RU2363736C2 - Method and charge for manufacturing of structural steel with reduced hardenability - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy field, particularly to manufacturing of structural steel. Method includes loading into steel-making vessel of metallic charge consisting of breakage, introduction of slag-formings, pouring of semi-product of carbonaceous or blast-furnace conversion pig iron, skimming of slag, melt heating up to the temperature of finish beginning, finish of melt by content and temperature, slag content correction during the melting process, deoxidation of metal by aluminium and introduction of titanium or its alloys. Melting process is implemented in oxygen steel-making converter made of metallic charge, including 15-20 wt % of scrap and 80-85 wt % of semi-product of carbonaceous or blast-furnace conversion pig iron, with limited amount of manganese, silicon and chrome, providing by melting content of each in melt not more than 0.1%, metallurgical scrap with content in it of chrome, nickel and copper, providing by melting content of each in melt not more that 0.1%. Metal is deoxidated and alloyed in unit furnace-ladle by aluminium and titanium or its alloys, which are introduced with consumption, providing in finish metal content of aluminium 0.02-0.06% and titanium 0.06-0.10%.

EFFECT: invention usage provides steel manufacturing with reduced hardenability in oxygen steel-making converter.

3 cl, 1 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular the production of structural steels with reduced hardenability (PP), obtained in oxygen converters (CC), and intended for hardening critical, heavily loaded machine parts by volume-surface hardening.

State of the art

There is a method of producing structural steel with reduced hardenability in an open-hearth furnace, including loading a metal charge from an iron-carbon alloy and scrap with a regulated content of chromium, nickel and copper taken in calculated quantities into the open-hearth furnace, introducing slag-forming materials, heating and melting the charge, and downloading slag , heating the bath to the start-up temperature, fine-tuning the melt in composition and temperature during polishing and clean boiling, adjusting the composition of the slag during polishing and clean boiling, deoxidation of metal in the furnace and during the release of the spill into the bucket or in the bucket with aluminum and the introduction of silicon and its alloys. As a metal charge, an iron-carbon alloy and scrap are used with a content of chromium, nickel and copper, which provide more than 0.1% of melting, while adjusting the composition of slag during polishing and clean boiling is done by downloading from the furnace some slag and periodic additives of slag-forming materials to ensure that in the melt upon release the manganese content is not more than 0.1%, the metal is deoxidized with aluminum and titanium alloy, which are introduced at a rate that ensures that the finished metal contains 0.03-0.1% aluminum and 0.06-0 titanium, 12%, and silicon and its alloys are introduced into the melt after its deoxidation with aluminum and titanium alloy (see No. 2164536, IPC С25С 5/04, 7/06, bull. No. 9, 2001). This invention is taken as a prototype for the charge and the proposed method.

It is known that the processes of limited hardenability became determined by the main factors:

1. The chemical composition of steel having a minimum content of manganese, silicon, chromium, nickel and copper.

2. The purity of the metal for non-metallic inclusions.

3. The technology of steel smelting, deoxidation and casting.

In sum, these factors should limit the growth of austenite grain in the process of heating the metal for hardening, thereby ensuring minimum grain sizes in hardened steel.

The above-described technology for the production of steel with reduced hardenability (PP) in open-hearth furnaces operating with a scrap-ore process provides, on the whole, the conditions for obtaining rolled products in accordance with the given mechanical properties, but has a number of significant drawbacks:

- the chemical stability of the metal is not ensured not only in individual melts, but also in the metal of one melting (Δ in the content of [Mn], [Si], [Cr] reaches 0.01-0.03%, [Al] ~ 0.05%). A significant run-up in the content of elements in steel does not ensure uniformity of metal hardenability;

- the purity of the metal is not ensured by non-metallic inclusions (N.V.), point heterogeneity (T.N.), central porosity (C.P.), and the integrity of the surface of the rolled products.

The presence of non-metallic inclusions and metal defects reduces the level of mechanical properties of the finished product, and violations of the requirements during casting lead to a significant increase in waste in the form of scrap when rolling ingots.

Two of these factors are due to the impossibility of high-quality mixing of metal in steel pouring ladles, refractory lining of steel pouring ladles and steel casting technology in the conditions of the existing workshop.

Disclosure of invention

The objective of the invention is the development of technology for the production of steel (with reduced hardenability in oxygen converters with further processing of metal on the ladle furnace (CCP) and casting steel on continuous casting machines (CCM) and the elimination of the disadvantages of the prototype.

The problem is solved using the signs specified in the 1st paragraph of the claims, namely, a method for the production of structural steel with reduced hardenability, including loading a metal charge consisting of scrap into the steelmaking unit, introducing slag-forming materials, pouring the intermediate carbon or blast furnace pig iron, downloading slag, heating the melt to the temperature of the start of refinement, refinement of the melt in composition and temperature, adjusting the composition of the slag during the smelting process, deoxidation of metal aluminum and the introduction of titanium or its alloys, while the steel melting process is carried out in an oxygen converter from a metal charge, including 15-20 wt.% scrap metal and 80-85 wt.% of the intermediate product of carbon or blast furnace pig iron, and the melt is finished according to temperature and content carbon, deoxidation and alloying of metal is carried out at the ladle furnace with subsequent metal processing on a vacuum.

According to paragraph 2 of the claims, the metal is deoxidized and alloyed in the ladle furnace with aluminum and titanium or its alloys, which are introduced at a flow rate that provides 0.02-0.06% aluminum and 0.06-0.10% titanium in the finished metal .

The problem is solved using the signs specified in the 3rd paragraph of the claims, namely, the mixture for the production of structural steel of low hardenability, consisting of a carbon intermediate obtained after the devanization of vanadium cast iron or blast furnace pig iron with a manganese content of not more than 0.5 % and metal scrap with the content of chromium, nickel and copper in it, which ensure that each melt in the melt does not exceed 0.1% by melting, and distinctive essential features, such as intermediate carbon contains a limited amount of manganese, silicon and chromium, which, when melted, ensure that the content of each in the melt is not more than 0.1%, with the following ratio of components wt.%:

Scrap metal 15-20 The intermediate product is carbon or pig iron 80-85

If we take the components of the charge less or more of the specified limits, then the increase in strength and service properties of steel is not achieved by ensuring the uniformity of the metal for a given chemical composition.

The technical result of the invention is to simplify the process, increase the strength and service properties of steel by ensuring the uniformity of the metal for a given chemical composition, as well as reducing the consumption of metal for hire.

The invention is illustrated in the drawing, which shows a diagram of a steel production line.

The technological line for the production of structural steel of low hardenability includes the following units installed in series: an oxygen converter 1, a ladle furnace 2, a vacuum degasser 3, and a continuous casting machine or mold 4.

An example embodiment of the invention.

In oxygen converter 1, metal scrap is loaded in an amount of 15% by weight of the heat when using carbon intermediate in the amount of 85% by weight of the heat or 20% of scrap by weight of the heat when using blast furnace pig iron, taken respectively in an amount of 80% by weight of the heat.

As scrap metal, waste from the production of steel 15-rim, the content of elements, wt.%: Carbon 0.08-0.17; manganese not more than 0.4; silicon not more than 0.1; sulfur not more than 0.03; phosphorus no more than 0,035; chrome, nickel, copper no more than 0.25 each. TU 14-115-67-2007, TU 0951-3000186341-2007, TU 11-115-1-2002, TU 14-115-9-2002. ChMZ OJSC.

Wastes from the production of steel with reduced hardenability with the content of elements wt.%: Carbon 0.60-0.67; manganese no more than 0.2; silicon not more than 0.2; sulfur, phosphorus no more than 0,030; chrome, nickel, copper, not more than 0.10 of each TU0950-005-00186-341-2002.

Wastes from the production of steel 3sp with the content of elements, wt.%: Carbon 0.14-0.22; manganese 0.4-0.65; silicon 0.15-0.30; chrome, nickel, copper, not more than 0.30 each; GOST 380-94, and scrap of other steel grades, providing the content in the melt of manganese, chromium and copper by melting no more than 0.10 wt.% Each.

As slag forming lime is used.

As a carbon-containing material, a carbon intermediate STP 115-28-2003 is used, which is obtained as a result of vanadium cast iron devanadation, element content, wt.%: Carbon not less than 4.2; manganese not more than 0.010; chrome no more than 0.10; vanadium not more than 0.10; silicon not more than 0.10; sulfur not more than 0.04; phosphorus no more than 0.05; titanium is not more than 0.02, the rest is iron.

Redox cast iron with a manganese content of not more than 0.5% is used as the carbon-containing material.

The composition of the mixture wt.% 1st squad 2nd squad Scrap metal fifteen twenty Intermediate carbon 85 - Pig iron - 80 one hundred one hundred

The weight of the poured intermediate of carbon or pig iron is 80-85% of the weight of the heat.

The metal in the converter is purged with oxygen to the carbon content in the alloy and the melt temperature necessary to ensure fine-tuning at the ladle furnace (UPK) 2. The metal ready for processing at UPK 2 should not contain harmful impurities in amounts of more than 0.10% everyone. The low content of impurities [Mn] and [Cr] is ensured by the discharge of slag from the converter and the induction of new slag by feeding slag-forming materials (W.O.).

Finishing metal by chemical composition and temperature is carried out on a ladle furnace (CCP) 2, deoxidation is carried out by feeding aluminum into the melt in the form of wire (wire technology) and titanium (or its alloys) in the form of pieces or wire with a flow rate that ensures in the finished metal, the content of aluminum is 0.02-0.06% and titanium 0.06-0.10%.

At the same time, the metal is mixed with an inert gas (argon) and the carbon content in the finished steel is adjusted (wire technology for carburizing steel). The metal is heated using graphite electrodes inserted into the cover of the code 2.

Metal processing at the “ladle-furnace” installation guarantees the production of steel that is homogeneous in a given chemical composition over the entire volume of the ladle and with a minimum temperature that ensures casting of steel. After processing on UPK 2, the metal in the ladle is closed with a special lid or heat-insulating mixtures. A metal bucket is mounted on a vacuum degasser for metal degassing. Next, a vacuum is created in the vacuum vessel 3 to release gases from the metal.

The proposed technology provides the production of steel grades of PP with the content of elements, wt.%: Carbon 0.50-0.85; manganese not more than 0.15; silicon not more than 0.15; chrome, nickel, copper, not more than 0.10 each; aluminum 0.02-0.06; titanium 0.06-0.10, the rest is iron.

Finished steel is cast at CCM 4 or into the molds according to the technological instructions in force at Chusovskaya Metallurgical Plant OJSC. The use of slag-forming mixtures with any casting method is mandatory.

The proposed technology for the production of steel with reduced hardenability ensures metal uniformity in a given chemical composition, and casting conditions (steel ladles with lining with refractory materials of the corresponding grades, the use of slag-forming mixtures) ensure metal purity according to N.V. and lack of metal defects.

The introduction of a new technology for the production of steel with reduced hardenability guarantees an increase in the service characteristics of the finished product, and a reduction in the consumption of metal during rolling.

From the description and practical application of the present invention, specialists will be obvious and other private forms of its implementation. This description and example are considered as material illustrating the invention, the essence of which and the scope of patent claims are defined in the following formula by a combination of essential features and their equivalents.

Claims (3)

1. A method of manufacturing structural steel of low hardenability, including loading a metal charge consisting of scrap into a steelmaking unit, introducing slag-forming materials, pouring a semi-product of carbon or blast furnace pig iron, downloading slag, heating the melt to the temperature of the finishing stage, adjusting the melt in composition and temperature, and adjusting the composition of the slag during the melting process, the deoxidation of metal by aluminum and the introduction of titanium or its alloys, characterized in that the steel melting process is carried out in an oxygen envelope e from a metal charge, including 15-20 wt.% scrap metal and 80-85 wt.% of the intermediate product of carbon or blast furnace pig iron, and melt refinement by temperature and carbon content, metal deoxidation and alloying are performed on a ladle furnace with subsequent processing metal in the vacuum. 2. The method according to claim 1, characterized in that the metal is deoxidized and alloyed in the ladle furnace with aluminum and titanium or its alloys, which are introduced at a rate that provides the aluminum content of 0.02-0.06 wt.% In the finished metal and titanium 0.06-0.10 wt.%. 3. The mixture for the production of structural steel of low hardenability, consisting of a carbon intermediate obtained after the devanization of vanadium cast iron, or blast furnace pig iron with a manganese content of not more than 0.5 wt.% And metallurgical scrap containing chromium, nickel and copper providing, upon melting, the content of each of them in the melt is not more than 0.1 wt.%, characterized in that the carbon intermediate contains an amount of manganese, silicon and chromium, providing each content on melting of them in the melt is not more than 0.1 wt.% in the following ratio of the components of the mixture, wt.%:
scrap metal 15-20 intermediate carbon or pig iron 80-85