Abstract: An orifice plate for liquid injection made of plate-shaped stainless steel, wherein an orifice is formed by shearing, is characterized in that the average crystal grain size of the stainless steel is 3 ?m or less. The thickness of the plate-shaped stainless steel is 1.2 mm or less, and preferably 0.1 mm or less. The aspect ratio of the orifices is 0.8 or lower. The orifices are formed orthogonal to the plate surface, or slanted by 50° or at smaller angles. The plate-shaped stainless steel has a composition containing C, Mn, and Si.

Abstract: An orifice plate for liquid injection made of plate-shaped stainless steel, wherein an orifice is formed by shearing, is characterized in that the average crystal grain size of the stainless steel is 3 ?m or less. The thickness of the plate-shaped stainless steel is 1.2 mm or less, and preferably 0.1 mm or less. The aspect ratio of the orifices is 0.8 or lower. The orifices are formed orthogonal to the plate surface, or slanted by 50° or at smaller angles. The plate-shaped stainless steel has a composition containing C, Mn, and Si.

Abstract: A formed product, characterized in that it is produced by using, as a material, a steel having an ultra fine structure comprising ferrite grains having an average grain diameter of 3 ?m or less and by a method comprising only a forming step and including none of refining steps; and a method for producting the above formed product with ease. The formed product contains no alloying element and has been subjected to no refining step, and has been imparted with high strength and high toughness by the above ultra fine structure.

Abstract: There are provided an excellent cold-workability exhibiting high-strength steel wire or steel bar, or high-strength shaped article and a process for producing them. In particular, there is provided a process comprising carrying out hot working at 350 to 800° C. of a steel ingot, cast slab, steel slab or steel semifinished product having a C content of not greater than the solid solution limit of carbon of ferrite phase at Ae1 point and not greater than 0.010 mass % and being free of any cementite, or having a C content of >0.01 to 0.45 mass % to thereby obtain a material whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ?3 ?m, and thereafter carrying out cold working of the material to thereby attain formation of a ferrite structure whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ?500 nm.

Abstract: A method of rolling a material in two more continuous passes is disclosed. The method includes rolling the material with a flattened-shaped caliber in a first pass, and subsequently rolling with a square-shaped caliber in a second pass. The rolling is performed with a first pass caliber having a flattened shape, wherein the ratio of the length (2A01) of minor axis of the first pass caliber to an initial width (2A0) is (A01/A0)?0.75; and a second pass caliber, wherein the ratio of a diagonal dimension (2AS1) of the second pass caliber to the length (2B1) of the major axis of the material after the first pass is (AS1/B1)?0.75 to introduce the large strain into the material.

Abstract: A formed product, characterized in that it is produced by using, as a material, a steel having an ultra fine structure comprising ferrite grains having an average grain diameter of 3 ?m or less and by a method comprising only a forming step and including none of refining steps; and a method for producting the above formed product with ease. The formed product contains no alloying element and has been subjected to no refining step, and has been imparted with high strength and high toughness by the above ultra fine structure.

Abstract: There are provided an excellent cold-workability exhibiting high-strength steel wire or steel bar, or high-strength shaped article and a process for producing them. In particular, there is provided a process comprising carrying out hot working at 350 to 800° C. of a steel ingot, cast slab, steel slab or steel semifinished product having a C content of not greater than the solid solution limit of carbon of ferrite phase at Ael point and not greater than 0.010 mass % and being free of any cementite, or having a C content of >0.01 to 0.45 mass % to thereby obtain a material whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ?3 ?m, and thereafter carrying out cold working of the material to thereby attain formation of a ferrite structure whose average crystal grain diameter in a cross section perpendicular to the longitudinal direction is ?500 nm.

Abstract: A method of rolling with a flattened-shaped caliber in a 1st pass and subsequently roiling with a square-shaped caliber in a 2nd pass In a caliber rolling of two or more continuous passes. The rolling is performed with a caliber which sets the ratio of the minor axis (2A01) of a 1st pass flattened to a material opposite side dimension (2A0) to A01/A0?0.75 and the ratio of a 2nd pass vertical diagonal dimension 2As1 to the major axis 2B1 of a material after the 1st pass to As1/B1?0.75 to introduce the large strain into the material. Thus, the effect of the distribution of strain introduced into the material in the 1st pass on the distribution of strain and the shape of the next pass is made clear so that the large strain can be introduced into the entire cross sectional are of the material, particularly at the center of the material.

Abstract: A multi-directional warm-rolling method for manufacturing an ultrafine grain steel material with an ultrafine grain structure of 3 ?m or smaller in average grain size. When roiling of two passes or more is performed for a steel material in the rolling temperature range of 350 to 800° C., a rolling by an oval shape caliber and a rolling by the other shape caliber an performed at leas one time so that a large amount of strain can be introduced into the material by a simple means with less section reduction ratio and less number of passes. Steel materials having the ultrafine grain structure and excellent strength and ductility can be manufactured by this method.

Abstract: A formed product, characterized in that it is produced by using, as a material, a steel having an ultra fine structure comprising ferrite grains having an average grain diameter of 3 ?m or less and by a method comprising only a forming step and including none of refining steps; and a method for producting the above formed product with ease. The formed product contains no alloying element and has been subjected to no refining step, and has been imparted with high strength and high toughness by the above ultra fine structure.