CN115029607B - Medium-carbon quasi-bainitic steel and method for preparing same by utilizing iron-rich nonferrous metallurgical slag - Google Patents
Medium-carbon quasi-bainitic steel and method for preparing same by utilizing iron-rich nonferrous metallurgical slag Download PDFInfo
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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Abstract
The invention discloses a medium carbon quasi-bainitic steel and a method for preparing the same by utilizing iron-rich nonferrous metallurgical slag. The method for preparing the medium carbon quasi-bainitic steel by using the iron-rich nonferrous metallurgical slag comprises the following steps: taking iron-rich nonferrous metallurgical slag as a raw material, and carrying out reduction smelting to obtain molten iron; adding alloy auxiliary materials into molten iron according to the molten iron components, and degassing and slagging to obtain molten steel; and adopting a continuous casting method casting blank, and preparing the medium-carbon quasi-bainitic steel through a controlled rolling and cooling process. According to the invention, the nonferrous metallurgical slag solid waste is utilized and linked with the steel industry, so that a process route from the nonferrous metallurgical slag to the medium-carbon quasi-bainitic steel product is formed, the utilization rate of the metallurgical slag is practically improved, and the recycling and harmless bulk treatment of the metallurgical slag are promoted; the value of alloy elements in the metallurgical slag is fully exerted, the variety of raw materials for steel production is enriched, the production cost is reduced, and the added value of the product is improved; has the advantages of energy conservation, environmental protection and green production.
Description
Technical Field
The invention relates to the technical field of metallurgical slag treatment, in particular to medium-carbon quasi-bainitic steel and a method for preparing the same by utilizing iron-rich nonferrous metallurgical slag.
Background
The iron and steel production in China mainly takes a long process, most of steel is refined from iron ores, but at present, lean iron ores are rich and rich, the exploitation requirement is high, the technical difficulty is high, the average exploitation taste is only 10% -30%, and the economical efficiency is poor, so that the iron ores have high external dependency, the non-regenerability of the iron ores is achieved, and the search for the replacement resources of the iron ores is a necessary path for promoting the healthy development of the iron and steel industry.
The nonferrous metallurgical slag is slag generated in the smelting process of nonferrous metal minerals, the current nonferrous metallurgical industry has huge scale, and the metallurgical slag has large annual production and various types and mainly comprises copper slag, red mud, nickel slag, electrolytic manganese slag, lead zinc slag and the like. The discharge amount of the nonferrous metallurgical slag is different according to the taste of the ore and the production process. For example, about 2.2 tons of copper slag can be discharged per ton of copper produced, about 0.6-2.5 tons of red mud can be produced per ton of aluminum oxide produced, the mass ratio of the electric furnace nickel-iron slag to the nickel-iron alloy produced correspondingly can be about 14:1, the yield of electrolytic manganese slag is about 7-11 tons/ton of manganese, and about 0.7-0.9 tons of lead-zinc slag can be produced per ton of lead/zinc produced. A large amount of nonferrous metallurgical slag is piled up in the open for a long time, so that a large amount of land resources are consumed, and the enterprise cost is increased; on the other hand, under the effect of long-term weathering leaching, heavy metal ions and toxic elements in the slag can permeate into underground water, rivers and soil, so that the ecological environment is directly seriously damaged, and the health of surrounding people, animals and plants is endangered. The reduction, harmless and recycling of metallurgical slag is a common problem in the whole nonferrous metal industry and is a core problem puzzling the green development of the industry. Thus, the bulk utilization of nonferrous metallurgical slag is urgent.
The current way of eliminating nonferrous metallurgical slag mainly comprises the steps of extracting valuable metals and producing cement concrete building raw materials. For the production of building materials by using colored slag, a part of industries in China form a series of specifications and can realize industrial application, such as 'ferronickel slag powder used in cement and concrete' given by JC/T2503-2018, and the application and development of other metallurgical slag cementing materials are well developed. In contrast, the development of metals extracted from colored slag is insufficient. Although Chinese patent CN106086428B discloses a method for producing ferroalloy by utilizing colored slag, the ferroalloy is required to be subjected to reduction melting treatment at 1500-1700 ℃ after pelletizing, but the technology is complex and the energy consumption is high. Chinese application CN109207718A proposes a method for preparing a stainless steel raw material sinter from nickel slag, but the raw materials thereof are hematite powder, magnetite concentrate powder, nickel slag (about 20%), limestone, dolomite, return ores, coke powder, corncob particles and the like, and the problems of complex raw materials and low utilization rate of colored slag exist.
Disclosure of Invention
Based on the problems, how to provide a treatment method which is effective, can apply the iron-rich metal extracted from the nonferrous metallurgical slag to the steel production, can greatly consume the nonferrous slag, can provide raw materials for steelmaking, is beneficial to enriching the types of steelmaking raw materials and makes up the defects of self-produced iron ore, and becomes a research direction of the invention. Based on this, according to an embodiment of the present invention, an object of the present invention is to provide a method for preparing a medium carbon quasi-bainitic steel by using iron-rich nonferrous metallurgical slag, so as to solve the problems of various raw materials, complex process, high energy consumption, low utilization rate of nonferrous metallurgical slag and the like existing in the current iron-rich nonferrous metallurgical slag iron extraction and steelmaking. Another object is to provide a medium carbon quasi bainitic steel.
The above object can be achieved by the following embodiments of the present invention:
according to one aspect of the invention, the invention provides a method for preparing medium carbon quasi-bainitic steel by using iron-rich nonferrous metallurgical slag, which comprises the following steps:
taking iron-rich nonferrous metallurgical slag as a raw material, and carrying out reduction smelting to obtain molten iron;
adding alloy auxiliary materials into the molten iron according to the components of the obtained molten iron, and performing degassing and slagging to obtain molten steel with qualified components;
and casting blank of molten steel by adopting a continuous casting method, and obtaining the medium-carbon quasi-bainitic steel by adopting a controlled rolling and cooling process.
Optionally, after the step of degassing and slagging, the method further comprises: adopting external refining to adjust the molten steel components to obtain the molten steel with qualified components.
Optionally, the alloy components of the qualified molten steel comprise the following components in percentage by mass: 0.2 to 0.3 percent of C, 1.0 to 1.5 percent of Si, 1.5 to 2.0 percent of Mn, 0.2 to 0.5 percent of Mo, 0.3 to 0.8 percent of Cr, 0.04 to 0.08 percent of Nb, less than or equal to 0.003 percent of B, less than or equal to 0.003 percent of N, less than or equal to 0.005 percent of O, 0.01 percent of P and less than or equal to 0.01 percent of S.
Optionally, the step of obtaining the medium carbon quasi-bainitic steel through a controlled rolling and cooling process comprises the following steps: soaking, wherein the heat preservation time is 60-120 min, and the temperature is 1120-1200; carrying out multi-pass rolling; and (3) rapidly cooling to 400-430 ℃ after rolling, controlling the cooling speed to be 0.5-1 ℃/s, and cooling to room temperature.
Optionally, two-pass rolling is performed, and when each pass of rolling is performed, the air cooling temperature is controlled and the reduction is regulated; comprising the following steps: air-cooling to 1050-1080 ℃, and rolling for the first pass, wherein the rolling reduction is 40%; air cooling to 820-860 ℃, and rolling for the second pass, wherein the rolling reduction is 30%.
Optionally, the step of reducing smelting includes: reducing agent and flux are added, reduction smelting is carried out at 1300-1550 ℃, the temperature is kept for 60-180 min, and iron is discharged when the reduction rate of iron in slag is not less than 90% through dynamic monitoring.
Optionally, the mass ratio of the iron-rich nonferrous metallurgical slag, the reducing agent and the flux is as follows: 100:5-15: 10 to 30 percent.
Optionally, the TFe is >30% in the iron-rich nonferrous metallurgical slag.
Optionally, the method further comprises: and preparing active micro powder by adopting secondary slag synchronously. Further, the secondary slag includes: one or two of reducing slag produced by reduction smelting and steel slag produced by degassing and slagging are adopted.
Optionally, adopting direct grinding or grinding after adding active activator to obtain specific surface area>350m 2 Active micro powder/kg.
Optionally, the dosage ratio of the secondary slag to the active excitant is 100:5-30.
Optionally, the activity excitant is one or more of blast furnace slag, fly ash, quicklime, cement, clinker, byproduct gypsum, sodium silicate, sodium hydroxide, sodium sulfate, tailings, triethanolamine, propylene glycol and the like.
Optionally, the active micro powder is used as a cement mixture or a concrete admixture, and the addition amount is more than or equal to 30 percent.
According to another aspect of the invention, the medium carbon standard bainitic steel is prepared by the method for preparing the medium carbon standard bainitic steel by utilizing the iron-rich nonferrous metallurgical slag.
Optionally, the medium carbon quasi bainitic steel has a metallographic structure formed by alternately forming bainitic ferrite laths and residual austenite films.
Optionally, the medium carbon quasi-bainitic steel has a yield strength of greater than 750MPa.
Optionally, the medium carbon quasi-bainitic steel has tensile strength of more than 1200MPa, impact energy of more than 40J and elongation of more than 15%.
The beneficial effects are that: the invention links the solid waste utilization of nonferrous metallurgical slag with the steel industry, takes the nonferrous metallurgical slag as raw material, obtains qualified molten steel after reduction smelting and degassing slagging alloying, and then produces the medium-carbon quasi-bainitic steel through continuous casting blanks and controlled rolling and cooling processes, thereby forming a process route from the nonferrous metallurgical slag to the medium-carbon quasi-bainitic steel product, truly improving the utilization rate of the metallurgical slag, solving the problems of various raw materials, complex process, high energy consumption and low utilization rate of the nonferrous slag in the current nonferrous metallurgical slag iron extraction and steelmaking, and promoting the recycling and harmless mass treatment of the metallurgical slag; the value of alloy elements in the metallurgical slag is fully exerted, the variety of raw materials for steel production is enriched, the production cost is reduced, and the added value of the product is improved; has the advantages of energy conservation, environmental protection and green production.
Drawings
FIG. 1 is a process flow diagram of the method of the present invention for preparing medium carbon quasi-bainitic steel using iron-rich nonferrous metallurgical slag.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Aiming at the problems of various raw materials, complex process, high energy consumption, low utilization rate of colored slag and the like existing in the prior iron-rich colored metallurgical slag iron extraction and steelmaking, the invention forms a process route from the iron-rich colored metallurgical slag to a medium-carbon quasi-bainitic steel product by linking the utilization of the colored metallurgical slag solid waste with the steel industry, namely the method for preparing the medium-carbon quasi-bainitic steel by using the iron-rich colored metallurgical slag. The method comprises the following steps: taking iron-rich nonferrous metallurgical slag as a raw material, and obtaining molten steel with qualified components through reduction smelting and degassing, slag making and alloying; and the medium-carbon quasi-bainitic steel is produced by continuous casting blank and controlled rolling and cooling processes. Thereby effectively improving the utilization rate of metallurgical slag and promoting the recycling and harmless bulk treatment of the metallurgical slag; meanwhile, the value of alloy elements in metallurgical slag is fully exerted, the variety of raw materials for steel production is enriched, the production cost is reduced, and the added value of products is improved.
The metallurgical slag in the invention can be one or more of copper slag, red mud, nickel slag, electrolytic manganese slag, lead-zinc slag and the like. Table 1 specifically describes several nonferrous metallurgical slag components, and it can be seen from table 1 that a larger part of the nonferrous metallurgical slag rich in iron has a higher total iron content, for example, the nonferrous metallurgical slag rich in iron reaches the high-iron bayer process red mud, nickel iron slag, copper slag and the like with TFe >40%, which are far higher than the average exploitation grade of iron ore in China. In the invention, the TFe of the nonferrous metallurgical slag rich in iron is preferably more than 30%, for example, one or more selected from copper slag, bayer process red mud, blast furnace nickel slag, lead zinc slag and the like.
TABLE 1 chemical composition of nonferrous metallurgical slag
Fig. 1 schematically shows a process flow of a method for preparing medium carbon quasi-bainitic steel from iron-rich nonferrous metallurgical slag in an embodiment of the present invention. As shown in fig. 1, the method for preparing the medium carbon quasi-bainitic steel by using the iron-rich nonferrous metallurgical slag comprises the following steps:
(1) Adding a certain proportion of reducing agent and flux into the nonferrous metallurgical slag, uniformly mixing, and then sending into a high-temperature smelting device for reduction smelting to obtain molten iron and reducing slag, wherein the reducing slag melt is arranged on the upper layer of the molten iron, and tapping and deslagging are carried out irregularly.
The high-temperature smelting device can be selected from an arc furnace, a side-blown smelting furnace, a submerged arc furnace and the like, equipment or a system capable of providing stirring of a molten pool is preferably adopted, the stirring mode can be one or more of gas stirring, electromagnetic stirring and mechanical stirring, and the reaction process can be accelerated by adopting the high-temperature smelting device with a stirring structure. The iron-rich nonferrous metallurgical slag TFe is more than 30%, has better economy, and can be selected from various metallurgical slag such as copper slag, bayer process red mud, blast furnace nickel slag, lead zinc slag and the like. The reducing agent is a carbonaceous raw material, and can be, for example, bituminous coal, anthracite, lignite, and the like. The flux is used for regulating alkalinity and can be one or more of limestone, dolomite, fluorite, lime and industrial alkali.
Preferably, during reduction smelting, the iron-rich nonferrous metallurgical slag: reducing agent: flux = 100:5-15: 10 to 30 percent. After the materials in the furnace form a molten pool at 1300-1550 ℃, preserving heat for 60-180 min, and fully melting and reducing the materials can be ensured by controlling the temperature and the preserving heat time.
Further, during reduction smelting, the method also comprises the step of dynamically monitoring the content of iron elements in slag, tapping iron and deslagging when the reduction rate of iron in slag is more than or equal to 90%, and tapping iron to obtain molten iron required in the subsequent steel making process. Furthermore, slag stopping operation is needed during tapping.
(2) According to the components of molten iron, alloy auxiliary materials with a certain proportion are added into the molten iron, and the qualified molten steel and steel slag byproducts of the invention are obtained after degassing, slagging and alloying.
The steelmaking process can be carried out in a traditional oxidizing atmosphere converter, or alloy auxiliary materials can be directly put into a reduction smelting furnace after slag tapping to carry out four-step (C, P, S, O), slag forming and alloying processes.
Optionally, if the components of the molten steel subjected to degassing and slagging are difficult to meet the requirements, the components of the molten steel can be further adjusted by external refining, so that the molten steel with qualified components can be further ensured to be obtained, and the medium carbon quasi-bainitic steel meeting the requirements can be further prepared. Among them, the external refining may be one or more of LF, VD, VOD, RH, SKF furnaces.
The alloy auxiliary materials are mainly used for providing alloy elements which cannot be fully met in nonferrous metallurgical slag, and adjusting alloy components such as ferrosilicon, ferrochromium, ferroniobium, molybdenum and the like. The invention provides qualified molten steel with the alloy components (mass fraction) as follows: 0.2 to 0.3 percent of C, 1.0 to 1.5 percent of Si, 1.5 to 2.0 percent of Mn, 0.2 to 0.5 percent of Mo, 0.3 to 0.8 percent of Cr, 0.04 to 0.08 percent of Nb, less than or equal to 0.003 percent of B, less than or equal to 0.003 percent of N, less than or equal to 0.005 percent of O, less than or equal to 0.01 percent of P, and less than or equal to 0.01 percent of S; the molten steel with qualified components can ensure to obtain a quasi-bainitic structure.
Alloy components are controlled by adding the alloy auxiliary materials, the existing valuable metal elements in the nonferrous metallurgical slag are reasonably utilized, the consumption of the alloy auxiliary materials is reduced, and the production cost is reduced. The alloy components act as follows: c, improving the hardness and strength of the material; si as a non-carbide forming element inhibits carbides (particularly Fe 3 C) Is formed to enrich the carbon of the unconverted residual austenite; mn and Mo play a role in strengthening solid solution and promoting tissue bainite; cr can enhance the stability of austenite while enhancing the strength; nb mainly plays roles of fine grain strengthening and precipitation strengthening; B. the N content is too high, so that a BN brittle phase is easily formed in the steel, the performance is not beneficial to improvement, and the content of the BN brittle phase is controlled.
(3) And (3) adopting a continuous casting method, obtaining a continuous casting blank from the molten steel with qualified components through a crystallizer, performing controlled rolling and controlled cooling processes after soaking treatment, and further obtaining the medium-carbon quasi-bainitic steel with qualified tissues.
The invention adopts a continuous casting process. Compared with die casting, the invention adopts the continuous casting method, which not only simplifies the production process flow, but also improves the metal yield, reduces the energy consumption, improves the quality of the finished product and the like. The controlled rolling and controlled cooling, i.e. Thermo-mechanical processing Technology (TMCP), adopts TMCP to produce steel products, and improves the performance of the steel. In addition, the method adopts the continuous casting and rolling controlled cooling production process to prepare the quasi-bainitic steel, and compared with the traditional method for preparing the quasi-bainitic structure through long-time isothermal quenching, the method is more beneficial to energy-saving, environment-friendly and green production, and improves economic and environmental benefits.
In order to further improve the performance of the steel product, the invention continuously optimizes and improves the controlled rolling and cooling process parameters on the basis of the established chemical components, and greatly improves the performance of the steel product by selecting the optimized controlled rolling and cooling process parameters. Post-optimization parameter control in this embodiment: and (3) feeding the continuous casting blank into a tunnel soaking pit, and preserving heat for 60-120 min, wherein the soaking pit temperature is 1120-1200 ℃. Then the hot rolling mill is sent into a hot rolling unit, air-cooled to 1050-1080 ℃ for rolling in a first pass, the rolling reduction is 40%, air-cooled to 820-860 ℃ for rolling in a second pass, the rolling reduction is 30%, and then quickly cooled to 400-430 ℃ in a temperature range, and cooled to room temperature at a cooling rate of 0.5-1 ℃/s, so as to obtain the medium carbon steel mainly comprising a quasi-bainitic structure, wherein the carbon content of the steel is 0.2-0.3%.
The metallographic structure of the quasi-bainitic steel obtained by the invention is a structure formed by alternately bainitic ferrite lath and residual austenite film, has good obdurability and plasticity matching, has yield strength of more than 750MPa, tensile strength of more than 1200MPa and impact energy (V-shaped opening) of more than 40J, has elongation of more than 15 percent, and can be used for producing high-strength steel bars and the like. The main reason is that: through reasonable alloying design and rolling-cooling process control, play roles of interstitial solid solution strengthening of carbon atoms and fine crystal strengthening of lath substructure, so that the steel has excellent strength characteristics; the presence of the residual austenite in the form of a film in turn gives the bainitic structure the ability to absorb the deformation energy, resist crack initiation and propagation.
In an alternative embodiment, as shown in fig. 1, the method for preparing the medium carbon quasi-bainitic steel by using the iron-rich nonferrous metallurgical slag further comprises: the generated secondary slag is recycled, so that the full utilization of the whole components of the metallurgical slag is realized.
Specifically, the reducing slag obtained in the reduction smelting process and the steel slag obtained in the steelmaking process are adopted to prepare building raw materials such as cement admixture or concrete admixture. The two secondary slag obtained by the invention mainly comprises CaO, mgO, siO 2 And Al 2 O 3 The composition is similar to cement ingredients, is used for producing building raw materials, not only avoids the generation of a large amount of secondary slag, but also realizes the full utilization of nonferrous metallurgical slag.
Optionally, the secondary slag with higher activity can be directly prepared into active micro powder after grinding, and the active micro powder can be used as an auxiliary cementing material for selling building material enterprises. For the secondary slag with lower activity, active micro powder is prepared by adding an active exciting agent, mixing and grinding together. Wherein the active excitant can be one or more of blast furnace slag, fly ash, quicklime, cement, clinker, byproduct gypsum, sodium silicate, sodium hydroxide, sodium sulfate, tailings, triethanolamine, propylene glycol and the like. Preferably, the secondary slag: activity excitant = 100:5 to 30. Further, the specific surface area of the ground active micro powder>350m 2 And/kg, and can be used as cement mixture or concrete admixture. When the active micro powder is used as a cement mixture or a concrete admixture, the addition amount is more than or equal to 30 percent, and the higher addition amount also shows the high resource utilization efficiency of the metallurgical slag.
In the above embodiment of the present invention, there are also the following advantages:
1) The method is characterized in that iron-rich nonferrous metallurgical slag is used as a main raw material, a process route of reduction iron extraction, oxidation converting, continuous casting and continuous rolling cooling control is designed, the preparation of the medium-carbon quasi-bainitic steel is carried out, metal elements in the nonferrous slag are fully utilized through alloying design, the raw material types of steel production are enriched, the production cost is reduced, and the added value of the product is improved.
2) The development of the 700MPa medium carbon quasi-bainitic steel plate is realized through the regulation and control of rolling and cooling control parameters, and compared with the traditional process for obtaining the quasi-bainitic structure through long-time isothermal quenching, the method is more beneficial to energy conservation, environmental protection and green production; and the obtained medium-carbon quasi-bainitic steel has good toughness-plasticity matching, excellent strength characteristics and better capacities of absorbing deformation energy and resisting crack initiation and expansion.
3) The secondary slag produced in the production process can be directly or after being treated used for producing cement mixture or concrete admixture and the like, so that the full-component utilization of the colored slag is realized. Specifically, the method is to synchronously prepare active micro powder by combining carbon quasi-bainitic steel with secondary slag in the preparation of the iron-rich nonferrous metallurgical slag, namely, the three of nonferrous, steel and building industries are linked, so that the raw material types of steel production and building materials are enriched, and the recycling and harmless bulk treatment of the iron-rich nonferrous slag is promoted; the whole production process is simple in flow, fast in rhythm, high in efficiency and high in added value of products, and the utilization rate of colored slag can be effectively improved while green production is realized.
The invention will be further described with reference to the following specific examples:
example 1
Adopting iron-rich nickel slag with TFe=40% as iron-rich nonferrous metallurgical slag to prepare the medium-carbon quasi-bainitic steel:
1) Reduction and iron extraction: the adopted high-temperature smelting device is an arc furnace. Comprising the following steps: according to nickel slag: anthracite coal: limestone = 100:5: mixing the materials according to a ratio of 20, and adding the mixture into an electric arc furnace for reduction smelting; after the materials in the furnace form a molten pool at 1450 ℃, preserving the temperature for 90min, and discharging iron and slag. When the slag is discharged, the iron content in the slag is 2.48%, the obtained molten iron comprises 0.85% of C, 2.13% of Si, 0.86% of Mn, 0.059% of P, 0.056% of S, 0.15% of Cr and 0.01% of Nb, and the rest of required components can be supplemented in the auxiliary materials of the next link.
2) Alloying: auxiliary materials are matched, converter blowing and LF external refining are carried out, molten steel is obtained, and the obtained molten steel comprises the following components: 0.26% of C, 1.4% of Si, 1.8% of Mn, 0.3% of Mo, 0.5% of Cr, 0.06% of Nb, 0.0025% of B, 0.0028% of N, 0.005% of O, 0.008% of P and 0.007% of S.
3) Continuous casting, controlled rolling and controlled cooling: and (3) the molten steel is subjected to crystallizer to obtain a continuous casting blank, and the continuous casting blank is sent into a tunnel soaking pit for 120min, wherein the soaking pit temperature is 1150 ℃. And then feeding the hot-rolled steel into a hot rolling unit, air-cooling to 1050 ℃ to roll the steel for the first pass, wherein the rolling reduction is 40%, air-cooling to 850 ℃ to roll the steel for the second pass, wherein the rolling reduction is 30%, and then rapidly cooling to 400 ℃ in a temperature range, and cooling to room temperature at a cooling rate of 1 ℃/s to obtain the medium carbon steel mainly comprising a quasi-bainitic structure.
Performance test: the yield strength is 764MPa, the tensile strength is 1258MPa, the impact energy (V mouth) is 42J, and the elongation is 16%.
4) Recycling the secondary slag: grinding the secondary slag to a specific surface area of 436m 2 And (3) adding 5% of high-calcium fly ash as an exciting agent to prepare the active micro powder. Activity index of 7d and 28d thereof was measured according to GB-T18046-2017: 7d was 83%,28d was 106%.
The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Claims (7)
1. A method for preparing medium carbon quasi-bainitic steel by using iron-rich nonferrous metallurgical slag, which is characterized by comprising the following steps:
taking iron-rich nonferrous metallurgical slag as a raw material, and carrying out reduction smelting to obtain molten iron; wherein, the reduction smelting step comprises the following steps: reducing agent and flux are added, reduction smelting is carried out at 1300-1550 ℃, the temperature is kept for 60-180 min, and iron is discharged when the reduction rate of iron in slag is monitored dynamically to be more than or equal to 90%;
adding alloy auxiliary materials into molten iron according to the molten iron components, degassing, slagging and alloying to obtain molten steel with qualified components; the alloy of the qualified molten steel comprises the following components in percentage by mass: 0.2 to 0.3 percent of C, 1.0 to 1.5 percent of Si, 1.5 to 2.0 percent of Mn, 0.2 to 0.5 percent of Mo, 0.3 to 0.8 percent of Cr, 0.04 to 0.08 percent of Nb, less than or equal to 0.003 percent of B, less than or equal to 0.003 percent of N, less than or equal to 0.005 percent of O, less than or equal to 0.01 percent of P and less than or equal to 0.01 percent of S;
the method for obtaining the continuous casting blank from the molten steel with qualified components by adopting a continuous casting method through a crystallizer, and performing a controlled rolling and cooling process comprises the following steps: feeding the continuous casting blank into a tunnel soaking pit furnace, and preserving heat at 1120-1200 ℃ for 60-120 min; feeding the hot-rolled steel sheet into a hot rolling unit, performing first-pass rolling by air cooling to 1050-1080 ℃, wherein the rolling reduction is 40%, and performing second-pass rolling by air cooling to 820-860 ℃ and the rolling reduction is 30%; rapidly cooling to 400-430 ℃, and cooling to room temperature at a cooling rate of 0.5-1 ℃/s to obtain the medium-carbon quasi-bainitic steel, wherein a metallographic structure of the medium-carbon quasi-bainitic steel is a structure formed by alternately bainitic ferrite laths and residual austenite films, the yield strength is more than 750MPa, the tensile strength is more than 1200MPa, the impact power is more than 40J, and the elongation is more than 15%.
2. The method for preparing a medium carbon quasi-bainitic steel using iron-rich nonferrous metallurgical slag as set forth in claim 1, further comprising: preparing active micro powder by adopting secondary slag; wherein the secondary slag comprises: one or two of reducing slag produced by reduction smelting and steel slag produced by degassing and slagging are adopted.
3. The method for preparing a medium carbon quasi-bainitic steel using iron-rich nonferrous metallurgical slag according to claim 1, further comprising, after the step of degassing and slagging: adopting external refining to adjust the molten steel components so as to obtain molten steel with qualified components.
4. The method for preparing medium carbon quasi-bainitic steel by utilizing iron-rich nonferrous metallurgical slag according to claim 1, wherein TFe >30% in the iron-rich nonferrous metallurgical slag; the mass ratio of the iron-rich nonferrous metallurgical slag to the reducing agent to the flux is 100:5-15:10-30.
5. According to claimThe method for preparing the medium-carbon quasi-bainitic steel by using the iron-rich nonferrous metallurgical slag as defined in claim 2, wherein in the step of preparing the active micro powder by using the secondary slag, a specific surface area is obtained by adopting a direct grinding mode or a mode of grinding after adding an active exciting agent>350m 2 Active micro powder/kg; wherein the dosage ratio of the secondary slag to the activity excitant is 100:5-30; the active excitant is one or more of blast furnace slag, fly ash, quicklime, cement, clinker, byproduct gypsum, sodium silicate, sodium hydroxide, sodium sulfate, tailings, triethanolamine and propylene glycol.
6. The method for preparing the medium carbon quasi-bainitic steel by using the iron-rich nonferrous metallurgical slag according to claim 5, wherein the active micro powder is used as a cement admixture or a concrete admixture and the addition amount is more than or equal to 30%.
7. The method for preparing the medium-carbon quasi-bainitic steel by utilizing the iron-rich nonferrous metallurgical slag is characterized in that the medium-carbon quasi-bainitic steel is prepared by adopting the method for preparing the medium-carbon quasi-bainitic steel by utilizing the iron-rich nonferrous metallurgical slag as defined in claim 1.
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