The Research On Property And Technaology Of Pack Boronizing On 45 Steel

60Si2Mn spring steel, as the main material of bar-sieve plate in vibration screening field has the shortcoming of low hardness which results in short service life of bar-sieve plate and influences it's practical performance. Boronizing can significantly improve the hardness, wear resistance, corrosion resistance of the component, increase the hardness of surface and make it possible to increase the life of bar-sieve plate.Boronizing process parameters and boronizing agent formula of 45 steel pack boronizing in this article optimized by means of single factor tests and orthogonal experiments. The observation of the cross-section microstructure, the surface morphology of samples and the thickness of and elements distribution in the boride layer is finished with the help of optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The FeB and Fe2B is distinguished through eroding the boride layer by "three K" kit, and the phase structure of boride layer is analyzed by means of X-ray diffraction. The microhardness of boride layer is measured by microhardness tester and the wear resistance of samples is tested by the low stress abrasion testing machine which can imitate the work condition of bar-sieve plate, then analyzed the possibility of this process used on bar-sieve plate based on the results.The results shows that:the optimum processing parameters of boronizing on 45 steel are:boronizing at 920℃for 6 hours, Na2B4O710%, KBF4 10%, NH4Cl 1%, 15% ferrosilicon,20% charcoal, activated carbon 2%, residual graphite. The thickness of boride layer which is dentate distribution and composed with the single-phase Fe2B can reach 134μm under the optimum processing.The contents of B elements showed a decreased tendency from the surface to center of sample; the contents of C, Si elements were high in the surface and low in boride layerwhile the enrichment of two elements appeared in the dense zones. The ratio of B, Fe atoms in the boride layer is close to 1:2, this tests the boride layer is mainly composed of Fe2B. As the mainly brittleness of boride layer, spalling brittleness is caused by the nature brittleness of boride Fe2B and the porosity and holes in boride layer. The boride layer composed of single-phase Fe2B with microhardness from 1300HV0.1 to 1400HV0.1 was obtained after boronizing at 920℃for 6h. Gentle hardness gradient of surface, lower spalling brittleness of boride layer and the best wear resistance can be obtained through cooling in the air after boronizing on 45 steel, The wear experiments shows that the wear resistance is 18 times more than that of 60Si2Mn which are used at the vibrating screen. So the 45 steel with boronizing can be used on bar-sieve plate.The penetration recycling test was conducted. The result shows that the thickness of boride layer can reach 128μm by the use of recovery penetration with 30% new penetration, thus the penetration costs can reduce about 70%.