A method for producing an iron-based alloy with an accompanying composite refractory material

Abstract

A preparation method of an iron-based alloy with associated composite refractory material, characterized in that it comprises the following steps: step 01, calcining chromite concentrate and iron oxide powder respectively; step 02, placing the calcined chromite concentrate in a water-cooled copper crucible, and placing it in a plasma heating furnace, and placing the iron oxide powder and aluminum in a high-position stock bin; step 03, electrifying the plasma heating furnace to melt the chromite concentrate; step 04, reducing the molten chromite concentrate and the mixed material to form an alloy layer at the bottom and a slag layer at the top; step 05, cooling by water cooling to obtain an iron-chromium-aluminum alloy and a composite refractory material. The present application melts the chromite, mixes the reducing agent with the iron oxide powder, and can flexibly adjust the amount of iron oxide according to the required iron-chromium metal ratio in the iron-chromium-aluminum product. When the reducing agent is excessive, the iron and chromium elements in the chromite and iron oxide powder are fully reduced, fully ensuring the quality of the by-produced composite refractory material.

Description

Technical Field

[0001] This invention relates to the fields of smelting technology and refractory material preparation, and particularly to a method for preparing an iron-chromium-aluminum alloy of associated composite refractory materials. Background Technology

[0002] Iron-chromium-aluminum alloy is an important electrothermal alloy, which has good oxidation resistance, high stability in use, and long service life, making it an ideal heating material in production and daily life.

[0003] For a long time, ensuring the quality of iron-chromium-aluminum alloys, especially controlling the content of elements such as carbon, sulfur, and nitrogen, has been crucial. The carbon content affects the hardness, strength, corrosion resistance, and weldability of the alloy; the sulfur content affects its hot cracking tendency and machinability; and the nitrogen content affects its strength, brittleness, and corrosion resistance. Therefore, precisely controlling the content of carbon, sulfur, and nitrogen during the preparation of iron-chromium-aluminum alloys is key to quality control. Furthermore, the current production method involves mixing various metals or alloys and then processing them using specialized smelting equipment, but this method suffers from low efficiency and high cost. Furthermore, aluminum has characteristics such as low melting point, low density, and easy oxidation during the smelting process, which poses a significant challenge to the alloying of iron-chromium-aluminum alloys. Aluminum alloys combine with oxygen to form aluminum oxide, and the presence of this oxide adversely affects the nucleation and formation of crystals in iron-chromium-aluminum alloys. While a small amount of oxide can provide a nucleation basis for grain formation and growth in iron-chromium-aluminum alloys, reducing the energy required for grain formation, and a diffusely distributed oxide film can enhance the mechanical properties of iron-chromium-aluminum alloys through grain refinement during nucleation and grain growth, increasing oxide content will negatively impact the alloying process. Therefore, controlling the oxygen content during preparation is a crucial technical problem that needs to be solved. Summary of the Invention

[0004] This invention provides a method for preparing iron-chromium-aluminum alloys for by-product composite refractory materials, which solves the shortcomings of the prior art, such as the difficulty in controlling gaseous elements and high production costs of existing iron-chromium-aluminum alloys, and can also produce composite refractory materials as by-products.

[0005] In order to achieve the objectives of this invention, the following technologies are proposed:

[0006] A method for preparing an iron-chromium-aluminum alloy composite refractory material, comprising the following steps:

[0007] Step 01, raw material pretreatment: chromite concentrate and iron oxide powder are placed in a high-temperature rotary kiln for calcination to remove harmful elements such as sulfur, arsenic, and carbon from the chromite concentrate.

[0008] Step 02, ingredient preparation: Place the roasted chromite concentrate in a water-cooled copper crucible with an inner coating, and then place the water-cooled copper crucible in a plasma heating furnace.

[0009] Among them, the water-cooled copper crucible with an inner coating has a high-temperature resistant coating with a thickness of 0.1-5mm. The main components of the high-temperature resistant coating are yttrium oxide, aluminum oxide, and zirconium oxide nanospheres, with a temperature resistance of ≥2000℃.

[0010] The roasted iron oxide powder is evenly mixed with aluminum pellets or aluminum granules, and the mixed iron oxide powder and aluminum are placed in a high-level silo connected to the plasma heating furnace.

[0011] Step 03, melting: Argon gas is introduced into the plasma heating furnace to maintain positive pressure inside the furnace. The exhaust gas is discharged through the pipeline after passing through the high-level silo. The plasma heating furnace is then powered on to melt the chromite concentrate. The protective atmosphere selected when the plasma heating furnace is working is formed by argon gas. The plasma gun and electrodes are made of non-graphite materials.

[0012] Step 04, reduction: After the chromite concentrate in step 03 is melted, the molten chromite concentrate is fed into the mixture in the high-level silo and a reduction reaction is carried out so that the bottom of the plasma heating furnace is a fluid alloy layer and the top of the plasma heating furnace is a slag layer.

[0013] Step 05, Cooling and unloading: Maintain positive pressure of argon gas in the plasma heating furnace until the slag layer is completely solidified;

[0014] The water-cooled copper crucible is cooled by water cooling until the material in the plasma heating furnace is completely cooled.

[0015] Remove the water-cooled copper crucible and the material inside it, and invert the water-cooled copper crucible to effectively separate the alloy layer and slag layer inside the water-cooled copper crucible.

[0016] The alloy layer is an iron-chromium-aluminum alloy, and the slag layer is a composite refractory material.

[0017] Further, in step 01, the chromite concentrate and iron oxide powder are calcined separately at a temperature of 1200-1500℃ for 1-5 hours.

[0018] Furthermore, the main components of chromite concentrate are 45-60% Cr2O3, 15-20% Fe2O3, 10-15% Al2O3, 10-15% MgO, 0.1-1.0% CaO, and 0.1-2.0% SiO2.

[0019] The main components of iron oxide powder are 97-99% Fe2O3, 0.1-1.0% CaO, and 0.1-2.0% SiO2.

[0020] Furthermore, in step 01, after calcining the chromite concentrate and iron oxide powder respectively, the carbon and sulfur content in the chromite concentrate and iron oxide powder is ≤20ppm.

[0021] Furthermore, in step 02, calcium oxide is added to the roasted chromite concentrate, and the amount of calcium oxide is 0.5-2.0 times the total weight of SiO2 in the chromite concentrate and iron oxide powder, and the carbon content in the calcium oxide is ≤0.01%.

[0022] Furthermore, in step 02, the amount of aluminum used is 0.35-0.5 times the total weight of Cr2O3 and Fe2O3 in chromite and iron oxide powder;

[0023] The total amount of iron oxide in iron oxide powder is 2.0-8.0 times that in chromite concentrate.

[0024] Furthermore, in step 3, argon gas with a concentration of ≥99.99% is introduced into the plasma heating furnace, and electric heating is performed after the oxygen concentration in the plasma heating furnace is ≤100ppm and the nitrogen concentration is ≤300ppm.

[0025] Furthermore, in step 3, the pressure inside the plasma heating furnace and the high-level silo is 0.001-0.1 MPa.

[0026] Furthermore, in step 5, the product is removed from the furnace when the temperature drops below 300°C.

[0027] Furthermore, in step 5, the iron-chromium-aluminum alloy contains C ≤ 0.005%, O ≤ 0.03%, N ≤ 0.005%, S ≤ 0.005%, and Si ≤ 0.03%;

[0028] The composite refractory material contains 60-80% Al2O3, 1-5% CaO, 0.5-2% SiO2, 0.1-1.0% Cr2O3, and 0.1-0.5% Fe2O3.

[0029] The advantages of the above technical solution are:

[0030] This invention uses chromite and iron oxide powder as the main raw materials, which reduces the preparation cost of iron-chromium-aluminum alloys compared to using various metals or alloys as raw materials.

[0031] This invention involves high-temperature roasting of chromite and iron oxide powder to effectively remove elements such as carbon and sulfur, thereby ensuring product quality.

[0032] This invention uses a plasma heating furnace with high-purity argon as the working gas, employs a non-carbon-containing plasma gun and electrodes, and a water-cooled copper crucible. The entire process avoids contact with carbon and sulfur-containing substances, effectively preventing the introduction of carbon and sulfur elements into the product.

[0033] This invention uses argon gas to replace the plasma heating furnace and sequentially maintains positive pressure and low oxygen and nitrogen content of argon gas in the heating furnace and high-level material silo, preventing cold air from entering during the production process. It does not require complex sealing conditions and vacuum facilities, effectively avoiding the introduction of oxygen and nitrogen elements into the product, which would have an adverse effect on the alloying of iron-chromium-aluminum alloys.

[0034] This invention melts chromite and mixes a reducing agent with iron oxide powder. The amount of iron oxide can be flexibly adjusted according to the required ratio of iron and chromium metals in the iron-chromium-aluminum product. When the reducing agent is in excess, the iron and chromium elements in the chromite and iron oxide powder are fully reduced, thus ensuring the quality of the by-product composite refractory material.

[0035] This invention introduces a small amount of calcium oxide, which can effectively fix silicon elements into the slag layer, reduce the silicon content in the iron-chromium-aluminum alloy, and at the same time, by controlling the amount of calcium oxide added, the alumina content and quality in the composite refractory material can be effectively guaranteed.

[0036] This invention applies a high-temperature resistant coating and static cooling process to water-cooled copper crucibles, which can effectively prevent copper elements from entering the iron-chromium-aluminum alloy. It also facilitates the subsequent separation of the copper crucible from the product. Static cooling can effectively prevent cold air from contacting the alloy, thus avoiding problems such as cracking and oxide formation in the alloy. Detailed Implementation

[0037] In a specific embodiment, the main components of the selected chromite concentrate and iron oxide powder are as follows:

[0038] Chromite concentrate, Cr2O3: 50.12%, Fe2O3: 19.11%, Al2O3: 14.37%, MgO: 13.55%, CaO: 0.23%, SiO2: 0.73%.

[0039] Iron oxide powder, Fe2O3: 98.36%, CaO: 0.21%, SiO2: 0.18%.

[0040] Example 1

[0041] 800 kg of chromite concentrate was calcined in a rotary kiln at 1400℃ for 3 hours, and the carbon content was found to be 0.0015% and the sulfur content to be 0.0016%. 1100 kg of iron oxide powder was calcined in a rotary kiln at 1250℃ for 1 hour, and the carbon content was found to be 0.0013% and the sulfur content to be 0.0018%.

[0042] The roasted chromite concentrate was mixed with 9.38 kg of calcium oxide and placed in a water-cooled copper crucible coated with a 1 mm high-temperature resistant coating. The mixture was then placed in a plasma heating furnace. The roasted iron oxide powder was mixed with 641.52 kg of aluminum briquettes and placed in a high-level silo, ensuring that the exhaust pipe of the plasma heating furnace was connected to the high-level silo.

[0043] Argon gas with a purity of 99.99% was introduced into the plasma heating furnace to replace the oxygen concentration to 89 ppm and the nitrogen concentration to 168 ppm, while maintaining the pressure in the high-level silo at 0.008 MPa. The plasma heating furnace was then powered on to melt the mixture of chromite concentrate and calcium oxide. After melting, the mixture in the high-level silo was heated to initiate a reduction reaction. Heating was stopped after the reaction was complete, and the argon gas supply was stopped after the slag layer had completely solidified. The furnace was then allowed to cool stagnant. Once the furnace temperature had dropped to 200°C, the water-cooled copper crucible was separated from the material to obtain iron-chromium-aluminum alloy ingots and composite refractory material ingots. The composition of the iron-chromium-aluminum alloy was tested and found to be: Cr: 22.25%, Al: 6.68%, C: 0.0033%, O: 0.0267%, N: 0.0017%, S: 0.0035%, Si: 0.022%, with the balance being Fe; the composition of the composite refractory material was: Al2O3: 89.02%, CaO: 1.04%, SiO2: 0.60%, Cr2O3: 0.24%, Fe2O3: 0.27%.

[0044] Example 2

[0045] 420 kg of chromite concentrate was calcined in a rotary kiln at 1300℃ for 3 hours, and the carbon content was found to be 0.0015% and the sulfur content was found to be 0.0013%. 1100 kg of iron oxide powder was calcined in a rotary kiln at 1350℃ for 1 hour, and the carbon content was found to be 0.0015% and the sulfur content was found to be 0.0018%.

[0046] The roasted chromite concentrate was mixed with 7.57 kg of calcium oxide and placed in a water-cooled copper crucible coated with a 2 mm high-temperature resistant coating. The mixture was then placed in a plasma heating furnace. The roasted iron oxide powder was mixed with 539.21 kg of aluminum briquettes and placed in a high-level silo, ensuring that the exhaust pipe of the plasma heating furnace was connected to the high-level silo.

[0047] Argon gas with a purity of 99.99% was introduced into the plasma heating furnace to replace the oxygen concentration to 77 ppm and the nitrogen concentration to 213 ppm, while maintaining the pressure in the high-level silo at 0.013 MPa. The plasma heating furnace was then powered on to melt the mixture of chromite concentrate and calcium oxide. After melting, the mixture in the high-level silo was heated to initiate a reduction reaction. Heating was stopped after the reaction was complete, and the argon gas supply was stopped after the slag layer had completely solidified. The furnace was then allowed to cool undisturbed. Once the furnace temperature dropped to 200°C, the water-cooled copper crucible was separated from the material to obtain iron-chromium-aluminum alloy ingots and composite refractory material ingots. The composition of the iron-chromium-aluminum alloy was tested and found to be: Cr: 13.85%, Al: 6.94%, C: 0.0041%, O: 0.0229%, N: 0.0026%, S: 0.0042%, Si: 0.017%, with the balance being Fe; the composition of the composite refractory material was: Al2O3: 92.83%, CaO: 1.07%, SiO2: 0.50%, Cr2O3: 0.27%, Fe2O3: 0.42%.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing an iron-chromium-aluminum alloy for a associated composite refractory material, characterized in that, Including the following steps: Step 01: Place the chromite concentrate and iron oxide powder in a high-temperature rotary kiln for calcination, respectively. Step 02: Place the roasted chromite concentrate into a water-cooled copper crucible with an inner coating, and then place the water-cooled copper crucible into a plasma heating furnace. The calcined iron oxide powder is uniformly mixed with aluminum, and the mixed iron oxide powder and aluminum are placed in a high-level silo connected to the plasma heating furnace. In step 02, calcium oxide is added to the roasted chromite concentrate, and the amount of calcium oxide is 0.5-2.0 times the total weight of SiO2 in the chromite concentrate and iron oxide powder, and the carbon content in the calcium oxide is ≤0.01%. Step 03: Argon gas is introduced into the plasma heating furnace to maintain positive pressure inside the furnace. The exhaust gas is discharged through the pipeline through the high-level silo. Then, the plasma heating furnace is powered on to melt the chromite concentrate. Step 04: After the chromite concentrate in Step 03 is melted, the molten chromite concentrate is fed into the mixture in the high-level silo and a reduction reaction is carried out so that the bottom of the plasma heating furnace is a fluid alloy layer and the top of the plasma heating furnace is a slag layer. Step 05: Maintain positive pressure of argon gas in the plasma heating furnace until the slag layer is completely solidified; The water-cooled copper crucible is cooled by water cooling until the material in the plasma heating furnace is completely cooled. Remove the water-cooled copper crucible and the material inside it, and invert the water-cooled copper crucible to separate the alloy layer and slag layer inside the water-cooled copper crucible. The alloy layer is an iron-chromium-aluminum alloy, and the slag layer is a composite refractory material; In step 5, the iron-chromium-aluminum alloy contains C ≤ 0.005%, O ≤ 0.03%, N ≤ 0.005%, S ≤ 0.005%, and Si ≤ 0.03%. The composite refractory material contains 60-80% Al2O3, 1-5% CaO, 0.5-2% SiO2, 0.1-1.0% Cr2O3, and 0.1-0.5% Fe2O3.

2. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, Step 01 involves calcining the chromite concentrate and iron oxide powder separately at a temperature of 1200-1500℃ for 1-5 hours.

3. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, The composition of chromite concentrate is 45-60% Cr2O3, 15-20% Fe2O3, 10-15% Al2O3, 10-15% MgO, 0.1-1.0% CaO, and 0.1-2.0% SiO2. The iron oxide powder contains 97-99% Fe2O3, 0.1-1.0% CaO, and 0.1-2.0% SiO2.

4. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, In step 01, after calcining the chromite concentrate and iron oxide powder respectively, the carbon and sulfur content in the chromite concentrate and iron oxide powder is ≤20ppm.

5. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, In step 02, the amount of aluminum used is 0.35-0.5 times the total weight of Cr2O3 and Fe2O3 in chromite and iron oxide powder; The total amount of iron oxide in iron oxide powder is 2.0-8.0 times that in chromite concentrate.

6. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, In step 3, argon gas with a concentration of ≥99.99% is introduced into the plasma heating furnace. After the oxygen concentration in the plasma heating furnace is ≤100ppm and the nitrogen concentration is ≤300ppm, the furnace is powered on for heating.

7. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, In step 3, the pressure inside the plasma heating furnace and the high-level silo is 0.001-0.1 MPa.

8. The method for preparing the iron-chromium-aluminum alloy of the associated composite refractory material according to claim 1, characterized in that, In step 5, the food is removed from the oven when the temperature drops below 300°C.