New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Study of corrective abrasive finishing for plane surfaces using magnetic abrasive finishing processes

On the basis of ordinary plane magnetic abrasive finishing,a finishing method is proposed that can improve the flatness of a plane workpiece.In this method,the feed speed is varied during finishing according to the profile curve of the initial surface and the material removal efficiency,to control the effective finishing time in different areas and thereby improve the surface flatness.A small magnetic pole with an end face diameter of 1 mm is designed,and a ferromagnetic plate is placed under the workpiece to improve the uniformity of the magnetic field distribution near the magnetic pole.An experiment on an A5052 aluminum alloy plate workpiece shows that after 60 min of finishing using the proposed method,the extreme difference of the workpiece surface can be reduced from 14.317μm to 2.18μm,and the standard deviation can be reduced from 3.322μm to 0.417μm.At the same time,according to the measurement results,a similar flatness can be achieved at different positions on the finishing area.Thus,the proposed variable-speed finishing method leads to obvious improvements in flatness.

Ultrasonic magnetic abrasive finishing

Put forward a new kind of polishing method,ultrasonic magnetic abrasive fin-ishing(UMAF),and studied its mechanism of improving polishing efficiency.By analyzingall kind of forces acting on single abrasive particle in the polishing process and calculatingthe Size of the composition of forces,get the conclusion that UMAF will enhance the effi-ciency of the normal magnetic abrasive finishing(MAF)due to the ultrasonic vibration in-creases the cutting force and depth.At last the idea of designing the UMAF system basedon numerical control milling machine is put forward which is convenient to setup and willaccelerate the practical application of MAF.

Investigation of the application of a magnetic abrasive finishing process using an alternating magnetic field for finishing micro-grooves

A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.

Hybrid post-processing effects of magnetic abrasive finishing and heat treatment on surface integrity and mechanical properties of additively manufactured Inconel 718 superalloys

Desired microstructure and surface integrity are critical to achieving the high performance of additively manufactured components.In the present work,the hybrid post-processes of magnetic abrasive finishing(MAF)and post-heat treatment(HT)were applied to the additively manufactured Inconel718 superalloys.Their hybrid effects and influencing mechanism on the surface quality and mechanical properties of the additively manufactured samples have been studied comparatively.The results show that the MAF process effectively reduces the surface roughness by more than an order of magnitude due to the flexibility and geometric consistency of the magnetic particles and abrasives with the finished surfaces.The proper sequence of MAF and HT obtains enhanced mechanical properties for the homogenized-MAF-aged sample with the yield strength of 1147 MPa,the ultimate tensile strength of 1334 MPa,and the elongation of 22.9%,which exceeds the standard wrought material.The surface integrity,compressive residual stress field,and grain refinement induced by the MAF and subsequent aging heat treatment increase the cracking resistance and delay the fracture failure,which significantly benefits the mechanical properties.The MAF process combined with proper post-heat treatment provides an effective pathway to improve the mechanical properties of additively manufactured materials.