基于Dynamo和Advance Steel的水轮机蜗壳快速设计方法

蜗壳是水电站中常用的一种异形结构,其设计质量直接影响水电站的发电效率。为提高蜗壳设计效率及解决蜗壳后续加工的难点,综合利用Dynamo for Revit和Advance Steel软件各自的优点,提出了一种适用于水轮机蜗壳的快速设计方法。利用Dynamo的参数化建模功能,结合蜗壳设计公式,实现了蜗壳结构的快速化建模;再选用合理的数据交换格式将模型导入Advance Steel,经过处理后即可生成蜗壳钢结构加工所需要的各类视图及数据驱动文件,可直接用于蜗壳加工。所提出的方法也可推广应用于水利水电工程中类似异形钢结构部件的设计及加工。

Improvement of the microstructural features and mechanical properties of advanced high-strength steel DP590 welds

The effects of the welding current mode in resistance spot welding on the microstructure and mechanical properties of advanced high-strength steel dual-phase 590(DP590)sheets were investigated.Results showed that a rough martensitic structure was formed in the weld zone of the sample welded via the single-pulsed mode,whereas the microstructure in the heat-affected zone consisted of a very rough martensitic microstructure and rough ferrite.However,using the secondary pulse mode led to the formation of tempered martensite in the weld zone.The maximum load and the energy absorption to failure of the samples with the secondary pulsed cycle were higher than those of the samples with the single-pulsed mode.Tensile shear results indicated that the secondary pulsed mode could significantly change the mode of failure upon shear tension testing.Therefore,the obtained results suggest that the use of secondary pulsed mode can improve the microstructural feature and mechanical properties of advanced high-strength steel DP590 welds.

Yield Loci of TRIP590 Advanced High Strength Steel Based on Biaxial Loading Test

The main purpose of the paper is to obtain the experimental yield loci of TRIP590 advanced high strength steel,and to compare it with the theoretical loci in order to obtain the best yield criterion for this material.First,the biaxial loading tests under different loading paths in the method of load control are carried out.Then,the experimental yield loci of different deformation stages are obtained.Finally,the experimental yield loci are compared with the theoretical loci of Mises criterion and Hill48 criterion,the parameters of which are calculated based on the r?value and the yield stress method,respectively.The results show that the accuracy of the theoretical yield loci of Hill48 based on the yield stress is higher than that of Mises criterion and Hill 48 criterion based on r?value method.

Development of a hot-rolled 980 MPa advanced high-strength steel with excellent flangeability and bendability

A new 980 MPa advanced high-strength steel(AHSS) with excellent bendability and flangeability has been studied and industrially produced, typical of tensile strength, fractured elongation, and hole expansion ratio(HER) exceeding 980 MPa, 10%,and 30%,respectively.The 90° V-type bending perpendicular to the rolling direction can satisfy the R/t=1.0 requirement, indicating excellent bendability.Systematic evaluations of industrial trial-produced 980 MPa hot-rolled AHSS have been conducted, including microstructure, tensile properties in three directions, HER,bendability, fatigue limit strength, and forming limit.The microstructure of the newly developed 980 MPa AHSS primarily consists of fine bainite and a small amount of martensite-austenite constituent.The practical yield and tensile strength are higher than 800 and 980 MPa, respectively, with typical elongation of 13% and HER of around 40%.The good combination of the newly developed 980 MPa AHSS is primarily attributed to the fine bainitic microstructure, resulting in excellent flangeability and bendability.In addition, the newly developed 980 MPa AHSS has good fatigue and forming properties, making it suitable for the production of chassis and suspension components.

Recent progress related with ultra-steels at NIMS

Ultra - steel Project performed at National Institute for Materials Science(NIMS) 1997 -2005 proposed 'Breakthroughs for innovation by steel science'.The main concepts were composed of decreasing the environmental load,no or less special alloying elements and safer infrastructure with reduced the total life cost.Four 'double strength and double life' steels were developed as follows:①800 MPa-class ecologically beneficial steels for welded structures,②1 500 MPa steels with high resistance to fracture,③advanced ferritic steels for 650C-USC boilers and④Ultra-steels for structures in marine and offshore environments.World steel society is still growing with threatening limits of resources and energy.Application of the ultra-steel ideas would be increasingly helpful for the global sustainability.The talk will introduce the recent progress in steel research at NIMS,based on the project accomplishments.

Feasibility of 0.02% Nb-Based Microalloyed Steel for the Application of One-Step Quenching and Partitioning Heat Treatment

To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.

Current Challenges and Opportunities Toward Understanding Hydrogen Embrittlement Mechanisms in Advanced High-Strength Steels: A Review

Hydrogen embrittlement(HE)is one of the most dangerous yet most elusive embrittlement problems in metallic materials.Advanced high-strength steels(AHSS)are particularly prone to HE,as evidenced by the serious degradation of their load-bearing capacity with the presence of typically only a few parts-per-million H.This strongly impedes their further development and application and could set an abrupt halt for the weight reduction strategies pursued globally in the automotive industry.It is thus important to understand the HE mechanisms in this material class,in order to develop effective H-resistant strategies.Here,we review the related research in this field,with the purpose to highlight the recent progress,and more importantly,the current challenges toward understanding the fundamental HE mechanisms in modern AHSS.The review starts with a brief introduction of current HE models,followed by an overview of the state-of-the-art micromechanical testing techniques dedicated for HE study.Finally,the reported HE phenomena in different types of AHSS are critically reviewed.Focuses are particularly placed on two representative multiphase steels,i.e.,ferrite–martensite dual-phase steels and ferrite–austenite medium-Mn steels,with the aim to highlight the multiple dimensions of complexity of HE mechanisms in complex AHSS.Based on this,open scientific questions and the critical challenges in this field are discussed to guide future research efforts.

基于模板的钢结构加工图自动标注技术研究

钢结构加工图是钢结构加工厂加工构件的重要依据,目前加工图的标注主要依赖于人工调整,占据当前深化加工工作量的50%以上,自动标注的实现可以提高加工图制图的效率。对基于模板的钢结构加工图自动标注技术进行研究,通过加工图的标注特征分析了自动标注模板的结构。自动标注模板的设计内容包括五个部分:构件类型管理、视图类型管理、标注方向确定、标注点选择、标注线样式管理。通过Advance Steel和Tekla标注插件分析了自动标注模板的应用方法,使用自定义标注模板生成的加工图符合设计要求,无需人工调图。

A comparison study on interfacial properties of fluorine-bearing and fluorine-free mold flux for casting advanced high-strength steels

A comparison study on interfacial properties of a traditional fluorine-bearing(F-bearing)mold flux and a newly designed fluorine-free(F-free)mold flux to produce advanced high-strength steels(AHSSs)by compact strip production technology was conducted.The results showed that these two kinds of mold fluxes gradually spread out on the typical AHSS substrate when slags began to melt with the increase in heating temperature,and they had a good interfacial ability between the two mold fluxes and the AHSS substrate,and there was no other interfacial reaction except the oxidization of steel substrate by the mold fluxes.In comparison,the wettability of the designed F-free mold flux with the AHSS substrate was better than that of the F-bearing mold flux.The reason could be explained as the addition of B_(2)O_(3) would increase the complexity and polymerization degree of the melt structure and weaken the attractive force between the ions and ionic groups,then leading to a better wettability.Besides,B_(2)O_(3) is an effective flux,which can reduce the melting temperature obviously,and the surface tension of the liquid F-free mold flux would get reduced with the addition of B_(2)O_(3).

Mechanism of subsurface microstructural fatigue crack initiation during high and very-high cycle fatigue of advanced bainitic steels

Advanced bainitic steels with the multiphase structure of bainitic ferrite,retained austenite and martensite exhibit distinctive fatigue crack initiation behavior during high cycle fatigue/very high cycle fatigue(HCF/VHCF)regimes.The subsurface microstructural fatigue crack initiation,referred to as“non-inclusion induced crack initiation,NIICI”,is a leading mode of failure of bainitic steels within the HCF/VHCF regimes.In this regard,there is currently a missing gap in the knowledge with respect to the cyclic response of multiphase structure during VHCF failure and the underlying mechanisms of fatigue crack initiation during VHCF.To address this aspect,we have developed a novel approach that explicitly identifies the knowledge gap through an examination of subsurface crack initiation and interaction with the local microstructure.This was accomplished by uniquely combining electron microscopy,three-dimensional confocal microscopy,focused ion beam,and transmission Kikuchi diffraction.Interestingly,the study indicated that there are multiple micro-mechanisms responsible for the NIICI failure of bainitic steels,including two scenarios of transgranular-crack-assisted NIICI and two scenarios of intergranular-crack-assisted NIICI,which resulted in the different distribution of fine grains in the crack initiation area.The fine grains were formed through fragmentation of bainitic ferrite lath caused by localized plastic deformation or via local continuous dynamic recrystallization because of repeated interaction between slip bands and prior austenite grain boundaries.The formation of fine grains assisted the advancement of small cracks.Another important aspect discussed is the role of retained austenite(RA)during cyclic loading,on crack initiation and propagation in terms of the morphology,distribution and stability of RA,which determined the development of localized cyclic plastic deformation in multiphase structure.

Influence of lanthanum on inclusions and as-cast microstructures in a low-alloy high-strength steel

Advanced high-strength steel ingots with total lanthanum(TLa)contents of 0,15×10^(–6),86×10^(–6)and 360×10^(–6)were prepared through laboratory experiments.The modification of inclusions and the variation of the as-cast microstructure with the content of lanthanum in the high-strength steel were analyzed.The result showed that with the increase in the TLa content in the steel from 0 to 360×10^(–6),the modification path of inclusions in the as-cast steel was Al2O_(3)and calcium aluminate→LaAlO_(3)→La_(2)O_(2)S→La_(2)O_(2)S–La2O_(3).The addition of La in the high-strength steel significantly refined the solidification structures.With the increase in the TLa content in the steel from 0 to 360×10^(–6),the ratio of the equiaxed crystal region in the macrostructure increased from 30.1%to 50.7%,the proportion of the high-angle grain boundary in the microstructure increased from 36.9%to 69.8%,and the area fraction of the acicular ferrite and the bainite increased from 0 to 93.3%.Inclusions of LaAlO_(3),La_(2)O_(2)S and La2O_(3)in the La-containing steel could act as heterogeneous nucleation cores ofα-Fe during the solidification.With the increase in the TLa content in the steel,the number density of inclusions that could act as effective heterogeneous nucleation cores in the steel gradually increased,which enlarged the ratio of the equiaxed crystal region and the proportion of intragranular acicular ferrite,and refined the as-cast microstructure of the high-strength steel.

Carbide precipitation behavior and mechanical properties of micro-alloyed medium Mn steel

The carbide precipitation behavior and mechanical properties of advanced high strength steel deformed at different temperatures are investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM) equipped with an energy dispersing spectroscopy(EDS),and tensile tests.The medium Mn steel was subjected to controlled deformation up to 70% at 750℃,850℃,950℃,and 1050℃,and then quenched with water to room temperature,followed by intercritical annealing at 630℃ for 10 min.In comparison with the undeformed and quenched specimen,it can be concluded that acicular cementite precipitates during the quenching and cooling process,while granular NbC is the deformation induced precipitate and grows during the following annealing process.As the deformation temperature increases from 750℃ to 1050℃,the product of strength and elongation increases at first and then decreases.The smallest average size of second phase particles(20 nm) and the best mechanical properties(32.5 GPa%) can be obtained at the deformation temperature of 950℃.