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
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
为了探究电脉冲处理对以马氏体为基体的第三代先进高强度钢(Advanced High Strength Steels,AHSS)显微组织及力学性能的影响,本文采用低碳热轧钢板作为原材料。经过奥氏体化并水淬后,进行不同电流密度的电脉冲处理。通过万能电子试验机...为了探究电脉冲处理对以马氏体为基体的第三代先进高强度钢(Advanced High Strength Steels,AHSS)显微组织及力学性能的影响,本文采用低碳热轧钢板作为原材料。经过奥氏体化并水淬后,进行不同电流密度的电脉冲处理。通过万能电子试验机测试力学性能,通过扫描电镜和透射电镜表征试样微观组织。结果表明,电流密度为12.03 A/mm^(2)时,出现共格相,抗拉强度达1464MPa;电流密度为19.52 A/mm^(2)时,晶界处析出ε-碳化物,晶内析出M6C型碳化物,抗拉强度达1402MPa,延伸率提升至12.6%;电流密度为27.76A/mm~2时,马氏体分解并发生回复再结晶,抗拉强度降低至924 MPa,出现屈服平台,延伸率达15.5%。可见电脉冲处理能有效促进原子扩散和碳化物脱溶沉淀,其热效应与非热效应的耦合影响,使位错缠结和塞积群重新开动,延缓晶界在应力作用下发生弯曲,从而改善塑性。展开更多
基于目前汽车产业的轻量化需求,先进高强钢板被广泛应用在汽车板中。为了保护高强钢板的表面不被腐蚀,其表面需要采用热镀锌或锌层合金化等表面处理技术,利用锌的阳极保护对钢板进行保护。但是由于锌的熔点为440-460°C,因此对高强...基于目前汽车产业的轻量化需求,先进高强钢板被广泛应用在汽车板中。为了保护高强钢板的表面不被腐蚀,其表面需要采用热镀锌或锌层合金化等表面处理技术,利用锌的阳极保护对钢板进行保护。但是由于锌的熔点为440-460°C,因此对高强钢板进行电阻点焊时,会发生液态金属致脆(Liquid Metal Embrittlement, LME)现象。此现象主要是由于锌或锌的金属间化合物在点焊过程中发生局部熔化,进而在点焊过程中的复杂应力场的作用下,沿着晶界扩展,进而导致晶界出现沿晶微裂纹的现象。本文提出采用高温三点弯的实验模拟方法,近似模拟出了Zn及Zn合金在高温复杂应力下沿着晶界浸润的液态金属致脆现象。展开更多
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.
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.
文摘基于目前汽车产业的轻量化需求,先进高强钢板被广泛应用在汽车板中。为了保护高强钢板的表面不被腐蚀,其表面需要采用热镀锌或锌层合金化等表面处理技术,利用锌的阳极保护对钢板进行保护。但是由于锌的熔点为440-460°C,因此对高强钢板进行电阻点焊时,会发生液态金属致脆(Liquid Metal Embrittlement, LME)现象。此现象主要是由于锌或锌的金属间化合物在点焊过程中发生局部熔化,进而在点焊过程中的复杂应力场的作用下,沿着晶界扩展,进而导致晶界出现沿晶微裂纹的现象。本文提出采用高温三点弯的实验模拟方法,近似模拟出了Zn及Zn合金在高温复杂应力下沿着晶界浸润的液态金属致脆现象。
