• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.207-210
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• 2008

The effects of boron additions in steels have long been recognized as very important, mainly with respect to hardnability of heat treatable steels. we investigated the effect of the microstructure and mechanical properties with cooling condition after heat treatment of the boron-treated(${\fallingdotseq}8{\sim}18ppm$) low carbon(${\fallingdotseq}0.2%C$) low alloy steel. The specimens were austenitised for 10 min at $910^{\circ}C$, cooled for the various periods of time from 10 sec to 30 sec or with water after forming for 15 sec. After cooling, mechanical properties were measured by tensile test and hardness test. For analysis of microstructure, Optical were carried out.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.3
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• pp.107-115
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• 2021

Al-Si coated boron steel has been widely used as commercial hot stamping steel. When the steel is heated at 900~930℃ for 5 min in an electric furnace, thickness of the coating layer increases as a consequence of formation of intermetallic compounds and diffusion layer. The diffusion layer plays an important roll in blunting the propagation of crack from coating layer to base steel. Change in microstructure and coating layer of Al-Si coated boron steel after conductive heating with higher heating rate than electric furnace has been investigated in this study. Conductive-heated steel showed the martensitic structure with vickers hardness of 505~567. Both intermetallic compounds in coating layer and diffusion layer were not observed in conductive-heated steel due to rapid heating. It has been found that the conductive-heating consisting of rapid heating to 550℃ which is lower than melting point of Al-Si coating layer, slower heating to 900℃, and then 1 min holding at 900℃ is effective in forming intermetallic compound in coating layer and diffusion layer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.499-500
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• 2009

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1355-1360
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• 2007

The use of high strength steels are gradually increasing to reduce the weight of automobile to improve the environmental problems and collision safety. To encounter the traditional disadvantages of high strength steels like as a poor formability and high springback, hot press forming has been developed. By this method, the strength of steel sheet is increased about three times of original one through die quenching process. In order to the design of hot press forming tools by using numerical simulation, the knowledge of mechanical and microstructural characteristics are required. This study show the mechanical and microstructural characteristics of a high strength boron-alloyed steel according to the various quenching conditions.

• Corrosion Science and Technology
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• v.4 no.3
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• pp.75-80
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• 2005

This work dealt with the evaluation of galvanic corrosion rate in a corrosion cell having annular gap of 0.5 mm between carbon steel 1018 and alloy 600 as a function of temperature and boron concentration. Temperature and boron concentration were ranged from 110 to 300 $^{\circ}C$ and 2000~10000 ppm, respectively. After the operating temperature of the corrosion cell where the electrolyte was injected was attained at setting temperature, galvanic coupling was made and at the same time galvanic current was measured. The galvanic corrosion rate decreased with time, which was described by corrosion product such as protective film as well as boric acid deposit formed on the carbon steel with time. From the galvanic current obtained as a function of temperature and boron concentration, it was found that the galvanic corrosion rate decreased with temperaturewhilethe corrosionrate increasedwith boronconcentration. The experimental resultsobtained from galvanic corrosion measurement were explained by adhesive property of corrosion product such as protective film, boric acid deposit formed on the carbon steel wall and dehydration of boric acid to be slightlysolubleboric acid phase.Moreoverthe galvaniccorrosionrate calculatedusing initialgalvaniccoupling current instead of steady state coupling current was remarked, which could give us relatively closer galvanic corrosion rate to real pressurized water reactor.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.269-275
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• 2016

In this study, the mechanical properties and the neutron shielding rate of concrete with the borosilicate glass and the amorphous boron steel fiber were investigated. The measures of this investigation includes air contents, slump loss, compressive strength, static modulus of elasticity, compressive toughness, flexural strength, flexure toughness and neutron shielding rate. As a result, the neutron shielding rate of the concrete with borosilicate glasses increased even though the compressive strength and flexural strength decreased in comparison with that of plain concrete. Also, the mechanical toughness and the neutron shielding rate of the concrete with amorphous boron steel fiber increased in comparison with that of plain concrete.

• Transactions of Materials Processing
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• v.20 no.5
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• pp.362-368
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• 2011

For the purpose of improving crashworthiness qualities and maximizing weight saving efficiency, TWB's(tailor welded blanks) of quench-hardenable boron steel sheet formed by hot stamping processes has been used for automotive BIW (body in white) applications. In this work, the flow behaviors of TWB of quench-hardenable boron steel sheet were investigated in uniaxial tension tests at elevated temperature. TWB's having a uniform thickness of 1.4mm were fabricated by laser welding. Specimens with two weld line directions were used to test the mechanical property and reliability of the weld zone. After heating at $950^{\circ}C$ for 5min, the specimens were subjected to tension test at 650, 700 and $800^{\circ}C$ with a strain rate of 0.01 /s and at $700^{\circ}C$ with strain rates of 0.01, 0.1 and 1/s. The ultimate strength of the weld zones was higher than that of the base materials at 650 and $700^{\circ}C$, but was similar to the base metal at $800^{\circ}C$. Fracture occurred at the base material at 650 and $700^{\circ}C$, but at the weld zone at $800^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.319-324
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• 2012

The hot-stamping technique is a forming method for manufacturing high-strength parts, in which the part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the microstructure and mechanical properties according to the heat-treatment conditions. Die-quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching has a tensile strength of 1454 MPa and an elongation of 6 %. It has 94 % of the tensile strength of the base metal (1522 MPa). These properties can provide practical information for the use of boron steels for hot stamping.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.383-391
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• 2011

The hot-stamping technique is used to manufacture high-strength parts by press forming by heating at a temperature above the Austenite transformation temperature and then rapid cooling. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to show the microstructures and to investigate the mechanical properties under different heat-treatment conditions. The heat treatment of water quenching was conducted at the various temperatures and different elapsed times. These can be practical data useful when boron steels are used for hot stamping. Furthermore, the microstructures and mechanical properties of the spot-welded specimen with coatings and counterpart materials (SPRC 340, SPRC 590) is investigated in order to determine the welding characteristics of boron steel at different welding condition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.87-94
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• 2017

Hot stamping processes are possible for tensile strength 1.4 GPa but the strength reduction is appeared from the cooling performance unbalance. And the strength of roll forming process is below than that of hot stamping process owing to using the steel which is lower strength of boron steel. In this study, We provide roll forming process asssisted high-frequency induction heating to solve the problem of conventional one. The experiments were carried out at under various sill side part conditions: high-frequency induction heating conditions of 15, 18, 21, 24, 27 and 30 kW. The high-frequency induction heating temperature was checked with Infrared camera and the sill side parts of mechanical properties and microstructure were measured. The heating temperature of high frequency induction was measured to max $850^{\circ}C$ under the coil power of 30 kW. The tensile strength was 1.5 GPa and hardness was 490 Hv. The martensite structure was discovered under coil power of 30 kW. The weight of steel material sill side having thickness 1.5 mm and the boron steel sill side having thickness 1.2 mm were compared to weight effect. The boron steel sill side reduced 11.5% compared to steel. Consequently, manufacturing process of 1.5 giga-grade's sill side part was successfully realized by the roll forming assisted high-frequency induction heating methods.