• 대한기계학회논문집A
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• 제20권12호
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• pp.3899-3908
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• 1996

In order to clarify the effects of nonmetallic inclusion contents insteels (SM45C & SCM440) on the tool life, cutting experiment was performed under various cutting conditions. Tool life, cutting force, roughness of machined surface and cutting mechanism are examined on these two kinds of steel. The following conclusions were obtained from the analysis (1) Cutting force of the steels was not affected by chemical component and nonmetallic inclusion. (2) If the rate of amount, Ca/S has a value grater than about 0.2 and addition of less amount of Al, Mn, tool wear of tips decreasesinturning. (3) It is also proved that higher contents of nonmetallic inclusion improve roughness of the surface. (4) Less amount of Ca, higher amount of S, Mn and Al improve the chip breakability.

• 한국표면공학회지
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• 제31권5호
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• pp.266-277
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• 1998

The effects of $H_2S$ gas ratio, temperature and time on the case depth, hardness, and sulfide and nitride formation on the surface of sulfnitrided SCM440 steel have been studied by micro-pulse plasma technique. The thickness of compound layer of sulfide and nitride increased with the increase of time, temperautre and $H_2S$ gas ratio. But surface hardness decreased with the increase of soft sulfide layer because the hard nitride layer formed beneath the sulfide. The thickness of sulfide layer was about 10$\mu\textrm{m}$ abpve 0.0088% of $H_2S$ gas. The highest surface hardness of the compound layer was Hv835 at $530^{\circ}C$, 1hr and 0.06% of $H_2S$ gas. X-ray diffraction indicated that the surface products were $Fe_{1_x}S$, $Fe_{2.5}N$ and $Fe_4N$. It was confirmed by EPMA that sulfide only existed in the surface.

• 한국기계기술학회지
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• 제13권3호
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• pp.31-37
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• 2011

The purpose of this study is to investigate cutting characteristics and wear behavior in SCM440 steel with different cutting tools, CBN(Cubic Boron Nitride) and coated CBN. During the test coated CBN tool especially with TiAlN showed better wear resistance behavior than orginal CBN tools. In the interrupted cutting condition, axial groove affected tool surface with impact force during the turning operation. For advantageous turning parameter in the interrupted process it is recommendable that lower speed. Also surface roughness showed better behavior in the coated CBN tool conditions than normal CBN conditions. Mainly this is caused by reduced friction between material and tool surface with coated layer.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 추계학술발표 개요집
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• pp.165-169
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• 1995

This paper deals with determining the proper friction welding condition and analyzing mechanical in of friction welded joints of sintered carbide tool materials (SKNM50 for the blade part of press punch) to alloy steel (SCM440 for the shank part of press punch), the alloy steel to aluminum(A6061 for the interlayer material between the blade part and the shank) and sintered carbide tool materials to aluminum. And also acoustic emission test will be carried out during fiction welding to evaluate the weld quality.

• 한국재료학회지
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• 제29권4호
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• pp.258-263
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• 2019

Since the directly bonded interface between TiAl alloy and SCM440 includes lots of cracks and generated intermetallic compounds(IMCs) such as TiC, FeTi, and $Fe_2Ti$, the interfacial strength can be significantly reduced. Therefore, in this study, Cu is selected as an insert metal to improve the lower tensile strength of the joint between TiAl alloy and SCM440 during friction welding. As a result, newly formed IMCs, such as $Cu_2TiAl$, CuTiAl, and $TiCu_2$, are found at the interface between TiAl alloy and Cu layer and the thickness of IMCs layers is found to vary with friction time. In addition, to determine the relationship between the thickness of the IMCs and the strength of the welded interfaces, a tensile test was performed using sub-size specimens obtained from the center to the peripheral region of the friction-welded interface. The results are discussed in terms of changes in the IMCs and the underlying deformation mechanism. Finally, it is found that the friction welding process needs to be idealized because IMCs generated between TiAl alloy and Cu act to not only increase the bonding strength but also form an easy path of fracture propagation.

• 한국정밀공학회지
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• 제31권1호
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• pp.35-42
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• 2014

Recently, in industry field, many researchers are looking for ways to reduce the use of lubricant because of environmental and economical reasons. MQL lubrication is one of many lubrication technologies. The aim of this study is to evaluate the machinability considering lubrication methods and taper angles of workpieces for turning of SCM440. Workpieces of two shapes such as workpiece with and without taper angle are used. And two lubrication methods such as MQL and Wet have been considered. And cutting force and surface roughness are used as characteristic values. Cutting speed, feed rate, injection angle and distance are used as design parameters. The characteristic values were statistically analyzed by Taguchi method. From the results, main effects plot and importance of each parameter according to conditions are analyzed. Finally, this study has been suggested the optimum machining conditions according to the lubrication methods, machining conditions and shape of workpiece.

• 한국생산제조학회지
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• 제26권3호
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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.

• 한국정밀공학회지
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• 제30권8호
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• pp.779-784
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• 2013

Increased efficiency and improved performance associated with light-weight materials were investigated in this study. Numerous studies have investigated surface treatments to improve the fatigue strength of metals. Laser heat treatment is a promising method because the power and spot size can be easily controlled, allowing a small heat affected zone (HAZ). However, changes in the material properties can result; in particular, the material can become more brittle. In this study, a combination of laser heat treatment and vibration peening was proposed to increase fatigue strength without changing the material characteristics. SCM440H was investigated experimentally, and specimens were tested using a giga-cycle ultrasonic fatigue tester. The results show that the combination of these two processes significantly increased the fatigue strength and, furthermore, different fracture types were observed after a small and large number of cycles.

• 열처리공학회지
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• 제4권3호
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• pp.54-62
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• 1991

The effect of tempering temperature on the ultrasonic propagation velocity at SCM 440 steel quenched from $870^{\circ}C$ and $1000^{\circ}C$ has been studied by metallurgical and crystallographical observation. The measurements of ultrasonic velocity were made on the specimen by appling an immersion ultrasonic pulse-echo technique with a constant frequency of 10 MHz. The quenched microstructure of this steel was a lath martensite. As the tempering temperature was increased, the martensite was transformed into the tempered martensite composed of cementite and carbide. The ultrasonic velocity increased with increasing the tempering temperature. It was thought that these were resulted from the microstructural transformation. The change of ultrasonic propagation velocity with quenching and tempering heat treatment was resulted from microstrain due to the change of internal stress. Considering these results concerning to the change of ultrasonic propagation velocity. the phenomena of microstructural transformation were estimated. Consequently, it was thought that the degree of quenching and tempered heat treatment of steel could be nondestructively evaluated with the change of ultrasonic propagation velocity.

• 열처리공학회지
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• 제7권3호
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• pp.184-189
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• 1994

The heat treatment charaterristic of SCM 440 and B 16 steels has been investigated in various condition(A, B and C) to the effect of heat treatment on mechanical properties, and the following results were obtained. 1. We are obtained a good nitriding characteristic in bainitic structure than other heat treatment cycle in our experiment. 2. Fatigue characteristic has shown in order of B)C)A condition as heat treatment cycle. 3. The effective hardening depth and fatigue characteristic has been excellented in B 16 than SCM 440 after the nitriding and Q. T for Band C condition. 4. Nitriding depth has been increased in addition of Cr, V and the nitriding efficiency is increased as easiness of banite formation to wide range of cooling rate by addition of Mo. 5. The depth of compound layer in parallel surface, notched slop plane and notched bottom has been varied to the nitriding depth of 5, 4 and 3 ${\mu}$ in relatively uniform pattern after 10h nitriding treatment for SCM 440 into A condition.