• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.395-399
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• 2004

Four microalloyed steels containing B were investigated in terms of hardenability, mechanical properties and microstructure depending upon the cooling rates in order to develop the steel grade for the cold forged fasners. The alloy with the largest DI value among 4 alloys, which contains $0.12\%\;C,\;1.54\%\;Mn,\;0.65\%\;Cr,\;0.11\%V,\;0.040\%Ti\;and\;0.0033\%B$, showed the larest shift to the right hand side in the TTT diagram, implying the wide allowable cooling rate range subsequent to hot rolling in long bar processing, Mechanical tests indicated that yield strength are dependent upon the DI value in water quenched specimens but other properties showed almost the same values. In the same grade of steel, the increase in cooling rates causes the decrease in elongation but the increase in strength, reduction of area and Charpy impact values. Microstructural examination in steel grade with the larest DI values revealed martensitic structure In the water quenched state, a mixture of martensite and bainite in the oil quenched, and ferrite + pearlite in the air cooled and the forced air cooled but the latter showed finer microstructure.

• Journal of Korea Foundry Society
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• v.10 no.3
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• pp.202-209
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• 1990

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.400-411
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• 1994

• Journal of the Korean Society for Heat Treatment
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• v.2 no.3
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• pp.55-60
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• 1989

• Journal of the Korean Society for Heat Treatment
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• v.11 no.2
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• pp.131-139
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• 1998

The object of this research is to estimate the hardenability of quenched carbon steels AISI 1050. The equation of transient heat conduction was analyzed to derive cooling curve by finite element method. The effects of temperature on physical properties, metallic structures and the latent heat by phase transformation were considered. A good agreement was found between analytical and experimental results to show that the proposed numerical procedure was reliable. This procedure could be used as the detabase for optimal condition of heat treatment cycle.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.275-282
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• 2010

The improved properties of surface layer can be achieved by so-called "new salt bath nitriding(NSBN)", which has been developed by a domestic company. This process based upon modified traditional salt bath nitriding process, increased hardenability with minimum toughness deterioration. This process also offers not only less white layer surfaces but also more eco-friendly one. That is, NSBN is the new eco-friendly surface treatment technology removing harmful $CN^-$ and toxic gas. According to the research of applying NSBN to Cr-Mo-V steel which has been used in defense industry, showed the improved result of wear resistance and surface hardening than non-coated condition. In further, we expect NSBN to curtail expenses and productivity improvement applied to the various defense industry parts.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.802-806
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• 2001

Chrome-molybden steel or chrome steel for machine structural use been shown to excellent hardenability adding boron of a small amount at low carbon steel. In the country boron steel has been used widely high strength volt and wear resistant components of construction equipment. SEM results showed classical fatigue fractures, consistent with surface crack initiation. The speciments were cycled using under load controlled rotary bending fatigue tests. In this study, the fatigue crack initiation as well as the fatigue crack growth behavior and the fracture mechanism were investigated through observations of fracture surface boron steel(AISI 51B20).

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.174-178
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• 2001

Chrome-molybden steel or chrome steel for machine structures has been shown to excellent hardenability adding boron of a small amount at low carbon steel. These days, boron steel has been used high strength bolt and wear resistant components of construction equipment. SEM results showed classical fatigue fractures, consist with surface crack initiation. The specimens were tested repeatedly(9 times) under controlled load rotary bending fatigue tests. In the study, the fatigue crack initiation as well as fatigue crack growth behavior and the fracture mechanism were investigated through observations of fracture of boron steel surface(AISI 51B20).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.134-135
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• 2006

Ancorsteel 4300, a high performance Cr-Si-Ni-Mo steel, was unveiled two years ago as the first in a series of powder metallurgy alloys that will simulate wrought steel compositions. Advantages of this alloy include good compressibility, high hardenability, and excellent dimensional stability. More important, however, is that this alloy has the ability to be effectively sintered at $1120^{\circ}C$ and maintain oxygen contents below 500 ppm. This unique blend of performance and processing capabilities provides static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed that offers complimentary performance levels at a lower Mo content. This manuscript reviews properties of the two chromium steels with comparisons to traditional sinter-hardened and heat-treated powder metallurgy alloys.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.303-304
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• 2006

The mechanical properties of ferrous powder metallurgy (P/M) materials are directly related to their microstructure. Ferrous P/M materials with sufficient hardenability will develop microstructures containing significant percentages of martensite in the as-sintered condition. Recently, sinter-hardening has developed into a highly cost effective production method through hardened P/M parts without the need for additional heat-treatments. This paper reviews the advances of sinter-hardening as well as some key processing parameters such as sintering temperature, cooling rate, tempering required to produce high quality sinter-hardened components. Specific topics including effect of alloying elements, alloying methods, and the Characterization and observation of microstructure are discussed.