High-speed Grinding Wheel Brazed Continuously By Ultra-high Frequency Induction

With the excellent physical properties, superhard abrasive such as diamond and cubic boron nitride are widely used in grinding industry, and have drawn much attention in high efficiency grinding of difficult-to-machine materials in recent decades. The single layer brazed wheels have several advantages such as high bonding strength, high chip storage space, high wheel sharpness and long service time. A great effort has been payed by many researchers in recent decades. However, since the whole wheel will be exposed in rather high temperature during brazing, the thermal deformation of the wheel is beyond control. As a result, the accuracy of the brazed wheel is greatly degraded. This restricts the brazed tools applying to high efficiency grinding, especially high-speed grinding, which becomes the major obstacle of the machining efficiency and quality improvement.Aimed at the challenge of the unexpected wheel deformation after brazing, continuous induction brazing by ultra-high frequency is proposed in this paper. Because of the localized heating area in brazing, the deformation of the wheel could be minimized. Based on this concept, a great effort is payed on the temperature field induce in the inducton brazing, and the accuracy of the brazed high-speed wheel. The main creative contents in this paper are as follows:1) Based on the law of coil projection, the influence factors, such as the ferrite core, the structure of the inductor, on eddy current and temperature distribution has been investigated through experiment and FEM analysis. The optimization design of the inductor has completed. This is the fundament for the continuous brazing by ultra-high frequency induction.2) In order to simulate the process of brazing high-speed wheel by ultra-high frequency induction, experiment platform for continuous induction brazing by ultra-high frequency has been established. The parameters in coutinuous induction brazing, such as heating gap, moving speed, and induction current on the temperature have been investigated. Several groups of countinuous induction brazing parameters have been selected for the brazing with Ag-Cu-Ti filler alloy. A brazing bonding among abrasive grain, filler alloy, and steel substrate is achieved by continuous induction brazing by ultra-high frequency.3) The new-formed reaction products, the interfacial microstructure, and the mechanical property of the joint under different conditions have been detected and investigated. The results reveal that the perfect microstructure of the new-formed compounds could be acquired with induction current 27 A, moving speed 0.5mm/s. The fracture morphology of the joint indicates the bonding matrix has strong joining strength to the abrasive grains. The mechanical properties of abrasive grains are not change during brazing.4) Continuous induction brazing device for super-abrasive wheel has been developed. f400mm brazed super-abrasive high-speed wheels have been fabricated. It has been observed that the deformation of the wheel is less than 16mm after brazing, and the radial runout is 21mm. This indicates the accuracy of the brazed high-speed wheel in this study is the same as the electroplated single layer super-abrasive wheel.5) Experimental studies have carried out for high-speed grinding of engineering ceramics and nickel-base superalloy with the maximum wheel speed 120m/s and 150m/s respectively. The grinding force ratio showed that both the brazed diamond and CBN wheels have good sharpness and satisfied grinding performance. The wheels have strong retention strength to grains, and abrasion wear is primary in the grinding process.