马尾松干燥特性研究

采用百度试验法,在(100±2)℃恒温干燥条件下对马尾松(Pinus massoniana Lamb)试件进行干燥试验,根据干燥过程中马尾松试件的初期开裂、内裂、截面收缩等干燥缺陷制定出马尾松木材的干燥基准。结果表明,马尾松试件的初期开裂等级为1等,内裂等级为1等,截面变形为2等,干燥速度等级为1等,综合特性等级为2等。马尾松的干燥初期温度为70℃,干燥初期干湿球温度差为4～7℃,干燥终期温度为90℃。厚度为25 mm的马尾松板材在强制循环干燥窑内干燥至含水率10%所需的时间为6.75(5)d(括号内为硬基准条件下的干燥时间)。马尾松木材的平均纵向收缩率为0.48%,平均径向收缩率为4.35%,平均弦向收缩率为5.97%。马尾松试件主要缺陷是截面变形,在实际生产过程中要尽量使用硬基准,干燥中、后期适时进行喷蒸处理。

Drying Characteristics of Pinus massoniana

Using 100 ℃ test method,the drying experiment of Pinus massoniana lumber was performed in drying oven at the constant temperature of 100±2℃.The drying schedule of P.massoniana lumber was developed according to the specimens of P.massoniana initial cracking,internal crack,cross-section disfigurement and other drying defects during the drying process.The results showed that the parameter grades of initial cracking,internal crack,cross-section disfigurement,drying speed and composite characteristic of test lumber were 1,1,2,1 and 2,respectivelly.The initial and final drying temperaturre of test lumber was 70 and 90 ℃ and the temperature difference of dry-wet bulb at initial drying stage was 4~7 ℃.The required drying time for P.massoniana panel with thickness of 25 mm dried to 10% in forced circulation drying oven was 6.75(5) days(in Brackets is the drying time under hard benchmark conditions).The average longitudinal shrinkage ratio,radial shrinkage ratio and tangential shrinkage ratio of test lumber were 0.48%,4.35% and 5.97%,respectivelly.The main defects of the specimen of P.massoniana was cross-section disfigurement,harder schedule should be possiblely used in the actual production process;steam injection in time during the medium-and post-drying process was also important.