| Summary: | 碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 107 === The development of lightweight automobiles means that high tensile steel plate is widely used but its poor formability is an industrial problem. Hot-stamped steel exhibits high formability in the process of hot-working and retains has hardness and strength after die quench forming. This reduces the sheet thickness along and vehicle weight. However, the quenching decreases safety because toughness is reduced and brittleness is increased. Tailor welding is used to increase the strength of steel plate and to maintain a certain degree of toughness, but it is difficult to ensure the thickness of the plate and the welding procedure involves extra cost.
This study uses tailored hot-stamping to increase the strength of different parts of steel plates. There are four ways of tailored hot stamping, including partial heating, partial cooling, changing the die materials and increasing die gaps. This study uses a segmented hot stamping die for tailor-type hot stamping and uses simulation software to analyze the die and stamping manufacture. The results show that the DEFORM-3D simulated die heating condition matches the real outcome, with only 1.1% deviation as the temperature is increased to 500 °C. The difference in the thickness of the upshot are less than 1.5% after the Pam-Stamp simulation of the tailor hot stamping, which gives a profile of the stress and strain situations. In the simulation of a heat die at 350 °C the output hardness reaches Hv357 after cooling and massive Martensite structures are formed, but the practical value is only Hv250 and becomes Bainite, so Pam-Stamp is more suitable for stamping formability. The results for hot stamping show that the steel contains a microstructure of Martensite at a heat die level of Hv380~Hv430 on 150℃~250℃,Bainite and Martensite from Hv250~Hv280 on 300℃~400℃ and frame Pearlite & Ferrite from Hv180~ Hv230 above 450℃. The impact examination shows that the test piece for scale Hv470 is unstable for absorption, that for Hv180 is liable to depress and that at Hv270 has superior strength and energy. The material properties are increased by tailor-made hot stamping with a hot die of 350 ° C.
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