Method for smelting high-quality steel by using galvanized iron sheet

Abstract

The invention provides a method for smelting high-quality steel by using a galvanized iron sheet, which relates to the technical field of iron and steel smelting, and comprises the following steps: putting waste iron and steel materials into an intermediate frequency furnace, and adding carbon powder after part of molten steel is melted in the intermediate frequency furnace; slagging off; pouring molten steel into a steel ladle, and continuously and strongly blowing argon at the bottom of the steel ladle in the steel pouring process; adding a slagging material along with the steel flow, further oxidizing and removing impurities, and after steel pouring is finished, blowing oxygen to molten steel in the steel ladle from the top of the steel ladle at an oxygen blowing position; deslagging operation is carried out, a new slagging material is supplemented, an aluminum wire is supplemented, an iron alloy is added, and argon blowing is stopped after alloying; in the smelting process, a dust removal system is started for smoke dust recovery; according to the method, waste galvanized iron sheets or raw materials which are not too high in cleanliness are added with more other steel and iron waste, molten steel with high cleanliness is smelted, qualified molten steel is provided for high-quality steel, and the quality of the high-quality steel is improved. And the zinc element is changed into a byproduct of steel smelting to be recycled.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, in particular to a method for smelting high-quality steel by using galvanized iron sheets. Background Art

[0002] Zinc ranks fourth in the world's metal production and consumption, only after steel, aluminum and copper, and is also the non-ferrous metal most closely related to the steel industry. According to statistics, China's annual zinc consumption exceeds 1.5 million tons, of which about 50% of the annual zinc consumption is used in the galvanizing production of steel. In the prior art, the methods used to digest waste galvanized iron sheets mainly include physical and chemical methods to separate zinc from iron, but the recycling cost is high; there are also methods for adding galvanized iron sheets to electric furnaces for smelting steel, but this type of smelting is more harmful to the electric furnace itself, and the proportion of waste galvanized iron sheets is usually not more than 30%. Its production cost is also relatively high, the zinc content in the recycled dust ash is also low, and the selling price of zinc ash is also low, and the overall economic benefits are not high. For similar waste galvanized iron sheets with low cleanliness or raw materials with more other steel waste, the impurity content is high and the zinc recovery rate is low, resulting in low quality of molten steel after treatment, which cannot be used to smelt high-quality steel.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for smelting high-quality steel using galvanized iron sheets, so as to solve the technical problem that there is a lack of a method for smelting steel using galvanized iron sheets in the prior art.

[0005] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0006] The present invention provides a method for smelting high-quality steel using galvanized iron sheets, comprising the following steps:

[0007] A. Put the scrap steel into the medium frequency furnace, start smelting, add carbon powder 1-2 times after some molten steel begins to melt in the medium frequency furnace; control the end point smelting temperature at the liquidus temperature + 100-150°C, then remove the slag to make the scrap steel in a molten clear state; the galvanized iron sheet in the scrap steel accounts for 60-90%;

[0008] B. Place the baked ladle on the ladle position next to the medium frequency furnace, pour the molten steel in the medium frequency furnace into the ladle, and continue to blow argon at the bottom of the ladle during the pouring process; add slag-making materials with the steel flow to make slag and further oxidize and remove impurities; perform slag removal, add new slag-making materials, and then add aluminum wire to deoxidize the molten steel, and add ferroalloy to alloy the molten steel; stop blowing argon 3 to 5 minutes after alloying;

[0009] The oxidation and impurity removal includes adding iron oxide scale while adding slag-making materials along with the steel flow, or after pouring the steel is completed, blowing oxygen into the molten steel in the ladle from the top of the ladle at the oxygen-blowing position to conduct oxidation and impurity removal and slag-making;

[0010] C. Above the intermediate frequency furnace and the ladle position, movable air suction hoods are both provided. The movable air suction hoods are connected to the dust removal system through pipelines. During the melting process of step A or / and step B, the dust removal system is turned on to make the air suction hoods in a negative pressure state for dust recovery treatment, ensuring that the air suction hoods above the intermediate frequency furnace and the ladle position are in a negative pressure state;

[0011] D. The ladle treated in step B is lifted to the VD vacuum furnace for treatment. The temperature of the molten steel when it reaches the VD vacuum furnace is the liquidus temperature + 80 - 100 °C, the clear space above the ladle is 800 - 1000 mm, it is treated for 5 - 10 minutes under the condition that the vacuum degree is less than 67 Pa. For a 100-ton ladle, the bottom blowing argon pressure of the ladle is 0.1 - 0.3 Mpa, and the argon flow rate is 100 - 300 Nl / min; the temperature after the VD vacuum furnace breaks the vacuum is the liquidus temperature + 40 - 60 °C;

[0012] E. For a 100-ton ladle, after the VD vacuum furnace breaks the vacuum, it is softly blown with argon for 10 - 20 min. The soft blowing pressure is 0.2 - 0.3 MPa, the flow rate is 50 - 150 Nl / min, the off-station temperature is the liquidus temperature + 30 - 40 °C, and a heat preservation agent of 0.5 - 1.0 Kg / t is added on the surface of the molten steel, then the ladle is lifted to continuous casting.

[0013] Further, in step A, the addition amount of the carbon powder is 0.3 - 1.0 Kg / t.

[0014] Further, in step B, the internal temperature of the baked ladle is 800 - 1200 °C;

[0015] The conditions for strong argon blowing include blowing argon with a pressure of 0.3 - 0.8 MPa and a blowing flow rate of 100 - 300 Nl / min into the bottom of the ladle.

[0016] Further, in step B, the conditions for oxygen blowing include an oxygen blowing pressure of 0.6 - 1.0 MPa, an oxygen blowing amount of 2000 - 4000 Nm 3 / h, and the oxygen blowing time is 10 - 20 min;

[0017] Preferably, adding slag-making materials along with the steel flow before oxygen blowing includes adding lime and / or fluorite along with the steel flow;

[0018] Preferably, the addition amount of the lime is 10 - 15 Kg / t, and the addition amount of the fluorite is 2 - 4 Kg / t.

[0019] Further, in step B, when adding slag-making materials along with the molten steel flow, the addition amount of the slag-making materials in the iron scale is 6-10 Kg / t of lime and / or 2-4 Kg / t of fluorite, and the addition amount of the iron scale is 5-10 Kg / t.

[0020] Further, in step B, after the further oxidation and impurity removal is completed, it further includes the operation of skimming slag outside the ladle, and after slag removal, the exposed surface of the molten steel in the static state in the furnace is greater than 60%.

[0021] Further, in step B, the slag discharging operation is carried out, new slag-making materials are added, then aluminum wire is added to deoxidize the molten steel, and ferroalloys are added to alloy the molten steel, including that after the slag discharging operation is completed, 1.0-2.0 Kg / t of aluminum wire is fed into the molten steel for deoxidizing the molten steel, 6-10 Kg / t of lime and / or 2-4 Kg / t of fluorite are added to the ladle for slag making, at the same time, ferroalloys are added according to the steel grade composition for alloying the molten steel, and 0.3-0.8 kg / t of aluminum particles are added to the slag layer for deoxidizing the top slag of the ladle;

[0022] Preferably, the ferroalloy includes at least one of silicomanganese alloy, low-carbon ferromanganese, metallic manganese, ferrosilicon, ferrochrome, ferromolybdenum or ferronickel;

[0023] Preferably, stopping argon blowing 3-5 minutes after alloying further includes simultaneously carrying out inspection of the molten steel composition;

[0024] Preferably, if the molten steel composition does not meet the target, secondary adjustment is carried out;

[0025] The secondary adjustment means that if the alloy composition does not reach the target, the corresponding ferroalloy is added again to make the alloy in the molten steel reach the target value.

[0026] Further, in step C, the absolute pressure in the negative pressure state is 50 Pa - 100 Pa.

[0027] Further, in step D, after the ladle is lifted to the VD vacuum furnace, a pre-pumping stage is set, the absolute pressure in the pre-pumping stage is 0.01 - 0.1 atmospheric pressure, the pre-pumping time is controlled to be 5 - 10 minutes, the argon pressure in the pre-pumping stage is 0.1 - 0.2 Mpa, and the argon flow rate is 50 - 150 Nl / min.

[0028] Further, in step D, if the temperature of the molten steel is lower than the liquidus temperature + 35 °C after the VD vacuum furnace breaks the vacuum, the ladle is lifted to the refining furnace for heating up.

[0029] A method for smelting high-quality steel using galvanized iron sheet provided by the present invention, in step A, adding carbon powder to make the melting process in a CO reducing atmosphere, and the overflow of CO from the molten steel has the effect of stirring the molten steel, and promotes the rapid volatilization of zinc vapor in the molten steel; in step B, slag is formed to remove impurities, argon is blown to ensure the melting of the alloy and the uniformity of the composition, and oxygen is blown to further remove impurities; during the treatment processes of step A and step B, zinc is easily vaporized to form zinc vapor and volatilize; in step C, the suction hood of the dust removal system is arranged above the intermediate frequency furnace and the ladle, which can not only suck the zinc vapor volatilized from the molten steel during the processes of step A and step B, but also suck the surrounding air. The inhaled air oxidizes all the zinc vapor into zinc oxide. Zinc oxide does not precipitate liquid substances during the cooling process. Through the heat dissipation of the longer pipeline, zinc oxide can be directly filtered by the bag filter. When all the furnace charges used during the melting process of the intermediate frequency furnace are galvanized iron sheets, about 80-90% of the Zn element in the scrap steel can be recovered. When galvanized iron sheets are not completely used, more than 50% of the zinc oxide-containing dust can still be recovered. In step D, the vacuum holding pressure of the VD vacuum furnace further evaporates the remaining zinc, further reducing the zinc content in the molten steel, ensuring that the smelted steel plate has high strength and toughness. The volatilization process drives the strong stirring of the molten steel, and the efficient removal effect of N and H gases can be obtained in a short time, removing the gases and impurities in the molten steel and improving the quality of the molten steel. In step E, after breaking the vacuum, argon is continuously blown softly to ensure the cleanliness of the molten steel. After being treated by steps A to E, the zinc content in the molten steel is below 0.005%, effectively solving the technical problem that the low melting point element Zn has an adverse effect on the quality of the molten steel. At the same time, more than 50% of the zinc-containing dust containing zinc oxide dust has high economic efficiency in the industrial recovery of zinc, and moreover, the higher the zinc content, the higher the economic value of the industrial recovery of zinc. This method uses an intermediate frequency furnace and a vacuum furnace. For waste galvanized iron sheets with not very high cleanliness or raw materials with a large amount of other steel scraps added, it not only smelts the non-galvanized iron sheets in the scraps into molten steel with high cleanliness, providing qualified molten steel for high-quality steel, but also makes the zinc element become a by-product of steel smelting for recovery. Detailed implementation manners

[0030] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meanings and scopes of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In this application, unless otherwise specified, the use of "or" means "and / or". In addition, the use of the term "comprising" and other forms is non-restrictive.

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0032] It should be noted that the melting point of Zn element is 419 °C and the boiling point is 907 °C. When zinc is melted in an intermediate frequency furnace with carbon powder added, it is easy to vaporize and form zinc vapor and volatilize. If the molten steel is in an oxidizing environment, zinc oxide is easily formed. The melting point and boiling point of zinc oxide are significantly higher than those of steel. If the zinc in the molten steel is oxidized to zinc oxide, then the zinc oxide can only enter the steel slag and form a steel slag with a relatively low melting point with the steel slag. Zinc is diluted by the slag in the steel slag and becomes worthless for recycling; however, zinc vapor is toxic. If zinc vapor enters the recycling system in its elemental form, it is necessary to condense the zinc vapor into a liquid or solid state for recycling, and the operation of the recycling device is prone to failure.

[0033] The present invention provides a method for smelting high-quality steel with galvanized iron sheets, comprising the following steps:

[0034] A. Put scrap steel materials into an intermediate frequency furnace, start melting, and after part of the molten steel starts to melt in the intermediate frequency furnace, add carbon powder in 1-2 times; control the final melting temperature at the liquidus temperature + 100-150 °C to keep the waste materials in a molten state; then skim the slag to make the scrap steel in a molten and clean state; the proportion of galvanized iron sheets in the scrap steel materials is 60-90%;

[0035] B. Place the baked ladle at the ladle position beside the intermediate frequency furnace, pour the molten steel in the intermediate frequency furnace into the ladle, and continuously blow argon strongly at the bottom of the ladle during the steel pouring process; add slag-making materials along with the steel flow to make slag and further oxidize and remove impurities; perform a slag discharge operation, add new slag-making materials, then add aluminum wire to deoxidize the molten steel, and add ferroalloys to alloy the molten steel; stop blowing argon 3-5 minutes after alloying;

[0036] The oxidation and impurity removal include adding iron oxide scale along with the slag-making materials when adding slag-making materials along with the steel flow, or after the steel pouring is completed, blowing oxygen into the molten steel in the ladle from the top of the ladle at the oxygen-blowing position to perform oxidation and impurity removal and slag making;

[0037] C. Above the intermediate frequency furnace and the ladle position, movable suction hoods are provided. The movable suction hoods are connected to the dust removal system through pipelines. During the smelting process of step A or / and step B, the dust removal system is turned on to make the suction hoods in a negative pressure state for smoke and dust recovery treatment, ensuring that the suction hoods above the intermediate frequency furnace and the ladle position are in a negative pressure state. While the dust removal system sucks in flue gas, it also sucks in a large amount of air. After zinc elements evaporate, they are quickly oxidized to zinc oxide in the dust removal system and are captured by the dust removal system. The mass ratio of zinc oxide in the obtained dust removal ash is 55-80%. Among them, more than 90% of the zinc elements in zinc oxide volatilize from the intermediate frequency furnace.

[0038] D. Lift the ladle processed in step B to the VD vacuum furnace for treatment. The temperature of the molten steel when it arrives at the VD vacuum furnace is the liquidus temperature + 80-100°C. The clear space above the ladle is 800-1000 mm. It is treated for 5-10 minutes under the condition that the vacuum degree is less than 67 Pa. For a 100-ton ladle, the bottom blowing argon pressure of the ladle is 0.1-0.3 Mpa, and the argon flow rate is 100-300 Nl / min. For ladles different from 100 tons, it can be adjusted proportionally by comparing with the 100-ton ladle. After the VD vacuum furnace breaks the vacuum, the temperature is the liquidus temperature + 40-60°C. After the molten steel passes through the VD vacuum furnace, the zinc elements in the molten steel further volatilize and enter the VD dust removal system. The zinc content in the molten steel is less than 0.005%.

[0039] E. For a 100-ton ladle, after the VD vacuum furnace breaks the vacuum, it is softly blown with argon for 10-20 min. The soft blowing pressure is 0.2-0.3 MPa, and the flow rate is 50-150 Nl / min, ensuring that the ladle liquid surface fluctuates, but the molten steel is not exposed. The off-station temperature is the liquidus temperature + 30-40°C, and a heat preservation agent of 0.5-1.0 Kg / t is added to the surface of the molten steel, and then it is lifted to continuous casting.

[0040] In step A of the present invention, by adding carbon powder, the smelting process is in a CO reducing atmosphere, and the overflow of CO from the molten steel has the effect of stirring the molten steel and promotes the rapid volatilization of zinc vapor in the molten steel; in step B, slag is formed to remove impurities, argon is blown to ensure the melting of the alloy and the uniformity of the composition, and oxygen is blown to further remove impurities; during the treatment processes of steps A and B, zinc is easily vaporized to form zinc vapor and volatilizes; in step C, the suction hood of the dust removal system is arranged above the intermediate frequency furnace and the ladle, which can not only suck the zinc vapor volatilized from the molten steel during steps A and B, but also suck the surrounding air. The inhaled air oxidizes all the zinc vapor into zinc oxide. Zinc oxide does not precipitate liquid substances during the cooling process. Through the heat dissipation of a longer pipeline, zinc oxide can be directly filtered by a bag filter. When all the furnace charges used during the smelting process of the intermediate frequency furnace are galvanized iron sheets, about 80-90% of the Zn element in the scrap steel can be recovered. When galvanized iron sheets are not completely used, more than 50% of the zinc oxide-containing dust can still be recovered. In step D, the vacuum holding pressure of the VD vacuum furnace further evaporates the remaining zinc, further reducing the zinc content in the molten steel, ensuring that the smelted steel plate has high strength and toughness. The volatilization process drives the strong stirring of the molten steel, and an efficient N and H gas removal effect can be obtained in a short time, removing the gases and impurities in the molten steel and improving the quality of the molten steel. In step E, after breaking the vacuum, argon soft blowing is continued to ensure the cleanliness of the molten steel. After being treated by steps A to E, the zinc content in the molten steel is below 0.005%, effectively solving the technical problem that low-melting-point elements such as Zn have an adverse effect on the quality of the molten steel. At the same time, more than 50% of the zinc-containing dust containing zinc oxide dust has high economic efficiency in industrial zinc recovery. Moreover, the higher the zinc content, the higher the economic value of industrial zinc recovery.

[0041] This method uses an intermediate frequency furnace and a vacuum furnace. For waste galvanized iron sheets with not too high cleanliness or raw materials with a large amount of other steel scraps added, it not only smelts the non-galvanized iron sheets in the scraps into molten steel with high cleanliness, providing qualified molten steel for high-quality steel, but also turns zinc elements into by-products of steel smelting for recovery.

[0042] Among them, the flow rate of the bottom blowing argon gas in the ladle can be, but is not limited to, 100Nl / min, 120Nl / min, 140Nl / min, 160Nl / min, 180Nl / min, 200Nl / min, 220Nl / min, 240Nl / min, 260Nl / min, 280Nl / min or 300Nl / min, or can also be any value between 100 and 300Nl / min.

[0043] The pressure of the soft blowing can be, but is not limited to, 0.2MPa, 0.21MPa, 0.23MPa, 0.25MPa, 0.27MPa, 0.29MPa or 0.3MPa, or can also be any value between 0.2 and 0.3MPa.

[0044] The flow rate of the soft blowing can be, but is not limited to, 50 Nl / min, 60 Nl / min, 70 Nl / min, 80 Nl / min, 90 Nl / min, 100 Nl / min, 120 Nl / min, 140 Nl / min or 150 Nl / min, and can also be any value between 50 and 150 Nl / min.

[0045] It should be noted that Step C ends with the start of heating in Step A and the end of Step B. To further save energy and facilitate control, when the dust removal system is turned on in Step C, the suction hoods above the intermediate frequency furnace and the ladle position do not necessarily always be in a negative pressure state. Corresponding valves are provided for each suction hood, and by opening and closing the corresponding valves, the corresponding suction hoods are in a negative pressure state. For example, during the melting process in the intermediate frequency furnace, the suction hood above the intermediate frequency furnace is in a negative pressure state, while the suction hood above the ladle is closed and in a non - negative pressure state; during the steel pouring process, the suction hoods above the intermediate frequency furnace and the ladle are both in a negative pressure state; after the steel tapping is completed, during the process of adding aluminum wire to the ladle, the suction hood above the ladle is in a negative pressure state, while the suction hood above the intermediate frequency furnace is closed and in a non - negative pressure state.

[0046] In some specific embodiments, in Step A, the addition amount of the carbon powder is 0.3 - 1.0 Kg / t.

[0047] Among them, the addition amount of the carbon powder can be, but is not limited to, adding 0.3 Kg, 0.4 Kg, 0.5 Kg, 0.6 Kg, 0.7 Kg, 0.8 Kg, 0.9 Kg or 1.0 Kg per ton of molten steel, and can also be any value between 0.3 and 1.0 Kg.

[0048] In some specific embodiments, in Step B, the internal temperature of the baked ladle is 800 - 1200 °C; the conditions for the strong argon blowing include blowing argon with a pressure of 0.3 - 0.8 MPa and a blowing flow rate of 100 - 300 Nl / min into the bottom of the ladle.

[0049] Among them, the blowing pressure can be, but is not limited to, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa or 0.8 MPa, and can also be any value between 0.3 and 0.8 MPa.

[0050] The blowing flow rate can be, but is not limited to, 100 Nl / min, 150 Nl / min, 200 Nl / min, 250 Nl / min or 300 Nl / min, and can also be any value between 100 and 300 Nl / min.

[0051] In some specific embodiments, in step B, the conditions for oxygen blowing include an oxygen blowing pressure of 0.6 to 1.0 MPa, an oxygen blowing amount of 2000 to 4000 Nm 3 / h, and an oxygen blowing time of 10 to 20 min;

[0052] Among them, the oxygen blowing pressure can be, but is not limited to, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa or 1.0 MPa, and can also be any value between 0.6 and 1.0 MPa.

[0053] The oxygen blowing amount can be, but is not limited to, 2000 Nm 3 / h, 2300 Nm 3 / h, 2500 Nm 3 / h, 2800 Nm 3 / h, 3000 Nm 3 / h, 3300 Nm 3 / h, 3500 Nm 3 / h, 3800 Nm 3 / h or 4000 Nm 3 / h, and can also be any value between 2000 - 4000 Nm 3 / h.

[0054] The time of the oxygen blowing treatment can be, but is not limited to, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, and can also be any value between 10 and 20 min.

[0055] In some specific embodiments, the slag-making materials added with the molten steel flow before oxygen blowing include adding lime and / or fluorite with the molten steel flow.

[0056] In some specific embodiments, the addition amount of the lime is 10 - 15 Kg / t, and the addition amount of the fluorite is 2 - 4 Kg / t.

[0057] In some specific embodiments, in step B, when adding the slag-making materials with the molten steel flow, the addition amount of the slag-making materials in the iron oxide scale is 6 - 10 Kg / t of lime and / or 2 - 4 Kg / t of fluorite, and the addition amount of the iron oxide scale is 5 - 10 Kg / t.

[0058] In some specific embodiments, in step B, after the further oxidation and impurity removal is completed, it further includes an operation of skimming the slag outside the ladle. After slag removal, the exposed surface of the molten steel in the furnace in the static state is greater than 60%, so as to improve the purity of the molten steel.

[0059] In some specific embodiments, in step B, the slag discharging operation is carried out, new slag-making materials are added, and then aluminum wire is added to deoxidize the molten steel, and ferroalloys are added to alloy the molten steel. After the slag discharging operation, 1.0 - 2.0 Kg / t of aluminum wire is fed into the molten steel for deoxidation, 6 - 10 Kg / t of lime and / or 2 - 4 Kg / t of fluorite is added to the ladle for slag making, and at the same time, ferroalloys are added according to the steel grade composition for alloying the molten steel, and 0.3 - 0.8 kg / t of aluminum particles is added to the slag layer for deoxidizing the top slag of the ladle.

[0060] Among them, the addition amount of the aluminum particles can be, but is not limited to, adding 0.3 Kg, 0.35 Kg, 0.4 Kg, 0.45 Kg, 0.5 Kg, 0.55 Kg, 0.6 Kg, 0.65 Kg, 0.7 Kg, 0.75 Kg or 0.8 Kg per ton of molten steel, or any value between 0.3 - 0.8 Kg.

[0061] The addition amount of the aluminum wire can be, but is not limited to, adding 1.0 Kg, 1.1 Kg, 1.2 Kg, 1.3 Kg, 1.4 Kg, 1.5 Kg, 1.6 Kg, 1.7 Kg, 1.8 Kg, 1.9 Kg or 2.0 Kg per ton of molten steel, or any value between 1.0 - 2.0 Kg.

[0062] Elements corresponding to the steel grade to be prepared are added to ensure that the finally prepared product has the required mechanical properties and chemical properties. In some specific embodiments, the ferroalloy includes at least one of silicomanganese alloy, low-carbon ferromanganese, ferromanganese, ferrosilicon, ferrochrome, ferromolybdenum or ferronickel.

[0063] In some specific embodiments, stopping argon blowing 3 - 5 minutes after alloying further includes simultaneously carrying out inspection of the molten steel composition.

[0064] In some specific embodiments, if the molten steel composition does not meet the target, secondary adjustment is carried out;

[0065] In some specific embodiments, the secondary adjustment includes adding ferroalloys again for alloying the molten steel.

[0066] In some specific embodiments, in step C, the absolute pressure in the negative pressure state is 50 Pa - 100 Pa.

[0067] In some specific embodiments, in step D, after the ladle is hoisted to the VD vacuum furnace, a pre-pumping stage is set. Avoid entering a relatively low vacuum state too quickly and too early, which causes the residual zinc to vaporize rapidly and overflow rapidly from the molten steel in a gaseous form, causing slag and / or molten steel to gush out of the ladle and form a steel overflow accident. Optionally, the absolute pressure of the pre-pumping stage is 0.01 to 0.1 atmospheres, and the pre-pumping time is controlled to be 5 to 10 minutes by controlling the air breaker valve. The argon pressure of the pre-pumping stage is 0.1 to 0.2 MPa, and the argon flow rate is 50 to 150 Nl / min.

[0068] In some specific embodiments, in step D, if the temperature of the molten steel is lower than the liquidus temperature + 35°C after the VD vacuum furnace is vented, the refining furnace is suspended to increase the temperature to obtain qualified molten steel.

[0069] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0070] Example 1: Smelting steel grade Q420GJC

[0071] The required composition of the steel grade is: C: 0.14~0.17%, Si: 0.15~0.30%, Mn: 1.40~1.50%, Nb: 0.02~0.03%, P: ≤0.025%, S: ≤0.010%, and other alloy components are omitted.

[0072] Preparation of galvanized iron sheet: prepare 18 tons of broken scrap steel and 80 tons of clean galvanized briquettes (zinc content of about 2.1%).

[0073] 1) Start smelting, put 18 tons of scrap steel into the medium frequency furnace to protect the furnace lining and speed up the melting rate, and then add 80 tons of clean galvanized briquettes. After some molten steel begins to melt in the medium frequency furnace, add 80 kg of carbon powder twice to ensure that the smelting process is in a reducing atmosphere.

[0074] 2) Mobile suction hoods are installed above the medium frequency furnace and the ladle. The mobile suction hoods are connected to the dust removal system through pipelines. During the entire smelting process, as the medium frequency furnace is turned on, the dust removal system is turned on accordingly to recover the smoke and treat the smoke, ensuring that the suction hoods above the medium frequency furnace and the ladle are in a negative pressure state with a relative atmospheric pressure of 90Pa. While sucking out the smoke, the dust removal system also sucks in a large amount of air. After evaporation, the zinc element is rapidly oxidized into zinc oxide in the dust removal system and captured by the dust removal system.

[0075] The melting point of the intermediate frequency furnace is 1665℃, and then the slag is removed to make the scrap steel in a molten clear state, with the exposed area of ​​molten steel being 70%. At this time, sampling and testing show that the composition of the molten steel is: C: 0.17%, Zn: 0.141%.

[0076] 3) Place the baked ladle on the ladle position next to the medium frequency furnace, pour the molten steel in the medium frequency furnace into the ladle, and blow argon at a pressure of 0.4MPa and a flow rate of 200Nl / min at the bottom of the ladle; add 600Kg of iron oxide, 820Kg of lime, and 270Kg of fluorite along with the pouring steel flow; during the pouring process, as the iron oxide is added and reacts, a large amount of white zinc oxide dust is generated on the top of the ladle and is captured by the dust removal system. After the slag making of the ladle is completed, the ladle is deslagging.

[0077] 150 kg of aluminum wire was added to the ladle for deoxidation; at this time, the composition of the molten steel was tested and the Zn content was 0.04%.

[0078] 1500Kg of silicon-manganese alloy, 400Kg of medium carbon ferromanganese, 150Kg of ferrosilicon and 35Kg of ferroniobium were added to the ladle for alloying of molten steel, and 50kg of aluminum particles were added for deoxidation of the ladle top slag.

[0079] Argon blowing operation of ladle: During the ladle slag making, deoxidation and alloying process, strong argon blowing operation is maintained, with argon flow rate of 225Nl / min and pressure of 0.7Mpa. Argon blowing is stopped 5 minutes after the deoxidation and alloying is completed. At this time, the temperature of the molten steel is measured, and the temperature is 1613℃.

[0080] 4) The molten steel is hoisted to the VD vacuum furnace for treatment. The temperature of the molten steel in the vacuum furnace is 1609°C. At this time, the ladle clearance is detected to be 830mm. After the ladle is transferred into the VD vacuum furnace, a pre-pumping stage is set with an absolute pressure of 0.01 to 0.1 atmospheres. The vacuum degree and pre-pumping time are controlled for 8 minutes by continuously controlling the air breaker valve. In the pre-pumping stage, the pressure of argon blown from the bottom of the ladle is 0.1MPa, and the argon flow rate is 70Nl / min to avoid entering a lower vacuum state too quickly and too early, which causes the residual zinc to vaporize rapidly and overflow rapidly from the molten steel in the form of gas, causing slag and molten steel to gush out of the ladle and form a steel overflow accident. Then it is treated for 8 minutes under a vacuum degree of 30Pa, and argon is blown from the bottom of the ladle at 200Nl / min; the molten steel passes through the VD vacuum furnace, and the zinc element in the molten steel further volatilizes. The temperature of the VD vacuum furnace is 1562℃ after breaking the air. After soft argon is blown again for 10 minutes, 40kg of carbonized rice husk is added, and the molten steel is hoisted to the continuous casting machine for casting operation.

[0081] Before the molten steel leaves the station, samples are taken for testing. At this time, the zinc content in the molten steel is 0.002%, and the other components of the molten steel are: C: 0.15%, Si: 0.23%, Mn: 1.42%, P: 0.018%, S: 0.002%, and Nb: 0.025%.

[0082] High zinc dust ash: The dust ash obtained from 98 tons of raw materials in the bag filter is shown in Table 1.

[0083] Table 1

[0084] Classification Total Zn content Total ash amount (t) Ash amount generated per ton of steel (Kg / t) High-Zn dust removal ash 69.50％ 2.37 24.2

[0085] Example 2: Smelting Steel Grade Q460qC

[0086] The required composition of the steel grade is as follows: C: 0.14 - 0.17%, Si: 0.15 - 0.30%, Mn: 1.35 - 1.50%, Nb: 0.02 - 0.04%, V: 0.04 - 0.05%, P: ≤0.020%, S: ≤0.005%, and other alloy components are omitted.

[0087] Preparation of galvanized iron sheet: Prepare 15 tons of scrap steel chips and 83 tons of clean galvanized briquettes (zinc content is about 1.9%).

[0088] 1) Start smelting. First, charge 15 tons of scrap steel chips into the intermediate frequency furnace to protect the furnace lining and accelerate the melting rate, and then add 83 tons of clean galvanized briquettes. After partial molten steel appears in the intermediate frequency furnace, add 90 Kg of carbon powder in two portions to ensure a reducing atmosphere during the smelting process.

[0089] 2) Install movable suction hoods above the intermediate frequency furnace and the ladle position (including the ladle oxygen-blowing position). The movable suction hoods are connected to the dust removal system through pipelines. During the entire smelting process, when the intermediate frequency furnace is started, the dust removal system is correspondingly started for smoke and dust recovery treatment to ensure that the suction hoods above the intermediate frequency furnace and the ladle position are in a negative pressure state, with a relative atmospheric pressure of 50 Pa. While the dust removal system is sucking in flue gas, it also sucks in a large amount of air. After the zinc element evaporates, it is quickly oxidized to zinc oxide in the dust removal system and captured by the dust removal system;

[0090] The melting end temperature of the intermediate frequency furnace is 1665°C, and then slag is skimmed to make the scrap steel in a molten and clean state, with the exposed area of the molten steel being 60%; at this time, a sample is taken for testing, and the composition of the molten steel is: C: 0.18%, Zn: 0.132%.

[0091] 3) Place the preheated ladle on the ladle position beside the intermediate frequency furnace, and pour the molten steel in the intermediate frequency furnace into the ladle. Argon gas with a bottom blowing pressure of 0.3 MPa and a flow rate of 120 Nl / min is blown into the ladle; 1100 Kg of lime and 280 Kg of fluorite are added along with the steel flow during the steel pouring.

[0092] Lift the ladle to the oxygen-blowing position for oxygen-blowing operation. The oxygen-blowing pressure is 0.7 MPa, the oxygen-blowing volume is 3000 Nm 3 / h, and the oxygen-blowing time is 18 min; after oxygen-blowing, slag is discharged, and then 650 Kg of lime and 200 Kg of fluorite are added. The composition of the molten steel is detected: Zn: 0.03%, C: 0.07%, P: 0.010%. After slag formation is completed, 155 Kg of aluminum wire is added for deoxidation.

[0093] 1530Kg of silicon-manganese alloy, 300Kg of medium carbon ferromanganese, 160Kg of ferrosilicon, 35Kg of ferroniobium, 70Kg of ferrovanadium were added to the ladle, and 53kg of aluminum particles were added to carry out the ladle top slag deoxidation operation.

[0094] Argon blowing operation of ladle: During the slag making, deoxidation and alloying process of the ladle, maintain strong blowing operation, with argon flow rate of 230Nl / min and pressure of 0.7Mpa, to carry out molten steel deoxidation and slag making and inclusion removal operations. Stop argon blowing 4 minutes after the deoxidation and alloying are completed; at this time, measure the molten steel temperature at 1600℃.

[0095] 4) The molten steel is hoisted to the VD vacuum furnace for treatment. The temperature of the molten steel in the vacuum furnace is 1590°C. At this time, the ladle clearance is detected to be 850mm. After the ladle is transferred into the VD vacuum furnace, a pre-pumping stage is set with an absolute pressure of 0.01 to 0.1 atmospheres. The vacuum degree and pre-pumping time are controlled for 7 minutes by continuously controlling the air breaker valve. In the pre-pumping stage, the pressure of argon blown at the bottom of the ladle is 0.2MPa, and the argon flow rate is 150Nl / min to avoid entering a lower vacuum state too quickly and too early, which causes the residual zinc to vaporize rapidly and overflow rapidly from the molten steel in the form of gas, causing slag and molten steel to gush out of the ladle and form a steel overflow accident. Then it is treated for 8 minutes under a vacuum degree of 35Pa, and argon is blown from the bottom of the ladle at 210Nl / min; the molten steel passes through the VD vacuum furnace, and the zinc element in the molten steel further volatilizes. The temperature of the VD vacuum furnace is 1550℃ after breaking the air. After the molten steel is lifted to LF for heating, argon is soft-blown again for 10 minutes, and 40kg of carbonized rice husk is added. The molten steel is lifted to the continuous casting machine for pouring.

[0096] Before the molten steel leaves the station, samples are taken for testing. At this time, the zinc content in the molten steel is 0.002%, and the other components of the molten steel are: C: 0.14%, Si: 0.23%, Mn: 1.40%, P: 0.011%, S: 0.002%, Nb: 0.025%, and V: 0.045%.

[0097] High zinc dust ash: The production of high zinc dust ash from 98 tons of raw materials is shown in Table 2.

[0098] Table 2

[0099] Classification Total Zn content Total ash amount (t) Ash amount generated per ton of steel (Kg / t) High-Zn dust removal ash 59.80％ 2.23 22.8

[0100] Example 3: Smelting steel grade Q690D

[0101] The required composition of the steel grade is: C: 0.09~0.12%, Si: 0.15~0.30%, Mn: 1.35~1.50%, Ni: 0.2~0.3%, Nb: 0.02~0.04%, V: 0.04~0.05%, P: ≤0.015%, S: ≤0.005%, and other alloy components are omitted.

[0102] Galvanized iron sheet preparation: Prepare 30 tons of scrap steel chunks and 68 tons of clean galvanized briquettes (zinc content is about 2.2%).

[0103] 1) Start melting. First, charge 30 tons of scrap steel chunks into the medium-frequency furnace to protect the furnace lining and accelerate the melting rate, and then add 68 tons of clean galvanized briquettes. After some molten steel starts to form in the medium-frequency furnace, add 100 Kg of carbon powder in two portions to ensure a reducing atmosphere during the melting process.

[0104] 2) Install movable suction hoods above the medium-frequency furnace and the ladle positions (including the ladle oxygen-blowing position). The movable suction hoods are connected to the dust removal system through pipes. During the entire melting process, when the medium-frequency furnace is started, the dust removal system is correspondingly started for flue gas recovery treatment to ensure that the suction hoods above the medium-frequency furnace and the ladle positions are in a negative pressure state, with a relative atmospheric pressure of 60 Pa. While the dust removal system sucks in flue gas, it also sucks in a large amount of air. After the zinc element evaporates, it is quickly oxidized to zinc oxide in the dust removal system and is captured by the dust removal system.

[0105] The melting end temperature of the medium-frequency furnace is 1668 °C, and then slag is skimmed to make the scrap steel in a molten and clean state, with the exposed area of the molten steel being 80%; at this time, a sample is taken for testing, and the composition of the molten steel is: C: 0.18%, Zn: 0.148%, P: 0.026%.

[0106] 3) Place the preheated ladle on the ladle position beside the medium-frequency furnace, and pour the molten steel in the medium-frequency furnace into the ladle. Argon gas with a bottom-blowing pressure of 0.3 MPa and a flow rate of 130 Nl / min is blown into the ladle; 1150 Kg of lime and 290 Kg of fluorite are added along with the pouring steel stream.

[0107] Since the impurity content in the molten steel exceeds the standard, the ladle needs to be lifted to the oxygen-blowing position for oxygen-blowing operation. The oxygen-blowing pressure is 0.8 MPa, the oxygen-blowing volume is 3200 Nm 3 / h, and the oxygen-blowing time is 19 min; after oxygen-blowing, slag is discharged, and then 690 Kg of lime and 220 Kg of fluorite are added to test the composition of the molten steel, Zn: 0.03%, C: 0.06%, P: 0.008%.

[0108] Add 1480 Kg of silicomanganese alloy, 200 Kg of medium-carbon ferromanganese, 130 Kg of ferrosilicon, 40 Kg of ferro-niobium, 75 Kg of ferro-vanadium, 250 Kg of nickel plate to the ladle, and add 50 kg of aluminum pellets for ladle top slag deoxidation operation.

[0109] Ladle argon-blowing operation: During the ladle slag-making, deoxidation, and alloying processes, maintain a strong blowing operation with an argon gas flow rate of 230 Nl / min and a pressure of 0.6 Mpa to carry out molten steel deoxidation and slag-making for inclusion removal operations. Stop blowing argon 4 minutes after the deoxidation and alloying are completed. At this time, measure the temperature of the molten steel, and the measured temperature is 1608 °C.

[0110] 4) The molten steel is hoisted to a VD vacuum furnace for treatment. The temperature of the molten steel in the vacuum furnace is 1601°C. At this time, the clearance of the ladle is detected to be 900mm. Before vacuum treatment, 40Kg of aluminum wire is fed again. A pre-pumping stage is set in the VD vacuum furnace with an absolute pressure of 0.01 to 0.1 atmospheres. The vacuum degree and pre-pumping time are controlled for 7 minutes by continuously controlling the air breaker valve. During the pre-pumping stage, the pressure of argon blown from the bottom of the ladle is 0.13MPa, and the argon flow rate is 83Nl / min to avoid entering a lower vacuum state too quickly and too early, which causes the residual zinc to vaporize rapidly and overflow rapidly from the molten steel in the form of gas, causing slag and molten steel to gush out of the ladle and form a steel overflow accident. Then it is treated for 8 minutes under a vacuum degree of 38Pa, and argon is blown from the bottom of the ladle at 230Nl / min; the molten steel passes through the VD vacuum furnace, and the zinc element in the molten steel further volatilizes. The temperature of the VD vacuum furnace is 1560℃ after breaking the air. After soft argon blowing for 10 minutes, 60kg of carbonized rice husk is added, and the molten steel is hoisted to the continuous casting machine for casting operation.

[0111] Before the molten steel leaves the station, samples are taken for testing. At this time, the zinc content in the molten steel is 0.002%, and the other components of the molten steel are: C: 0.10%, Si: 0.23%, Mn: 1.41%, P: 0.010%, S: 0.002%, Nb: 0.026%, V: 0.047%, Ni: 0.025%.

[0112] High zinc dust ash: The production of high zinc dust ash from 98 tons of raw materials is shown in Table 3.

[0113] Table 3

[0114] Classification Total Zn content Total ash amount (t) Ash amount generated per ton of steel (Kg / t) High-Zn dust removal ash 70.80％ 2.62 27.8

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for smelting high-quality steel with galvanized iron sheet, characterized in that, It includes the following steps: A. Put scrap steel into the intermediate frequency furnace and start melting. After partial molten steel appears in the intermediate frequency furnace, add carbon powder in 1 - 2 times. Control the final melting temperature at the liquidus temperature + 100 - 150°C, then skim the slag to make the scrap steel in a fully melted state. The proportion of galvanized iron sheet in the scrap steel is 60 - 90%; B. Place the baked ladle at the ladle position beside the intermediate frequency furnace, pour the molten steel in the intermediate frequency furnace into the ladle, and continuously blow argon strongly at the bottom of the ladle during the steel pouring process. Add slag-making materials along with the steel flow to make slag, and further oxidize and remove impurities. Conduct slag removal operation, add new slag-making materials, then add aluminum wire to deoxidize the molten steel, and add ferroalloys to alloy the molten steel. Stop blowing argon 3 - 5 minutes after alloying; The oxidation and impurity removal include adding iron oxide scale along with the slag-making materials along with the steel flow, or after the steel pouring ends, blowing oxygen into the molten steel in the ladle from the top of the ladle at the oxygen-blowing position to conduct oxidation and impurity removal and slag making; C. Install movable suction hoods above both the intermediate frequency furnace and the ladle position. The movable suction hoods are connected to the dust removal system through pipelines. During the melting process of step A or / and step B, turn on the dust removal system to make the suction hoods in a negative pressure state for flue dust recovery treatment, ensuring that the suction hoods above the intermediate frequency furnace and the ladle position are in a negative pressure state; D. Lift the ladle processed in step B to the VD vacuum furnace for treatment. The temperature of the molten steel when it reaches the VD vacuum furnace is the liquidus temperature + 80 - 100°C, the clear space above the ladle is 800 - 1000mm. Under the condition that the vacuum degree is less than 67Pa, treat for 5 - 10 minutes. For a 100-ton ladle, the argon gas blowing pressure at the bottom of the ladle is 0.1 - 0.3Mpa, and the argon gas flow rate is 100 - 300Nl / min; the temperature of the VD vacuum furnace after breaking the vacuum is the liquidus temperature + 40 - 60°C; E. For a 100-ton ladle, after the VD vacuum furnace breaks the vacuum, softly blow with argon for 10 - 20min, the soft blowing pressure is 0.2 - 0.3MPa, the flow rate is 50 - 150Nl / min, the off-site temperature is the liquidus temperature + 30 - 40°C, and add 0.5 - 1.0Kg / t of heat preservation agent on the surface of the molten steel, then lift the ladle to continuous casting.

2. The method according to claim 1, wherein In step A, the addition amount of the carbon powder is 0.3 - 1.0Kg / t.

3. The method according to claim 1, wherein In step B, the internal temperature of the baked ladle is 800 - 1200°C; The conditions for the strong argon blowing include blowing argon with a pressure of 0.3 - 0.8MPa and a blowing flow rate of 100 - 300Nl / min into the bottom of the ladle.

4. The method according to claim 1, characterized in that In step B, the conditions for oxygen blowing include an oxygen blowing pressure of 0.6 to 1.0 MPa, an oxygen blowing amount of 2000 to 4000 Nm 3 / h, and an oxygen blowing time of 10 to 20 minutes; Preferably, adding slag-making materials along with the steel flow before oxygen blowing includes adding lime and / or fluorite along with the steel flow; Preferably, the addition amount of the lime is 10 - 15Kg / t, and the addition amount of the fluorite is 2 - 4Kg / t.

5. The method according to claim 1, wherein In step B, when adding iron oxide scale while adding slag-making materials along with the steel flow, the addition amount of the slag-making materials is 6 - 10Kg / t of lime and / or 2 - 4Kg / t of fluorite, and the addition amount of the iron oxide scale is 5 - 10Kg / t.

6. The method according to claim 1, characterized in that In step B, after the further oxidation and impurity removal is completed, it also includes skimming the slag outside the ladle. After slag removal, the exposed surface of the molten steel in the static state in the furnace is greater than 60%.

7. The method according to claim 1, characterized in that In step B, the slag discharging operation is carried out, new slag-making materials are added, then aluminum wire is added to deoxidize the molten steel, and ferroalloys are added to alloy the molten steel, including that after the slag discharging operation, 1.0 - 2.0 Kg / t of aluminum wire is fed into the molten steel for deoxidation, 6 - 10 Kg / t of lime and / or 2 - 4 Kg / t of fluorite is added to the ladle for slag making, at the same time, ferroalloys are added according to the steel grade composition for alloying the molten steel, and 0.3 - 0.8 kg / t of aluminum particles is added to the slag layer for deoxidizing the top slag of the ladle; Preferably, the ferroalloy includes at least one of ferrosilicon manganese alloy, low-carbon ferromanganese, metallic manganese, ferrosilicon, ferrochrome, ferromolybdenum or ferronickel; Preferably, stopping argon blowing 3 - 5 minutes after alloying also includes simultaneously carrying out inspection of the molten steel composition; Preferably, if the molten steel composition does not meet the target, secondary adjustment is carried out; The secondary adjustment means that if the alloy composition does not reach the target, the corresponding ferroalloy is added again to make the alloy in the molten steel reach the target value.

8. The method according to claim 1, characterized in that, In step C, the absolute pressure in the negative pressure state is 50 Pa - 100 Pa.

9. The method according to claim 1, characterized in that, In step D, after the ladle is lifted to the VD vacuum furnace, a pre-pumping stage is set, the absolute pressure in the pre-pumping stage is 0.01 - 0.1 atmospheres, the pre-pumping time is controlled to be 5 - 10 minutes, the argon pressure in the pre-pumping stage is 0.1 - 0.2 Mpa, and the argon flow rate is 50 - 150 Nl / min.

10. The method according to claim 1, characterized in that, In step D, if the temperature of the molten steel is lower than the liquidus temperature + 35°C after the VD vacuum furnace breaks the vacuum, the ladle is lifted to the refining furnace for heating up.