金刚石与磨料磨具工程

Key factors affecting the performance of diamond wire drawing die coatings

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0104

Abstract(808)

Abstract:
Abstract： Diamond has high hardness, elastic modulus and other properties, irreplaceable role in the tool market, for the relevant enterprises to bring stable earnings.The diamond wire drawing die is extensively employed in the metal drawing and strand tightening fields, primarily due to its remarkable hardness. This attribute enables the die to withstand the immense pressures and friction encountered during the drawing process, ensuring that the wires are pulled through with precision and minimal resistance. The high hardness of the diamond not only facilitates the reduction of the wire diameter but also contributes to the integrity and strength of the finished product. The metal drawing properties of diamond coating are closely related to the microstructure.
【Objectives】In this research, the selection of two pivotal temperature 900℃ and 950℃, was based on extensive prior experimentation. These temperatures were chosen for their significant impact on the material's properties and the outcomes of the processes. The effect of the two processes on microstructure and the difference of failure mechanism were studied.
【Methods】Based on the simulation method, the temperature distribution in the drawing die is analyzed, Scanning Electron Microscopy (SEM) is employed to observe the surface topography of diamond drawing die at high magnification. X-ray Diffraction (XRD) analysis is then conducted to investigate the crystallographic structure of the diamond drawing die. Additionally, Raman spectroscopy is used to analyze quality of the diamond drawing die.
【Results】The results show that the temperature gradient inside the die is small so the direct effect of temperature on diamond coating deposition is small. High temperature can promote carbon active groups to enter the compression and sizing regions to form nanodiamonds, while lower temperature will weaken the diffusion ability of carbon active groups and form micrometer diamonds in the compression and sizing regions. Nanometer diamond coating has good performance, but weak binding force leads to the failure of large diamond coating. Micrometer diamond film hardness is higher, surface roughness control is difficult, will lead to a coarse metal surface.
【Conclusions】Based on this analysis, a method of in-situ deposition of nanometer diamond coating on micron diamond coating is proposed in this study, which can effectively improve the service life of wire drawing die, the wire drawing distance can be increased to more than 100km.

Experimental Study on Magnetic Abrasive Finishing of Inner Pipe Surface Based on Optimized Halbach Array

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0092

Abstract(783)

Abstract:
Objectives:To address the issue of low magnetic induction intensity and insufficient renewal of magnetic abrasive particles in magnetic abrasive finishing (MAF) of pipes, which results in low inner surface machining efficiency.

Methods:This paper proposes a novel method to enhance the finishing process. This method utilizes an optimized Bilateral Halbach array magnetic pole structure to improve the magnetic induction intensity and gradient within a confined space. Firstly, finite element software was used to analyze the magnetic field distribution of various magnetic pole structures. The Bilateral Halbach array magnetic poles were found to produce a stronger single-peak magnetic field in the machining area compared to other magnetic pole structures. Secondly, theoretical and simulation models were employed to identify the auxiliary magnetic pole height and thickness as sensitive parameters affecting the magnetic induction intensity and gradient of the Halbach array magnetic poles. These parameters were then used as optimization variables. Neural networks were utilized to fit the predictive model, ensuring accurate representation of the relationship between these parameters and the resulting magnetic field characteristics. The Non-dominated Sorting Genetic Algorithm Ⅱ (NSGA-Ⅱ) was applied to the predictive model to seek the Pareto optimal solution set, thereby determining the optimal configuration of the Halbach array. The use of NSGA-Ⅱ allowed for the simultaneous optimization of multiple objectives, ensuring that the final design provided a balance between high magnetic induction intensity and gradient. This optimal configuration, combined with the radial reciprocating feed of the magnetic poles, aimed to increase grinding pressure while simultaneously enhancing the turnover and renewal of the magnetic abrasive particles. Finally, the performance of different magnetic pole structures at two different rotational speeds was validated through simulations and experimental tests. The magnetic abrasive particle dynamics were simulated to provide insights into their behavior under varying conditions, while experimental tests confirmed the practical applicability of the theoretical and simulation findings.

Results:Experimental validation demonstrated that the optimized Bilateral Halbach array magnetic poles effectively increased magnetic induction intensity and gradient. Compared to the traditional N-S pole structure, the maximum magnetic induction intensity increased by 60%, and the magnetic field gradient improved by -30 mT/mm. The magnetic brush within the pipe exhibited stronger agglomeration strength, leading to higher processing efficiency. After 30 minutes of processing, the inner surface roughness of the pipe decreased to Ra 0.068 μm. The inner surface's oxide layer and original defects were completely removed, leaving only uniform transverse machining marks. The efficiency of the MAF process was improved by 90%.

Conclusions:The MAF process efficiency was improved by 90%, demonstrating the substantial benefits of the optimized Halbach array. The higher grinding pressure and more frequent turnover of the magnetic abrasive particles led to faster and more effective material removal, enhancing the overall efficiency of the finishing process. The optimized Bilateral Halbach array magnetic pole structure effectively enhanced the magnetic induction intensity and gradient within the pipe, leading to significant improvements in the efficiency and quality of the MAF process. During the finishing process, the magnetic brush inside the pipe exhibited high agglomeration strength, reducing the loss of magnetic abrasive particles and increasing grinding pressure. The frequent turnover and renewal of the magnetic abrasive particles extended their lifespan, ensuring consistent grinding efficiency and achieving a high-quality surface finish.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0046

Abstract(920)

Abstract:

Prediction of grinding surface roughness of Al2O3-based insulating coating on bearing surface considering the change of grinding wheel surface morphology

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0118

Abstract(1008)

Abstract:
To improve the prediction accuracy of grinding surface roughness of Al2O3-based ceramic insulating coating on bearing surface, a BP neural network prediction model was established which was consistent with the actual machining process. A method for measuring grinding wheel surface and quantifying abrasive particle characteristic parameters was proposed based on the principle of spectral confocal. A neural network prediction model for workpiece surface roughness was established, which took characteristic parameter K of grinding wheel surface, grinding wheel speed ω, workpiece feed speed υ, cutting depth ρ and normal grinding force F as input parameters. The model could directly reflect the time-varying state of grinding wheel surface. Finally, the prediction performance of the network was verified by the known grinding samples and the four groups of unknown test samples after grinding wheel passivation. For the known samples, the roughness predicted by BP network is consistent with the actual roughness, and the network output error is less than ±0.04μm. Further using the network for the grinding wheel after passivation to predict the unknown grinding test samples, the accuracy of the network prediction decreases, and the maximum error percentage is less than 20%. The neural network, which includes the characteristic parameters of abrasive particles on grinding wheel surface, can be used to predict the workpiece roughness of Al2O3-based ceramic insulation coating on bearing surface under the transient state of abrasive wear of grinding wheel, and the network has a certain generalization ability for unknown samples.

Effect of pad and slurry on fixed abrasive polishing of gallium oxide crystal

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0043

Abstract(1546)

Abstract:
Gallium oxide crystal is the most representative fourth generation semiconductor material with the advantages of high band gap, high voltage resistance and short absorption cutoff edge, and has broad application prospects. Gallium oxide crystal is prone to micro-cracks, scratches and other surface defects in the polishing process, which is difficult to achieve high-quality surface processing and cannot meet the requirements of the corresponding devices. Moreover, the existing polishing process of gallium oxide crystal is complex and inefficient. Fixed abrasive polishing technology has the advantages of controllable abrasive distribution and depth of cut, and high utilization rate of abrasive grain. Fixed abrasive polishing was used, and the effect of pad and slurry on material removal rate and surface quality were explored in fixed abrasive polishing of gallium oxide crystal. The results show that when the hardness of the polishing pad is moderate II, the abrasive concentration is 100%, and the slurry additive is oxalic acid, material removal rate is 68 nm/min, and the surface roughness Sa value is 3.17 nm in fixed abrasive polishing gallium oxide crystal. Fixed abrasive polishing technology can achieve efficient and high-quality polishing of gallium oxide crystal

Development of CAM system for automatic compound dressing of superabrasive grinding wheels

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0061

Abstract(1243)

Abstract:
In the field of superabrasive wheel dressing, multi-process composite dressing has obvious advantages, but there is no research related to the automation system of grinding wheel composite dressing. In order to make the integration of multiple processes in the composite dressing method more systematic and improve the dressing efficiency of shaped grinding wheels, this paper develops a CAM system by self-developed laser-mechanical composite dressing equipment, which can, according to different grinding wheel section shapes, automatically plan the dressing trajectory under multiple processes and dressing strategies, calculate the dressing toolpath with planar three-axis linkage, automatically generate the machining code, and at the same time design a visualisation interface to simulate the machining process. The results of dressing experiments on 150# diamond bronze bonded grinding wheels show that the system can generate machining programs for laser roughing, semi-finishing and mechanical finishing without collision and overcutting of the machine tool, and significantly improve the programming efficiency of the compound dressing method. And the dressing wheel profile error is within 9.1 µm and circular runout error is 6.1 µm.

Study on the Mechanism and Process Magnetorheological Variable Gap Dynamic Pressure Planarization Finishing

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0004

Abstract(1211)

Abstract:
In order to improve the polishing efficiency of magnetorheological polishing and realize the high-efficiency, high-quality and ultra smooth planarization of photoelectric wafer, a magnetorheological variable gap dynamic pressure planarization method is proposed. In this paper, the changes of material removal rate and surface roughness of sapphire wafer surface polishing with processing time under different variable gap conditions are studied, and the dynamic pressure flattening mechanism of magnetorheological variable gap is deeply analyzed. The results show that the dynamic change of polishing pressure and the extrusion strengthening effect of MR fluid can be produced by applying axial low-frequency extrusion vibration to MR polishing fluid, and the polishing efficiency and polishing effect can be significantly improved. After 120 min of magnetorheological variable gap dynamic pressure flattening, the surface roughness of sapphire wafer decreased from Ra 7 nm to Ra 0.306 nm, and the material removal rate was 5.519 nm / min. Compared with constant gap magnetorheological polishing, the surface roughness decreased by 49% and the material removal rate increased by 55.1%; By changing the moving speed of variable clearance, the flow field characteristics can be controlled. Choosing the appropriate workpiece pressing speed and workpiece lifting speed is conducive to improve the polishing efficiency and surface quality.

Effect of Fe₃O₄ Characteristics on Properties of Solid-phase Fenton Reaction Lapping Pellets for Single-Crystal SiC

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0008

Abstract(1212)

Abstract:
To improve the lapping quality and processing efficiency of single-crystal SiC, solid-state Fenton reaction lapping pellets were prepared. Effects of particle size and concentration of Fe₃O₄solid-phase catalyst on the physical properties (hardness, flexural strength, porosity), catalytic performance, and lapping performance of single-crystal SiC were studied. The results showed that with the increase of Fe₃O₄ particle size, the hardness, flexural strength, porosity, and catalytic performance of the lapping pellets all decreased, the material removal rate (MRR) decreased from 43.12 nm/min to 36.82 nm/min, and the surface roughness (Ra) increased from 1.06 nm to 3.72 nm. As the Fe₃O₄ concentration increased, the hardness and flexural strength of the lapping pellets decreased, and the porosity and catalytic performance increased. Although the material removal rate decreased, the surface roughness (Ra) decreased firstly and then increased. The MRR decreased from 40.14 nm/min to 33.51 nm/min, the surface roughness (Ra) was 3.25 nm, 1.75 nm and 1.88 nm. In this experiment, when the Fe₃O₄ particle size and the concentration was 0.5 µm and 29 wt.%, the processing effect was the best, the MRR and the surface roughness (Ra) was 43.13 nm/min and 1.06 nm.

Latest Accepted Articles

NewsMore>