BRPI0803913A2 - new technology for the production of high copper and low manganese skating steels, presenting technological, economic and environmental advantages - Google Patents

Abstract

The present invention is a new steel technology based on precipitation of copper sulphides in substitution of manganese sulphide (MnS). From this foundation, new types of steels are presented with economic, technological and environmental advantages. Briefly, these steels are grouped into two families, namely: 1 - "ECOS" or "GREEN" - These steels are named after the fact that they can be made from highly contaminated scrap with copper to avoid discarding. this scrap in the wild; 2 - "ACOS COMINELI" - PATINAVEL steels - In this family, high copper and low manganese steels have little or no manganese sulphides and sulfur is stabilized by copper. In these steels, high copper gives high corrosion resistance and copper sulfide increases mechanical properties (tensile and impact strength); The economic advantage is conferred by the use of copper contaminated scrap, the non-addition of manganese and the absence or even unnecessary addition of nickel to control hot brittleness during manufacture.

Description

"NEW TECHNOLOGY FOR PRODUCING HIGH COPPER AND LOW MANGANESE STEELS WITH PRESENTABLE TECHNOLOGICAL, ECONOMIC AND ENVIRONMENTAL ADVANTAGES".

Presentation

The present invention relates to a new technology for producing steels with better mechanical properties, corrosion resistance and reduced cost for application to welded, bolted or riveted structures and exposed to atmospheric or marine corrosion without the need for painting. The basis is to replace manganese, as a sulfur stabilizer, with copper, taking advantage of the technological benefits of substitution, and also enable the use of highly contaminated copper steel scrap, preventing it from being discarded in nature.

Description - Scientific bases for the requestTechnological and Environmental:

Nowadays environmental and cost reduction requirements are increasingly important in materials. Recyclability and low cost can determine the success of a new material, as these are complementary attributes that can help reverse Earth's tendency to environmental degradation.

Metals in general, and particularly steel, are materials of good recyclability.

However, the contamination of scrap by some elements such as copper from electro-electronic components contained in discarded household appliances and automobiles can make their reuse more expensive or even render these scrap unavailable and discarded in nature.

With the tendency for efficiency and size reduction of these electro-electronic components, copper contamination in scrap metal tends to be even more difficult to separate. In this way the problem only tends to get worse, as copper increases in steels made from scrap.

Once present in liquid steel, copper is an element that cannot be removed by processing this steel and will inevitably be present in the solidified product. This element can cause brittleness problems during hot processing of steel (continuous casting or rolling). Therefore, if this problem occurs, the amount of copper in steels must be tightly controlled or its effects should be offset by the addition of nickel, which can make the final product much more expensive. As a result, copper-contaminated scrap may have very limited use and must be discarded in nature. On the other hand, copper also confers interesting properties in steels, increasing its mechanical strength, corrosion resistance and impact resistance, which makes it a important element in the league.

French patent application No. 02/00387 of 14/01/2002 deals with the manufacture of a copper-containing steel product, the purpose of which is solely to increase mechanical properties via precipitation precipitation of copper that is supersaturated in ferrite. Indeed this phenomenon of aging is possible and well known in science. However, the proposed process of product production (direct solidification - or continuous casting - of a sheet up to 10mm thick and other procedures) is outside the current industrial reality. In any case, what the inventor intends absolutely does not conflict with the present request, since they are totally different approaches. What the applicant proposes is a way to produce aging, based on thermomechanical processing, without worrying about manufacturing problems. Already the present invention is focused on altering the chemical composition in order to produce the same end results of mechanical properties, but with clear economic advantages, environmental technologies, all within a totally possible manufacturing reality.

The present application consists of the results of many years of research in order to solve the problem of hot shortness in the manufacture of undesirables, allowing it to be cheapened by reducing the addition of alloy elements such as manganese and nickel. In addition, the process allows for the creation of an "ECOLOGICAL STEEL" or "GREEN STEEL" because of the increased copper dowel in steel to allow the use of highly contaminated scrap with copper that would otherwise be discarded in nature.

Producing higher copper steels with less alloying elements will reduce costs and give better mechanical properties and corrosion resistance. It also makes it possible to reduce the weight of the structures, by increasing the mechanical resistance and increasing their corrosion life, without painting. These steels are called WEATHERING STEELS which are used in metal structures exposed to time.

Scientific background

The scientific basis of the request is based on the results of scientific work performed by the applicant in Brazil and abroad. It is the fact that it is necessary to control the amount of sulfur, which is a harmful element for causing hot brittleness in these steels. Therefore to control the sulfur sulfide, manganese is added which will stabilize sulfur in the form of sulfur sulfide inclusions (Mns) within the steel and prevent its harmful effects. It turns out that copper is also a copper sulfide builder and therefore It can also stabilize the sulfur. However, in the presence of MnS, the copper present in the corn will compete for sulfur, concentrate around the inclusions and form a secreted copper rich region. This phenomenon is of fatal importance because of hot brittleness, as copper will be liquid at the process temperature. To compensate for the problem, nickel is added to reduce hot brittleness. Reducing or even eliminating the addition of manganese and increasing the addition of copper will lead to the formation of copper sulphide, with less possibility, or even absence of MnS formation. Copper sulphide has mechanical strength enhancing properties because it is very small in size. In this way the sulfur is stabilized and the copper will become solution and not secreted. Thus the problem of hot brittleness can be reduced or eliminated and therefore no nickel addition is required. Therefore, the harmful effect of copper segregation is controlled and the benefits of its addition can be reaped both in technological properties and in allowing better scrap recycling.

Claims (6)

1. - Rollable copper (Cu) iron alloy steel and other elements in any composition to permit the stabilization of the sulphides wholly or partially by the formation of copper sulphide and to reduce or eliminate MnS appreciation. In this new technology, steel will have better mechanical properties and increased corrosion resistance, both due to the presence of copper, and will be easier and cheaper to manufacture, given that there is no addition of manganese and that the added copper will come from the contamination of the copper. waste. Also, knowing that co-segregates around MnS inclusions, reducing the amount of MnS will reduce copper segregation. Therefore, since no segregation is found, which is the cause of hot brittleness, the addition of nickel will be smaller, or even unnecessary, to avoid this problem. 2. - Rollable iron (steel) alloys containing% Mn below 0,5% and% Cu in quantities greater than manganese (% Mn:% Cu <1 ratio) and other elements in any other composition. The reduction of manganese is intended to facilitate the stabilization of sulfur by copper by carrying out the advantages cited in claim 1; 3. - "ECOLOGICAL STEEL" or "GREEN STEEL" (Iron alloy - skid steels) produced wholly or partly from copper-contaminated scrap steel. This steel will have the manganese content only from scrap and nickel5 below 1% and other elements in any other composition. Nickel is added only because of the negative effects caused by segregation of copper around MnS inclusions, as it is unlikely to have manganese-free steel scrap. Reducing the amount of nickel manganese may also be reduced, allowing as described in claim 1. 4. - Iron (steel) alloys where the amount of manganese is less than copper and sulfur less than 0.004% (S <0.004%) and other elements in any other composition. In this case, again the reduction of manganese will allow for sulfur stabilization by copper and the described in claim 1 to occur. 5. - Iron (steel) alloys where the amount of nickel is lower than that of copper and two elements in any other composition. These steels will certainly have to be grounded in the principles of the invention, as little nickel addition in copper or less than copper will only be possible if described in claim 1. Otherwise the hot brittleness problem will occur. 6. - "COMINELI STEEL" (Ferro-steel alloys) without added manganese, or with manganese only from residual contamination, produced from sponge iron (direct reduction), with or without added scrap, therefore also containing low content of residual sulfur. As it is a steel made from sponge iron (direct reduction) the carbon is also residual and can be stabilized with the addition of niobium or titanium. These steels, as they are practically manganese free and the sulfur is very low, will still be practically free of MnS inclusions which are the breakdown points. Thus they may have high levels of copper, as this way there will be no segregation of copper around the inclusions. Thus, the addition of nickel will be unnecessary or small, as described in claim 1. Still, besides few inclusions, the steel will have predominantly ferritic structure, which will result in high fracture toughness. The mechanical properties (tensile and impact strength) and corrosion resistance of this steel should be very suitable for onshore and offshore uncoated applications at low temperatures and atmospheric corrosion of these environments.