RU2323261C2 - Alloy steel producing method - Google Patents

Abstract

FIELD: steel metallurgy, namely processes for melting converter chrome-containing alloy steel.

SUBSTANCE: method comprises steps of adding to steel melt ferromolybdenum and nickel after intermediate slagging off; draining metal from converter to ladle while successively adding to ladle aluminum, part of ferrochrome, ferrosilicon, silico-manganese and second part of ferrochrome; dividing charge of ferrochrome by said parts at relation (0.9 - 1.1): (0.9 - 1.1); heating ferroalloys in furnace till temperature of their upper layers no less than 700°C; providing relation of temperature of lower layers of ferroalloys to temperature of their upper layers no less than 0.25.

EFFECT: less loss of yield of high-quality steel, lowered expenses for producing steel.

4 cl, 1 ex

Description

The invention relates to the metallurgy of steel and can be used in the production of converter alloyed, chromium-containing steel. Metal is smelted in top-purged oxygen converters. In this case, after an intermediate slag download, alloying elements are introduced into the steel melt in a predetermined quantity, and after the steel is drained from the converter into the ladle, the necessary ferroalloys are usually introduced into the latter. Some features of the converter steel production technology are described, for example, in the book of V.K.Babich et al. "Fundamentals of metallurgical production (Ferrous metallurgy)", M., "Metallurgy", 1988, pp. 60-72.

There is a known method for the production of molybdenum-containing steel, in which the melt is purged with oxygen, and after filling a certain volume of the ladle with cast steel, molybdenum concentrate, deoxidizers, and also chromium and manganese are introduced into it (see AS USSR No. 160/135, class C21C 7 / 06, 5/28, published in BI No. 39, 1990). However, this method is not acceptable for the production of chrome alloyed converter steel.

The closest analogue to the claimed method is the production technology of converter chromium-nickel-molybdenum steel, presented in the collection of works of the Central laboratory of OJSC MMK "Improving the technology in OJSC MMK, issue 9, Magnitogorsk, Printing House, 2005, p.41-49.

This technology for the production of steel with a chromium content from 1.4 to 1.9% includes the introduction of ferromolybdenum and nickel into the steel melt after an intermediate slag download, the metal is drained from the converter to the ladle and is characterized in that pig iron is desulfurized to a sulfur content of 0.007%, and at the time of melting in the ladle, about 3% (of the weight of steel in the ladle) of high-chromium ferrochrome is planted in it.

A disadvantage of the known technology is its unacceptability for the production of alloy steel with a chromium content of more than 1.9% due to increased metal waste and production costs.

The technical task of the present invention is to increase the yield of steel and reduce costs in the production of alloy steel with a chromium content of up to 2.3%.

To solve this problem, a method is proposed for the production of alloy steel in a converter with a chromium content of up to 2.3%, which includes introducing ferromolybdenum and nickel into the steel melt after intermediate loading of slag from the converter and pouring metal into the ladle, in which aluminum, part of ferrochrome, is successively introduced into the ladle. , ferrosilicon, silicomanganese and the second part of ferrochrome, a portion of which is divided into these parts in the ratio (0.9 ... 1.1) :( 0.9 ... 1.1), while the ferroalloys introduced into the ladle are heated in an oven to the temperature of their upper layers less than 700 ° C, the ratio of the temperature of the lower layers of the ferroalloys to the temperature of their upper layers is at least 0.25, and ferromolybdenum can be added to the ladle.

The above parameters of the proposed method are determined empirically and are empirical.

The essence of the proposed technical solution is to optimize the technology for smelting alloy steel in a converter with a chromium content of up to 2.3%, namely: in a certain sequence of operations that comprise the process, heating temperatures of different layers of ferroalloys introduced into the ladle during steel casting, as well as in the ratio of these temperatures. As a result of this, it becomes possible to melt in the converter high-quality alloy steel with a chromium content of up to 2.3%, previously melted in an open-hearth furnace. This increases the yield of metal and reduces production costs.

An experimental verification of the proposed method was carried out in the oxygen-converter shop (CCC) of OJSC "Magnitogorsk Iron and Steel Works".

For this purpose, in the production of alloy steel with up to 2.3% (inclusive) chromium content in it, the sequence of introducing aluminum and ferroalloys into the ladle was varied (moreover, the ferrochrome batch was divided into two parts of different volumes), the final heating temperature of the upper layers of ferroalloys was changed, and the ratio of the temperatures of their upper and lower layers and assessed the possibility of additional introduction into the melt or ladle of ferromolybdenum.

The best results (quality steel yield of about 100%) were obtained using the proposed method. Deviations from its optimal parameters worsened the results achieved.

So, with a different sequence of introducing aluminum and ferroalloys into the bucket (different from the recommended one - see above), as well as with a different ratio of parts of the ferrochrome hitch, the yield of high-quality steel did not exceed 70%. The yield within 75 ... 95% was also with the use of ferroalloys heated to a temperature of less than 700 ° C, and with a ratio of the temperatures of their layers less than 0.25. A change in the ratio of parts of the sample, a decrease in the temperature of the upper layers less than 700 ° C, a change in the ratio of the temperature of the lower layers to the temperature of the upper layers less than 0.25 led to the formation of sintered cake of ferroalloys in the ladle, which in turn reduced the yield of steel.

It was found that the determining part of the recommended technology is that which is described in claim 1 of the claims of this invention.

A check of the technology, taken as the closest analogue (see above), showed that when it is used, the yield of high-quality alloy steel with a chromium content of up to 2.3% does not exceed 65%. Thus, the experiments confirmed the acceptability of the technical solution found to achieve the goal and its advantages over the known object.

Technical and economic studies carried out at the Central Laboratory of OJSC MMK showed that the introduction of the developed technology in the CCC plant in the production of the above steel will increase the yield of high-quality metal by at least 30% while reducing production costs (compared with open-hearth production) by almost 10%.

EXAMPLE OF SPECIFIC PERFORMANCE

Alloy steel with a 2.1% chromium content is smelted in an oxygen converter.

Alloying of steel is carried out by additives of ferroalloys of fractions of 20 ... 80 mm into the steel pouring ladle, which are supplied with heating of their upper layers to 720 ° C, and heating is carried out with natural gas for 15 ... 20 min. The ratio of the temperature of the lower layers of ferroalloys to the temperature of their upper layers is 0.32.

When steel is drained, aluminum, the first part of ferrochrome, ferrosilicon, silicomanganese and the second part of ferrochrome, the weight of which is divided into these parts in a ratio of 1: 1, are successively introduced into the ladle.

Ferromolybdenum is additionally introduced into the bucket.

Claims (4)

1. A method of producing alloy steel in a converter with a chromium content of up to 2.3%, comprising introducing ferromolybdenum and nickel into the steel melt after intermediate loading of slag from the converter and pouring metal into the ladle, in which aluminum, part of ferrochrome, ferrosilicon is successively introduced into the ladle, silicomanganese and the second part of ferrochrome, while a weighed portion of ferrochrome is divided into these parts in the ratio (0.9 ... 1.1) :( 0.9 ... 1.1). 2. The method according to claim 1, characterized in that the ferroalloys introduced into the ladle are heated in the furnace to a temperature of their upper layers of at least 700 ° C. 3. The method according to claim 2, characterized in that the ratio of the temperature of the lower layers of the ferroalloys to the temperature of their upper layers is at least 0.25. 4. The method according to claim 1, characterized in that ferromolybdenum is additionally introduced into the bucket.