• 열처리공학회지
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• 제37권3호
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• pp.128-137
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• 2024

In this study, the carburizing heat treatment process used in aircraft gear manufacturing was compared with the general carburizing heat treatment process using AISI 9310 steel. The process of carburizing followed by slow cooling, and then quenching after austenitizing(Process A) showed less compressive residual stress and less retained austenite in the surface layer compared to the process of quenching directly after carburizing(Process B). In prpcess B, there was a large amount of retained austenite when quenched immediately after carburization, and when treated with subzero, martensite rapidly increased and the compressive residual stress increased significantly, but at the same time, there is a risk of cracking due to severe expansion in volume. Therefore, in the case of aviation parts, it is believed that a step-by-step heat treatment cycle was adopted to ensure stability against heat treatment cracks. As a result of the final tempering after sub-zero treatment, the A process specimen showed a deeper effective case depth and HV700 depth and a higher hardness value above HV700 than the B process specimen.

• 한국표면공학회지
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• 제43권5호
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• pp.211-216
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• 2010

Vacuum carburizing process is well known process for its environment-friendly, low-cost, high-quality characteristics, compared with gas carburizing. In this study, a research was carried out to develop a process of vacuum carburizing for essential components of automotive transmission that is difficult to control its distortion. As a result, vacuum carburizing process is superior to gas carburizing in terms of cost, environment and quality.

• 열처리공학회지
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• 제28권1호
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• pp.24-31
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• 2015

In this study, a simulation was used to derive an optimal process of heat treatment with carburizing, and compared the derived result with SCr420HB helical gear in heat treatment with carburized quenching process about a change of the quenching method. The optimal carburizing process time is derived by the simulation with the theoretical time. The process has been performed by oil quenching and salt quenching method. Through the comparison of the results from the simulation(Hardness, effective case depth hardened by carburizing treatment and deformation) and the actual process, analyzed the error value of each quenching. And it verified the applicability of the simulation.

• 열처리공학회지
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• 제19권5호
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• pp.262-269
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• 2006

The development of eco-friendly low pressure carburizing system with high pressure gas quenching(LPC-GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1284-1292
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• 2006

Heat treatment is a controlled heating and cooling process to improve the physical and/or mechanical properties of metal products without changing their shapes. Today finite element method is widely used to simulate lots of manufacturing processes including heat treatment and surface hardening processes, which aims to reduce the number of time- and cost-consuming experimental tryouts. In this study we tried, using this method, to simulate the full carburizing process that consists of carburizing, diffusing and quenching, and to predict the distribution of carbon contents, phase fraction and hardness, thermal deformation and other mechanical characteristics as the results. In the finite element analysis deformation, heat transfer, phase transformation and diffusion effects are taken into consideration. The carburizing process of a lock gear, a part of the car seat recliner, that is manufactured by the fine blanking process is adopted as the analysis model. The numerical results are discussed and partly compared with experimental data. And a combination of process parameters that is expected to give the highest surface hardness is proposed on the basis of this discussion.

• 열처리공학회지
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• 제5권1호
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• pp.32-40
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• 1992

This content is a part of the results of the study on the development of the vacuum carburizing technology. In this study the vacuum carburizing furnace being used was the furnace that developed through the joint project between KIMM and Kyung-Pook Heat Treating Co. from June 1988 to Nov. 1990. And the used carburizing gas was the propane gas and the introducing methods of the gas applied two methods such as pulse and constant pressure. By this study we established the basis of the furnace manufacturing technology and of the processing technology in the vacuum carburizing. Above all in this work there are notable meanings in a viewpoint of the foremost research in home. Hereafter, we are going to industrialize the vacuum carburizing technology by improving the results of the present work and by developing the process for the mass production.

• 열처리공학회지
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• 제15권6호
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• pp.269-271
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• 2002

For the investigation of the hardness profiles and distortion characteristics of SCM415 steel, test pieces of SCM415 steel were gas and vacuum carburizing treated. The hardness profiles and distortion characteristics of vacuum and gas carburized SCM415 steel show different results. Vacuum carburizing can offer more improved hardness profiles than alternate methods of carburizing. Compared to alternate methods of carburizing, vacuum carburizing can offer improved mechanical properties and reduced cycle times of the process.

• 열처리공학회지
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• 제35권3호
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• pp.139-149
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• 2022

In the automobile and shipbuilding industries, various materials and components require superior surface strength, excellent wear resistance and good resistance to repeated loads. To improve the surface properties of the materials, various surface heat treatment methods are used, which include carburizing, nitriding, and so on. Among them, carburizing treatment is widely used for structural steels containing carbon. The effective carburizing thickness required for materials depends on the service environment and the size of the components. In general, however, there is a limit in evaluation of the surface properties with a standardized mechanical test method because the thickness or cross-sectional area of the carburized layer is limited. In this regard, the nanoindentation technique has lots of advantages, which can measure the mechanical properties of the material surface at the nano and micro scale. It is possible to understand the relationship between the microstructural change in the hardened layer by carburizing treatment and the mechanical properties. To be spread to practical applications at the industrial level, in this paper, the principle of the nanoindentation method is described with a representative application for analyzing the mechanical properties of the carburized material.

• 열처리공학회지
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• 제34권6호
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• pp.272-280
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• 2021

The influence of acetylene flow rates on the carburizing behavior of an AISI 4115 steel in 1 ton-class mass production-type vacuum carburizing furnace has been studied through microstructure, carbon concentration, hardness analyses. The AISI 4115 steels were carburized with various flow rates (20, 32.7, 60 l/min) and locations in the furnace (top, center, bottom) at 950℃. The acetylene flow rate played an important role in controlling the carburizing properties of carburized samples, such as effective case depth and uniformity carburizing according to location in the furnace. At an acetylene flow rate of 20 l/min, the carburized samples had a shallow average hardened layer (0.645 mm) compared to the target hardening depth (1 mm) due to low carbon flux and spatial uniformity of carburization (17.8%) in the furnace. At a flow rate of 60 l/min, the carburized samples showed an average hardened layer (1.449 mm) deeper than the target hardening depth and had the spatial uniformity of carburization (98.8%). In particular, at a flow rate of 32.7 l/min, the carburized samples had an average hardened layer (1.13 mm) close to the target hardening depth and had the highest carburizing uniformity (99.1%). As a result, an appropriate flow rate of 32.7 l/min was derived to satisfy the target hardening depth and to have spatial uniform hardened layer in the furnace.

• 열처리공학회지
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• 제5권4호
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• pp.195-200
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• 1992

SCM 415 has been vacuum carburized in the carburizing pressure of 60-65kpa and the carburizing temperature of 1233k and 1273k after varied to 0-20 in the ratio of $N_2/C_3H_8$ and then diffusion treated for various times at 1123k. The results obtained from the experiment are as follows. 1. With increasing from 0 to 20 in ratio of $N_2/C_3H_8$ the sooting formation of surface after carburizing considerably decreased. 2. The hardness control and surface carbon content of carburizing surface has been modified by the addition of nitrogen to the propan. 3. The appoximate value of k is indirectry calculated at 1123k which results are obtained to $0.58{\times}10^{-2}(wt.%.S^{-1/2})$. 4. A great deal of propan by addition of nitrogen gas in carburizing gas was possible to saving without considerable change in case hardening depth. 5. The effective carburizing depth range is obtained to 0.8-1.1mm by diffusion temperature of 1123k after carburization at 1273k-3.6ks, and the surface hardness is increased as the increasing of $T_D/T_c$ in our experimental condition, and the maximum hardness as reachin distance from surface is decreased.