Cold forging steel smelting method capable of reducing slag consumption and application of cold forging steel smelting method

Abstract

The invention discloses a cold forging steel smelting method capable of reducing slag consumption and application of the cold forging steel smelting method, and relates to the technical field of steel smelting. Comprising the following steps: after a converter smelting end point and before LF refining, adding casting residue recovery slag and lime into molten steel, and conveying the molten steel into an LF furnace for LF refining. The casting residue recovery slag comprises aluminum-containing steel slag or aluminum-free steel slag, and when the casting residue recovery slag is the aluminum-containing steel slag, the mass ratio of the casting residue recovery slag to the molten steel is (1.4-1.8): 120; and when the casting residue recovery slag is aluminum-free steel slag, the mass ratio of the casting residue recovery slag to the molten steel is (1.0-1.4): 120. According to the method, the casting residue recovery slag left after last continuous casting is recycled, the adding amount of slag materials, especially lime, in the refining process can be reduced, meanwhile, the casting residue recovery slag has a certain temperature, and after the casting residue recovery slag is recycled, the electricity consumption in the refining process can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a smelting method of cold heading steel capable of reducing slag consumption and application thereof. Background Art

[0002] In the process of steelmaking, a large amount of slag is generated in the converter and refining stages, about 1750 to 2000 kg. If these slags are directly discarded as waste after the molten steel is continuously cast, it will cause a waste of resources and increase the cost of waste disposal and the risk of environmental pollution. However, the direct use of these slags will also have a certain impact on the steelmaking process, for example, it may affect the chemical composition of the molten steel and the stability of the smelting process. Therefore, developing a steelmaking method that can effectively utilize waste slags while ensuring the quality of steelmaking is one of the key issues that need to be urgently addressed in this field.

[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 cold heading steel smelting method and application thereof which can reduce slag consumption.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a cold heading steel smelting method with reduced slag consumption, comprising adding casting recovery slag and lime to molten steel after the end of converter smelting and before LF refining, and sending the molten steel to a LF furnace for LF refining.

[0007] The recovered casting slag includes the slag of aluminum-containing steel or the slag of aluminum-free steel. When the recovered casting slag is the slag of aluminum-containing steel, the mass ratio of the recovered casting slag to the mass of molten steel is 1.4-1.8:120; when the recovered casting slag is the slag of aluminum-free steel, the mass ratio of the recovered casting slag to the mass of molten steel is 1.0-1.4:120.

[0008] In an optional embodiment, after the end of converter smelting and before LF refining, the mass ratio of lime added to molten steel to the mass of molten steel is 180-480 kg: 120 t;

[0009] Preferably, when the recovered slag is the slag of aluminum-containing steel, the mass ratio of lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 200-310kg:120t, more preferably 200-250kg:120t; when the recovered slag is the slag of aluminum-free steel, the mass ratio of lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 180-470kg:120t.

[0010] In an optional embodiment, the recycled slag is slag containing aluminum steel.

[0011] In an optional embodiment, the theoretical mass percentage of S in the molten steel after desulfurization of the recovered casting slag is calculated according to the desulfurization rate of the recovered casting slag. When the theoretical mass percentage of S is greater than the standard upper limit of the mass percentage of S in the steel grade, lime is added during LF refining and power transmission.

[0012] The desulfurization rate of the slag of aluminum-free steel is 53-60%, and the desulfurization rate of the slag of aluminum-containing steel is 69-77%.

[0013] In an optional embodiment, after LF refining to obtain LF refined sample 1, and the mass percentage of each component in the molten steel in LF refined sample 1 is less than the standard lower limit of the mass percentage of each component corresponding to the steel grade, metal raw materials are added to the molten steel.

[0014] Preferably, when adding the metal raw material to be melted into the molten steel after taking the LF refined sample 1, the bottom blowing argon flow rate of the molten steel is adjusted to 80-100m 3 / h, stirring time is 120-130s.

[0015] In an optional embodiment, when the mass percentage of Als in LF refined sample 1 is less than the standard lower limit of the mass percentage of Als in the steel grade, the metal raw material includes aluminum wire, and after adding the aluminum wire, lime is added to the molten steel again.

[0016] In an optional embodiment, the theoretical mass percentage of Als in the steel after adding the aluminum wire is the standard upper limit of the mass percentage of Als in the steel + (0.015-0.018%).

[0017] In an optional embodiment, the mass of lime added again after adding the aluminum wire = 800000 × (the standard upper limit of the mass percentage of Als in the steel grade + (0.015-0.018%) - the mass percentage of Als in LF refined sample 1), where the mass of the lime is measured in kg.

[0018] In an optional embodiment, during the LF refining process, the argon flow rate is adjusted to 10-15 m / s when taking the LF refining sample 2. 3 / h, stirring time is 300-400s.

[0019] In a second aspect, the present invention provides an application of a method as described in any one of the aforementioned embodiments in reducing the cost of steel smelting.

[0020] The present invention has the following beneficial effects:

[0021] The present invention provides a cold heading steel smelting method and application thereof for reducing slag consumption. By returning the residual casting slag remaining after the previous continuous casting to the molten steel before LF refining and after the converter smelting, the amount of slag, especially lime, added can be reduced. At the same time, the residual casting slag itself has a certain temperature, and after repeated use, the power consumption of the refining process can be reduced. By controlling the amount of residual casting slag added, the refining cost can be reduced while ensuring the refining quality of the molten steel, and the control difficulty of the refining process is not increased, which is of great significance to the repeated use of residual casting slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a refining cost curve diagram of the recovered casting slag provided by the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0025] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0026] In the traditional steelmaking process, in order to ensure the quality of molten steel, it is usually necessary to add lime, fluorite, synthetic slag and aluminum slag to the molten steel for slag making and refining. The total slag volume is 1750-2000kg. After the refining, refined molten steel is obtained. The refined molten steel is continuously cast into ingots in the continuous casting process, and the remaining slag in the ladle is the recycled slag. In the past, the residual slag was mostly used as waste slag and directly sent to the slag treatment plant for environmental protection treatment. However, after research, it was found that recycling the residual slag for secondary refining can significantly reduce the refining power consumption and reduce the refining cost. However, the inventors also found that the refining and slag making effect of the recycled residual slag is very poor, which will affect the quality of the molten steel.

[0027] Specifically, the inventors have found through preliminary experiments that if the casting slag is fully recycled, the advantage is that all the casting slag is utilized, and there is no waste of casting slag. At the same time, the power consumption of the LF furnace is reduced to the maximum; but the disadvantage is that the casting slag is too much. During the recycling process, the ladle is lifted by the overhead crane, the ladle mouth is turned over, and it flows into the next ladle, so that the slag is oxidized by contact with the air, resulting in an increase in the content of oxides such as aluminum oxide, silicon dioxide and iron oxide in the slag during the smelting of the next molten steel, and the slag is transformed from white cream slag to black or dark green glass slag. In order to achieve the effect of white slag refining, more deoxidizer and lime need to be added to the molten steel to transform the black or dark green glass slag into white cream slag. In order to ensure that the deoxidizer and lime melt and react with impurities in the molten steel, this process will greatly increase the deoxidation cost and slag making cost.

[0028] Therefore, in order to reduce production costs and avoid affecting the quality of molten steel, the inventors proposed the following solution.

[0029] In a first aspect, the present invention provides a cold heading steel smelting method with reduced slag consumption, comprising adding casting recovery slag and lime to molten steel after the end of converter smelting and before LF refining, and sending the molten steel to a LF furnace for LF refining.

[0030] Among them, before LF refining refers to before the molten steel starts to be refined in the LF furnace. Generally, the start of power supply in LF is used as the standard, and the start of refining is when the power supply in LF starts.

[0031] Therefore, the recovered slag and lime can be added to the molten steel during the converter tapping process, or can be added to the molten steel at the end of the converter tapping, as long as it is ensured to be added to the molten steel before the start of LF refining.

[0032] Preferably, lime is added to molten steel during the process of tapping from a converter to ensure that the lime can be quickly dissolved.

[0033] Preferably, lime is added to the molten steel when 1 / 3 to 1 / 2 of the converter is tapped, and other alloys required for the steel grade are added together with lime, such as ferromanganese, ferroaluminum, etc. After the converter is tapped, the casting slag from the previous furnace is added to the molten steel.

[0034] In addition, we learned in practice that since the recycled slag will oxidize and become thinner during the recycling process, the recycled slag is added before LF refining. During the converter steelmaking process, we adjust the viscosity of the slag by adding lime, and there is no need to add additional aluminum-containing deoxidizers, which saves the cost of using slag.

[0035] In an optional embodiment, 500-600 kg of lime is added when the converter is tapping. When the amount of lime added is too low, after the casting waste recovery slag is added, the slag is too thin and the oxides in the slag are too high; when the amount of lime added is too high, the lime is easy to agglomerate during the converter tapping process. After the casting waste recovery slag is added, there is still agglomerated lime, which will affect the slag in the early stage of the LF furnace. Preferably, in order to facilitate the fixed slag amount, 500 kg of slag is added when the converter is tapping.

[0036] At the same time, the recovered slag itself has heat. After adding it into molten steel, it can not only reduce the temperature drop of molten steel, but also improve the effect of slag melting and arc burying in the early stage of LF, thereby reducing the power consumption of LF refining process.

[0037] The addition amount of recycled casting slag has an important influence on the refining process of molten steel. If the addition amount of recycled casting slag is too low, the power consumption and slag consumption of LF refining will increase; if the addition amount of recycled casting slag is too high, the thickness of the slag layer will increase during the LF refining process. On the one hand, during the LF refining process, the stirring time required for the carbon powder to be drawn into the molten steel is longer and the stirring is more difficult, so it is difficult to increase the carbon of the molten steel; on the other hand, since the recycled casting slag has been severely oxidized, more lime and aluminum-containing deoxidizers need to be added to produce the target white slag, which further increases the thickness of the slag layer and further increases the difficulty of increasing the carbon of the molten steel. In addition, as the thickness of the slag layer increases, the heat absorption of the slag also increases, the heating rate of the molten steel slows down, and the power consumption further increases.

[0038] The present invention controls the addition amount of the recovered casting slag within the above range, thereby ensuring the refining effect of molten steel, avoiding an increase in the difficulty of controlling the molten steel refining process, and achieving a reduction in smelting costs.

[0039] Further, the after-casting recycled slag includes aluminum-containing steel slag or aluminum-free steel slag. When the after-casting recycled slag is aluminum-containing steel slag, the mass ratio of the after-casting recycled slag to the mass of molten steel is 1.4-1.8:120; when the after-casting recycled slag is aluminum-free steel slag, the mass ratio of the after-casting recycled slag to the mass of molten steel is 1.0-1.4:120. It should be noted that, whether the after-casting recycled slag is aluminum-containing steel slag or aluminum-free steel slag, the mass ratio of the recycled mass to the mass of molten steel can be 1.4:120.

[0040] Among them, when the acid-soluble aluminum content in the molten steel is greater than 0.006%, it is aluminum-containing steel, and when it is less than or equal to 0.006%, it is aluminum-free steel.

[0041] Aluminum-free steels include screw steel and ordinary carbon steel. The quality requirements of these steels are relatively low. Therefore, it is generally not necessary to produce white slag during refining and slag making. Therefore, the content of oxides such as silicon dioxide, manganese oxide and iron oxide in the slag is relatively high. After the slag of these steels is recovered, the consumption of aluminum elements used for deoxidation increases when smelting the next batch of cold heading steel. Therefore, the more the amount of recycled casting slag is added, the greater the consumption of aluminum-containing deoxidizer and lime.

[0042] The inventors have found that in the LF refining process, taking the 120t molten steel refining process as an example, during the refining process, the total mass of the converter slag + casting recovery slag + LF supplementary slag is in the range of 2.2 to 2.5 tons, which is better for reducing power consumption and controlling molten steel quality. Therefore, the recovery amount of casting recovery slag needs to be strictly controlled.

[0043] Since the composition of molten steel in each furnace is not exactly the same, and the steel grades smelted in adjacent furnaces are not necessarily exactly the same, the recovered slag can be divided into slag containing aluminum steel and slag without aluminum steel according to whether different steel grades contain aluminum.

[0044] Since whether the recycled casting slag contains aluminum has a great influence on the process control of molten steel smelting, it is necessary to control the amount of different types of recycled casting slag added during the smelting of the next batch of molten steel.

[0045] like Figure 1 As shown, when the recycled slag is the slag of aluminum steel, the content of aluminum oxide in the recycled slag is relatively high and the oxide content in the slag is relatively low. Therefore, the addition amount is controlled within the range of 1.4 to 1.8 tons per 120 tons of molten steel. In this way, only a small amount of lime and aluminum-containing deoxidizer is needed to make the viscosity of the slag more suitable and will not affect the refining effect of the molten steel.

[0046] When the recycled slag is the slag of aluminum-free steel, the aluminum oxide content in the recycled slag is low and the oxygen property of the slag is strong, so the slag is thinner. The addition amount needs to be controlled within the range of 1.0-1.4t per 120t of molten steel, and more lime and aluminum-containing deoxidizer are added to make the viscosity of the slag more suitable, which will not affect the refining effect of the molten steel.

[0047] Preferably, the aftercasting recovery slag is the slag of aluminum-containing steel. When the aftercasting recovery slag is the slag of aluminum-containing steel, more slag can be recycled and less lime is needed. When the aftercasting recovery slag is the slag of aluminum-free steel, due to its high oxygen content and thin slag layer, the arc burying ability and the ability to absorb inclusions are poor. In order to ensure the refining effect, it may be necessary to increase the amount of lime. However, it should be noted that even if the amount of lime needs to be increased for the slag of aluminum-free steel, the amount of slag such as lime is still significantly reduced compared to not recycling the aftercasting recovery slag.

[0048] In an optional embodiment, after the end of converter smelting and before LF refining, the mass ratio of lime added to molten steel to the mass of molten steel is 180-480 kg:120 t.

[0049] Preferably, when the recovered slag is the slag of aluminum-containing steel, the mass ratio of lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 200-310kg:120t, more preferably 200-250kg:120t; when the recovered slag is the slag of aluminum-free steel, the mass ratio of lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 180-470kg:120t.

[0050] When the recovered slag is the slag of aluminum-containing steel, the recovery amount of the recovered slag can be controlled within a narrow range. The reason is that after the molten steel arrives at the LF furnace, the capacity of the slag is relatively stable. Therefore, a relatively fixed slag amount can be used to adjust the slag to white cream slag; however, when the recovered slag is the slag of aluminum-free steel, due to the large difference in the deoxidation effect of the slag of the previous furnace, for example, the slag of spiral steel has the highest oxide content, with the total mass percentage of iron oxide and manganese oxide exceeding 3%, while the total mass percentage of iron oxide and manganese oxide in the slag of ordinary carbon steel is about 1.8-3%. If medium carbon steel such as 50LF can be recovered, the total mass percentage of iron oxide and manganese oxide in the slag is about 1-2%, but the total mass percentage of iron oxide and manganese oxide in the slag of aluminum-containing steel is less than 1%. Therefore, the recovery of aluminum-free steel slag has a relatively large range of lime dosage requirements for different types of steel used in the recovered slag.

[0051] In an optional embodiment, the theoretical mass percentage of S in the molten steel after desulfurization of the recovered casting slag is calculated according to the desulfurization rate of the recovered casting slag. When the theoretical mass percentage of S is greater than the standard upper limit of the mass percentage of S in the steel grade, lime is added during LF refining and power transmission.

[0052] The desulfurization rate of the slag of aluminum-free steel is 53-60%, and the desulfurization rate of the slag of aluminum-containing steel is 69-77%.

[0053] For example, assuming that the upper limit of the mass percentage standard of S in a certain type of steel is 0.02%, the recovered slag is the slag of aluminum-free steel, and the desulfurization rate is 60%; when the molten steel discharged from the converter is sampled and tested at the argon station, the mass percentage of S in the molten steel in the argon station sample is 0.04%. According to the desulfurization rate of 60%, the recovered slag can remove S in the molten steel to 0.024%, and 0.024%>0.02%, so it is necessary to add lime to assist the desulfurization of the recovered slag.

[0054] Therefore, it can be understood that when the theoretical mass percentage of S in the molten steel after desulfurization with recycled casting slag is less than or equal to the standard upper limit of the mass percentage of S in the steel grade, lime may not be added during LF refining and power supply, and in the early stage of LF refining, the molten steel is desulfurized only by recycled casting slag.

[0055] That is, if the recycled slag can directly remove the S content in the molten steel to below the upper limit of the S content required by the steel grade, lime can be added only during the converter tapping process before taking refined sample 1 during the LF refining process; if the recycled slag cannot directly remove the S content in the molten steel to below the upper limit of the S content required by the steel grade, lime needs to be added additionally when the LF refining is powered on to ensure the desulfurization effect of the molten steel.

[0056] In addition, the additional lime is added when the LF refining is powered on for the following reasons: the slag basicity is high at the beginning of LF refining, and as the refining progresses, the slag basicity decreases. High slag basicity is beneficial to desulfurization, so in order to increase the utilization rate of lime for desulfurization, it is better to add lime at the beginning of refining.

[0057] For example, before LF refining was powered on, the slag basicity sampled at the argon station was 4.2. When power was supplied to take LF refining sample 1, the slag basicity dropped to 3.8. The same mass of lime (400 kg) was added to the molten steel, and the adding time was after sampling at the argon station and after sampling LF refining sample 1. The lime added after sampling at the argon station could eventually remove the S content in the molten steel from 0.030% to 0.008%, while the lime added after sampling LF refining sample 1 could eventually remove the S content in the molten steel from 0.030% to 0.011%. The desulfurization effect was relatively poor.

[0058] Preferably, the mass of lime added during LF refining and power transmission is calculated according to the mass percentage of S calculated above. 100 kg of lime is required for each 0.003% desulfurization. For example, assuming that the theoretical S content of molten steel after desulfurization of the recovered slag is 0.024%, and the upper limit of the mass percentage of S required by the steel grade is 0.02%, the lime added at this time needs to desulfurize 0.004%, and the amount of lime added is 135 kg.

[0059] In an optional embodiment, after LF refining to obtain LF refined sample 1, and the mass percentage of each component of the molten steel in LF refined sample 1 is less than the standard lower limit of the mass percentage of each component corresponding to the steel grade, metal raw materials are added to the molten steel. The metal raw materials can be various pure metals or alloy raw materials required by the steel grade, such as at least one of aluminum, manganese, and silicon.

[0060] Preferably, when adding the metal raw material to be melted into the molten steel after taking the LF refined sample 1, the bottom blowing argon flow rate of the molten steel is adjusted to 80-100m 3 / h, and the stirring time is 120 to 130 seconds. By controlling the bottom blowing argon gas flow rate within the above range, the metal raw material can be melted quickly.

[0061] In an optional embodiment, when the mass percentage of Als in LF refined sample 1 is less than the standard lower limit of the mass percentage of Als in the steel grade, the metal raw material includes aluminum wire, and after adding the aluminum wire, lime is added to the molten steel again.

[0062] That is, if the Als content in LF refined sample 1 does not meet the steel grade requirements, for example, when the Als content is less than the lower limit of the steel grade requirements, aluminum needs to be added to supplement the acid-melted aluminum in the molten steel. In this process, lime is added again to maintain the calcium-aluminum ratio in the slag, which is conducive to deoxidation and the floating and discharge of deoxidized products. In order to make it easier for operators to calculate the amount of lime added, combined with the calcium-aluminum ratio adsorbed by inclusions in the slag, 8 kg of lime is added for every 0.001% increase in Als.

[0063] Therefore, it can be understood that if the Als content in LF refined sample 1 meets the steel grade requirements, aluminum wire can be omitted and lime can be omitted from being added again.

[0064] Preferably, in order to avoid Als loss in the subsequent refining process, the Als content can be increased at this time to ensure that the element content of the final molten steel meets the requirements. Therefore, the theoretical mass percentage of Als in the steel after adding aluminum wire is the standard upper limit of the mass percentage of Als in the steel + (0.015~0.018%).

[0065] In an optional embodiment, the mass of lime added again after adding the aluminum wire = 800000 × (the standard upper limit of the mass percentage of Als in the steel grade + (0.015-0.018%) - the mass percentage of Als in LF refined sample 1), where the mass of the lime is measured in kg.

[0066] For example, the Als content in LF refined sample 1 is 0.022%, and the upper limit of the Als range required by the steel grade is 0.035%. Therefore, 0.028-0.031% of Als needs to be added, and the corresponding amount of lime required is 224-248 kg.

[0067] In an optional embodiment, during the LF refining process, when taking the LF refining sample 2, the argon flow rate is adjusted to 10-15 m3 / h and the stirring time is 300-400 s to avoid inaccurate sampling.

[0068] In a second aspect, the present invention provides an application of a method as described in any one of the aforementioned embodiments in reducing the cost of steel smelting.

[0069] Example 1

[0070] The present embodiment provides a smelting method for cold heading steel with reduced slag consumption, wherein the element composition of the cold heading steel, measured by mass percentage, includes: 0.06-0.08% carbon, 0-0.08% silicon, 0.20-0.30% manganese, less than 0.025% phosphorus, less than 0.008% sulfur, 0.020-0.035% acid-soluble aluminum, and the remainder is iron and other trace elements, and the mass of the molten steel is 120 tons.

[0071] The specific smelting method is as follows:

[0072] After the molten steel is smelted to the end point in the converter, it is tapped from the converter. 500 kg of lime is added when 1 / 3 of the steel is tapped. After the tapping is completed, 1.2 tons of 50LF steel (aluminum-free steel) casting slag is recovered. Then the molten steel is sampled at the argon station. The composition of the molten steel is shown in Table 1, and the composition of the slag is shown in Table 2.

[0073] Table 1 Content of each component in molten steel sample of argon station (unit: %)

[0074] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.032 0.045

[0075] Table 2 Content of each component of argon station slag sample (unit: %)

[0076] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 52.871 5.146 26.207 0.569 0.583 0.765 4.895 0.017 10.274

[0077] After sampling at the argon station, the molten steel is sent to the LF furnace for LF refining. Since the S content in the argon station sample is 0.032%, the desulfurization rate of the recovered slag of 50LF steel is 57%, and the desulfurization is expected to be 0.032%*0.43=0.0137%. Therefore, the desulfurization capacity of the recovered slag cannot meet the requirement of 0.008% S content in the cold heading steel. It is necessary to add 100 / 0.003%*(0.0137%-0.008%)=190kg of lime for refining and desulfurization, and then the molten steel is powered and LF refining is started until LF refined sample 1 is taken. The composition of the obtained molten steel is shown in Table 3.

[0078] Table 3 Content of various components in molten steel of LF refined sample 1 (unit: %)

[0079] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.013 0.028

[0080] Add 10kg of carbon powder and 240kg of high manganese alloy to the molten steel, and feed 140m of aluminum wire at the same time to make the Als content in the molten steel 0.054%. After feeding the aluminum wire, add lime (0.054%-0.028%) / 0.001%*8=208kg, and then use 80m 3 / h argon gas for 130s, and then turn down the argon gas to 12m 3 / h, LF refined sample 2 was taken, the composition of the molten steel obtained was shown in Table 4, and the composition of the slag was shown in Table 5.

[0081] Table 4 Content of various components in molten steel of LF refined sample 2 (unit: %)

[0082] C Si Mn P S Als 0.0623 0.023 0.228 0.0099 0.006 0.035

[0083] Table 5 Composition content of LF refined sample 2 slag (unit: %)

[0084] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 54.44 3.65 27.41 0.49 0.21 0.887 4.94 0.028 12.215

[0085] Maintain the argon blowing flow rate for 350 s and feed the calcium line to the soft blow station.

[0086] The total amount of lime slag added in the method of this embodiment = 500 + 190 + 208 = 898 kg.

[0087] Example 2

[0088] The present embodiment provides a smelting method for cold heading steel with reduced slag consumption, wherein the element composition of the cold heading steel, measured by mass percentage, includes: 0.06-0.08% carbon, 0-0.08% silicon, 0.20-0.30% manganese, less than 0.025% phosphorus, less than 0.008% sulfur, 0.020-0.035% acid-soluble aluminum, and the remainder is iron and other trace elements, and the mass of the molten steel is 120 tons.

[0089] The specific smelting method is as follows:

[0090] After the molten steel is smelted to the end point in the converter, it is tapped from the converter. 500 kg of lime is added when 1 / 3 of the steel is tapped. After the tapping is completed, 1.3 tons of casting slag of Q345C steel (aluminum-free steel) is recovered. Then the molten steel is sampled at the argon station. The composition of the molten steel is shown in Table 6, and the composition of the slag is shown in Table 7.

[0091] Table 6 Content of each component in argon station molten steel sample (unit: %)

[0092] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.019 0.040

[0093] Table 7 Content of each component of argon station slag sample (unit: %)

[0094] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 56.252 5.104 24.58 0.598 0.086 0.632 5.629 0.021 11.021

[0095] After sampling at the argon station, the molten steel is sent to the LF furnace for LF refining. Since the S content in the argon station sample is 0.019%, the desulfurization rate of the recovered slag of 50LF steel is 60%, and the desulfurization is expected to reach 0.019%*0.4=0.0076%. Therefore, the desulfurization capacity of the recovered slag can meet the requirement of 0.008% S content in cold heading steel, and there is no need to add lime for refining and desulfurization. Then, the molten steel is powered and LF refining is started until LF refined sample 1 is taken. The composition of the obtained molten steel is shown in Table 8.

[0096] Table 8 Content of various components in molten steel of LF refined sample 1 (unit: %)

[0097] C Si Mn P S Als 0.0513 0.003 0.11 0.0089 0.011 0.032

[0098] Add 220kg of high manganese to the molten steel and feed 110m of aluminum wire at the same time to make the Als content in the molten steel 0.054%. After feeding the aluminum wire, add lime (0.054%-0.032%) / 0.001%*8=176kg, and then use 80m 3 / h argon gas for 120s, and then turn down the argon gas to 11m 3 / h, LF refined sample 2 was taken, the composition of the molten steel obtained was shown in Table 9, and the composition of the slag was shown in Table 10.

[0099] Table 9 Content of various components in molten steel of LF refined sample 2 (unit: %)

[0100] C Si Mn P S Als 0.0603 0.033 0.221 0.0099 0.007 0.034

[0101] Table 10 Composition content of slag of LF refined sample 2 (unit: %)

[0102] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 60.946 2.291 27.807 2.887 0.101 0.576 3.292 0.021 26.602

[0103] Maintain the argon blowing flow rate for 350 s and feed the calcium line to the soft blow station.

[0104] The total amount of lime slag added in the method of this embodiment = 500 + 176 = 676 kg.

[0105] Example 3

[0106] The present embodiment provides a smelting method for cold heading steel with reduced slag consumption, wherein the element composition of the cold heading steel, measured by mass percentage, includes: 0.06-0.08% carbon, 0-0.08% silicon, 0.20-0.30% manganese, less than 0.025% phosphorus, less than 0.008% sulfur, 0.020-0.035% acid-soluble aluminum, and the remainder is iron and other trace elements, and the mass of the molten steel is 120 tons.

[0107] The specific smelting method is as follows:

[0108] After the molten steel is smelted to the end point in the converter, it is tapped from the converter. 500 kg of lime is added when 1 / 3 of the steel is tapped. After the tapping is completed, 1.6 tons of casting slag of Q235C steel (containing aluminum steel) is recovered. Then the molten steel is sampled at the argon station. The composition of the molten steel is shown in Table 11, and the composition of the slag is shown in Table 12.

[0109] Table 11 Content of each component in molten steel sample of argon station (unit: %)

[0110] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.038 0.037

[0111] Table 12 Content of each component in argon station slag samples (unit: %)

[0112] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 52.522 4.514 32.935 0.554 0.075 1.389 5.102 0.006 11.635

[0113] After sampling at the argon station, the molten steel is sent to the LF furnace for LF refining. Since the S content in the argon station sample is 0.038%, the desulfurization rate of the recovered slag of 50LF steel is 72%, and the desulfurization is expected to be 0.038%*0.28=0.0106%. Therefore, the desulfurization capacity of the recovered slag cannot meet the requirement of 0.008% S content in the cold heading steel. It is necessary to add 100 / 0.003%*(0.0106%-0.008%)=87kg of lime for refining and desulfurization, and then the molten steel is powered and LF refining is started until LF refined sample 1 is taken. The composition of the obtained molten steel is shown in Table 13.

[0114] Table 13 Content of various components in molten steel of LF refined sample 1 (unit: %)

[0115] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.009 0.025

[0116] Add 10kg of carbon powder and 240kg of high manganese alloy to the molten steel, and feed 140m of aluminum wire at the same time to make the Als content in the molten steel 0.053%. After feeding the aluminum wire, add lime (0.053%-0.025%) / 0.001%*8=224kg, and then use 80m 3 / h argon gas for 130s, and then turn down the argon gas to 12m 3 / h, take LF refined sample 2, the composition of the molten steel obtained is shown in Table 14, and the composition of the slag is shown in Table 15.

[0117] Table 14 LF Refined Sample 2 Molten Steel Component Content (Unit: %)

[0118] C Si Mn P S Als 0.0623 0.023 0.228 0.0099 0.004 0.035

[0119] Table 15 Composition content of LF refined sample 2 slag (unit: %)

[0120] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 53.378 3.088 30.721 0.68 0.04 1.11 4.272 0.007 17.286

[0121] Maintain the argon blowing flow rate for 350 s and feed the calcium line to the soft blow station.

[0122] The total amount of lime slag added in the method of this embodiment = 500 + 87 + 224 = 811 kg.

[0123] Example 4

[0124] The present embodiment provides a smelting method for cold heading steel with reduced slag consumption, wherein the element composition of the cold heading steel, measured by mass percentage, includes: 0.06-0.08% carbon, 0-0.08% silicon, 0.20-0.30% manganese, less than 0.025% phosphorus, less than 0.012% sulfur, 0.020-0.035% acid-soluble aluminum, and the remainder is iron and other trace elements, and the mass of the molten steel is 120 tons.

[0125] The specific smelting method is as follows:

[0126] After the molten steel is smelted to the end point in the converter, it is tapped from the converter. 500 kg of lime is added when 1 / 3 of the steel is tapped. After the tapping is completed, 1.6 tons of casting slag of SWRCH6A steel (containing aluminum steel) is recovered. Then the molten steel is sampled at the argon station. The composition of the molten steel is shown in Table 16, and the composition of the slag is shown in Table 17.

[0127] Table 16 Content of each component in molten steel sample of argon station (unit: %)

[0128] C Si Mn P S Als 0.0463 0.003 0.098 0.0089 0.027 0.041

[0129] Table 17 Content of each component of argon station slag sample (unit: %)

[0130] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 59.773 4.151 22.186 0.716 0.119 0.545 3.846 0.012 14.4

[0131] After sampling at the argon station, the molten steel is sent to the LF furnace for LF refining. Since the S content in the argon station sample is 0.027%, the desulfurization rate of the recovered slag of 50LF steel is 72%, and the desulfurization is expected to reach 0.027%*0.28=0.0075%. Therefore, the desulfurization capacity of the recovered slag can meet the requirement of 0.008% S content in cold heading steel, and there is no need to add lime for refining and desulfurization. Then the molten steel is powered on and LF refining is started until LF refined sample 1 is taken. The composition of the obtained molten steel is shown in Table 18.

[0132] Table 18 Content of various components in molten steel of LF refined sample 1 (unit: %)

[0133] C Si Mn P S Als 0.0493 0.003 0.077 0.0089 0.032 0.035

[0134] Add 300kg of high manganese to the molten steel and feed 95m of aluminum wire at the same time to make the Als content in the molten steel 0.055%. After feeding the aluminum wire, add lime (0.055%-0.035%) / 0.001%*8=160kg, and then use 80m 3 / h argon gas for 120s, and then turn down the argon gas to 12m 3 / h, take LF refined sample 2, the composition of the molten steel obtained is shown in Table 19, and the composition of the slag is shown in Table 20.

[0135] Table 19 Content of various components in molten steel of LF refined sample 2 (unit: %)

[0136]

[0137]

[0138] Table 20 Composition content of slag of LF refined sample 2 (unit: %)

[0139] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe MnO S MgO <![CDATA[P 2 THE 5 ]]> Alkalinity 60.683 4.695 22.957 0.541 0.161 0.486 4.194 0.031 12.925

[0140] Maintain the argon blowing flow rate for 350 s and feed the calcium line to the soft blow station.

[0141] The total amount of lime slag added in the method of this embodiment = 500 + 160 = 660 kg.

[0142] Comparative Example 1

[0143] This comparative example provides a smelting method for cold heading steel, and its steps are similar to those of Example 1, except that no casting recovery slag is added.

[0144] When tapping the converter, add 500kg of lime, 500-700kg of lime (600kg in this comparative example), 300kg of synthetic slag, 100-150kg of fluorite (125kg in this comparative example), 200kg of aluminum slag and 150kg of bauxite.

[0145] The total slag amount = 500 + 600 + 300 + 125 + 200 + 150 = 1875 kg, of which the total amount of lime added is 500 + 600 + 150 = 1250 kg.

[0146] The method of this comparative example consumes a large amount of slag during the refining process, and the slag absorbs a lot of heat when melting, resulting in high power consumption.

[0147] Comparative Example 2

[0148] This comparative example provides a smelting method for cold heading steel, and its steps are similar to those of Example 1, with the only difference being that all the recovered casting slag is added, and the recovered casting slag is aluminum-free slag, and the total recovered weight is 1900 kg.

[0149] When the converter is tapping steel, 500kg of lime and 300kg of bauxite are added. When the LF furnace arrives at the station, 400-700kg of lime (550kg in this comparative example) and 100-150kg of fluorite (125kg in this comparative example) are added.

[0150] Since the amount of recycled casting slag is large and there are more oxides in the slag, more aluminum-containing deoxidizer and lime are required. In the subsequent refining process, an additional 150kg of lime needs to be added.

[0151] The total amount of slag = 500 + 300 + 550 + 125 + 150 = 1625 kg, of which the total amount of lime added is 500 + 550 + 100 = 1200 kg.

[0152] The method of this comparative example consumes a large amount of slag during the refining process, and the slag absorbs a lot of heat when melting, resulting in high power consumption.

[0153] Comparative Example 3

[0154] This comparative example provides a smelting method for cold heading steel, and its steps are similar to those of Example 3, with the only difference being that all the recovered casting slag is added, and the recovered casting slag is slag containing aluminum steel, and the total recovered weight is 2100 kg.

[0155] When the converter is tapping steel, 500 kg of lime is added, 400-700 kg of lime is added to the LF furnace (550 kg in this comparative example), and 100-150 kg of fluorite is added (125 kg in this comparative example).

[0156] Since the amount of recycled casting slag is large and there are more oxides in the slag, more aluminum-containing deoxidizer and lime are required. In the subsequent refining process, an additional 100kg of lime needs to be added.

[0157] The total amount of slag = 500 + 550 + 125 + 100 = 1275 kg, of which the total amount of lime added is 500 + 550 + 100 = 1150 kg.

[0158] The method of this comparative example consumes a large amount of slag during the refining process, and the slag absorbs a lot of heat when melting, resulting in high power consumption.

[0159] Test Example 1

[0160] The methods of Examples 1 to 4 were compared with those of Comparative Examples 1 to 3, and the smelting costs of different methods were calculated to obtain the results shown in Table 21.

[0161] Among them, the unit price of lime is 600 yuan / t, the cost of synthetic slag is 2000 yuan / t, the cost of fluorite is 1500 yuan / t, the cost of aluminum slag is 5500 yuan / t, the cost of bauxite is 1200 yuan / t, the heat absorption of lime or slag is 0.009℃ per kg, and the electricity cost per temperature rise of 1℃ is 25 yuan.

[0162] The calculation method for the total cost of slag consumption in Comparative Example 1 is as follows: the slag absorbs heat, causing the temperature of the molten steel to drop = 1875*0.009 = 16.875°C, the increased heating cost = 16.875*25 = 421.875 yuan, the total slag cost = 500*0.6+600*0.6+300*2+125*1.5+200*5.5+150*1.2 = 2727.5 yuan, the total slag and heating cost = 421.875+2727.5 = 3149.375 yuan.

[0163] The calculation method for the total cost of slag consumption in Comparative Example 2 is as follows: the slag absorbs heat, causing the temperature of the molten steel to drop = 1625*0.009 = 14.625°C, the increased heating cost = 14.625*25 = 365.625 yuan, the total slag cost = 500*0.6+300*1.2+550*0.6+125*1.5+150*0.6 = 1267.5 yuan, the total slag and heating cost = 365.625+1267.5 = 1633.125 yuan.

[0164] The calculation method for the total cost of slag consumption in Comparative Example 3 is as follows: the slag absorbs heat, causing the temperature of the molten steel to drop = 1275*0.009 = 11.475°C, the increased heating cost = 11.475*25 = 286.875 yuan, the total slag cost = 500*0.6+550*0.6+125*1.5+100*0.6 = 877.5 yuan, the total slag and heating cost = 286.875+877.5 = 1164.375 yuan.

[0165] Table 21 Smelting costs of different methods

[0166]

[0167] As can be seen from Table 21, the embodiment of the present invention, whether recycling aluminum-containing steel slag or aluminum-free steel slag, significantly reduces various costs by controlling the amount of recycled casting slag compared to the method of comparative example 1 that does not recycle recycled casting slag. The total cost of the embodiment accounts for about 1 / 6 to 1 / 4 of the total cost of comparative example 1, and no other slag materials other than lime need to be added in the embodiment of the present invention, and the total cost of slag materials is lower; while comparative examples 2 and 3 recycle all the residual casting slag, respectively recycling aluminum-containing steel slag and aluminum-free steel slag, and the total cost of comparative examples 2 and 3 is reduced compared to the case of comparative example 1 without recycling, but the recovery amount of controlled residual casting slag is higher. Therefore, by controlling the amount of residual casting slag added, in combination with the smelting method of the present invention, not only can the quality of molten steel be guaranteed, but also the reduction of refining cost can be achieved, which has better industrial application value.

[0168] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for smelting cold heading steel with reduced slag consumption, characterized in that: It includes adding casting recovery slag and lime to molten steel after the end of converter smelting and before LF refining, and sending the molten steel to the LF furnace for LF refining; The after-casting recovered slag includes slag of aluminum-containing steel or slag of aluminum-free steel. When the after-casting recovered slag is slag of aluminum-containing steel, the mass ratio of the after-casting recovered slag to the mass of molten steel is 1.4-1.8:120; when the after-casting recovered slag is slag of aluminum-free steel, the mass ratio of the after-casting recovered slag to the mass of molten steel is 1.0-1.4:

120.

2. The method according to claim 1, characterized in that: After the end of converter smelting and before LF refining, the mass ratio of the lime added to the molten steel is 180-480 kg: 120 t; Preferably, when the recovered slag is the slag of aluminum-containing steel, the mass ratio of the lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 200-310kg:120t, more preferably 200-250kg:120t; when the recovered slag is the slag of aluminum-free steel, the mass ratio of the lime added to the molten steel after the end of converter smelting and before LF refining to the mass of the molten steel is 180-470kg:120t.

3. The method according to claim 1 or 2, characterized in that: The recovered casting slag is slag containing aluminum steel.

4. The method according to claim 1, characterized in that: Calculating the theoretical mass percentage of S in the molten steel after desulfurization of the recovered casting slag according to the desulfurization rate of the recovered casting slag, and when the theoretical mass percentage of S is greater than the standard upper limit of the mass percentage of S in the steel grade, adding lime during LF refining and power transmission; The desulfurization rate of the aluminum-free steel slag is 53-60%, and the desulfurization rate of the aluminum-containing steel slag is 69-77%.

5. The method according to claim 1 or 4, characterized in that: When the LF is refined to obtain LF refined sample 1, and the mass percentage of each component in the molten steel in the LF refined sample 1 is less than the standard lower limit of the mass percentage of each component in the steel grade, adding metal raw materials to the molten steel; Preferably, when adding the metal raw material to be melted into the molten steel after taking the LF refined sample 1, the bottom blowing argon flow rate of the molten steel is adjusted to 80-100m 3 / h, stirring time is 120-130s.

6. The method according to claim 5, characterized in that When the mass percentage of Als in the LF refined sample 1 is less than the standard lower limit of the mass percentage of Als in the steel grade, the metal raw material includes aluminum wire, and after adding the aluminum wire, lime is further added to the molten steel.

7. The method according to claim 6, characterized in that The theoretical mass percentage of Als in the steel after adding the aluminum wire is the standard upper limit of the mass percentage of Als in the steel + (0.015-0.018%).

8. The method according to claim 6, characterized in that The mass of lime added again after adding the aluminum wire = 800000 × (the standard upper limit of the mass percentage of Als in the steel grade + (0.015-0.018%) - the mass percentage of Als in LF refined sample 1), and the mass of lime is measured in kg.

9. The method according to claim 5, characterized in that During the LF refining process, the argon flow rate was adjusted to 10-15 m / s when taking LF refining sample 2. 3 / h, stirring time is 300-400s.

10. Use of the method according to any one of claims 1 to 9 in reducing steel smelting costs.

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