Nodular cast iron powder and production process thereof
By using water atomization process and spheroidizer core wire in the production process of ductile iron powder, combining the ratio of silicon carbide and inoculant of specific sizes, talc powder and doping elements are introduced, and the desulfurization agent structure is optimized, the problems of uneven powder particle size and spheroidizer burning in traditional processes are solved, and the mechanical properties of ductile iron powder are significantly improved.
Patent Information
- Application Number
- CN202510465669.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-07-01
AI Technical Summary
In the existing ductile iron powder production process, mechanical crushing method leads to uneven distribution of powder particle size, poor fluidity, and severe burning of spherical agents, which affects the formation of spherical graphite groups and leads to poor mechanical properties and wear resistance of ductile iron.
The water atomization process is used instead of the traditional crushing process, and the spheroidizing agent core-encapsulated wire is added during the smelting process. Through the ratio of specific size silicon carbide and different silicon-containing incubators, talc powder is introduced as a pore-making agent, and the calcium element is doped with barium and magnesium, and combined with steam digestion technology, the specific surface area and pore structure of the desulfurizer are optimized.
The produced ductile iron powder has good fluidity, high loose density, and good spherical graphite group formation, which significantly improves the impact toughness, strength and wear resistance of ductile iron and enhances its mechanical properties.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of ductile iron, and particularly to a ductile iron powder and its production process. Background Art
[0002] With the continuous development of modern industrial technology, the requirements for material properties are also getting higher and higher. As a material with high strength, high toughness and excellent wear resistance, ductile iron has been widely used in the fields of automotive parts, mechanical equipment, pipeline valves, etc.
[0003] In the prior art, cast iron blocks are usually broken into powders by mechanical crushing. This method not only has high energy consumption, but also the particle size distribution of the crushed powder is uneven, and the fluidity is poor, which is difficult to meet the production requirements of high-precision and high-quality castings. In addition, in the traditional smelting process, the spheroidizing agent is often easily burned out, which results in an imperfect formation of spherical graphite clusters, affecting the mechanical properties and wear resistance of ductile iron.
[0004] More importantly, during the preparation of ductile iron, due to poor desulfurization treatment, the brittleness often increases and the mechanical properties are greatly reduced, which greatly affects the quality and performance of ductile iron powder.
[0005] In summary, it is of great significance to prepare a ductile iron powder. Summary of the Invention
[0006] The purpose of the present invention is to provide a ductile iron powder and its production process to solve the problems raised in the above background art.
[0007] To solve the above technical problems, the present invention provides the following technical solutions:
[0008] A production process of ductile iron powder, comprising the following steps:
[0009] Step 1: Melting the cast iron raw materials, followed by smelting treatment, refining and impurity removal, cooling, and tapping to obtain the cast iron stock solution;
[0010] Step 2: Adding the cast iron stock solution to a cored wire of a spheroidizing agent for spheroidizing treatment, and adding a desulfurizing agent for desulfurization treatment to obtain ductile iron liquid A;
[0011] Step 3: Adding the ductile iron liquid A to a composite inoculant for primary inoculation and secondary inoculation in sequence to obtain ductile iron liquid B;
[0012] Step 4: Crushing and refining the ductile iron liquid B by a water atomization process, followed by annealing treatment and cooling to obtain ductile iron powder.
[0013] Preferably, the composition of the ductile iron liquid B includes the following elements by mass percentage: 3.4% - 3.7% carbon, 2.4% - 3.0% silicon, 0.18% - 0.24% manganese, 0.028% - 0.032% phosphorus, 0.016% - 0.02% titanium, 0.04% - 0.05% magnesium, 0.0015% - 0.0035% chromium, and the balance is iron and unavoidable impurities ≤ 0.04%.
[0014] Preferably, in step 1, the time of the smelting treatment is 45 - 75 min, and the temperature of the smelting treatment is 1500 - 1550 °C;
[0015] The temperature of the smelting treatment is 1600 - 1650 °C;
[0016] The temperature of the refining and impurity removal is 1400 - 1450 °C.
[0017] Preferably, in step 2, the composition of the nodulizer cored wire includes the following elements by mass percentage: 28.5% - 30% magnesium, 43% - 46% silicon, 3.0% - 4.0% rare earth elements, 2.0% - 2.5% calcium, and the balance is iron;
[0018] The core diameter of the nodulizer cored wire is 12.5 - 13.5 mm, and the unit core powder weight is 190 - 200 g / m;
[0019] The wire feeding speed of the nodulizing treatment is 23 - 26 m / min, the wire feeding time is 25 - 32 s / package, and the temperature is 1400 - 1450 °C;
[0020] In the desulfurization treatment, the desulfurizer accounts for 1.1 wt% - 1.3 wt% of the ductile iron liquid A, and the desulfurization treatment temperature is 1350 - 1400 °C.
[0021] In a further embodiment, the material of the nodulizer cored wire includes one or more of magnesium, silicon, manganese, and rare earth ferrosilicon alloy.
[0022] Preferably, in step 3, during the primary inoculation, the composite inoculant accounts for 0.02 wt% - 0.04 wt% of the ductile iron liquid B;
[0023] During the secondary inoculation, the composite inoculant accounts for 0.04 wt% - 0.06 wt% of the ductile iron liquid B.
[0024] Preferably, in step 4, the specific process of the water atomization process is to set the superheat degree to 150 - 250 °C and atomize with high-pressure water at 5 - 8 MPa;
[0025] The temperature of the annealing treatment is 800 - 900 °C.
[0026] Preferably, in the raw materials of the composite inoculant, there are ferrosilicon-antimony inoculant, ferrosilicon-barium inoculant, and silicon carbide inoculant with a mass ratio of 1-1.2:1:1.5-2;
[0027] In the raw materials of the silicon carbide inoculant, there are silicon carbide inoculant A with a particle size of 45-55 nm and silicon carbide inoculant B with a particle size of 5-15 μm with a mass ratio of 1:8.5-9.5.
[0028] Preferably, the preparation process of the desulfurizer is as follows:
[0029] Step 1: Add calcium chloride and barium chloride to deionized water to obtain a mixed solution; add potassium carbonate to deionized water to obtain a potassium carbonate solution; adjust the pH to 9.0-10.0 and react for 5-15 min at 20-30 °C for the mixed solution and the potassium carbonate solution, filter, and dry to obtain calcium carbonate and barium carbonate; add magnesium oxide particles to the potassium carbonate solution, adjust the pH to 9.0-10.0 and react for 5-15 min at 600-800 °C, react for 2-3 hours, cool, filter, and dry to obtain magnesium carbonate;
[0030] Step 2: Calcinate magnesium carbonate, calcium carbonate, barium carbonate, and talcum powder at 900-1100 °C for 30-60 min, cool, and then perform steam digestion treatment at 200-240 °C under a pressure of 0.44-0.46 MPa, take out and cool to obtain the desulfurizer.
[0031] In the solution, silicon carbide with a specific size is proportioned with different silicon-containing inoculants according to a specific ratio to improve the impact toughness, strength, wear resistance and other properties of ductile iron; by introducing talcum powder as a pore-forming agent, doping calcium element with barium element and magnesium element, and using steam digestion technology and other means, the specific surface area and pore structure are improved, the adsorption performance is enhanced, and the desulfurization performance of the desulfurizer and the mechanical properties of ductile iron are further improved.
[0032] Among them, silicon carbide is used as part of the inoculant to supplement carbon and silicon elements, reduce the solidification time, increase the number of nodular particles, have a high spheroidization rate, promote the precipitation of graphite, and improve the mechanical properties and hardness of ductile iron powder. However, silicon carbide is prone to agglomeration. Therefore, silicon carbide particles of different sizes are proportioned and then compounded with antimony inoculant and ferrosilicon-barium inoculant to supplement barium and rare earth elements, which can form graphite crystal nuclei, promote the spheroidization of graphite, help control the graphite morphology, increase its sphericity, and further enhance the hardness, wear resistance, impact resistance, fatigue resistance and other properties of ductile iron.
[0033] Among them, barium and magnesium elements are doped into calcium element to effectively increase the amount of vacant sites. Talc powder is added as a pore-forming agent to synergistically generate a porous structure, increase the specific surface area of the desulfurizer, enhance the pore structure, increase the contact with sulfides, and thus improve the desulfurization performance. Finally, technical means such as evaporation digestion are used to further activate the desulfurizer, making it have higher activity and better desulfurization performance.
[0034] Preferably, the raw materials of the mixed solution include the following components: by mass, 14 - 15 parts of calcium chloride, 4.5 - 5.5 parts of barium chloride, and 80 - 81 parts of deionized water;
[0035] The raw materials of the potassium carbonate solution include potassium carbonate and deionized water with a mass ratio of 1:7 - 7.5;
[0036] In the raw materials of the desulfurizer, it includes magnesium carbonate, calcium carbonate, barium carbonate, and talc powder with a mass ratio of 0.5 - 1:4 - 6:0.5 - 1:0.08 - 0.12.
[0037] Compared with the prior art, the beneficial effects of the present invention are:
[0038] 1. In the solution, the water atomization process is adopted to replace the traditional crushing process. The produced ductile iron powder has good powder fluidity and high apparent density. After smelting, the graphite in the ductile iron dissolves. When adding the nodulizer cored wire during smelting, the problem of serious nodulizer burning loss is effectively solved, promoting the formation of spherical graphite clusters, and producing ductile iron powder with spherical graphite morphology.
[0039] 2. In the solution, by adopting a reasonable ratio of silicon carbide with a specific size and different silicon-containing inoculants, the impact toughness, strength, and wear resistance of ductile iron are improved. At the same time, talc powder is introduced as a pore-forming agent, barium and magnesium elements are doped into calcium element, and combined with steam digestion technology, the specific surface area and pore structure of the desulfurizer are optimized, improving its desulfurization performance, thereby further enhancing the mechanical properties of ductile iron. Specific Embodiments
[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.
[0041] It should be noted that the following parts are by mass, and there are no special restrictions on the manufacturers of the raw materials involved in the present invention. Exemplarily, including: in the following examples, the particle size of silicon carbide powder A is 10 μm; the particle size of silicon carbide powder B is 50 nm; the nodulizer cored wire is rare earth ferrosilicon alloy, and the product number is j1-20200601; the silicon-antimony inoculant is purchased from Henan Junliao Metallurgical Materials Co., Ltd.; the specification of the silicon-barium inoculant is 2 mm; the specification of talcum powder is 300 mesh.
[0042] In the following embodiments, it is particularly noted that:
[0043] (1) The composition of ductile iron liquid B includes the following elements, by mass percentage: 3.6% carbon, 2.67% silicon, 0.201% manganese, 0.030% phosphorus, 0.018% titanium, 0.043% magnesium, 0.0029% chromium, and the rest is iron and unavoidable impurities of 0.02%.
[0044] (2) The composition of the nodulizer cored wire includes the following elements, by mass percentage: 29.5% magnesium, 44.5% silicon, 3.5% rare earth elements, 2.2% calcium, and the rest is iron.
[0045] (3) The core diameter of the nodulizer cored wire is 13 mm, and the unit core powder weight is 195 g / m.
[0046] Example 1: A production process of ductile iron powder, comprising the following steps:
[0047] Step 1: Mix the silicon-antimony inoculant, silicon-barium inoculant, and silicon carbide inoculant according to a mass ratio of 1.1:1:1.75. The silicon carbide inoculant includes silicon carbide inoculant A with a particle size of 50 nm and silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1:9 to obtain a composite inoculant;
[0048] Step 2: Preparation of desulfurizer: (1) Add 14.24 parts of calcium chloride and 5.03 parts of barium chloride to 80.73 parts of deionized water to obtain a mixed solution; add potassium carbonate to deionized water, and the mass ratio of potassium carbonate to deionized water is 1:7.2 to obtain a potassium carbonate solution; adjust the pH of the mixed solution and the potassium carbonate solution to 9.5 at 25°C and react for 10 min, filter, and dry to obtain calcium carbonate and barium carbonate; add magnesium oxide particles to the potassium carbonate solution at 700°C, adjust the pH to 9.5 and react for 10 min, react for 2.5 hours, cool, filter, and dry to obtain magnesium carbonate; (2) Calcinate magnesium carbonate, calcium carbonate, barium carbonate, and talcum powder at 1000°C for 45 min. The mass ratio of magnesium carbonate, calcium carbonate, barium carbonate, and talcum powder is 0.7:5:0.7:0.1, cool, and then perform steam digestion treatment at 220°C and a pressure of 0.45 MPa, take out and cool to obtain the desulfurizer;
[0049] Step 3: Melting the cast iron raw materials at 1525 °C for 60 min, then conducting smelting treatment at 1625 °C, and performing refining and impurity removal, cooling, and tapping at 1425 °C to obtain the original cast iron liquid;
[0050] Step 4: Adding the original cast iron liquid to the nodulizer cored wire, setting the wire feeding speed at 25 m / min and the wire feeding time at 28 s / package, conducting nodulizing treatment at 1425 °C, and then adding a desulfurizing agent for desulfurization treatment at 1375 °C. The desulfurizing agent accounts for 1.2 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0051] Step 5: Adding a composite inoculant to the ductile iron liquid A for primary inoculation. The composite inoculant accounts for 0.03 wt% of the ductile iron liquid B, and then adding the composite inoculant again for secondary inoculation. The composite inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0052] Step 6: Setting the superheat degree of the ductile iron liquid B at 200 °C, atomizing, crushing, and refining it with high-pressure water at 6 MPa, and then conducting annealing treatment at 850 °C, followed by cooling to obtain ductile iron powder.
[0053] Example 2: A production process of ductile iron powder, comprising the following steps:
[0054] Step 1: Mixing a silicon-antimony inoculant, a silicon-barium inoculant, and a silicon carbide inoculant in a mass ratio of 1:1:1.5. The silicon carbide inoculant includes a silicon carbide inoculant A with a particle size of 50 nm and a silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1:8.5 to obtain a composite inoculant;
[0055] Step 2: Preparation of the desulfurizing agent: (1) Adding 14.24 parts of calcium chloride and 5.03 parts of barium chloride to 80.73 parts of deionized water to obtain a mixed solution; adding potassium carbonate to deionized water with a mass ratio of potassium carbonate to deionized water of 1:7.2 to obtain a potassium carbonate solution; adjusting the pH to 9.0 and reacting for 10 min at 25 °C with the mixed solution and the potassium carbonate solution, filtering, and drying to obtain calcium carbonate and barium carbonate; adding magnesium oxide particles to the potassium carbonate solution at 700 °C, adjusting the pH to 9.0 and reacting for 10 min, reacting for 2.5 hours, cooling, filtering, and drying to obtain magnesium carbonate; (2) Calcining magnesium carbonate, calcium carbonate, barium carbonate, and talc powder at 900 °C for 30 min. The mass ratio of magnesium carbonate, calcium carbonate, barium carbonate, and talc powder is 0.5:4:0.5:0.08, cooling, and then conducting steam digestion treatment at 200 °C and a pressure of 0.44 MPa, taking it out and cooling to obtain the desulfurizing agent;
[0056] Step 3: Melting the cast iron raw materials at 1525°C for 60 minutes, then conducting smelting treatment at 1625°C, and carrying out refining to remove impurities, cooling, and tapping at 1425°C to obtain the original cast iron liquid;
[0057] Step 4: Adding the original cast iron liquid to the nodulizer cored wire, setting the wire feeding speed at 25 m / min and the wire feeding time at 28 s / package, conducting nodulizing treatment at 1425°C, and then adding a desulfurizing agent for desulfurization treatment at 1375°C. The desulfurizing agent accounts for 1.1 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0058] Step 5: Adding a composite inoculant to the ductile iron liquid A for primary inoculation. The composite inoculant accounts for 0.03 wt% of the ductile iron liquid B. Subsequently, adding the composite inoculant again for secondary inoculation. The composite inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0059] Step 6: Setting the superheat degree of the ductile iron liquid B at 200°C, atomizing, crushing, and refining it with high-pressure water at 6 MPa, and then conducting annealing treatment at 850°C, followed by cooling to obtain ductile iron powder.
[0060] Example 3: A production process of ductile iron powder, comprising the following steps:
[0061] Step 1: Mixing a silicon-antimony inoculant, a silicon-barium inoculant, and a silicon carbide inoculant in a mass ratio of 1.2:1:2. The silicon carbide inoculant includes a silicon carbide inoculant A with a particle size of 50 nm and a silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1:9.5 to obtain a composite inoculant;
[0062] Step 2: Preparation of the desulfurizing agent: (1) Adding 14.24 parts of calcium chloride and 5.03 parts of barium chloride to 80.73 parts of deionized water to obtain a mixed solution; adding potassium carbonate to deionized water, with the mass ratio of potassium carbonate to deionized water being 1:7.2, to obtain a potassium carbonate solution; adjusting the pH to 9.5 and reacting for 10 minutes at 25°C with the mixed solution and the potassium carbonate solution, filtering, and drying to obtain calcium carbonate and barium carbonate; adding magnesium oxide particles to the potassium carbonate solution at 700°C, adjusting the pH to 9.5 and reacting for 10 minutes, reacting for 2.5 hours, cooling, filtering, and drying to obtain magnesium carbonate; (2) Calcining magnesium carbonate, calcium carbonate, barium carbonate, and talc powder at 1100°C for 60 minutes, with the mass ratio of magnesium carbonate, calcium carbonate, barium carbonate, and talc powder being 1∶6:1∶0.12, cooling, and then conducting steam digestion treatment at 240°C and a pressure of 0.46 MPa, taking out and cooling to obtain the desulfurizing agent;
[0063] Step 3: Melting the cast iron raw materials at 1525 °C for 60 min, then conducting smelting treatment at 1625 °C, and performing refining to remove impurities, cooling, and tapping at 1425 °C to obtain the cast iron stock solution;
[0064] Step 4: Adding the cast iron stock solution to the nodulizer cored wire, setting the wire feeding speed at 25 m / min and the wire feeding time at 28 s / package, conducting nodulizing treatment at 1425 °C, and then adding a desulfurizer for desulfurization treatment at 1375 °C. The desulfurizer accounts for 1.3 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0065] Step 5: Adding a composite inoculant to the ductile iron liquid A for primary inoculation. The composite inoculant accounts for 0.03 wt% of the ductile iron liquid B, and then adding the composite inoculant again for secondary inoculation. The composite inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0066] Step 6: Setting the superheat degree of the ductile iron liquid B at 200 °C, atomizing, crushing, and refining it with high-pressure water at 6 MPa, and then conducting annealing treatment at 850 °C, followed by cooling to obtain the ductile iron powder.
[0067] Comparative Example 1: Based on Example 1, adding a nodulizer without using a nodulizer cored wire, with the remaining processes unchanged. Specifically:
[0068] Step 1: Mixing the silicon-antimony inoculant, silicon-barium inoculant, and silicon carbide inoculant in a mass ratio of 1.1∶1∶1.75. The silicon carbide inoculant includes silicon carbide inoculant A with a particle size of 50 nm and silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1:9 to obtain a composite inoculant;
[0069] Step 2: Preparation of the desulfurizer: (1) Adding 14.24 parts of calcium chloride and 5.03 parts of barium chloride to 80.73 parts of deionized water to obtain a mixed solution; adding potassium carbonate to deionized water, with the mass ratio of potassium carbonate to deionized water being 1:7.2, to obtain a potassium carbonate solution; adjusting the pH to 9.5 and reacting for 10 min at 25 °C with the mixed solution and the potassium carbonate solution, filtering, and drying to obtain calcium carbonate and barium carbonate; adding magnesium oxide particles to the potassium carbonate solution at 700 °C, adjusting the pH to 9.5 and reacting for 10 min, reacting for 2.5 hours, cooling, filtering, and drying to obtain magnesium carbonate; (2) Calcining magnesium carbonate, calcium carbonate, barium carbonate, and talc powder at 1000 °C for 45 min, with the mass ratio of magnesium carbonate, calcium carbonate, barium carbonate, and talc powder being 0.7:5:0.7:0.1, cooling, and then conducting steam digestion treatment at 220 °C and a pressure of 0.45 MPa, taking it out and cooling to obtain the desulfurizer;
[0070] Step 3: The cast iron raw materials are melted at 1525°C for 60 minutes, then smelted at 1625°C, refined to remove impurities, cooled, and taken out of the furnace at 1425°C to obtain the original cast iron liquid;
[0071] Step 4: Add the original cast iron liquid and a spheroidizing agent and conduct spheroidizing treatment at 1425°C. The addition amount of the spheroidizing agent accounts for 1.2 wt% of the ductile iron liquid A. Subsequently, add a desulfurizing agent at 1375°C for desulfurization treatment. The desulfurizing agent accounts for 1.2 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0072] Step 5: Add the ductile iron liquid A and a composite inoculant for primary inoculation. The composite inoculant accounts for 0.03 wt% of the ductile iron liquid B. Subsequently, add the composite inoculant again for secondary inoculation. The composite inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0073] Step 6: Set the superheat degree of the ductile iron liquid B to 200°C, atomize, break, and refine it with high-pressure water at 6 MPa. Subsequently, conduct annealing treatment at 850°C, cool, and obtain ductile iron powder.
[0074] In this technical solution, the spheroidizing agent is a rare earth ferrosilicon magnesium alloy spheroidizing agent, and the model is 2-6 / 3-8.
[0075] Comparative Example 2: Based on Example 1, replace the composite inoculant with silicon carbide powder of a single size, and the rest of the process remains unchanged. Specifically:
[0076] Step 1: Preparation of the desulfurizing agent: (1) Add 14.24 parts of calcium chloride and 5.03 parts of barium chloride to 80.73 parts of deionized water to obtain a mixed solution; add potassium carbonate to deionized water, and the mass ratio of potassium carbonate to deionized water is 1:7.2 to obtain a potassium carbonate solution; adjust the pH to 9.5 and react for 10 minutes at 25°C with the mixed solution and the potassium carbonate solution, filter, and dry to obtain calcium carbonate and barium carbonate; add magnesium oxide particles to the potassium carbonate solution at 700°C, adjust the pH to 9.5 and react for 10 minutes, react for 2.5 hours, cool, filter, and dry to obtain magnesium carbonate; (2) Calcinate magnesium carbonate, calcium carbonate, barium carbonate, and talcum powder at 1000°C for 45 minutes. The mass ratio of magnesium carbonate, calcium carbonate, barium carbonate, and talcum powder is 0.7:5:0.7:0.1, cool, and then conduct steam digestion treatment at 220°C and a pressure of 0.45 MPa, take out and cool to obtain the desulfurizing agent;
[0077] Step 2: The cast iron raw materials are melted at 1525°C for 60 minutes, then smelted at 1625°C, refined to remove impurities, cooled, and taken out of the furnace at 1425°C to obtain the original cast iron liquid;
[0078] Step 3: Add the as-cast iron stock solution to the spheroidizing agent and conduct spheroidizing treatment at 1425°C. The addition amount of the spheroidizing agent accounts for 1.2 wt% of the ductile iron liquid A. Subsequently, add the desulfurizing agent at 1375°C for desulfurization treatment. The desulfurizing agent accounts for 1.2 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0079] Step 4: Add the ductile iron liquid A to the silicon carbide inoculant with a particle size of 10 μm for primary inoculation. The compound inoculant accounts for 0.03 wt% of the ductile iron liquid B. Subsequently, add the silicon carbide inoculant with a particle size of 10 μm again for secondary inoculation. The compound inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0080] Step 5: Set the superheat degree of the ductile iron liquid B to 200°C, atomize it with high-pressure water at 6 MPa for crushing and refinement, and then conduct annealing treatment at 850°C and cool to obtain ductile iron powder.
[0081] Comparative Example 3: Based on Example 1, without adding the desulfurizing agent and the rest of the process remains unchanged. Specifically:
[0082] Step 1: Mix the silicon-antimony inoculant, silicon-barium inoculant, and silicon carbide inoculant according to a mass ratio of 1.1∶1∶1.75. The silicon carbide inoculant includes silicon carbide inoculant A with a particle size of 50 nm and silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1∶9 to obtain a compound inoculant;
[0083] Step 2: Conduct smelting treatment on the cast iron raw materials at 1525°C for 60 min, then conduct smelting treatment at 1625°C, conduct refining and impurity removal, cooling, and tapping at 1425°C to obtain the as-cast iron stock solution;
[0084] Step 3: Add the as-cast iron stock solution to the spheroidizing agent and conduct spheroidizing treatment at 1425°C. The addition amount of the spheroidizing agent accounts for 1.2 wt% of the ductile iron liquid A. Subsequently, conduct desulfurization treatment at 1375°C to obtain the ductile iron liquid A;
[0085] Step 4: Add the ductile iron liquid A to the compound inoculant for primary inoculation. The compound inoculant accounts for 0.03 wt% of the ductile iron liquid B. Subsequently, add the compound inoculant again for secondary inoculation. The compound inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0086] Step 5: Set the superheat degree of the ductile iron liquid B to 200°C, atomize it with high-pressure water at 6 MPa for crushing and refinement, and then conduct annealing treatment at 850°C and cool to obtain ductile iron powder.
[0087] Comparative Example 4: Based on Example 1, without doping magnesium and barium elements in the preparation of the desulfurizing agent and the rest of the process remains unchanged. Specifically:
[0088] Step 1: Mix the silicon-antimony inoculant, silicon-barium inoculant, and silicon carbide inoculant in a mass ratio of 1.1∶1∶1.75. The silicon carbide inoculant includes silicon carbide inoculant A with a particle size of 50 nm and silicon carbide inoculant B with a particle size of 10 μm in a mass ratio of 1∶9 to obtain a composite inoculant;
[0089] Step 2: Preparation of the desulfurizer: Calcinate calcium oxide and talcum powder at 1000 °C for 45 min. The mass ratio of calcium oxide to talcum powder is 5.5:0.1. Cool, and then perform steam digestion treatment at 220 °C and a pressure of 0.45 MPa. Take it out and cool to obtain the desulfurizer;
[0090] Step 3: Carry out smelting treatment on the cast iron raw materials at 1525 °C for 60 min, then carry out smelting treatment at 1625 °C, and carry out refining and impurity removal, cooling, and tapping at 1425 °C to obtain the original cast iron liquid;
[0091] Step 4: Add the original cast iron liquid to the spheroidizing agent and carry out spheroidizing treatment at 1425 °C. The addition amount of the spheroidizing agent accounts for 1.2 wt% of the ductile iron liquid A. Then add the desulfurizer at 1375 °C for desulfurization treatment. The desulfurizer accounts for 1.2 wt% of the ductile iron liquid A to obtain the ductile iron liquid A;
[0092] Step 5: Add the ductile iron liquid A to the composite inoculant for primary inoculation. The composite inoculant accounts for 0.03 wt% of the ductile iron liquid B. Then add the composite inoculant again for secondary inoculation. The composite inoculant accounts for 0.05 wt% of the ductile iron liquid B to obtain the ductile iron liquid B;
[0093] Step 6: Set the superheat degree of the ductile iron liquid B to 200 °C, atomize it with high-pressure water at 6 MPa, break and refine it, and then carry out annealing treatment at 850 °C, cool to obtain ductile iron powder.
[0094] Detection experiment: Test the performance of a kind of ductile iron powder prepared in Examples 1-3 and Comparative Examples 1-4: (1) Tensile strength test: Sinter the ductile iron powder prepared in Examples 1-3 and Comparative Examples 1-4 into a block product and refer to "GB / T 9440-2008" for the tensile strength test. The test results are shown in Table 1; (2) Impact toughness test: Sinter the ductile iron powder prepared in Examples 1-3 and Comparative Examples 1-4 into a block product and carry out the impact toughness test at -20 °C. The results are shown in Table 1;
[0095]
[0096] Table 1
[0097] Result analysis: It can be seen from the data analysis in Table 1 that by using the water atomization process to replace the traditional crushing process, the produced ductile iron powder has good powder fluidity and high apparent density. After smelting, the graphite in the ductile iron dissolves, and a cored wire of spheroidizing agent is added during smelting, effectively solving the problem of serious burning loss of the spheroidizing agent and promoting the formation of spherical graphite clusters, thus producing ductile iron powder with spherical graphite morphology. In the solution, by adopting a reasonable ratio of silicon carbide with a specific size and different silicon-containing inoculants, the impact toughness, strength and wear resistance of ductile iron are improved. At the same time, talcum powder is introduced as a pore-forming agent, calcium element is doped with barium and magnesium elements, and combined with steam digestion technology, the specific surface area and pore structure of the desulfurizer are optimized, and its desulfurization performance is improved, thereby further enhancing the mechanical properties of ductile iron.
[0098] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced by the present invention.
Claims
1. A production process for ductile iron powder, characterized in that: The following steps are involved: Step 1: smelting the cast iron raw material, followed by smelting, refining and impurity removal, cooling, and furnace discharge to obtain cast iron stock solution; Step 2: adding the spheroidizing agent cored wire to the cast iron stock liquid for spheroidizing treatment, and adding the desulfurizing agent for desulfurization treatment to obtain ductile iron liquid A; Step 3: adding the composite inoculant to the ductile iron liquid A for primary inoculation and secondary inoculation in sequence to obtain the ductile iron liquid B; Step 4: The ductile iron liquid B is crushed and refined by a water atomization process, and then annealed and cooled to obtain ductile iron powder.
2. The production process of ductile iron powder according to claim 1, characterized in that: The composition of the ductile iron liquid B includes the following elements, calculated by mass percentage: 3.4% to 3.7% carbon, 2.4% to 3.0% silicon, 0.18% to 0.24% manganese, 0.028% to 0.032% phosphorus, 0.016% to 0.02% titanium, 0.04% to 0.05% magnesium, 0.0015% to 0.0035% chromium, and the rest is iron and unavoidable impurities ≤ 0.04%.
3. The production process of ductile iron powder according to claim 1, characterized in that: In step 1, the smelting treatment time is 45 to 75 minutes, and the smelting treatment temperature is 1500 to 1550° C.; The temperature of the smelting treatment is 1600-1650°C; The temperature of the refining and impurity removal is 1400-1450°C.
4. The production process of ductile iron powder according to claim 1, characterized in that: In step 2, the composition of the spheroidizer cored wire includes the following elements, by mass percentage: 28.5% to 30% magnesium, 43% to 46% silicon, 3.0% to 4.0% rare earth elements, 2.0% to 2.5% calcium, and the remainder iron; The core diameter of the spheroidizing agent cored wire is 12.5-13.5 mm, and the unit core powder weight is 190-200 g / m; The wire feeding speed of the spheroidization treatment is 23-26 m / min, the wire feeding time is 25-32 s / bag, and the temperature is 1400-1450°C; In the desulfurization treatment, the desulfurizer accounts for 1.1wt% to 1.3wt% of the ductile iron liquid A, and the desulfurization treatment temperature is 1350 to 1400°C.
5. The production process of ductile iron powder according to claim 1, characterized in that: In step 3, during the one inoculation process, the composite inoculant accounts for 0.02wt% to 0.04wt% of the ductile iron liquid B; During the secondary inoculation, the composite inoculant accounts for 0.04wt% to 0.06wt% of the ductile iron liquid B.
6. The production process of ductile iron powder according to claim 1, characterized in that: In step 4, the specific process of the water atomization process is to set the superheat to 150-250° C. and use high-pressure water for atomization at 5-8 MPa; The temperature of the annealing treatment is 800-900°C.
7. The production process of ductile iron powder according to claim 5, characterized in that: The raw materials of the composite inoculant include silicon-antimony inoculant, silicon-barium inoculant and silicon carbide inoculant in a mass ratio of 1-1.2:1:1.5-2; The raw materials of the silicon carbide inoculant include a silicon carbide inoculant A with a particle size of 45 to 55 nm and a silicon carbide inoculant B with a particle size of 5 to 15 μm in a mass ratio of 1:8.5 to 9.
5.
8. The production process of ductile iron powder according to claim 4, characterized in that: The preparation process of the desulfurizer is as follows: Step 1: adding calcium chloride and barium chloride to deionized water to obtain a mixed solution; adding potassium carbonate to deionized water to obtain a potassium carbonate solution; adjusting the pH of the mixed solution and the potassium carbonate solution to 9.0-10.0 at 20-30° C. and reacting for 5-15 minutes, filtering, and drying to obtain calcium carbonate and barium carbonate; adding magnesium oxide particles to the potassium carbonate solution at 600-800° C., adjusting the pH to 9.0-10.0 and reacting for 5-15 minutes, reacting for 2-3 hours, cooling, filtering, and drying to obtain magnesium carbonate; Step 2: calcine magnesium carbonate, calcium carbonate, barium carbonate and talc at 900-1100° C. for 30-60 min, cool, and then steam digest at 200-240° C. and 0.44-0.46 MPa, take out and cool to obtain a desulfurizer.
9. The production process of ductile iron powder according to claim 8, characterized in that: The raw materials of the mixed solution include the following components: 14-15 parts of calcium chloride, 4.5-5.5 parts of barium chloride, and 80-81 parts of deionized water, by mass. The raw materials of the potassium carbonate solution include potassium carbonate and deionized water in a mass ratio of 1:7 to 7.5; The raw materials of the desulfurizer include magnesium carbonate, calcium carbonate, barium carbonate and talcum powder in a mass ratio of 0.5-1:4-6:0.5-1:0.08-0.
12.
10. Ductile iron powder prepared according to the production process of ductile iron powder according to any one of claims 1 to 9.