Grits

Steel additive Steel anode Steel bearings Steel cans Steel cathodes Steel, decaiburized Steel drums Steel grit... 

There are three basic forms of abrasives grit (loose, granular, or powdered particles) bonded materials (particles are bonded iato wheels, segments, or stick shapes) and coated materials (particles are bonded to paper, plastic, cloth, or metal). 

Abrasive appHcations for industrial diamonds include thek use in rock drilling, as tools for dressing and tmeing abrasive wheels, in polishing and cutting operations (as a loose powder), and as abrasive grits in bonded wheels and coated abrasive products. 

Miscellaneous Natural Abrasives. Powdered feldspar [68476-25-5] is used as a mild abrasive in cleansing powders, and clays are sometimes used in polishing powders. StauroHte [12182-56-8] is a complex hydrated aluminosiHcate of kon, of high density (3.74—3.83 g/mL) and a hardness of 7 to 8 on Mohs scale. It is primarily used as a sandblasting grit, but siHcosis hazards had cut production in 1987 about 25% compared to that... 

Steel Shot and Grit. Steel shot and grit are also widely used ia grit blasting and abrasive finishing. In 1989, 220, 196 metric tons of metallic abrasives were produced in the United States with a combined value of 89.55 million (20). 

Grit Diameter, p.m Grit Diameter, p.m Grit Diameter, p.m... 

Stmeture. The stmcture designation may or may not be given. It is numeric 0 represents the closest possible packing of abrasive grits, and ascending numbers correspond to incrementally less abrasive per unit volume of wheel (wider spaced grits). 

Hardness. Glass hardness tests usually measure the resistance to abrasion by grinding or grit-blasting, resistance to scratching, or penetration by an indenter. The method to be used depends on expected service conditions. Knoop hardness (Table 4) is commonly used, because other methods usually fracture the glass. 

The standard Rockwell test requires a relatively smooth surface (120 grit or better) for reproducibiUty. Superficial Rockwell test samples must be ground to 600 grit or better for accuracy and reproducibiUty. 

Surface finish requirements for the Vickers test vary with the test load. Heavy load tests can be made on a 120 grit ground surface. At low loads increasingly finer surface preparation is required, approaching that for metaHographic specimens, to permit accurate diamond indentation measurements. 

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

Zinc arc spraying is an inexpensive process in terms of equipment and raw materials. Only 55—110 g/m is required for a standard 0.05—0.10 mm Zn thickness. It is more labor intensive, however. Grit blasting is a slow process, at a rate of 4.5 m /h. AppHcation of an adhesive paint layer is much quicker, 24 m /h, although the painted part must be baked or allowed to air dry. Arc sprayed 2inc is appHed at a rate of 9—36 m /h to maintain the plastic temperature below 65°C. The actual price of the product depends on part complexity, number of parts, and part size. A typical price in 1994 was in the range of 10—32/m. ... 

Eig. 8. Illustration of the effect of nitriding on the wear resistance of a steel blasted with steel grit A, 300 HV steel B, 750 HV steel case hardened by carburizing and C, 1100 HV steel nitrided at 500°C for 60 h (17). HV = Vickers hardness. 

The grit content of coarse mica is deterrnined by the vanning method. A 25-g sample of dry mica is placed on a vanning plaque or a 21.6 x 28-cm... 

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