STUDY ON THE HYDROTHERMAL TREATMENT OF KILN-DRIED TIMBER OF RED ALDER

This study used red alder (Alnus rubra f. pinnatisecta) and applied humidity control during storage to shorten the health cycle and enhance preservation effects. Orthogonal testing was conducted to assess the impact of humidity control on drying quality and identify optimal conditions. The results showed that: 1) Post-humidity control, most materials exhibited high surface and low core moisture distribution. Surface moisture difference before and after treatment was largest and negatively correlated with moisture increase. Higher temperatures reduced differences at the same treatment duration. 2) Reasonable humidity control significantly improved drying quality: surface moisture remained stable, elastic and mechanical adsorption creep strains decreased, and residual stress was reduced by up to 59.5% after 7 days of humidity and curing compared to room temperature curing. 3) Moisture treatment initially reduced residual stress significantly then rebounded slightly, with stress elimination efficiency generally higher than room temperature. This indicates that humidity control shortens wood storage and curing cycles. 4) Orthogonal test results identified optimal humidity control conditions as 70°C, 85% relative humidity, and 48 h treatment.