NSK bearing parts processing cooling technology

Repair parts in the process of heat treatment must be normalized processing, the structure of the required mechanical performance index components should be carried out after normalizing conditioning can meet the requirements of mechanical properties. Medium and high alloy steel and large forgings after normalizing must plus high temperature tempering to eliminate internal stress is generated when the fire. Some steel alloy forging parts are produced when the martensitic transformation, the formation of hard tissues. In order to eliminate this kind of undesirable tissue taken normalizing, higher than the normal normalizing temperature 20 ℃ or so for normalizing heat insulation. More than 1 NSK bearing parts machining demand is high, production process inevitably. General bearing production need 20 ~ 40 working procedure, much more than 70. 2 processing bearing parts of the surface of the work are rotary forming surface, suitable for molding in processing. Such as forged ring groove rolling mill and car, is the forming tool or prevent plate processing. Most of the surface to 3 NSK bearings precision machining parts after grinding, grinding size and geometric accuracy are in microns, especially ring raceway and rolling body of higher precision, superfinishing or grinding processing. 1) Annealing cooling way: when steel annealing, generally USES along with the furnace cooled to 600 ~ 550 ℃ below came empty cold again. 2) Normalizing cooling method: when the steel is a fire, generally USES in cooling in the air. 3) Quenching cooling way: steel quenching, the steel in the supercooled austenite (the most volatile range 650～550℃） Cooling rate should be greater than the critical cooling rate, thus ensure the workpiece does not change for the pearl shape organizations; And cooling velocity near the Ms point should be as low as possible, so as to reduce the quenching stress, reduce the workpiece deformation and cracking. As a result, quenching, besides should choose suitable quenching cooling medium, still should improve quenching method. For simple shape workpiece, often using the simple single liquid quenching method, such as carbon steel liquid water or salt water as cooling medium, alloy steel used oil as cooling medium. 4) Tempering cooling method: carbon steel tempering, commonly used in air cooling. Normalizing process is heat the steel to Ac3 ( Or Acm) More than 30 ~ 50 ℃, the heat preservation after the right time, in the stillness of the air cooling heat treatment process. The steel heating to 100 ~ 150 ℃ above Ac3 normalizing is called high temperature normalizing. For medium and low carbon steel casting, forging, the main purpose of normalizing is refined. After compared with annealing, normalizing pearlite lamella is fine, ferrite grain size is small, thus higher strength and hardness. Low carbon steel because of the low hardness after annealing, produce the phenomenon that stick knife when cutting, cutting performance is poor, improve hardness by normalizing, can improve the cutting performance, some carbon structural steel parts in normalizing can substitute for conditioning, simplify the heat treatment process.