• 소성∙가공
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• 제3권1호
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• pp.38-50
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• 1994

Fundamental deformation mechanism and plastic behavior of AISI304 austenitic stainless steel were investigated to evaluate press formability. Local and uniform deformation capacity of AISI304 steel were compared to those of ferritic AISI430 steel and Al killed low carbon steel. Nine kinds of austenitic stainless steels having different austenite stabilities were made in laboratory scale to examine the transformation behavior in various deformation mode and variation of mechanical properties. Deformation path and strain distributions along edge corner of commercial sink die were illustrated and effect of austenite stability on press forming of sink die was clarified with experiments using square cup drawing tools.

• KSTLE International Journal
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• 제3권1호
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• pp.17-22
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• 2002

Roughing of tool steel in its hardened state represents a real challenge in the die and meld industry and process improvement depends on research of tool material, coating technique, and lubrication. However, roughing of hardened steels generates extreme heat and without coolant flooding, tool material cannot withstand the high temperature without choosing the right tools with proper coating. This research conducted milling tests using coated ball end mills to study effects of cutting conditions and geometric parameters of ball end mills on the machinability of hardened tool steel. KP4 steel and STD 11 heat treated steels were used in the dry cutting as the workpiece and TiAIN coated ball end mills with side relief angle of 12$^{\circ}$ was utilized in the cutting tests. Cutting forces, tool wear, and surface roughness were measured in the cutting tests. Results from the experiments showed that 85 m/min of cutting speed and 0.32 mm/rev of feed rate were optimum conditions for better surface finish during rough cutting and 0.26mm/rev with the same cutting speed are optimum conditions in the finish cutting.

• 소성∙가공
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• 제15권2호
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• pp.164-171
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• 2006

The die development of the high-strength steel sheet is very different with that of the common steel sheet. Especially, the springback problem of the high-strength steel is serious in the stamping process. This paper showed the optimized die development of the high-strength steel sheet which was based on the experimental measured and simulated springback auto panel stamping process.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.55-58
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• 2008

Hydroforming is a forming technology in which a steel tube is set in a die and formed to fit a specified shape by applying hydraulic pressure from inside the tube while also applying force in the tube axial direction (axial feed). In present study, the entire design process chain for an automotive cross-member was simulated and developed using hydroforming technology on high-strength steel. The part design stage required a feasibility study. The process was designed using computer-aided design techniques to confirm the actual hydroformability of the part in detail. The possibility of using hydroformable cross-member parts was examined using cross-sectional analyses, which were essential to ensure the formability of the tube material for each forming step, including pre-bending and hydroforming. The die design stage included all the components of a prototyping tool. Press interference was investigated in terms of geometry and thinning.

• 소성∙가공
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• 제15권8호
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• pp.609-614
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• 2006

Micro-alloyed steels(MA steels) for cold forging was developed to replace the usual quenched and tempered steel. MA steels have several advantages over the conventional quenched and tempered carbon steels. First of all, energy consumption could be lowered due to the elimination of spherodizing annealing and quenching/tempering heat treatment. Also, bending during quenching could be avoided when MA steels are applied for manufacturing of long fastener parts. However, larger amount of load is exerted on the dies compared than in the case of conventional mild steels, which might lead to the earlier fracture of dies, when MA forging steels are applied in forging practice. Therefore, die lift could be a critical factor to determine whether HA forging steels could be widely applied in cold forging practice. In the present study, authors have investigated the forging characteristics of non-heat treated micro-alloyed steel by using a series of experimental and numerical analyses. Firstly, microstructural features and its effect on the deformation behavior have been studied. Numerical analysis has been done on the forging of guide rod pin to investigate for the optimization of forging process and die stress prediction.

• 한국표면공학회지
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• 제49권6호
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• pp.587-594
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• 2016

Various surface treatments and thin film coating processes on the surface of injection die steel have been developed to extend the life. Most of previous studies were mainly focused on investigating the wear and static bonding behavior of thin films. In this study complex surface treatments of DLC coating combined with ion nitriding were applied to increase fatigue life and wear resistance. Ion nitriding, DLC coating, and DLC coating following nitriding on the surface of Fe-3.0Ni-0.7Cr-1.4Mn-X steel were investigated to uncover the beneficial effect which is applicable to injection die. The effect of various surface treatments and coating conditions on high cycle fatigue resistance was studied. Surface morphology change during fatigue tests were observed with AFM. Fatigue life of the die steel increased by 10 to 1,000 times at the various level of stress amplitudes in the condition of DLC coating following the ion nitriding for 3 hrs comparing with the only DLC coated condition.

• Journal of Magnetics
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• 제16권3호
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• pp.300-303
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• 2011

The effect of the hot-compaction temperature on the microstructure and magnetic properties of anisotropic nanocrystalline magnets was investigated. The hot-compaction temperature was found to impact both the magnetic properties and the microstructure of die-upset magnets. The remanence of the isotropic precursor increases slightly with the improved hot-compaction temperature, and the grains start to grow on the flake boundary at higher hot-compaction temperatures. After hot deformation, it was found that the change in the magnetic properties was the inverse of that observed with the hot-compaction temperature. Microstructural investigation showed that die-upset magnets inherit the microstructural characteristics of their precursor. For the die-upset magnets, hot pressed at low temperature, scarcely any abnormal grain growth on the flake boundary can be seen. For those hot pressed at higher temperatures, however, layers with large equiaxed grains could be observed, which accounted for the poor alignment during the hot deformation, and thus the poor magnetic properties.

• 한국재료학회지
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• 제22권4호
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• pp.169-173
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• 2012

Recently, various attempts to produce a heat sink made of Al 6xxx alloys have been carried out using die-casting. In order to apply die-casting, the Al alloys should be verified for die-soldering ability with die steel. It is generally well known that both Fe and Mn contents have effects on decreasing die soldering, especially with aluminum alloys containing substantial amounts of Si. However, die soldering has not been widely studied for the low Si aluminum (1.0~2.0wt%) alloys. Therefore, in this study, an investigation was performed to consider how the soldering phenomena were affected by Fe and Mn contents in low Si aluminum alloys. Each aluminum alloy was melted and held at $680^{\circ}C$. Then, STD61 substrate was dipped for 2 hr in the melt. The specimens, which were air cooled, were observed using a scanning electron microscope and were line analyzed by an electron probe micro analyzer. The SEM results of the dipping soldering test showed an Al-Fe inter-metallic layer in the microstructure. With increasing Fe content up to 0.35%, the Al-Fe inter-metallic layer became thicker. In Al-1.0%Si alloy, the additional content of Mn also increased the thickness of the inter-metallic layer compared to that in the alloy without Mn. In addition, EPMA analysis showed that Al-Fe inter-metallic compounds such as $Al_2Fe$, $Al_3Fe$, and $Al_5Fe_2$ formed in the die soldering layers.

• 한국주조공학회지
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• 제30권2호
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• pp.76-82
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• 2010

Effect of reaction time and sludge formation on the thickness of die soldering reaction layer has been studied in Al-9Si-0.3Mg casting alloy. Ternary ${\alpha}_{bcc}-Al_8Fe_2Si$ and ${\alpha}_{hcp}-Al_8Fe_2Si$ intermetallic compounds formed at the interface of SKD61 tool steel by interaction diffusion of Al, Fe and Si atoms after 0.5hr and 6hr immersion time, respectively. Binary ${\eta}-Fe_2Al_5$ additionally formed at the interface of SKD61 tool steel after 10hr immersion time. Thickness of soldering reaction layer in die surface increased as immersion time increased from 0.5hr to 24hr. Sludge formation was ascertained in the samples which were immersed in the melts more than 10hr. Reaction of die soldering after sludge formation was more accelerated than that of before sludge formation due to a decrease in Fe content, followed by higher diffusion rate of Al in the melt by sludge formation.

• Design & Manufacturing
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• 제15권3호
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• pp.13-18
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• 2021

In plate forming technology, cylindrical drawing process is widely used in industry due to technological development. In this study, we used stainless steel 3042B and stainless steel 304J1, which are the most commonly used materials in the production of cold and hot water tanks for water purifiers, among cylindrical drawing products. Under the same conditions, the thickness of the sidewall of the product formed by drawn experiment was studied. As a result of the experiment, the bottom thickness of stainless steel 304J1 was considered to be thick. It is judged that the defect rate can be reduced by changing the breaking phenomenon of the floor surface of the cold and hot water bottles to the material of stainless steel 304j1. Stainless steel 304 2B material shows a sharp change in thickness from punch corner R to sidewall position, while stainless steel 304J1 material showed a uniform change from punch corner R to sidewall position. Stainless steel 304J1 material is considered to improve the clamping of the product in the process of extracting the product after hand drawing. The appearance of stainless steel 3042B products is considered to produce more wrinkles in the flange, which exerts greater tensile force on the sidewall during molding, resulting in uneven sidewall thickness.