• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.10a
• /
• pp.248-253
• /
• 1998

Recently, the uses of Ceramic/metal bonded joints, resin/metal joints, adhesive joints, composite materials which are composed of dissimiliar materials have increased in various industry fields. Since the ceramic/metal bonded joints material is made at a high temperature, residual stress distributions due to differences in material properties were investigated by varying material parameters. The two dimensional finite element analysis was performed to study residual stress distribution in Si3N4/SM45C bonded joint with a copper interlayer between the silicon nitride(Si3N4) and the structural carbon steel(SM45C) and 4-point bending tests were carried out under room temperature. Fracture surface and crack propagation path were observed using scanning electron microscope and characteristics of its fracture was discussed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.6
• /
• pp.519-525
• /
• 2008

For this study, SM45C steel rods using generally for power transmission shafts and machine components was selected and welded by butt-GMAW method. And then it was studied about estimation of fatigue strength and the region of infinite life by Haigh diagram using Goodman's equation. Fatigue strength in weld zone presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. This result agrees with distribution of hardness in weld zone. Fatigue strength in base metal zone presents highly compared with weld zone in low cycles between $10^4$ cycles and $10^6$cycles, but it presents the lowest fatigue strength on the order of heat affected zone in the vicinity of $10^6$cycles. It is the result that the first high compressive residual stress distributed by drawing process of the steel rods is released and the base metal is softened by alternating stresses. The region of infinite life by Haigh diagram presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. From this results, it is demanded that the stress for safety design of machine components using SM45C butt-welded steel rods must be selected in the region of the lowest infinite life of heat affected zone.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.6
• /
• pp.953-962
• /
• 1987

Domestic dissimilar structural steels, SM 45 C and SUS304 were friction welded under optimal welding condition and the micro-artificial holes were drilled at SM 45 C base metal, SM 45 C HAZ, welded zone, SUS 304 HAZ, and SUS 304 base metal for fatigue behavior tests. In this study, the fatigue limit and the behavior of micro-crack propagation, crack propagation rate, and its dependency on stress intensity factor under the low stress level and high stress level of bending stress have been investigated. The results obtained are as follows. (1) The fatgiue strength of the portion of SM45C B.M., SM45C HAZ, welded zune, SUS304 HAZ and SUS304 B.M. on notched friction welded specimens are 20 kgf/mm$^{2}$, 32 kgf/mm$^{2}$, 27kgf/mm$^{2}$, 29kgf/mm$^{2}$, and 29kgf/mm$^{2}$, respectively. (2) The fatigue strength of welded zone of unnotched and notched specimens are 32.5kgf/mm$^{2}$, and 27kgf/mm$^{2}$, respectively. (3) Micro-crack initiation in the welded zone, HAZ, and each base metals occurrs simultaneously in front and rear of micro-hole tips in the view of the rotational directions. (4) Fatigue crack propagates more slowly in the welded zone than in another protions of specimen, regardless of the magnitude of the stress level. (5) Fatigue crack propagation rates were plotted as a function of stress intensity range. The value of m in the equation da/dN=C(.DELTA.K)$^{m}$ was found to range from 2.09-2.55 in this study.

• Journal of the Korean Society for Heat Treatment
• /
• v.13 no.4
• /
• pp.224-230
• /
• 2000

Garbon steel(SM35C) was gas nitrocarburized at $580^{\circ}C$ in $55%N_2-40%NH_3-5%CO_2$ mixed gas atmosphere, and then the steel was induction hardened at $850^{\circ}C$. The microstructure of gas nitrocarburized surface layer was observed by optical microscope and SEM. The phase analysis was carried out by X-ray diffraction method. The mechanical properties of gas nitrocarburized SM35C steel was evaluated by hardness, wear and fatigue test. The thickness of compound and diffusion layer were increased with increasing the gas nitrocarburizing time and the densest compound layer was obtained at 3 hours gas nitrocarburizing time. In case of 15sec induction hardening after gas nitrocarburizing, the surface hardness was decreased from 800Hv to 630Hv owing to the decomposition of compound layer, but wear resistance was increased because of increased hardness of diffusion layer. The fatigue strength of induction hardened steel after gas nitrocarburizing, $58kgf/mm^2$, was higher than $41.5kg/mm^2$ of gas nitrocarburized steel and $45kg/mm^2$ of induction hardened steel, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.1620-1625
• /
• 2015

In this study, a variety of industrial gears, shafts, chains, rollers, mold, etc. are widely used inautomotive steel carbon steel for machine structural SM45C typical material used for the experiments. In order to cure the surface of the test piece after the rough grinding and fine grinding was performed in order polishing. Perform the surface hardening of SM45C lacal area by using a diode laser. The output of the laser diode and the feed rate to the process variable. Micro-hardness testing, microstructure testing, scanning electron microscope testing(SEM), the heat input to the analysis. After analyzing the experiment to compare the mechanical properties of the material. When using a diode laser to assess the soundness of the surface hardening. Accordingly, the process for deriving the optimum demonstrate the feasibility.

• Journal of Ocean Engineering and Technology
• /
• v.5 no.1
• /
• pp.71-80
• /
• 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 the Korean Society for Precision Engineering
• /
• v.22 no.11 s.176
• /
• pp.51-58
• /
• 2005

Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for automotive parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser heat treatment for the case of SM45C medium carbon steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide heat treatment area with a uniform hardness. From the results of the experiments, it has been shown that the maximum hardness is approximatly 780 Hv when the power and the travel speed of laser are 1,095 W and 0.6 m/min, respectively. In addition, the hardening width using the elliptical lens was three time larger than that using the defocusing of laser beam.

• Proceedings of the Safety Management and Science Conference
• /
• 2009.04a
• /
• pp.413-421
• /
• 2009

This paper investigates tensile characteristics of the stress aging heat-treated SM45C steel which are aging temperature at $250^{\circ}C$, $300^{\circ}C$, aging time at 1, 3 hours, and applied load at 300, 400N conditions by using acoustic emission. Most suitable aging condition was aging temperature $300^{\circ}C$, aging time 1 hour, and aging applied load 300N. And increased yield load 28.3% than non-treatment specimen in this condition. AE energy in elastic limit increased about 16.7 times than non-treatment specimen. When aging time is 3 hours, yield load decreased than other conditions that possibility is high to have itself defect on inside the specimen or coarse grain size precipitation is different in happened over-aging phenomenon. Especially, in case of $300^{\circ}C$, 3 hours and 400N condition appeared AE energy in elastic limit fairly high about 30 times than non-treatment specimen. This is considered by emit a lot of energies when material causes plastic deformation because the ductility increases on specimen by over-aging phenomenon.

• Journal of the Korean Society for Heat Treatment
• /
• v.12 no.1
• /
• pp.9-20
• /
• 1999

The effect of post oxidation, water-quenched after holding in air for 5~420 seconds or cooling or furnace cooling, on corrosion resistance and phase formation characteristics of the surface layer of SM20C and SM45C carbon steels after gas nirtrocarbursing in the $NH_3-5%CO_2-N_2$ gas atmosphere at $580^{\circ}C$ for 3hours is studied. The compound layers of two steels consist of ${\varepsilon}-Fe_{2-3}N$, ${\gamma}^{\prime}-Fe_4N$ and $Fe_3O_4$, phases, however, the quantity of ${\gamma}^{\prime}-Fe_4N$ phase increases for the furnace cooled specimen compared to that of air cooling specimen. With increasing $NH_3$ content in the gas mixture and also increasing the keeping time in the air after gas nitrocarburising, the ${\varepsilon}-Fe_{2-3}N$ phase of compound layer increases, while the decreased current density recognizing the improvement of corrosion resistance are shown. the passive current density of SM45C steel is lower than that of SM20C steel at the same nitrocarburising conditions.

• Journal of the Korean Society for Heat Treatment
• /
• v.20 no.5
• /
• pp.237-242
• /
• 2007

Friction coefficient of SM45C steel was surprisingly reduced with $H_2S$ and $C_3H_8$ gas during plasma sulf-nitriding. During the plasma sulf-nitriding, 100-700 sccm of $H_2S$ gas and 100 sccm of $C_3H_8$ gas were added and working pressure and temperature were 2 torr, $500-550^{\circ}C$, respectively. As $H_2S$ gas amount increased over 500 sccm, flake-like structures were developed on top of the nitriding layer and grain size of the nitriding layer were about 100 nm. The friction coefficient for the sample treated plasma sulf-nitriding under $N_2-H_2S$ gas was 0.4 - 0.5. The structure became more finer and amorphous-like along with $N_2-H_2S-C_3H_8$ gas and the nano-sized surface microstructures resulted in high hardness and significantly low friction coefficient of 0.2.