A further type of material heat treatment is hardening (H) and austempering. During steel hardening, first the carbon is dissolved in the austenitic zone. The carbon precipitation that takes place at normal cooling speeds is then stifled by a high cooling speed. Thus, at supercritical cooling speeds, after falling short of the Ms — temperature […]
Рубрика: Manufacturing Processes 2
4.8. Grinding Brittle Materials
The designation “brittle”, often used in manufacturing, characterises a certain material group according to their mechanical properties. High brittleness, i. e. low fracture-resistance, and hardness represent a combination of material properties that, on the one hand, influences the range of uses of these materials, but also determines their machinability and workability properties. Several factors influence […]
Methods with Stationary Tools
Non-rotating or stationary dressing tools do not exhibit any movement in the peripheral direction of the grinding wheel. The grinding wheel profile originates by means of axial movement along the wheel contour, comparably to a turning process (Fig. 6-2). Between the dressing tool and the rotating grinding wheel, there is a radial dressing feed rate […]
Grinding Temperatures
The by far largest amount of mechanical energy introduced to the process is converted to heat during grinding. This heat is then conducted away by chips, cooling lubricant, the grinding wheel and the workpiece. Depending on the process conditions, the amount of heat flow into the workpiece amount to up to 85 % [MARI77, LOWI80, […]
. Source: by H. Frank
The cooling rate of molten corundum largely influences the size of the crystals formed. In the case of the billet method, the corundum billet, weighing up to 20 tons, cools slowly. Cooling times can range from 10 to 14 days. In this way, generally larger crystals are formed than in the so-called tapping method, in […]
The Manufacture of Vitrified Bonded Grinding Wheels
The production of vitrified bonds also begins with mixing the components. By covering the grits with a temporary binder (e. g. organic adhesive and water), sufficient form stability can be achieved in the blank. The pourable mixture is transferred to the mould and compressed via pressing and shaking methods. In the casting method, the vitrified […]
Hardening and Tempering
The strength of steel can also be increased by hardening and subsequent tempering. In tempering a material, the martensite formed during hardening is specifically brought again to partial disintegration by re-heating, thereby relaxing the crystal lattice. At low annealing temperatures, carbon precipitates in a finely distributed fashion, while at higher temperatures coarser cementite grains develop […]
The Machining Behaviour of Brittle Materials
The machinability of brittle materials significantly variable in contrast to metallic materials due to the characteristics described above. When machining brittle materials, as opposed to machining ductile materials, we proceed from the assumption that, with increasing penetration depths, material separation becomes dominated by the characteristic behaviour of brittle materials, i. e. microcrack formation and resultant […]
Methods with Rotating Tools
Rotating dressing tools execute an additional rotational movement (Fig. 6-4). If the dressing tool has the negative profile of the grinding wheel, only a radial feed motion is necessary. Dressing rollers that do not engage across the entire wheel width require however a lateral feed. Common rotating diamond tools for dressing grinding wheels are: • […]
Methodological Variants according to DIN 8589
6.3.1 Introduction Machining processes of workpieces with grinding wheels is fundamentally distinguished according to DIN 8589, or ISO/ DP 3002/ V. Subdivision is carried out with serial numbers (ON), which are currently in seven figures and describe each method according to its systematics. Proceeding from the upper division ’’separation” in manufacturing processes, we have the […]