黑木相思木材干燥特性及干燥工艺制定

  目的  为获得黑木相思Acacia melanoxylon木材的干燥特性，编制合理干燥基准，从而促进其实际开发和利用。  方法  采用百度试验法研究黑木相思木材的干燥特性，参照百度试验干燥缺陷等级拟定木材干燥初终期条件，依据锯材干燥质量检测结果对黑木相思锯材常规干燥工艺进行系统优化试验，并制定25 mm厚黑木相思锯材的干燥基准。  结果  黑木相思木材的干燥缺陷主要为初期开裂和扭曲变形，其次为截面变形，无内裂产生。从干燥速度看，黑木相思属于中等易干材。木材含水率15%时的气干密度为0.620 g·cm?3，属于中等范畴。采用优化制定的干燥基准对25 mm厚黑木相思锯材进行常规干燥后，木材含水率从110.40%干至8.42%，干燥周期为268.0 h (11.2 d)，整个干燥过程中干燥速率比较稳定，平均为0.38%·h?1。  结论  黑木相思干燥锯材的平均最终含水率、干燥均匀度、厚度上含水率偏差、残余应力以及可见干燥缺陷方面的指标均达到锯材干燥质量二级要求。本研究制定的黑木相思锯材干燥工艺可为实际干燥生产过程提供科学依据。图2表6参25

Drying characteristics and drying schedule developed of Acacia melanoxylon wood

  Objective  In order to provide the technical support for promoting the practical development and utilization of blackwood (Acacia melanoxylon) planted in China, its drying characteristics were investigated, and further its suitable drying schedule was drawn up.  Method  The drying characteristics of blackwood were determined using the 100 ℃ test method. The kiln drying experiments were conducted on the lumber of 25 mm in thickness to develop a suitable drying technique.  Result  The main drying defects were initial cracking and twist deformation. The cross-sectional deformation degree was light, and there were no internal cracks. The blackwood was moderately easy to dry with the drying speed. The blackwood was a medium density hardwood with the air-dry density at 15% moisture content of 0.620 g·cm?3. Applying the proposed drying technique, the drying period of lumber was 268.0 h (11.2 d) as the moisture content of wood decreased from 110.40% to 8.42%. The drying rate remained relatively constant with an average value of 0.38%·h?1 during the whole process.  Conclusion  The final average moisture content, drying evenness, moisture content deviation in thickness, residual drying stress, and drying defects of the dried lumber all come to the requirements of the second grade drying quality of sawn timber in the Chinese National Standard. The findings provide the scientific basis for the actual production of kiln drying to ensure drying quality of the blackwood. Ch, 2 fig. 6 tab. 25 ref.]