The use of plasma nitriding skills in crankshaft production (1)
2019-09-03 14:05:08
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The use of plasma nitriding skills in crankshaft production (1)
Source: China Bearing Network Time: 2014-03-06
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First, the theoretical scale of crankshaft ion soft nitriding process parameters in terms of crankshaft plasma nitriding skills; most manufacturers have selected ion soft nitriding skills; the formulation of process parameters should generally follow the following criteria:
1. Selective scale nitriding temperature plasma nitriding is a chemical thermal treatment method that uses nitrogen glow discharge to introduce nitrogen into the metal surface to form FeN. In the iron-nitrogen phase diagram; 580 °C is the allotropic transformation point; Below 580 ° C it is arranged as alpha iron; above 580 ° C its arrangement is converted to gamma iron. Usually; the progress of the treatment temperature contributes to the composition of the nitride and to obtain a deeper layer (at the same time); this is because The diffusion coefficient is proportional to the exponential change of temperature. However, because the diffusion coefficient of nitrogen in γ-iron is only 1/4 of that of α-iron; when the treatment temperature is higher than 580°C; the increase of the permeable layer is slowed down; thus; Ion nitriding operating temperature scale is 520 ° C to 580 ° C.
2. The selection of soft nitriding temperature is about carbon steel or cast iron or low alloy steel; we often use ion soft nitriding (low temperature carbon, nitrogen osmosis) skills. Many theories indicate: hardness and permeability of nitrided layer There is an extreme relationship between time and concentration. Usually the ratio of ammonia to acetone is 10:1; the temperature is between 560 ° C and 580 ° C; the time is between 3 and 4 hours; the best hardness and permeability are obtained. In the ternary phase diagram of nitrogen and carbon; the isomorphic transformation point is slightly reduced; its isothermal section is reduced to 575 ° C. When the temperature is higher than 575 ° C; the temperature rises; the permeability and hardness decrease rapidly; At 600 ° C; the layer is completely gone. In order to have better carbon and nitrogen osmosis; the operating temperature of ion nitrocarburizing is usually 540 ° C to 580 ° C.
3. The influence of other factors on the process parameters The above is the process temperature control scale based on the phase diagram; in fact, it is subject to other factors. 1 is to ensure the induction of the function of the part; usually before the ion nitriding needs to be advanced Heat treatment; the upper limit temperature of ion nitriding should not exceed the pre-heat treatment temperature, 2 depending on the degree of deformation of the part; select the appropriate heating rate and should be properly homogenized in the pre-heat treatment. In summary: ion soft nitriding The temperature control scale should be above 540 °C; below the aging temperature; and according to the specific needs of the parts; select the appropriate heating rate.
Second, the crankshaft ion nitriding process is currently; the typical materials used for domestic production of crankshafts are ductile iron and 42CrMoTi.
Similar to the disposal of other nitrided parts; the ion nitriding process of the crankshaft is usually carried out by blowing, squeezing, squeezing and blowing for 4 periods; including the furnace; roughly taking 18 hours. Different manufacturers are in the ion nitrogen The process is slightly different.
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