SU1257097A1 - Method of steelmaking from chromium-treated iron in converter - Google Patents

Abstract

The invention relates to ferrous metallurgy and can be used in the production of steel in oxygen converters from chromium iron. In order to increase the yield of chromium in terms of chromium content and increase productivity, intermediate slag is downloaded with a minimum chromium content in the metal. For this purpose, the purge in the first period is carried out at the position of the tuyere 25-33 of the calibres given, and the pshka is downloaded by using 35–40 pig iron at a content of 26–32% FeO in the slag and the melt temperature 1400–1440 ° C. The amount of slag being drawn is 90-120 kg / ton steel. 2 tab. i SL

Description

one

The invention relates to ferrous metallurgy, in particular to the production of steel in oxygen converters from chromium iron,

The purpose of the invention is to increase the yield of chunks for chromium content and increase productivity.

When using the invention, chromium is more fully oxidized in the first period, the chromium content at the end of the second period is less than 0.25%, the blow-outs for chromium are eliminated and, as a result, the productivity of converters is improved. This is achieved due to the optimal blowing, temperature, and slag regimes of the first period, which ensure the maximum removal of chromium into the slag and the production of a liquid-mobile, easily-pumped slag with foam oxidation and basicity.

The essence of the invention is that in order to obtain the mark content of chromium and steel less than 0.25, the intermediate slag is downloaded with the minimum content of jxpoMa in the melt and the optimum amount of liquid foamy slag with a sufficiently high oxidation and basicity.

Studies have shown that the position of the minimum on the kinetic curve of the chromium design change along the purge path is observed in the range after oxygen consumption in the amount of 35-40 m / t of pig iron. Earlier loading of slag is not feasible due to the high silicon and chromium content in the melt and the low temperature slag from - for insufficient temperature (less than 1400 C). By the consumption of oxygen of 40 cast iron, slag loading is difficult, since at a melt temperature of more than 144 COP

Indicators

0.04-0.08 0.09-0.10 0.14-0.15

0.28 29.7

2.7

570972.

the decarburization rate increases dramatically, which leads to a decrease in the content of ferrous oxide in the slag (less than 26% FeO) and reduction

5 chromium from slag to metal. In this case, after stopping the blowing, intense boiling of the metal is observed, which leads to difficulty in converting the converter and additional metal loss when loading thick chromic slag.

The choice of the working position of the tuyere 25-33 of the calibers given is due to the need to obtain highly co-oxidized basic slags and a low chromium content in the melt on an intermediate level. Thus, at the position of the tuyere 25 of the above calibers, the content of FeO in the slag in the medium 20 is 26.2%, the chromium and silicon in the melt are 0.38 and 0.08%, respectively, and at the end of the purge the content of chromium is 0.24% . The lower position of the tuyere is impractical25 but. With the position of the tuyere more than 33 calibers given, due to the high oxidation of the slag (FeO more than 32%), emissions are observed and the blowing should be stopped earlier than planned.

3Q of time, which leads to a high content of chromium and silicon in the melt, increased loss of iron when downloading slag, etc.

The optimum lime consumption for obtaining sufficient liquid slurry highly basic slag is 70-80 kg / t of pig iron for each percent of silicon in the iron. With a lime consumption of less than 70 (% Si) ,, yp kg / t

. the iron content of silicon, and consequently, chromium in the metal, is obtained, respectively, more than 0.08 and 0.40%.

Table 1 presents the effect of silicon on the chromium content in the melt in the first period. Table 1

The content of silicon,%

0.59 19.8

 1.75

3

, With a lime consumption of more than 80 (ZSi) y kg / t of iron, the slag does not foam well, which makes it difficult to download and removes chromium and slag. Since the chromium content and the silicon content in the pig iron are interrelated (as the silicon content increases, the chromium content also increases), the lime consumption takes into account the change in the chromium content in the cast iron.

When slag is loaded less than 90 kg / t of steel in the second period, chromium is reduced from slag, and at the end of the purge, the chromium content in the metal exceeds 0.25%. By downloading slag of more than 120 kg / t, the mechanical loss of metal increases, the melting cycle lengthens, and the yield of liquid steel decreases.

It is necessary to emphasize that the limit of chromic CAST IRONS in OTJ

For example, from phosphorous cast iron it is very sensitive to measuring technological parameters, i.e. the deviation from the optimal values of even one of the basic parameters, as a rule, leads to unsatisfactory results.

The technological indicators of the process with different variants of chromic iron redistribution are presented in Table 2.

T a b l i

a25

at

1.45

Oh 78

55.2

Continuation of table 2

Example 1 In order to carry out the method of producing steel from chromium iron, smelted on NTMK from Cuban iron ore, experimental smelting was carried out in a 10-ton converter at an oxygen consumption of 40 m / min. 2 tons of scrap were poured into the converter and 8.0 tons of pig iron were poured with the content,%: carbon A, 6; silicon 0.8; manganese 0.82; chromium 1,44 j nickel 0,29; sulfur 0.035; phosphorus 0.10 cobalt 0.09. During the first 3 minutes of purging, 450 kg of lime and 25 kg of fluorspar were added, and then, within 5-6 minutes of blowing, 150 kg of sinter was added. Blowing started at the position of the tuyere 20 of reduced calibers and after 30 s, tons. e. after ignition of the smelting, the tuyere lifts up to 33 calibrations (working position) and the consumption of oxygen in the amount of 40 cast iron with a 32% FeO content in the slag and the melt temperature, slag in the amount of 120 kg / t of steel was downloaded. With a basic slag of 2.8, the chemical composition of the melt was as follows,%: C 3.05; Mp 0.20; chromium 0.24; phosphorus 0.02 and sulfur 0.021.

In the second period, 400 lime was added, 100 kg of sinter and 20 kg of fluorspar were sown. Purging was carried out at an oxygen consumption of 40 m / min at a lance height of 15 calibers listed. At the end of the purge, we obtained,%: carbon 0., 14; chromium 0.16; phosphorus 0,008; sulfur 0.012, with a slag basicity of 4.6, a slag content of 17.8% FeO and a metal temperature of 1650 ° C. ,

Example 2. In a 10-ton converter piled 2.0 tons of scrap and poured 8.0 g of pig iron with the content,%: carbon 4.5; silicon 0.78; chromium 1,5; manganese 0.80. During the first 3 minutes of purging, 500 kg of lime, 25 kg of fluorspar and 250 kg of sinter were added to the converter. Purging was carried out at the working position of the tuyere 24 calibers, and the consumption of oxygen in the amount of 35 pig iron at a melt temperature of 1400 C and a content of 0.08% silicon, 0.38% chromium, 3.3% carbon, and slag in the amount of 90 kg / t steel. The basicity of the slag was 2.5, the content of FeO in the slag was 26.0%.

(about 15 0 5

about 0

five

In the BTopoh period, 400 kg of lime and fluorspar were added. At the end of the purge they obtained,%: carbon 0.18, chromium 0.24, phosphorus 0.008, sulfur 0.022, with a basicity of pshak 4.3, a content of 15.2% FeO in the donkey and TeMiieurture metal 1640 C.

Example 3. A 10-ton converter piled 2.0 tons of scrap and poured 8.0 tons of pig iron with the content,%: carbon 4.5, silicon 0.8, and chromium 1.45. Within 3 minutes of purging into the converter: 480 kg of lime, 30 kg of fluorspar and 200 kg of sinter were added. Purging was carried out at the position of 29 calibers, and when oxygen was consumed in the amount of 37.5 m- / t of pig iron at a melt temperature of 1420 C / t, its content was 3.2% carbon, 0.06% silicon, 0.29% chromium Oshak in the amount of 105 kg / t of steel. The slag contained 29.2% FeO with a basicity of 2.95.

In the second period, 400 kg of lime, 20 kg of fluorspar and 50 kg of sinter were added. At the end of the purge, 0.18% of carbon and 0.18% of chromium were obtained with 16.2% of FeO in the slag, its basicity was 4.8, and the temperature of the metal 1645 C.

Doduvka on these heats were not performed, which led to a decrease in the cycle of heats.

The technical advantages of the proposed method in comparison with the known ones consist in increasing the oxidation and basicity of the slag being charged, reducing the temperature of the first period, which allows for a more complete oxidation of chromium in the first period and ensuring a 100% yield of melts on the chromium content, eliminating significant metal and metal oxidation. blower on chrome.

Claims (1)

Invention Formula The method of steel production from chromium iron in the converter, including two periods of oxygen purging and intermediate slag loading, characterized in that, in order to increase the yield of heat of chromium and increase productivity, purge is carried out in the first period when the tuyere is above the melt level 25 -33 712570978 These calibers, and on the basis of 26-32% FeO and a temperature of 1800–1440 ° C oxygen in the amount of 1400–1440 ° C, 35–40 iron was downloaded, and the content in the slag was 90–120 kg / t of steel.