LIAOCHENG SUNSPEED BEARING INDUSTRIAL CO.,LTD
BEARING PRODUCTION PROCESS
Forging is a kind of processing method which uses forging machine to exert pressure on metal bad material to produce plastic deformation in order to obtain forgings with certain mechanical properties, shape and size.
The forging of bearing rings can be divided into three stages
1. Material preparation: cut raw materials into sections according to the required weight
2. Forging forming: the material section is heated, and then forged on the forging equipment to make it a rough embryo with the shape and size meeting the requirements
3. Post forging treatment: inspect forgings, remove scrap, repair products, heat treatment and surface cleaning after forging.
The forging deformation should conform to the law of shear stress, the law of minimum resistance, the law of constant volume and the law of elastic deformation in plastic deformation
Forging can improve the internal structure of steel, improve the strength, plasticity, impact toughness and other mechanical properties of steel
Lathe processing is a part of mechanical processing, there are two main processing forms: one is to fix the turning tool and process the unformed workpiece in rotation; The other is to fix the workpiece, through the high-speed rotation of the workpiece, the horizontal and vertical movement of the turning tool (tool holder) for precision machining
Martensite quenching and tempering of high carbon chromium bearing steel is as follows: the bearing parts are heated to 830 ~ 860 ℃ for heat preservation, then quenched in oil, and then tempered at low temperature. The mechanical function after quenching and tempering depends not only on the initial arrangement before quenching and quenching skills, but also on the tempering temperature and time to a great extent. With the increase of tempering temperature and holding time, the hardness decreases and the strength and endurance advance. Suitable tempering skills can be selected according to the operation requirements of parts: GCr15 steel bearing parts: 150 ~ 180 ℃; GCr15SiMn steel bearing parts: 170 ~ 190 ℃. For parts with special requirements, higher tempering temperature is selected to meet the service temperature of forward bearing, cold treatment at - 50 ~ - 78 ℃ between quenching and tempering is carried out to improve the dimensional stability of forward bearing, or martensite step quenching is carried out to stabilize the remaining austenite, so as to achieve high dimensional stability and high resistance.
The heat treatment process is isothermal quenching, the isothermal temperature is 200 ℃, 250 ℃ and 300 ℃ respectively, and the isothermal quenching time is the time until the bainite transformation stops. The content of bainitic ferrite, the content of carbon in bainitic ferrite, the thickness of microstructure and dislocation density are different at three different temperatures
① Due to the gradual increase of strength of austenite at lower temperature and the change of free energy during transformation, the bainitic ferrite lath is only 30-65nm thick; ② Bainitic ferrite contains up to 0.3% carbon. The stress strength, tensile strength, fracture toughness and elongation change with temperature. During the test, the plastic deformation is evenly distributed on the scale of the tensile specimen, and there is no necking phenomenon. The results show that the bainite structure has very good properties. The stress strength is higher than 1.2gpa, and the tensile strength is 1.77 ~ 2.2GPa. With the increase of strength, the fracture toughness and elongation decrease.
There are two reasons for the good mechanical properties of the microstructure: 1) the thickness of bainite ferrite lath reaches nanometer level, which greatly improves the strength of the sample; ② In bainitic steel, carbon content is closely related to mechanical properties.
Due to the movement of C atoms in the transformation process, C atoms accumulate at the position of bainitic ferrite dislocation, which affects the dislocation density of the structure, and the dislocation density is another mechanism for the enhancement of the properties of the structure. Moreover, dislocation lines, Fe lattice strength and solute atoms' hindrance to dislocation movement also promote the enhancement of microstructure and properties.
Centerless grinding machine is a kind of grinding machine which does not need to use the axis positioning of the workpiece. It is mainly composed of grinding wheel, adjusting wheel and workpiece support. The grinding wheel actually serves as the grinding work. The adjusting wheel controls the rotation of the workpiece and the feed speed of the workpiece. The workpiece support supports the workpiece during grinding, There are several ways to fit these three parts, except stopping grinding, which are the same in principle.
The end face grinder is a high-precision end face processing equipment with high-strength mechanical structure and stable precision.
High precision bearing ensures the rigidity and accuracy of the machine tool.
It is generally divided into two steps: grinding the non reference end first, and then grinding the reference end. The purpose is to ensure the position of the raceway relative to the reference end
Accuracy. Vertical shaft surface grinding is carried out by grinding wheel end face. The grinding force is small, and most of the abrasive grains are below the line contact
Poor grinding condition of high efficiency cutting force. Therefore, even if each abrasive has a sharp edge, the grinding efficiency is still very low, even worse
As for the workpiece that can not be grinded, the so-called "fake" phenomenon appears. In practice, it can be seen that the main part of vertical shaft grinding wheel is in the
The circumferences of the outer circle on the cutting depth and the working end faces close to the circumferences. That is to say, the working face of the vertical axis grinding wheel is only close to the surface
The abrasive grains on the peripheral end face of the grinding wheel play a major cutting role, while the inner peripheral end face of the grinding wheel only plays a friction role on the workpiece.
In this way, in addition to the above phenomenon, the heating value of the cutting area is increased and the coolant is blocked, resulting in the failure of machining
The surface of the workpiece was burned. The existence of the friction surface also makes it difficult to discharge the loose sand particles, so as to scratch the polished surface
Small pressure is exerted on the workpiece with fine-grained abrasive tools (oilstone), and short stroke reciprocating vibration and slow relative vibration are carried out
It is a kind of finishing method to realize micro grinding.
1) Cutting angle
Cutting angle refers to the angle between the cutting speed direction of a point on the machined surface and the actual movement direction of the point
In the process of rough and super machining, the grinding deterioration layer and machining allowance should be removed, and the cutting angle should be large, generally 20 °~ forty
° When finishing and ultra machining, the main purpose is to reduce the surface roughness, and the cutting angle should be small, usually within 5 °~ ten ° Between the two
2) Vibration frequency of oilstone
The vibration frequency of oilstone is the key factor to determine the effect of superfinishing. The vibration frequency is high, and the abrasive particles are harmful to the workpiece
With the increase of cutting times, the cutting effect is strong, otherwise it is weak.
3) Amplitude of oilstone
The larger the amplitude of oilstone is, the stronger the cutting effect is, and the higher the production efficiency is. But the surface quality is not good, which is not conducive to reducing the surface roughness
In rough cutting, the cutting effect should be strong, and the larger amplitude should be chosen, generally 3 ~ 5mm;
In order to reduce the surface roughness, the amplitude should be smaller, generally 1 ~ 3mm.
4) Workpiece speed
When the workpiece speed is high, the cutting angle is small and the cutting effect is weak,
It is beneficial to reduce the surface roughness.
Usually in the cutting stage, the workpiece speed is 15 ~ 20 m / S. in the finishing and super machining, in order to reduce the surface roughness, the workpiece speed should be increased
Generally 25-35 M / s.
5) Oilstone pressure
The greater the pressure of oilstone on the workpiece surface, the greater the cutting amount and the higher the machining efficiency, but it is not conducive to reduce the cutting efficiency
The surface roughness of the workpiece is suitable for the roughing stage; The pressure of oilstone is low, the passivated abrasive particles are not easy to fall off, and the cutting effect is reduced
It can reduce the surface roughness of the workpiece. After machining, the surface quality of the workpiece is good and suitable for machining
It is in the stage of super essence.
Generally, the pressure of rough machining is 0.2 ~ 0.6MPa, and that of finish machining is 0.15 ~ 0.2MPa