• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.17-20
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• 2000

In order to improve the sheet formability of the ferritic stainless steel, the through-thickness textures of the recrystallized sample was modified by means of a thermomechanical treatment. An annealing process between the cold rolling reductions modified the preferred orientations throughout the thickness, which resulted in the modification of the final cold rolling texture as well as the final recrystallization texture. With the help of the modification of the recrystallization texture by the intermediate annealing, improvement of the sheet formability, i.e. an increase of the Lankford value.

• Laser Solutions
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• v.17 no.2
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• pp.11-18
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• 2014

This research was conducted as a fundamental study to apply tailored blank welding technique into automotive production process. Specially we tried to apply the TWB technique to exhaust system. The materials used in this work were ferritic 439 stainless steel sheet with a thickness of 1.2mm and 0.8mm. Welding tests were conducted for BOP test and dissimilar thickness (0.8 to 1.2t) cases. Major process parameters were position of focus, travel speed, shielding gas and joint (gap) condition. As a result, there are nothing significant welding characteristic compare with TWB of carbon steel. Stainless steel shows the good weldability and mechanical properties (tensile, hardness and forming strength) also shows high level. Just problem is gap condition. However, also in this case, it shows not only good forming strength but also base metal fracture after tensile test. And to conclude, it is good opportunity to make lightweight design muffler using TB welding technique.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.349-356
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• 2011

This paper replaces a conventional austenitic stainless steel sheet to a ferritic stainless steel for the cost reduction of a pulsator cover of a washing machine. However, ferritic stainless steel has poor formability in comparison with austenitic one. The low formability of ferritic steel results in problems during stamping such as fracture, wrinkling, shape inaccuracy and so on. Design modification of the stamping tool is carried out with the aid of the finite element analysis for multistage stamping process of the pulsator cover. The simulation results show that fracture occurs on top of the product while wrinkles are generated by the excess metal near the wing part. Modification of the initial stamping die is performed to improve metal flow and to eliminate problems during the stamping process. Simulation with the modified design fully demonstrates that safe forming is possible without inferiorities.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.151-154
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• 1998

Stainless steel sheets are widely used to produce electrical appliances. But there are various problems occured in forming stainless steel sheets such as scratch, local fracture, earing. So the productivity of electrical appliances made of stainless steel sheets is decreased. And it is very important to improve the formability of stainless steel sheets. In this study, rectangular cup drawing tests have been carried out to obtain optimum process parameters for improving the formablity of stainless steel sheets. In the tests, selected process parameters are materials of dies and punches, lubricating conditions, and blank holding force. From the test results, we suggest the appropriate conditions to be applicable to the actual manufacturing processes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.397-400
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• 2009

When the metal sheet is subjected to the housing surface for fitting and insulating from harsh surroundings like fluid ingression or hot steam, both strength and formability have to be equally considered. In this regard, the main aim of this study is to design an apparatus of cost-effectively producing flexible fluted band with increasing the formability of embossed stainless steel sheet, which is utilized as a thermal insulation metal for housing ship engine exhauster. Designed to fabricate a maximum sheet width of 700 mm, this new apparatus consists of upper roll made of hard urethane and the female-etched lower roll made of SKD11, have a producing capacity up to 1-meter homogeneously embossed sheet for just 60 seconds. This machine is devised for the maximum operating efficiency from original sheet handling to machine setting. The embossing properties are characterized by 3-D profiling. After embossing plain metal sheet, both yield strength and elongation properties are improved simultaneously, indicating the effectiveness of the newly designed apparatus.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.679-684
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• 2011

Recently, STS 301L joints of side panels to frames for stainless steel rolling stock have been made out by using existing welding methods including Resistance Spot Welding, Laser Welding and Arc Welding. Most of the processes were jointed by spot welding because it is faster at welding and comparatively less expensive for investment in welding facilities than other methods. During spot welding, however, indentation of the metal surface was made due to pressure and melting property of welding. Moreover, since the melting metal was forced to periphery of the plate as indentation was made, sheet separation, which cracked apart between jointed sheets, was carried out. A slight deformation which resulted from sheet separation deteriorated the emotional quality of railway vehicles. This paper suggests that by processing conventional spot electrode tip appropriately, melting metal is able to push up around the processed part (Hollow Spot Electrode Tip) and prevent from being dislodged from first place to periphery. Consequently, sheet separation is remarkably decreased. Also, the emotional quality of appearance of stainless steel rolling stock is enhanced considerably.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.331-331
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• 2007

• Transactions of Materials Processing
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• v.28 no.6
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• pp.328-335
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• 2019

Demand for ultra-thin materials is increasing due to their light-weight and versatile properties. In this work, the formability of the ultra-thin stainless steel sheets of various thicknesses in the incremental sheet forming (ISF) process is investigated. The effects of the thickness on formability were evaluated with forming experiments of the truncated cone shape with 10° intervals. As the thickness of the material decreased, the maximum forming angle decreased and wrinkles also occurred quickly. The maximum forming angles in the truncated cone shape without the wrinkles for the thickness of 0.05 mm, 0.08 mm, and 0.1mm were 30°, 40°, and 50°, respectively. Wrinkles occurred in a twisted shape along the moving direction of the tool. As the material thickness increased, the size of the wrinkles increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1294-1298
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• 2005

In this study, combined micro press and surface finishing process are proposed to fabricate the micro nozzle array on a stainless steel sheet metal. In micro hole punching process the burr occurs inevitably, but the burr must be minimized in order to improve the quality and accuracy of the product. For this reason, subsequent magnetic field-assisted finishing technique is applied to remove the burr which exists around the nozzles for ink-jet printer head and proved to be a feasible for deburring by experiment. The deburring characteristics of sheet metals were investigated changing with polishing time and magnetic abrasive size. After the deburring, the burr size has remarkably reduced and roundness of the hole also has improved.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.689-694
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• 2013

A duplex stainless steel sheet with 1 wt.% gadolinium was fabricated for a neutron absorbing material with high strength, excellent corrosion resistance, and low cost as well as high neutron absorption capability. The microstructure of the as-cast specimen has typical duplex phases including 31% ferrite and 69% austenite. Main alloy elements like chromium (Cr), nickel (Ni), and gadolinium (Gd) are relatively uniformly distributed in the matrix. Gadolinium rich precipitates were present in the grains and at the grain boundaries. The solution treatment at $1070^{\circ}$ for 50 minutes followed by the hot-rolling above $950^{\circ}$ after keeping the sheet at $1200^{\circ}$ for 1.5 hours are important points of the optimum condition to produce a 6 mm-thick plate without cracking.