• Applied Microscopy
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• v.48 no.4
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• pp.117-121
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• 2018

The multiple length scale analysis of previously designed Fe-Mn-Al-C based low-density model alloys reveals the difference in ordered ${\kappa}-carbide$, $(Fe,Mn)_3AlC_x$, between Fe-25Mn-16Al-5.2C (at%) alloy and Fe-3Mn-10Al-1.2C (at%) alloy. For the former alloy composition consisting of fully austenite grains, ${\kappa}-carbide$ showed majorly cuboidal and minorly pancake morphology and its chemical composition was not changed through aging for 24 h and 168 h at $600^{\circ}C$. Meanwhile, for the isothermally annealed ferritic alloy system for 1 hr at 500 and $600^{\circ}C$, the dramatic change in the chemical composition of needle-shape ${\kappa}-carbide$, $(Fe,Mn)_3(Fe,Al)C_x$, was found. Here we address that the compositional fluctuations in the vicinity of the carbides are significantly controlled by abutting phase, either austenite or ferrite. Namely, the cooperative ordering of carbon and Al is an important factor contributing to carbide formation in the high-Mn and high-Al alloyed austenitic steel, while the carbon and Mn for the low-Mn and high Al alloyed ferritic steel.

• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.151-156
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• 2010

The high-strength low-alloy (HSLA) steels have low carbon contents (0.05~0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.376-380
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• 2017

In this paper, we prepared a metal alloy resistor with stable thermal electro motive force (thermal EMF) as well as a low temperature coefficient of resistance (TCR) by adjusting the manganese proportion from 3 to 12 wt% in the Cu-Mn-Ni alloy. Composition of the fabricated metal alloy was investigated using energy dispersive X-ray (EDX) analysis. The TCR of each sample was measured as 44.56, 40.54, 35.60, and 31.56 ppm for Cu-3Mn-2Ni, Cu-5Mn-2Ni, Cu-10Mn-2Ni, and Cu-12Mn-2Ni, respectively. All the resistor samples were available for the F grade (${\pm}1%$ of the allowable error of resistance) high-precision resistor. All the samples satisfied the baseline of high thermal EMF (under 3 mV at $60^{\circ}C$); however, Cu-3Mn-2Ni and Cu-5Mn-2Ni satisfied the baseline of low thermal EMF (under 0.3 mV at $25^{\circ}C$). We were thus able to design and fabricate the metal alloy resistor of Cu-3Mn-2Ni and Cu-5Mn-2Ni to have low TCR and stable thermal EMF at the same time.

• Journal of Korea Foundry Society
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• v.44 no.1
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• pp.9-15
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• 2024

In this study, in order to improve the lifespan of parts made of manganese steel, manganese steel was cast by varying the amount of Ti added to the steel. In order to confirm the characteristics of the cast material, processing characteristics including tensile and surface characteristics and bearing ratio were investigated. It was confirmed that when the amount of Ti added to high manganese steel exceeds 0.5%, the strength of the alloy is improved due to grain refinement, and fine carbides are formed inside the steel. This results in increased resistance to surface wear compared to the alloy with only Mn added. There was no significant difference in the increase in tensile strength as the Ti content in manganese steel was increased. However, inclusion of Ti showed a small but greater effect on wear resistance compared to Mn, and the size and the distribution of carbides become coarse depending on the Ti content. and was evenly distributed. It was confirmed that the strength and surface properties of manganese steel can be improved by the addition of Ti to improve the lifespan of parts made with this steel. It was found that Ti is effective in developing materials with excellent wear resistance due to refinement of dendrite crystal grains. In the samples where Ti was added, the carbide appears to increase the resistance to surface roughness, and due to the nature of Mn steel, surface hardening begins to occur, which appears to extend the life.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.10-14
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• 2012

Recently the low alloy steel plate made with manganese-molybdenum is used widely in steam drum and separator of the new coal-fired power plant boiler. This material is suitable for the vapor storage of high pressure and high temperature. The high temperature creep strength of Mn-Mo alloy is higher than the carbon plate(SA516) that used in the subcritical pressure boiler. It reduces the thickness of the pressure vessel and makes the lightweight possible. Recently in the power plant boiler operation and production process, the damage has happened frequently in the heat affected zone and base material according to the hydrogen crack and delayed crack. This paper describes the research result about the damage case experienced in the boiler steam drum production process and present the optimum manufacture method for the similar damage prevention of recurrence.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.426-431
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• 2008

The high-strength low-alloy(HSLA) steels have low carbon contents($0.05{\sim}0.25%$ C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.933-934
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• 2006

The present study examines the sintering behaviour and effect of manganese addition both mechanically-blended and mechanically alloyed on Cr-Mo low alloyed steels to enhance the mechanical properties. Mn sublimation during sintering provides some specific phenomena which facilitate the sintering of alloying elements with high oxygen affinity. First step is the optimization of milling time to attain a master alloy with 50% of Mn which is diluted in Fe-1.5Cr-0.2Mo water atomized prealloyed powder by normal mixing. These mixtures are pressed to a green density of $7.1g/cm^3$ and sintered at $1120^{\circ}C$ in $90N_2-10H_2$ atmosphere.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.229-235
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• 2014

In this paper, the effects of precipitates and Mn-solute atoms on the recrystallization behavior of an Al-Mn alloy was studied using micro-Vickers hardness, electrical conductivity measurements and optical microscopy. Various thermo-mechanical processes were designed to investigate the different morphologies, and the solute concentration, of Mn in the matrix. The results indicate that the recrystallization temperature, $T_R$ and time, $t_R$, are influenced by the amount of M-solute atoms in the matrix, and that the recrystallization microstructure is influenced by the amount of precipitates. Recrystallization in the Slow-Cooling specimen was rapid due to its low concentration of Mn-solute atoms, and the crystal-grain size was the smallest due to finely distributed precipitates. However, in the case of the No-Holding specimen, elongated grains were observed at the low annealing temperature and the largest recrystallized grains were observed at the high annealing temperatures (compared with Slow-Cooling and Base specimens) due to the high Mn-solute atoms in the matrix.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.53-53
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• 2010

Car industry has required light-weight steels, but still with strong mechanical strength. To meet this requirement, a variety of researches on Fe-Al alloys have been performed. As Al is being added in a disordered manner, alloys become more ductile and show higher yield stress. At a certain concentration of Al, however, the Fe-Al alloy system falls in a second phase whose mechanical strength is worsened. To understand the microscopic role of Al, we investigate the stability and the elastic properties of various Fe-Al alloys using ab initio density functional theory. At agiven Al concentration, the equilibrium geometry is obtained among several disordered Fe-Al alloy structures by performing the geometry relaxation. The formation energies and elastic properties such as bulk moduli of the equilibrium structures are also computed as a function of Al concentration. We also investigate the effects of different elements such as Si and Mn. Fe-Si alloy systems exhibit unusual mechanical behaviors requiring further investigation to understand their physical origin. Especially, the microscopic role of Mn is investigated to find its physical origin of preventing the Fe-Al alloy system from forming an unfavorable second phase. The effect of manganese on mechanical properties of Fe-based alloys is also explored.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1995.11a
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• pp.25-25
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• 1995

Liquid phase sintering of 90W-6Ni-4Mn alloy has been investigated as functions of sintering atmosphere, heating rate, and reduction temperature. The present work accounts for the thermodynamic oxidatiodreduction reactions of constituent powders of W, Ni and Mn. By discounting these reactions, the previous investigations would obtain only the alloy with large pores and the lowered relative sintered density, by the liquid phase sintering under a dry hydrogen atmosphere. the sintering cycle consisted of a rapid heating to reduction temperatures under high purity nitrogen atmosphere, and holding for 4 hours and sintering at $1260^{\circ}C$ for 1 hour under a dry hydrogen gas. The relative density of the sintered alloy increased with increasing heating rate. As the reduction temperature increased, the relative density increased to the lm theotical density at the duction temture above $1150^{\circ}C$. The mimsturcatre of sintered alloys has been analysed by a scanning election microscope. The sintered density was compared with those obtained from the other investigators. It was found that the reduction $1150^{\circ}C$ results in the lowered densification of 90W-6Ni-4Mn alloy. This is caused by the fact that reducing reactions of W and Ni oxides contained in W an Ni powders concomitantly leads to oxidizing reaction of Mn powder the oxidized Mn is hardly reduced at sintering temperature and thereby remains large pores in the alloy. It is concluded that the W-Ni-Mn alloy with full density can be obtained by the precise control of atmosphere, heating rate, and sintering temperature.