RU2285050C1 - Method and production line for steel-making process - Google Patents

Abstract

FIELD: metallurgy; making high-quality steels at treatment in steel complex treatment unit.

SUBSTANCE: proposed method includes melting liquid charge in steel-making unit, teeming it to "ladle-furnace" followed by treatment in steel complex treatment unit and teeming. After treatment in steel complex treatment unit, final treatment of steel is performed by pouring it from "ladle-furnace" into teeming ladle with covering slag formed in steel complex treatment unit. Proposed method is carried out in production line provided with off-furnace treatment unit including steel complex treatment unit, "ladles-furnaces", tapping ladles, teeming unit and final treatment unit located between steel complex treatment unit and teeming unit.

EFFECT: reduction of time required for treatment of steel in "ladle-furnace"; reduced number of "ladles-furnaces".

6 cl, 1 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy, more precisely, to the smelting of high-quality steels with processing at the integrated steel processing unit (AKOS).

A known method of producing steel by the so-called classical technology (see D.P. Povolotsky et al. Electrometallurgy of steel and ferroalloys. M: Metallurgy, 1995, p. 344), in which high-quality, including alloy steels are smelted in small and medium capacity electric arc furnaces.

The classical steelmaking technology has a number of options, but all of them include a time-consuming period of melting refinement (refining, deoxidation, alloying, heating to a given temperature), which takes up to 60% of the total melting time with significant losses of alloying elements (Cr, W, V, Nb, Si, Mn), have a high power consumption. In addition, classical technology requires performers to have extensive production experience and high professional training.

Currently, a widespread method for producing high-quality steels (see "Proceedings of the VI Congress of steelmakers", Cherepovets, 17-19.10.2000, Pat. RU No. 2233.339, IPC ⁷ C 21 C 5/52, publ. 2004 d), including the smelting of a liquid billet with a one-slag process in heavy-duty arc electric furnaces, the discharge of the billet into a “ladle furnace” (“kp”), lined with periclase-carbon materials, having devices for purging the liquid billet with inert gases. "Kp" with a liquid billet is transferred to AKOS. At AKOS, equipped with a special transformer, the liquid billet is heated by electric arcs, the necessary fluxing agents are introduced into the “kp” through the charging devices in order to form a coating refining slag, as well as deoxidizers, ferroalloys containing alloying elements and modifiers. The resulting intermediate is processed at AKOS and cast from "to-p".

Closest to the claimed and adopted as a prototype of the method is a method of steel production ("Proceedings of the VI Congress of steelmakers" Cherepovets, 17-19.10.2000 g), including the smelting of a liquid billet in a steelmaking unit, its release in "K-p", lined with refractory material with high chemical resistance to liquid slag and metal, its subsequent treatment at AKOS and casting from "to-p".

This method allows to obtain high-quality steel with high metallurgical parameters (uniformity in chemical composition, temperature, low concentrations of harmful impurities, gases, low pollution by non-metallic inclusions, good "spillability"), ensuring the production of high-quality metal products.

Closest to the claimed production line and adopted as a prototype is a steel production line (Pat. RU No. 21198 U1, IPC ⁷ C 21 C 5/28, publ. 2001), containing a steel-smelting unit interconnected by vehicles, device out-of-furnace metal processing, including AKOS, "ladle-kilns" lined with refractory material with high chemical resistance to liquid slag and metal, and a casting device.

However, the specified method of smelting and the production line have a number of disadvantages, which are especially manifested in the smelting of high-quality steel of a wide range of grades, including alloyed and highly alloyed, on the technological line: arc steel-smelting furnace (DSP) - AKOS - casting device (continuous casting machine (CCM), siphon casting, top casting in forging ingots of various weights). Such disadvantages include:

- the difficulty of synchronizing the operation of chipboard and AKOS, for example, the total duration of melting in a chipboard with a capacity of 60 tons takes 40-50 minutes for almost any grade of steel, except for the smelting of low-carbon (C≤0.05%), medium alloy steels, during which the melting time increases up to 60 minutes, and the processing time of steel at AKOS in the first case is from 50 to 60 minutes, in the second case, the processing time is up to 70 minutes or more. This leads to downtime of the particleboard and, in turn, to an increase in the specific consumption of electricity, refractories;

V, Nb, Mn, Si и др. от 15% и выше (Cr - до 20%) стали, что в свою очередь требует применения низкоуглеродистых или безуглеродистых дорогих ферросплавов, а также высокого обезуглероживания (С≤0,03%), перегрева, переокисления жидкой заготовки в ДСП, приводящего к повышенному расходу электроэнергии, огнеупоров, увеличению продолжительности плавки;- the increase in the duration of treatment at AKOS in "KP", lined with periclase-carbon refractory, leads to an undesirable increase in the carbon content in the metal. This is especially true for the smelting of low-carbon (С≤0.10%), highly alloyed - ΣCr, Ni, Mo,

V, Nb, Mn, Si, etc. from 15% and above (Cr - up to 20%) steel, which in turn requires the use of low-carbon or carbon-free expensive ferroalloys, as well as high decarburization (C≤0.03%), overheating , reoxidation of the liquid billet in the particleboard, leading to increased consumption of electricity, refractories, increase the duration of the melting;

- the production of ingots with various casting methods (continuous casting machine, siphon, horse) requires different durations of indebtedness, for example, when casting metal on continuous casting machines, the indebtedness of the indemnity from chipboard to the readiness for the next melting is more than 3 hours, while the stay of the liquid workpiece in the "K-p" is 135 minutes; when casting in blacksmith ingots weighing 2 ... 4 tons - 120 minutes. This leads to the involvement in the operation of the production line with one chipboard and one AKOS, at least four "KP". The presence of "empty" "kp", i.e. free from liquid billets, preparation of “KP” for receiving the next heat - slag draining, casting, etc. leads to a significant cooling of KP refractories due to the high thermal conductivity of the periclase-carbon lining and the need for further heating by a gas-oxygen mixture, leading to thermal destruction of the working (hot) layer of the lining and its depletion of carbon, which reduces chemical resistance to slag and metal.

These shortcomings increase the specific consumption of natural gas and compressed air for heating “kp”, expensive refractories, which requires additional overheating of the liquid billet in the electric furnace to compensate for the loss of temperature of the “empty” kp, which in turn leads to increased consumption electricity.

The objective of the invention is to reduce the cost of obtaining complex, high-quality steels.

The only technical result achieved by using the proposed method and device is the synchronization of chipboard and AKOS operation, reduction of processing time at AKOS in “kp”, reduction in the number of “kp” required to operate a production line with one chipboard and one AKOS .

The problem is solved by improving the method of producing steel, including the smelting of a liquid billet in a steel-smelting unit, its production in “kp”, lined with refractory material with high chemical resistance to liquid slag and metal, its subsequent processing on AKOS and casting.

This improvement consists in the fact that after processing at AKOS, the final refinement of steel is additionally carried out by overflow from Kp to a casting ladle with a cover slag formed on AKOS.

The final refinement after processing at AKOS has become an overflow from “kp” to a casting ladle with a cover slag formed at AKOS, which allows to release the “kp” and thus reduce the residence time and processing of the liquid workpiece in the “kp” and reduce the number of "kp" necessary for the operation of one chipboard and one AKOS. At the same time, during the overflow process, the metal is mixed with the coating slag, which results in the process of emulsification of the metal with slag, and as a result, refining from sulfur and non-metallic inclusions, which reduces the processing time of the liquid billet at AKOS.

The task is also solved by improving the technological line for the production of steel, which contains a steel-smelting unit interconnected by vehicles, an out-of-furnace metal processing device, including AKOS, "kp" lined with refractory material with high chemical resistance to liquid slag and metal, and a device casting.

This improvement lies in the fact that the production line is equipped with casting ladles, and the device for secondary metal processing is additionally equipped with a final steel finishing unit, made in the form of a steel overflow device from “to-p” to the casting ladle located between AKOS and the casting device.

In addition, the casting ladle can be lined with semi-acidic material, such as chamotte.

In addition, "kp" may have one or more nodes for purging the liquid preform.

In addition, the casting bucket may have one or more nodes for purging steel.

In addition, the device for overflowing steel from “KP” to the casting ladle can be equipped with units for supplying inert gas, introducing modifying and microalloying additives, and determining the mass of overflowed steel.

The supply of the production line with casting ladles, and the device for secondary metal processing with a final steel finishing unit made in the form of a device for overflowing steel from the “to-p” to the casting ladle located between AKOS and the casting device, allows to release the “to-p” and such way to reduce the residence time and processing of the liquid billet in "KP", to reduce the number of "KP" necessary for the operation of the production line with one chipboard and one AKOS.

Moreover, in the process of overflow, the metal is mixed with the coating slag, as a result of which the process of emulsification of the metal with slag and, as a result, refining from sulfur and non-metallic inclusions takes place.

The lining of the casting ladle with semi-acidic material, such as chamotte, makes it possible to use a ladle lined with cheaper material for casting, while ensuring sufficient durability of the lining.

The supply of “kp” with one or more nodes for purging a liquid preform allows, when processing at AKOS, to purge the liquid preform with an inert gas to intensify the processing process. At the same time, the nodes for purging the liquid billet are located rationally in the bottom of the bucket, since there is no need for an arrangement in the bottom of the casting unit.

Providing the casting ladle with one or more nodes for purging the steel allows purging the liquid billet with inert gas to intensify the process during overflow.

The supply of steel overflow device to the pouring ladle with inert gas supply units, introduction of modifying and microalloying additives and determining the mass of the transfused liquid preform allows the inert gas to be purged of the liquid preform during the overflow, introducing modifying and microalloying additives and determining the mass of the transfused liquid blanks for process control.

The proposed group of inventions is illustrated in the drawing, which shows a technological line for the production of steel.

The production line contains steel-smelting interconnected vehicles (not shown), a chipboard unit 1, an out-of-furnace metal processing device, including AKOS 2, “kp” 3, lined with refractory material with high chemical resistance to liquid slag and metal, and casting device 4. The production line is equipped with casting ladles 5 lined with semi-acid material, for example chamotte. The out-of-furnace metal processing device is additionally equipped with a final steel finishing unit, made in the form of a device 6 for overflowing steel from “to-p” 3 into a casting ladle 5 located between AKOS 2 and the casting section 4.

In the above embodiment, “kp” 3 has one unit 7 for purging a liquid billet located in the bottom, and the casting bucket 5 has one unit 8 for purging steel. The device 6 overflow of steel from "KP" 3 into the casting ladle 5 is equipped with a node 9 for supplying an inert gas, a node for introducing modifying and microalloying additives (not shown) and a node 10 for determining the mass of the overflow steel.

The proposed method is carried out on the proposed production line as follows.

In chipboard 1, which has a gas-oxygen burner, a device for foaming slag with carbon-containing materials, a water-cooled arch with holes for feeding slag-forming materials into the working space, a liquid billet is melted for subsequent refinement to the parameters of a certain steel grade.

Then the liquid billet is produced in “KP” 3, lined with periclase-carbon brick and having nodes 7 in the center of the bottom for purging the liquid billet with inert gas (argon), and transferred to AKOS 2.

At AKOS 2, processing is carried out, including guidance of the coating refining slag, deoxidation, alloying to the required grade composition and temperature, modification, after which, on the device 6, steel is poured from “KP” 3 together with the coating slag into the casting ladle 5. In the process overflow metal is mixed with a coating slag, as a result of which there is a process of emulsification of metal with slag and as a result - the final refinement of steel - refining from sulfur and non-metallic inclusions. After that, the casting ladle 5 is transferred to the casting device 4, where steel is cast from the casting ladle. Released after overflow, not cooled "K-p" 3 is heated, if necessary, to the desired temperature, is fed to the exhaust unit of chipboard 1 and is filled with a liquid billet of the next heat.

An example of smelting stainless steel 15GS according to GOST 4543-71 of the proposed method.

The liquid billet was smelted in a DSP-60 arc furnace equipped with a furnace transformer with a capacity of 40 MVA (0.67 MVA / t). As the charge used scrap of carbon steel grades and coke, the weight of the metal filling was 64 tons.

The chemical composition of the liquid billet before the release of melting from particleboard,%:

C — 0.08, Mn — 0.10, Si — 0.01, P — 0.008, S — 0.038, Cr — 0.12, Ni — 0.25, Cu — 0.17; Fe is the rest; workpiece temperature 1620 ° C.

In the process of releasing a liquid preform from DSP-60, silicomanganese (Mn - 66%, Si - 18%, C - 1.5%), ferrosilicon (Si -46%), and aluminum in pigs 550, 400 were introduced into "to-p" and 32 kg, respectively, and freshly burnt lime 400 kg. When releasing the billet from DSP-60, measures were envisaged to ensure the minimum penetration of furnace oxidizing slag into the “kp”. Then the “kp” was transferred to AKOS.

The chemical composition of the workpiece in the initial processing period at AKOS,%:

C — 0.10, Mn — 0.70, Si — 0.20, P — 0.012, S — 0.036, Cr — 0.12, Ni — 0.24, Cu — 0.18, Fe — the rest; workpiece temperature - 1590 ° C.

In the course of processing, coating slag was induced by feeding lime to slag, slag from the production of secondary aluminum, alloyed with carbon ferromanganese, and ferrosilicon. During the entire processing of the workpiece at AKOS, it was purged with argon.

Upon receipt of the given chemical composition, temperature of the billet and slag, which has a white-gray color, which indicates the content of FeO <1.5-2.0% in it, microalloying was carried out using silicoway wire, after which the “k-p” was transferred for metal overflow into the casting bucket.

The chemical composition of the workpiece before feeding "KP" with AKOS for overflow,%: C - 0.16, Mn - 0.95, Si - 0.78, P - 0.016, S - 0.026, Ni - 0.25, Cu - 0.18, Ca - 0.002, Fe - the rest; coating slag (main elements): CaO - 52%, SiO ₂ - 20%, Al ₂ O ₃ - 20%, MgO - 6%; workpiece temperature - 1580 ° C. Then produced overflow from "KP" to the casting ladle, which was transferred to the casting device in the forging ingots. The temperature of the metal in the casting ladle is 1560 ° C. The chemical composition of the finished steel,%: C - 0.16, Mn - 0.96, Si - 0.77, P - 0.016, S - 0.012, Ni - 0.25, Cu - 0.18, Al - 0.015, Ca - 0.001.

Comparative main technical parameters of smelting stainless steel according to the prototype method and the claimed are given in the table.

No. p / p Parameter Units Prototype (averaged) The claimed Difference
(-) savings (+) losses one 2 3 four 5 6 Electric arc furnace ДСП-60 one Smelting Duration min 45 42 -3 2 Power consumption kWh / t 480 455 -25 3 Metal temperature at the outlet ° C 1640 1620 -twenty four Periclase-carbon refractory consumption kg / t 1.14 1.09 -0.05 AKOS 5 Metal temperature at the beginning of processing ° C 1570 1580 6 Duration of processing at AKOS min 55 40 7 Metal temperature at the end of processing at AKOS ° C 1580 1580 8 Power consumption during processing at AKOS kWh / t 60 54 -6 9 Argon consumption Kg / t 1.66 1,50 -0.16 10 The need for "KP" PC. four 2 -2 eleven ^* Consumption of casting ladles PC. - 3 +3 12 Periclase-carbon refractory consumption Kg / t 3.94 2.76 -1.18 13 The consumption of semi-acid (chamotte) refractories Kg / t - 8.5 +8.5 fourteen The consumption of natural gas for heating-heating "KP", pouring ladles m ³ / t 17.33 3.15 -14.18 2.66 + 2.66 fifteen Sulfur content - on the release of melting from particleboard 0,038 0,038 - at the end of processing at AKOS 0.014 0,028 - in finished steel 0.014 0.013 16 Contamination of metal by non-metallic inclusions The average score for all inclusions 1,2 1,2 17 Nitrogen content - end of processing at AKOS % 0.010 0.007 - 0.003 - start of casting 0.010 0.008 - 0.002 ^* When operating DSP-60 with a capacity of 900 tons (16 heats per day)

The table shows: the duration of the smelting on DSP-60 when using the proposed method and technological line decreased by 3 minutes with a decrease in the temperature of the metal by 20 ° C, which is explained by the higher temperature supplied to the smelting "K-p" with minimal heating, as time the turnover of "KP" from smelting to smelting decreased by 2-2.5 times and "KP" did not have time to cool.

The consumption of refractories in the DSP-60 furnace decreased by 0.05 kg / t (more than 4%), which is associated with a lower metal temperature in the furnace and a decrease in the melting time by 3 minutes.

The processing time at AKOS decreased by 15 minutes, because there is no need for high metal desulfurization (only from 0.036 to 0.026%), and final refinement - deeper desulfurization (up to 0.012%) and metal refining from nonmetallic inclusions was carried out when the metal was poured from “kp” together with coating refining slag, formed on AKOS into a casting ladle. The consumption of expensive refractories for "K-P" is reduced by ~ 30%, which is explained by an increase in the durability of the working lining due to:

- reducing the duration of processing liquid billets at AKOS, eliminating the debt "to-p" for metal casting;

- reducing the duration of turnover "K-P" in 3 ... 4 times (from 4 ... 5 hours to 1 ... 1,5 hours), which in turn reduced the temperature loss of the working "hot" layer of the lining and thermal destruction, and a decrease in the duration of the heating and heating of the bucket with a gas-air mixture made it possible to reduce its carbon depletion and had a positive effect on chemical stability upon contact with a liquid billet and slag.

Thus, the use of the proposed group of inventions allows to reduce the cost of obtaining complex, high-quality steels by synchronizing the work of chipboard and AKOS, reducing the processing time at AKOS in "kp", reducing the number of "kp" required to operate the production line with one chipboard and one AKOS.

Claims (6)

1. Method for the production of steel, including the smelting of a liquid billet in an electric arc furnace, its release into a “ladle furnace” lined with refractory material with high chemical resistance to liquid slag and metal, its subsequent processing at the integrated steel processing unit (AKOS) and casting, characterized in that after processing at AKOS, additional final finishing of the steel is carried out by overflow from the “ladle-furnace” to the casting ladle with a cover slag formed on AKOS. 2. A steel production line containing an interconnected electric steel furnace, an out-of-furnace metal processing device including AKOS, a ladle furnace lined with refractory material with high chemical resistance to liquid slag and metal, and a casting device, characterized in that it is equipped with a casting ladle, and the device for secondary metal processing is additionally equipped with a final finishing unit for steel, made in the form of a device reliva steel of "ladle-furnace" in the ladle, disposed between the casting device and ICCO. 3. The production line according to claim 2, characterized in that the casting ladle is lined with semi-acidic material, such as chamotte. 4. The production line according to claim 2, characterized in that the "ladle-furnace" has one or more nodes for purging the liquid billet. 5. The production line according to claim 2, characterized in that the casting ladle has one or more nodes for purging steel. 6. The production line according to claim 2, characterized in that the device for overflowing steel from the “ladle-furnace” into the casting ladle is equipped with inert gas supply units, introducing modifying and microalloying additives and determining the mass of the overflowed steel.