Aluminum alloy casting refiner and its preparation method and application

Abstract

The present invention belongs to the technical field of aluminum alloys, and specifically relates to an aluminum alloy casting refiner, a preparation method and an application thereof. The aluminum alloy casting refiner described in the present invention comprises the following components in mass percentage: 5-10% potassium fluoroborate; 20-30% potassium titanate; 20-30% titanium dioxide; 10-20% potassium titanate whiskers; 20-30% potassium chloride; based on the above mixture as 100%, it also includes 0.15-0.5% calcium fluoride and 3-5% silica sol. The aluminum alloy casting refiner provided by the present invention has good dispersibility and low cost; the aluminum alloy cast by using the refiner of the present invention has improved overall mechanical properties. The present invention also provides a preparation method of the refiner and its application in casting aluminum alloys.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloys, and in particular relates to an aluminum alloy casting refiner and a preparation method and application thereof. Background Art

[0002] Cast aluminum alloys are widely used in the automotive, aerospace and machinery manufacturing fields due to their lightweight, corrosion resistance and good processing performance. However, traditional cast aluminum alloys generally have defects such as coarse grains and pore inclusions, which makes it difficult for key mechanical properties such as tensile strength and elongation to meet the needs of high-end equipment. In the existing technology, although the performance can be partially improved by adding grain refiners and auxiliary fluxes, there are still some technical bottlenecks. Most of the aluminum titanium boron (Al-Ti-B) refiners in the existing technology are in the form of alloys. As the mainstream refiner in the industry, Al-Ti-B achieves grain refinement through a heterogeneous nucleation mechanism, but its TiB2 particles are easy to agglomerate and settle in the melt, resulting in a significant attenuation of the refinement effect with the extension of the insulation time. Especially under slow cooling conditions such as thick-walled castings, the proportion of coarse equiaxed crystals increases by 30%-40%, which seriously weakens the mechanical properties of the material. In addition, the TiAl3 hard and brittle phase generated by the reaction of Ti element and melt is easy to become a source of crack initiation, reducing the fatigue life of castings.

[0003] To make up for the defects of a single refiner, the existing technology mostly adopts a dual-agent combination mode of "refiner + slag remover". After Al-Ti-B refinement, a fluoride-based slag remover is added. Although it can remove oxide slag, it causes the hydrogenation of the melt to reach more than 0.25mL / 100g, and an additional vacuum degassing process is required, which increases the equipment investment by 15%-20%. At the same time, the multi-step process extends the smelting cycle by 40 minutes, and the energy consumption cost increases significantly.

[0004] In the existing technology, rare earth elements such as Ce and La are added to Al-Ti-B to improve the refining effect. Although the tensile strength can be increased by 8%-10%, the cost of rare earth raw materials accounts for more than 60% of the total cost of the refiner. What is more serious is that rare earth oxides form a high-viscosity slag layer on the surface of the melt, which requires special slag removal equipment to clean, resulting in an increase of about 800-1200 yuan in processing costs per ton of castings.

[0005] Therefore, the existing fluoride-based slag removers decompose at high temperatures to produce toxic gases such as HF and SiF4, and require an exhaust gas treatment system, which increases environmental management costs. Although sodium-based refiners are more environmentally friendly, they are prone to cause sodium embrittlement in the melt, causing the elongation of castings to drop by more than 35%, and have a narrow process window (temperature control accuracy must be ≤±5℃), which restricts large-scale industrial applications. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide an aluminum alloy casting refiner with good dispersibility and low cost; the aluminum alloy cast by using the refiner of the present invention has improved overall mechanical properties. The present invention also provides a preparation method of the refiner.

[0007] The aluminum alloy casting refiner of the present invention comprises the following components in percentage by mass:

[0008] Potassium fluoroborate 5-10%;

[0009] Potassium titanate 20-30%;

[0010] Titanium dioxide 20-30%;

[0011] Potassium titanate whiskers 10-20%;

[0012] Potassium chloride 20-30%;

[0013] Taking the total mass of the potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whiskers and potassium chloride as 100%, the present invention further comprises 0.15-0.5% of the total mass of calcium fluoride and 3-5% of the total mass of silica sol.

[0014] Potassium fluoroborate 5-10%: Removes oxides from aluminum liquid through decomposition reaction, effectively removes iron elements in aluminum alloy, thereby improving the purity of aluminum alloy, helping to improve the mechanical properties of the alloy, especially strength and toughness; improves the fluidity of aluminum alloy, facilitates mold filling during the casting process, and reduces defects.

[0015] Potassium titanate 20-30%: absorbs harmful gases and moisture in aluminum liquid, enhances the mechanical properties of aluminum products such as hardness and impact resistance; improves the strength of aluminum alloy and refines grains, generates TiAl3 compounds with aluminum to improve the strength and hardness of aluminum alloy, refines grains and reduces porosity during smelting, improves the mechanical properties and density of the alloy, and improves the corrosion resistance and oxidation resistance of the alloy.

[0016] Titanium dioxide 20-30%: Coarsens the grains of the alloy, improves the microstructure, acts as a heterogeneous nucleus core during solidification, promotes the formation of crystal nuclei, refines the grains, prevents the formation of thermal cracks, effectively improves the tensile properties and hardness of the alloy, and at the same time improves the ductility of the alloy, improves the suspension of the refiner, and floats the impurities in the aluminum liquid above the aluminum liquid for easy cleaning.

[0017] Potassium titanate whiskers 10-20%: Improve the fatigue resistance and wear resistance of aluminum alloys, generate α-Al2O3 and TiAl3 as well as γ-Al2O3 with aluminum, and after treatment, the whiskers react with the aluminum matrix to generate TiO2 at the interface; the addition of whiskers changes the solidification process of aluminum alloys, refines the grain structure, and at the same time produces numerous interfaces between grain boundaries and the matrix inside the material. These interfaces hinder the movement of dislocations and cause dislocation accumulation, thereby improving the performance of the material.

[0018] Potassium chloride 20-30%: reduces the melting point of aluminum alloy, removes oxides and impurities in aluminum alloy, improves the purity of aluminum liquid, reduces the formation of pores and inclusions, improves the quality of castings; improves the fluidity of aluminum liquid to facilitate filling.

[0019] The initial particle sizes of potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whisker and potassium chloride are as follows: potassium fluoroborate particle size is 16-50 μm; potassium titanate particle size is 15-50 μm; titanium dioxide particle size is 30-45 μm; potassium titanate whisker particle size is 20-40 μm; potassium chloride particle size is 20-40 μm.

[0020] The preparation method of the aluminum alloy casting refiner comprises the following preparation method:

[0021] (1) Ball-milling potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whiskers, and potassium chloride, respectively, and sieving;

[0022] (2) Mix the materials, heat and stir to obtain mixed powder;

[0023] (3) Inoculation treatment: Add calcium fluoride to the mixed powder, heat and stir to inoculate;

[0024] (4) Granulation: Add silica sol to the prepared mixed powder, granulate, screen, test and package to obtain the refiner.

[0025] Step (1) The particle size of potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whisker and potassium chloride after ball milling and screening is 0.5-1 μm.

[0026] In step (2), the temperature is raised to 70-90°C, and the mixture is stirred at a forward and reverse speed of 80-120 r / min for 90-140 minutes. Through orthogonal experiments, it is found that when the temperature in step (2) is lower than 70°C, the mixing uniformity decreases; when it is higher than 90°C, potassium chloride is prone to moisture absorption and agglomeration.

[0027] Step (3) The temperature is raised to 210-230° C., and the mixture is stirred at a forward and reverse speed of 80-120 r / min for 50-80 min.

[0028] In step (4), the stirring speed of the granulation is 300-400 r / min, the granulation temperature is 170-190° C., the discharge pressure is 0.15-0.25 MPa, and the particle size after screening is controlled to be 5.5-6.5 mm.

[0029] The application of the aluminum alloy casting refiner comprises the following steps:

[0030] (1) heating the aluminum ingot to 720-740°C and melting it to obtain an aluminum alloy melt;

[0031] (2) The aluminum alloy melt is heated to 750-770°C, high-purity argon is introduced, the rotor speed is set to 440-460 r / min, and after vortexing for 2-4 minutes, the prepared refiner is added, and the refining, degassing and slag removal are performed;

[0032] (3) Casting the slag-removed aluminum alloy melt into an aluminum alloy product blank by low-pressure casting;

[0033] (4) The aluminum alloy product blank is subjected to surface treatment, heat treatment, precision machining and cleaning to obtain a finished aluminum alloy.

[0034] The mass of the refiner added in step (2) is 0.03% to 0.07% of the aluminum alloy melt.

[0035] The pressure of the low pressure casting in step (3) is 0.2-0.4 MPa.

[0036] The solution temperature in the heat treatment of step (4) is 535-545°C, and the heat preservation time is 7-9 hours. The aging temperature is 175-185°C, and the heat preservation time is 9-11 hours.

[0037] Specifically, the preparation method of the aluminum alloy casting refiner includes the following preparation method:

[0038] (1) 5-10% potassium fluoroborate, 20-30% potassium titanate, 20-30% titanium dioxide, 10-20% potassium titanate whiskers, and 20-30% potassium chloride are placed in a ball mill respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0039] (2) Mix the materials, raise the temperature to 70-90°C, stir at a forward and reverse speed of 80-120 r / min, and mix for 90-140 minutes to obtain a mixed powder;

[0040] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.15-0.5% calcium fluoride based on the mass of the mixed powder, heat to 210-230°C, stir at a forward and reverse speed of 80-120 r / min, mix for 50-80 minutes, and inoculate;

[0041] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 3% to 5% silica sol based on the mass of the mixed powder, granulate, stir at a speed of 300 to 400 r / min, a granulation temperature of 170 to 190 °C, a discharge pressure of 0.15 to 0.25 MPa, and control the sieve particle size to 5.5 to 6.5 mm. Detect and package to obtain the refiner.

[0042] Specifically, the application of the aluminum alloy casting refiner comprises the following steps:

[0043] (1) Heating the A356 aluminum ingot to 720-740°C and melting it to obtain an aluminum alloy melt;

[0044] (2) The aluminum alloy melt is heated to 750-770°C, and high-purity argon is introduced for refining and degassing. The rotor speed is set to 440-460 r / min. After vortexing for 2-4 minutes, the prepared 0.03%-0.07% refiner is added. After 6 minutes, the baffle is lowered, and the refining and degassing are performed for 20 minutes, and slag is removed.

[0045] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by low-pressure casting at 0.2-0.4 MPa;

[0046] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 535-545°C and a heat preservation temperature of 7-9 hours, an aging temperature of 175-185°C and a heat preservation temperature of 9-11 hours, and precision machining and cleaning to obtain a finished aluminum alloy.

[0047] The preparation of traditional Al-Ti-B refiners relies on fluorine-containing salts (such as K2TiF6, KBF4), which release a large amount of toxic gases such as KF and AlF3 during the reaction, and residual salt inclusions pollute alloy 1115. The present invention uses a composite salt system of potassium fluoroborate and potassium chloride combined with inoculation treatment (adding calcium fluoride) to reduce the generation of harmful gases by optimizing the salt reaction path; at the same time, silica sol granulation technology is used to replace the traditional molten salt reaction to avoid the problem of molten salt inclusion residues. In addition, the preparation process uses low-temperature mixing and granulation, without the need for high-temperature smelting or inert gas protection, which reduces energy consumption and equipment complexity and is more suitable for industrial continuous production needs. Existing Al-Ti-B refiners are easily affected by silicon poisoning or high-temperature decay, especially in aluminum-silicon alloys, where the refinement effect is unstable. The present invention forms highly active nucleation particles such as TiB2 and TiAl3 by composite addition of potassium titanate whiskers and titanium dioxide, and optimizes the dispersion of particles through inoculation treatment to improve the nucleation efficiency. In addition, the particle size of the refiner after granulation is uniform (5.5~6.5mm), combined with the low-pressure casting process (0.2~0.4MPa), to ensure that the refiner is quickly dissolved and evenly distributed in the melt, slowing down the sedimentation rate, thereby extending the durability of the refinement effect. Experimental data show that adding only 0.03~0.07% can significantly refine the grains, and subsequent heat treatment (solid solution + aging) further stabilizes the structure and avoids secondary coarsening.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The preparation method of the aluminum alloy casting refiner of the present invention reduces pollution emissions, simplifies the preparation process, and reduces energy consumption.

[0050] (2) The aluminum alloy casting refiner of the present invention is added to the casting of aluminum alloy to replace aluminum titanium boron and slag remover, and has good effect. The tensile strength, elongation and hardness are all improved, and the overall mechanical properties are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is the metallographic phase diagram of the aluminum alloy prepared in Example 5.

[0052] Figure 2 This is the metallographic phase diagram of the aluminum alloy prepared in Example 7.

[0053] Figure 3 This is the metallographic image of the aluminum alloy prepared in Comparative Example 1.

[0054] Figure 4 This is the metallographic image of the aluminum alloy prepared in Comparative Example 2. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with specific embodiments.

[0056] The raw materials and additives used in the following examples and comparative examples are all commercially available products.

[0057] The following commercially available raw materials are: potassium fluoroborate with a particle size of 16 to 50 μm; potassium titanate with a particle size of 15 to 50 μm; titanium dioxide with a particle size of 30 to 45 μm; potassium titanate whisker with a particle size of 20 to 40 μm; and potassium chloride with a particle size of 20 to 40 μm. The mixed material is composed of potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whisker and potassium chloride, and the total mass thereof is 100%.

[0058] The following % are all based on 100kg.

[0059] Example 1

[0060] The preparation method of the aluminum alloy casting refiner comprises the following preparation method:

[0061] (1) 10% potassium fluoroborate, 30% potassium titanate, 25% titanium dioxide, 15% potassium titanate whiskers, and 20% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0062] (2) Mix all materials, heat to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0063] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.2% calcium fluoride based on the mass of the mixed powder, heat to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0064] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled at 6 mm, and the fineness agent A is obtained after testing and packaging.

[0065] Example 2

[0066] The preparation method of the aluminum alloy casting refiner comprises the following preparation method:

[0067] (1) 5% potassium fluoroborate, 30% potassium titanate, 30% titanium dioxide, 10% potassium titanate whisker, and 25% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0068] (2) Mix all materials, raise the temperature to 70°C, stir at a forward and reverse speed of 80 r / min, and mix for 90 minutes to obtain a mixed powder;

[0069] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.15% calcium fluoride by weight of the mixed powder, heat to 230°C, stir at 120r / min, mix for 50 minutes, and inoculate;

[0070] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 3% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 300 r / min, the granulation temperature is 170°C, the discharge pressure is 0.15 MPa, the sieve particle size is controlled at 6.5 mm, and the fineness agent B is obtained after testing and packaging.

[0071] Example 3

[0072] The preparation method of the aluminum alloy casting refiner comprises the following preparation method:

[0073] (1) 10% potassium fluoroborate, 20% potassium titanate, 20% titanium dioxide, 20% potassium titanate whiskers, and 30% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0074] (2) Mix all materials, heat to 90°C, stir at a forward and reverse speed of 120 r / min, and mix for 140 min to obtain a mixed powder;

[0075] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.5% calcium fluoride by weight of the mixed powder, heat to 210°C, stir at 80r / min, mix for 80 minutes, and inoculate;

[0076] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 5% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 400 r / min, the granulation temperature is 190°C, the discharge pressure is 0.25 MPa, the sieve particle size is controlled at 5.5 mm, and the fineness agent C is obtained after testing and packaging.

[0077] Example 4

[0078] The application of the aluminum alloy casting refiner comprises the following steps:

[0079] (1) Heating the A356 aluminum ingot to 730°C and melting it to obtain an aluminum alloy melt;

[0080] (2) The aluminum alloy melt was heated to 760° C., and high-purity argon was introduced for refining and degassing. The rotor speed was set to 450 r / min. After vortexing for 3 minutes, 0.03% of the refiner A prepared in Example 1 was added. After 6 minutes, the baffle was lowered, and the refining and degassing were carried out for 20 minutes, and slag was removed.

[0081] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.3 MPa low-pressure casting;

[0082] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 540°C and a heat preservation temperature of 8 h, an aging temperature of 180°C and a heat preservation temperature of 10 h, and precision machining and cleaning to obtain a finished aluminum alloy.

[0083] Example 5

[0084] The application of the aluminum alloy casting refiner comprises the following steps:

[0085] (1) Heating the A356 aluminum ingot to 720°C and melting it to obtain an aluminum alloy melt;

[0086] (2) The aluminum alloy melt was heated to 750° C., and high-purity argon gas was introduced for refining and degassing. The rotor speed was set to 440 r / min. After vortexing for 2 minutes, 0.04% of the refiner A prepared in Example 1 was added. After 6 minutes, the baffle was lowered, and the refining and degassing were carried out for 20 minutes, and slag was removed.

[0087] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.3 MPa low-pressure casting;

[0088] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 540°C and a heat preservation temperature of 8 h, an aging temperature of 175°C and a heat preservation temperature of 11 h, and precision machining and cleaning to obtain a finished aluminum alloy.

[0089] Example 6

[0090] The application of the aluminum alloy casting refiner comprises the following steps:

[0091] (1) Heating the A356 aluminum ingot to 740°C and melting it to obtain an aluminum alloy melt;

[0092] (2) The aluminum alloy melt was heated to 770° C., and high-purity argon was introduced for refining and degassing. The rotor speed was set at 460 r / min. After vortexing for 4 minutes, 0.05% of the refiner A prepared in Example 1 was added. After 6 minutes, the baffle was lowered, and the refining and degassing were carried out for 20 minutes, and slag was removed.

[0093] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.4 MPa low-pressure casting;

[0094] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 535°C and a heat preservation temperature of 9 hours, an aging temperature of 175°C and a heat preservation temperature of 11 hours, and precision machining and cleaning to obtain a finished aluminum alloy.

[0095] Example 7

[0096] The application of the aluminum alloy casting refiner comprises the following steps:

[0097] (1) Heating the A356 aluminum ingot to 730°C and melting it to obtain an aluminum alloy melt;

[0098] (2) The aluminum alloy melt was heated to 760° C., and high-purity argon was introduced for refining and degassing. The rotor speed was set to 450 r / min. After vortexing for 3 minutes, 0.06% of the refiner B prepared in Example 2 was added. After 6 minutes, the baffle was lowered, and the refining and degassing were carried out for 20 minutes, and slag was removed.

[0099] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.4 MPa low-pressure casting;

[0100] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 545°C and a heat preservation temperature of 7 h, an aging temperature of 180°C and a heat preservation temperature of 10 h, and precision machining and cleaning to obtain a finished aluminum alloy.

[0101] Example 8

[0102] The application of the aluminum alloy casting refiner comprises the following steps:

[0103] (1) Heating the A356 aluminum ingot to 730°C and melting it to obtain an aluminum alloy melt;

[0104] (2) The aluminum alloy melt was heated to 760° C., and high-purity argon was introduced for refining and degassing. The rotor speed was set to 450 r / min. After vortexing for 3 minutes, 0.07% of the refiner C prepared in Example 3 was added. After 6 minutes, the baffle was lowered, and the refining and degassing were carried out for 20 minutes, and slag was removed.

[0105] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.2 MPa low-pressure casting;

[0106] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 540°C and a heat preservation temperature of 8 h, an aging temperature of 180°C and a heat preservation temperature of 10 h, and precision machining and cleaning to obtain a finished aluminum alloy.

[0107] The aluminum alloys of Examples 4 to 8 above are tested according to GB / T1173-2013, and their raw material composition is shown in Table 1.

[0108] Table 1 Raw material mass composition of Examples 4-8

[0109]

[0110] Comparative Example 1

[0111] This comparative example is the same as Example 4, except that the refiner A is removed and conventional commercially available aluminum-titanium-boron refiner and slag remover are used. The specific steps are as follows:

[0112] (1) Heating the A356 aluminum ingot to 730°C and melting it to obtain an aluminum alloy melt;

[0113] (2) The aluminum alloy melt was heated to 760°C, and high-purity argon was introduced for refining and degassing. The rotor speed was set to 450 r / min. After vortexing for 3 minutes, 0.15% AlTi5B1 alloy was added. After 6 minutes, the baffle was lowered, and 0.1% of the slag remover HM2510 by weight of the aluminum alloy was sprinkled in to cover. The mixture was refined and degassed for 20 minutes, and slag was removed.

[0114] (3) Casting the slag-removed aluminum alloy molten metal into an aluminum alloy product blank by 0.3 MPa low-pressure casting;

[0115] (4) The aluminum alloy product blank is subjected to surface treatment and heat treatment, with a solution temperature of 540°C and a heat preservation temperature of 8 h, an aging temperature of 180°C and a heat preservation temperature of 10 h, and precision machining and cleaning to obtain a finished aluminum alloy.

[0116] Comparative Example 2

[0117] A method for preparing an aluminum alloy casting refiner comprises the following preparation methods:

[0118] (1) 10% potassium fluoroborate, 45% potassium titanate, 25% titanium dioxide, and 20% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0119] (2) Mix all materials, raise the temperature to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0120] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.2% calcium fluoride based on the mass of the mixed powder, heat to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0121] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled at 6 mm, and the fineness agent D is obtained after testing and packaging.

[0122] The refiner D prepared above was used to cast aluminum alloy according to the steps of casting aluminum alloy in Example 4. Comparative Example 2 did not add potassium titanate whiskers, resulting in a significant decrease in grain refining effect.

[0123] Comparative Example 3

[0124] A method for preparing an aluminum alloy casting refiner comprises the following preparation methods:

[0125] (1) 40% potassium fluoroborate, 25% titanium dioxide, 15% potassium titanate whiskers, and 20% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0126] (2) Mix all materials, heat to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0127] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.2% calcium fluoride based on the mass of the mixed powder, heat to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0128] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled at 6 mm, test, and package to obtain refiner E.

[0129] The refiner E prepared above was used to cast aluminum alloy according to the steps of casting aluminum alloy in Example 4.

[0130] Comparative Example 4

[0131] A method for preparing an aluminum alloy casting refiner comprises the following preparation methods:

[0132] (1) 25% potassium titanate, 30% titanium dioxide, 20% potassium titanate whiskers, and 25% potassium chloride are placed in a ball mill respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0133] (2) Mix all materials, heat to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0134] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.2% calcium fluoride based on the mass of the mixed powder, heat to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0135] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled to 6 mm, test, and package to obtain refiner F.

[0136] The refiner F prepared above was used to cast aluminum alloy according to the steps of casting aluminum alloy in Example 4.

[0137] Comparative Example 5

[0138] This comparative example is the same as Example 1, but the 0.2% calcium fluoride in step (3) is removed. The specific steps are as follows:

[0139] (1) 10% potassium fluoroborate, 30% potassium titanate, 25% titanium dioxide, 15% potassium titanate whiskers, and 20% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0140] (2) Mix all materials, heat to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0141] (3) Inoculation treatment: Add the mixed powder into the reaction tank, heat it to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0142] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% silica sol based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled at 6 mm, and the fineness agent G is obtained after testing and packaging.

[0143] The refiner G prepared above was used to cast aluminum alloy according to the steps of casting aluminum alloy in Example 4.

[0144] Comparative Example 6

[0145] This comparative example is the same as Example 1, but the 4% silica sol in step (4) is replaced by 4% water glass. The specific steps are as follows:

[0146] (1) 10% potassium fluoroborate, 30% potassium titanate, 25% titanium dioxide, 15% potassium titanate whiskers, and 20% potassium chloride are placed in a ball mill jar, respectively, and ball milled with a ball mill. After sieving, the particle size is 0.5-1 μm;

[0147] (2) Mix all materials, heat to 80°C and stir, stir at a forward and reverse speed of 100 r / min, mix for 100 min, and obtain mixed powder;

[0148] (3) Inoculation treatment: Add the mixed powder into the reaction tank, then add 0.2% calcium fluoride based on the mass of the mixed powder, heat to 220°C, stir at a forward and reverse speed of 100 r / min, mix for 60 minutes, and inoculate;

[0149] (4) Granulation: Place the inoculated mixed powder in a strong mixing granulator, add 4% water glass based on the mass of the mixed powder, and granulate. The stirring speed is 350 r / min, the granulation temperature is 180°C, the discharge pressure is 0.2 MPa, the sieve particle size is controlled to 6 mm, test, and package to obtain the refiner H.

[0150] The refiner H prepared above was used to cast aluminum alloy according to the steps of casting aluminum alloy in Example 4.

[0151] The raw material composition table of the aluminum alloys of the above comparative examples 1-6 is shown in Table 2 according to GB / T1173-2013.

[0152] Table 2 Raw material mass components of comparative examples 1-6

[0153]

[0154] The properties of the aluminum alloys cast in the above embodiments and comparative examples were measured according to GB / T1173-2013, GB / T9438-2013, GB / T25745-2010 and GB / T228.1-2021. The test results are shown in Table 3.

[0155] Table 3 Test results

[0156]

[0157] The aluminum alloy of Example 4-8 is refined by adding the refiner prepared by the present invention during melting, and has a dense structure, a tensile strength higher than 329 MPa, an elongation value of more than 11.9%, a hardness value of more than 98, and stable comprehensive performance.

[0158] The aluminum alloy materials of Comparative Examples 1-6, Comparative Example 1 did not add a particle refiner, but used ordinary aluminum titanium boron and slag remover. The refiner components in Comparative Examples 2-6 were changed, and the tensile strength was lower than 298MPa, the elongation value was lower than 6, and the hardness value was lower than 100. The comprehensive performance was not high. It can be seen that each component is indispensable, and each component needs to exert its own performance to achieve the effect.

[0159] Metallographic examination was performed on Example 5, Example 7, Comparative Example 1 and Comparative Example 2. The test results are as follows: Figure 1-4 shown.

[0160] Metallographic analysis shows that after the particle refinement and metamorphism of the present invention, the eutectic Si grows into a round or spherical shape and is evenly distributed, which hinders the growth of silicon crystals, increases silicon crystallization, increases the nucleation rate, refines the structure, and significantly changes the α-Al matrix. However, the eutectic Si structure in the alloy with the addition of aluminum-titanium-boron refiner is coarse flake or coarse needle-like, which seriously splits the matrix and reduces the strength and plasticity of the alloy. There is a large gap in the metamorphism effect, and the α-Al matrix has not changed significantly. Metallographic comparison shows that the advantages of the present invention are quite obvious; after heat treatment, higher strength and hardness can be achieved, and the elongation is higher, which has a significant strengthening effect on the Al matrix.

Claims

1. A method for preparing an aluminum alloy casting refiner, characterized in that: The invention comprises the following preparation methods: (1) Ball-milling potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whiskers, and potassium chloride, respectively, and sieving; (2) Mix the materials, raise the temperature to 70-90°C and stir to obtain a mixed powder; (3) Inoculation treatment: Add calcium fluoride to the mixed powder, raise the temperature to 210-230°C and stir to inoculate; (4) Granulation: Add silica sol to the inoculated mixed powder, granulate, screen, test, and package to obtain a refiner; The aluminum alloy casting refiner comprises the following raw material components in percentage by mass: Potassium fluoroborate 5-10%; Potassium titanate 20-30%; Titanium dioxide 20-30%; Potassium titanate whiskers 10-20%; Potassium chloride 20-30%; Taking the total mass of the potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whiskers and potassium chloride as 100%, the present invention further comprises 0.15-0.5% of the total mass of calcium fluoride and 3-5% of the total mass of silica sol.

2. The method for preparing an aluminum alloy casting refiner according to claim 1, characterized in that: Step (1) The particle size of potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whisker and potassium chloride after ball milling and screening is 0.5-1 μm.

3. The method for preparing an aluminum alloy casting refiner according to claim 1, characterized in that: In step (2), the mixture is stirred at a forward and reverse speed of 80 to 120 r / min and mixed for 90 to 140 minutes.

4. The method for preparing an aluminum alloy casting refiner according to claim 1, characterized in that: In step (3), the temperature is raised and the mixture is stirred at a forward and reverse speed of 80 to 120 r / min for 50 to 80 minutes.

5. The method for preparing an aluminum alloy casting refiner according to claim 1, characterized in that: In step (4), the stirring speed of the granulation is 300-400 r / min, the granulation temperature is 170-190° C., the discharge pressure is 0.15-0.25 MPa, and the particle size after screening is controlled to be 5.5-6.5 mm.

6. The method for preparing an aluminum alloy casting refiner according to claim 1, characterized in that: The initial particle sizes of potassium fluoroborate, potassium titanate, titanium dioxide, potassium titanate whisker and potassium chloride are as follows: potassium fluoroborate particle size is 16-50 μm; potassium titanate particle size is 15-50 μm; titanium dioxide particle size is 30-45 μm; potassium titanate whisker particle size is 20-40 μm; potassium chloride particle size is 20-40 μm.

7. Use of a refiner prepared by the method for preparing an aluminum alloy casting refiner according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) heating the aluminum ingot to 720-740°C and melting it to obtain an aluminum alloy melt; (2) The aluminum alloy melt is heated to 750-770°C, high-purity argon is introduced, the rotor speed is set to 440-460 r / min, and after vortexing for 2-4 minutes, the prepared refiner is added, and the refining, degassing and slag removal are performed; (3) Casting the slag-removed aluminum alloy melt into an aluminum alloy product blank by low-pressure casting; (4) The aluminum alloy product blank is subjected to surface treatment, heat treatment, precision machining and cleaning to obtain a finished aluminum alloy.

8. The use of the refiner prepared by the method for preparing the refiner for aluminum alloy casting according to claim 7, characterized in that: The mass of the refiner added in step (2) is 0.03% to 0.07% of the mass of the aluminum alloy melt, and the pressure of the low-pressure casting in step (3) is 0.2 to 0.4 MPa.

9. The use of the refiner prepared by the method for preparing the refiner for aluminum alloy casting according to claim 7, characterized in that: The solution temperature in the heat treatment of step (4) is 535-545°C, and the heat preservation time is 7-9 hours. The aging temperature is 175-185°C, and the heat preservation time is 9-11 hours.

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