Steels for bearings

Microstructure-sensitive computational modeling of fatigue crack formation

Fatigue life of additively manufactured Ti–6Al–4V in the very high cycle fatigue regime

This article extensively reviews published research on inclusions in ingot steel and defects on ingot products, methods to measure and detect inclusions in steel, the causes of exogenous inclusions, and the transport and entrapment of inclusions during fluid flow, segregation, and solidification of steel cast in ingot molds. Exogenous inclusions in ingots originate mainly from reoxidation of the molten steel, slag entrapment, and lining erosion, which are detailed in this article. The measures to prevent the formation of exogenous inclusions and improve their removal are provided, which are very useful for the clean steel production of ingot industries.

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State of the art in the control of inclusions during steel ingot casting

Safe life and damage tolerance aspects of railway axles – A review

Gigacycle fatigue properties for high-strength low-alloy steel at 100 Hz, 600 Hz, and 20 kHz

Faceted shell structure in grain boundary diffusion-processed sintered Nd-Fe-B magnets

Fatigue tests up to 10 8 cycles were carried out for two spring steels (Heats A and D1) and one valve spring steel (Heat F) with tensile strength, σ B , of 1720, 1725 and 1764 MPa, respectively. The size and composition of inclusions in Heats Dl and F were controlled. The surface-type fracture occurred at shorter lives below 10 6 cycles, while the fish-eye-type fracture occurred at longer lives. The fatigue limit, σ W , at 10 8 cycles was 640 MPa for Heats A and D1 and 700 MPa for Heat F. Al 2 O 3 inclusions for Heat A and both TiN inclusions and matrix cracks, i.e. internal facets, for Heat F were observed at the fish-eye-type fracture sites, while only matrix cracks were observed for Heat Dl. ODA, i.e. optically dark area, which is considered to be related to hydrogen effects, were formed around Al 2 O 3 and TiN inclusions. Fatigue tests were also conducted after specimens were heated up to 573 K in high vacuum of 2 × 10 -6 Pa. The heat treatment eliminated matrix cracks for Heat D1 and the fatigue limit at 108 cycles recovered to the estimated value of 920 MPa from the equation ω w = 0.53 ω B for the surface fracture. These results suggest that inclusions control and hydrogen influence the gigacycle fatigue properties for these high strength steels. In addition, it is expected that the creation of a martensite structure with a high resistance to hydrogen effects in the inclusion-controlled steel could achieve the higher fatigue limit estimated for the surface-type fracture.

Gigacycle fatigue properties of 1800 MPa class spring steels

The effect of Co replacement for Fe on the microstructure and soft magnetic properties of Fe78.8−xCoxNb2.6Si9B9Cu0.6 (x=5–60) nanocrystalline alloys has been studied for improving the soft magnetic properties of Fe–Si–B–Nb–Cu type alloys at a high frequency range. The magnetic anisotropy constant increases with x, but the coercivity increases when x exceeds 20, indicating that magnetic softness is degraded by replacing Fe with Co. Three-dimensional atom-probe observations have revealed that the number density of Cu-enriched clusters decreases with x, thereby decreasing the number density of the heterogeneous nucleation sites for bcc-Fe primary crystals. In addition, differential scanning calorimetry measurements show that the Cu clustering temperature shifts to a higher temperature with increasing x, suggesting that the kinetics for the Cu clustering decreases as Co content. These experimental results are discussed from the thermodynamical point of view, and the optimized Cu composition to achieve a low coercivity with 40 at % Co has been found. © 2003 American Institute of Physics.

Optimization of the microstructure and properties of Co-substituted Fe–Si–B–Nb–Cu nanocrystalline soft magnetic alloys

10 10 -cycle fatigue tests were conducted at 100 Hz for three years and at 20 kHz for one week on 1800 MPa-class JIS-SUP7 spring steel. Uniaxial tests up to 10 8 cycles were also conducted at 120 and 600 Hz. The 120 Hz tests had larger control volumes. The fatigue limit at 10 10 cycles was lower than at 10 8 cycles, and any frequency effect was shown to be negligible. A size effect was found; the tests with larger control volumes showed results of lower fatigue strength.

Takayuki Abe

Papers

Gigacycle fatigue properties for high-strength low-alloy steel at 100 Hz, 600 Hz, and 20 kHz

Faceted shell structure in grain boundary diffusion-processed sintered Nd-Fe-B magnets

Gigacycle fatigue properties of 1800 MPa class spring steels

Optimization of the microstructure and properties of Co-substituted Fe–Si–B–Nb–Cu nanocrystalline soft magnetic alloys

1010-cycle fatigue properties of 1800 MPa-class JIS-SUP7 spring steel