![]() ![]() It is a very tough abrasive, so it lasts longer, however it is generally not as hard or sharp, and thus requires higher pressures to be effective. Zircon, or zirconium silicate, is another less common abrasive used for coarse grinding. For metallographic applications, polycrystalline diamond is recommended as a rough polishing abrasive. Although diamond would be ideal for coarse grinding, its price makes it a very inefficient grinding material for anything except for hard ceramics. It has a cubic crystal structure, and is available as a natural or an artificial product. Is the hardest material known to man (mHV). Note that larger coated or bonded grit sizes of alumina are commercially available, however they are not ideal for metallographic applications because they become dull, resulting in lower cut rates and higher surface and subsurface damage. Unlike SiC, alumina breaks down relatively easily to submicron or colloidal particles. Alumina abrasives are used primarily as a final polishing abrasive because of their high hardness and durability. ![]() It exits in either the softer gamma (mohs 8) or harder alpha (mHV) phase. 150x)Īlumina is a naturally occurring material (Bauxite). SEM micrograph of 600 grit SiC Abrasive Paper (original mag. Note that coated abrasives are not quite coplanar, thus SiC papers produce the maximum efficiency (cut rate, stock removal and minimal damage) because new abrasive is exposed as the old abrasive breaks down. This is achieved by aligning the abrasive particles approximately normal to the backing. For metallographic preparation, SiC abrasives are used in abrasive blades and for coated abrasive grinding papers ranging from very coarse 60 grit to very fine 1200 grit sizes.īonded or coated abrasive papers of SiC are designed so that the abrasive will have a large number of cutting points (negative abrasive rank angle). ![]() SiC is an excellent abrasive for maximizing cutting rates while minimizing surface and subsurface damage. It is also somewhat brittle, and therefore it cleaves easily to produce sharp new edges (self sharpening). It is an ideal abrasive for cutting and grinding because of its hardness and sharp edges. It has a hexagonal-rhombohedral crystal structure and has a hardness of approximately 2500 HV. SiC is a manufactured abrasive produced by a high temperature reaction between silica and carbon. We are not responsible for any errors.The following are the most common metallographic abrasives: The grit sizes are defined by the number of lines per inch (25.4 mm) length of each sieve e.g. MM Micro-mesh grit in comparison to other standards. A Micron row is added to each FEPA P, FEPA F, JIS und ANSI row for comparison. As measuring unit it describes 1 thousandth of a millimeter (1 μ = 0.001 mm). MICRON (μ) is the letter "micron" in the Greek alphabet. JIS (Japanese Industrial Standard) issued by the Japanese Standards Association.ĪNSI American National Standards Institute. The decisive factor for comparison is FEPA F. The FEPA distinquishes between grain for sanding paper (FEPA P) and grain for sharpening stones or wheels (FEPA F) Definitions:įEPA (Fédération Européenne des Fabricants de Produits Abrasifs) Federation of European Producers of Abrasives. Use conventional abrasives as normal prior to going into the Micro-mesh stage. Use this Conversion chart to view the different standards and as a guide to know when you can start using Micro-mesh. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |