CS240477B1 - Soothed steel for general use, especially deep-drawing and structural - Google Patents

Abstract

The invention relates to a quenched steel for general use, especially as a deep-drawing and structural steel, and solves the problem of universality in the production of casting and rolling of steel into cold and hot rolled products. The steel contains a maximum of 0.03% by weight of silicon and 0.0.2% each of sulfur and phosphorus, and further contains 0.02 to 0.06% of carbon, 0.1 to 0.3% of manganese, 0.015 to 0.035% of aluminum, traces of up to 0.004% of nitrogen and traces of up to 0.01% of total oxygen.

Description

The invention relates to calm steel for general use, in particular as a deep-drawing and structural steel, and solves the problem of the versatility of manufacturing steel casting and hot-rolling products. Steel is the most obsatiujúca / ₀ by weight. 0.03% silicon and after 0.0.2% sulfur and phosphorus, it also contains 0.02-0.06% carbon, 0.1-0.3% manganese, 0.015-0.035% aluminum, traces up to 0.004% nitrogen and traces up to 0.01% of total oxygen.

The invention relates to mild steel for general use, in particular as a deep-drawing and structural steel, and solves the problem of the universality of production, finishing, continuous casting and rolling of steels into cold and hot-rolled products.

In order to maximize the benefits of continuous steel casting, it is necessary, in addition to improving its own technology, to focus on peripheral technologies, which will bring both economic and qualitative effects, including direct supply of hot rolling mill through gates. For the sake of harmonization and simplification of the continuity of this connection, it is best to use continuously cast steel with the most general application. Such a steel! should meet at least the following: low carbon content with good depth and non-aging characteristics, sufficient ductility, good adhesion with metal coatings, i. j. suitability for hot rolled, cold rolled products and plated sheets at the same time. Oce! s-a must therefore be used where mild steels have been used for these specific properties or mild steels. In doing so, the frames intended for the direct sequence must not exhibit critical errors such as. cracks, clusters of impurities, tiny inclusions, etc., including the stability of the quality of the intermediate gates, especially without the appearance of bubbles. However, as is apparent from the specificity of the production of rough steels, from the point of view of their use for these purposes, they are not suitable, in particular because of the occurrence of cracks and inclusions in hot-rolled sheets, aging of the material, susceptibility to In calm steels, this is due to the poor adhesion of zinc with increasing aluminum and silicon content, the increased hardness of aluminum calibrated steel sheets and, last but not least, the necessity of a higher heating temperature in the ram furnace to dissolve and utilize the precipitation of aluminum and nitrogen in the solid solution.

The chemical composition of conventional low-carbon steels, especially those containing aluminum and silicon, is crucial for their classification in the group of restrained or non-restrained steels, which implies teehnology, in particular of stationary casting. In particular, the unsettled steel is in the classical sense of a variation of steel due to the course of the carbon reaction, which cannot be cast economically on a continuous casting machine. Thus, the effort is to continuously cast the steels as calm, but to achieve all the beneficial properties of changing the nature of the steel technology, which are essentially contradictory requirements.

One possible solution to this problem is to reduce the soluble aluminum content to a range of 0.008 to 0.04% by weight. the occurrence of bubbles and inclusions on the surface of the slab, but whose exceeding, common in calm steels, increases the content of metallic-aluminum, from the impurities of the aluminates present in the steel in the form of aggregates.

Another need is to provide a nitrogen content in% by weight. a maximum of 0.004% by its radical reduction, in particular the stricter regime of steel production, finishing and casting. The nitrogen content achieved so far from 0.007 to 0.01% for conventional steelmaking technologies can only be reduced by a complex of measures aimed at preventing the ingress of nitrogen, such as starting with an increased carbon content at the end of melt blowing - at least 0.05% in the pre-test; by insulating the contact of liquid steel with air from the converter to the continuous casting crystallizer - covers on casting vessels, vacuuming the steel within the secondary metallurgical complex, - using very pure argon, for homogenizing the steel In addition, the silicon content should be reduced below 0.03% by weight. in order to improve the galvanizing properties and, last but not least, to reduce the manganese content below 0.3% by weight: in particular to improve normal isisotropy, i. j. susceptibility of the steel to brittleness under red glow, which can be ensured by lowering the heating temperature of the gates in the ram furnaces. However, it is often required to develop steel 'which, after the well-known mopping treatment, can easily be cast into molds without lowering the required parameters.

Said drawbacks are overcome and the problem is solved by calm steel for general use, in particular as a deep-drawing and structural according to the invention. The principle of the invention consists in that the steel with a content in wt. 0.03% of silicon, 0.02% of sulfur and phosphorus, contains 0.02 to 0.06% of carbon, 0.1 to 0.3% of manganese, 0.015 to 0.035% of aluminum, traces up to 0.004% nitrogen and traces up to 0.01% of total oxygen.

The advantages of the invention are mainly that steel is produced which meets all of the above-mentioned requirements and is generally applicable both from the point of view of consumption and processing of products therefrom and secondly from the viewpoint of its production on modern modern production, finishing, continuous casting and rolling mills. direct sequence, without any major changes in the technology used and its variations. Steel is produced and processed with low energy consumption and material savings.

An example of a steel according to the invention:

Steel 'for general use, in particular for products made of hot-rolled and hot-rolled sheets. cold - contains in wt. 0.035% carbon, 0.20% manganese,

0.016% silicon, 0.015% phosphorus and sulfur, 0.02% aluminum and 0.0025% nitrogen. This steel has the following values: Re = 238 MPa, RM = 345 MPa and As = 35.5 θ / ο.

Claims (1)

240477 5 0.016% silicon, 0.015% phosphorus and sulfur, 0.02% aluminum and 0.0025% nitrogen. This steel has values: Re = 238 MPa, RM = 345 MPa and As = 35.5 θ / ο. SUBSTRATE Quenched steel for general use, especially as deep-drawing and structural, containing at most /% by weight. 0.03% sulfur and 0.02% sulfur and phosphorus, characterized in that it contains from 0.02 to 0.06% carbon, 0.1 to 0.3% by weight, aluminum, traces of up to 0.004% of nitrogen and traces of up to 0.01% of total oxygen.