The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value—a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Provided are a non-heat treated wire rod having high drawability and impact toughness, and a method for manufacturing the non-heat treated wire rod. The non-heat treated wire rod includes, by wt%, C: 0.02% to 0.30%, Si: 0.05% to 0.8%, Mn: 0.5% to 2.0%, Cr: 1.0% or less, P: 0.03% or less, S: 0.03% or less, sol.Al: 0.01% to 0.07%, N: from greater than 0.01% to 0.02%, Nb: 0.1% or less, V: 0.5% or less, and Ti: 0.1% or less, and a balance of Fe and inevitable impurities, wherein the non-heat treated wire rod has a microstructure including ferrite and pearlite.

Disclosed are a wire rod and a component, for cold forging, each having excellent delayed fracture resistance characteristics and applicable to high-strength bolts and the like and a manufacturing method therefor.

According to an embodiment, a heat-treated component having excellent delayed fracture resistance characteristics includes, in percent by weight (wt %), 0.3 to 0.5% of C, 0.01 to 0.3% of Si, 0.3 to 1.0% of Mn, at least two types selected from the group consisting of 0.3 to 1.5% of Cr, 0.3 to 1.5% of Mo, and 0.01 to 0.4% of V, and the balance being Fe and other impurities, includes, as a microstructure, a tempered martensite phase in an area fraction of 95% or more, and includes V-based carbides having a diameter of 300 nm or less at 10/100 μm.sup.2 or more.

An inductive hardening system for hardening a component includes a holding unit for holding the component, an induction coil configured to induce an electrical current in the component to heat the component, and a control unit configured to control the induction coil to produce a first amount of heat per unit area in the component until a predetermined temperature is reached and/or a predetermined time is elapsed and after the predetermined temperature is reached and/or the predetermined time is elapsed, to control the induction coil to produce a second amount of heat per unit area in the component, the second amount of heat being from 3% to 80% of the first amount of heat.

A method of making a forged, martensitic, stainless steel alloy is provided. The alloy is a forged preform of martensitic, pitting corrosion resistant stainless steel alloy comprising, by weight: 12.0 to 16.0 percent chromium; greater than 16.0 to 20.0 percent cobalt, 6.0 to 8.0 percent molybdenum, 1.0 to 3.0 percent nickel, 0.02 to 0.04 percent carbon; and the balance iron and incidental impurities. The alloy has a microstructure that comprises a retained austenite phase less than or equal to 2 percent by volume of the microstructure. The method heats the preform to a solutionizing temperature to form a solutionized microstructure. The preform is cooled with a liquid to room temperature. The preform is immersed in a cryo-liquid to transform the retained austenite phase in the microstructure to martensite. The preform is heated to a temperature of less than 600° F. for a time sufficient to form a tempered forged preform.

Provided is a stainless steel sheet having a predetermined chemical composition, in which a total volume fraction of Cr-based carbides with a grain size of 2.0 μm or more is 10% or less.

Provided is a steel component with excellent surface fatigue strength. The steel component has a nitride compound layer with a thickness of 5.0 μm to 30.0 μm and a hardened layer in an order from a component surface to a component inside, where a thickness of a porous layer on an outermost surface of the nitride compound layer is 3.0 μm or less and 40.0% or less of a thickness of the nitride compound layer, and the hardened layer has a hardness of HV600 or more at a position of 50 μm inward from the component surface, a hardness of HV400 or more at a position from the component surface to the component inside of 400 μm, and a hardness of HV250 or more at a position from the component surface to the component inside of 600 μm.

A high permeability grain oriented electrical steel having a chemistry comprising, all in weight percent, 2.5% to 4.5% silicon, 0.02% to 0.08% carbon, 0.01 to 0.05% aluminum, 0.005% to 0.050% sulfur or selenium, 0.02 to 0.20% manganese, 0.05 to 0.20% tin, 0.05 to 1% copper, 0.5% to 2.0% chromium, up to 0.10% phosphorus and up to 0.20% antimony with the balance being essentially iron and residual elements. The steel contains chromium and phosphorus in such amounts that a Cr:(P+0.25Sb) ratio is below 80:1 or, below 50:1, or below 30:1 which provides highly stable magnetic properties in the finished steel sheet. A hot processed band comprised of such steel is annealed and rapidly cooled after such annealing at a rate of at least 50° C. per second from 875-950° C. to a temperature below 400° C. prior to cold rolling to final thickness. Such steel forming a hot processed band having a thickness of from 1.5 to 4.0 mm and having a volume resistivity of at least 50 μΩ-cm, an austenite volume fraction (γ1150° C.) of at least 20%, and an isomorphic layer thickness of at least 2% of the total thickness on at least one surface of the hot processed band.

A vacuum solid solution method for nickel-free high manganese and nitrogen is provided and relates to the technical field of metal material heat treatment. By vacuumizing, heat homogenizing, keeping the temperature in the final temperature range, deoxidation, and rapid cooling treatment, the present method forms a single austenitic structure from the raw materials, and promotes full and uniform dispersion of nitrogen carbide, providing a nickel-free high nitrogen stainless steel with more stable comprehensive performance and wider range of application.

Provided is a steel used for chassis parts, etc. of an automobile and, more specifically, to a hot rolled steel plate for an electric resistance welded steel pipe, which shows an excellent weldability in electric resistance welding, and a manufacturing method thereof.