CS270861B1 - Microalloy low-carbon welding steel for metal-coated sheet-iron strips - Google Patents

Abstract

The micro-alloyed low-carbon weldable steel is designed for double or single-sided sheet-iron strips metal-coated with zinc or its alloys, primarily for the automotive industry and bended profiles with the basic composition of carbon up to 0.06 mass %, sulphur between 0.002 and 0.025 mass %, phosphorus from 0.005 to 0.035 mass %, manganese of 0.1 to 0.3 mass %, silicon between 0.05 and 0.2 mass % and aluminium from 0.03 to 0.08 mass %. Such steel contains alloying ingredients in the extent of 0.05 to 0.15 mass % of vanadium and between 0.008 and 0.1 mass % of nitrogen. As a benefit, this type of steel also contains 0.05 to 0.15 mass % of titanium and between 0.05 and 0.15 mass % of zircon. The rest is iron.

Description

The invention relates to microalloyed low carbon weldable steel intended for hot-rolled and cold-rolled metallized sheet metal sheets, in particular for the automotive industry and folded general purpose profiles, and to improve corrosion resistance to thermal and atmospheric erosion of sheet alone. .

For the mentioned purposes of using sheet metal, for example for bent profiles and in particular for car bodies and exhausts in the automotive industry, low carbon deep-drawing or cold-rolled structural steels are used. These steels, in addition to the disadvantageous mechanical properties, exhibit insufficient corrosion resistance to atmospheric influences and, in particular, to the effects of thermal influence on, for example, car exhausts. Even with the necessary plating for the above purposes, it is necessary to apply coatings of greater weight of about 275 g / m @ 2 on both sides, with relatively high surface roughness after cold rolling. The lack of corrosion resistance of these steels limits the possibility of one-sided plating of sheets solving pressing problems in the processing of, for example, body sheets. Unsuitable structure of materials, especially on the surface of sheets in the so-called. intermetallic phase, while not allowing the necessary adhesion and binding of the metallization coating to the sheet metal surface. These conventional steels, due to their unsuitable strength properties, and without special surface and heat treatment before or after plating of the sheets, require relatively large depths of the sheets for the said high-weight products, as well as reduced welding of the sheets so coated. The problem is partially solved by the development of plating materials and technologies.

The microalloyed low carbon steel according to the invention solves these problems. The principle of the invention is that microalloyed low carbon weldable steel with a basic carbon composition of up to 0.06%, manganese of 0.1 to 0.3%, silicon of 0.05 to 0.2%, aluminum of 0.03 to 0 , 08%, and 8 with a sulfur content of from 0.002 to 0.025% and a phosphorus of from 0.005 to 0.035 contains other alloying components in the range of 0.05 to 0.15% vanadium and 0.008 to 0.1% by weight of nitrogen. Preferably, the steel is further alloyed with titanium in the range of 0.05 to 0.15% and zirconium in the range of 0.05 to 0.15% by weight.

The advantages of the steel according to the invention are mainly that the formed low carbon steel exhibits a significantly higher corrosion resistance to both atmospheric and combined thermal influences, both without plating and after plating, which allows plating with a lower coating weight or a lower weight. one-sided plating suitable for demanding pressing eg car bodies. Appropriate alloying of steels improves the strength properties of sheets with the possibility of reducing the weight of the products made of them. In particular, however, by combining the anticorrosive components, namely silicon with the above-mentioned alloying elements, they simultaneously form a quaternary phase in the intermetallic surface layer with the zinc plating, but also with its alloys, including the zinc-aluminum alloy developed. metallized sheets without compromising their corrosion resistance. Steel also enables efficient and rational utilization of other processing technologies before and after metal plating.

An example of microalloyed steel according to the invention:

The steel contains 0.03% carbon, 0.3% manganese, 0.2% silicon, 0.015% sulfur, 0.016% phosphorus, 0.012% zirconium, 0.04% aluminum, 0.065% titanium, 0.055% vanadium and 0.011% nitrogen, the rest iron. and

Claims (2)

PRE-TREATMENT ’ 1. Micro-alloyed low-carbon weldable steel for hot-rolled and cold-rolled metal sheets on both sides or one-sided, in particular for the automotive industry, for example for exhaust pipes and bodywork and for general purpose bent profiles, zinc plating or alloys and / or with the addition of silicon and titanium CS 270 861 B1 or magnesium, with a basic carbon composition of 0,06% _f sulfur of 0,002 to 0,025%, phosphorus of 0,005 to 0,035%, of manganese of 0,1 to 0,3%, of silicon of 0,05 to 0, 2% and aluminum from 0.03 to 0.08% by weight, characterized in that it contains Salium alloying ingredients in the range of 0.05 to 0.15% vanadium and 0.008 to 0.1% nitrogen by weight. 2. A microalloyed steel according to claim 1, characterized in that it contains 0.05 to 0.15% titanium and 0.05 to 0.15% zirconium by weight.