Study on Heat Affected Layer in Laser Drilling

This study was conducted on the structure of the heat affected layer formed by YAG laser. The mechanism for the formation of this layer with a thin plate of austenite structure stainless steel has not yet been adequately clarified. The conclusions obtained under the conditions used are summarized as follows : (1) The growth structure of a micro columnar crystal can be explained on the basis of a formation model of the heat affected layer visually conceived of from the experimental results. (2) A micro columnar crystal is formed independently of the variation for a laser pulse length. (3) This crystal is formed by quick cooling solidification. (4) The heat affected layer and micro columnar crystal on the surface skin layer clearly demonstrate the relationship of temperature to stress, arising from heat conduction.