Abstract: A tough high strength heavy wall steel material having superior weldability is provided, said steel material has a diameter or a side 5 mm or more in length, and comprises oxides 1 ?m or less in particle diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 particles/mm2 and uniform ferrite grains 2 ?m or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction.

Abstract: A high Cr ferritic heat-resistant steel (Cr content of 15 mass % or less), which, at least a region 10 &mgr;m in depth as measured from the surface has a worked texture comprising elongated ferritic grains or a fine crystal grain texture comprising ferritic grains of 3 &mgr;m or less in diameter, and has a protective coating film on the surface; it is a high Cr ferritic heat-resistant steel improved in oxidation resistance without causing drop in high temperature strength or in toughness.

Abstract: A tough high strength heavy wall steel material having superior weldability is provided, said steel material has a diameter or a side 5 mm or more in length, and comprises oxides 1 &mgr;m or less in particle diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 particles/mm2 and uniform ferrite grains 2 &mgr;m or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction.

Abstract: A fine ferrite-based steel is disclosed, wherein at least 60% of the ferrite grain boundary is a large angle grain boundary of at least 15°, and the mean ferrite grain size is not more than 2.5 &mgr;m. The fine ferrite-based steel of the invention has a high strength and a long fatigue life.

Abstract: A method of producing a ultra fine grain steel made of ferrite having a mean grain size of not larger that 3 &mgr;m as the base phase, after ingoting raw materials, by austenitizing the ingot by heating it to a temperature of at least an Ac 3 point, then, applying compression working of a reduction ratio of at least 50% at a temperature of from an Ae 3 point or lower to an Ar 3 point −150° C., or at a temperature of at least 550° C., and thereafter, cooling, wherein the strain rate as compression working is in the range of from 0.001 to 10/second.

Abstract: A tough high strength heavy wall steel material having superior weldability is provided, said steel material has a diameter or a side 5 mm or more in length, and comprises oxides 1 &mgr;m or less in particle diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 particles/mm2 and uniform ferrite grains 2 &mgr;m or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction.

Abstract: A fine ferrite-based steel is disclosed, wherein at least 60% of the ferrite grain boundary is a large angle grain boundary of at least 15°, and the mean ferrite grain size is not more than 2.5 &mgr;m. The fine ferrite-based steel of the invention has a high strength and a long fatigue life.

Abstract: A high strength phosphorus-containing steel having fine texture free from the problem of embrittlement by positively using the presence of P, which is a carbon steel having an average ferritic grain diameter of 3 &mgr;m or less and containing from 0.04 to 0.1% by mass of P, wherein the volume fraction of P segregated in the grain boundary accounts for 0.3 or less in case the grain boundary is covered by a P layer 1 nm in thickness.

Abstract: The invention provides an ultra-fine grain steel comprising fine ferrite grains as oriented at random and surrounded by large angle grain boundaries. The steel comprises fine ferrite grains having a mean grain size of not larger and 3.0 &mgr;m and surrounded by large angle grain boundaries having an misorientation not smaller than 15°.

Abstract: In carbon steel, oxides with grain diameter of 1 .mu.m or less and with grain spacing of 6 .mu.m or less are dispersed to suppress growth of .gamma. grains by heating at .gamma. region temperature.

Abstract: A ceramic sintered body comprising TiB.sub.2 as the principal component, 0.5 to 30 wt. % of SiC and 2 to 40 wt. % of ZrO.sub.2. In some cases ZrO.sub.2 includes stabilizers for tetragonal crystal, such as Y.sub.2 O.sub.3, MgO or CeO.sub.2. The sintered body has a dense structure where TiB.sub.2, ZrO.sub.2 and SiC uniformly disperse. ZrO.sub.2 is located at the grain boundary of TiB.sub.2, and inhibits the grain growth of TiB.sub.2 as well as improves the strength of the sintered body by binding it to TiB.sub.2 strongly. SiC is located not only at the grain boundary but also on the inside of both grains. Since the contract of SiC during cooling process of the sintered body is less than TiB.sub.2 and ZrO.sub.2, compressive stress is produced in SiC and around thereof. The sintered body is remarkably strengthened by the residual compressive stress, and simultaneously, the high fracture toughness is also achieved.