TW202246529A - Method of electric furnace steelmaking - Google Patents

Abstract

The present invention relates to a method of an electric furnace steelmaking. By a specific order of a distributing procedure for materials and a specific total usage amount of steel slags and / or slag iron, the method of the electric furnace steelmaking can produce basic furnace slags to facilitate melting the steel slags and / or the slag iron, and early bubble the furnace slags, thereby saving electricity and enhancing effect of dephosphorization.

Description

electric furnace steelmaking method

The present invention relates to an electric furnace steelmaking method, and in particular to an electric furnace steelmaking method with high dephosphorization effect and energy saving.

The method of electric furnace steelmaking uses external electric energy and uses electrode rods as heat sources, so it can provide enough energy to melt raw materials. Furthermore, the method of electric furnace steelmaking can carry out steps such as decarburization and dephosphorization to remove impurities to ensure the quality of the molten steel produced. The combustion generated by high oxygen is used to remove the carbon of the molten iron, and the slag is used to remove iron. phosphorus in water.

Traditionally, the material distribution step of the electric furnace steelmaking method is to first add steel slag and/or iron slag into the electric furnace, then provide steel scrap on the steel slag and iron slag, and then add additives such as lime (also called auxiliary raw materials). Use scrap steel to hold steel slag and iron slag at the bottom of the electric furnace, so that steel slag and iron slag can contact molten iron earlier, thereby promoting the melting of steel slag and iron slag. However, since the melting point of steel slag and iron slag (about 1900°C to 2000°C) is higher than that of steel scrap, and the heat transfer rate of steel slag and iron slag is relatively slow, only the steel slag and iron slag near the electrode rod (ie heat source) are melted melt. If you want to melt the whole steel slag/iron slag, you need to consume a lot of electric energy, but affected by the poor heat transfer efficiency, it is easy to have defects such as melting and residual unmelted lumps at the end of smelting. Secondly, the liquid-phase molten steel produced by melting steel scrap is blocked between the steel slag (and/or iron slag) and the slag. This causes chemical diffusion between the steel slag (and/or iron slag) and the slag cannot be carried out, and the melting point of the steel slag and iron slag cannot be lowered, thus reducing the melting efficiency. Furthermore, unmelted steel slag and iron slag lead to the inability to completely remove phosphorus in molten steel, resulting in rephosphorization of molten steel and reducing the dephosphorization effect. In addition, more electricity must be applied to melt the remaining unmelted steel slag and slag iron of large size.

Although lime is added to the electric furnace at the initial stage of steelmaking (about 5 to 20 minutes from the start of steelmaking), the lime is above the scrap steel, so it must be after the scrap steel is melted (at least part of the scrap steel is melted) before the lime can contact the molten steel. At this time, the lime can chemically diffuse and contact the slag containing iron oxide in the molten steel to form foamed slag. In other words, the foaming of slag occurs in the middle and late stages of steelmaking (40 minutes after steelmaking), when the basicity of slag (that is, the ratio of the weight of calcium oxide divided by the weight of silicon dioxide) is less than 1 (that is, the content of SiO ₂ in the slag is greater than that of CaO). This kind of slag is usually called acid slag, and at this time (when the lime touches molten steel), the temperature of the electric furnace has risen to a temperature unfavorable for dephosphorization (for example: higher than 1550 ° C), so the traditional electric furnace steelmaking method cannot effectively dephosphorize. phosphorus.

Another distributing step involves embedding lime in scrap steel. Although it can improve the dephosphorization effect, it is necessary to add a lime silo in the scrap pit (that is, the storage place for scrap steel), which increases the equipment cost and reduces the storage space for scrap steel.

In view of this, there is an urgent need to develop a new electric furnace steelmaking method to improve the above-mentioned shortcomings of the conventional electric furnace steelmaking method.

In view of the above problems, one aspect of the present invention is to provide a method for electric furnace steelmaking. With a specific sequence of distributing steps and a specific total amount of steel slag and/or iron slag used, this electric furnace steelmaking method can generate basic slag to help melt steel slag and iron slag, and foam the slag early, thereby saving Electric energy and improve the dephosphorization effect.

According to an aspect of the present invention, a method for electric furnace steelmaking is proposed. The electric furnace steelmaking method includes a cloth distributing step and a slagging step. The distributing step is to feed oxygen and natural gas into the electric furnace, the volume ratio of oxygen and natural gas is 1.5 to 2.5, and the distributing step includes providing steel scrap, providing steel slag and/or iron slag on the scrap steel and providing molten iron into the electric furnace. Based on the total weight of steel scrap, steel slag, iron slag and molten iron being 100% by weight, the total usage of steel slag and iron slag is 5% by weight to 15% by weight. The slagging step increases the volume ratio to greater than 2.5 and is less than or equal to 10, and the slagging step includes adding additives into the electric furnace and blowing carbon powder into the electric furnace to obtain slag and molten steel. Based on the weight of the molten steel as 100% by weight, the amount of tapping phosphorus in the molten steel is not more than 0.03% by weight.

According to an embodiment of the present invention, based on the total weight of steel scrap, steel slag, iron slag and molten iron being 100% by weight, the amount of steel scrap used is 30% by weight to 90% by weight.

According to another embodiment of the present invention, the composition of the steel slag includes calcium oxide and silicon dioxide, and the basicity of the steel slag is 3.0 to 5.0.

According to yet another embodiment of the present invention, the composition of the iron slag includes calcium oxide and silicon dioxide, and the basicity of the iron slag is 3.0 to 5.0.

According to yet another embodiment of the present invention, based on the total phase ratio of the slag being 100%, the solid phase ratio of the slag is 5% to 10%.

According to yet another embodiment of the present invention, the basicity of the slag is 2.0 to 3.0.

According to another embodiment of the present invention, the dephosphorization temperature of the slag is 1450°C to 1560°C.

According to yet another embodiment of the present invention, based on the total weight of 100% by weight, the additive is used in an amount of 5% by weight to 13% by weight.

According to yet another embodiment of the present invention, the additive comprises lime, magnesia, cement, marble, serpentine, dolomite, feldspar, mica and/or talc.

According to yet another embodiment of the present invention, after the molten iron is provided, the method for electric furnace steelmaking further includes a step of transmitting electricity.

The method of applying the electric furnace steelmaking method of the present invention, wherein steel scrap is provided first, and then steel slag and/or slag iron is provided on the scrap steel, and molten iron is provided in a specific order to carry out the material distribution step of the electric furnace steelmaking method, and a specific The total amount of steel slag and iron slag is used to produce basic slag, which helps to melt steel slag and iron slag, and foams the slag in advance, so that dephosphorization can be carried out at low temperature, so this method can save electric energy and improve the dephosphorization effect.

The making and using of embodiments of the invention are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are illustrative only and do not limit the scope of the invention.

The scrap steel referred to in the present invention refers to general household scrap steel (for example: iron and steel components of discarded furniture), factory scrap steel (for example: steel scrap produced in the production process), scrapped vehicles (for example: steel components of ships and vehicles) or other scrap steel components in which the iron content of the scrap averages between 85% and 95% based on the total weight of the scrap being 100%.

The steel slag referred to in the present invention refers to the slag produced by raking slag after the steelmaking process, and based on the total weight of the steel slag being 100%, the average iron content of the steel slag is 60% to 85%. Iron slag referred to in the present invention refers to the slag produced by raking slag after the ironmaking process, and based on the total weight of iron slag being 100%, the average iron content of iron slag is 60% to 85%.

The slag referred to in the present invention refers to the slag produced in the process of smelting steel slag and/or iron slag in an electric furnace, and its main components include calcium oxide (CaO), silicon dioxide (SiO ₂ ), iron oxide (FeO), Magnesium oxide (MgO), manganese oxide (MnO) and aluminum oxide (Al ₂ O ₃ ).

In the electric furnace steelmaking method of the present invention, the steps of distributing materials are carried out in a specific order. This specific order is to add steel scrap first, and then add steel slag and/or iron slag to embed steel slag/iron slag in the steel scrap, so as to provide the slag with the calcium oxide contained in the steel slag and iron slag in a specific total usage. The basicity (for example: 2.0 to 3.0, which is conducive to the generation of basic slag), helps to melt steel slag and slag iron in advance. In addition, the increased basicity will reduce the saturation concentration of MgO (that is, increase the content of second-phase solid particles), so as to increase the viscosity of slag, and then generate foamed slag, so dephosphorization can be performed at low temperature and foam can be generated earlier slag, thereby saving electricity. Therefore, the electric furnace steelmaking method of the present invention can improve the foaming effect of the slag while reducing the content of auxiliary raw materials such as MgO and CaO, thereby improving the dephosphorization effect of the slag.

Please refer to FIG. 1 , which is a flowchart illustrating an electric furnace steelmaking method according to an embodiment of the present invention. The method 100 for electric furnace steelmaking includes a step 110 of distributing materials. In the distributing step 110, oxygen and natural gas are introduced into the electric furnace, wherein the volume ratio of oxygen to natural gas is 1.5 to 2.5, and preferably 2.0.

When the volume ratio of oxygen to natural gas is less than 1.5, too low oxygen content is not conducive to the melting of raw materials. When the volume ratio of oxygen to natural gas is greater than 2.5, too high oxygen content is easy to rapidly increase the temperature of molten steel and slag, and reduce the dephosphorization effect.

In some embodiments, oxygen and natural gas can be fed into the electric furnace through the furnace wall oxygen lance, and the furnace wall oxygen lance adopts a low-oxygen combustion mode at this time. In some embodiments, natural gas may comprise methane or combinations thereof.

In some embodiments, raw materials for electric furnace steelmaking may include steel scrap, steel slag, iron slag, molten iron, and iron-containing raw materials of direct-reduced iron (DRI). In some specific examples, steel slag and iron slag can be used alone or in combination. Hereinafter, "steel slag/iron slag" refers to the raw materials used alone or in combination.

The composition of steel slag/iron slag includes iron phase and slag phase. Compared with other raw materials, the content of CaO in the composition of steel slag/iron slag is higher (that is, the basicity is 3.0 to 5.0), so as to provide calcium oxide to the slag, thus increasing its basicity, thereby improving the dephosphorization effect and save power.

The electric furnace steelmaking method 100 of the present invention utilizes the CaO in the slag phase of steel slag/iron slag to increase the viscosity of molten steel, and through the order of the material distributing steps (i.e. adding scrap steel first, then adding steel slag/iron slag) to In the initial stage of steelmaking, increase the basicity of slag to equal to or greater than 2 (that is, produce basic slag), so that dephosphorization can be carried out earlier, and the saturation concentration of MgO can be reduced by the increased basicity (that is, increase the second phase content of solid particles) to increase the viscosity of the slag, thereby producing foamed slag. Therefore, the electric furnace steelmaking method 100 of the present invention can increase the foaming effect of slag while reducing the content of secondary raw materials such as MgO and CaO, thereby improving the dephosphorization effect of slag.

In some embodiments, the composition of steel slag/slag iron includes calcium oxide and silicon dioxide, and the basicity of steel slag/slag iron is 3.0 to 5.0. When the composition of steel slag/iron slag includes calcium oxide and silicon dioxide, and the basicity of steel slag/iron slag is 3.0 to 5.0, steel slag can increase the basicity of slag, improve its dephosphorization effect and save electricity. Preferably, the basicity of steel slag/iron slag can be 3.5 to 4.5.

Based on the total weight of steel scrap, steel slag, iron slag and molten iron being 100% by weight, the total usage of steel slag and iron slag is 5% by weight to 15% by weight. Preferably, the total usage amount of steel slag and iron slag is 7% by weight to 10% by weight. When the total amount of steel slag and iron slag used is less than 5% by weight or greater than 15% by weight, the steel slag and iron slag cannot increase the basicity of the slag to 2.0 to 3.0 at the initial stage of steelmaking (about 30 minutes from steelmaking) within, reducing its dephosphorization effect and wasting electric energy.

In some embodiments, based on the total weight of steel scrap, steel slag, iron slag and molten iron being 100% by weight, the amount of steel scrap used is 30% by weight to 90% by weight. When the amount of steel scrap used is within the aforementioned range, the molten steel produced by the electric furnace steelmaking method has sufficient iron content and purity.

The distributing step 110 includes providing steel scrap (shown in operation 111 ), providing steel slag and/or iron slag on the steel scrap (shown in operation 113 ), and providing molten iron into the electric furnace (shown in operation 115 ). When the order of adding steel scrap and steel slag/iron slag is not in the aforementioned order (that is, adding steel slag/iron slag first, then adding steel scrap), it is no different from the existing electric furnace steelmaking technology, and cannot effectively dephosphorize.

In some embodiments, while feeding oxygen and natural gas, the aforementioned raw materials are added at the same time. After steel scrap is added, steel slag/iron slag is added, and then molten iron is added to the electric furnace. In some specific examples, the temperature of the molten iron is 1350° C. to 1450° C., and the feeding rate of the molten iron is 2 tons/minute to 5 tons/minute. When the temperature and feeding speed of the molten iron are in the aforementioned range, the molten iron can be used as a heat source to facilitate the melting of other raw materials.

Please refer to FIG. 1 again, after the distributing step 110, a slagging step 130 is performed. In the slagging step 130, the volume ratio of oxygen to natural gas is increased to be greater than 2.5 and less than or equal to 10.

When the volume ratio of oxygen to natural gas is not greater than 2.5, too low oxygen content is not conducive to the melting of raw materials. When the volume ratio of oxygen to natural gas is greater than 10, too high oxygen content is easy to rapidly increase the temperature of molten steel and slag, and reduce the dephosphorization effect.

The slagging step 130 includes adding additives into the electric furnace (as shown in operation 131 ) and blowing carbon powder into the electric furnace (as shown in operation 133 ). The aforementioned additives and carbon powder can oxidize and reduce the impurities produced in the steelmaking process into electric furnace slag, thereby improving the cleanliness of molten steel.

In some embodiments, after all the molten iron is added to the electric furnace, power is applied to the electrode rod of the electric furnace, and the oxygen lance is changed from the low-oxygen combustion mode to the high-oxygen combustion mode, that is, the volume ratio of oxygen to natural gas is adjusted to be greater than 2.5 and equal to or less than 10 for decarburization. In some other embodiments, before the molten iron is fed into the electric furnace, the electricity is turned on and the volume ratio of oxygen to natural gas is adjusted to perform the aforementioned decarburization. Decarburization is a high-oxygen environment that removes carbon and other impurities in the molten raw material by burning to generate higher-purity molten steel.

In some embodiments, additives may include, but are not limited to, lime, magnesia, cement, marble, serpentine, dolomite, feldspar, mica, and/or talc. In some embodiments, the lime contains 95 weight percent CaO (100 weight percent based on the total weight of the lime). In other embodiments, the dolomite contains 60% by weight of CaO and 38% by weight of MgO (100% by weight based on the total weight of the dolomite).

The source of the electric furnace slag can come from the oxides produced by the components and additives of at least one of steel scrap, steel slag and iron slag. The composition of slag includes basic oxides, acidic oxides and amphoteric oxides. Specific examples of basic oxides include, but are not limited to, calcium oxide (CaO), ferrous oxide (FeO), magnesium oxide (MgO), and manganese oxide (MnO). Specific examples of basic oxides include, but are not limited to, silicon dioxide (SiO ₂ ), phosphorus pentoxide (P ₂ O ₅ ), and ferric oxide (Fe ₂ O ₃ ). Specific examples of amphoteric oxides may include, but are not limited to, alumina (Al ₂ O ₃ ).

In the slagging step 130 , steel slag/iron slag with a high basicity (for example: 3.0 to 5.0) and slag with a low basicity (for example: 2.0 to 3.0) can contact in advance to produce chemical diffusion. For example, iron oxide in electric furnace slag diffuses to the surface of steel slag/iron slag, or calcium oxide in steel slag/iron slag diffuses into electric furnace slag, which can lower the melting point of steel slag/iron slag, thus saving the cost of electric furnace electrical energy.

In some embodiments, the basicity of the slag is 2.0 to 3.0. When the basicity of the slag is within the aforementioned range, the iron oxide in the slag can diffuse to the surface of the steel slag/iron slag, thereby lowering the melting point of the steel slag/iron slag, thus saving the electric energy of the electric furnace. In addition, the slag has a good dephosphorization effect, which can prevent the rephosphorization of molten steel, and the slag has good fluidity, so it is easy to become foamed slag.

In the traditional distributing step, steel slag/iron slag is added first, and then steel scrap is added, so molten steel scrap will block the contact between steel slag/iron slag and slag, and hinder the chemical reaction between the aforementioned steel slag/iron slag and electric furnace slag diffusion.

In some embodiments, the phases of the slag may include a solid phase and a liquid phase. Specific examples of the aforementioned solid phase may include but not limited to supersaturated solid phase particles of CaO, C ₂ S, MgO or Ca ₂ SiO ₄ . Specific examples of the liquid phase may include but not limited to supersaturated solutions of CaO, C ₂ S, FeO, MgO, and Al ₂ O ₃ .

In some embodiments, the electric furnace steelmaking method 100 of the present invention can use solid particles to increase the viscosity of the slag to promote the foaming of the slag. The foamed slag can improve the smelting efficiency of the electric furnace steelmaking method 100 . In other words, foamed slag can promote the reaction of steel slag, remove impurities (such as dephosphorization) and improve cleanliness, and can cover the arc generated by the electrode rod to improve the heating efficiency of molten steel and reduce the impact of molten steel on the furnace. The heat radiation of the body, the air is isolated to prevent nitrogen from entering the electric furnace, so it has both energy saving and low nitrogen benefits.

In some embodiments, the viscosity of the slag may be 150 cP to 500 cP, and preferably 250 cP to 400 cP. When the viscosity of the slag is in the aforementioned range, the slag has good foaming, so the dephosphorization effect can be improved and electric energy can be saved.

In some embodiments, the viscosity of the slag can be adjusted by the solid fraction of the slag. In some specific examples, based on the total phase ratio of the slag being 100%, the solid phase ratio of the slag is 5% to 10%. When the solid phase rate of the slag is within the aforementioned range, the slag can be controlled to be outside the liquid phase area of the slag liquid phase saturation line diagram and within the slagging target area to produce supersaturated solid phase particles, thereby increasing the slag viscosity, and Foams the slag.

In some embodiments, the dephosphorization temperature of the slag is 1450°C to 1560°C, and preferably 1450°C to 1500°C. When the dephosphorization temperature is within the aforementioned range, the slag can remove the phosphorus in the molten steel, and rephosphorization will not occur, so the dephosphorization effect of the electric furnace steelmaking method can be improved.

When the electric furnace melts down (that is, the scrap steel and steel slag/slag iron of the electric furnace are in a molten state), the molten steel is taken out to measure its temperature, carbon concentration, and the amount of phosphorus in the steel to determine whether it meets the steelmaking termination conditions. If so, the steelmaking is terminated, and the molten steel is taken out to remove the slag for subsequent casting.

In some embodiments, the temperature at which steelmaking is terminated is 1300°C to 1700°C. When the temperature at which steelmaking is terminated falls within the aforementioned range, the resulting molten steel can facilitate subsequent casting.

The electric furnace steelmaking method 100 can perform dephosphorization. Based on the weight of the molten steel being 100% by weight, the amount of tapping phosphorus in the molten steel is not greater than 0.03% by weight, and preferably not greater than 0.02% by weight. In some embodiments, the dephosphorization rate of molten steel is not less than 89%, and preferably greater than 90%. When the amount of tapping phosphorus in the molten steel is greater than 0.03% by weight, or the dephosphorization rate of the molten steel is less than 89%, the plasticity and toughness of the steel product made become poor.

The following examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention. Anyone skilled in this art can make various changes and modifications without departing from the spirit and scope of the present invention.

Preparation of molten steel

The molten steel in Example 1 is sequentially added 30 to 90 weight percent steel scrap and 5 to 15 weight percent steel slag/iron slag into the electric furnace. The composition of steel slag and iron slag mainly includes iron, iron oxide, calcium oxide and silicon dioxide, and the basicity of steel slag and iron slag is 3.2 to 4.8. Feed oxygen and methane with a volume ratio of 2.0 into the electric furnace, and add 5% by weight to 95% by weight of molten iron at a temperature of 1350°C to 1450°C into the electric furnace at a rate of 2 to 5 tons per minute. After all the molten iron is added, power is applied to the electrode rod, and the volume ratio of oxygen to methane is adjusted to be 3 to 10 to carry out the combustion oxidation decarburization step. Next, add 3 to 8 weight percent of lime and 2 to 5 weight percent of other additives (including dolomite and magnesium oxide, but not lime) into the electric furnace, and blow carbon powder to perform the slagging step. The solid fraction of the slag is 5% to 10% by weight, the basicity of the slag is 1.8 to 2.8, and the viscosity of the slag is 150 to 500cP. The dephosphorization temperature of the slag is 1450°C to 1530°C. After the raw materials are smelted (that is, the scrap steel and steel slag/slag iron of the electric furnace are in a molten state), start timing, and when the smelting temperature reaches 1600°C to 1620°C, stop steelmaking to obtain the molten steel of Example 1, and take it out The molten steel and its slag were tested in the following evaluation methods, and the aforementioned detailed conditions and test results are shown in Table 1 and Figures 2 to 4 below.

comparative example

Comparative Example Prepare molten steel in the same manner as in Example 1. The difference is that the comparative example changes the fabric process, the amount and type of raw materials and additives used, and the detailed conditions and test results are shown in Table 1 and Figures 5 to 7 below.

Evaluation method

1. Test of phosphorus content in tapping

The test of the amount of phosphorus in the steel was carried out by using an X-ray fluorescence spectrometer (XRF) to detect the phosphorus content of the molten steel in the examples and comparative examples, and its parameters and reagents were commonly used by those with ordinary knowledge. Based on the weight of the molten steel in the embodiment and the comparative example being 100% by weight, the amount of tapping phosphorus in the embodiment and the comparative example is calculated correspondingly.

2. Dephosphorization rate test

The test of dephosphorization rate is to detect the phosphorus content of the molten iron and molten steel of embodiment and comparative example with X-ray fluorescence analyzer, detection parameter and reagent are what have common knowledge person's customary, and according to following formula (I) Obtain the dephosphorization rate of embodiment and comparative example, to evaluate its dephosphorization effect, wherein the calculation of dephosphorization rate is shown in the following formula (I):

3. Test of average power consumption

The test of the average power consumption is based on the electricity consumed by the electric furnace steelmaking method of the embodiment and the comparative example (in kwh) correspondingly divided by the weight of the steel slag/iron slag used in the embodiment and the comparative example (in tons) ), to obtain the average power consumption of the embodiment and the comparative example, and the unit of the average power consumption is kilowatt-hour/ton, so as to evaluate the power saving effect of the embodiment and the comparative example accordingly.

Table 1 Example comparative example electric furnace steelmaking method cloth step Cloth method A B Amount of steel scrap used (percentage by weight) 30~90 5~95 Total usage of steel slag and iron slag (weight percentage) 5~15 2~7 Slagging step Lime usage (weight percent) 3~8 3~10 Usage amount of other additives (percentage by weight) 2~5 2~6 Salinity of steel slag and iron slag 3.2~4.8 3.2~4.8 Evaluation method Tapping phosphorus content (weight percent) 0.0120 0.0145 Dephosphorization rate (%) 90.77 88.85 Average power consumption (kWh/ton) 166.0 177.3 Note: In the distributing step, "A" means adding steel slag/iron slag first and then steel scrap to embed steel slag/iron slag in the steel scrap, and "B" means adding steel slag first and then adding steel slag/iron slag.

Please refer to Table 1, according to the results of tapping phosphorus amount and dephosphorization rate, compared with Comparative Example, the molten steel produced by the electric furnace steelmaking method of the embodiment has a lower tapping phosphorus amount and higher dephosphorization rate rate, so the order of distribution of materials used in the electric furnace steelmaking method of the embodiment can improve the dephosphorization effect. In other words, adding steel slag/iron slag first and then adding scrap steel, and burying steel slag/iron slag in scrap steel can improve the dephosphorization effect.

In addition, according to the result of the average power consumption, compared with the comparative example, the electric furnace steelmaking method of the embodiment has a better power saving effect, so the order of the material distribution used in the electric furnace steelmaking method of the embodiment can save the electric energy consumption of the electric furnace . Accordingly, the sequence of material distribution used in the electric furnace steelmaking method of the embodiment can enable chemical diffusion between the steel slag/iron slag and the slag to lower the melting point of the steel slag/iron slag so that dephosphorization can be performed at low temperature. In addition, this distribution sequence can increase the viscosity of slag to produce foamed slag, thereby improving the dephosphorization effect.

Please refer to FIGS. 2 and 5 , which are diagrams showing the change of slag basicity with smelting time according to the electric furnace steelmaking method of Example 1 and Comparative Example of the present invention. The basicity of the slag in Example 1 can reach 2.0 in about 30 minutes, while the basicity of the slag in Comparative Example can only reach 2.0 after 40 minutes. Therefore, the distribution order of the electric furnace steelmaking method in Example 1 and the total amount of steel slag/iron slag used can facilitate chemical diffusion between the steel slag/iron slag and the slag, so that the basicity of the slag reaches a suitable dephosphorization level sooner. Range (i.e. 2.0 to 3.0).

Please refer to FIGS. 3 and 6 , which are diagrams showing the variation of slag composition with smelting time in the electric furnace steelmaking method according to Embodiment 1 and Comparative Example of the present invention, respectively. From the composition of calcium oxide and silicon dioxide, it can be seen that compared with the slag of Comparative Example, the calcium oxide content of the slag of Example 1 is higher, and the silicon dioxide content of the two is equivalent, so the slag of Example 1 The salinity can reach the range suitable for dephosphorization in the early stage of smelting, so as to improve the dephosphorization effect.

Please refer to FIGS. 4 and 7 , which are diagrams showing the slag liquid saturation line diagrams of the electric furnace steelmaking method according to Embodiment 1 and Comparative Example of the present invention, respectively. The numbering sequence of the points marked in Figures 4 and 7 is counted according to the smelting time in Figures 2 and 5 respectively. In these two figures, the liquid phase area is marked by a solid line, and the slagging target area is marked by a dotted line, so the area where foamed slag is generated is outside the liquid phase area and within the slagging target area. The 7 points in Fig. 4 are all in the region where foamed slag is produced, and the 6 points in Fig. 7 are in the region where foamed slag is produced, but 2 points are in the liquid phase region, so the electric furnace steelmaking of embodiment 1 The distributing sequence of the method can make the whole smelting process be carried out under the foamed slag, thereby improving the dephosphorization effect.

In summary, the method for electric furnace steelmaking of the present invention is to carry out the distributing step (sequence of providing steel scrap, steel slag/slag iron and molten iron in sequence) and use a specific total usage amount (5% by weight to 15% by weight) in a specific order. percentage) of steel slag and iron slag to produce basic slag to help melt steel slag and iron slag, and foam the slag in advance to dephosphorize at low temperature, so it can save electric energy and improve the dephosphorization effect.

Although the present invention has been disclosed above in terms of implementation, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field of the present invention can make various modifications and changes without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

100: method 110,130: steps 111, 113, 115, 131, 133: Operation

In order to have a more complete understanding of the embodiments of the present invention and their advantages, please refer to the following descriptions together with the corresponding drawings. It must be emphasized that the various features are not drawn to scale and are for illustration purposes only. The contents of relevant diagrams are explained as follows: FIG. 1 is a flowchart illustrating an electric furnace steelmaking method according to an embodiment of the present invention. FIG. 2 is a diagram showing the variation of slag basicity with smelting time in the electric furnace steelmaking method according to an embodiment of the present invention. Fig. 3 is a graph showing the variation of slag composition with smelting time in the electric furnace steelmaking method according to an embodiment of the present invention. FIG. 4 is a diagram showing a slag liquid saturation line diagram of an electric furnace steelmaking method according to an embodiment of the present invention. Fig. 5 is a graph showing the variation of slag basicity with smelting time in the electric furnace steelmaking method according to a comparative example of the present invention. Fig. 6 is a diagram showing the variation of slag composition with smelting time in the electric furnace steelmaking method according to a comparative example of the present invention. FIG. 7 is a diagram showing a slag liquid saturation line diagram of an electric furnace steelmaking method according to a comparative example of the present invention.

100: method

110,130: steps

111, 113, 115, 131, 133: Operation

Claims (10)

A method for electric furnace steelmaking, comprising: Carrying out a distributing step, wherein the distributing step passes oxygen and natural gas into the electric furnace, a volume ratio of the oxygen to the natural gas is 1.5 to 2.5, and the distributing step includes: Provide a scrap steel; providing a steel slag and/or a ferrous slag on the scrap; and Providing a molten iron into the electric furnace, wherein based on the total weight of the steel scrap, the steel slag, the iron slag and the molten iron being 100% by weight, the total usage of the steel slag and the iron slag is 5% by weight to 15% by weight % by weight; and Carrying out a slagging step, wherein the slagging step increases the volume ratio to be greater than 2.5 and less than or equal to 10, and the slagging step comprises: adding an additive to the electric furnace; and Blowing carbon powder into the electric furnace to obtain a slag and a molten steel; Wherein based on the weight of the molten steel being 100% by weight, the amount of phosphorus in a tapping of the molten steel is no more than 0.03% by weight. The method for electric furnace steelmaking as described in Claim 1, wherein based on the total weight of the steel scrap, the steel slag, the iron slag and the molten iron as 100% by weight, the usage amount of the steel scrap is 30% by weight to 90% by weight percentage. The method for electric furnace steelmaking according to claim 1, wherein a composition of the steel slag includes calcium oxide and silicon dioxide, and a basicity of the steel slag is 3.0 to 5.0. The method for electric furnace steelmaking according to claim 1, wherein a composition of the iron slag includes calcium oxide and silicon dioxide, and a basicity of the iron slag is 3.0 to 5.0. The method for electric furnace steelmaking according to claim 1, wherein based on the total phase ratio of the slag being 100%, the solid phase ratio of the slag is 5% to 10%. The method for electric furnace steelmaking according to claim 1, wherein the basicity of the slag is 2.0 to 3.0. The method for electric furnace steelmaking as claimed in Claim 1, wherein a dephosphorization temperature of the slag is 1450°C to 1560°C. The method for electric furnace steelmaking according to claim 1, wherein based on the total weight being 100 wt%, the additive is used in an amount of 5 wt% to 13 wt%. The method for electric furnace steelmaking according to claim 1, wherein the additives include lime, magnesia, cement, marble, serpentine, dolomite, feldspar, mica and/or talc. The method for electric furnace steelmaking as described in Claim 1, wherein after the molten iron is provided, the method for electric furnace steelmaking further includes a power transmission step.

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