大径级火力楠木材干燥特性和干燥工艺研究

采用百度试验法研究木材干燥特性，利用小型木材干燥试验机分别对25 mm和40 mm厚锯材进行常规干燥试验研究锯材干燥工艺基准。结果表明，火力楠木材的百度干燥缺陷程度较轻，初期开裂等级为2，扭曲变形等级为2，截面变形等级为1，内裂等级为1；木材的干燥速度中等，等级为3。木材含水率为15%时的密度为0.679 g·cm^-3，属中等。木材的差异干缩很小，干燥过程产生开裂的趋势较小。采用制定的干燥基准对锯材进行常规干燥，25 mm厚锯材从初含水率87.9%干至终含水率9.1%，干燥用时169.0 h (7.0 d)，平均干燥速率0.47%·h^-1；40 mm厚锯材从87.5%干至8.5%，干燥用时341.0 h (14.2 d)，平均干燥速率0.23%·h^-1。2种厚度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，均达到了国家标准规定的锯材干燥质量二级及以上级别的要求。本研究编制的2种厚度火力楠锯材的干燥基准合理，可为实际木材的干燥生产提供科学依据。

Drying Characteristics and Drying Technology of Large-diameter Michelia macclurei Wood

In order to promote the practical utilization of large-diameter Michelia macclurei wood,its drying characteristics and drying technology were studied.The drying characteristics were determined using the 100℃test method.The drying technologies of 25 mm and 40 mm thick timber were studied by conventional drying experiments on a small-scale wood drying kiln.The results showed that the drying defects of the M.macclurei wood in 100℃test were not serious.The grades of initial cracking,twist deformation,cross-sectional deformation and internal cracking of the wood were 2,2,1,and 1,respectively.The wood was moderately easy to dry with the drying speed grade of 3.The wood was a medium density hardwood with the density at 15%moisture content of 0.679 g·cm^-3.The ratio of tangential shrinkage to radial shrinkage of the wood was very small,indicating its tendency of cracking in drying process would be very small.For conventional drying of 25 mm thick timber,the moisture content decreased from 87.9%to 9.1%with the drying period of 169.0 h(7.0 d)and the average drying rate of 0.47%·h-1.The moisture content decreased from 87.5%to 8.5%with the drying period of 341.0 h(14.2 d)and the average drying rate of 0.23%·h-1 for the timber of 40 mm in thickness.The final average moisture content,drying evenness,moisture content deviation in thickness,residual drying stress,and visible drying defects of the dried 25 mm and 40 mm thick timbers all met the requirements of the second and above grade drying quality of sawn timber in the China National Standard.Thus the proposed drying schedules are reasonable,and these provide technical support for the actual production of kiln drying of the M.macclurei wood to ensure drying quality.