Grindability studies of thermomechanically processed advanced high strength steel using sol-gel and fused alumina grain-based grinding wheels

Advanced high strength steels have excellent strength-to-weight ratio and are widely used for automotive and structural applications. Grinding is commonly used as a final machining process for these materials to achieve the required dimensional tolerance and surface quality. In this work, the grindability of as-received microstructure of ferrite-pearlite and in-house developed ferrite-bainite-martensite steels using polycrystalline white fused alumina and microcrystalline sol-gel alumina grinding wheels under flood and minimum quantity lubrication conditions is studied. Grindability of these steels was evaluated based on the wheel wear, grinding forces, force ratio, specific cutting energy, surface roughness (Ra), and surface morphology. The sol-gel alumina wheel was observed with higher wear flat area and forces under all the grinding conditions as compared with white fused alumina wheel. The white fused alumina wheel exhibited higher force ratio values for all the grinding conditions than the sol-gel alumina wheel. The energy required per unit volume of material removal is lower for the white fused alumina wheel in both the steels under flood and minimum quantity lubrication conditions. This is due to the retention of sharpness of abrasive grains by self-sharpening for white fused alumina wheel than the sol-gel alumina. The presence of fractured, melted, and hollow chips on the ferrite-pearlite and ferrite-bainite-martensite steels under both the grinding condition confirms the change in material removal mechanism with the presence of higher wear flat area of the sol-gel alumina wheel. Based on the obtained results, the white fused alumina wheel was found to be a suitable grinding wheel for grinding of both the steels under all grinding conditions compared to the sol-gel alumina wheel.

Grinding Force and Specific Energy in Plunge Grinding of 20CrMnTi with Monolayer Brazed CBN Wheel

In this paper, plunge grinding experiment was conducted on 20CrMnTi with monolayer brazed cubic boron nitride (CBN) wheel. Surface integrity was evaluated through morphology observing and roughness testing. It is found that surface roughness Ra is lower than 0.8μm. Grinding forces were measured and the effects of process parameters (i.e. workpiece speed and depth of cut) on grinding forces were studied. The changing regulation of specific grinding energy with the increase of equivalent chip thickness was revealed. The result shows that both grinding force and specific energy are lower comparing with white fused alumina (WA) wheels. In general, monolayer brazed CBN wheels perform better in grinding of 20CrMnTi than WA wheels.

Effect of Binders on the Properties of Chromia/Alumina Refractory Castables

Refractory castable specimens were prepared using industrial white fused alumina as aggregates, chromium oxide green and ultrafine alumina powder as matrix materials, solid aluminum dihydrogen phosphate (Al(H2PO4)3) or liquid AlPO4 as binder materials. Effect of different binder additions on the propertiSubscript textes of high chromium oxide IGCC refractory castables, such as bulk density, apparent porosity, strength was evaluated and their microstructures were observed by SEM and mercury porosimetry.

Effect of Silica Sol on the Properties of Unfired Mullite Rollers

An unfired mullite roller was produced by using mullite roller waste, white fused alumina, α-Al2O3, clay and micro silica, meanwhile silica sol was used to partially substitute for micro silica as the SiO2 source. The effect of silica sol on the properties of unfired mullite roller was investigated. The results showed that the microstructure and properties of the unfired mullite roller prepared with silica sol were improved. With the increase of silica sol, the COMR, bulk density and thermal shock resistance increased, and the water absorption rate decreased. When silica sol was 8w/t%, treated temperature was 1200°C, the CMOR of unfired mullite roller was more than 50MPa.