Non-metallic Inclusions in Continuously Cast Aluminum Killed Steels

In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Probe Microanalysis) and by analyzing the total oxygen. The results showed that in the slabs the total oxygen was quite low and the inclusions discovered were mainly small-sized angular alumina inclusions. This indicates that most inclusions have been removed by floating out during the continuous casting process. In addition, the countermeasures were discussed to decrease the alumina inclusions in the slabs further.     

Prediction of Hot Ductility of Low-Carbon Steels Based on BP Network

The purpose of the research is to obtain an effective method to predict the hot ductility of low-carbon steels, which will be a reference to evaluate the crack sensitivity of steels. Several sub-networks modeled from BP network were constructed for different temperature use, and the measured reduction of area (AR) of 12 kinds of low-carbon steels under the temperature of 600 to 1000 ℃ were processed as training samples. The result of software simulation shows that the model established is relatively effective for predicting the hot ductility of steels.     

A Model for Diagnosing the Formation of Internal Cracks in Continuously Cast Slabs

Internalcracksareatypeofdefectfrequentlyoccurringincontinuouslycastslabs,anditisusuallyaccompaniedbyserioussegregationandisharmfultotheuniformityandcontinuityofsteel.Ithasbeenprovedthatinternalcracksarecausedbytheexcessivetensilestrainoriginatingatth...     

High Temperature Ductility Loss of 16MnCr5 Pinion Steels

A wide ductility trough covering from 700 to 1100 is observed in the curve of Reduction of Area (RA) vs.tempetature for 16MnCr5 pinion steel. At 750℃, corresponding to the minimum of RA, it is grain boundary slidingthat controls its hot ductility rather than usual Deforming Induced Ferrite (DIF), which can only appear just below750℃ and slightly improve hot ductility. The volume fraction of ferrite is dependent on the strain and strain rate.Firstly a critical strain must be necessary for formation of DIF then with strain rate increasing, the volume fractionof DIF decreases but RA is elevated. In the γ phase region, hot ductility is seriously deteriorated because of grainboundary sliding promoted by oxidcs and sulfides at the grain boundary and recovered because of dynamic recrystal-lization at higher temperature; when strain rate increases, ductility is improved as there is insufficient time for cracksto propagate along the γ grain boundary as well as dynamically precipitating, and ductility trough becomes narrowerbecause the temperature for onset of dynamic recrystallization decreases. In addition, γ→α phase transformationintroduced by temperature drop before the tensile test encourages precipitation of AlN and impairs ductility.     

对向差压超塑胀形m值的计算公式和测量方法

本文给出在背压作用下超塑自由胀形m_H·m_V·m_P的计算公式和测量方法,为研究双拉一压应力状态以及在此应力状态下不同加载路径对m值的影响提供了必要的研究手段。从ZnAl_4Cu在不同背压下胀形实验结果可见,增大背压,可以显著提高胀形速度。     

横向变形独立发展现象分析

文中对粗砂岩和细砂岩两种岩石单轴受压蠕变试验中，横向变形独立发展现象进行了定性描述与定量分析，并以岩样内部裂隙发生发展为出发点，对该现象机理进行了分折，认为在一定水平的应力下，岩样内部裂隙随时间不断发展，是横向变形独立发展的原因。     

等离子渗氮处理超级钢材的长寿命疲劳性能

采用等离子渗氮技术对两种抗拉强度约为2300MPa和2700MPa的超级钢材进行表面改性处理，再分别利用常规疲劳实验方法和压电超声频率加速实验方法进行长寿命疲劳性能实验研究，并重点讨论了等离子渗氮超级钢材长寿命疲劳性能和内部裂纹萌生机制。两种超级钢材在超过107应力循环后仍然发生破坏。实验结果表明，等离子渗氮可以显著提高麻时效钢的疲劳强度，但却有损于高碳铬轴承钢的疲劳性能。     

Strain in solidifying shell of continuous casting slabs

Two-dimension unsteady heat transfer model was applied to obtain the surface temperature and the shell thickness of continuous casting slabs during the process of solidification. On the basis of which, the mathematical model of strain at the interface of solid and liquid steel was set up. Through which, the strain in the solidifying shell under normal and abnormal operation conditions was gained. The results indicate that the strain is small under the normal operation conditions and the internal crack never happens. However, when the variation of the roll gap is above 2 mm, the strain caused by which is greater than that caused by bulging. Furthermore, the total strain exceeds the critical one and the internal crack is the result. So it is of great importance to maintain the fine state of continuous casting machine to avoid the appearance of internal crack.     

硅通孔电镀填充铜的蠕变性能

为了研究TSV-Cu的蠕变性能,首先利用典型的TSV工艺制作了电镀Cu的TSV试样,然后利用纳米压痕法对TSV-Cu进行了压痕蠕变测试.采用恒加载速率/载荷与恒载荷法相结合的方式,对TSV-Cu的蠕变行为进行了研究,测量了TSV-Cu在不同压入应变速率和最大压入深度条件下的蠕变行为.通过对保载阶段的数据进行处理,得到了不同加载条件下的蠕变速率敏感指数m.结果表明：压入应变速率和最大压入深度等加载条件对m的影响不很明显.     

消失模铸造高铬铸铁板锤工艺的数值模拟优化

应用PROCAST对高铬铸铁板锤的消失模铸造工艺进行数值模拟,充分考虑工艺参数冒口、冷铁和浇注温度,并对模拟结果进行分析,选择最优工艺方案,最后通过生产实践验证了优化结果的准确性。     

应用散斑放大技术确定裂纹尖端应变场

应用激光散斑放大技术对１６Ｍｎ钢三点弯曲裂纹试件进行了测试。提取了裂纹尖端附近１ｍｍ区城内的位移信息，然后应用小变形几何关系换算成应变场。对裂纹扩展规律进行了探讨。实验结果与最大拉应变准则相符。     

CSP工艺Q235 B热轧带钢边部裂纹成因分析

为减少采用CSP工艺生产的Q235B热轧带钢边部裂纹缺陷,分别在Q235 B连铸坯和热轧带钢裂纹处进行取样,通过宏观形貌、金相组织、扫描电镜及能谱分析等方法,研究铸坯角部横裂纹与热轧带钢边部裂纹的演变规律和形态变化. 结果表明,结晶器卷渣、冷却不均匀是产生连铸坯角部裂纹的主要原因;第2道次过渡带钢的金相组织中出现混晶现象,裂纹边上存在脱碳现象;热轧带钢边部裂纹主要源自于铸坯裂纹,并在轧制过程中得到扩展. 根据连铸工艺参数,对边部裂纹缺陷率与液渣层厚度、保护渣消耗量、结晶器振动参数、中间包过热度、结晶器传热参数以及铸坯宽度的关系进行统计分析,并提出相应的边部裂纹控制工艺措施.     

细晶粒高强钢筋混凝土梁受弯性能试验与参数分析

为研究配置了细晶粒高强钢筋混凝土梁的受弯性能,制作了HRBF400、HRBF500级钢筋混凝土矩形截面梁各4根进行静力抗弯试验.研究表明HRBF筋混凝土梁在短期荷载作用下的最大裂缝宽度实测值满足规范要求,但计算值不满足.HRBF400级钢筋混凝土梁在正常使用条件下的挠度能满足规范要求,HRBF500级钢筋混凝土梁不能够满足规范要求.推导了HRBF筋混凝土梁在裂缝/挠度控制条件下的承载力计算公式,提出了构件承载力利用系数的概念,分析了钢筋强度、钢筋直径、混凝土强度、配筋率、混凝土保护层厚度、高跨比对构件承载力利用系数的影响.在经济配筋率范围内,HRBF筋混凝土梁的延性基本满足要求.HRBF筋混凝土梁的耗能能力在较低配筋率时与普通钢筋混凝土梁相近,但随着配筋率的提高,其耗能能力较普通钢筋混凝土梁降低的快.同配筋率下,HRBF筋混凝土梁在弹性阶段的耗能能力较普通钢筋混凝土梁要高,且随着配筋率的增大而提高.     

Influence of Microstructures and Residual Stress on Fatigue Crack Propagation Rate of High Carbon Steels

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温度、应变率和晶粒对Mn18Cr18N钢高温塑性的影响

通过拉伸热模拟试验研究了温度、应变率和晶粒尺寸对Mn18Cr18N高氮奥氏体不锈钢高温塑性的影响。结果表明：在800℃~1 200℃温度范围内,Mn18Cr18N高氮奥氏体不锈钢的塑性随温度升高而升高,1 200℃时达到最好,然后开始下降;应变率通过再结晶的作用而影响塑性;当温度低于1100℃时,细晶粒尺寸材料的塑性优于粗晶粒尺寸,而温度高于1 100℃时中等晶粒尺寸材料塑性最好。     

Creep rate sensitivities of materials by a depth-sensing indentation technique

1. Introduction Under indentation, creep occurs in many kinds of materials at temperatures well below half of their melting points, due to the very high stress beneath the indentation [1-4]. However, the creep strain rate occurring under such conditions i…     

Mechanism of High Temperature Deformation in Cast Ti46Al8.5Nb0.2W Alloy

Compression tests were conducted in the two phase Ti46Al8.5Nb0.2W alloy with a cast microstructure under the strain rates ranging from 2×10-5s-1to 10-2s-1 at temperatures ranging from 900℃ to 1 100℃. It was found that there exist approximately linear relationships between the flow stress and the logarithm of strain rate at different temperatures. The strain rate dependence was analyzed by the thermal activation theory and dislocation climbing is regarded as the controlling mechanism during high temperature compression tests.     

Simulation of thermomechanical behavior during continuous casting process based on MiLE method

A new method called mixed Lagrangian and Eulerian method(MiLE method) was used to simulate the thermomechanical behavior during continuous casting process of steel YF45MnV.The simulation results are basically in agreement with the measured data.The delaying period at the beginning of solidification is about 0.1 in square root of solidification time which is agreement with the data in literatures,and shell thickness increases in linear relation to square root of solidification time.The bloom surface temperature decreases gradually as the casting proceeds.The effective stress in the corner is much larger than that in the mid-face.The corner area is the dangerous zone of cracking.The effects of mold flux break temperature on the air gap and hot tearing indicator were also modeled.The model predicts that the bloom surface temperature increases with the increase of the mold flux break temperature,but the heat flux decreases with the increase of the mold flux break temperature.The hot tearing indicator is much smaller when the mold flux break temperature is higher.     

强电场中LY12CZ合金摩擦焊缝金属变形行为研究

通过测定摩擦焊接过程参数和焊接接头的焊合区及扭转塑变区的测量,推导了电场作用下LY12CZ合金摩擦焊接过程中,初始动态再结晶的热变形条件方程式和准稳定摩擦阶段焊合区金属的塑性流动方程.结果表明随着摩擦界面温度升高、相对旋转速率降低和外加电场强度的增加,产生初始动态再结晶的临界流变应力降低;随着外加电场强度的增大,LY12CZ合金摩擦焊缝金属的应变速率敏感性指数m增大,但在本实验条件下,当电场强度E>522 V/mm时的m值有所降低;LY12CZ合金摩擦焊缝金属发生塑性变形的变形表观激活能随外加电场强度的增大而降低.     

硫化氢腐蚀疲劳环境中高压气瓶临界裂纹尺寸计算

针对当前高压天然气瓶缺乏“检验与评价标准”的现状,按照断裂力学与概率统计理论,从H2S应力腐蚀角度出发,在符合实际工况的中等质量分数的H2S溶液、6．7μHz超低周频率下进行了系列试验,得到了腐蚀疲劳裂纹扩展速率dα／dN-△K的数学表达式．用逆推方法,在综合考虑H2S应力腐蚀下的极限裂纹尺寸、腐蚀疲劳环境中的裂纹扩展量、实验数据的随机性与可靠度、不同检验周期实用性的基础上,定量给出了多种检验周期下气瓶初始最大允许裂纹尺寸,绘制了裂纹评定图,为制定气瓶的检验周期及进行寿命评估提供了实验依据．