Abstract: High tensile strength, high Young's modulus carbon fiber, free from holes and voids having a statistical probability of holes detected by a standard plasma etching test of less than about 2%, a tensile strength of at least about 150 kg/mm.sup.2 and a Young's modulus of at least about 15 .times. 10.sup.3 kg/mm.sup.2. The carbon fiber has excellent homogeneity of internal structure and excellent reliability as a composite material.A process is provided for producing a high performance, high quality carbon fiber having excellent productivity and operability and requiring only a short time for oxidation. The process comprises converting an organic polymeric fiber (preferably an acrylic fiber) to an oxidized fiber, comprising repeatedly bringing said fiber into contact with the surface of a heated body such as a heated roll or heated plate at about 200.degree. - 400.degree.

Abstract: Organic fibrous material is changed to heat-stabilized material by heating in an atmosphere, and then the heat-stabilized material is carbonized in a carbonizing furnace at a temperature of from about 800.degree.C to 1600.degree.C.When temperature at any given point in the furnace is plotted on a vertical axis and the particular location along the length of the carbonizing furnace is plotted on a horizontal axis, the slope of the resulting temperature profile above 800.degree.C either remains constant or decreases until the maximum temperature in the furnace is reached.

Abstract: High tensile strength, high Young's modulus carbon fiber, free from holes and voids having a statistical probability of holes detected by a standard plasma etching test of less than about 2%, a tensile strength of at least about 150 kg/mm.sup.2 and a Young's modulus of at least about 15.times.10.sup.3 kg/mm.sup.2. The carbon fiber has excellent homogeneity of internal structure and excellent reliability as a composite material.A process is provided for producing a high performance, high quality carbon fiber having excellent productivity and operability and requiring only a short time for oxidation. The process comprises converting an organic polymeric fiber (preferably an acrylic fiber) to an oxidized fiber, comprising repeatedly bringing said fiber into contact with the surface of a heated body such as a heated roll or heated plate at about 200.degree.-400.degree. C.