Papers by Author: Zi Rui Pang

Abstract: To meet the requirements of super-high speed vitrified bond of CBN grinding wheel that should be low-melting, high strength and multi-foams, performance of nano-ceramic bond were researched in this paper. Four types of bond which major glass components was R₂O+RO-B₂O₃- -Al₂O₃-SiO₂ have been compounded with pure raw chemical materials. In order to improve the strength of bond, nano-materials were added into formulations of the vitrified bond. And experiments results showed that compared with traditional vitrified bond the new nano-ceramic bond had a significant advantage at its refractoriness, expansion coefficient, surface morphology and bending strength. Especially, the bending strength of 4# nano-ceramic bond had reached to 83.75 MPa and its refractoriness was 790 °C. It proved that 4# nano-ceramic bond was more suitable for super-high speed CBN grinding wheel.

Abstract: Technology and metallographic of three kinds of representative gears were analyzed in this paper according to characteristics of carburizing and quenching, and technology problems met with during the carburization process of large low-alloy gears in Citic Heavy Industries Co., Ltd were also taken into account. Three conclusions are demonstrated through experimental results. Firstly, although carburization technology is normal, grinding cracks can be caused by hard particles included in matrix. Secondly, if carbon concentration of carburization layer is too high or too steep in carburizing technology, carbide will aggregate in reticular or structural stress will not be average during the subsequent quenching technology. And therefore grinding cracks are caused. Moreover, retained austenite of surface layer and subsurface layer will be over standard and thus grinding cracks will be caused if quenching temperature is too high during quenching technology after carburizing.

Abstract: It is different from the traditional integrated super high-speed grinding wheel, the centrifugal force has greater impact on segmented grinding wheel in super high-speed rotation. In this paper, in order to ensure the safety of super high-speed grinding wheel, models for the connection between inner micro-unit’s displacement and stress of wheel matrix were established to optimize high-speed grinding wheel section form, reduce the centrifugal stress and control the radial displacement of grinding wheel. Consider the structural and mechanical characteristics of wheel matrix, strength check of the theoretical formula were also established. Taking into account the factors of aerodynamic and wheel connector effects, at last the design of segmented super high-speed grinding matrix was optimized with finite element method.

Abstract: Three-dimensional cutting process of single grain in the shape of polygonal pyramid was simulated by coupled Euler-Lagrange method. The method makes the workpiece material free from its meshes. The material allowance can be removed without mesh separation criterion. The simulation results show that workpiece material flows to the side and front owing to the pressing of cutting plane. Chip flows out along the front of the grain upward. The deformation of workpiece material contacted with grain edge is very severe. Therefore there is large machining stress concentration at the contact zone of grain edge. It results in biggish residual stress and cutting temperature at the side and bottom of the groove. The contact stress at edge angle of abrasive grain is biggest. Therefore grain wear is severe in the position

Abstract: In this paper, grinding performance and Manufacturing process of vitrified CBN wheel were described for Quick-point grinding at 200m/s. In order to insure security rotation of wheel, wheel core was optimized at 200m/s based on ANSYS software. Four kinds of domestic abrasives were tested for their compressive strength, impact toughness, microcosmic crystal photographs, and oxidation temperature, high temperature performance baked at 870 °C, by right of advanced apparatus such as SEM etc. Simultaneity vitrified bonds, wheel segments and adhesive techniques were also discussed. At last, grinding performance of Quick-point Grinding wheel was tested.

Abstract: In this paper, we emphasize that residual stresses in a ground surface are primarily generated due to grinding zone temperature effect, and discuss grinding zone temperature can be debased based on characteristics of the thin vitrified bond CBN wheel and quick-point grinding. Via experimental results of 5 group working procedures, we find that surface roughness Ra showed a tendency to reduce slightly with infeed rate reduced, cut depth increased, grinding wheel speed and grinding variable angle increased, the favorable residual compressive stress could obtained along with variables angle(α, β) increased, the sub-surface white etching layer and tempered martensite layer in size become thinner with α, β angle and grinding wheel speed increased when removal rate Z=0.06mm3/mm keep constant in quick-point grinding, by contraries, surface quality were decreased entirely when variables angle(α, β) equal to zero. The results indicate it is important that grinding variable angle were choice in quick-point grinding for to obtain favorable residual compressive stress.