中间包等离子加热可以弥补浇注过程中的钢液温降,改善连铸坯的质量,但加热区温度高对覆盖剂会产生一系列影响.通过X射线衍射(XRD)、光镜及扫描电镜等手段对工业现场中间包使用等离子加热前后的覆盖剂样品进行了对比分析,并采用FactSage热力学软件绘制加热前后覆盖剂的液相线投影图.结果表明,等离子加热前后的中间包覆盖剂形貌发生了明显变化,具体表现为加热前样品疏松多孔,加热后样品结晶率低,呈致密的玻璃状,表面较为均质;通过XRD对等离子加热前后的覆盖剂进行物相鉴别,加热后的覆盖剂由晶态变为非晶态,呈现一定的规律性;在光镜下观察样品可发现等离子加热后的覆盖剂样品较加热前更均匀,扫描电镜下进行观察与物相分析发现,等离子加热前覆盖剂样品主要为单一的均质化组成,加热后的样品有灰黑色不溶于基底的氧化物;加热前后覆盖剂的低熔点区域面积变化不大.

Based on the analysis of single-bar melting experiments in a previous article,' I the effect of spacing between the steel bars on the agglomeration of steel shells around the steel bars and the melting rate of steel scrap samples was studied in this article. In addition, a calculation model of melting time of steel scrap in the electric arc furnace under different bulk densities and random stacking conditions was also established. The two-bar melting experimental results show that the thermal simulation results are basically consistent with the numerical simulation results. And an increase in the spacing between the steel bars up to 6 mm and the preheating temperature of the steel scrap samples up to 1 073 K, can greatly reduce or eliminate the adverse effect of the agglomeration of steel shells around the steel bars on the melting process, thus greatly reducing the melting time. The multibar melting experimental results show that an increase in the porosity is beneficial to the melting of steel scrap samples, and when the porosity reached 0.84 and above, the melting time of multibar samples is close to that of an individual steel bar. In addition, the calculation model can accurately predict the melting time of the steel scrap in the electric arc furnace.

Steel products have experienced long-standing problems such as unstable product quality and low product homogeneity. In the continuous casting process, realizing constant-temperature pouring is an effective way to improve product homogeneity. Plasma heating can compensate for the temperature drop during casting with a tundish and maintain a stable degree of superheating of the molten steel in the tundish. Plasma heating has a certain impact on the cleanliness of the molten steel and on the tundish covering flux in the tundish while compensating for the temperature drop. This paper uses SEM-EDS, XRD and FactSage to analyze the cleanliness of molten steel and the characteristics of the tundish covering flux before and after plasma heating. The results show that the number density of inclusions in the tundish is significantly lower after heating, improving the floating removal of small-sized inclusions; after heating, the surface morphology of the tundish covering flux sample appears transparent and glassy, with uniform morphology. XRD results show that the tundish covering flux after plasma heating exhibits no crystal precipitation and is amorphous and that there is a certain regularity before and after heating; there are no obvious changes in the composition of the tundish covering flux in the liquid phase area.

以典型热挤压凸模服役工况为切入点,通过有限元数值模拟获取模具危险部位的加载历程,采用Neuber算法对其进行修正,获得归一化处理之后的载荷谱作为疲劳分析的加载曲线;基于Manson-Coffin模型,实验获取模具材料在服役温度下的拉伸性能,得出材料的应变-寿命曲线,建立基于应变损伤的模具疲劳失效预测模型.针对铝合金挤压件特定工况,进行模具在球化退火+ 1020℃油淬+580℃×2h两次回火处理后的疲劳寿命预测,并对模型进行验证.结果 表明:所建模型预测寿命为1318次,实际寿命为1120次,模具失效部位、服役寿命与预测结果吻合良好.

针对6082铝合金多筋反挤压制件结构复杂、变形不均匀和局部变形程度较大的特点,提出了直接反挤压成形和两工序成形方案(先成形外筋板,再成形内腔).基于MSC.MARC对两种不同的成形方案进行了有限元仿真分析,分别得到了挤压时的应力应变状态、载荷-行程曲线以及金属填充模具的情况.结果表明:采用反挤压一次成形时,筋板成形较困难,难以得到合格的产品;采用两工序成形方案得到的制件外形饱满,无明显缺陷,且材料利用率较高,成形过程中制件的最大等效应力为63MPa,凸模最大载荷为308 kN.根据模拟结果确定了两工序成形方案,设计了工装模具并成功生产出合格零件,为该类多筋制件的生产提供了参考.

在Gleeble-1500D热模拟试验机上对O态6082铝合金进行了热压缩实验,研究了该合金在变形温度300 ～ 500℃,应变速率0.01 ～10 s-1条件下的热变形行为和组织演化;基于Arrhenius双曲正弦本构关系建立了6082铝合金的本构方程;基于动态材料模型(DDM)和Murty法建立了热加工图,并结合微观组织进行验证.研究结果表明:6082铝合金为正应变速率敏感材料,峰值应力随温度的降低和应变速率的升高而升高,热变形过程中的主要软化机制为动态回复,在较高温较低应变速率(500℃,0.1s-1)时,该合金发生动态再结晶.计算得到该合金的热激活能为171.1539 kJ·mol-1,最佳热加工工艺参数区间为:450 ～ 500℃,0.2～0.5 s-1.

目的 研究Cu-Al2O3(0.68%)弥散强化铜合金高温圧缩塑性变形特性.方法 在Gleeble-1500D热模拟试验机上,在变形温度为550,650,750,850,950℃,应变速率为0.01,0.1,1,5,10 s?1,变形量均为50%的条件下,对Cu-Al2O3(0.68%)铜合金进行热压缩变形试验.结果 获得了不同热变形条件下的真应力应变曲线,建立了基于双曲正弦本构关系Arrhenius流动应力模型的本构方程,及基于动态材料模型(DMM)的热加工图.结论 Cu-Al2O3(0.68%)弥散强化铜合金高温压缩时,合金的热变形存在应变强化和稳态流变2个基本阶段,主要软化机制为动态再结晶.该合金的最佳变形区域温度为900~950℃,应变速率为0.2~2.8 s?1.

In view of the characterization of internal crack in materials service process, industrial computed tomography technology was used to scan the samples with internal cracks, and obtain the three-dimensional orientation gray slice images of the cracks.The threshold, area and propagation path were quantitatively characterized and fitted by MATLAB+ImageJ software technology.The results show that the crack area distribution realized as a symmetrical trend, using quartic polynomial can better fit the curve.The crack volume calculated by accumulative method is 76.83 mm3, and the fitting calculation error is 0.48%.The absolute value of the area difference between adjacent slice cracks is less than 5 accounts for 59.26%, which means that the crack area in this interval changes uniformly.In the front view, the expansion trend of the two sides of the crack path is different, the path A and path B are fitted by Gauss function and Logistic function, respectively, the R2 is 0.9928 and 0.9968, showing a good fitting effect.The difference value of two crack paths has three peaks, dividing the scatter diagram into three stages, and difference of the second stage increases linearly.

For the fracture failure of 5CrMnMo hot extrusion die,the service circumstance,macroscopical morphology and microstructures were studied by analyzing the die structure and working conditions combining metallographic,scanning electronic microscope (SEM),hardness testing and so on.The results show that the main reason for the die failure is the local stress concentration due to the structure and mechanical characteristics of the die.The ragged die surface and microstructural factors including large-size carbides in the die steel and serious banding segregation contribute to the die failure.The cracks source is formed on the ragged die surface due to wear and the impact toughness is reduced due to large-size carbides and the banding segregation,which result in rapid propagation of cracks under great stress concentration and then lead to the die's intergranular brittle fracture.

Receiver and output display of GPS information based on the STC89C52 MCU are introduced indetail.Using GPS module as satellite reception,through a serial port conversion,can not only by MCU processing,displaying relevant information in TFT,but also can communicate with the PC,through PC application software,displaying GPS output data.The actual application result indicates that the design is rational and effective with high practical value.

In this paper,based on measurement of GPS model,the method of the error theory and data processing is used for data processing.The veracity of the data is judged by the Lingtu map,processed data is converted to actual mileage,and the actual mileage error and its causes are presented.The results show that the analysis is correct and the data model is reliable.The study accumulates experience for future research work on GPS receiver.