• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.300-301
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• 2007

In this study, it is investigated that sheet characteristics of high strength steel sheets and effect of springback. High strength steel sheets has got attention in automobile industry of high strength and high formability. Springback is a common phenomenon in sheet metal forming, caused by the elastic recovery of the internal stresses after removal of the tooling. However, the information in deformation behavior of high strength steel sheets, including bending and sheet characteristics and springback, is not enough until now. In this research, the V-bending experiment and analysis have been done to obtain the information of springback of high strength steel sheets. Tensile test for high strength steel sheets was done to got tensile properties of elastic modulus and flow stress of the material. It analyzed springback according to the sheet characteristics with using roll-forming model. FE-Simulation used DEFORM-$3D^{TM}$.

• Resources Recycling
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• v.9 no.1
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• pp.15-20
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• 2000

The effect of different kinds of steel scraps, the raw material in the manufacturing of nodular cast iron, on the microstructures and mechanical properties has been investigated Different grades were produced by changing the steel scraps. When nodular graphite cast iron was produced by using Zn rich steel scrap, such as galvanized steel sheet and auto body sheet, mechanical properties were deteriorated due to the decomposition of graphite, so close control must be maintained over this element. Tensile strength and hardness of nodular graphite cast iron which were manufactured by using Sb rich steel scrap were increased while elongation was decreased due to the increased amounts of pearlite within matrix. Mn and Cr contents in the structural steel sheet scrap or malleable iron scrap increased tensile strength and hardness of nodular graphite cast iron by facilitating the formation of pearlite.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.12
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• pp.617-622
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• 2006

It is necessary to measure precisely the magnetic characteristics of electrical steel sheets under rotating magnetic fields, to obtain an accurate numerical performance analysis of electric machines made of electrical steel sheets. In this paper, the two dimensional magnetic characteristics of an electrical steel sheet are measured and explained under rotating magnetic fields using a two-axes-excitation type single sheet tester (SST). Through experiments, the magnetic properties, under rotating magnetic fields, of a non-oriented and grain oriented electrical steel sheet were measured respectively. In addition, the iron losses due to not only the alternating magnetic fields, but also rotating magnetic fields were measured. These experimentally measured results can evidently be applied to the analysis of iron losses in electrical machines.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.8-12
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• 2012

This study aims to analyze the formability property of surface texturing processed automotive steel sheet for improving the sheet forming property. In the paper, the effect of cavities fabricated using the laser surface texturing technique on automotive high strength steel sheets was studied. The frictional behavior of the sheet drawing is a function of interface parameters such as sheet surface roughness, holding force, contact pressure, etc. For these reasons, automotive steel researchers want to optimize the surface topography of automotive steel sheets in order to enhance the formability. Therefore, this study presents the behavior of deformation of a laser surface texturing steel sheet by considering the frictional operation during the deep drawing process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.4
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• pp.354-361
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• 2008

Cold rolled steel sheet for automotive was treated by Ar/$O_2$ atmospheric pressure plasma to improve the adhesive bonding strength. Through the contact angle test and calculation of surface free energy for cold rolled steel sheet, the changes of surface properties were investigated before and after plasma treatment. The contact angle was decreased and surface free energy was increased after plasma treatment. And the change of surface roughness and morphology were observed by AFM(Atomic Force Microscope). The surface roughness of steel sheet was slightly changed. Based on Taguchi method, single lap shear test was performed to investigate the effect of experimental parameter such as plasma power, treatment time and flow rate of $O_2$ gas. Results shows that the bonding strength of steel sheet treated in Ar/$O_2$ atmospheric pressure plasma was improved about 20% compared with untreated sheet.

• Transactions of Materials Processing
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• v.29 no.1
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• pp.27-36
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• 2020

The Goss texture component of {110}<001> is well known as one of the best texture components to improve the magnetic properties of electrical steel sheets. The small amount of the Goss texture component is obtained at the surface of the steel sheet by shear deformation due to friction between the steel sheet and the roll during conventional symmetric rolling. This study aims to identify a method to obtain high intensity of the Goss texture component not only at the surface but in the whole layer of the steel sheet by shear deformation of asymmetric rolling. Low carbon steel sheets, which have different initial texture, were asymmetrically rolled by about 50%, 70%, and 80%. The pole figures of the top, center, and bottom layers of the initial and asymmetrically rolled low carbon steel sheets were measured by an X-ray diffractometer. Based on the measured pole figures of these samples, the intensities of the main texture components were analyzed for the initial and asymmetrically rolled low carbon steel sheets. As a result, the initial low carbon steel sheet with the γ-fiber component showed a higher intensity of the Goss texture component in the whole layer than the steel sheet with other texture components after asymmetric rolling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1807-1818
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• 1991

The frictional characteristic of Zn-Ni electrogalvanized steel sheet was investigated by experimental procedures. To clarify the effect of surface property on the frictional characteristic of Zn-Ni coated steel sheet, Micro-hardness test, SEM analysis and X-ray diffraction analysis were carried out. Coefficients of friction for various stamping lubricant and Ni content in coated layer were measured by a draw bead friction test. The results show that frictional characteristic is very sensitive to Ni content of coated layer and depends on stamping lubricant. For Ni content less than about 11%, selection of proper lubricant is necessary to obtain low coefficient of friction in Zn-Ni coated steel sheet such as in case of cold rolled steel sheet.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.6
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• pp.283-291
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• 2012

In order to increase the anti-oxidation property during the tailor welding blanked hot press forming process for a high strength boron steel sheet, we performed a different coating method on the boron-steel sheet such as 87% Al - 13% Si and Fe - 8.87 Zn dipping plating procedure. However, during laser welding process, the Al-Si coated steel sheet has showed a low tensile strength and about half value of elongation than the original boron-steel sheet. Aluminum and silicon, elements of coating layer were diffused into the boron-steel matrix and have shown a low strength result than non-coated specimen. On the other hand, Zinc-coated boron-steel has expectedly showed a excellent tensile strength and micro-harness value in the welded area like original boron-steel.

• Transactions of Materials Processing
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• v.19 no.4
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• pp.236-241
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• 2010

The frictional behavior of bare steel sheet highly depends on surface roughness. It was investigated that the change of surface roughness of bare steel sheet due to deformation for each forming mode. The flat type friction test was done to check the effect of surface roughness change on frictional characteristics of bare steel sheet. As increasing the deformation, the Ra value was increased at stretching forming mode and drawing forming mode, however the change of Pc showed different trends. The Pc was decreased as increasing stretch deformation but increased at compression deformation. At drawing forming mode, the friction coefficient was increased as deformation was increased after initial big drop with drawing oil. As deformation was increased, the friction coefficient was decreased with drawing oil at stretching forming mode. The results show that the deformation changes the surface roughness and frictional characteristics of steel sheet but the effect depends on the forming mode.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.228-229
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• 2007

As one way of weight saving of the vehicle, 1-piece typed lower control arm has been developed using high strength hot rolled steel sheet. In order to overcome the edge splitting problem during edge flanging or burring process, HER (hole expansion ratio) value of steel sheet was primarily considered. The strength grade of steel sheet and the shape were optimized utilizing Taguchi method.