Lightweight design is one of the development trends of the automobile industry. An effective way to achieve lightweight auto bodies is to use AHSS （advanced high strength steel ） for the safety components of automob...Lightweight design is one of the development trends of the automobile industry. An effective way to achieve lightweight auto bodies is to use AHSS （advanced high strength steel ） for the safety components of automobiles. This study has taken doorsill reinforcements made of martensite AHSS as the object ,and performed research on the AHSS roll forming technologies and prototype development of typical asymmetric open components. By means of finite element analysis （FEA） and simulation,studies have been carried out on the springback and edge wave defects during AHSS roll forming ,and an optimized process design has been achieved. The generation mechanisms of vertical bows ,horizontal cambers, twists,pre-punched hole distortion and cut end flare have been analyzed,and solutions to these defects have been given. In addition,tesing of the roll forming process for AHSS has been conducted and typical samples with required dimensional accuracy have been manufactured. This study has provided technical support for the large-scale application of AHSS.展开更多
Improving the galvanizability of high silicon advanced high strength steels （AHSS） is a practical technical challenge. In this study, spot defects on an industrial hot dip galvanized （GI） sheet of an AHSS with 1.5...Improving the galvanizability of high silicon advanced high strength steels （AHSS） is a practical technical challenge. In this study, spot defects on an industrial hot dip galvanized （GI） sheet of an AHSS with 1.5 % Si has been studied in-depth. The surface morphologies of spot defects before and after partial and complete removal of the Zn layer, as well as the interface between the outermost coating layer and the sheet substrate were characterized using optical microscopy （ OM）, scanning electron microscopy （ SEM）, a 3-D optical profiler, energy dispersive spectroscopy（ EDS ） and focused ion beam （FIB） analysis. The most outstanding spot defect on the normally coated area of the steel sheet has a diameter of approximately 500μm, with the following characteristics. In the central region of the spot defect,Zn is barely coated and the sheet substrate is covered by a thin silicon oxide film with dispersed Zn-Fe intermetallics. At the periphery of the spot defect, a burst structure of Zn-Fe intermetallics forms on the sheet substrate. Outside the spot defect where the Zn layer is normally coated, there is a continuous Fe2Al5 inhibition layer between the Zn coating and the sheet substrate. These results indicate that a silicon oxide film forms on the substrate during annealing prior to hot dipping, thus preventing the formation of the Fe2Al5 inhibition layer during hot dipping. This causes spot defects on high Si AHSS sheets.展开更多
The aim of this research study was to determine optimal resistance spot brazing parameters for joining between AHSS and AISI 304 stainless steel by using filler metal. The key parameters investigated in this study con...The aim of this research study was to determine optimal resistance spot brazing parameters for joining between AHSS and AISI 304 stainless steel by using filler metal. The key parameters investigated in this study consist of the brazing current, electrode pressure and brazing time. The Taguchi method was applied to the design of experiments. Signal-to-Noise ratio was introduced in the study to identify optimal levels from the process where input parameters yield increased shear strength. Brazing was thus implemented with 5,000A brazing current, 0.70 MPa electrode pressure, and 1.50s brazing time. The maximum shear strength obtained was 54.31 N·mm^-2 in accordance with input parameter settings. In addition, Cu-rich phase and Ag0.4Fe0.6 intermetallic phases were found at the interface zone.展开更多
文摘Lightweight design is one of the development trends of the automobile industry. An effective way to achieve lightweight auto bodies is to use AHSS （advanced high strength steel ） for the safety components of automobiles. This study has taken doorsill reinforcements made of martensite AHSS as the object ,and performed research on the AHSS roll forming technologies and prototype development of typical asymmetric open components. By means of finite element analysis （FEA） and simulation,studies have been carried out on the springback and edge wave defects during AHSS roll forming ,and an optimized process design has been achieved. The generation mechanisms of vertical bows ,horizontal cambers, twists,pre-punched hole distortion and cut end flare have been analyzed,and solutions to these defects have been given. In addition,tesing of the roll forming process for AHSS has been conducted and typical samples with required dimensional accuracy have been manufactured. This study has provided technical support for the large-scale application of AHSS.
文摘Improving the galvanizability of high silicon advanced high strength steels （AHSS） is a practical technical challenge. In this study, spot defects on an industrial hot dip galvanized （GI） sheet of an AHSS with 1.5 % Si has been studied in-depth. The surface morphologies of spot defects before and after partial and complete removal of the Zn layer, as well as the interface between the outermost coating layer and the sheet substrate were characterized using optical microscopy （ OM）, scanning electron microscopy （ SEM）, a 3-D optical profiler, energy dispersive spectroscopy（ EDS ） and focused ion beam （FIB） analysis. The most outstanding spot defect on the normally coated area of the steel sheet has a diameter of approximately 500μm, with the following characteristics. In the central region of the spot defect,Zn is barely coated and the sheet substrate is covered by a thin silicon oxide film with dispersed Zn-Fe intermetallics. At the periphery of the spot defect, a burst structure of Zn-Fe intermetallics forms on the sheet substrate. Outside the spot defect where the Zn layer is normally coated, there is a continuous Fe2Al5 inhibition layer between the Zn coating and the sheet substrate. These results indicate that a silicon oxide film forms on the substrate during annealing prior to hot dipping, thus preventing the formation of the Fe2Al5 inhibition layer during hot dipping. This causes spot defects on high Si AHSS sheets.
基金express deep gratitude and sincere appreciation to the National Research Council of Thailand(NRCT under contract number A104/2017 for the financial support of this research
文摘The aim of this research study was to determine optimal resistance spot brazing parameters for joining between AHSS and AISI 304 stainless steel by using filler metal. The key parameters investigated in this study consist of the brazing current, electrode pressure and brazing time. The Taguchi method was applied to the design of experiments. Signal-to-Noise ratio was introduced in the study to identify optimal levels from the process where input parameters yield increased shear strength. Brazing was thus implemented with 5,000A brazing current, 0.70 MPa electrode pressure, and 1.50s brazing time. The maximum shear strength obtained was 54.31 N·mm^-2 in accordance with input parameter settings. In addition, Cu-rich phase and Ag0.4Fe0.6 intermetallic phases were found at the interface zone.
