Abstract: Provided is a C/C composite having a long life in an environment including a heating process and a cooling process and having less adverse effects on surrounding facilities and the quality of treatment objects. A C/C composite in which, in measurement for open pores by mercury porosimetry, an open porosity for open pores with a radius of not less than 0.4 ?m and less than 10 ?m in the C/C composite is 2.0% or less.

Abstract: A heat treatment furnace jig having a box-like frame including a rim part and a bottom part, the bottom part being removable from the rim part, and a removable net of woven strands disposed in the box-like frame and supported from below by the bottom part. The net has a triaxial weave of strands, each strand having a bundle of carbon fibers that are aligned without twisting, wherein, among the woven strands, strands of at least one direction are held by two strands in another direction, and the net is impregnated with a matrix material.

Abstract: The present invention improves the strength of the bottom (net) of the jig and makes it more difficult and unlikely for deviation of the mesh to occur. A workpiece is loaded on the net (2) of the heat treat furnace jig (hereinafter, heat treatment furnace jig). In the net (2), a first strand (10), a second strand (20) and a third strand (30) are in contact at a contact point (X1). Near the contact point (X1), the second strand (20) overlaps the first strand (10) from above and the third strand (30) overlaps the first strand (10) from below. As a result, the first strand (10) is held between the second strand (20) and the third strand (30) in the up/down directions.

Abstract: The present invention improves the strength of the bottom (net) of the jig and makes it more difficult and unlikely for deviation of the mesh to occur. A workpiece is loaded on the net (2) of the heat treat furnace jig (hereinafter, heat treatment furnace jig). In the net (2), a first strand (10), a second strand (20) and a third strand (30) are in contact at a contact point (X1). Near the contact point (X1), the second strand (20) overlaps the first strand (10) from above and the third strand (30) overlaps the first strand (10) from below. As a result, the first strand (10) is held between the second strand (20) and the third strand (30) in the up/down directions.

Abstract: A purpose is to provide a tray for oil quenching heat treatment furnaces that can inhibit oil infiltration to reduce adverse effects on the quality of the workpiece and also can make lightweight design of the tray possible. Provided is a tray including a carbon material and being capable of placing a workpiece thereon for oil quenching of the workpiece, characterized in that the cumulative pore volume of pores with a pore radius of greater than or equal to 1 ?m is less than or equal to 40 mm3/g in the carbon material. The carbon material is desirably such that a C/C composite is impregnated with a thermosetting resin and burned.