Study on the Measurement of Physical Properties in the Metal Powder for Rapid Prototyping

-Proposal of the Measurement of Thermal Conductivity and Absorption of Laser Beam-

Abstract

In this paper, a simple method for the measurement of thermal conductivity and absorption of laser beam in fine metal powder for rapid prototyping is proposed. When the heating time of the metal powder t is sufficiently short in comparison with the time until the metal powder reaches its maximum temperature T (t/T<0.1), and the measurement depth from a surface Z is longer than the diameter of the heat source a (Z/a>1.23), it is shown that the thermal conductivity of a metal powder can be precisely calculated by measuring the time that the temperature takes to reach its maximum value. As work materials, chromium molybdenum steel powder (SCM) and copper powder, whose diameters are 10μm, 20μm and 30μm, are used.
As a result of measuring the thermal conductivity and the absorption of laser beam in various metal powders, the thermal conductivity of a metal powder is quite small compared with that of the metal, and the materials, the shapes and the diameter of a metal powder have little influence on thermal conductivity. The absorption at the surface of a metal powder is larger than that of the metal, and there is little difference among the materials.