Fabrication and Characterization of Ni60A Alloy Coating on Copper Pipe by Plasma Cladding with Induction Heating

Plasma cladding coupled induction heating was developed and successfully used to fabricate Ni60A coating on the surface of copper pipe. By matching the swing arc with the rotating copper pipe, the cladding efficiency was as high as 32.72 mm2/s. From the head to the tail of the coating, the wear resistance changed from 4.5 to 1.8 times that of pure copper. During the cladding process with constant current, the surface temperature of the cladding zone and the bath depth gradually increased. The corresponding dilution ratio increased, accompanied by the widening of the interface transition zone and the growth of precipitated phases (CrB and Cr23C6). Due to the gradient change of composition, the coating can be regarded as an in situ synthesized gradient coating. The critical point of sudden change of temperature in cladding zone was 850 °C, at which point the wear mechanism changed from abrasive wear to adhesive wear. The proper surface temperature of cladding zone should be controlled within 600–850 °C, which can be achieved by matching the cladding current and induction heating power. Results indicated that plasma cladding coupled induction heating is a potentially effective method to prepare high-quality coating on the surface of a large-complex-curved copper component.

The Effect of Temperature on the Braking Force Experienced by Magnet Falling Through a Copper Pipe

The braking experienced by a magnet falling through a conductive pipe is often shown in laboratories, as it is highly intriguing and captures the imagination of students. The Eddy current is the physical phenomenon behind Eddy current braking, which has a lot of utility as Eddy current brakes do not utilise friction and hence do not wear. Linear eddy current brakes, often used on rail vehicles, use the rail as a conductor. Consequently, it is important to address the impact of the rail's properties. Previous papers have explored the significance of thickness and material however temperature has yet to be considered. Here, coils were wrung around a copper pipe and an oscilloscope was used to determine the position of a neodymium magnet falling through pipe at various temperatures in order to determine the magnet’s terminal velocity. This data was then used to determine the braking force exerted by the pipe on the magnet. The experimental findings were compared to a theoretical model for the braking force. Graphing the inverse of the dragging constant and temperature showed a positive linear relationship suggesting that increasing the temperature reduces the braking force experienced by the magnet, which is in line with pre-existing theory that increasing the temperature will reduce conductivity, in turn reducing the eddy currents that cause the braking force. Finally, this study establishes that temperature, and hence the weather plays a significant role and needs to be considered when designing eddy current based machines, such as magnetic brakes in high-speed trains.

Pipe Internal Grooving Using Closed Magnetic Field System: A Novel Method

The present work proposes an innovative method to form microgrooves on a tube internal surface through a new machining mechanism based on the principle of magnetic force for a greater flexibility and lower mechanical constraint. A newly designed machine equipped with a Magnetic Grooving Tool (MGT) was designed and fabricated for this purpose. The tool that consists of a pair of magnets is positioned in the pipe to be pulled by another pairing magnets set at the pipe external side. These four magnets are arranged in sequence of N-S-N-S direction so that it creates a closed magnetic field circuit which has a greater pulling force. By controlling the magnet pair at the pipe’s external side in the linear and rotational direction, the MGT is moved in both directions and simultaneously pulled towards the pipe surface to form the microgrooves. Experiment has been carried out by adjusting the internal and external magnets size combination and its distance to vary the magnetic strengths. The effect of magnetic pull force on the grooving dimension was examined by using an optical microscope and further analyzed using a 3D optical surface profile analyzer. The method was proven to capable of producing microgrooves on the internal surface of the copper pipe. The maximum groove depth of 75.55 μm was recorded by using the magnet size 10x10x40 mm and distance between magnet and workpiece of 2.5 mm.

Problems of application of standards in evaluation of microstructure of metals and alloys

The purpose of this work is to consider the problems of applying some standards containing reference scales of structures: 1763-68, 1778-70, 5640-68, 9391-80, 10 243-75, 13938.13-93, 22 838-77, 3443-87 (materials: oxygenated copper, pipe and structural steels, cast iron). It is shown that the normative base of standards for metallographic analysis is morally outdated. The main problem is the discrepancy between the increase in standards and real modern structures. Basically, microstructure standards use a magnification of 100 times, in particular, for the analysis of oxygenated copper, banding of the rolled metal structure, Widmanstätt structure, phosphide eutectic. The analysis of modern materials requires an increase of about 500...800 times. The magnification of 360…400 times, used in some scales, is also insufficient, in particular, for the analysis of structurally free cementite. Also, the quality of images of structures makes them difficult to use. A common disadvantage of the considered standard scales of structures is the absence of metrics in photographs, which does not correspond to the modern level of metallurgy and causes certain inconveniences when comparing structures. It is necessary to revise the standards governing the structure of metals and alloys. Research should be carried out to develop a new generation of standards based on the real structures of modern industrial alloys. It is also necessary to develop new methods of structure analysis. This applies primarily to analysis in image processing programs.

Design and Fabrication of Magnetic Loop Antenna for 5MHz

In the short-wave range, size of the antenna become large and therefore is a major constraint. Magnetic Loop Antenna provides an advantage over other antennas in terms of a smaller size, higher quality factor and better signal to noise ratio. It works on the principle of resonance with the inductor provided by loop and external tuning capacitor operating like a tank circuit. The tunable magnetic loop antenna is designed to work in the high frequency range. The antenna consists of a circular hollow copper pipe, an inductive loop feed and a variable tuning capacitor. The antenna is tuned using variable 9-140pF capacitor paralleled with 150pF capacitor. The designed antenna is simulated using 4NEC2 software. The simulated antenna has high efficiency and quality factor of more than 1000. The real time testing show great result at 5.45MHz with bandwidth of 8KHz.