Bearing collar after heat treatment deformation of the situation can be roughly divided into three types: the first kind is diameter changes (Vpe), the second average diameter changes (Vdmp), the third class for flatness changes (Ape), these three categories of deformation often overlapping, of which the most easy generation diameter change, and change large amount, so to control deformation quenching, main is to try to reduce the diameter of the collar of change.
A collar, the deformation of quenching factors
A, bearing steel structure defects and annealing after the original cause the organization of uneven distribution of carbide size, will lead to quenching deformation.
B, quenching heat stress and organization when the greater the stress, the greater the quenching deformation. The thermal stress and organizational force includes: the heating temperature, heating speed and uniformity, the cooling speed and uniformity, cooling medium temperature, etc.
C, ring throwing, car process residual stress size, and the diameter of the car after processing by the size of the change, and hardened to the quantity of the change, and in the direction of the basic agreement.
Second, reduce the deformation of quenching collar measures
A, strictly control the cooling speed, improve the quality of annealing. Ball annealing cooling speed size, directly affecting the carbide shapes, sizes and dispersion, thereby affecting the quenching and tempering technology formulating, diameter changes quantity, and eventually mechanics performance. So in the correct formulation annealing process at the same time, the cooling speed strictly control in 10 ~ 25 ℃ / h, for the heat treatment to make organization.
B, strict KongZhiChe processing contractor changes, from table 2-63 can see, after turning the diameter of the change and quenching deformation closely related. The greater the amount car machining diameter changes, the hardening of large diameter changes also about, and in the direction of the basic to remain consistent. So to control the diameter of the quench heating changes, the first to strictly control lathe work process diameter changes.
C, meet each other in hardness and organization premise, quench heating try to take lower limit temperature, the temperature control of the three points appropriate reduction furnace caterpillar area first temperature, extend the heating time to slow down the heating speed, ensure that contractor is heated evenly, reduce quenching diameter changes.
Table 2-63 Turner change the volume and quenching variations under relationship
Turner diameter variations under percent of pass / % hardened diameter variations under/mm average diameter variations under/mm diameter changes more than the required rate / %
% 980.08 ~ 0.350.134.23
750.08 ~ 0.480.2222.70
500.08 ~ 0.560.3045.00

Table 2-64 the third district of the influence of temperature, the front-runners life
The third area / ℃ temperature, the serial number of the damage ratio L50 life rings / %
1790 ~ 800112347.5
2805 ~ 81593657.00
3815 ~ 82556972.00
Table 2-65 have temperature changes of quenching quantity relationship
The oil temperature / ℃ after quenching diameter variations under/mm ultra rate differential %
450.03 ~ 0.358.3
600.03 ~ 0.282.5
750.03 ~ 0.191.2
D, take the cold hardening, already tracked furnace area first (heating area), the second area (heat preservation zone) take the normal quenching temperature, just the third district furnace temperature will drop to 790 ~ 800 ℃, and then the material into the oil quenching. Ensure that contractor in the furnace, or so heated more even, not only reduce the collar diameter change, but also improve the bearing life and other mechanical properties (see table 2-64).
E, an appropriate increase of oil quenching temperature, be helpful for control of general yi deformation light series, and light series rings quenching change quantity, quenching oil temperature control in 60 ~ 90 ℃ between advisable. Table 2-65 for 7309/01 of the measurement results, see hot to reduce oil quenching rings diameter changes have obvious effect. To ensure that the size of the bearing stability, heat oil hardened rings should be after a cold water to rinse rust, to try to reduce the front-runners austenite content.




Other News:
Precision bearing installed
SKF announces change of the total number of votes in AB SKF 31 August 2010
Reduce the deformation of quenching collar measures
Bearing steel casting heat treatment
Use common super precision grinding machine processing, low roughness parts