To provide a method for producing a heat-treated lumber in which the occurrence of breaking, deformation, and warpage is prevented and which is improved in durability against decay, termite repelling properties, and safety.
The heat-treated lumber is produced by passing in turn through the first process in which lumber having a large cross section and a water content of at least 15% selected from a log having a sectional diameter of at least 50 mm, a square bar having the minimum side in the cross section of at least 50 mm, and a board having the minimum side in the cross section is at least 50 mm, by the use of at least one heating medium selected from superheated steam, microwaves, and heating oils, is dried to make its water content 12% or below while the temperature of the lumber is kept at 50-130C and the second process in which the lumber dried in the first process, by the use of at least one heating medium selected from superheated steam and heating oils, is heat-treated for 4-24 hours while the temperature of the lumber is kept at 180-250C.
Sadao Matsumura
Fumio Takino
Next Patent: OPTICAL FILM AND METHOD OF MANUFACTURING THE SAME