含B2O3无氟连铸保护渣物理性能的研究

常规保护渣中配入的助熔剂一般是氟化物和Na2O,但二者都对环境产生严重污染。为此试验研究了含助熔剂B2O3保护渣及其熔点、粘度、结晶性能和表面张力等物理性能。试验表明，当保护渣碱度(CaO/SiO2)等于0．88，成分(％)为37．91CaO-43.09SiO2—5Al2O3—5MgO-2Li2O-7B2O3时的熔点909℃，熔化性温度1160℃，1300℃粘度值0．40Pa．s,1300℃表面张力值0．32N/m，能满足常规钢种和部分特殊钢种对连铸保护渣的使用要求。     

第十四讲:真空工程用焊接技术

(上接2005年第5期第64页) 3.1.3 异种材料的接头形式 在真空系统和真空泵体设计制造中常遇到异种金属的焊接结构,如不锈钢法兰盘与可伐管的连接,不锈钢与铜管的连接等.设计这种结构形式时,要结合不同材料的热膨胀系数、熔化温度、导热率和在深冷条件下的收缩等情况综合予以考虑,才能得到满足真空气密性要求的焊接.其接头形式见表3.     

升温速率对金属熔化和过热的影响

采用分子动力学方法和QSC(Quantum Sutton-Chen)力场研究了升温速率对金属银和金属铅的熔化和过热行为的影响。研究结果表明，升温速率对金属银和铅的熔化和过热行为有很大影响，随着升温速率的升高，金属的熔点有所升高。高的升温速率会导致金属体系内部无序化程度增加，降低了熔化相变的能垒。升温速率导致的银和铅完美晶体的过热极限分别为1450K和800K。     

根据二元合金相图计算脱氧元素的熔化热

根据9幅二元合金相图，分别计算了6种炼钢用脱氧元素Si、Ca、Ba、Mn、La和Al的熔化热。根据二元合金相图计算脱氧元素的熔化热的方法，对确定出钢温度和钢水脱氧过程的热力学分析及计算有一定的实际意义。     

GMAW焊接熔滴过渡模型的研究进展

对实芯焊丝GMAW焊接熔滴过渡数值模型的研究进展进行综述,认为主要熔滴过渡模拟理论为SFBT、PIT和VOF理论。通过对SFBT、PIT、VOF三种理论的比较,认为VOF理论在处理复杂的自由边界形态时比其他方法更适合和更有效,与实验结果更吻合。为提高理论计算与实验结果的一致性,指出VOF理论还需考虑金属蒸发产生的蒸气压力等因素的影响。     

一种基于PPCNN的金属激光熔化沉积熔池状态识别方法

金属激光熔化沉积质量与熔池状态具有密切的关联,根据熔池视觉特征对加工中的熔池状态进行识别,进而实现沉积质量的在线预测对金属激光熔化沉积技术具有重要意义。为构建上述映射关系,本文提出了一种基于金字塔池化卷积神经网络的金属激光熔化沉积熔池状态识别方法。针对所采集的熔池同轴图像,建立用于训练和测试的数据集;构建了金字塔池化卷积神经网络(Pyramid pooling convolutional neural networks,PPCNN),并进行网络关键参数的研究。结果表明:第一层卷积核尺寸为5×5,卷积层和金字塔池化模块含有64+8×3个卷积核使网络在识别准确率上达到最佳。所提方法取得了最高96.80%的识别准确率。     

危机滋生地

《国语·周语下》有曰：众口铄金。说的是舆论的力量大得可以将金属熔化。可见舆论的力量之强悍，早在古代中国便知其利害。     

Softening and Melting Behavior of Mixed Burden for Oxygen Blast Furnace

 The behaviors of mixed burden in the cohesive zone of oxygen blast furnace were studied by softening and melting tests, and the influence of reducing gas and burden basicity on the softening and melting behaviors of mixed burden was also investigated. The results indicated that the softening range became wide, however, the melting range narrowed sharply in the atmosphere of oxygen blast furnace. The permeability of burden in the oxygen blast furnace was obviously improved comparing with the conventional blast furnace. In addition, the content of sulphur in the dripping iron of oxygen blast furnace was much lower than that of conventional blast furnace, however, the content of carbon increased. An optimum basicity of burden, which could lead to the appearance of the narrower melting range and better permeability of burden, was obtained in the atmosphere of oxygen blast furnace.     

真空自耗炉熔化过程有新研究

本报讯近日，法国学者研究了真空自耗炉工艺中自耗电极的熔化行为和整体电弧运动对熔化行为的影响。     

Modeling,Simulation and Control of Pulsed DE-GMA Welding Process for Joining of Aluminum to Steel

Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,they can not precisely control the heat input to work-piece,they are high costs,low efficiency and consist lots of complex welding devices,and the generated intermetallic compound layer in weld bead interface is thicker.A novel pulsed double electrode gas metal arc welding（Pulsed DE-GMAW）method is developed.To achieve a stable welding process for joining of aluminum to steel,a mathematical model of coupled arc is established,and a new control scheme that uses the average feedback arc voltage of main loop to adjust the wire feed speed to control coupled arc length is proposed and developed.Then,the impulse control simulation of coupled arc length,wire feed speed and wire extension is conducted to demonstrate the mathematical model and predict the stability of welding process by changing the distance of contact tip to work-piece（CTWD）.To prove the proposed PSO based PID control scheme’s feasibility,the rapid prototyping experimental system is setup and the bead-on-plate control experiments are conducted to join aluminum to steel.The impulse control simulation shows that the established model can accurately represent the variation of coupled arc length,wire feed speed and the average main arc voltage when the welding process is disturbed,and the developed controller has a faster response and adjustment,only runs about 0.1 s.The captured electric signals show the main arc voltage gradually closes to the supposed arc voltage by adjusting the wire feed speed in 0.8 s.The obtained typical current waveform demonstrates that the main current can be reduced by controlling the bypass current under maintaining a relative large total current.The control experiment proves the accuracy of proposed model and feasibility of new control scheme further.The beautiful and smooth weld beads are also obtained by t