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/*728*90 created on 2018/5/16*/ var cpro_id = "u3440131"; Home>Bearing knowledge>The determination of the cold treatment of the ferrule Determination of cold processing and normalizing processing method of ferrule
Ferrule cold treatment 1. The effect of cold treatment is that the precision bearing has higher requirements for dimensional stability. After the ring is quenched (especially after stage quenching), the internal arrangement still retains more retained austenite; this residual Austrian. . /*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';
Ferrule cold treatment
1. The effect of cold treatment is that the precision bearing has higher requirements for dimensional stability. After the ring is quenched (especially after stage quenching), the internal arrangement still retains more retained austenite; this residual austenite is an unstable arrangement; And the use of the bearing process; will continue to change; then change the accuracy of the bearing. For this purpose, the cold treatment process is selected; it can reduce the remaining austenite in the arrangement; slightly improve the hardness of the part.
2. Cold treatment process after quenching at room temperature: after quenching; must be allowed to cool the ferrule surface to room temperature and then cold treatment; otherwise simply cracking; cold to room temperature immediately after cold treatment (usually not exceed 30min); otherwise discontinuous austenite orientation The transformation of martensite.
Cold treatment temperature: The temperature of cold treatment is mainly based on the martensite transformation stop temperature Mf of steel; the other is to consider the influence of cold treatment on mechanical properties and processability.
About GCr15 steel; cold treatment is selected at -70 °C, when the ferrule or equipment with low precision requirement is restrained; the cold treatment temperature can be -40 ~ -70 °C, ultra-fine bearing; can be -70 °C ~ -80 °C Cold treatment is carried out. The temperature of the cold affects the bearing impact fatigue and the touch life.
Cold treatment insulation: Although many martensite transformations are completed at a cold to a certain temperature A; but in order to make a batch of ferrules and the heart evenly reach the cold treatment temperature; the demand must be the insulation time; usually 1 to 1 5h.
Tempering after cold treatment: After the ferrule is cold treated, it is placed in the air. The temperature is slowly raised to room temperature and then tempered in time. The temperature rise cannot be too fast; otherwise, the crack is briefly cracked and the tempering is timely; otherwise, the residual residual stress inside the ferrule Will cause the ferrule to crack; usually does not exceed 2h.
Normalizing
1. The intention of normalizing (1) Adjusting the hardness of steel: Some bearing products have good anti-tempering performance; they must have higher hardness after quenching after 200~250 °C; optional annealing after normalizing; Pearlite arrangement.
(2) Elimination of reticulated carbides and line-like arrangements: when the steel forging temperature is too high and the cooling is too slow, the carbides are separated along the austenite to separate the reticulated carbides, when the final forging temperature of the steel is too low; The grain is elongated along the direction of deformation and presents a line-like arrangement. This arrangement cannot be completely eliminated during the annealing process; then the impact toughness of the bearing's fatigue strength is lowered.
(3) Non-conforming products for rework annealing: coarse pearlite which is generated by annealing overheating; it is necessary to pass normalizing; then the second annealing is performed.
2. The normalizing process normalizing process is mainly to select the heating temperature and cooling method; it depends on the intention of normalizing, the shape of the carbide in the fiber arrangement before the normalizing, and the shape and wall thickness of the ferrule. The normalizing heat preservation time is usually 30 to 50 minutes. The cooling rate should not be less than 50 ° C / min; avoid the separation of the carbide net. About thin-walled parts; diffuse cooling or blow-drying, for thicker parts; spray, oil-cooled or emulsion cooling; oil-cooled It is usually taken out to the outside of the part at 300 °C; after the oil is incinerated, it is placed in the oil again and cooled to a temperature of not lower than 250 °C. Immediately after normalizing, it should be tempered or firstly subjected to stress relief at 400-450 °C. Fire; avoid cracks. The emulsion is usually controlled at 70 ~ 100 ° C during cooling; the circulating cooling method is selected; the workpiece is cooled to 550 ~ 650 ° C and then taken out of air cooling.
Processing method
1. Features of the gathering process (1) Can complete most or all turning operations in one clamping cycle; reduce the positioning error of the ferrule clamping and the positioning time of the clamping positioning; improve the orientation and scale precision between the outer surfaces of the ferrule; The yield is obtained. If the medium and small ferrules produced in batches can be driven 2 to 3 at a time on a multi-axis active lathe.
(2) Shortened the process flow; reduced the central storage, loading and unloading, and transportation links; facilitated the production and processing, and reduced the amount of machine tools and equipment.
(3) Conducive to the completion of the initiative and mass production; shortened the production cycle; reduced production costs.
However, there is a high demand for process equipment such as lathes, knives, jigs and auxiliary materials, and workpiece blanks. For example, there is less demand for blanks and higher precision; the quality of appearance such as metallographic arrangement and hardness is also more severe. The demand lathe has greater power, rigidity and higher processing precision and degree of automation; often use multi-blade, multi-step, multi-station multi-axis semi-active machine and active machine tool; usually suitable for mass production Multi-axis active machine tools; multi-blade semi-active lathes should be used for medium and small batches and different types of processing. The variety and quantity of process equipment are large; the speciality is strong, the replacement type is troublesome; the adjustment is difficult and time-consuming; the skill level of workers Higher; reasonable production arrangements for processing.
2. Features of the smashing process method (1) Suitable for medium and small batches and single piece production. Briefly arranged production; lathes, fixtures are simple and economical; easy to replace bearing types; low cost. If single machine is connected to the active line; .
(2) It can be processed with high-efficiency special lathe with good rigidity and high power; it is easy to select the best process parameters; it can be cut by high-speed large-passing cutter; the processing power is improved.
(3) It can complete active loading and unloading, active cutting and active measurement for a single machine; the machine tool is simple operation; the demand for workers is not high.
(4) The demand for ferrule blanks is not high; blanks of various methods, sizes, and precision batches can be used.
However, there are many processes in the “disintegration process†and the process route is long; the processing time and the storage, transportation, and loading and unloading between the processes are long; one ferrule needs to be multi-machine, multi-process, repeated clamping positioning, multi-person operation and viewing; Large positioning error and poor processing accuracy.
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Source: China Bearing Network Time: 2014-02-09