A steel composition, a reinforcement part of a vehicle using the steel composition and a method of manufacturing the reinforcement part using the steel composition are provided. In particular, the steel composition includes increased content of carbon components and the steel composition is processed by rapid heating and immediate quenching.

A steel composition, a reinforcement part of a vehicle using the steel composition and a method of manufacturing the reinforcement part using the steel composition are provided. In particular, the steel composition includes increased content of carbon components and the steel composition is processed by rapid heating and immediate quenching.

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.

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.

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.

This application provides Fe—Mn—Al—C lightweight steel, including: Fe, wherein a weight percentage of the Fe is greater than or equal to 50.4 wt %; Mn, wherein a weight percentage of the Mn is 25-35 wt %; Al, wherein a weight percentage of the Al is 6-12 wt %; C, wherein a weight percentage of the C is 0.8-2.0 wt %; and O, wherein a weight percentage of the O is 0.005-0.6 wt %. This application further provides a terminal to which the Fe—Mn—Al—C lightweight steel is applied, a production method for the Fe—Mn—Al—C lightweight steel, a steel mechanical part, and an electronic device. The lightweight steel in this application has low density, high strength, and high elongation.

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.

An essentially lead free steel having improved machinability while reducing or eliminating lead (except for trace impurities) and without detriment of the material properties of the steel. The properties of the lead free steel are dependent on both the composition and method of manufacture. The improved lead free steel has, in percent by weight (wt-%): Carbon: 0.39-0.43%; Manganese: 0.75-1.00%; Silicon: 0.15-0.35%; Chromium: 0.80-1.05%; Molybdenum: 0.15-0.25%; at least one of Tellurium: 0.003-0.090 wt-%, Selenium: 0.080-0.2 wt-%, Sulfur: 0.065-0.09% wt-%, and Bismuth: 0.03-0.1 wt-%; and the balance being Fe and normally occurring scrap steel impurities. The hot-rolled lead-free steel product is subjected to a heat treatment at a first temperature for a first duration, at a second temperature for a second duration that is less than the first temperature, at a third temperature for a third time period that is greater than the second temperature, and subsequently cooling the steel product.

An essentially lead free steel having improved machinability while reducing or eliminating lead (except for trace impurities) and without detriment of the material properties of the steel. The properties of the lead free steel are dependent on both the composition and method of manufacture. The improved lead free steel has, in percent by weight (wt-%): Carbon: 0.39-0.43%; Manganese: 0.75-1.00%; Silicon: 0.15-0.35%; Chromium: 0.80-1.05%; Molybdenum: 0.15-0.25%; at least one of Tellurium: 0.003-0.090 wt-%, Selenium: 0.080-0.2 wt-%, Sulfur: 0.065-0.09% wt-%, and Bismuth: 0.03-0.1 wt-%; and the balance being Fe and normally occurring scrap steel impurities. The hot-rolled lead-free steel product is subjected to a heat treatment at a first temperature for a first duration, at a second temperature for a second duration that is less than the first temperature, at a third temperature for a third time period that is greater than the second temperature, and subsequently cooling the steel product.

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.