Galvanized rolling-hardened cold-rolled flat product and process for producing it

Abstract

A flat product according to the invention which has been produced from a low-alloy steel containing iron and unavoidable impurities together with (in % by weight) up to 0.45% of C, up to 2.20% of Si, up to 2.50% of Mn, up to 0.12% of P, up to 0.025% of S, up to 2.0% of Al, up to 0.15% of Ti, up to 0.09% of Nb, a total of up to 1.0% of Cr and Mo, up to 0.2% of V and up to 0.005% of B and has been cold-rolled to a thickness of 0.1-4 mm and is in the rolling-hardened state has a tensile strength of 700-1000 MPa and is coated with a zinc layer which has been applied by electrolytic galvanization and has a layer thickness of up to 12 [mu]m. The cold-rolled flat product of this type provides a steel sheet or strip which has not only a particularly high strength but also a high corrosion resistance. In addition, the invention provides a process for producing such a flat product.

Description

technical field [0001] The present invention relates to a cold-rolled galvanized sheet produced from low-alloy steel, such as a high-strength cold-rolled strip or cold-rolled steel sheet, and a method for producing the sheet. Background technique [0002] In the steelmaking industry there is a need for economical thin steel plates which are light in weight and suitable for applications where high strength is the most important factor and in all cases the formability and ductility of the steel sheet handling are secondary conditions application occasions. An example of such an application is the manufacture of profiles for doors and gates. In particular, sheet steel of the type considered here needs to be processed into sheet metal for the manufacture of roller shutters, roller shutters or other similar components. [0003] Another example of the use of this type of sheet steel considered here is the manufacture of transmissions or clutches, where light and high-strength ec...

AI Technical Summary

Problems solved by technology

[0007] While the document JP 10176253A describes an attempt to minimize the reduction in tensile strength induced during hot-dip galvanizing, in which the strip entering the zinc bath in individual sections is only achieved by intensive concentrated induction heating just before it enters the zinc bath required temperature, but the resulting necessary equipment and control technology costs are so high that in practice the known method proves to be uneconomical