Imported bearing failure checking method of cooling medium and quenching

According to the formation mechanism of grinding badness layer of bearings working surface, the main factors influencing the grinding metamorphic layer is a function of grinding and grinding force. Here we analyse about bearing failure reason. 1. Bearing grinding heat in bearing grinding, grinding wheel and workpiece contact zone, consume large amounts of energy, produced a large number of grinding heat, local transient high temperature caused by grinding area. On the basis of the theory of linear motion heat source heat transfer formula derivation, calculation or by the method of infrared ray and measured experiment under the condition of instantaneous temperature thermocouple method, can be found in 0. 1 to 0. The grinding area within 001 ms instantaneous temperature up to 1000 ~ 1500 ℃. The instantaneous high temperature, which would have made certain depth on the surface of the work surface to produce high temperature oxidation, amorphous group, high temperature tempering, secondary hardening, and even burn cracking and other changes. ( 1) Surface under the action of transient high temperature oxide layer of the surface of the steel and the oxygen in the air, rises into extremely thin ( 20～30nm） The iron oxide thin layer. It is worth noting that the oxide layer thickness and surface grinding metamorphic layer is the total thickness test results in corresponding relation. This shows that the thickness of oxide layer, is directly related to the grinding process is an important symbol of grinding quality. ( 2) Amorphous layer organization grinding the instantaneous high temperature makes the workpiece surface reach a molten state, molten metal molecular flow is evenly coated to the work surface, and the matrix metal cooling at breakneck speed, formed a very thin layer of amorphous tissue layers. It has high hardness and toughness, but it is only about 10 nm, it is easy to be removed in the precision grinding processing. ( 3) High temperature tempering instantaneous high temperature can make the surface layer of grinding zone certain depth ( 10 ~ 100海里) Be heated to a temperature higher than the workpiece temperature tempering heat. In the absence of austenitizing temperature reached, with the improvement of heated temperature, the surface will produce one by one and heating temperature corresponding to the organization transformation, or high temperature tempering tempering hardness. The higher the heating temperature and hardness of the decline is more severe. ( 4) Transient high temperature quenching layer when the grinding area on the second floor heat the workpiece surface layer to the austenitizing temperature ( Ac1） Above, the layer of austenitizing group in the subsequent cooling process, the quenching into martensite structure anew. Where the secondary hardening burns of workpiece, the second time hardening layer must be under very low temperature tempering hardness layer. ( 5) Grinding crack two quenching burns will make workpiece surface layer stress changes. Secondary hardening zone is in compression state, the high temperature materials back to the fire area underneath there are the largest tensile stress, this is the place where the most likely to occur crack core. Crack is the most easily spread along the original austenite grain boundary. Serious burns can lead to crack of the grinding surface ( Formed a crack) Artifacts caused by scrapping. In the process of bearing use, vibration, noise, improper use of lubricant will cause serious damage to the bearing, directly affect the service life of the bearing, in order to better use bearing, improve production efficiency it is necessary for us to understand some of the improper way of using the bearing harm and some simple bearing maintenance. Different bearing parts of the composition, shape, design, size, the mechanical performance requirements are different, the quenching method is different, generally speaking each bearing steel all have fixed C curve, and decided the bearing quenching cooling medium of the organization and mechanical properties is not standard, so do focus on analysis of these factors will be specific, in the actual bearing parts in the production process of the production of heat treatment defect, and cooling the bearing medium are directly related. In bearing heat treatment furnace heated to completely after refining, in order to strictly technical parameters requirements, should be treated after quenching, after cooling the bearing to get martensite structure, bearing of the cooling rate must be greater than the critical cooling rate, speed too fast, but the cold causes artifacts volume shrinkage and organizational change drastically, cause a lot of internal stress. So in obtain martensitic conditions 'F', so it is important to note that the cooling speed, so as to get qualified martensite. Choose appropriate quenchant is particularly important, it determines the microstructure and mechanical properties of bearing parts after quenching, quenching medium usually has a solid, liquid and gas are three, according to the bearing when quenching medium changes of state can be divided into changes of state and change of state class. Produced in the ease of selection of quenching medium is one of the most important, it determines the bearing quenching after the overall performance of an organization and, in general the quenching medium of gas and liquid, and solid, the comparison of gas with relatively less, and in accordance with changes of the quenching time and can be divided into biological state change and no change of state of the two classes.