on the microstructure and properties of high-carbon chromium bearing steel in different heat treatment processes has been studied. The microstructure and mechanical properties of the bearing steel under hot rolled, annealed and quenched and tempered conditions were compared and analysed, focusing on the effect of inclusions on fatigue performance. The addition of rare earth Y improves the microstructure, Vickers hardness, tensile strength, impact toughness and fatigue properties of bearing steel. The results show that rare earth Y can refine and spheroidise cementite, make the distribution of cementite more uniform, enhance the strengthening effect of the second phase and reduce the stress concentration caused by the shape of cementite. At the same time, the formation of network cementite is inhibited and the harm to grain boundary is reduced. It also has a refining effect on the grain, and the refined grain can achieve better mechanical properties. In addition, by modifying the oxides and sulphides in the steel, the properties of the steel are also improved, particularly in the quenched and tempered state.