• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.835-841
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• 2012

We measured the mechanical and thermal properties of four types of cast irons used for manufacturing the brake discs of railway vehicles. It was found that these properties could be controlled by varying the composition of Ni, Cr, and Mo. Thermal fatigue tests were carried out by using a thermal fatigue tester in which thermal cycles could be controlled. Thermal crack initiation and propagation were measured on cylindrical specimens. Finally, we simulated the thermal fatigue test procedure by finite element analysis and calculated the thermal fatigue lifetimes by Manson-Coffin's equation and the maximum principal strain. The estimated thermal fatigue lifetimes corresponded to the measured lifetimes when the total crack length was $40{\mu}m{\sim}1mm$.

• Journal of Korea Foundry Society
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• v.24 no.6
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• pp.323-330
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• 2004

This study aims to investigate on the effects of the microstructures on the wear characteristics of the different grey cast iron(GC) and spheroidal ductile cast iron(DCI). Wear test using wear tester of pin-on-disc type was carried out under the conditions of load 47.2N , velocity 0.2m/s, distance 4000m. At the GC, Wear rates depend on graphite type and oxide layer formed at wear surface. Weak rosette graphites are easily broken and formed wear debris over 30 ${\mu}m$. This wear debris occurs scuffing at wear surface. As a result of surface deformation, Narrow regions of the matrix between the graphite flakes and the contact surface lead to the failure of the necks. Wear rate for the DCI depended on hardness of matrix more than size of graphite.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.39-45
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• 2022

In this study, it was verified that carbon-ceramic brake discs can replace existing cast-iron brake discs of the same size. In addition, a method of pretreating carbon fiber to secure heat dissipation characteristics while using a small amount of carbon fiber was established. The thermal conductivity and bending strength characteristics were analyzed according to the carbon content, and brake braking tests were conducted. Through pretreatment, the maximum temperature was lowered by 16 ℃ compared to the case using only carbon fiber, and the cooling rate was improved by approximately 10% compared to metal brake discs. However, the total heat capacity increased as the mass increased owing to the reaction. Thus, the measured temperature was higher than that of the metal brake disc; therefore, additional research is required.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.289-295
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• 2004

The relationship between friction characteristics and iron oxides at the sliding interface was investigated. Three friction materials containing iron, magnetite $(Fe_3O_4)$ or hematite $(Fe_2O_3)$ were manufactured and friction tests were performed on gray cast iron disks to evaluate the friction coefficient as a function of sliding speed $\mu-\nu$. In-situ noise spectrum analyzer was employed to compare noise propensity during friction tests. Results show that the specimens with magnetite are more sensitive to velocity than those with iron or hematite. The specimens containing magnetite and hematite generated noise with different peaks in the spectrum. The difference in the peak frequency seems attributed to the different surface aggressiveness of iron oxides and intermittent changes of real contact area at the sliding interface during sliding. Surface morphology and roughness of the counter disc after the tests are also consistent with the aggressiveness of iron oxides.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.971-974
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• 2011

Aluminum matrix composites reinforced with SiC particles(AMC) are one of the candidate materials for the weight reduction of rolling stock brake discs. It is known that weight reduction of about 40% is possible when they replace conventional cast iron brake discs. But casting is not easy because of bad wettability of SiC with Al alloy. We developed two AMC brake discs with SiC volume fraction of 20% by a new casting method. It was found the developed method produced brake discs of good quality.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.140-145
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• 2009

This paper deals with a stability evaluation of a butterfly valve using the body and disc of a valve seat. The experimental results of a strength evaluation are shown using STS316 stainless steel and spheroidal graphite cast iron (GCD450). The disc material was made from GCD450. The results of the strength analysis are as follows: Ultimate tensile strength 485MPa, Yield strength 370 MPa, Young's modulus $1.1{\times}10^5$, and Poisson's ratio v = 0.28. For the results of the disc analysis, the safety factor was about 4. This shows that a design was derived that satisfied the requirements of structural safety. However, some problems, such as the deflection and deformation of the disc, may occur when the sea water has back flow with a high pressure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.337-343
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• 2017

The laser cladding process on structural steel (SCM440) and gray cast iron (GC250) substrates with Co-based powder (Stellite 12) was studied. A diode laser (2 kW) was used as a heat source, and the powder was supplied by a disc rotary powder feeder. The relationship between the laser cladding process and the cross-sectional analysis of coating was examined based on coating shape and microstructure. Additionally, the microhardness was measured to confirm the mechanical property improvements. As a result, proper laser cladding conditions were selected through this study and verified by cross-sectional analysis. In addition, the evaluation process for laser cladding feasibility was conducted on the selected materials.

• Tribology and Lubricants
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• v.36 no.2
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• pp.88-95
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• 2020

In this study, we investigate the mechanical properties of high manganese steel, and the friction and wear characteristics of brake friction material containing this steel, for passenger car application, with the aim of replacing copper and copper alloys whose usage is expected to be restricted in the future. These steels are prepared using a vacuum induction melting furnace to produce binary and ternary alloys. The hardness and tensile strength of the high manganese steel decrease and the elongation increases with increase in manganese content. This material exhibits high values of hardness, tensile strength, and elongation; these properties are similar to those of 7-3 brass used in conventional friction materials. We fabricate high manganese steel fibers to prepare test pad specimens, and evaluate the friction and wear characteristics by simulating various braking conditions using a 1/5 scale dynamometer. The brake pad material is found to have excellent friction stability in comparison with conventional friction materials that use 7-3 brass fibers; particularly, the friction stability at high temperature is significantly improved. Additionally, we evaluate the wear using a wear test method that simulates the braking conditions in Europe. It is found that the amount of wear of the brake pad is the same as that in the case of the conventional friction material, and that the amount of wear of the cast iron disc is reduced by approximately 10. The high manganese steel is expected to be useful in the development of eco-friendly, copper-free friction material.

• Journal of Auto-vehicle Safety Association
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• v.7 no.2
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• pp.19-24
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• 2015

Ferritic Nitro Carburizing (FNC) cast iron brake discs is known to improve corrosion resistance and brake creep groan noise as well as prevent corrosion-induced pulsation. But, it is necessary to treat honing machining on braking surface to avoid grinding noise during braking.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.4
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• pp.261-270
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• 1996

Boriding is one of the chemical methods to achieve the case hardening of steel as well as nitriding or carburizing. The surface layer of the borided steel shows higher hardness and exhibits better resistance to corrosion or fatigue than the nitrided or carburized steel. The great majority of previous studies were confined to mild steel or some alloy steel. To enlarge the application, ductile cast iron (DCI) as a material for boriding has been tried in this study. Thus, sliding wear test has conducted using a pin-on-disc machine to compare between borided DCI and mild steel in fluidized bed furnace. The results show that the wear resistance of borided DCI is improved. Especially it is more efficient in the case of occurence of the mechanical wear.