An anti-coking surface having a thickness up to 15 microns comprising from 15 to 50 wt. % of MnCr.sub.2O.sub.4 (for example manganochromite); from 15 to 25 wt. % of Cr.sub.0.23Mn.sub.0.08Ni.sub.0.69 (for example chromium manganese nickel); from 10 to 30 wt. % of Cr.sub.1.3Fe.sub.0.7O.sub.3 (for example chromium iron oxide); from 12 to 20 wt. % of Cr.sub.2O.sub.3 (for example eskolaite); from 4 to 20 wt. % of CuFe.sub.5O.sub.8 (for example copper iron oxide); and less than 5 wt. % of one or more compounds chosen from FeO(OH), CrO(OH), CrMn, Si and SiO.sub.2 (either as silicon oxide or quartz) and less than 0.5 wt. % of aluminum in any form provided that the sum of the components is 100 wt. % is provided on steel.

A manufacturing method of an electrical steel sheet according to an embodiment of the present invention includes: hot-rolling a slab to manufacture a hot-rolled sheet; removing some of scales formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more; controlling roughness of the hot-rolled sheet in which the scale layer remains; cold-rolling it to manufacture a cold-rolled sheet; and annealing the cold-rolled sheet.

A grain-oriented electrical steel sheet includes: a base steel sheet; an intermediate layer arranged in contact with the base steel sheet; and an insulation coating arranged in contact with the intermediate layer to be an outermost surface, in which a Cr content of the insulation coating is 0.1 at % or more on average, and when viewing a cross section whose cutting direction is parallel to a thickness direction, the insulation coating has a compound layer containing a crystalline phosphide in an area in contact with the intermediate layer.

Provided is an oriented electrical steel sheet including a groove existing on the surface of the electrical steel sheet and a forsterite layer formed on a part or all of the surface of the electrical steel sheet, in which forsterite which is extended from the forsterite layer and penetrates to a base steel sheet in an anchor form is present on the surface of the side of the groove.

Provided is an oriented electrical steel sheet including a groove existing on the surface of the electrical steel sheet and a forsterite layer formed on a part or all of the surface of the electrical steel sheet, in which forsterite which is extended from the forsterite layer and penetrates to a base steel sheet in an anchor form is present on the surface of the side of the groove.

A permanent magnet may include a Fe16N2 phase in a strained state. In some examples, strain may be preserved within the permanent magnet by a technique that includes etching an iron nitride-containing workpiece including Fe16N2 to introduce texture, straining the workpiece, and annealing the workpiece. In some examples, strain may be preserved within the permanent magnet by a technique that includes applying at a first temperature a layer of material to an iron nitride-containing workpiece including Fe16N2, and bringing the layer of material and the iron nitride-containing workpiece to a second temperature, where the material has a different coefficient of thermal expansion than the iron nitride-containing workpiece. A permanent magnet including an Fe16N2 phase with preserved strain also is disclosed.

A permanent magnet may include a Fe16N2 phase in a strained state. In some examples, strain may be preserved within the permanent magnet by a technique that includes etching an iron nitride-containing workpiece including Fe16N2 to introduce texture, straining the workpiece, and annealing the workpiece. In some examples, strain may be preserved within the permanent magnet by a technique that includes applying at a first temperature a layer of material to an iron nitride-containing workpiece including Fe16N2, and bringing the layer of material and the iron nitride-containing workpiece to a second temperature, where the material has a different coefficient of thermal expansion than the iron nitride-containing workpiece. A permanent magnet including an Fe16N2 phase with preserved strain also is disclosed.

An anti-coking equipment, a preparation method therefor, and the use thereof. The preparation method comprises: bringing a low-oxygen partial pressure gas into contact with an equipment for reaction to obtain an anti-coking equipment containing an oxide film on the inner surface, wherein the dew point of the low-oxygen partial pressure gas is -40° C. to 40° C.

A dense and stable oxide film is formed on the inner surface of the equipment prepared by the method, which can inhibit or slow down the catalytic coking phenomenon, reduce the degree of equipment carburization, and prolong the service life of the equipment.

A spring steel wire includes a main body made of a steel and having a line shape, and an oxidized layer covering an outer peripheral surface of the main body. The steel constituting the main body contains not less than 0.62 mass % and not more than 0.68 mass % C, not less than 1.6 mass % and not more than 2 mass % Si, not less than 0.2 mass % and not more than 0.5 mass % Mn, not less than 1.7 mass % and not more than 2 mass % Cr, and not less than 0.15 mass % and not more than 0.25 mass % V, with the balance being Fe and unavoidable impurities. A value obtained by dividing a sum of a Si content and a Mn content by a Cr content is not less than 0.9 and not more than 1.4. The steel constituting the main body has a tempered martensite structure.

An apparatus for manufacturing a stress relieved length of steel having an oxidised surface layer includes: a heating chamber; a reaction chamber coupled to the heating chamber; and a conveying mechanism conveying the length of steel along a path through the heating chamber and reaction chamber. The heating chamber includes a heating apparatus arranged to heat the length of steel in a heating portion of the path. The apparatus further includes a control means including a sealed unit defined by the heating chamber and the reaction chamber and arranged to control both the temperature of the length of steel and the atmosphere to which the length of steel is exposed in an oxidisation portion of the path within the reaction chamber in which the oxidised surface layer is formed. A method of manufacturing a stress relieved length of steel having an oxidised surface layer is also disclosed.