Near‐infrared two‐color pyrometer for determining ignition temperatures of metals and metal alloys

摘要

A two‐color pyrometer has been designed, constructed, and used to measure the ignition temperatures of metals and metal alloys. Cylindrical metal and metal alloy specimens were ignited by a focused cw CO2 laser beam in a cool, static, pure oxygen environment. The pyrometer operates in the near‐infrared at two narrow spectral regions, with a nominal bandwidth of 10 nm centered at 0.9051 and 1.06 μm, and has a temperature range from 1000 to 4000 K. In the present design the temperature of a spot, ∼0.5 mm in diameter, can be recorded with a maximum time resolution of 25 μs and with an accuracy of a few percent. Results of CO2 laser ignition of cylindrical specimens of 6061 aluminum alloy and 302 SS in a pure oxygen environment were obtained from the two‐color pyrometer and were compared with those obtained from a thermocouple placed inside the specimen near the laser‐irradiated surface.