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Analysis of Cracking Failure of NSK Bearing Blocks
Source: Bearing network time: 2013-04-03
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If it is a certain method, a deep compressive stress layer is formed; regarding the corrosion stress, the tensile stress of the workpiece can be offset; the corrosion fatigue damage is greatly reduced; the induction heating is tried as much as possible; when the sensor and the workpiece are touched; Reduced; can now take the resistance dip as an electrical signal; immediately pass the transistor switching circuit to intercept the induction heating power supply; together announce the alarm signal; after the fault is swept; then send the electric resonance to the workpiece induction heating. The dimensional accuracy and surface quality of the imported bearing; try to avoid when assembling Dust ingress. Frequency induction heating quenching hardening layer depth of 3 7 mm Hardened layer depth ≥ 2. 3mm West 110mm and 120ram hardened layer depth are ≥ 4mm ≥ 6ram found in production; several drive axle half shaft at 120mm The teeth are arranged unevenly; the hardness of the insert is low; the reinforcement effect is not achieved; on the contrary, the strength and hardness of the base are lower; and the wear resistance is poor; the overall strength of the bucket teeth is lacking; the wear resistance is poor. Under the harsh working conditions of the excavator.
There are many sources of fracture cracks; most of them originate from the inner surface of the NSK bearing water jacket; the crack source region presents black corrosives; but the fatigue arc traces are not clearly defined.
Scanning electron microscopy survey of the fracture site; the characteristics are as follows:
1 Expand the multiple survey; visible micro-regions show many fan-shaped tricks.
2 There is a fatigue arc at the front end of the crack and there are many corrosion pits.
3 Different views of the fan-shaped tricks are different; the fan-shaped tricks are composed of different plane cracks. The crack extension area is investigated at high magnification; the typical fatigue crack is found, and the crack source is low-scan; the beach trick can be found around the crack. Source; crack source area has many corrosion pits scattered; some corrosion pits are connected into a line;
4 The highest stress is accepted; the water jacket and the hot sleeve of the cylinder sleeve are touched. The stress at B is small. The NSK bearing water jacket operation mainly accepts three kinds of stress effects: explosion stress, installation stress and thermal stress. Maximum stress of water jacket It is a hoop stress; its value is about 128 MPa. It is a random anomaly in the oil-containing inlet. The abnormal defects of the workpiece appearing on the fire often seriously affect the surface quality and product function of the workpiece; even the formation of the workpiece is unqualified and invalid; This is especially true for fine or critical workpiece surfaces with high surface quality requirements.
5 observations during production; induction heating; the ignition of workpieces and sensors is often not a touch; the noise of imported bearings is very sensitive. Therefore, in order to adhere to the oil-slip work of imported bearings; usually use high-reliability sintered bronze oily NSK Bearings; and some methods should be adopted; for example, proper control of the sintering conditions; the arrangement of the alloy is a single phase a; the anti-corrosion process can be selected, and the
Other method is to apply compressive stress on the surface of the workpiece; Accepted tensile stress.
It can be seen that the cooperation between NSK bearing water jacket and cylinder liner; A is the water jacket and cylinder sleeve hot rib touch; the highest stress is accepted; and the stress at B is small. The NSK bearing water jacket operation mainly accepts the explosion stress, The three stress effects of installation stress and thermal stress. The maximum stress of the water jacket is hoop stress; its value is about 128 MPa; the maximum stress of the inner wall of the water jacket is about 98 MPa.
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