Key Engineering Materials Vol. 522

Abstract: The fluid magnetic abrasive (FMA) is a new type of intelligent material. The fluid magnetic abrasive (FMA) has typical liquid characteristics, when there is no external magnetic field around it. But when a strong magnetic field is applied, the viscosity of it will increase more than 100 times within a few milliseconds, and it will show the characteristics those are resemble to solid's. We call this feature as rheological property, of which because the workpiece can be finished by fluid magnetic abrasive (FMA). On base of researching on the micro-structure of fluid magnetic abrasive (FMA), the experiments and results are presented in this paper.

Abstract: Aiming at the problem that current vacuum casting method lack of the filling ability in filling large & thin-wall castings. Therefore, a regulated pressure vacuum casting method is proposed, which using regulated pressure to improve the filling ability. The process and mechanism for regulated pressure vacuum casting method is presented and proved it through the home-made V450N-VD vacuum casting prototype. The results show that the regulated pressure vacuum casting method has higher filling capacity and can provide higher negative pressure during the whole filling process. So regulated pressure vacuum casting method has profound development potential.

Abstract: The Q235 steel was modified by hot-dip-aluminizing technique, and Al-Mn alloy layer was obtained on the steel surface. Scan electron microscopy (SEM), X-ray diffraction (XRD) and abrasive wear tester were used to investigate the microstructure and wear performance of the Al-Mn alloy coatings. The results show that the surface of the obtained pure aluminum coatings is acicular, while blocks Al-Mn compounds phase exists in Al-Mn alloys layer, and the Al-Mn alloy layer is composed of Al, FeAl₃, Fe₂Al₅ and MnAl₆ phases. The experimental results showed that wear weight loss of aluminum coating is more than Q235 steel. However, after manganese added to the aluminum, Al-Mn alloy coating abrasion wear loss of weight far below the Q235 steel and aluminum coating. And weight loss increases along with Mn content decreases. When worn after 100 h, Al-13% wtMn wear alloy coating weight loss of 45% of Q235 steel, aluminum coating of 35%. So the hot-dipping Al-Mn alloy layer has excellent abrasive wear resistance.

Abstract: Electrical discharge machining (EDM) processing is generally applied on the area of molding plastic component or mating surface required high accuracy. The areas determine the quality of the plastic components. The principle of EDM is based on the material vaporization of high potential difference across the workpiece and Tool electrode. Tool electrode and workpieces are discontiguous when the EDM processes. Because there is no mechanical contact, Hardness and strength of the workpiece material have minimal effect on the material removal rate .The application of EDM technology on injection mold of automotive connector is focused on in this paper. Processing of the complex cores is researched. The design and processing of the tool electrode have been completed in the meantime.

Abstract: According to the fact that the common machining medium used in magnetic abrasive finishing (magnetic abrasive) possessed disadvantages such as high preparation cost, easier to disperse in finishing process, and low utilization and repeat -utilization, this paper puts forward spherical magnetic abrasive of a certain size as magnetic abrasive machining medium, discusses the preparation techniques, establishes the mathematical model of finishing, and analyses the main performance parameter influencing finishing quality and finishing efficiency. Compared with magnetic grinding, spherical magnetic abrasive is not easy to disperse, can be re-used, having long service life and high finishing efficiency and quality. It is a magnetic finishing medium hasing development research value.

Abstract: In processing of structure ceramics materials with diamond grinding wheel, grinding heat is one of vital factors influencing workpiece surface quality. Grinding parameters have important influences on workpiece surface temperature distribution. Contrast experiments on grinding temperature field of ZrO2 in common and ultrasonic grinding were carried out in the paper by manual thermocouple method. The relationship between grinding parameters and temperature were researched theoretically and experimentally. The results show that the farther the distance from grinding surface, the smaller the peak value of temperature is. With the increases of grinding depth, grinding speed and feedrate, the surface temperature will heightens accordingly. It was proved that grinding depth is the most vital factor influencing grinding temperature field through orthogonal experiments. Furthermore, comparing with high surface layer temperature which often results in grinding burn in traditional grinding, ultrasonic grinding can reduce grinding temperature effectively.

Abstract: The heated spiral bevel gear can improve service life and performance. However, the heated spiral bevel gear must be machined by the finish machining process, as result of deformation of tooth surface, which obtained lower machining accuracy. Due to the tooth surface particularity of spiral bevel gears, the traditional tooth grinding, lapping improve the processing quality of tooth surface was subject to a certain degree of influence. Therefore, some measures, such as flared cup grinding, waguri grinding and ultrasonic grinding, which not only improve processing quality of tooth surface of spiral bevel gear, but also improve mill efficiency. With the development of end processing technology at the same time, the cutting tool material and cutting methods appeared certain advantages and received attention in improving fine milling of hard tooth surface.

Abstract: To improve the ECF leveling effect, according to the actual work of anodic and cathode surface micro-profile, based on the electrodynamics knowledge, established the mathematical model of current field. On the basis of this use of some software to simulate and proceeded numerical calculation, obtained for the influence rule the different cathode surface profile of the current field distribution, and was verified by the experiment. The experimental results show that the variation of the cathode surface micro-profile by changing the current distribution to affect the surface of the anodic and influence of leveling effect by copying the phenomenon will be its own surface profile is copied to the anode. The cathode surface profile is more pointed the affect for the anodic surface will be more obvious.

Abstract: Electrochemical finishing with pulsed current (ECFP) is introduced in this paper. The main process parameters, such as electric parameter and inter-electrode gap, etc., were investigated. The results show that the ECFP is an effective finishing method for improving the machining quality as the result of the machining mechanism. The related experimental results show that the obtained surface quality and dimensional accuracy are improved significantly as the result of the application of the pulsed current. Moreover, machining quality is increased with shorter pulses.