Drying Characteristics of Mongolian Scots Pine (Pinus sylvestris var. mongolica) Square Timber under Different High-Temperature Drying-Set Treatments
Junbo Cheng, Zhengmin Jin, Zhipeng Zhu, Yingchun Cai, Jingyao Zhao*
Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), College of Material Science and Engineering, Northeast Forestry University, Harbin 150040, China
* Corresponding Author: Jingyao Zhao. Email: 
Journal of Renewable Materials https://doi.org/10.32604/jrm.2026.02026-0092
Received 14 July 2026; Accepted 18 August 2026; Published online 31 August 2026
Abstract
To investigate the effects of different high-temperature drying-set treatment processes on the drying characteristics of 120 mm thick Scots pine (
Pinus sylvestris var.
mongolica) square timber, six drying schedules were designed. Temperature and moisture content distribution, drying rate, checking behavior, and residual stress variations were measured and analyzed. The results showed that a surface temperature exceeding 100°C during the drying-set stage was essential for promoting effective surface shrinkage and forming a stable drying-set layer. The 105°C treatment failed to achieve this condition, resulting in severe surface checking. In contrast, the 120°C treatment provided suitable conditions for forming a stable drying-set layer. Among the investigated schedules, the schedule with a drying-set temperature of 120°C and a duration of 10 h exhibited the lowest surface-checking area. Although the surface temperature exceeded 100°C under the 135°C treatment, the heating rate of the surface layer increased with treatment duration (reaching a maximum of approximately 12.5°C/h), resulting in an increased temperature difference between the surface and interior layers and an elevated risk of surface checking. After drying, the residual stress of the high-temperature drying-set treated groups was reduced by 72.41%–86.89% compared with the control group. Among the investigated drying schedules, the schedule involving saturated steam softening at 95°C for 12 h followed by drying-set treatment at dry-bulb/wet-bulb temperatures of 120°C/90°C for 10 h exhibited the best overall performance. This schedule reduced the drying cycle to 5.9 d, representing a reduction of 9.23%–52.80% compared with the other schedules. It also produced a residual stress of 0.29%, and a surface checking area of 51.69 mm
2, corresponding to reductions of 56.85%–88.04% relative to other schedules. These findings provide new insights into moisture migration and stress evolution during high-temperature drying-set treatment, supporting the optimization of drying strategies for large-section wood products.
Keywords
Pinus sylvestris var.
mongolica; high-temperature drying set; pretreatment; surface checking; moisture content
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