1992 Volume 32 Issue 5 Pages 593-599
The objective of this study was to establish the technology for measuring the surface temperature of the metal pool in Electron Beam Melting (EBM) of titanium and titanium alloys.
The experiments were carried out using the 80 kW×2 EB furnace. Under various pressures in the chamber, the temperature of titanium or titanium alloy pools were measured by a two color pyrometer, with two wave lengths for the measurements were 500 and 580 nm; and by an optical spectrometer with range from 400 to 800 nm. Tungsten-Rhenium (5/26) thermocouples were used for the correction of the optically measured temperature by directly immersion in the metal pool.
Results obtained were as follows;
(1) Only when the pressure in the chamber was below 0.04 Pa, the two color pyrometer could be used for the temperature measurements of titanium pool.
(2) In case of pressure above 0.04 Pa, the reading of the two color pyrometer was disturbed by emitted light especially with the spectral-line of 500 nm in titanium vapor. In these cases, the temperature should be computed from the base line of the visible light spectrum.
(3) The relationship between the surface temperature of the titanium alloy pool in the hearth and EB irradiation power could be well expressed by a simple heat balance model.
