Abstract: The present invention inexpensively provides a steel material having greater corrosion resistance than electromagnetic stainless steel and also having excellent magnetic properties. The steel material comprises, in % by mass, 0.001%-0.025% C, 1.0%-4.0% Si, 0.1%-1.0% Mn, more than 0% but no more than 0.030% P, more than 0% but no more than 0.10% S, more than 0% but less than 4.0% Cr, more than 0% but no more than 0.010% Al, and more than 0% but no more than 0.01% N, with the remainder being iron and unavoidable impurities; and is characterized by having an oxide coating formed on the steel surface material, said oxide coating including either Si or Cr, or both, including a non-crystalline layer, and having a thickness of 50-500 nm.

Abstract: Provided is a steel for a mechanical structure for cold working, which contains C, Si, Mn, P, S, Al and N and in which the metal structure includes pearlite and ferrite, the total areal proportion of pearlite and ferrite relative to the overall structure is 90% or higher, the average circle-equivalent diameter of bcc-Fe crystal grains surrounded by large angle grain boundaries is 5-15 ?m, the average aspect ratio of pro-eutectoid ferrite crystal grains is 3.0 or lower, and the average spacing at the narrowest pearlite lamellar spacing is 0.20 ?m or less.

Abstract: An object of the present invention to provide a soft magnetic steel that improves the magnetic properties, that is, the soft magnetic properties, the cold forgeability, and the magnetic aging characteristics without adding a large amount of alloy elements. The present invention is directed to a soft magnetic steel, including C, Mn, P, S, Al, and N in each predetermined amount, in which an area ratio of carbides and carbonitrides that have a thickness of less than 0.4 ?m is 0.20 area % or less, and an area ratio M of carbides and carbonitrides that have a thickness of 0.4 ?m or more in terms of percentage satisfies a relationship represented by the formula (1) below: F=M?20×[C]>0??(1) where [C] means a C content in the steel in percentage by mass.

Abstract: Provided is a steel for a mechanical structure for cold working, which contains C, Si, Mn, P, S, Al and N and in which the metal structure includes pearlite and ferrite, the total areal proportion of pearlite and ferrite relative to the overall structure is 90% or higher, the average circle-equivalent diameter of bcc-Fe crystal grains surrounded by large angle grain boundaries is 5-15 ?m, the average aspect ratio of pro-eutectoid ferrite crystal grains is 3.0 or lower, and the average spacing at the narrowest pearlite lamellar spacing is 0.20 ?m or less.

Abstract: To provide a coil spring having excellent fatigue resistance. Disclosed is a coil spring made of steel, including (in % by mass, the same shall apply for a chemical composition): C: 0.40 to 0.70%; Si: 1.50 to 3.50%; Mn: 0.30 to 1.50%; Cr: 0.10 to 1.50%; V: 0.50 to 1.00%, and Al: 0.01% or less (excluding 0%), with the balance being iron and inevitable impurities, wherein an average crystal grain size number of prior austenite crystals in a depth of 0.3 mm from a surface is 11.0 or more, while a difference in grain size number between the respective prior austenite crystals is in a range of less than 3 from a grain size number observed at the maximum frequency, and wherein a carburized layer is provided in a depth of 0.30 to 1.00 mm from the surface, while an average Vickers hardness is 600 or higher at a position in a depth of (¼)×diameter in the depth direction from the surface.

Abstract: Provided is a steel material for soft magnetic components, having excellent pickling properties and capable of achieving excellent magnetic properties and corrosion resistance in a final component. The steel material for soft magnetic components comprises, in % by mass, 0.001%-0.025% C, more than 0% but less than 1.0% Si, 0.1%-1.0% Mn, more than 0% but no more than 0.030% P, more than 0% but no more than 0.08% S, more than 0% but less than 0.5% Cr, more than 0% but no more than 0.010% Al, and more than 0% but no more than 0.01% N, with the remainder being iron and unavoidable impurities; and is characterized by having a rolled scale including 40-80 vol % FeO being formed on the steel material surface.

Abstract: The present invention inexpensively provides a steel material having greater corrosion resistance than electromagnetic stainless steel and also having excellent magnetic properties. The steel material comprises, in % by mass, 0.001%-0.025% C, 1.0%-4.0% Si, 0.1%-1.0% Mn, more than 0% but no more than 0.030% P, more than 0% but no more than 0.10% S, more than 0% but less than 4.0% Cr, more than 0% but no more than 0.010% Al, and more than 0% but no more than 0.01% N, with the remainder being iron and unavoidable impurities; and is characterized by having an oxide coating formed on the steel surface material, said oxide coating including either Si or Cr, or both, including a non-crystalline layer, and having a thickness of 50-500 nm.

Abstract: Disclosed is a spring steel which contains, by mass, 1.2% or less C; 0.1% to 2% Mn; 0.2% to 3% Si; 0.0003% to 0.005% Al; to 8 ppm Li; 30 ppm or less (excluding 0 ppm) Ca; and 10 ppm or less (excluding 0 ppm) Mg. The steel contains oxide inclusions satisfying the following conditions (1) to (3) in a number of 1×10?4 or more per square millimeter: (1) containing a total of 80 percent by mass or more of Al2O3 and SiO2 based on the inclusion composition excluding Li2O; (2) having a ratio by mass of Al2O3 to SiO2 of from 1:4 to 2:3; and (3) containing lithium (Li). The spring steel gives a spring that exhibits superior fatigue properties without strict control of the average composition of inclusions.

Abstract: Disclosed is a spring steel which contains, by mass, 1.2% or less C; 0.1% to 2% Mn; 0.2% to 3% Si; 0.0003% to 0.005% Al; to 8 ppm Li; 30 ppm or less (excluding 0 ppm) Ca; and 10 ppm or less (excluding 0 ppm) Mg. The steel contains oxide inclusions satisfying the following conditions (1) to (3) in a number of 1×10?4 or more per square millimeter: (1) containing a total of 80 percent by mass or more of Al2O3 and SiO2 based on the inclusion composition excluding Li2O; (2) having a ratio by mass of Al2O3 to SiO2 of from 1:4 to 2:3; and (3) containing lithium (Li). The spring steel gives a spring that exhibits superior fatigue properties without strict control of the average composition of inclusions.