氧一乙炔喷焊技术在挤出机螺杆上的应用

介绍了氧一乙炔喷焊技术的工艺和应用,以挤出机螺杆表面喷焊为例,叙述了喷焊技术对合金粉末的要求,合金粉末的选择原则,喷焊基体的预热及表面处理,喷焊工作原理及工艺,喷焊层缺陷的分析等。     

喷焊技术在流化床锅炉上的应用

分析了沸腾流化床锅炉存在的主要问题及原因 ,通过采用喷焊技术对锅炉沸腾层埋管进行喷焊处理 ,大大延长了锅炉的运行周期 ,降低了生产成本 ,增加了经济效益。     

Melting mechanism in single screw extrusion

Flow visualization experiments of polycarbonate and polystyrene resin extrusion were performed to observe the melting mechanism and the flow kinematics around the solid-bed in the melting zone of a single screw extruder. The axial solids content and pressure profile calculations of the Tadmor melting model were modified as a result of variable solid-bed velocity and solid-bed temperature observations.     

钨极氩弧焊在不锈钢薄皮管焊接中的应用

不锈钢薄皮管主要运用在食品、医药行业中。对于一般介质的管道焊接采用手工电弧焊焊接,使用之前进行压力试验,保证焊缝不漏即达到要求。对于不锈钢薄皮管的焊接则是采用手工钨极氩弧焊的方法进行,对这种特殊介质且管壁薄、直径小的管道,焊接要求是焊缝内部没有任何缺陷,施工难度也很大。本文分析了不锈钢薄皮管在现场组焊过程中的技术特点和质量控制要点,提出了相应的对策及检测方法。     

实芯焊丝半自动MIG焊在不锈钢管道焊接中的应用

在对347H型不锈钢的焊接性充分了解的基础上,通过对347H型不锈钢使用不锈钢实芯焊丝进行半自动MIG焊接试验,确定了不锈钢实芯焊丝半自动MIG焊焊接347H型不锈钢使用的焊接工艺,为不锈钢管道焊接提供了高效率的焊接方法.     

Total applied shear in capillary extrusion

Viscoelastic properties of polymer fluids are single-valued functions of shear stress or shear rate only at high total applied shear. These parameters may vary with applied shear under milder shear histories. The mean total shear in capillary extrusion is shown to be a function of orifice geometry. Apparent flow curves can be measured at various total shear values by changing the length/radius ratio of the capillary. The true shear stress and true shear rate at the orifice wall correspond to infinite total shear conditions. The true flow curve and elastic parameters like die swell are not measured at equivalent total shear unless the capillary is extremely long.     

Fluorescence monitoring of twin screw extrusion

An optical fiber probe has been constructed in order to obtain real-time measurements of fluorescence radiation during twin screw mixing and extrusion of plasticized polybutadiene and calcium carbonate particulate. The probe consists of an optical fiber bundle which was inserted along the axis of a half-inch sensor bolt, and it was used to transmit optical excitation energy to the processed material and to detect the subsequent fluorescence. The source of fluorescence radiation was a fluorescent dye which was doped into the processed ingredients at very low concentrations. Although most of our measurements were taken with the probe positioned close to the exit die, the sensor bolt can be placed in any instrumentation port along the extruder line. Experiments were carried out to measure residence time distribution, quality-of-mix, and mix concentrations as a function of processing conditions. Product mix changes in response to variations in material feed rates and screw RPM were also observed. Values of residence time were obtained by measuring the transit times for the dye to travel from an upstream injection port to the measurement probe, a distance of 63 cm. Flow instabilities, such as mat formation of the solids, were observed by noting the abrupt changes and discontinuities in the fluorescence signal.     

焦碳塔不锈钢复合板的焊接技术

介绍了15CrMoR 410S不锈复合钢板的焊接工艺技术。在分析研究的基础上,通过采取合理的焊接工艺,保证了复合钢板的力学性能及耐蚀性能。     

The effect of screw geometry on melt temperature profile in single screw extrusion

Experimental observations of melt temperature profiles and melting performance of extruder screws are reported. A novel temperature sensor consisting of a grid of thermocouple junctions was used to take multiple temperature readings in real time across melt flow in a single screw extruder. Melt pressure in the die and power consumption were also monitored. Three extruder screws at a range of screw speeds were examined for a commercial grade of low density polyethylene. Results showed melt temperature fields at low throughputs to be relatively independent of screw geometry with a flat‐shaped temperature profile dominated by conduction. At high throughputs, melting performance and measured temperature fields were highly dependent upon screw geometry. A barrier‐flighted screw with Maddock mixer achieved significantly better melting than single flighted screws. Low temperature “shoulder” regions were observed in the temperature profiles of single‐flighted screws at high throughput, due to late melting of the solid bed. Stability of the melt flow was also dependent upon screw geometry and the barrier‐flighted screw achieving flow with lower variation in melt pressure and temperature. Dimensionless numbers were used to analyze the relative importance of conduction, convection, and viscous shear to the state of the melt at a range of extrusion conditions. Polym. Eng. Sci. 46:1706–1714, 2006. © 2006 Society of Plastics Engineers     

Melting performance in the single screw extrusion of thermoplastics

Melting performance experiments involving three different thermoplastics and three different screw designs have been carried out on a well-instrumented single screw extruder equipped for cold screw extractions. In the case of the particular polystyrene used it was possible to deduce, from measurements made on the extracted screw, the velocity, and hence acceleration, of the solid bed of compacted polymer at points along the screw channel. The experimental results are successfully compared with the performance predicted by a previously established model, the most important feature of which is the ability to allow the solid bed to deform freely and hence to accelerate. The results show that the bed does indeed suffer significant and non-uniform acceleration and that the model can predict both this acceleration and the resulting bed break-up which leads to surging.     

An analysis of the extrusion welding process

A mathematical model has been developed for the heating phase of extrusion welding. It is shown that weld quality is mainly determined by melting a layer of the base material. All the parameters relevant to the heating phase are shown to affect weld quality through their effect on the thickness of the molten layer in the base material. It is shown that these parameters can be well controlled.