Starting pitches for carbon fibers

A process for the production of carbon fibers which comprises heat treating a starting pitch to obtain a precursor pitch, melt spinning the thus obtained precursor pitch, infusibilizing the thus spun pitch, carbonizing the thus infusibilized pitch, and if desired, graphitizing the thus carbonated pitch, wherein the starting pitch is produced by the following method:

• (A) mixing 100 parts by volume of (1) a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of steam cracking of petroleum with 10-200 parts by volume of (2) a hydrogenated oil selected from the group consisting of:
• (a) aromatic nucleus hydrogenated hydrocarbons prepared from aromatic hydrocarbons of 2-10 rings by hydrogenating the aromatic nucleus thereof;
• (b) a hydrogenated oil obtained by contacting a fraction oil boiling at 160.degree.-650.degree. C. produced at the time of heat treating, at 370.degree.-480.degree. C., a heavy fraction oil boiling at not lower than 200.degree. C. obtained at the time of steam cracking a fraction and/or petroleum boiling at 160.degree.-650.degree. C. obtained at the time of steam cracking petroleum, with hydrogen in the presence of a hydrogenating catalyst to hydrogenate 10-70% of the aromatic nucleus of aromatic hydrocarbons contained in said fraction boiling at 160.degree.-650.degree. C.;
• and
• (c) a hydrogenated oil obtained by contacting a fraction boiling at 160.degree.-650.degree. C. produced at the time of preparing the starting pitches by heat treatment,
• with hydrogen in the presence of a hydrogenating catalyst to hydrogenate 10-70% of the aromatic nuclei of aromatic hydrocarbons contained in said fraction boiling at 160.degree.-650.degree. C., to form a mixture of the oils (1) and (2), and then
• (B) heat treating the thus formed oil mixture at 370.degree.-480.degree. C. under a pressure of 2-50 kg/cm.sup.2.G thereby to obtain the starting pitch.