TWI721844B - Composition for slagging - Google Patents

Abstract

A composition for slag making, comprising 15 wt% to 35 wt% FeO, 35 wt% to 45 wt% CaO, and 10 wt% to 20 wt%, based on the total amount of the slag making composition being 100 wt% % SiO ₂ , and 10 wt% to 20 wt% Al ₂ O ₃ . The composition for slag making is used in the electric arc furnace steelmaking process to remove impurities (such as phosphorus) from the molten steel and obtain slag. The viscosity of the formed slag is not easily affected by temperature and changes. Furthermore, the slag It has a wide foaming temperature. In addition, the foamed slag formed by the slag has a long foaming life.

Description

Composition for slagging

The present invention relates to a composition used in a steelmaking process, in particular to a composition used in a steelmaking process and used to form slag.

The oxidation period of electric arc furnace steelmaking sequentially includes the following treatments: melting of steel scrap, dephosphorizing the molten steel, and foaming the slag. The process of foaming the slag is to foam the slag obtained in the dephosphorization stage to form foamed slag. The foamed slag can embed the electric arc generated by the electric arc furnace, so that the lining and the electrode of the electric arc furnace are reduced by arc radiation and the service life of the lining and the electrode of the electric arc furnace is improved. In addition, the foamed slag can absorb the heat radiation of the electric arc and facilitate the heating of the molten steel, thereby improving the steelmaking efficiency and simultaneously achieving the effect of saving electric energy. Therefore, the foaming ability of slag will directly affect the cost of electric arc furnace steelmaking.

Wu Weide et al. published in 2018 "Study on the effect of different FeO ratios on the high-temperature characteristics of FeO-CaO-SiO ₂ -Al ₂ O ₃ -MgO slag system", which disclosed a FeO-CaO-SiO ₂ -Al ₂ O ₃ -MgO The slag system contains 10 wt% to 40 wt% FeO, 37.5 wt% to 57.1 wt% CaO, 12.5 wt% to 22.9 wt% SiO ₂ , 5 wt% Al ₂ O ₃ , and 5 wt% MgO. The slag system can increase the foaming performance of the slag by _{adjusting the ratio of CaO/SiO 2 and the content of FeO.}

Therefore, the object of the present invention is to provide a slag-making composition used in the electric arc furnace steelmaking process and used to form slag with better foaming properties.

Therefore, the composition for slag making of the present invention includes 15 wt% to 35 wt% FeO, 35 wt% to 45 wt% CaO, and 10 wt% to 10 wt% based on 100 wt% of the total amount of the slag making composition. 20 wt% SiO ₂ and 10 wt% to 20 wt% Al ₂ O ₃ .

The effect of the present invention is that the slag-making composition is applied to the electric arc furnace steelmaking process to separate impurities (such as phosphorus) from the molten steel scrap and obtain slag. The slag-making composition is combined with various components and contents. In particular _{, the content of Al 2} O ₃ ranges from 10 wt% to 20 wt%, so that the viscosity of the slag is not easily affected by temperature. The slag has a wide foaming temperature, and the foamed slag formed by the slag has Long foam life.

The composition for slag making of the present invention includes 15 wt% to 35 wt% FeO, 35 wt% to 45 wt% CaO, and 10 wt% to 20 wt% based on the total amount of the slag making composition. % SiO ₂ , and 10 wt% to 20 wt% Al ₂ O ₃ .

In order to match the operating environment of the electric arc furnace steelmaking as an oxidizing atmosphere, the FeO content in the composition for slagging is not less than 15wt%. In addition, the FeO content is 15 wt% or more, which helps to remove impurities (such as phosphorus) from the molten steel scrap. The FeO content is 35 wt% or less, which can prevent the viscosity of the slag formed from the slagging composition from being too low to be conducive to foaming.

In the composition for slagging, the _{content ratio of CaO to SiO 2} (CaO/SiO ₂ , that is, basicity) ranges from 1.75 to 4.5. The basicity of the slagging composition is 1.75 or more, which helps to remove impurities (such as phosphorus) from the molten steel scrap, and can prevent the viscosity of the slag formed by the slagging composition from being too low, which is not conducive to development. bubble. The alkalinity of the slagging composition is 4.5 or less, which can prevent the slag formed from the slagging composition from becoming too high in viscosity and preventing impurities (for example, phosphorus) from being detached from the molten steel.

The content range of the Al ₂ O ₃ is 10 wt% or more. The viscosity of the slag formed by the slagging composition is not easily affected by temperature. Furthermore, the slag has a wide foaming temperature and is formed by the slag. The foamed slag formed has a long foam life. And taking the cost of the slagging composition as a consideration, _{the content of Al 2} O ₃ in the slagging composition is controlled to be 20 wt% or less. In order to make the foamed slag formed after foaming the slag have a longer foam life, preferably, the _{content of the Al 2} O ₃ of the slagging composition ranges from 15 wt% to 20 wt %.

In order to cope with the generation of MgO and MnO from the oxidation of scrap steel in the electric arc furnace steelmaking process, the slagging composition may optionally further contain MnO and MgO. For example, but not limited to, in terms of the content of MnO and MgO in the slag formed in the electric arc furnace steelmaking process, the composition for slagging includes more than 0 wt% to less than 6 wt% of MnO, and more than 0 wt% to 6 wt% % Less than MgO.

The preparation method of the composition for slagging is, for example, _{uniformly mixing FeO, CaO, SiO 2} , Al ₂ O ₃ , and optionally added MnO and MgO.

The method of using the composition for slagging is to mix the composition for slagging with melted steel scrap to form a mixture, and subject the mixture to a smelting process to form a product containing slag and molten steel separated from the slag. The smelting process is performed in a furnace. The smelting process is, for example, oxidation roughing, and the melting furnace is, for example, an electric arc furnace. The smelting process is performed at a temperature of, for example, 1530° C. to 1620° C., gas is introduced into the mixture to produce foamed slag formed from the slag. The gas is, for example, oxygen, nitrogen, or air. Further, the foamed slag is obtained and solidified slag is formed through cooling treatment, such as water quenching.

The present invention will be further illustrated with the following examples, but it should be understood that the examples are only for illustrative purposes and should not be construed as limitations to the implementation of the present invention.

Example 1

Combine 18.7 wt% FeO (purity 99%), 41.5 wt% CaO (purity 99%), 16.8 wt% SiO ₂ (purity 99%), and 11.9 wt% Al ₂ O ₃ (purity 99%). %), 5.4 wt% of MnO (purity of 99%), and 5.7 wt% of MgO (purity of 99%) were uniformly mixed to obtain a composition for slagging. The composition for slagging was heated and melted in a frequency induction furnace, and then cooled and solidified to obtain a sample of the composition for slagging. An X-ray fluorescence spectrometer (manufacturer Rigaku Corporation, model Supermini 200) was used to analyze the components of the sample to confirm the component ratio of the composition for slagging.

Put 35 grams of the slag-making composition into a pure molybdenum crucible, and use the cycle induction furnace to heat the slag-making composition to 1550°C at a frequency of 45 kHz and a power of 20 kW. The composition for slagging is melted to obtain the composition for slagging in a molten state. Then, a carbon source material (purity of 90% to 95%) is added to the molten slag-making composition for a foaming process to cause a chemical reaction between the two and generate carbon monoxide gas to form foamed slag. Afterwards, the foamed slag is subjected to water quenching treatment to form solidified slag.

Examples 2 to 3 and Comparative Examples 1 to 2

Examples 2 to 3 and Comparative Examples 1 to 2 were prepared with a similar preparation process as Example 1 to produce slagging composition, foamed slag, and solidified slag. The difference is that Examples 2 to 3 and Comparative Example were changed as shown in Table 1. The amount of each component in the slagging composition of 1 to 2.

[Evaluation item]

1. Viscosity measurement

The slag-making composition of Examples 1 to 4 and Comparative Examples 1 to 6 was heated under the conditions of starting temperature at room temperature (25°C), ending temperature at 1600°C, and heating rate at 2°C/min, and Using a viscosity measuring instrument (manufacturer Brookfield, model LVDV-III RV) to analyze the viscosity of the slagging composition of Examples 1 to 4 and Comparative Examples 1 to 6 at 1400°C to 1580°C (the rotating speed of the viscosity measuring instrument) Set to 20 rpm).

2. Bubble life

The "slag foaming measuring device" described in the first embodiment of Patent Document TW I667473 was used to measure the height of the slagging composition of Examples 1 to 3 and Comparative Examples 1 to 2 after heating and melting, and record as The initial height. Then, the molten slagging composition is foamed at 1550°C to form foamed slag, and at the same time, the height change and duration of the foamed slag are recorded, and the recording time is stopped when the height of the foamed slag drops back to the initial height , This time interval is the foam life of the foamed slag formed by the slagging composition.

Table 1 Example Comparative example 1 2 3 1 2 Composition for slagging (wt%) CaO/SiO ₂ 2.5 2.5 2.5 2.5 2.7 CaO 41.5 40.9 42.4 46.2 48.3 SiO ₂ 16.8 16.6 17.0 18.7 18.2 FeO 18.7 15.2 11.4 17.8 15.7 Al ₂ O ₃ 11.9 15.7 18.3 6.5 6.4 MgO 5.7 6.0 5.3 4.8 5.0 MnO 5.4 5.6 5.6 6.0 6.4 Slag viscosity (cP) 1400°C 130 127 193 No measurement No measurement 1480°C 58 77 54 Greater than 1200 Greater than 2000 1530°C 36 64 48 79 1047 1550°C 36 58 47 60 645 1580°C 35 52 45 56 137 Foam life (minutes) 1550°C 6.3 10.0 10.3 4.8 6.1

In the electric arc furnace steelmaking process, the viscosity of the slag will affect the foaming performance of the slag. The existing literature proposes that the slag foaming temperature in the general electric arc furnace steelmaking process is 1530°C to 1620°C. The viscosity of the slag The range of 200 cP to 800 cP is more conducive to the foaming of the slag. If the viscosity of the slag is greater than 1000 cP, the slag will be too viscous and have poor fluidity which is not conducive to the foaming of the slag. Therefore, the viscosity of the slag must be 1000 cP. Below, and when the viscosity of the slag is below 1000 cP, the wider the temperature range, the better. In addition, the viscosity of slag is affected by temperature as low as possible. Based on this, it can be seen from the slag viscosity in Table 1 that the slag-making composition of Examples 1 to 3 penetrates the blending of the content of each component, especially the content of Al ₂ O ₃ in the range of 10 wt% to 20 wt%, so that the formed The viscosity of the slag in the temperature range of 1400°C to 1580°C is below 1000 cP, which is beneficial to the slag foaming, and the viscosity of the slag in the temperature range of 1400°C to 1580°C is affected by the temperature and the range of change is small. It is shown that the slags of Examples 1 to 4 are suitable for foaming in a wide temperature range.

However, in Comparative Example 1, because _{the content of Al 2} O ₃ in the slag-making composition is less than 10 wt% and the content of CaO is greater than 45 wt%, the viscosity of the formed slag at 1480°C to 1530°C is affected by temperature. The magnitude of the change is enormous.

_{Comparative Example 2 Because the content of Al 2} O ₃ in the composition for slagging is less than 10 wt% and the content of CaO is greater than 45 wt%, the viscosity of the formed slag between 1480°C and 1580°C is affected by temperature. The range is extremely large, and the viscosity of the slag at 1530°C is greater than 1000 cP, which is not conducive to foaming, indicating that the slag of Comparative Example 2 has a narrow temperature range suitable for foaming.

From the foam life of the foamed slag in Table 1, it can be seen that the composition for slagging of Examples 1 to 4 can be used for slagging through the blending of the content of each component, especially the content of Al ₂ O ₃ in the range of 10 wt% to 20 wt%. The slag formed by the composition has a lower viscosity, which makes the foam life of the foamed slag longer, especially the foamed slag of Examples 2 and 3 has a longer foam life.

The slagging composition of Comparative Examples 1 and 2 is a formula commonly used in the prior art, which is to increase the solidified phase particles of the slag to increase the viscosity of the slag by increasing the CaO content in the slagging composition to be greater than 45% by weight. In turn, the foam life of the foamed slag is improved. However, from the foam life of the foamed slag in Table 1, it can be seen that in Comparative Example 1 _{, the range of Al 2} O ₃ content in the slagging composition is less than 10 wt% and the CaO content is greater than 45 wt%, resulting in a longer foam life of the formed foamed slag. short. In Comparative Example 2, because _{the content range of Al 2} O ₃ in the composition for slagging is less than 10 wt% and the content of CaO is greater than 45 wt%, the foam life of the formed foamed slag is short.

In summary, the composition for slagging of the present invention can be combined with each component and content, especially the content of Al ₂ O _{3 is} in the range of 10 wt% to 20 wt%, so that the slag formed by the composition for slagging is The viscosity is not easily affected by temperature, the slag has a wide foaming temperature, and the foamed slag formed by the slag has a long foam life, so it can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to Within the scope covered by the patent of the present invention.

no.

Claims (3)

One kind of a slag composition, comprising: a total amount of slag in the composition is 100wt% basis, 15wt% to 35wt% of the of FeO; 35wt% to 45wt% of CaO; 10wt% to 20wt% of SiO _2; and 15wt% to 20wt% Al ₂ O ₃ . The composition for slagging according to claim 1, further comprising more than 0 wt% to 6 wt% or less of MnO. The composition for slagging according to claim 1, further comprising more than 0 wt% to 6 wt% or less of MgO.