Effect of air heat treatment on the shrinkage and surface roughness of six Korean oak woods

The effect of air heat treatment was evaluated relative to the shrinkage and surface roughness of six Korean oak woods: Quercus serrata (Qs), Quercus mongolica (Qm), Quercus acutissima (Qac), Quercus aliena (Qal), Quercus dentata (Qd), and Quercus variabilis (Qv). The properties were examined using untreated and treated flat-sawn heartwood boards at 160, 180, 200, and 220 °C for 2 h. The shrinkage in the radial and tangential directions increased with increasing temperature, whereas the anisotropy coefficients decreased from 160 to 200 °C and increased at 220 °C. At all temperatures, Qm exhibited the smallest shrinkage, and Qv showed the highest shrinkage in the radial and tangential directions. The surface roughness of the oak wood decreased with increasing temperature, showing the highest average roughness (Ra) value in Qs at all temperatures. Qm and Qac showed the smallest Ra values at 160 to 200 °C and 220 °C, respectively. Qm showed the highest change in Ra value at 160 and 200 °C, while Qv had the highest change at 180 and 220 °C. In contrast, Qal consistently exhibited the smallest change in Ra at all temperatures.