Corner Strengthening by Local Thickening and Ausforming Using Planar Compression in Hot Stamping of Ultra-High Strength Steel Parts

Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners are thickened by compressing the blank in the planar direction with the upper and lower dies while blocking the movement of both edges with stoppers in the latter stage of forming. Thickening of the corners largely heightens the strength of the formed parts. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching. For a hot hat-shaped part, a 30% increase in thickness and a 530 HV20 hardness around the corners were attained. The bending rigidity and strength of the formed parts thickened by 30% in the corners increased by 25% and 20%, respectively. In addition, the improvements of the part shape accuracy and the sidewall quenchability were obtained.

PRACA ZMIANOWA W ZAKŁADZIE DEKORUJĄCYM OPAKOWANIA SZKLANE

System pracy zmianowej jest terminem określającym sposób organizacji pracy w instytucjach i zakładach, gdzie ich funkcjonowanie nie może zostać przerwane. Wiąże się to z całodobowym i zmiennym rytmem pracy, który poprzez zaburzenie okołodobowych rytmów biologicznych negatywnie wpływa na organizmy pracowników. U pracowników zmianowych często zauważa się występowanie zaburzeń sennych oraz dolegliwości układu trawiennego i poznawczego. Ponadto ta grupa pracowników jest bardziej narażona na choroby serca, otyłość czy cukrzycę. Celem niniejszej publikacji jest zbadanie, jak praca zmianowa wpływa na zdrowie pracowników działu sitodruk i hot stamping, zatrudnionych w zakładzie dekorującym opakowania szklane. W artykule wytłumaczono, na czym polega system pracy zmianowej oraz opisano, jak praca zmianowa może wpływać na organizmy ludzkie. Ponadto przedstawiono charakterystykę zakładu dekorującego opakowania szklane. Dalsza część poświęcona jest analizie, która polega na przeprowadzeniu wśród pracowników ankiety badającej występujące u nich dolegliwości. Ponadto wpływ pracy zmianowej został zbadany i oceniony na podstawie wypełnionych przez pracowników dobowych profili senności i zmęczenia. Badania pozwoliły na wywnioskowanie, iż najczęstszymi dolegliwościami są zmęczenie i zaburzenia snu. Następnie zaproponowane zostały rozwiązania, które mogą poprawić i pozytywnie wpłynąć na samopoczucie zatrudnionych.

Performance Comparison of Zn-Based and Al–Si Based Coating on Boron Steel in Hot Stamping

The coatings of boron steels play an important role in affecting the quality of hot stamping parts, so it is important to evaluate the hot stamping performance of coatings before designing processes. Taking the U-type hot stamping part of boron steel as research objects, the surface quality, microstructure and temperature variation of samples with GA (galvannealed), GI (galvanized) and Al–Si coatings were observed and analyzed to evaluate the anti-oxidation, forming and quenching performances of different coatings. The results show that all the GA, GI and Al–Si coatings could provide good oxidation protection and also act as the lubricants for avoiding the friction damage of sample substrates and die-surface. But the different compositions of GA, GI and Al–Si coatings will contribute the different colors. Under the same deformation degree, the Al–Si coating can provide the best substrate protection and the GI coating will induce cracks in the substrate because of the liquid metal-induced embrittlement phenomenon. There is no significant difference between the quenching performances of GA, GI and Al–Si coatings, and the thermal conductivity of the GI coating is slightly better than Al–Si and GA coatings.

Design and Development of a Micro-LDH Apparatus to Determine Formability of Sheet Metal Under Hot Stamping Conditions Using Gleeble

In the last few years, demand for hot stamped components has increased in the automotive industry. Determination of formability under hot stamping is challenging due to elevated temperature, fast cooling and high punch velocity. Although there was various strive for formability determination but had limitations with experiments like non-uniform heating of specimen, non-uniform strain and temperature distribution. Therefore, in this work, an experimental apparatus was developed to determine formability at room temperature, high temperature, hot stamping conditions, and any complex process cycle involving heating and cooling. New specimen was designed to produce different strain paths, uniform and homogenous temperature distribution with the help of FEM software using thermomechanical and thermoelectrical simulation. A micro hemispherical dome based experimental apparatus was designed using Solidworks. The designed apparatus was used in conjunction with the thermo-mechanical simulator (Gleeble-3800). Thermomechanical analysis was done in PAM STAMP software to optimize specimen size and shape to get uniform strain distribution and different strain paths. A thermoelectric FEM model was developed using Abaqus 6.14 to optimize the temperature distribution in the specimen. The developed model enables choosing the appropriate polarity of the electrical cable connection to achieve uniform temperature distribution in the specimen. Strain path and temperature profiles for experiment and simulation were compared. Further, a forming limit curve was developed using the designed apparatus to verify the feasibility of the apparatus. For feasibility test of apparatus, hot stamping process was selected. This new design apparatus can be used for a range of temperatures up to 1000 °C, hot stamping conditions, and for different materials (aluminium, magnesium alloys, different grade of steel, etc.). It concludes that the connection of different polarities of electrical cable was critical for homogenous and uniform temperature distribution in specimens.