Papers by Keyword: Abrasive

Abstract: Abrasive properties of selected rocks and their influence on button bit wear were investigated. Rock samples were obtained from three locations in Southwest, Nigeria. These samples were tested in the laboratory for grain size and circularity factor. Also, porosity, Equivalent Quartz content (EQC), Rock Hardness Number (RHN), Rock Abrasivity Index (RAI) and Uniaxial Compressive Strength were determined. Bit button lengths consumed were measured at regular interval as drilling operation progresses. Results of grain size revealed that medium feldspar granite has least average grain size varying from 0.12 – 0.14 mm. There is possibility that rate of drilling may be low while drilling through this rock. The values of circularity factor varied from 0.624 for medium feldspar granite to 0.786 for coarse muscovite granite. The mean values of porosity varied from between 0.85 and 1.33% for medium feldspar granite and coarse muscovite granite respectively. Biotite hornblende granite has the highest mean uniaxial compressive strength value of 119.48 MPa while coarse muscovite granite has the least mean value of 90.65 MPa. The values of free silica, EQC, RHN, and RAI varied from 35.93 – 51.35%, 45.60 – 67.21%, 575.52 – 821.64 kg/mm³ and 4133.64 – 7003.71 respectively. It was observed that grain size affects the void size in these rocks, which accounted for least porosity value obtained in medium feldspar granite. Average bit button length consumed varied from 15.56 – 24.54 mm for gauge button while length of centre button varied from 13.00 – 19.61 mm. Higher gauge button length consumption could be inferred that it effects the cutting, crushing and wedging of rock mineral components at rock-bit interface. The understanding of grain size, circularity factor and abrasive properties will provide adequate information for quarry to select appropriate bit and drilling machine.

Abstract: The composition of each grinding wheel depends on the specific application, and nowadays, there are many types of grinding wheels on the market. Bakelite bonded grinding wheels are fast becoming the standard choice for grinding and finishing processes in automotive, aerospace and other special fields of industry. Increasing requirements on higher quality and lifetime push manufacture to continuous research and development in this field. From that reason, it is necessary to characterize the structure and properties of already produced commercial grinding tools. In this contribution, two in chemical composition identical bakelite bonded grinding wheels with different properties were studied. Processing parameter like compression force is the main factor resulting in either hard grinding wheel for machining soft materials or soft grinding wheel for machining hard materials. The main components of both grinding wheels are abrasive particles of brown alumina (Al₂O₃) and two bonding agents based on synthetic rubber and bakelite. In addition, grinding wheels contain additives, e.g. vulcanization accelerators, fillers etc. to improve functional properties of grinding wheel. Fractures and metallographic samples morphology was studied by scanning electron microscopy. Porosity of grinding wheels was estimated using image analysis. Hardness of binder and abrasive brown alumina particles was measured by Rockwell hardness test.

Abstract: The high-speed grinding wheel can be defined as a self-sharpening composite structural tool composed from abrasive grains held in a specific binder. The main properties of grinding wheels depend on the type of abrasive elements, grit size, grade, binder and the resulting structure, which is influenced by several crucial technological processing steps. Preparation of an initial mixture of abrasive particles together with permanent binder’s mixture and temporary binder followed by pressing and high-temperature sintering is the essential technological step in the manufacturing of high-quality grinding wheels. High demands placed on functionality and quality together with constantly increasing effort to improve existing properties of grinding tools require detailed characterization of all input raw materials. For further research and development is crucial know, how each technological step can influence the final quality of the product. This contribution is focused on the characterization of four alumina abrasives with different grit size and two in chemical composition different binder mixtures which were used for the production of two different high-speed grinding wheels. Initial abrasive grains, binders and metallographic samples of high-speed grinding wheels were evaluated by means of scanning electron microscopy. The porosity of grinding wheels with different binding agents was also determined ustilizing digital image analysis technique.

Abstract: In this paper, a series of chemical mechanical polishing (CMP) experiments for magnesia alumina (Mg-Al) spinel were carried out with different abrasives, and the materials removal rate (MRR) and surface quality was evaluated to explore their different effects. The scanning electron microscope (SEM) and laser particle size analyzer were also employed to test the micro-shape and size distribution of abrasives. Then, the mechanism of different effects with different abrasives was analyzed in CMP for Mg-Al spinel. Those experimental results suggest that different subjecting pressure ratios of abrasives to polishing pad with different abrasive are the key factors leading to difference polishing performances in CMP.

Abstract: The dimension stone polishing consists of eliminating the surface roughness of the slabs with the use of fickerts. The main tools used for this activity are composed of epoxy resin, derived from petroleum, which contains chemical elements with harmful potential to the environment and human health. To overcome this problem, it is necessary to develop new technologies with the lowest environmental impact in the life cycle, from the raw material acquisition to the waste disposal. This study aims to contribute to the improvement of an ecological fickert developed by the Centre for Mineral Technology (CETEM). The fickerts presented here are composed of castor oil resin, silicon carbide and silica from rice hull ash. Two different compositional formulas were used for the preparation of the pieces that were tested in an industrial polishing machine. The results showed that the formula with higher percentage of fillers showed better performance, expressed by the relation between the loss of mass of the pieces and the increase of gloss on the surface of the slab. Other particularities of the product, as the high abrasion resistance of the matrix that reduced the cutting function, could be solved by choosing a filler with a lower hardness. This fact allows to infer that this line of research presents great potential of applicability in the dimension stones market.

Abstract: The article presents the results of experimental studies of differences in the nature of impact destruction of single garnet grains penetrating the target material, and presents the results of numerical simulation (modeling) of the contact interaction of an abrasive particle with a flat obstacle, which allowed determining the volume ablation of the material under the action of a single abrasive particle, and makes it possible to predict the performance of waterjet cutting.

Abstract: The traditional finishing processes are incapable of producing required surface finish and other characteristics in difficult-to machine materials like Nickel based superalloys and also complex geometrical shapes of engineering components. Hence to achieve these goals non-traditional micro-machining processes have been developed. Extrusion honing (EH) is one of the non-traditional micro-machining process to debur, radius, polish, and remove recast layer of components in a wide range of applications. In this process material is removed from the work-piece by flowing abrasive laden medium under pressure through or past the work surface to be finished. Components made up of complex passages having surface/areas inaccessible to traditional methods can be finished to high quality and precision by this process. Hastelloy C22 offers resistance to both aqueous corrosion and attack at elevated temperatures and it is a difficult metal to machine using traditional techniques. In this study, micro finishing of internal surface of Hastelloy C22 material having predrilled passage diameters 7, 8, 9 and 10 mm have been performed in an indigenously built hydraulic operated one way extrusion honing setup. For the present EH process, patented polymer mixed with SiC abrasive at 35% volume concentration was used as carrier medium. The study was performed for 46, 54, and 60 grit sizes of SiC abrasive. The material removal in EH process varies with passage diameter and grit size of abrasives at each trial. A feed forward back propagation neural network model has been developed for the prediction of material removal and it has successfully predicted material removed in each trial of EH process.

Abstract: This paper describes the existing methods for determining the corrosion-erosion wear of materials, and describes a technique developed to assess the stability of oilfield pipes for corrosion-abrasive wear. The results of comparative tests on this method of steels 13HFA and St20 are presented.

Abstract: The article deals with the method of obtaining a hard chromium coating on details of the "body of rotation" type with the use of an abrasive tool. The influence of the composition and hardness of the elastic abrasive tool on the results of galvanomechanical chromium plating of rotating cylindrical parts has been studied. Binder compositions for an abrasive tool used to improve the roughness of the deposited chromium layer have been developed. A series of experimental studies has been carried out with chromium plating of steel cylindrical parts with simultaneous abrasive processing. Beforehand, an abrasive tool with previously developed binder formulations was manufactured. The obtained results of the influence of the characteristics of the abrasive tool and its pressing force on the chromium-plated part on the quality of the precipitated chromium made it possible to determine the optimum modes for obtaining a coating of the required thickness. Also, a suitable abrasive tool has been chosen to obtain a coating of proper quality.

Abstract: The article deals with the method of obtaining a hard chromium coating with using abrasive tool. The influence of the pressing force of the abrasive tool, the rotation speed of the part, the temperature of the electrolyte on the results of galvanomechanical chromium plating of rotating cylindrical parts has been studied. A special abrasive tool has been developed for use in the galvanic mechanical coating of metal parts. The tool is made on a polymer bond. The effect of the electrolyte temperature on the quality of the precipitated chromium is revealed.