slewing bearing

Mechanical grinding is a method of manufacturing a common metal cutting, the bearing processing industry also been widely used, the bearing parts of heat hardening, or reticular cracking may occur more rules during grinding arrangement of small cracks, known as grinding cracks, it not only affects the appearance of bearing parts, more importantly, also directly affect the quality of the bearing parts. This paper analyzes the causes of bearing parts produced grinding cracks in the grinding process, then take preventive measures, so as to effectively prevent the generation of grinding cracks.
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First, the reasons bearing grinding cracks
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Generating bearing grinding cracks caused by the grinding heat, the surface temperature of the bearing up to 800-1000 ° C or more grinding. Tissue quenched steel is of martensite and residual austenite certain number of them are in a expanded state (without tempering). With increasing expansion and contraction of martensite steel carbon content increases, the steel grinding cracks generated surface of the bearing is particularly important. Effect of grinding heat of retained austenite in hardened steel that is subject to decomposition during grinding, gradually transformed into martensite, martensite this renewed focus on the surface of the part, causing local expansion of the bearing surface, increased parts of the surface stress, stress concentration resulting in grinding, will continue to accelerate the grinding surface of the grinding cracks produced; in addition, the nascent large Chuai martensite, grinding easily accelerate the production of grinding cracks.
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On the other hand, grinding when the grinding machine parts, parts of both pressure and tensile force is, contributing to the generation of grinding cracks. If the cooling is insufficient at the grinding, since the heat generated during grinding, the grinding surface of the sheet sufficient to re-austenitization, quenching and then quenched again into martensite, so that the surface layer of additional stress in the organization, coupled with the amount of heat generated by the grinding surface of the bearing temperature rises fast, fast cooling, which is superimposed the stress and thermal stress may lead to the grinding surface of the grinding cracks generation.
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Second, it characterized in bearing grinding crack
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Usually the grinding cracks significantly different quenching cracks, cracks occur only in the grinding surface of the grinding, shallow, and substantially uniform depth. Lighter grinding cracks perpendicular or nearly parallel to a line perpendicular to the grinding direction and are regularly arranged strips crack, which is a kind of cracks, crack more severe form of tortoiseshell (closed network like), a depth of approximately 0.03 ~ 0.15ram, with obvious cracks after acid etching, which is the second crack.
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Third, grinding cracks Prevention
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From the above analysis of the root cause to know that the generation of the grinding cracks are in a quenched martensite expanded state, the presence of stress. To reduce or eliminate such stress, the stress to be tempered i.e. quenching, tempering is performed, waste of time must be more than 4h. With increasing tempering time, the possibility of grinding cracks decreases. In addition, bearing in rapidly heated to about 100 degrees C and rapid cooling will crack. To prevent cold cracks, the part should be tempered at about 150 to 200 degrees Celsius, if heated to 300 degrees Celsius to continue bearing surface shrinkage cracks again, to prevent the generation of cracks, the bearings should be tempered at about 300 degrees Celsius. It is noteworthy that, bearing around 300 degrees Celsius tempering the hardness will drop, something should not be used. Is produced through a tempering still grinding cracks, which can be tempered or secondary artificial aging treatment, this method is very effective.

Slewing ring

It produces grinding cracks due to heat caused by grinding, so reducing the grinding heat is the key to solve the grinding cracks. Wet milling method is generally employed, but in any case the injection coolant, the coolant no method to arrive at the grinding surface grinding, grinding heat and therefore can not reduce the grinding point. Coolant only part of the grinding point of the grinding wheel and grinding after cooling being passed instantaneously, while the quenching effect of the cooling liquid to make the grinding point. Thus increasing the amount of coolant is one of the main measures to minimize the grinding zone of the grinding heat. If dry milling process, grinding feed less, grinding cracks can be reduced. However, this method is not very significant, and dusty, affecting the work of a bad environment, should not be taken.
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Selection softer durometer, coarser sand to the grinding wheel, grinding heat can be reduced. However, coarser particles can affect parts of the surface roughness, high surface roughness for the part, can not use this method, and therefore subject to certain restrictions. The crude fraction, grinding, selection of both coarse particles coarser soft grinding wheel, the grinding facilitate strength, improve efficiency, and then be fine-grained grinding wheel, grinding feed amount is small. Two points were roughing and finishing, this is the ideal method.
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Self-sharpening properties of a good choice of abrasive wheel, the grinding wheel surface timely removal of waste material, reducing the grinding feed, increasing the number of grinding table speed is reduced, which is an effective way to grinding cracks is reduced.
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The rotational speed of the grinding wheel and part of one of the factors is the main, large wheel rotation runout, ran large parts are grinding cracks incentives. Increase in time accuracy of the grinding wheel and the rotary part so as to eliminate the grinding cracks caused by various factors as much as possible.
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Fourth, the method of preventing the surface of the bearing steel grinding cracks
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In grinding, the grinding cracks generated surface bearing steel, the main method for preventing:
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① reduce grinding heat to solve the grinding cracks.
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② points coarse, fine grinding, both coarse particles selected coarse grinding soft grinding wheel.
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③ Selection good performance since the sharp abrasive wheel, the grinding wheel surface timely removal of waste material, reducing the grinding feed, increasing the number of grinding table speed is reduced.
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④ increase in time accuracy of the grinding wheel and the rotating parts so as to eliminate cracks caused by grinding possible.
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These are the bearings on the causes and preventive measures of cracks in the grinding process analysis reports, I hope you can help look after. Luoyang permanent crown diameter slewing bearings are mainly production of 50-9800mm / wheel bearings and various high-precision rotary bearing, a large thrust ball bearings, bearings and other non-standard shaped products, precision covering P0, P6, P5, P4 four grades, the product type comprises a single row four-point contact ball structure, cross-cylindrical roller structure, a triple-row cylindrical roller structure, a double structure volleyball, the ball joint structure of columns, thin-walled flange structure, large thrust ball structure. Welcome to the needs of friends to call detailed consultation.