Green and efficient production method of nodular cast iron or spheroidal graphite cast steel profile

Abstract

The invention relates to a green and efficient production method of nodular cast iron or spheroidal graphite cast steel profiles, which adopts a process route of a hydrogen-rich blast furnace, an electric arc furnace, a converter, a vacuum refining furnace, a ladle refining furnace and a continuous casting machine to produce nodular cast iron / spheroidal graphite cast steel new steel material profiles. In the production process, a large amount of clean low-carbon hydrogen energy is used for replacing an original carbonaceous material to serve as a reducing agent, on one hand, the ton iron carbon emission of the product is reduced, on the other hand, oxygen, sulfur, phosphorus and other impurity elements in the material are deeply removed, and meanwhile liquid solidification of the nodular cast iron / spheroidal graphite cast steel material is achieved in a continuous casting mode; the production efficiency is improved; and the energy consumption and carbon emission of the product are further reduced.

Description

Technical Field

[0001] The present invention relates to the field of production of advanced new steel material profiles of ductile iron or ductile steel, and in particular to a green and efficient production method of ductile iron or ductile steel profiles. Background Art

[0002] Ductile iron or ductile steel materials have good comprehensive properties, low production costs, and are easy to process. They are important materials in the machinery manufacturing industry. The future development direction is to further improve the mechanical properties of ductile iron or ductile steel materials, including high strength, high toughness, good fatigue resistance and corrosion resistance, to meet the more demanding service working environment and load of components. How to further reduce harmful elements such as phosphorus, sulfur, and oxygen in the raw materials to obtain pure iron-containing raw materials for the production of ductile iron or ductile steel is a key restrictive link.

[0003] The current development direction of the ductile iron industry is to innovate the existing production methods of ductile iron materials and reduce energy consumption and environmental impact during the material production process.

[0004] With the rapid development of the hydrogen energy industry, hydrogen energy is becoming increasingly accessible and economically viable. The adoption of large-scale hydrogen-rich smelting technology in processes such as ironmaking and steelmaking will undoubtedly become an effective way to achieve green and sustainable development in steel production. Using hydrogen for reduction offers significant advantages. Hydrogen has a low density and strong diffusion capacity. As a highly efficient reducing agent, it can improve the kinetic conditions of the reduction process for complex metallurgical materials. Hydrogen's high calorific value and excellent thermal conductivity accelerate heat exchange between complex metallurgical materials and gases, improving thermal energy utilization. The reduction product of hydrogen is water, reducing pollution and carbon emissions during the production process.

[0005] Combining the relevant advantages of hydrogen metallurgy, in view of the current situation of high energy consumption, large carbon emissions and cumbersome equipment in the production process of ductile iron or ductile steel profiles, how to promote the green, low-carbon and efficient transformation of ductile iron or ductile steel profile production technology is an urgent problem that needs to be solved. Summary of the Invention

[0006] The existing production methods of ductile iron or ductile steel materials have the problems of high unit energy consumption and large carbon emissions, while the spheroidization and inoculation process of graphite is time-consuming and inefficient.

[0007] To solve the above problems, the present invention provides a green and efficient production method for graphite cast iron or ductile cast steel profiles, which adopts the production process of hydrogen-rich blast furnace-electric arc furnace / converter-vacuum degassing furnace-ladle refining furnace-continuous casting machine, wherein:

[0008] In the blast furnace smelting process, the blast furnace process adopts hydrogen-rich smelting technology, and the hydrogen consumption per ton of iron is not less than 200 cubic meters under standard conditions. Hydrogen is injected into the blast furnace from the blast furnace tuyere or the hydrogen injection port at the bottom of the furnace body to produce liquid iron-carbon alloy raw materials with low unit carbon emissions;

[0009] The alloy smelting function is completed in an electric arc furnace or a converter. The materials are proportioned according to the alloy components and content of the ductile iron / ductile steel profiles. Scrap steel, recycled materials, and liquid iron-carbon alloy raw materials are loaded into the electric arc furnace or the converter. After all the raw materials are melted, the liquid ductile iron / ductile steel raw materials are heated to the specified temperature.

[0010] In the vacuum degassing furnace smelting process, the added refined slag has the following components: w(CaO) / [w(Al2O3)+w(SiO2)]≥1.6, w(MgO)=3.5%-6%, w(SiO2)=6%-10%, w(FeO+MnO)≤0.5%, the vacuum degree is ≤66.7Pa, the vacuum degree is ≤66.7Pa, and the time for maintaining the target vacuum degree is not less than 15 minutes. During the first 2 / 3 of the vacuum smelting process, hydrogen is blown bottom at an intensity of not less than 2.5L / min / t. At the same time, a spheroidizing agent is added at an amount of 0.8% of the mass of the liquid ductile iron material. During the last 1 / 3 of the vacuum smelting process, argon is blown bottom at an intensity of not less than 2L / min / t.

[0011] In the ladle refining furnace process, an inoculant is added, and the amount of the inoculant added is 0.3% of the mass of the liquid ductile iron material.

[0012] Specifically, the composition of the finally obtained ductile iron or ductile steel profile is: C=3.8%, Si=2.3%, Mn=0.6%, S=0.005%, and P=0.01%.

[0013] Specifically, in the vacuum degassing furnace smelting process, the oxygen content in the molten steel is determined by the following formula based on the ratio of water vapor to hydrogen in the atmosphere:

[0014]

[0015] [%O]: mass percentage of oxygen in molten steel, %;

[0016] P: ambient pressure, Pa;

[0017] φ H2O : water vapor volume fraction;

[0018] φ H2 : Hydrogen gas volume fraction;

[0019] f o : Activity coefficient of oxygen in molten steel;

[0020] The amount of hydrogen injection is regulated by the above formula so that the oxygen content in the molten steel is controlled within a set range to achieve the best deoxidation and graphite ball-forming effects.

[0021] Specifically, the spheroidizing agent composition is: Mg: 5% to 6%, rare earth: 1% to 2%, Si: 35% to 38%, and Ca: 0.5% to 1%.

[0022] Specifically, the inoculant is a silicon-calcium-barium inoculant.

[0023] Specifically, the heat flux density of the continuous casting mold is 1.6 to 1.9 MW / m 2 , the secondary cooling water volume is 0.45~0.6L / kg, and the water pressure is 0.2~0.5Mpa.

[0024] Specifically, the hydrogen is clean, low-carbon green hydrogen, which is produced through gas power generation or green electricity generated by photovoltaic, wind, nuclear, hydropower and grid valley electricity, and is produced based on water electrolysis.

[0025] Technical Effects

[0026] Energy conservation, emission reduction and carbon reduction:

[0027] By using a large amount of hydrogen instead of the original carbonaceous materials as a reducing agent during the production process, the carbon emissions per ton of iron in the product are reduced. The ductile iron or ductile steel profiles produced by this process have carbon dioxide emissions per ton reduced by more than 50% compared with traditional processes.

[0028] The reduction product of hydrogen is water, which reduces pollution emissions in the production process and helps achieve green manufacturing and sustainable development.

[0029] Improve production efficiency:

[0030] The continuous casting method is used to achieve liquid solidification of ductile iron or ductile steel materials. Compared with traditional casting or horizontal continuous casting methods, it simplifies the production process, improves production efficiency, and further reduces the energy consumption of the product.

[0031] The graphite spheroidization step is set in a vacuum degassing furnace, and hydrogen is blown from the bottom of the vacuum degassing furnace to accelerate the graphite spheroidization. At the same time, the inoculation treatment is carried out in a ladle refining furnace, making the graphite spheroidization and inoculation more efficient and saving process time.

[0032] Improve product quality:

[0033] Bottom blowing of hydrogen in the vacuum degassing furnace helps the spheroidizing agent to better contact and react with the molten iron, promoting the spheroidization of graphite. At the same time, bottom blowing of argon and vacuum degassing can effectively remove excess hydrogen and some harmful gases originally present in the molten iron, thereby improving the purity of the molten iron, which is beneficial to improving the quality of castings and making the ductile iron or ductile steel profiles have better mechanical properties, including high strength, high toughness, good fatigue resistance and corrosion resistance, to meet the more demanding service working environment and load requirements of components.

[0034] Precise control of process parameters, such as the hydrogen injection rate in the blast furnace smelting process, the raw material ratio and bottom-blowing hydrogen flow rate in the electric arc furnace smelting process, the refined slag composition and bottom-blowing gas parameters in the vacuum degassing furnace smelting process, the inoculant addition amount in the ladle refining furnace process, and the crystallizer heat flux density, secondary cooling water volume and water pressure in the continuous casting process, helps to stabilize product quality and ensure that the final ductile iron or ductile steel profile has a stable composition that meets the requirements (such as C=3.8%, Si=2.3%, Mn=0.6%, S=0.005%, P=0.01%).

[0035] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a process flow chart of a green and efficient production method for ductile iron or ductile steel profiles. DETAILED DESCRIPTION

[0037] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0038] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0039] like Figure 1As shown, the present invention provides a green and efficient production method for ductile iron or ductile steel profiles, which adopts a process route of hydrogen-rich blast furnace-electric arc furnace / converter-vacuum refining furnace-ladle refining furnace-continuous casting machine. By using a large amount of hydrogen instead of the original carbonaceous material as a reducing agent during the production process of ductile iron or ductile steel profiles, on the one hand, the carbon emissions per ton of iron of the product are reduced, and on the other hand, impurity elements such as oxygen, sulfur, and phosphorus in the material are deeply removed. At the same time, a continuous casting method is used to achieve liquid solidification of the ductile iron or ductile steel material, thereby improving production efficiency and further reducing energy consumption and carbon emissions of the product.

[0040] The composition of the ductile iron profile is: C = 3.8%, Si = 2.3%, Mn = 0.6%, S = 0.005%, P = 0.01%;

[0041] In the blast furnace smelting process, the effective volume of the blast furnace is 450m 3 The hydrogen purity is 99.5%, and it is injected into the blast furnace through 16 tuyeres. The amount of hydrogen injected per ton of iron is 200Nm 3 , the temperature of the liquid iron-carbon alloy raw material produced is 1465℃, C=4.69%, Si=0.40%, Mn=0.58%, S=0.018%, P=0.26%;

[0042] In the electric arc furnace smelting process, the nominal capacity of the electric arc furnace is 70t, and 20% scrap steel and 80% liquid iron-carbon alloy raw materials are added. 2.5t of lime is added during the smelting process to make foamed slag for desulfurization and dephosphorization. During the steel tapping process, the bottom blowing hydrogen flow rate is 180Nm 3 / h, and after 5 minutes, add 2.5t of 75% ferrosilicon and 0.2t of 65% ferromanganese respectively;

[0043] During the vacuum degassing furnace smelting process, the refined slag composition is 60% CaO, 18% Al2O3, 5% MgO, 6% SiO2, and 0.5% FeO+MnO. The vacuum level is ≤ 66.7 Pa, and the target vacuum level is maintained for 20 minutes. Hydrogen is blown from the bottom for 0 to 15 minutes at a flow rate of 210 L / min. A nodulizer is added simultaneously. The nodulizer composition is 5% to 6% Mg, 1% to 2% rare earth elements, 35% to 38% Si, and 0.5% to 1% Ca. The amount of nodulizer is 0.8% of the mass of the liquid ductile iron. Argon is blown from the bottom for 15 to 20 minutes at a flow rate of 150 L / min. According to the bubble theory of graphite nodulization, the presence of a large number of small suspended bubbles in the molten iron promotes graphite nodulization. Low-boiling-point elements like magnesium, when vaporized in molten iron, form a large number of dispersed microbubbles. Carbon atoms in the molten iron diffuse and accumulate at the gas-liquid interface. Because the work required for nucleation is relatively low, graphite precipitates preferentially and grows into spheres. Furthermore, according to the interfacial energy theory of spherical graphite, the morphology of graphite in molten iron depends on the interfacial energy between the graphite's edge faces and basal planes. Graphite crystals in molten iron are hexagonal, and carbon preferentially diffuses toward crystal faces with lower interfacial energy. When sulfur and oxygen are present in the molten iron, sulfur primarily adsorbs on the edge faces, where the interfacial energy is lower than that of the basal planes, prompting graphite to grow along these faces into flake graphite. When elements like sulfur and oxygen, which have strong affinities for RE and Mg, are added to the molten iron, the amount of sulfur and oxygen adsorbed on the edge faces decreases. Once this decreases to a certain level, the interfacial energy of the basal plane falls below that of the edge faces, allowing graphite to grow into spherical graphite by means of screw dislocations.

[0044] The present invention blows hydrogen from the bottom of the vacuum degassing furnace, and simultaneously arranges the graphite spheroidization process in the vacuum degassing furnace. On the one hand, hydrogen has a large specific surface area, and the bubbles formed help the spheroidizing agent and molten iron to better contact and react, thereby further promoting the spheroidization of graphite. In addition, bottom blowing of hydrogen combined with a vacuum environment can effectively remove oxygen from the molten steel, increase the recovery rate of magnesium in the spheroidizing agent, and increase the proportion of spheroidal graphite, which is beneficial to improving the quality of castings.

[0045] In the ladle refining furnace process, an inoculant is added, and the amount of the inoculant added is 0.3% of the mass of the liquid ductile iron material. The inoculant is a silicon-calcium-barium inoculant.

[0046] The present invention arranges the graphite spheroidization step in a vacuum degassing furnace and blows hydrogen at the bottom of the vacuum degassing furnace to accelerate the graphite spheroidization, while the inoculation step is arranged in a ladle refining furnace, so that the graphite spheroidization and inoculation are more efficient, process time is saved, and production efficiency is improved.

[0047] In the continuous casting process, the arc continuous casting method is adopted, and the heat flux density of the crystallizer should be 1.6MW / m2 , the secondary cooling water volume is 0.6L / kg, and the water pressure is 0.45Mpa;

[0048] The carbon dioxide emissions per ton of ductile iron or ductile steel profiles produced by the above process are reduced by more than 50% compared with traditional processes.

[0049] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A green and efficient production method for ductile iron or ductile steel profiles, using a production process of hydrogen-rich blast furnace-arc furnace / converter-vacuum degassing furnace-ladle refining furnace-continuous casting machine, characterized in that: In the blast furnace smelting process, the blast furnace process adopts hydrogen-rich smelting technology, and the amount of hydrogen used per ton of iron is not less than 200 cubic meters under standard conditions. Hydrogen is sprayed into the blast furnace from the blast furnace tuyere or the hydrogen injection port at the bottom of the furnace body to produce liquid iron-carbon alloy raw materials with low unit carbon emissions; The alloy smelting function is completed by using an electric arc furnace or a converter. The materials are proportioned according to the alloy components and contents of the ductile iron / ductile steel profiles. Scrap steel, recycled materials, and liquid iron-carbon alloy raw materials are loaded into the electric arc furnace or the converter. After all the raw materials are melted, the liquid ductile iron / ductile steel raw materials are heated to a specified temperature. In the smelting process of the vacuum degassing furnace, the components of the refined slag added are w(CaO) / [w(Al2O3)+w(SiO2)]≥1.6, w(MgO)=3.5%~6%, w(SiO2)=6%~10%, w(FeO+MnO)≤0.5%, the vacuum degree is ≤66.7Pa, the vacuum degree is ≤66.7Pa, the maintenance time of reaching the target vacuum degree is not less than 15min, hydrogen is blown at the bottom in the first 2 / 3 time period during the vacuum smelting process, and the bottom blowing hydrogen intensity is not less than 2.5L / min / t, and a spheroidizing agent is added at the same time, the amount of the spheroidizing agent added is 0.8% of the mass of the liquid ductile iron material, and argon is blown at the bottom in the last 1 / 3 time period, and the bottom blowing argon intensity is not less than 2L / min / t; In the ladle refining furnace process, an inoculant is added, and the amount of the inoculant added is 0.3% of the mass of the liquid ductile iron material.

2. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: The final obtained ductile iron profile new steel material composition is: carbon = 3.8%, silicon = 2.3%, manganese = 0.6%, sulfur = 0.005%, phosphorus = 0.01%; the ductile steel profile new steel material composition is: carbon = 1.0-2.0%, silicon = 1.0-1.8%, manganese = 0.3-0.9%, sulfur = 0.005%, phosphorus = 0.01%.

3. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: In the vacuum degassing furnace smelting process, the oxygen content in the molten steel is determined by the following formula based on the ratio of water vapor to hydrogen in the atmosphere: [%O]: mass percentage of oxygen in molten steel, %; P: ambient pressure, Pa; φ H2O : Water vapor volume fraction; φ H2 : Hydrogen gas volume fraction; f o : Activity coefficient of oxygen in molten steel; The amount of hydrogen injection is regulated by the above formula so that the oxygen content in the molten steel is controlled within a set range to achieve the best deoxidation and graphite balling effects.

4. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: Nodulizer composition: Mg: 5% to 6%, rare earth: 1% to 2%, Si: 35% to 38%, Ca: 0.5% to 1%.

5. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: The inoculant is silicon-calcium-barium inoculant.

6. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: The heat flux density of continuous casting mold is 1.6~1.9MW / m 2 The secondary cooling water volume is 0.45~0.6L / kg, and the water pressure is 0.2~0.5Mpa.

7. The green and efficient production method for ductile iron or ductile steel profiles according to claim 1, wherein: The hydrogen is clean, low-carbon green hydrogen, which is produced through green electricity generated by gas power generation or photovoltaic, wind power, nuclear power, hydropower and grid valley power, based on the electrolysis of water.

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