焊接时间和氯化铜处理对木榫焊接性能的影响机制

Influence Mechanisms of Welding Time and CuCl2 Treatment on the Weldability of Dowels

选取国产落叶松作为木榫旋转焊接基材,采用氯化铜浸渍桦木木榫,分析焊接时间和氯化铜处理对焊接性能的影响机制。结果表明:1)未处理试验组焊接时间3s的试件抗拉拔力平均值分别高于5s和7s试件28.33%、87.12%;氯化铜浸渍处理试验组焊接时间3s的试件抗拉拔力平均值分别高于5s和7s试件61.06%、130.49%;同样的焊接时间条件下,氯化铜浸渍处理试验组焊接时间3s比未处理试验组高68.28%,焊接时间5s高34.08%,焊接时间7s高36.62%。2)未处理试验组不同焊接时间界面最高温度和深度之间均符合线性关系,氯化铜浸渍处理试验组焊接界面最高温度低于未处理焊接界面。3)采用FTIR对未处理木榫与界面、氯化铜浸渍处理木榫与界面的对比分析,发现桦木圆棒榫在经过氯化铜浸渍处理后可能发生了半纤维素和纤维素的酸水解,半纤维素、无定型物质等在焊接过程中均发生了热解,同时有大量物质氧化形成C-O和C=O,随着焊接时间的延长,木材组分的热解程度增加。木榫旋转焊接的机理是焊接过程中半纤维素和无定型物质热解熔融并包覆纤维形成焊接界面层。氯化铜浸渍处理的增强机制为氯化铜浸渍处理可能引起半纤维素和纤维素的酸水解,促进焊接过程中木材组分的解聚、热解形成熔融物质。

In this paper,welded specimens were manufactured by rotation welding with Betula wood dowel and Larch substrate.Wood dowels were pretreated by immersing in CuCl2 solution.The influence mechanisms of welding time and CuCl 2 treatment on the weldabilities of the dowels were studied.The results showed that 1) the pullout resistance of the untreated woods with welding time 3s was 28.33% and 87.12% higher than that those with welding time 5 s and 7 s,respectively.For the CuCl2 treated groups,the pullout resistance of welding time 3 s was 61.06% and 130.49% higher than those of welding time 5 s and 7 s,respectively.Under the same welding time 3 s,5 s and 7 s,the pullout resistance of CuCl2 treated groups was 68.28%,34.08% and 36.62% higher than those of untreated groups,respectively.2) The linear relationship existed between the highest temperature of the welding interface and depth for untreated groups.The highest temperatures of welding interface for CuCl 2 treated groups were lower than those of untreated groups.3) The analyses of chemical groups for wood dowel and welding interface conducted by FTIR indicated that acid hydrolysis of hemicellulose and cellulose of wood dowel might occur after the immersing process.The pyrolysis of hemicellulose and amorphous substance might also occur during the welding process,with the formation of C-O and C=O oxygen-containing materials.With the extending of welding time,the degree of pyrolysis of wood components increased.The mechanism of wood dowels welded into substrates was that fiber was covered by the molten materials of pyrolysed hemicellulose and amorphous materials in the welding interface during the welding process.The enhancement mechanism of wood dowel treated with CuCl 2 was that acid hydrolysis of hemicellulose and cellulose of wood dowel might occur during immersion which may promote the formation of molten materials by the depolymerization and pyrolysis of wood constituents.