• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.64-72
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• 1993

Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaussian mode of beam. Then the model for rectagular beam was used for the predicition of the size of hardened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters such as beam mode, beam size, and traverse speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.26-30
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• 1996

This paper presents the performance of CBN tools in the machining of hardened die-materials, SKD11 and SKD61 steel with HRC 50, by high-speed face milling. Generally, grinding or EDM is being used in machining of hardened materials but the cost is very high. If those can be replaced by cutting, it will be a greatly economical advantage. CBN tool has been recognized as an effective tool in turning, but it has not been in milling. So wear and surface roughness mode of CBN tool for hardened SKD11 and SKD61 steel were investigated by high-speed face milling in this study Also the relation between cutting force and wear mode of CBN tools was investigated.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.267-273
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• 2009

Three types of structural intermetallic compounds, $Ni_3Al$, NiAl and TiAl, having each single phase structure without pores were produced by arc-melting process. Their sliding wear properties were investigated against a hardened tool steel. It was shown that the wear of the intermetallic compounds was hardly occurred against the hardened tool steel. TiAl compound showed the best wear resistance among them. In this case, wear was preferentially occurred on the surface of the hardened tool steel of the mating material which has higher hardness. It could be found that the wear mode on intermetallics without pores by arc-melting process was different from that on its porous layer coated on steel by combustion synthesis.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.221-226
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• 2014

A low temperature plasma nitrocarburizng was implemented on the duplex stainless steel to achieve the enhancement of surface hardness without degradation of its corrosion resistance. Attempts were made to investigate the influence of Pulse frequency and Duty factor of pulsed power in a high Pulse frequency regime on the surface characteristics of the hardened layer. The hardened layer (S-phase) was formed on all of the treated surfaces. Surface hardness reached up to 1300 $HV_{0.1}$ which is about 4.6 times higher than that of the untreated material (280 $HV_{0.1}$). The thickness of the hardened layer tends to increase lightly with the higher Pulse frequency and the higher Duty factor. The corrosion resistance of nitrocarburized duplex stainless steel was almost similar to that of the untreated material. Both the Pulse frequency and the Duty factor do not have a significant influence on the corrosion property of plasma treated duplex stainless steel.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.1001-1005
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• 2001

In this study, the surface of 40Cr steel was hardened by $CO_2$Laser, and then the microstructural transformations and the hardness distributions of the laser surface hardened layer were observed. The experimental results showed the surface hardening layer was consisted of three parts, which is outmost surface layer of needle martensite, middle layer of martensite and remained pearlite, and transitory boundary layer. In hardness distributions, the surface hardeness of the surface hardening layer had Hv 800~1000, that was 2 to 4 times of matrix's hardness. The hardeness distribution of laser hardening layer that of surface layer hardened by general heat treatment.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.3
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• pp.165-170
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• 1992

The chip controls are investigated experimentally for the purpose of estimating cutting ability of hardened steel. In this experiment, hardened STD11 steel ($HR_c$ 60) is turned with carbide tool M20 under various cutting conditions and with several tool shapes. The main results obtained are as follows : 1) Cutting conditions of cutting speed 45m/min. feed 0.09-0.13 rev. depth of cut 0.4-0.6 are recommended for the chip excluding. 2) In case that the feed becomes larger and a lead angle of cutting tool becomes smaller, the chip excluding becomes easier. 3) It is confirmed that frank wear and crator wear on the cutting tool appear severely from about 10 min. after cutting start and chip excluding get worse.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.429-436
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• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.71-80
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• 1991

This paper reveals the effect of the effective case depth(ECD) on the fatigue behavior of a high-frequency induction hardened SM45C in rotated bending fatigue test. In addition, the effects of fracture modes(surface origin type, inner origin type) on it are discussed. The fatigue limit of the induction hardened steel is remarkably increased compared with that of base metal. In addition, the fatigue limit is linearly increased as the effective casedepth grows deep in the region of this experiment (ECD/R;0.23-0.49). The S-N curve and fracture mode in the induction case hardened steel are classified into two kinds, as a result : N$_{f}$<10$^{5}$ ;surface origin type fracture(at high stress), N$_{f}$>10$^{5}$ ; in ner origin type fracture(at low stress). In case of inner origin type fracture; as the effective case depth(ECD) gets deep, the fatigue limit is increased by the reason that the fracture origin moves toward center; in reverse, is decreased by reason that the compressive residual stress gets low. As a result, the increasing effect of the former is much bigger than the decreasing effect of the latter, and the fatigue limit is increased as the ECD gets deep.eep.

• Journal of Ocean Engineering and Technology
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• v.23 no.2
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• pp.74-80
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• 2009

Surface hardening treatments, such as using the high-frequency induction hardening method, are widely used to increase the fatigue life and prevent the failure of materials by locally increasing the surface hardness. This method, in particular, brings an improvement in static strength by compressive residual surface stress due to the hardening. In this study, the mechanical properties of high-frequency induction hardened SCM440 steel were investigated. These results were also compared with those for base metal and a Q/T (tempering after quenching) treatment specimen. The test results showed that partially high-frequency induction hardened SCM440 steel specimens were more improved in static strength, surface hardness, fatigue limit, and anti-wear than the base metal and Q/T treatment specimens. In particular, the fatigue limit of the high-frequency induction hardened SCM440 steel increased by more than about 52% compared to that of base metal and by about 25% compared to that of the Q/T specimen.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.538-545
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• 1993

By using propagation characteristics of ultrasonic surface wave, the depth of the surface hardened layer of SCM440 steel with different high frequency induction heat treatments was measured and the same was done on the carburized SCM415 steel. The propagation velocity of surface wave was constant and independent of frequency in t.he specimens with identical microstructure, it was, however, decreased by 59m/s in the hardened layers compared to the unhardened part. From t.he relationship between the effective case depth and the wave length of surface wave, the depth of the hardened layer could be measured and evaluated nondestructively for both induction hardened and carburized steels.