CARBON FIBER BUNDLE AND PRODUCTION METHOD THEREOF

PROBLEM TO BE SOLVED: To provide a carbon fiber which has excellent tensile elasticity and adhesion strength and exerts excellent mechanical strength even in carbon fiber reinforced composite materials using the carbon fiber in a very small amount used.SOLUTION: A method of producing a carbon fiber bundle comprises: subjecting a polyacrylonitrile based precursor fiber bundle to a flame resistance imparting treatment and preliminary carbonization to obtain a preliminarily carbonized fiber bundle of a trial length dependency coefficient mof the bundle strength of 2-9; and carbonizing the preliminarily carbonized fiber bundle in an inert atmosphere of 1,200-2,000°C under a tensile force of 13-18 mN/dtex, and the distance between drive rollers before and after the carbonization oven is set to be 50-500 mm. The carbon fiber bundle has a crystallite size Lc (nm) of 1.7-5.6, a crystal orientation (%) meeting the condition 3.1×Lc+82<