• 한국산학기술학회논문지
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• 제13권11호
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• pp.4950-4955
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• 2012

볼트의 제작 공정은 연속적인 단조 작업에 의해서 완성되는데 각 공정의 기술적, 경제적인 성공은 적절한 공정설계와 각 작업에 필요한 금형 설계에서 좌우된다. 본 연구에서는 다단 공정에 의해서 이루어지는 SCM435 볼트의 성형과정 중에서 1, 2단계의 성형을 유한요소법을 이용하여 해석하여 합리적인 공정이 이루어지도록 개선 방향을 제시하고자 하며 유한요소법을 이용하여 해석한 1, 2단계의 공정은 축대칭이 성립되므로 소재의 변형 형상이 공정에서 기대했던 치수를 만족할 수 있었으며 소재에 형성된 단류선이 전 공정을 통하여 부드럽게 연속적으로 형성됨을 알 수 있었으므로 소재의 성형 뿐 아니라 내부의 결함도 없을 것으로 예상되었다.

• 소성∙가공
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• 제20권3호
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• pp.243-249
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• 2011

In this study, an approach designed to compute high temperature friction coefficients for SCM 435 steel through a pilot hot rolling test and a finite element analysis, is proposed. Single pass pilot hot flat rolling tests with reduction ratios varying from 20 to 40% were carried out at temperatures ranging from 900 to $1200^{\circ}C$. In the proposed approach, the friction coefficient is calculated by comparing the measured strip spread and the roll force with the simulation results. This study showed that the temperature and reduction ratio had a significant influence on the friction coefficient. As both material temperature and reduction ratio become higher, the friction coefficient increases monotonically. This finding is not in agreement with the Ekelund model, which is widely used in the analysis of the hot rolling process. In the present work, the friction coefficient at a reduction ratio of 40% was found to be 1.2 times greater than that at a reduction of 30%. This higher friction coefficient means that an increment of the roll thrust force is expected at the next stand. Therefore, a roll pass designer must understand this phenomenon in order to adjust the reduction ratio at the stands while keeping the driving power, the roll housing structure and the work roll strength within the allowable range.

• 한국산업융합학회 논문집
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• 제23권4_1호
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• pp.531-539
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• 2020

When injection mold is repeatedly used for mass production, fatigue phenomenon due to cyclic stress may occur. The surface and interior of structure might be damaged due to cyclic stress or strain. The objective of this study was to analyze failure of SCM435 high-tension bolts connecting upper and lower parts of a three-stage injection molding machine. These bolts have to undergo an accurate heat treatment to prevent the formation of chromium carbide and the action of dynamic stresses. Bolts were fractured by cyclic bending stress in the observation of ratchet marks and beach marks. Damaged specimen showed an acicular microstructure. Impurity was observed. Chromium carbide was observed near the crack origin. Both shape parameters of the Vickers hardness were similar. However, the scale parameter of the damaged specimen was about 20% smaller than that of the as-received specimen. Much degradation occurred in the damaged specimen. Bolts should undergo an accurate heat treatment to prevent the formation of chromium carbide. They must prevent the action of dynamic stresses. Bolts need accurate tightening and accuracy of heat treatment and screws need compression residual stress due to peening.

• 한국재료학회지
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• 제14권4호
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• pp.265-269
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• 2004

Plasma nitrocarburising and post oxidation were performed on SCM435 steel by a pulsed plasma ion nitriding system. Plasma oxidation resulted in the formation of a very thin ferritic oxide layer 1-2 $\mu\textrm{m}$ thick on top of a 15～25 $\mu\textrm{m}$ $\varepsilon$-F $e_{2-3}$(N,C) nitrocarburized compound layer. The growth rate of oxide layer increased with the treatment temperature and time. However, the oxide layer was easily spalled from the compound layer either for both oxidation temperatures above $450^{\circ}C$, or for oxidation time more than 2 hrs at oxidation temperature $400^{\circ}C$. It was confirmed that the relative amount of $Fe_2$$O_3$, compared with $e_3$$O_4$, increased rapidly with the oxidation temperature. The amounts of ${\gamma}$'-$Fe_4$(N,C) and $\theta$-$Fe_3$C, generated from dissociation from $\varepsilon$-$Fe_{2-3}$ /(N,C) phase during $O_2$ plasma sputtering, were also increased with the oxidation temperature.e.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.124-127
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• 2009

In this paper, a longitudinal die insert fracture which occurred during cold forging of a high strength ball-stud with a sound die design nearly optimized empirically for relatively low strength material of SCM435 is introduced and the reason is revealed. A comparative study between SCM435 and ESW105 is quantitatively made using a thermoelastic finite element method for die structural analysis coupled with a forging simulator theoretically based on a rigid-plastic finite element method. It has been shown that the longitudinal die insert fracture caused from non-optimized value of shrink fit, emphasizing that the die optimal design is inevitable for cold forging of high strength materials.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.59-60
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• 2008

• 한국기계가공학회지
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• 제12권5호
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• pp.109-115
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• 2013

In this study, a variable swash plate compressor has been used in a vehicle to improve its fuel efficiency. To manufacture the swash plate, either SCM 435 or UNS C67300 was used. The effects of using different materials for the structural reliability of compressor have been investigated. Static analysis was carried out on swash plate A/C compressor by using commercial software ANSYS 13.0v. The results showed that the Max. stress occurred on the swash plate made of UNS C67300 was lower than that made of SCM435, which indicated that UNS C67300 is more suitable for producing the safe swash plate.

• 한국정밀공학회지
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• 제31권12호
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• pp.1115-1119
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• 2014

In this article, a 20 kHz ultrasonic waveguide for nano-surface treatment was designed and manufactured. When designing the system, finite element analysis with ANSYS software was performed to find optimal dimensions of the waveguide, which can raise energy efficiency. Consequently an anti-resonance frequency of an Al waveguide with a piezoelectric actuator was 20 kHz, which predicted the experimentally obtained value of 18 kHz well. For the assessment of the performance, Steel Use Stainless (SUS) 304 and chromium molybdenum steel (SCM) 435 specimens were tested. Cross-sectional microscopies of SUS304 were taken and they showed that the treated thickness was $30{\mu}m$. Additionally, hardness tests of SCM435 were done and the hardness before the process was 14.0 Rockwell Hardness-C scale (HRC) and after the process was 20.5 HRC, respectively, which means 46% increase. Considering these results, the developed ultrasonic system is thought to be effective in the nano-surface treatment process.

• 소성∙가공
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• 제18권6호
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• pp.453-457
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• 2009

In this paper, plastic deformation behaviors of ESW105 and SCM435 steels are revealed by simulations and experiments. ESW105 is the special pre-heat-treated steel characterized by high initial yield strength and negligible strain-hardening behavior. The flow stresses of the two steels for large stain are calculated from tensile tests. Axial and lateral compressions of cylindrical bars are tested and simulated and the deformed shapes are compared to characterize the plastic deformation behaviors of the two materials. A forward extrusion process of a cylindrical bar is also simulated to reveal the difference. It has been shown that there are pretty much difference in plastic flow between ESW105 and SCM435 which causes from the difference in strain-hardening capability, implying that the experience-oriented design rules for common commercial materials may lead to failure in process design when the new material of ESW105 is applied without consideration of its plastic deformation behavior.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.48-51
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• 2009

In this paper, plastic deformation behaviors of ESW105 and SCM435 steels are revealed by simulations and experiments. ESW105 is the special pre-heat-treated steel characterized by high initial yield strength and negligible strain-hardening behavior. The flow stresses of the two steels for large stain are calculated from tensile tests. Axial and lateral compressions of cylindrical bars are tested and simulated and the deformed shapes are compared to characterize the plastic deformation behaviors of the two materials. A forward extrusion process of a cylindrical bar is also simulated to reveal the difference. It has been shown that there are pretty much difference in plastic flow between ESW105 and SCM435 which causes from the difference in strain-hardening capability, implying that the experience-oriented design rules for common commercial materials may lead to failure in process design when the new material of ESW105 is applied without consideration of its plastic deformation behavior.