TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The preweb forming device comprises: an opening machine for uniformly mixing and loosening the lumps of entangled oxidized carbon precursor staple fibers and the lumps of entangled binder staple fibers and disentangling them; a carding machine for arranging the oxidized carbon precursor staple fibers and the binder staple fibers in parallel and collecting them to form an oxidized carbon precursor fiber preweb in a sheet shape; a cross lapping machine for stacking the oxidized carbon precursor fiber preweb discharged from the carding machine into many layers to produce an oxidized carbon precursor fiber preweb with a desired weight; a needle-punching machine for mechanically entangling the oxidized carbon precursor staple fibers and the binder staple fibers with each other from the thus-cross lapped carbon precursor fiber preweb by needle-punching to prepare a thus-bound oxidized carbon precursor fiber preweb; a calendaring machine for heating and pressing the oxidized carbon precursor fiber preweb which has been bound; and a winding machine for winding the oxidized carbon precursor fiber preweb. The curing device is a multi-step rolling curing device for sequentially performing a preheating step, a heat-press curing step and a cooling step. The multi-step rolling curing device comprises: a preheating unit for preheating the oxidized carbon precursor fiber web while it is being transferred at 100-150 degrees C; a rolling curing unit having two or more pairs of rolls whose rolling gaps formed to be progressively narrowed in the transfer direction of the oxidized carbon precursor fiber web in order to transfer, press and cure the oxidized carbon precursor fiber web at 130-250 degrees C; and a cooling unit for air-cooling the oxidized carbon precursor fiber web which has been pressed and cured to a predetermined thickness by the rolling curing unit. The preheating unit comprises a heating belt which is installed on and under the oxidized carbon precursor fiber web and rotates in the transfer direction of the web; and two or more pre-heaters which are provided in the heating belt and heat the heating belt to allow the oxidized carbon precursor fiber web to be progressively heated in the transfer direction. The preheating unit is formed to enclose the oxidized carbon precursor fiber web while it is being transferred and comprises two or more heating chambers which are sectioned in the transfer direction of the oxidized carbon precursor fiber web to progressively heat the oxidized carbon precursor fiber web and respective pre-heaters provided in the heating chambers. The rolling curing unit comprises two or more press roll units with each press roll unit including a pair of rolls, each pair of rolls disposed to face each other on and under the oxidized carbon precursor fiber web in order to transfer, press and cure the web, where the two or more press roll units are horizontally arranged, and roll heaters are provided on at least one side of the inner and outer sides of the rolls of the press roll unit, the heating temperatures of the two or more press roll units are set to be progressively increased in the transfer direction of the oxidized carbon precursor fiber web, and the gaps between each pair of upper and lower rolls in the two or more press roll units are set to be progressively narrowed in the transfer direction of the web. The rolling curing unit comprises two or more press roll units with each press roll unit including a pair of rolls, each pair of rolls disposed to face each other on both sides of the oxidized carbon precursor fiber web in order to transfer, press and cure the web, and the two or more press roll units are vertically arranged, a guide roll is provided between the two press roll units to guide the oxidized carbon precursor fiber web to the next press roll unit, roll heaters are provided on at least one side of the inner and outer sides of the rolls of the press roll unit, the heating temperatures of the two or more press roll units are set to be progressively increased in the transfer direction of the web, and the gaps between each pair of rolls in the two or more press roll units are set to be progressively narrowed in the transfer direction of the oxidized carbon precursor fiber web. The cooling unit comprises two or more cooling chambers, each separately disposed in the transfer direction of the oxidized carbon precursor fiber web, and the cooling chambers are configured to allow each cooling air to be supplied and thus the oxidized carbon precursor fiber web is slowly cooled while passing each cooling chamber. The carbonization device comprises a carbonization furnace for carbonizing oxidized carbon precursor staple fibers, a thermosetting resin, and binder staple fibers of the oxidized carbon precursor fiber web in an inert atmosphere at 600-1000 degrees C; and a graphitization furnace for further heating the carbonized web under an inert atmosphere at 1300-2000 degrees C to form a graphite structure in carbonized carbon fibers which have been formed by the carbonization.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The oxidized carbon precursor fiber preweb forming process comprises: an opening step for uniformly mixing and loosening the lumps of oxidized carbon precursor staple fibers and the lumps of binder staple fibers, and disentangling them by using an opening machine; a carding step for arranging the oxidized carbon precursor staple fibers and the binder staple fibers in parallel and collecting them to form an oxidized carbon precursor fiber preweb in a sheet shape by using a carding machine; a cross-lapping step for stacking the oxidized carbon precursor fiber preweb discharged from the carding machine into many layers to obtain an oxidized carbon precursor fiber preweb with a desired weight; a bonding step for allowing the oxidized carbon precursor staple fibers and the binder staple fibers to be mechanically entangled with each other by needle-punching using a special needle to bind the oxidized carbon precursor fiber preweb; a heat-pressing step for heat-pressing the oxidized carbon precursor fiber preweb thus-bound by calendaring the preweb; and a winding step for winding the oxidized carbon precursor fiber preweb. The curing process is performed by a multi-step rolling curing process comprising a preheating step, a heat-press curing step and a cooling step. The multi-step rolling curing process comprises: a preheating process for preheating the oxidized carbon precursor fiber web, which has been impregnated with the thermosetting resin and the carbonaceous fillers, while it is being transferred at 100-150 degrees C; a continuous rolling curing process for pressing and curing the oxidized carbon precursor fiber web, while it is being transferred at 130-250 degrees C by a rolling curing unit having two or more pairs of rolls whose rolling gaps formed to be progressively narrowed in the transfer direction of the oxidized carbon precursor fiber web; and a cooling process for air-cooling the oxidized carbon precursor fiber web which has been pressed and cured to a predetermined thickness through the continuous rolling curing process. The preheating process is performed by sequential heating at a temperature of two or more different stages within a range of 100-150 degrees C. In the continuous rolling curing process, the oxidized carbon precursor fiber web is heated and pressed while continuously passing through at least two pairs of rolls of the rolling curing unit in a manner in which the oxidized carbon precursor fiber web passes through a first pair of rolls having a gap of 300-1000 mu m at 130-250 degrees C, subsequently passes through a second pair of rolls having a gap of 250-600 mu m 130-250 degrees C, and then passes through a N-pair of rolls (where N is a natural number in range of 3-10) having a gap of 200-400 mu m at 130-250 degrees C. The cooling process is performed in a manner in which the oxidized carbon precursor fiber web heated in the continuous rolling curing process is sequentially cooled at a temperature of two or more stages to be slowly cooled. The carbonization process comprises: a carbonization step for heating the oxidized carbon precursor fiber web in an inert atmosphere at 600-1000 degrees C to carbonize the oxidized carbon precursor staple fibers, the thermosetting resin, and the binder staple fibers; and a graphitization step for further heating the carbonized web in an inert atmosphere at 1300-2000 degrees C to form a graphite structure in the carbon fibers which has been formed by the carbonization. Preferred Components: The binder staple fibers are present in at 1-30 wt.%, based on weight of the preweb, and are thermoplastic polymer staple fiber with a melting point of less than or equal to 300 degrees C. The oxidized carbon precursor staple fibers are at least one of oxidized polyacrylonitrile-based staple fibers, oxidized pitch-based staple fibers, oxidized polyvinyl alcohol-based staple fibers, oxidized cellulose-based staple fibers or oxidized phenolic resin-based staple fibers, and the binder staple fibers are at least one of polyvinyl alcohol staple fibers, low melting point polyester staple fibers, polyethylene staple fibers, polypropylene staple fibers, cellulose staple fibers or pitch staple fibers. EXAMPLE - Oxidized polyacrylonitrile-based staple fibers (90 wt.%) with 62% carbon content, and polyvinyl alcohol staple fibers (10 wt.%) were uniformly mixed. Fiber opening/mixing treatment, a carding treatment, a cross lapping treatment, a binding treatment by needle-punching, a heat-press treatment for performing calendaring at a pressure of 3 kgf/cm2, and a winding treatment were performed by using the staple fiber mixture to form an oxidized carbon precursor fiber preweb. The oxidized carbon precursor fiber preweb was impregnated with slurry prepared by mixing a phenolic resin solution, N-methyl-2-pyrrolidone and graphite particles. Then curing process at 120 degrees C, and carbonization process were performed on the thus-obtained oxidized carbon precursor fiber preweb by using the system for manufacturing a carbon substrate, to obtain carbon substrate.