Precision casting characteristics of induction melting equipment
In precision casting processes, especially in "equal" processes, metal temperature is a dominant factor and, therefore, has a direct impact on many quality characteristics. If the measurement and control are not proper, the difference in metal temperature will affect the finished casting size, grain size, porosity (surface and interior), mechanical properties, product quality (ie, the tendency of hot tear), and the fullness of the thin-walled portion. Have an impact.
Therefore, improved metal temperature measurement and control will improve quality and productivity, reduce maintenance and labor costs, and reduce testing costs and liability costs. Difficulty in temperature measurement
Precision casting, especially precision casting using inductive melting equipment, typically uses some type of non-contact infrared radiant thermocouple or pyrometer as the primary or secondary means of metal temperature measurement. People using conventional pyrometers may not be aware of the potential sources of error in their measurements, but simply pay attention to the "precision" technical conditions of the instrument and are often misled. These precision technical conditions are only ideal targets in a laboratory environment. Some situations in the real world can lead to surprisingly high measurement error values, including but not limited to the following:
1. Unknown/changing emissivity—multiple alloys, perturbation effects, temperature and wavelength dependence, and compositional changes during processing, all of which contribute to the unpredictability of emissivity.
2. Steam Emission: For high pressure melting (close to and above atmospheric pressure), gases that escape from the bath or crucible increase or decrease heat radiation, thus causing errors. 3. Observing hole obstacles: For most instruments, any weakening of the signal will cause a drop in the temperature indication value; the dirt on the observation window affects the accuracy of most pyrometers. 4. Observe the glazing material: not all glasses have the same transmission properties; some are “grey”, while others have a transmittance that varies with wavelength. This can cause conventional pyrometers to fail.
5. Verification: The industry standard is verified once a year. However, the drift and failure of the instrument have its own schedule. It is ideal to verify all the optical components used in the factory (observation glass or sight glass).
6. Instrument calibration: Aiming through the lens requires accurate overlap of the two optical paths, which affects all grades of conventional pyrometers.