Factors affecting cracking when steel precision metal processing parts heat treatment and prevention of 45 # steel is a kind of precision machinery processing USES a wide range of materials, in the course of processing, the need for quenching treatment, in the process of quenching, prone to cracking the case, the main reason is precision hardware internal thermal stress and organization stress is produced.
Thermal stress is a result of heating and cooling the parts of the parts caused by temperature difference exists.
Organization stress because of austenite and its transformation product volume, precision hardware parts processing organization change in different time, in quenching process, the two stress often occur at the same time, after the two stress superposition of total stress of large steel instantaneous ultimate strength, precision metal processing parts can produce crack at this time.
So affect precision parts
thermal stress and organization stress and the main factors of the ultimate strength of steel what?
Precision hardware parts structural design: if the shape of the machined part asymmetry, uneven thickness of section, mutated, thin edges and corners, which are likely to cause stress concentration.
Heating speed and temperature, heating speed is too fast to produce larger thermal stress, the heating temperature is too high to cause overheating, make austenitic organization bulky, reduce the ultimate strength of steel, precision metal processing parts at the same time the thermal stress and organization stress increased.
Cooling method and cooling medium, cooling temperature, cooling speed will generate larger thermal stress and organization stress, due to the structure of the workpiece shape design is not easy to change, and the impact is not big, we focus on analyzing from the heat treatment process.
To prevent 45 # steel qualitative precision mechanical parts during quenching cracking methods: 1.
Lower heating temperature: the 780 -
800 oc heating, to prevent overheating and causing cracking.
Precooling quenching method: after parts of precooling to close to the right temperature and quenching, usually adopts 720 - carbon steel
760 oc, this method can reduce the thermal stress, so the general slender, thin precision components has good effect, on its thickness disparity parts, to a certain extent, can also have the effect of preventing cracking.
To choose the appropriate cooling medium, the parts quenching cooling rate should be greater than the critical cooling rate, in order to obtain M group, but excessive cooling speed will produce a great stress, deformation and cracking precision metal processing parts of risk.
The above information is derived from the precision metal processing factory in shenzhen Xavier company, more products please click on the link to see http://www for details.
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