64results about How to "Good spot weldability" patented technology

Disclosed is a high-strength composite steel sheet having a tensile strength of 980 MPa or greater and excellent in moldability, delayed fracture resistance and spot weldability. The steel sheet comprises a steel having the following chemical composition: C: 0.12-0.25%, Si: 1.0-3.0%, Mn: 1.5-3.0%, P: 0.15% or less, S: 0.02% or less, Al: 0.4% or less, and Cr: 1.0% or less, with the remainder being iron and unavoidable impurities, wherein the contents of Si, Al, Mn and Cr satisfy the relationship expressed by the following formula: (Si+Al) / Mn or (Si+Al) / (Mn+Cr)=0.74-1.26 and the steel sheet has a specified microstructure.

A Zn alloy plated steel sheet having excellent phosphatability and spot weldability and a method for manufacturing the same are provided. In the Zn alloy plated steel sheet including a base steel sheet and a Zn alloy plating layer, the Zn alloy plating layer includes, by wt%, Al: 0.5-2.8%, Mg: 0.5-2.8%, and a remainder of Zn and inevitable impurities, and a cross-sectional structure of the Zn alloy plating layer includes, by area percentage, more than 50% of a Zn single phase structure and less than 50% of a Zn-Al-Mg-based intermetallic compound. A surface structure of the Zn alloy plating layer includes, by area percentage, 40% or less of a Zn single phase structure and 60% or more of a Zn-Al-Mg-based intermetallic compound.

The invention relates to a surface treatment liquid for a plated steel sheet to be hot-processed. The present invention is a surface treatment liquid with excellent storage stability and is able to provide a surface-treated steel sheet for which the treatment coating formed has excellent water resistance, solvent resistance, adhesion to plated steel sheets, and hot lubricity as well as chemical conversion treatability after hot-pressing, corrosion resistance after coating, and spot weldability. The surface treatment liquid for a plated steel sheet that is to be hot-pressed comprises an aqueousZnO dispersion (A) and a water-dispersible organic resin (B). The aqueous ZnO dispersion (A) comprises water and ZnO particles, the particle diameter of which is 50-300 nm. The water-dispersible organic resin (B) has an acid value of 5-45 mg KOH / g and 5-300 nm emulsion particle diameter. The mass ratio (WA / WB) of the mass (WA) of ZnO particles in the aqueous ZnO dispersion to the mass (WB) of solids of the water-dispersible organic resin is 30 / 70 to 95 / 5.

The invention relates to steel for a 300MPa-grade automobile structural part and a production method for the steel. The steel comprises the following main components in percentage by weight: 0.06-0.08 percent of C, 0.05-0.09 percent of Si, 0.30-0.45 percent of Mn, 0.025-0.055 percent of Al, 0.015-0.025 percent of P, less than or equal to 0.006 percent of S, 0.010-0.019 percent of Nb, less than or equal to 0.006 percent of N and the balance of Fe and impurities. The production method comprises the production steps of molten iron desulfurization, converter smelting, ladle argon blowing, continuous casting, heating of a casting blank, hot rolling, winding, conventional pickling, cold rolling, continuous operation and flattening for later use. The production method disclosed by the invention has the advantages of short process flow, lower energy consumption and stable mechanical property; and in addition, on the premise that the yield strength of 300-340MPa and the tensile strength of 390-445MPa are met, the elongation percentage is not lower than 31 percent, the plastic strain ratio r is 1.45-1.80, a strain hardening index n is 0.16-0.20, a wide-cold test bending is 180 degrees and a bending diameter d is equal to 0; and in a metallographic structure, an equiaxed ferrite is 85-90 percent and a granular pearlite is 10-15 percent.

The invention provides a high-strength cold-rolled steel sheet having excellent stretch flangeability and spot welding property and a manufacturing method of the steel sheet. The steel sheet comprises 0.03-0.15% of C, 0.30-0.10% of Si, 1.20-2.20% of Mn, not more than 0.015% of P, not more than 0.010% of S, 0.02-0.15% of Al, not more than 0.005% of N, 0.20-0.60% of Cr, 0.010-0.060% of Nb, 0.030-0.100% of V and 0.0007-0.0050% of Ca, with the balance being Fe and unavoidable impurities, and with the (Mn+2Nb+V) being not more than 2.3% and not less than 1.6%. In the manufacturing method, the start rolling temperature of hot continuous rolling precision rolling is 1000-1100 DEG C, the finish rolling temperature is 890-950 DEG C, the acid-washing cold rolling rate is 60-80%, and two-stage cooling, namely slow cooling firstly and rapid cooling secondly, are adopted after annealing and temperature maintaining steps. The tensile strength of the finally obtained steel sheet is higher than 800 MPa. The obtained steel sheet is good in strength ductility matching, and excellent in stretch flangeability and spot welding property.

The invention provides high-strength anti-delayed fracture steel with a yield ratio of no more than 0.5. The steel comprises, by weight, 0.11 to 0.25% of C, 15.5 to 17.5% of Mn, 0.030 to 0.050% of Mo, 0.005 to 0.02% of Co, 0.005 to 0.009% of B, 0.009 to 0.011% of N and 0.011 to 0.025% of La+Ce+Nd. A production method for the steel comprises the following steps: desulphurization of molten iron; converter smelting; RH vacuum treatment; continuous casting; hot rolling, wherein finish rolling temperature is in a range of 755 to 790 DEG C; cold rolling, wherein a reduction rate is 51 to 54%; and continuous annealing. According to the invention, the problems of low elongation percentage, a high yield ratio and poor welding performance of high-strength steel of a same grade are overcome, and the phenomenon of delayed fracture is avoided; an automobile crash-proof part manufactured from the steel has better formability, welding performance and energy absorption performance compared with other cold-rolled high-strength steel, and use security, weight reduction performance and energy saving performance of a product are substantially improved; B, Mo, Co and N are employed, so refined crystalline strengthening and precipitation strengthening are realized, and a low yield ratio, heat resistance and corrosion resistance are guaranteed; a steel plate has double effects and a low yield ratio, and good forming capability, good bearing performance and anti-fracture performance of a material are guaranteed.

A method of manufacturing a high strength steel sheet. The method including casting a slab consisting essentially of 0.05 to 0.15% C, 0.5% or less Si, 1.00 to 2.00% Mn, 0.09% or less P, 0.01% or less S, 0.005% or less N, 0.01 to 0.1% Sol.Al, and a balance of Fe and inevitable impurities; hot-rolling the slab at a temperature of the Ar3 point or more; beginning cooling the hot-rolled steel sheet within 2 seconds after completing the hot-rolling at a temperature of from 750° C. to 600° C. at a cooling rate of 150° C. / s or more; holding the cooled steel sheet at a temperature between 750° C. and 600° C. for 2 to 15 seconds; cooling the steel sheet at a cooling rate of 20° C. / s or more; and coiling the cooled steel sheet at a temperature of 400° C. or less.