SU773079A1 - Method of cast iron refining in a ladle - Google Patents

Description

one

The invention relates to the production of ferrous metals and can be used in complex out-of-furnace processing of cast iron with stabilization, in it the temperature and content of 5 silicon and sulfur, 1 as well as for obtaining iron-carbon semi-products or steel in the buckets.

One of the main objectives of increasing the efficiency of steel production is to reduce the content of harmful impurities in the iron and to stabilize its chemical composition and temperature. The most successful t5 peujeHH can be these issues by the use of out-of-furnace iron treatment.

Methods for the secondary treatment of pig iron are known, in which a desulfurizer is introduced into the ladle and, mixing with 20 nIM cast iron, the reduction of sulfur content 1 is achieved.

The disadvantage of this process is that the temperature of the cast iron decreases and its stabilization by silicon content is not achieved.

There is a method of processing pig iron with mixing gas lift ,. including the rise of molten metal by transporting gas over a 30

on the gas lift side above the surface onto which the reagent was previously filled, and the subsequent discharge of metal from the column into the ladle through the layer of this reagent 2.

The disadvantage of this method when using oxygen-containing reagents is the relatively low intensity of the process, since pulling the reagent into the ladle leads to a sharp gas release from the metal and possible emissions of the metal from the ladle. In addition, during the process, as a rule, it is possible either to remove only sulfur or only silicon (their joint removal will not ensure the stability of the results), and the temperature of the iron during the processing process will noticeably decrease.

The purpose of the invention is to increase the stability of the chemical composition and temperature of the cast iron and to intensify the process.

The goal is achieved by the fact that a desulfurizer is introduced into the lower part of a gas-lift column immersed in cast iron, and oxygen-containing gas is introduced into the gas-metal flow coming out of the column with a counter-directed jet with a flow rate of 2.5 to 30.0 Nm. / s per 1 m 2-section of the column. Due to the independent, separate input of the desulphurizer and the oxidizing agent, both the desulfurization and the desiliconization are highly stable (or. It is known that, under conditions of high oxidizing potential of the medium, metal desulphurization is very difficult. desulfurization and the possibility of achieving stable results. Desulfurizer consumption is selected depending on its desulfurization ability and the desired degree of desulfur It is most convenient to enter it in powder form in a carrier gas stream. It can also be independently fed through a separate tuyere. The desulfurizer itself can also be an additional transporting body, for example magnesium or soda in superheated iron. The oxygen-containing gas is introduced from above through a tuyere mounted along the axis of the column and fitted at the exit with a Laval nozzle, which allows to obtain an outflow rate exceeding the speed of sound (500 m / s and more) and to ensure a significant penetration depth into outflow and sufficiently large surface contact of gas with metal. The conditions for the interaction of oxygen with iron impurities with the proposed method are much better than in the oxygen-converting process, since the metal comes to the reaction zone already in a state sprayed with a transporting gas and a desulphurizer. The consumption of oxygen-containing gas is limited by the size of the gas-lift and the necessary degree of removal of impurities. Under actual conditions of metallurgical plants, it should be kept within 2.5 - 30.0 Nm / s per 1 m of the column section. With an increase in the flow rate above 30.0 .k, it is possible to stop the column and stop lifting metal on it. When the flow rate drops below the lower great-grandfather, it is possible to seize the channel of the tuyere with metal and drastically reduce the processing efficiency. Oxygen can be introduced through the tuyere either in its pure form or in a mixture with nitrogen, argon or natural raqiOM. if in the process of refining it is necessary to reduce the content of ry in the guna and raise the temperature without significantly lowering the content of silicon in it. The flow rate of the carrier gas, as in the known method, is maintained at 0.2 - 0.7 per 1 m of the cross section of the column; air, nitrogen, and natural gas are used as transport gas. The depth of immersion of the gas lift column into cast iron is 0.8-2.5 m, the height of metal lifting above the surface in the ladle is 0.2–0.8 m. The drawing shows a diagram of the device that implements the proposed method. The device comprises a gas lift column 1 immersed in metal, a gas separation chamber 2, a lance 3 for introducing oxygen-containing gas, a pipeline 4 with a tuyere for introducing carrier gas and a desulfurizer, a gas lift outlet 5, a pipeline b for exhaust gas removal. The method is carried out as follows. Before immersion of the gas lift column into the cast iron, the supply of the transporting gas is carried out. And through the pipeline 4 and oxygen-containing gas., Gas through the tuyere 3. After that, the gas lift is immersed in the bucket with the cast iron. After complete immersion of the gas lift, the desulphurizer (in this case, t; also via pipeline 4) is turned on. Exhaust gases are discharged through pipeline b, connected through a movable joint to the gas cleaning pipeline. Example 1. Refining is subjected to cast iron, intended for pouring into the open-hearth furnace, of composition 4.1% С, 0.80% Si, 0.70% Mp., .0.040% S. The temperature of the iron before the treatment is 1340 ° C, the amount of iron in the ladle 85 tons. Treatment is carried out with a gas lift with a column cross section of 230 x 230 mm (area 0.053 m) with oxygen consumption through the upper lance 2500 Nm h (13.1 Nm / s per 1 m column cross section) and consumption of carrier gas "(nitrogen) 150 Nm h (0.78 ImVc per 1 m column cross section). A mixture of granulated magnesium and lime in the ratio of 1: 4 in the amount of 20 kg / min is blown in with the nitrogen as a desulfurizer. After 8 min of refining, a pig iron of composition 4.05% C, 0.45% Si, 0.40% Mn, 0.021% S, is obtained. The temperature of the iron after treatment. Thus, in a short treatment time (8 min), it is possible to achieve stabilization of the chemical composition of cast iron over both silicon and sulfur, and to raise the temperature of the cast iron to. Example 2 Under the conditions of an open-hearth shop, cast iron of the following composition is processed: 3.9% C,. 0.45% Si, 0, iB% Mn, 0.050% S. The temperature of the pig iron before the treatment is 1310 s, the mass of the iron in the BO BO t. During the treatment in, gas lift with the same solutions as in example 1, as transporting natural gas with a flow rate of 6 and e-feed with a flow rate of 85 kg / min.

Claims (2)

Claim 1. A method of refining cast iron in a ladle, including immersing a gas lift lifting column in a ladle, introducing reagents into the metal and mixing them with metal Order 7432/32 Circulation 608 'Subscription VNIIIPI State Committee of the USSR. for inventions and discoveries 4/5 gas elevator gas, 113035, Moscow, Zh-35, Raushskaya nab. an oxygen-containing gas is introduced into the stream leaving the column in a counter directional stream. 2. The method of pop. 2, with the exception that the oxygen-containing gas is introduced in an amount of 2.5 to 30.0 Nm ^ / s per 1 section of the column.