油气润滑参数对高速电主轴热特性影响的试验研究

为研究油气润滑参数对高速电主轴热特性的影响,在考虑气流压力和供油量2个因素下对高速电主轴进行热特性正交试验。结果表明:供油量对温升指标的影响最大,气流压力影响次之,二者的交互因素对温升指标的影响比较小。获得了最佳水平组合,得到了不同水平组合下电主轴各方向的热变形;分析电主轴各方向热变形不同的原因,得到在实际加工中应该重点控制主轴Z方向热变形量的结论。     

高速主轴温升影响因素实验研究

温升是影响电主轴工作性能的一个重要指标,为了研究水冷系统和油气润滑系统各参数对高速电主轴温升的综合影响,找出最佳工况参数。采用单一因素实验法和正交实验法,利用水冷系统和油气润滑系统实验平台,对不同转速下,不同工况对主轴轴承某点温升的影响进行实验分析。结果表明,冷却水流量为0.35m~3/h~0.38m~3/h,冷却水温度为17℃,空气压力为0.36MPa~0.39MPa,供油间隔为1min~2min时主轴温升最小。     

电主轴主轴支撑形式及轴承材质研究

对高速电主轴主轴支撑方案进行分析,提出在高转速、大负荷工况下,水润滑动静压滑动轴承是一种可行的主轴支撑解决方案;并从提高主轴刚度、阻尼和回转精度等角度出发,选择了两种可用于水润滑的轴承的匹配材质,为电主轴主轴支撑设计提供参考.     

高速数控车床主轴变工况温升特性研究

为了定量评价和分析高速数控车床在不同运行工况下的主轴温升特性,以某高速数控车床主轴系统为研究对象,在分析主轴系统热源基础上,考虑实际工况参数对主轴系统温升影响,设计了空转条件和切削条件下的工况参数表,利用正交实验法对各工况参数进行组合,然后运用ANSYS Workbench15.0进行热稳态分析,得到不同工况下主轴系统的温度场分布情况;在此基础上,采用了多元线性回归的方法建立变工况参数与车床主轴系统达到热平衡时最高温升的预测模型,并对模型进行了验证,结果表明主轴系统温度真实值与预测值的误差在0℃~2.5℃范围内,所以预测模型具有很高的预测精度。此模型为车床主轴系统温升特性评估、工程实践中工艺参数的合理确定和热误差补偿提供依据。     

高速电主轴热误差实验与预测建模

数控加工中心采用高速电主轴,由于电主轴发热导致主轴工作端明显热延伸,严重影响加工精度。以数控精雕机用永磁同步电主轴为研究对象,通过建立热特性实验平台,测试电主轴在不同转速、不同工作条件下的特征温度和热误差数据,建立基于自然指数函数的电主轴轴向热误差预测模型。在不同的工况下对模型的补偿结果进行实验验证,验证结果表明:该预测模型简单、精度较高,且建模成本较低,可以快速应用到实际的加工环境中。     

高速电主轴冷却系统试验研究

针对高速电主轴实际运行中主轴内部发热量大、温度升高等导致主轴热变形而影响电主轴加工精度问题,以某型电主轴为研究对象,通过仿真与试验结合的方法探究冷却系统冷却能力。阐述电主轴热态特性;分析螺旋和循环冷却系统的有限元仿真结果;进行冷却系统对比试验,验证仿真结果。结果表明:螺旋冷却系统稳态下整体冷却效果和冷却速率都优于循环冷却系统。研究结果为电主轴设计、优化与开发提供了一定的技术参考。     

基于流固耦合的高速电主轴冷却系统分析北大核心

针对机床高速电主轴在高速运转中的冷却问题,以某型号卧式加工中心高速电主轴为研究对象,基于流固耦合法,对串并联、单螺旋及双螺旋三种冷却流道结构从流速、压力、温升三方面进行详细对比。另外,为了进一步优化提升流道对电主轴的冷却效率,通过理论计算分析流道内不同初始流速对主轴热平衡后温升影响,以及不同流道几何参数对换热能力和压力损失的影响,并运用Fluent分别对以上两种提升流道冷却效率的影响因素进行仿真分析。研究结果表明,双螺旋结构因其结构的独特性综合对比为最佳冷却结构;主轴散热随流道内初速流速的增加呈现先急后缓,可通过对比选取最佳冷却流速;流道几何参数对换热能力影响较小,但对压损影响较大,提出了综合考虑换热与压损的流道几何参数设计。研究结果为精密高速电主轴在冷却系统的设计提供了一定理论依据。     

冷却润滑参数对电磁自平衡电主轴温升影响的研究

高速电主轴高度紧凑的结构使其在服役过程中散热困难,常采用油雾润滑和循环水冷方式强制降温。以一种新型电磁自平衡电主轴为对象,研究了异步电动机、滚动轴承和电磁平衡头生热原理;分析了主轴系统传热机制;采用有限元热分析对170MD12Y16-EMAB45电磁自平衡电主轴进行了稳态温度场分析,研究了冷却液流量、压缩空气流量对电主轴最大温升的影响规律。结果表明:电磁平衡头对电主轴温升影响总体很小,电磁自平衡电主轴具有良好热特性;获得了最佳温控参数,为这种电主轴的优化设计和工程应用奠定了基础。     

小模数滚齿机用电主轴的设计与研究

小模数数控滚齿机去掉了传动用的齿轮副、蜗轮蜗杆副等传动元件,刀具轴和工件轴直接与电机轴相联。几何误差和热误差是小模数滚齿机的主要误差来源,为此,设计了一种新型的电主轴。该电主轴采用了主轴电机置于主轴后轴承之后的形式,缩小了主轴轴承位置的径向尺寸,使轴承摩擦产生的热量的散发,减少了电机发热对轴承变形产生的影响;主轴轴承采用了静压轴承的形式,提高了主轴轴承的耐磨性和回转精度。该电主轴的设计能够提高小模数滚齿机的生产效率和加工精度。     

高速机床电主轴过盈配合量的计算

电主轴是高速机床的核心部件,电机转子与机床主轴间过盈配合量的大小是影响主轴性能的重要因素。本文根据材料力学和弹性力学理论,对电主轴的配合特性进行了分析,分别推导出电主轴在静态和高速运转条件下,主轴过盈量和应力分布的理论公式。最后,根据理论公式计算出ＧＤ－Ⅱ型电主轴的过盈配合量,研究结果表明,采用理论公式设计的过盈配合能较好地满足高速电主轴的需要。     

RHEOLOGY FEATURE OF SIMPLE METAL MELT

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

LASER CLADDED TiCN COATINGS ON THE SURFACE OF TITANIUM

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Microstructure and Mechanical Properties of X80 Pipeline Steel Joints by Friction Stir Welding Under Various Cooling Conditions

X80 pipeline steel plates were friction stir welded(FSW) under air, water, liquid CO_2 + water, and liquid CO_2 cooling conditions, producing defect-free welds. The microstructural evolution and mechanical properties of these FSW joints were studied. Coarse granular bainite was observed in the nugget zone(NZ) under air cooling, and lath bainite and lath martensite increased signifi cantly as the cooling medium temperature reduced. In particular, under the liquid CO_2 cooling condition, a dual phase structure of lath martensite and fi ne ferrite appeared in the NZ. Compared to the case under air cooling, a strong shear texture was identifi ed in the NZs under other rapid cooling conditions, because the partial deformation at elevated temperature was retained through higher cooling rates. Under liquid CO_2 cooling, the highest transverse tensile strength and elongation of the joint reached 92% and 82% of those of the basal metal(BM), respectively, due to the weak tempering softening. A maximum impact energy of up to 93% of that of the BM was obtained in the NZ under liquid CO_2 cooling, which was attributed to the operation of the dual phase of lath martensite and fi ne ferrite.     

INDUSTRY NEWS

China Securities News reported on March 21, 2014： Guangdong Hongtu Wuhan Die Casting Co., Ltd. （Wuhan Hongtu）, a wholly owned subsidiary of Guangdong Hongtu Technology （Holdings） Co., Ltd., held a groundbreaking ceremony recently. With the registered capital of 50 million Yuan, Wuhan Hongtu has a total land area of 100,000 square meters and a plant construction area of 72,000 square meters. It is expected to have a production capacity of about 30,000 tonnes of aluminum castings annually after it is put into production.     

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.     

GROWTH MORPHOLOGIES OF A BINARY ALLOY WITH LOW ANISOTROPY IN DIRECTIONAL SOLIDIFICATION

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.