Optimized formula of low-rare earth composite spheroidizing agent and preparation process thereof

Abstract

The application discloses an optimized formula of a low-rare earth composite spheroidizing agent and a preparation process thereof, and belongs to the field of spheroidizing agent preparation. The spheroidizing agent is prepared from the following components in mass parts: magnesium (Mg): 50-75 parts; rare earth elements (RE): 8-15 parts; silicon (Si): 30-40 parts; calcium (Ca): 8-15 parts; barium (Ba): 5-10 parts; zirconium (Zr): 3-6 parts; yttrium (Y): 0.5-1 part; and iron and impurities: 1-2 parts. The total amount of rare earth elements in the application is very small, far lower than that of conventional low-rare earth spheroidizing agents and traditional rare earth spheroidizing agents, so that the consumption of rare earth resources is greatly reduced, the production cost is reduced, the negative influence of rare earth enrichment on the performance of castings is reduced, the development trend of environmental protection and resource saving is met, the spheroidizing rate is ensured to be greater than or equal to 95% under the condition of low rare earth consumption through the synergistic proportioning of Ce, La and Y, and the roundness of graphite balls is high, and there is no broken graphite and other abnormal structures.

Description

Technical Field

[0001] This invention belongs to the field of spheroidizing agent preparation, specifically an optimized formulation and preparation process of a low rare earth composite spheroidizing agent. This invention is applicable to the spheroidizing treatment of ductile iron, and is especially suitable for casting scenarios with high requirements for cost control, environmental protection, and stable mechanical properties of castings. Background Technology

[0002] Spheroidizing agents are core auxiliary materials in the production process of ductile iron. Their role is to transform flake graphite in cast iron into spheroidal graphite, thereby significantly improving the mechanical properties of cast iron, such as strength, toughness, and wear resistance, and broadening the application range of ductile iron. Currently, the spheroidizing agents widely used in industry are mainly rare earth magnesium-silicon spheroidizing agents. Among them, rare earth elements (such as cerium and yttrium) are key components for achieving efficient spheroidization, which can refine graphite spheroids, suppress interference from anti-spheroidizing elements, and reduce the tendency for white iron. However, rare earth resources are scarce and expensive. Excessive use will not only significantly increase production costs, but may also lead to defects such as rare earth enrichment and graphite distortion in castings, and worsen the low-temperature impact toughness of castings.

[0003] To address the issue of excessive rare earth usage, various low-rare earth spheroidizing agent solutions have emerged in existing technologies, but they still have several shortcomings: First, some low-rare earth spheroidizing agents achieve cost control by simply reducing the amount of rare earth, resulting in insufficient spheroidizing ability, low spheroidization rate, poor graphite spheroid roundness, and a tendency to produce fragmented graphite and other variant structures, leading to unstable mechanical properties of castings; Second, existing low-rare earth spheroidizing agents mostly use single rare earth elements or simple composite rare earths, lacking synergistic design with other alloying elements, and have weak resistance to interference from anti-spheroidizing elements (such as titanium, antimony, lead, etc.), making them prone to defects. The spheroidization decay phenomenon is particularly pronounced when using molten iron with high sulfur and high anti-spheroidizing element content, resulting in a persistently high defect rate. Thirdly, the preparation process often employs traditional medium-frequency induction furnaces for direct melting, leading to uneven component mixing, severe loss of effective elements (such as magnesium and rare earth elements), low absorption rate, large fluctuations in product particle size, and a high content of fine powder, further affecting the stability of the spheroidization effect. Fourthly, some low-rare-earth spheroidizing agents excessively increase silicon content to compensate for insufficient spheroidization ability, resulting in excessively high final silicon content in the molten iron, affecting the machinability of castings and easily causing casting defects such as shrinkage cavities and porosity.

[0004] Existing technology discloses a novel low-silicon, low-rare-earth spheroidizing agent, whose rare-earth component is a composite of cerium oxide, yttrium oxide, and rubidium oxide. Although this reduces the amount of rare earth elements used, it still suffers from insufficient synergistic effect of rare earth elements and limited anti-interference ability. Furthermore, the preparation process only uses a conical crushing roller for crushing followed by direct melting, resulting in poor component mixing uniformity and difficulty in improving the effective element absorption rate. Therefore, the optimized formulation and preparation process of the low-rare-earth composite spheroidizing agent of this invention have emerged.

[0005] Developing a low-rare-earth composite spheroidizing agent with low rare-earth content, stable spheroidizing effect, strong anti-interference ability, simple and efficient preparation process, controllable cost, and adaptability to various casting scenarios has become an urgent technical problem to be solved in the current casting field. Summary of the Invention

[0006] To address the shortcomings of existing low-rare-earth spheroidizing agents, such as insufficient spheroidizing ability, unstable mechanical properties, weak anti-interference ability, unreasonable preparation process, and low absorption rate of effective elements, this invention provides an optimized formulation and preparation process for a low-rare-earth composite spheroidizing agent. By scientifically proportioning rare-earth components and auxiliary alloying elements, the amount of rare-earth used is further reduced, while the spheroidizing effect and anti-interference ability are improved. The preparation process is optimized to reduce the burn-off of effective elements and ensure component uniformity, ultimately obtaining a low-rare-earth composite spheroidizing agent with low cost, excellent performance, and wide applicability.

[0007] This invention is implemented as follows:

[0008] An optimized formulation of a low-rare-earth composite spheroidizing agent, wherein the spheroidizing agent is prepared from the following components in parts by mass:

[0009] Magnesium (Mg): 50-75 parts;

[0010] Rare earth elements (RE): 8-15 parts;

[0011] Silicon (Si): 30-40 parts;

[0012] Calcium (Ca): 8-15 parts;

[0013] Barium (Ba): 5-10 parts;

[0014] Zirconium (Zr): 3-6 parts;

[0015] Yttrium (Y): 0.5~1 part;

[0016] Iron and impurities: 1-2 parts.

[0017] Furthermore, the rare earth element (RE) is a composite rare earth of cerium (Ce) and lanthanum (La), and the weight ratio of Ce to La is 2.5~3.5:1.

[0018] The present invention discloses a method for preparing a low rare earth composite spheroidizing agent, the method comprising:

[0019] Step 1: Raw material pretreatment;

[0020] Step 2: Ingredient Mixing; Prepare according to the following mass parts: Magnesium (Mg): 50-75 parts; Rare Earth Elements (RE): 8-15 parts; Silicon (Si): 30-40 parts; Calcium (Ca): 8-15 parts; Barium (Ba): 5-10 parts; Zirconium (Zr): 3-6 parts; Yttrium (Y): 0.5-1 part; Iron and impurities: 1-2 parts, then put them into a high-speed mixer; first mix at a speed of 150-200 r / min for 10-15 min, then increase the speed to 300-350 r / min and continue mixing for 20-25 min to ensure that all components are mixed evenly to obtain a mixed raw material; Compared with the simple mixing in the existing technology, this step adopts segmented speed-controlled mixing, which effectively solves the problem of uneven mixing caused by the difference in component density, and lays the foundation for the uniformity of the subsequent melting reaction.

[0021] Step 3: Vacuum melting;

[0022] Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials; This step further removes impurities and oxide inclusions in the molten liquid by adding a special refining agent, improves the purity of the spheroidizing agent, and solves the problem of unstable spheroidizing effect caused by insufficient purity of existing low rare earth spheroidizing agents.

[0023] Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm.

[0024] Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

[0025] Furthermore, step 1 specifically involves selecting industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingots (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloys (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) as raw materials;

[0026] All raw materials are crushed to a particle size of 2-5mm using precision crushing equipment, and then placed in a drying oven and dried at 120-150℃ for 2-3 hours to remove moisture and oil from the surface of the raw materials and avoid defects such as pores and inclusions during the preparation process. After drying, magnetic separation equipment is used to remove ferromagnetic impurities from the raw materials to ensure the purity of the raw materials.

[0027] Furthermore, step 3 specifically includes:

[0028] The mixed raw materials are fed into a vacuum induction furnace, and the furnace pressure is evacuated to ≤5Pa. Then, the temperature is slowly increased: first, the temperature is increased to 800-900℃ at a rate of 50-80℃ / min and held for 30-40min for preheating and degassing to remove residual gases from the mixed raw materials; then, the temperature is increased to 1550-1650℃ at a rate of 100-120℃ / min and held for 60-80min to completely melt the mixed raw materials. During this process, the mixture is stirred once every 15-20min with a stirring device at a speed of 80-100r / min. Compared with the atmospheric pressure melting in the prior art, the vacuum environment in this invention can significantly reduce the burn-off rate of volatile elements such as magnesium and rare earth elements, and increase the effective element absorption rate to over 85% (most of the prior art is 60-70%), while avoiding the formation of oxide inclusions during the melting process. Detailed Implementation

[0029] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide a more detailed description of the invention. It should be noted that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0030] Example 1

[0031] The preparation method of the low rare earth composite spheroidizing agent in this embodiment is as follows:

[0032] Step 1: Raw material pretreatment; Select industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingot (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloy (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) as raw materials;

[0033] Step 2: Ingredient mixing; Prepare according to the following mass parts: Magnesium (Mg): 70 parts; Rare earth elements (RE): 12 parts; Silicon (Si): 38 parts; Calcium (Ca): 12 parts; Barium (Ba): 7 parts; Zirconium (Zr): 5 parts; Yttrium (Y): 1 part; Iron and impurities: 2 parts. Then put them into a high-speed mixer; first mix at a speed of 150~200 r / min for 10~15 min, then increase the speed to 300~350 r / min and continue mixing for 20~25 min to ensure that all components are mixed evenly to obtain a mixed raw material;

[0034] Step 3: Vacuum melting; The mixed raw materials are fed into a vacuum induction furnace, and the furnace pressure is ≤5Pa. Then the temperature is slowly increased: First, the temperature is increased to 800~900℃ at a rate of 50~80℃ / min, and held for 30~40min for preheating and degassing to remove residual gas from the mixed raw materials; then the temperature is increased to 1550~1650℃ at a rate of 100~120℃ / min, and held for 60~80min to completely melt the mixed raw materials. During this process, the mixture is stirred once every 15~20min using a stirring device at a speed of 80~100r / min.

[0035] Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials;

[0036] Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm.

[0037] Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

[0038] Example 2

[0039] The preparation method of the low rare earth composite spheroidizing agent in this embodiment is as follows:

[0040] Step 1: Raw material pretreatment; Select industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingot (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloy (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) as raw materials;

[0041] Step 2: Ingredient mixing; Prepare according to the following mass parts: Magnesium (Mg): 50 parts; Rare earth elements (RE): 8 parts; Silicon (Si): 30 parts; Calcium (Ca): 8 parts; Barium (Ba): 5 parts; Zirconium (Zr): 3 parts; Yttrium (Y): 0.5 parts; Iron and impurities: 1 part. Then put them into a high-speed mixer; first mix at a speed of 150~200 r / min for 10~15 min, then increase the speed to 300~350 r / min and continue mixing for 20~25 min to ensure that all components are mixed evenly to obtain a mixed raw material;

[0042] Step 3: Vacuum melting; The mixed raw materials are fed into a vacuum induction furnace, and the furnace pressure is ≤5Pa. Then the temperature is slowly increased: First, the temperature is increased to 800~900℃ at a rate of 50~80℃ / min, and held for 30~40min for preheating and degassing to remove residual gas from the mixed raw materials; then the temperature is increased to 1550~1650℃ at a rate of 100~120℃ / min, and held for 60~80min to completely melt the mixed raw materials. During this process, the mixture is stirred once every 15~20min using a stirring device at a speed of 80~100r / min.

[0043] Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials;

[0044] Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm.

[0045] Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

[0046] Example 3

[0047] The preparation method of the low rare earth composite spheroidizing agent in this embodiment is as follows:

[0048] Step 1: Raw material pretreatment; Select industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingot (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloy (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) as raw materials;

[0049] Step 2: Ingredient mixing; Prepare according to the following mass parts: Magnesium (Mg): 75 parts; Rare earth elements (RE): 15 parts; Silicon (Si): 40 parts; Calcium (Ca): 15 parts; Barium (Ba): 10 parts; Zirconium (Zr): 6 parts; Yttrium (Y): 1 part; Iron and impurities: 2 parts. Then put them into a high-speed mixer; first mix at a speed of 150~200 r / min for 10~15 min, then increase the speed to 300~350 r / min and continue mixing for 20~25 min to ensure that all components are mixed evenly to obtain a mixed raw material;

[0050] Step 3: Vacuum melting; The mixed raw materials are fed into a vacuum induction furnace, and the furnace pressure is ≤5Pa. Then the temperature is slowly increased: First, the temperature is increased to 800~900℃ at a rate of 50~80℃ / min, and held for 30~40min for preheating and degassing to remove residual gas from the mixed raw materials; then the temperature is increased to 1550~1650℃ at a rate of 100~120℃ / min, and held for 60~80min to completely melt the mixed raw materials. During this process, the mixture is stirred once every 15~20min using a stirring device at a speed of 80~100r / min.

[0051] Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials;

[0052] Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm.

[0053] Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

[0054] Example 4

[0055] The preparation method of the low rare earth composite spheroidizing agent in this embodiment is as follows:

[0056] Step 1: Raw material pretreatment; Select industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingot (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloy (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) as raw materials;

[0057] Step 2: Ingredient mixing; Prepare according to the following mass parts: Magnesium (Mg): 60 parts; Rare earth elements (RE): 10 parts; Silicon (Si): 38 parts; Calcium (Ca): 10 parts; Barium (Ba): 6 parts; Zirconium (Zr): 5 parts; Yttrium (Y): 0.7 parts; Iron and impurities: 1.5 parts, then put them into a high-speed mixer; first mix at a speed of 150~200 r / min for 10~15 min, then increase the speed to 300~350 r / min and continue mixing for 20~25 min to ensure that all components are mixed evenly to obtain a mixed raw material;

[0058] Step 3: Vacuum melting; The mixed raw materials are fed into a vacuum induction furnace, and the furnace pressure is ≤5Pa. Then the temperature is slowly increased: First, the temperature is increased to 800~900℃ at a rate of 50~80℃ / min, and held for 30~40min for preheating and degassing to remove residual gas from the mixed raw materials; then the temperature is increased to 1550~1650℃ at a rate of 100~120℃ / min, and held for 60~80min to completely melt the mixed raw materials. During this process, the mixture is stirred once every 15~20min using a stirring device at a speed of 80~100r / min.

[0059] Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials;

[0060] Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm.

[0061] Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. An optimized formulation of a low-rare-earth composite spheroidizing agent, characterized in that, The spheroidizing agent is prepared from the following components in parts by weight: Magnesium (Mg): 50-75 parts; Rare earth elements (RE): 8-15 parts; Silicon (Si): 30-40 parts; Calcium (Ca): 8-15 parts; Barium (Ba): 5-10 parts; Zirconium (Zr): 3-6 parts; Yttrium (Y): 0.5~1 part; Iron and impurities: 1-2 parts.

2. The optimized formulation of a low-rare-earth composite spheroidizing agent according to claim 1, characterized in that, The rare earth element (RE) is a composite rare earth of cerium (Ce) and lanthanum (La), and the weight ratio of Ce to La is 2.5~3.5:

1.

3. The preparation method of a low rare earth composite spheroidizing agent according to any one of claims 1 to 2, characterized in that, The method includes: Step 1: Raw material pretreatment; Step 2: Ingredient mixing; Prepare according to the following mass parts: Magnesium (Mg): 50-75 parts; Rare earth elements (RE): 8-15 parts; Silicon (Si): 30-40 parts; Calcium (Ca): 8-15 parts; Barium (Ba): 5-10 parts; Zirconium (Zr): 3-6 parts; Yttrium (Y): 0.5-1 part; Iron and impurities: 1-2 parts. Then put them into a high-speed mixer; first mix at a speed of 150-200 r / min for 10-15 min, then increase the speed to 300-350 r / min and continue mixing for 20-25 min to ensure that all components are mixed evenly to obtain a mixed raw material; Step 3: Vacuum melting; Step 4: Refining treatment; Add a refining agent to the molten liquid, the amount of which is 0.3~0.5% of the total weight of the mixed raw materials; Step 5: Atomization and Cooling Formation; The refined molten spheroidizing agent is introduced into the atomization device through the guide tube. Nitrogen atomization is used with a nitrogen pressure of 0.8~1.2MPa and an atomization temperature of 1400~1500℃ to form fine droplets of molten spheroidizing agent. The droplets are rapidly cooled to room temperature in a nitrogen atmosphere to form spherical particles with a particle size of 0.5~3mm. Step 6: Screening, testing and packaging; The atomized and cooled spherical particles are screened using a vibrating screen to select particles with a diameter of 1~3mm, thus obtaining the finished low rare earth composite spheroidizing agent.

4. The preparation method of a low rare earth composite spheroidizing agent according to claim 3, characterized in that, Step 1 specifically includes: Industrial pure iron with a purity ≥99.5%, industrial ferrosilicon (Si content ≥98%), magnesium ingots (Mg content ≥99.8%), cerium-lanthanum mixed rare earth alloy (Ce content 65~70%, La content 20~25%), metallic calcium (Ca content ≥98%), metallic barium (Ba content ≥98%), metallic zirconium (Zr content ≥99%), and metallic yttrium (Y content ≥99%) were selected as raw materials. All raw materials are crushed to a particle size of 2-5mm using precision crushing equipment, and then placed in a drying oven and dried at 120-150℃ for 2-3 hours to remove moisture and oil from the surface of the raw materials.

5. The preparation method of a low rare earth composite spheroidizing agent according to claim 3, characterized in that, Step 3 specifically includes: The mixed raw materials are fed into a vacuum induction furnace and evacuated until the pressure inside the furnace is ≤5Pa. Then the temperature is slowly increased: first, the temperature is increased to 800~900℃ at a rate of 50~80℃ / min and held for 30~40min for preheating and degassing to remove residual gas from the mixed raw materials; then the temperature is increased to 1550~1650℃ at a rate of 100~120℃ / min and held for 60~80min to completely melt the mixed raw materials. During this period, the mixture is stirred once every 15~20min using a stirring device at a speed of 80~100r / min.