One: drying treatment
Artificial drying
The wood is sealed in a steam drying chamber, and steam is used to promote evaporation of water to dry the wood. (According to the size and thickness of the wood, such as 4cm plate drying time generally takes one week), the highest degree of drying can make the wood moisture content only 3%, usually the dryness of the log should be maintained at about 30% water content.
Natural drying
The wood is classified into a ventilated place (plate, square or log), and placed on a raft. The bottom of the raft is about 60cm away from the ground, leaving a gap in the middle to allow air to circulate, take away moisture, and gradually dry the wood. Natural drying usually takes several years or months to achieve certain drying requirements.
Second, the purpose of wood drying
Prevent parts from deforming and cracking
When the moisture in the wood is removed into the air, it causes a shrinkage of the volume of the wood. If the shrinkage is uneven, the wood will crack or deform. If the wood is dried to a level suitable for the environment to be used or the state required for use, the volumetric size of the wood can be kept relatively stable and durable.
Prevent deterioration and decay of wood and prolong the service life of wood products
If wet wood is piled up in the open air for a long time, it will often cause decay or insect damage if appropriate measures are not taken. When the moisture content of wood is reduced to less than 20%, the damage and destruction of fungi and pests can be reduced. Therefore, generally in the production unit, the wood is dried to a moisture content of about 8-15%. This not only ensures the inherent properties and strength of the wood, but also improves the corrosion resistance of the wood.
Improve the mechanical strength of wood and wood products to improve the physical properties of wood
When the moisture content of the wood is below the fiber saturation point, the physical and mechanical strength of the wood increases with its reduction; at the same time, the wood is also easy to be sawed and planed, reducing the loss of woodworking machinery.
Reduce the weight of wood and help improve carrying capacity
The newly cut wood has a water content that exceeds its own weight. After short-term storage and natural drying, its water content is still high. After the wood is dried through the chamber, its weight can be reduced by about 30-50%, which is beneficial to improve the carrying capacity of the vehicle.
In short, dried wood can guarantee the quality of wood products, improve the performance of wood and extend the service life, thus saving wood. Practice over the years has proven that wood drying is an indispensable process in production and has become a specialized discipline in science.
Three: How much should the wood be dried?
When the wood is placed in a certain environment, after a long enough time, the water content will tend to an equilibrium value, which is called the equilibrium moisture content of the environment. When the moisture content of the wood is higher than the equilibrium moisture content of the environment, the wood will shrink and contract, and vice versa. For example, the average annual equilibrium moisture content in Guangzhou is 15.1%, compared with 11.4% in Beijing. Drying to 11% of wood is suitable for Beijing, and it can be used in Guangzhou to absorb moisture and deform. Therefore, wood drying should be appropriate, not as dry as possible. Different areas and different uses have different requirements for wood moisture content.
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