RU2833062C9 - Method of producing wire rod from copper raw material - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: invention relates to a method of producing wire rod from copper raw material. Charge is loaded into refining reflecting furnace and initial melt for wire rod is formed from copper raw material. After melting of copper raw material content of oxygen in melt from 2,000 to 2,500 ppm is obtained. One-stage refining is performed using boric acid flux. Said melt is mixed, slag is removed and oxygen content is reduced to 150-250 ppm. After reduction, melt temperature is reduced to 1,100-1,120°C by introducing a melt for wire rod from copper raw material with content of weight fractions of elements equal to that of the initial melt. Casting of melt for wire rod and rolling to produce wire rod is performed. When casting melt for wire rod into refining reflecting furnace, additional loading of melt from copper raw material is performed with maintenance of melt temperature in casting bath in range from 1,105 to 1,115°C.

EFFECT: as a result, the coefficient of use of the refining reflecting furnace for production of wire rod from copper raw material is increased.

8 cl, 1 ex

Description

The invention relates to methods of casting and rolling copper rod with simultaneous additional loading of the charge into a refining reverberatory furnace [C22B 15/00, B21B 1/46].

The prior art discloses a METHOD FOR PRODUCING OXYGEN-FREE COPPER ROD [CN 105821219 A, published 03.08.2016] using a line for producing oxygen-free copper rod, comprising the following steps: removing regenerated copper and placing it in a drying furnace for heat treatment; placing the regenerated copper in a smelting furnace for smelting; refining and removing metallic impurities; reducing treatment; adding a rare earth element and a composite oxidizer to copper in a copper furnace; continuous casting and rolling; using a cleaning pool for cleaning.

The closest in technical essence is the METHOD OF PRODUCING OXYGEN-FREE COPPER ROD BY REFINING CONTAMINATED COPPER AND CONTINUOUS CASTING AND ROLLING [CN 101914688 A, published 15.12.2010] including the following stages: copper is sorted and packed; placed in a furnace and heated to 1300 °C; maintained at a temperature of 1100 to 1150 °C and melted, coke is added for primary oxidative refining, at a temperature of 1200-1250 °C, slag is removed; quartz is added for secondary oxidative refining, at a temperature of 1200-1250 °C, slag is removed; lime is added for triple oxidative refining at a temperature of 1200-1250°C, slag is removed; pure copper oxide is reduced; rare earth elements are added at a temperature of 1150-1170°C; then continuous casting and rolling are carried out.

The main technical problem of the analogue and prototype is that the above solutions use raw materials for the melt containing a large number of various impurities, due to which, when implementing the methods of the analogue and prototype, a large amount of time and resources are spent on refining the raw materials and preparing them for casting. This problem is especially acute when using reverberatory furnaces for casting. When using them, a long and complex refining process (due to the fact that the raw materials have a large number of impurities) leads to downtime in the furnace and, as a result, to a decrease in its utilization rate.

The objective of the invention is to eliminate the shortcomings of the prototype.

The technical result is an increase in the utilization factor of the refining reverberatory furnace for producing wire rod from copper raw materials.

The stated technical result is achieved due to the fact that the method for producing wire rod from copper raw materials is characterized in that the charge is initially loaded into the refining reverberatory furnace and the initial melt for wire rod from copper raw materials is formed with the following content of mass fractions of elements:

iron - no more than 30 ppm,

nickel - no more than 100 ppm,

tin - no more than 100 ppm,

lead - no more than 450 ppm,

antimony - no more than 45 ppm,

sulfur - no more than 30 ppm,

tellurium - no more than 20 ppm,

zinc - no more than 50 ppm,

bismuth - no more than 20 ppm,

copper and silver content - 99.91%-99.95%,

oxygen content from 150 ppm to 250 ppm,

the total content of iron, nickel, tin, lead, antimony, sulfur, tellurium, zinc and bismuth does not exceed 0.065%,

after melting the copper raw material, an oxygen content of 2000 to 2500 ppm is obtained in the melt, then a single-stage refining is carried out using a boric acid flux, then the said melt is mixed, slag is removed and the oxygen content is subsequently restored to values of 150-250 ppm, after the end of the restoration, the temperature of the melt is reduced to 1100-1120 °C by introducing a melt for wire rod from copper raw materials with a content of mass fractions of elements the same as the original melt, then the melt is cast for wire rod and rolled to obtain wire rod, wherein during casting the melt for wire rod into the refining reverberatory furnace, additional loading of the melt from copper raw materials is periodically carried out with maintaining the temperature of the melt in the casting bath in the range of 1105 to 1115 °C.

In particular, the initial melt for wire rod is prepared from a charge consisting of copper cathodes with a copper content of at least 99.93%.

In particular, the initial melt for wire rod is prepared from a charge consisting of copper strands of mechanically separated cable with a copper content of at least 99.91%.

In particular, the initial melt for wire rod is prepared from a charge consisting of copper ingots with a copper content of at least 99.5%.

In particular, the additionally loaded melt for copper raw material wire rod is prepared from a charge consisting of copper cathodes with a copper content of at least 99.93%.

In particular, the reloaded melt for copper raw material wire rod is prepared from a charge consisting of mechanically separated copper cable with a copper content of at least 99.91%.

In particular, additional loading of melt for wire rod is carried out in portions from 500 kg to 2500 kg at intervals of 8-15 minutes.

In particular, after the end of the reduction, the temperature of the melt is reduced to 1100-1120°C by introducing a melt for wire rod from copper raw materials with a content of mass fractions of elements the same as the initial melt with impurities of no more than 0.3%.

The claimed method can be implemented on equipment from the Italian company Continuus-Peoperzi S.p.A., which includes a reverberatory rocking refining furnace with a maximum volume of 81.5 tons and a continuous casting and rolling line.

The claimed method is implemented in several main stages.

The first stage of loading and melting the charge in the refining reverberatory furnace is characterized by the fact that the melt for the wire rod is prepared from a homogeneous charge in the form of copper cathodes of various qualities with a copper content of at least 99.93%, electrical copper scrap in the form of a copper core of a mechanically separated cable - with a copper content of at least 99.91% and copper ingots with a copper content of at least 99.5%.

In this way, a melt for wire rod is formed that satisfies the following requirements for the content of mass fractions of elements:

Fe (not more than, ppm) - 30;

Ni (not more than, ppm) - 100;

Sn (not more than, ppm) - 100;

Pb (not more than, ppm) - 450;

Sb (not more than, ppm) - 45;

S (not more than, ppm) - 30;

Te (not more than, ppm) - 20;

Zn (not more than, ppm) - 50;

Bi (not more than, ppm) - 20;

The sum of elements Fe, Ni, Sn, Pb, Sb, S, Te, Zn, Bi (not more than %) 0.065%;

Oxygen content (%): 0.015-0.025;

Cu + Ag content (not less than%) 99.91-99.95.

It follows from this that, by combining the loading of different types of charge and analyzing the chemical composition of the furnace melt, the process of preparing the melt for rolling is carried out within the framework of the above-mentioned chemical composition (which satisfies the requirements of the chemical composition of the KMor copper grade). It follows from this that after loading and melting, the chemical composition of the furnace melt corresponds to the above-mentioned in terms of impurity content.

The process of loading copper raw materials for obtaining the primary copper melt is carried out through the loading window in several portions with a time interval held for the complete melting of each portion using a burner installed in one of the furnace walls. After the final loading of the raw materials into the furnace, a time holding is also carried out, which is necessary for the complete melting of the copper raw materials in order to proceed to the next technological stage - refining. In this case, after loading and melting, the oxygen content in the melt is from 2000 to 2500 ppm. The duration of the loading and melting stage is 6.5 hours.

The second stage is the stage of refining and reduction. The refining process for the claimed method is characterized by the fact that it is reduced in time. The time of the refining stage is reduced by carrying out single-stage fire refining, since only a homogeneous charge of the above-mentioned chemical composition is used in the process of melt preparation. Single-stage fire refining is carried out in order to remove part of the impurities that have, in comparison with copper, an increased affinity for oxygen, as well as to remove surface contaminants, such as surface oxides, dust that are formed during preparation, storage and transportation on cathodes, ingots and copper core, traces of drawing emulsion and plasticizer on the surface of the mechanically cut copper core. Refining also achieves equalization of the chemical composition of the melt in the furnace. Within the framework of the claimed method, refining is carried out only by fire, without the use of refining fluxes. Slag removal is carried out using a boric acid flux, which liquefies the slag. At the stage of fire refining and reduction, the melt is also stirred with tuyeres, slag is removed and the oxygen content is then restored to the values of 150-250 ppm required for casting. The duration of the refining and reduction stages is 2.5 hours. Upon completion of the reduction stage, the melt temperature in the furnace reaches 1180-1200°C. To conduct the casting and rolling process, it is reduced to 1100-1120°C, which is achieved by introducing a portion of the charge with a copper and silver content of at least 99.91% (with the content of mass fractions of elements the same as the above-mentioned melt for wire rod). Cooling of the melt can only be performed with a homogeneous charge with an impurity and oxygen content not exceeding the values specified for the wire rod melt and a clogging of no more than 0.3%, so as not to spoil the melt in chemical composition and not to obtain a surface slag layer.

The third stage is the casting and rolling stage . This stage lasts on average 16.5 hours. During this time, the furnace is additionally loaded (additional loading during casting and rolling). The process is designed in such a way that batch portions are loaded at certain intervals (in the embodiment, copper cathodes alternate with copper wire in the additionally loaded portions, as well as with recycled waste from our own production, while the chemical composition of the additionally loaded batch must also meet the requirements for impurity and oxygen content not exceeding the values specified for the wire rod melt; in particular, the melt is additionally loaded from copper raw materials consisting of copper cathodes with a copper content of at least 99.93% and from copper raw materials consisting of mechanically separated copper cable with a copper content of at least 99.91%). During the implementation of the entire casting and rolling stage, the chemical composition of the melt in the furnace and wire rod coils is monitored, and the temperature of the melt is monitored. To avoid problems during rolling, the chemical composition in the furnace must be stable and meet the requirements for impurity and oxygen content not exceeding the values specified for the rod melt. At the same time, the melt temperature must be within 1100-1120 ° C. Thus, due to the additional loading of batch portions, the speed of metal flow from the furnace and the speed of feeding and melting of the metal fed into the furnace are synchronized, forming a continuous process for obtaining copper rod.

In the embodiment, additional loading can be carried out in portions from 500 to 2500 kg, after a time interval of 8-15 minutes, depending on the temperature of the melt and its amount in the furnace. The smaller the melt residue in the furnace and the lower the temperature, the smaller the portion size. The main task in this case is to ensure a melt temperature range of 1100-1120 °C. At a high melt temperature, the probability of obtaining a cast billet with a crystalline structure different from the optimal one increases, which will not ensure the best quality of copper rod. At a low melt temperature, the risk of copper crystallization in the furnace taphole and stopping casting increases.

Justification of the boundaries used in the implementation of the claimed method, ranges of physical quantities.

The requirements for the content of mass fractions of elements for the wire rod melt (which is used at all stages of the implementation of the claimed method) were determined experimentally (iron - no more than 30 ppm, nickel - no more than 100 ppm, tin - no more than 100 ppm, lead - no more than 450 ppm, antimony - no more than 45 ppm, sulfur - no more than 30 ppm, tellurium - no more than 20 ppm, zinc - no more than 50 ppm, bismuth - no more than 20 ppm; the sum of the elements Fe, Ni, Sn, Pb, Sb, S, Te, Zn, Bi no more than 0.065%; oxygen content: 0.015-0.025%; Cu + Ag content from 99.91% to 99.95%). Going beyond the specified ranges will make it impossible to implement the claimed method, since in this case the wire rod melt will contain an unacceptable amount of impurities, which will require additional technological procedures for their removal (which will require significant adjustments at the refining and recovery stages, as well as at the casting and rolling stages). Similar arguments are appropriate regarding the initial raw materials, namely

copper core of mechanically separated cable - with copper content of at least 99.91% and copper cathodes with copper content of at least 99.93%, copper ingots with copper content of at least 99.5%, no more than 10% per melt. Use of raw materials with lower copper content will make it impossible to implement the claimed method, since in such case the molten rod will contain an unacceptable amount of impurities. Similar conclusions are appropriate for the chemical composition of the melt of the additionally loaded raw materials, namely: additional loading of the melt is carried out from copper raw materials consisting of copper cathodes with copper content of at least 99.93% and from copper raw materials consisting of mechanically separated copper cable with copper content of at least 99.91%. Use of raw materials with lower copper content will make it impossible to implement the claimed method, since in such case the molten rod will contain an unacceptable amount of impurities. It was experimentally established that additional loading is carried out from copper raw materials of higher quality than the initial melt for the wire rod, and therefore ingots are not used for additional loading into the furnace.

Thus, it was experimentally established that the specified boundaries of the used ranges of physical quantities make it possible to meet the requirements of GOST R 53803-2010 for the electrical conductivity and surface quality of copper rod KMor when implementing the declared method.

After the melting of the charge in the fire refining furnace, the oxygen content in the melt should be in the range of 2000-2500 ppm. This is the optimal range, at which, on the one hand, the necessary oxidation of harmful impurities in the melt occurs, the so-called fire refining, and on the other hand, the time of the recovery stage will not be increased when the oxygen content decreases to the value of 150-250 ppm required for the production of wire rod.

During single-stage fire refining, only oxidized impurities are removed. The oxygen content in the melt and, accordingly, in the rod, according to the process instructions, should be 150-250 ppm. The oxygen content in the melt is reduced to 150-250 ppm at the reduction stage. Only this range of oxygen values allows us to meet the requirements of GOST R 53803-2010 for electrical conductivity and surface quality of copper rod KMor.

Before the casting process, the temperature of the melt in the furnace is lowered to 1100-1120°C by introducing a portion of the charge. This temperature range is due to the need to maintain the temperature of the melt in the casting bath in the range of 1105-1115°C. And this range, in turn, is necessary to obtain a cast billet with the required crystalline structure, which determines the quality of the copper rod. Thus, at a high melt temperature, the probability of obtaining a cast billet with a crystalline structure different from the optimal one increases, which will not ensure the best quality of the copper rod. At a low melt temperature, the risk of copper crystallization in the taphole of the furnace and stopping the casting increases.

The use of additional loading from 500 to 2500 kg at intervals of 8-15 minutes is justified by experiments confirmed in practice, during which it was found that the use of additional loading outside the specified range of mass and time complicates the process of controlling the temperature of the furnace melt within the required limits.

The declared technical result: an increase in the utilization factor of the refining reverberatory furnace for producing copper wire rod, is achieved due to the fact that at all stages of the implementation of the declared method, namely at the stage of loading raw materials into the furnace, cooling (after the reduction stage) and additional loading (at the stage of casting and rolling), a melt is used for copper wire rod obtained from a homogeneous charge with an impurity content of no more than 0.065% (with an iron content of no more than 30 ppm; nickel - no more than 100 ppm; tin - no more than 100 ppm; lead - no more than 450 ppm; antimony - no more than 45 ppm; sulfur - no more than 30 ppm; tellurium - no more than 20 ppm; zinc - no more than 50 ppm; bismuth - no more than 20 ppm), with an oxygen content from 150 ppm to 250 ppm and a Cu + Ag content (not less than%) 99.91%-99.95%. Due to this, significantly less slag is formed during melting of the charge and at the stages of refining and reduction there is no need to use additional refining (in addition to single-stage fire refining with boric acid). Also, during casting and rolling, constant cooling of the melt is realized (without reducing the burner power) due to periodic additional loading of the melt from a homogeneous charge, due to which a continuous technological process of casting and rolling of copper rod is formed, which in turn allows to significantly increase the utilization rate of the refining reverberatory furnace.

An example of achieving a technical result

To confirm the stated technical result, a series of experiments was conducted for several possible methods of producing copper wire rod using a refining reverberatory furnace.

The first method is based on the technology of the Spanish company La Farga Lacambra, on equipment from the Italian company Continuus-Peoperzi S.p.A., including a reverberatory rocking refining furnace with a maximum capacity of 81.5 tons and a continuous casting and rolling line.

The second method according to the declared technology, on the equipment of the Italian company Continuus-Peoperzi S.p.A., includes a reverberatory rocking refining furnace with a maximum volume of 81.5 tons and a continuous casting and rolling line.

During the experiment it was found that the following are significant disadvantages of the La Farga Lacambra technology of melting in reverberatory furnaces with subsequent rolling:

- only 1/3 of the working time is effectively used for feeding liquid copper into the casting machine and rolling mill for the production of wire rod, which is due to the cyclic operation of the furnace: 8 hours - loading and melting; 8 hours - oxidation, refining, reduction; 8 hours - pouring liquid copper;

- the production cycle incorporated into the La Farga Lacambra technology strictly limits the volume of wire rod output per year, which is determined by the product of the volume of melt in the furnace and the number of melts;

- high gas consumption per 1 ton of wire rod; in addition, it is necessary to constantly maintain a certain temperature regime of the liquid copper melt in the furnace even in the absence of wire rod production, since starting and stopping reverberatory furnaces is much more difficult due to their design features;

- the presence of significant costs for the creation of a system of fireproof chimneys and cleaning of exhaust gases, since a large amount of exhaust gases with a temperature of 700 to 1100°C comes out of the furnace;

- the presence of significant costs for refining fluxes;

- accelerated wear of the lining.

One of the important factors due to which the above-mentioned shortcomings were identified is that scrap is used as the initial raw material for melting within the framework of the La Farga technology, which is a non-homogeneous product, since it includes various grades of copper (M00K, M0K, M06, M0, M1, M1r, M2, M2r, M3, M3r), copper microalloys (KMor, MS0.03, MS0.1, BrKd1, BrMg0.3). The presence of copper alloys alloyed with aluminum, silicon, iron is also possible (GOST 54564-2022, table 20). All the above-mentioned grades of copper and alloys are electrical grades and are used in devices transmitting electric current (wires, cables, including special-purpose ones using copper-nickel thermoelectrode alloy or resistance alloy cores; busbars; various parts of mechanisms, including motors, rheostats, etc.). Processing copper scrap with oxides and scale in the load leads to the emergence of several factors that do not allow for a stable standardized smelting process:

- unstable chemical composition in the melt, which will require multi-stage fire refining using fluxes;

- increased slag formation as a result of the reaction of oxygen from the melt with active elements of various grades of copper during melting;

- a sharp uncontrolled increase in the oxygen content in the melt over 250 ppm, which must be reduced to the required values of 150-250 ppm;

- release of free oxygen from oxides and scale, which enters into oxidation reactions first with active elements, and then with copper itself.

When implementing the claimed method, the above-mentioned problems were eliminated, which made it possible to organize a technological process for the production of copper wire rod with periodic additional loading of melt from a homogeneous charge without reducing the quality of the wire rod obtained after rolling.

The additionally loaded volume of copper during casting and rolling is 120 tons. Thus, during one smelting, a total of 200 tons of homogeneous charge were loaded and smelted into the fire refining furnace with a capacity of 80 tons. The preparation of production between smeltings was 0.5 hours. The total smelting time was on average 26 hours. The efficiency of using working time increased to 63%, and the productivity increased more than twofold from 3 tons/hour to 7 tons/hour, the consumption of natural gas was reduced by 10% for the production of 1 ton of copper rod, and the utilization rate of the refining reverberatory furnace for obtaining copper rod was increased by approximately 2.2 times, which confirms the declared technical result.

An assessment was also made of the average amount of copper rod produced per month and year of production (on similar equipment):

The first method, using the technology of the Spanish company La Farga Lacambra, produced an average amount of copper rod per month/year of 2650 tons/25800 tons.

The declared method - the average amount of copper rod produced per month/year was 4815 tons/55375 tons.

Claims (21)

1. A method for producing wire rod from copper raw materials, characterized in that the charge is initially loaded into a refining reverberatory furnace and an initial melt is formed for wire rod from copper raw materials with the following content of mass fractions of elements: iron - no more than 30 ppm, nickel - no more than 100 ppm, tin - no more than 100 ppm, lead - no more than 450 ppm, antimony - no more than 45 ppm, sulfur - no more than 30 ppm, tellurium - no more than 20 ppm, zinc - no more than 50 ppm, bismuth - no more than 20 ppm, copper and silver content - 99.91-99.95%, oxygen content - from 150 to 250 ppm, the total content of iron, nickel, tin, lead, antimony, sulfur, tellurium, zinc and bismuth does not exceed 0.065%, after melting the copper raw material, an oxygen content of 2000 to 2500 ppm is obtained in the melt, then a single-stage refining is carried out using a boric acid flux, then the said melt is mixed, slag is removed and the oxygen content is subsequently restored to values of 150-250 ppm, after the end of the restoration, the temperature of the melt is reduced to 1100-1120 °C by introducing a melt for wire rod from copper raw materials with a content of mass fractions of elements the same as the original melt, then the melt is cast for wire rod and rolled to obtain wire rod, wherein during casting the melt for wire rod into the refining reverberatory furnace, additional loading of the melt from copper raw materials is periodically carried out with maintaining the temperature of the melt in the casting bath in the range of 1105 to 1115 °C. 2. The method according to paragraph 1, characterized in that the initial melt for the wire rod is prepared from a charge consisting of copper cathodes with a copper content of at least 99.93%. 3. The method according to paragraph 1, characterized in that the initial melt for the wire rod is prepared from a charge consisting of copper conductors of mechanically separated cable with a copper content of at least 99.91%. 4. The method according to paragraph 1, characterized in that the initial melt for the wire rod is prepared from a charge consisting of copper ingots with a copper content of at least 99.5%. 5. The method according to item 1, characterized in that the additionally loaded melt for wire rod from copper raw materials is prepared from a charge consisting of copper cathodes with a copper content of at least 99.93%. 6. The method according to item 1, characterized in that the additionally loaded melt for the copper raw material rod is prepared from a charge consisting of mechanically separated copper cable with a copper content of at least 99.91%. 7. The method according to item 1, characterized in that the additional loading of melt for the wire rod is carried out in portions from 500 to 2500 kg at intervals of 8-15 minutes. 8. The method according to claim 1, characterized in that after the end of the reduction, the temperature of the melt is reduced to 1100-1120°C by introducing a melt for wire rod from copper raw materials with a content of mass fractions of elements the same as the initial melt with impurities of no more than 0.3%.