Modification and grain refiner for Al-Si series die-casting aluminum alloy and preparation method thereof

Abstract

The invention discloses a modification and grain refiner for Al-Si series die-casting aluminum alloy, which comprises the following components in mass percentage: 60-80% of rare earth aluminum alloy powder, 19-39% of auxiliary agent A, and 0.1-1.0% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth elements account for 2-20% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the rare earth element is any one or a combination of two of La, Ce, Y, Er, and Sc; the auxiliary agent A comprises light calcium carbonate, sodium cryolite, potassium cryolite, sodium fluorosilicate, lithium fluoride, potassium fluoride, sodium fluoride, aluminum fluoride, sodium chloride, potassium chloride, potassium fluoroborate, magnesium chloride, and hexachloroethane; the auxiliary agent B comprises polyethylene glycol and stearamide. The modification and grain refiner obtained by mixing rare earth aluminum alloy powder, additive A and additive B can be evenly dispersed in the aluminum alloy melt to play the role of long-term modification and grain refinement as well as refining and dehydrogenation.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy smelting, and in particular relates to a modification and grain refiner for Al-Si series die-casting aluminum alloy and a preparation method thereof. Background Art

[0002] In the casting process of Al-Si cast aluminum alloys, strontium (Sr) is usually used to modify eutectic silicon (Si). Adding a certain amount of aluminum-strontium master alloy (Al-Sr10) during the smelting process before casting Al-Si cast aluminum alloys can transform the needle-shaped coarse eutectic silicon (Si) phase in the alloy into a fine fibrous form, which is beneficial to improve the strength, plasticity and toughness of the alloy. However, the modification effect of strontium on Al-Si cast aluminum alloys gradually decays with time, and strontium does not have the effect of refining the aluminum alloy matrix grains. In the die-casting production process, the aluminum alloy melt usually stays in the furnace for a long time. Using strontium (Sr) for modification will cause the mechanical properties of the same batch of castings to fluctuate greatly.

[0003] Research results show that rare earth elements, such as lanthanum (La), cerium (Ce), erbium (Er), yttrium (Y), scandium (Sc), etc., not only have the effect of refining aluminum alloy grains, but also have the effect of improving and refining the morphology of eutectic silicon (Si). This is because these rare earth elements can form a class of intermetallic compounds with Al elements in the aluminum alloy system, such as Al3Sc, Al3Y, Al3Er, Al 11 La3、Al 11 Ce3, etc. These intermetallic compounds can serve as the nucleation core of α-Al during the solidification process of aluminum alloy, promote the nucleation rate of α-Al grains, and finally achieve the effect of grain refinement. In addition, the research results show that a certain amount of rare earth elements can be enriched at the "solid-liquid" interface between eutectic silicon (Si) and aluminum melt during the solidification process of Al-Si die-cast aluminum alloy, hindering the growth of Si along a special crystal direction to a certain extent, achieving the effect of refining and improving the morphology of eutectic Si. However, in the actual large-scale production process, it is very difficult to add rare earth elements and make them evenly dispersed in the aluminum alloy system. The rare earth oxides or rare earth carbonates added now are difficult to quickly and evenly enter the aluminum alloy melt under the aluminum alloy melting temperature conditions, resulting in low utilization and absorption rates of rare earth elements and uneven quality of aluminum alloy products. Summary of the invention

[0004] In view of the above-mentioned deficiency that rare earth elements cannot be evenly dispersed in the aluminum alloy melt, the present invention discloses a modification and grain refiner for Al-Si series die-casting aluminum alloy and a preparation method thereof, which can evenly disperse the rare earth elements in the aluminum alloy melt, play the role of modifying the eutectic silicon and refining the grains in the Al-Si series die-casting aluminum alloy, and has the characteristics of long-term stability, and also has the functions of refining and dehydrogenation, and is very suitable for the production of die-casting aluminum alloy parts.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in percentage by mass: 60-80% rare earth aluminum alloy powder, 19-39% auxiliary agent A, and 19-39% auxiliary agent B. 0.1-1.0%; in the rare earth aluminum alloy powder, rare earth elements account for 2-20% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the rare earth element is any one or a combination of two of La, Ce, Y, Er, and Sc; the auxiliary agent A includes the following components in mass percentage: light calcium carbonate 1-5%, sodium cryolite 5-10%, potassium cryolite 5-10%, sodium fluorosilicate 3-6%, lithium fluoride 3-8%, potassium fluoride 1-4%, sodium fluoride 10-15%, aluminum fluoride 3-9%, sodium chloride 15-20%, potassium chloride 15-20%, potassium fluoroborate 5-8%, magnesium chloride 2-4%, and hexachloroethane 10-30%; the auxiliary agent B includes the following components in mass percentage: polyethylene glycol 40-50%, and stearamide 50-60%.

[0007] The present invention uses rare earth aluminum alloy powder to achieve long-term modification of Al-Si die-cast aluminum alloy, specifically, using atoms of rare earth elements, such as La, Ce, Er, Y, and Sc, to be enriched on the surface of eutectic Si phase during the solidification process of Al-Si alloy melt, hindering the rapid growth of Si phase along certain specific directions, thereby transforming the original needle-like Si phase into a fibrous or small block shape, thereby achieving a modification effect. At the same time, the present invention uses an auxiliary agent A prepared by light calcium carbonate, sodium cryolite, potassium cryolite, sodium fluorosilicate, lithium fluoride, potassium fluoride, sodium fluoride, aluminum fluoride, sodium chloride, potassium chloride, potassium fluoroborate, magnesium chloride, hexachloroethane, etc., and uses an auxiliary agent B prepared by polyethylene glycol, stearamide, etc., and the auxiliary agent A and the auxiliary agent B synergistically act with the rare earth aluminum alloy powder to obtain better modification and grain refinement effects. The light calcium carbonate in the auxiliary agent A plays the role of skeleton support; sodium cryolite, potassium cryolite, lithium fluoride, potassium fluoride, sodium fluoride, aluminum fluoride and other fluorides can effectively dissolve and adsorb the oxide inclusions in the aluminum alloy melt; sodium fluorosilicate, sodium chloride, potassium chloride, potassium fluoroborate and magnesium chloride can promote the dissolution of rare earth aluminum alloy powder on the one hand, and on the other hand, because the rare earth aluminum alloy powder is relatively active, it can protect the rare earth aluminum alloy powder and reduce its burning loss; and the hexachloroethane quantitatively added in the present invention can be decomposed into carbon dioxide and hydrogen chloride gas under high temperature conditions to degas and remove impurities for the melt, and play the role of refining and purifying the melt. The present invention adopts polyethylene glycol and stearamide to compound in proportion to obtain auxiliary agent B, through their synergistic effect, it can not only play a bonding role, so as to help keep the block shape not easy to loose after pressing and molding, but also can lubricate the inner wall of the pressing mold, so as to facilitate smooth demoulding after pressing and molding.

[0008] Furthermore, the quality change and grain refinement agent comprises the following components in percentage by mass: rare earth aluminum alloy powder 70-80%, additive A 20-29.6%, additive B 0.2-0.4%; in the rare earth aluminum alloy powder, rare earth elements account for 2-15% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the rare earth element is any one or a combination of two of La, Ce, Y, Er, and Sc; the auxiliary agent A includes the following components in mass percentage: light calcium carbonate 2-4%, sodium cryolite 5-7%, potassium cryolite 5-7%, sodium fluorosilicate 3-5%, lithium fluoride 3-6%, potassium fluoride 1-3%, sodium fluoride 10-13%, aluminum fluoride 3-5%, sodium chloride 15-18%, potassium chloride 15-18%, potassium fluoroborate 5-6%, magnesium chloride 2-3%, and hexachloroethane 15-25%; the auxiliary agent B includes the following components in mass percentage: polyethylene glycol 40-45%, and stearamide 55-60%.

[0009] Furthermore, the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0010] The above-mentioned method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy comprises the following steps:

[0011] (1) Weigh rare earth compounds, flux and aluminum ingots in proportion, first charge the aluminum ingots into a furnace and heat them to 850°C to 1250°C to obtain a melt, add rare earth compounds and flux to the melt A for smelting, continue to stir the melt A, and keep it warm for 1 to 1.5 hours, then introduce 99.99% high-purity argon gas into the melt A for refining for 20 to 30 minutes, the flow rate of the argon gas is 4 to 10 m / s 3 / h, after refining, the slag is removed and allowed to stand for 15 to 20 minutes, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is any one or a combination of two of lanthanum oxide, cerium oxide, yttrium fluoride, erbium fluoride, and scandium fluoride; the flux comprises the following components in mass percentage: NaF 10 to 20%, NaCl 20 to 35%, KCl 35 to 50%, and cryolite 5 to 10%; the mass ratio of the aluminum ingot to the flux is (4 to 5):1;

[0012] The synergistic effect of NaF and cryolite can effectively dissolve rare earth oxides and fluorides, and NaCl and KCl are used to adjust the melting temperature of the solvent so that it has a melting temperature that matches the reaction temperature during the process, so as to control the volatilization of the molten salt solvent;

[0013] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 760°C to 900°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1 to 1.5 hours, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 2.0 to 5.0 MPa, and the atomization gas flow rate is 5 to 15 Nm 3 / min;

[0014] (3) The rare earth aluminum alloy powder, additive A and additive B obtained in step (2) are placed in a mixer to mix to obtain a mixture, and then the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0015] The invention melts a rare earth compound, a flux and an aluminum ingot together to obtain a rare earth aluminum alloy ingot, then melts the rare earth aluminum alloy ingot and atomizes and pulverizes it under suitable conditions to obtain a rare earth aluminum alloy powder, finally mixes the rare earth aluminum alloy powder with an auxiliary agent A composed of multiple salts, adds a small amount of an auxiliary agent B composed of a binder and a lubricant, and presses it into a relatively dense modification and grain refiner with a certain shape, which can be evenly dispersed in the aluminum alloy melt, thereby improving the dispersibility and absorption rate of the rare earth element in the aluminum alloy melt, giving full play to the role of the rare earth element in refining the aluminum alloy grains and improving and refining the morphology of eutectic silicon, and having the effects of modification, grain refinement and melt refining at the same time.

[0016] Furthermore, the casting temperature in step (1) is 850°C to 900°C.

[0017] Furthermore, in step (1), rare earth compounds and flux are added to the melt A for smelting, and the melt A is continuously stirred at a speed of 300 to 500 r / min. By controlling the stirring speed of the melt A, the flux and rare earth compounds inside the melt A are evenly dispersed to ensure that the rare earth compounds are fully contacted and mixed with the aluminum melt, thereby further improving the performance of the rare earth aluminum alloy ingot.

[0018] Furthermore, in step (3), the additive A is first dried at a temperature of 80 to 120° C. for 1 to 2 hours, and then the additive A, the rare earth aluminum alloy powder and the additive B are placed in a mixer for mixing. Since the additive A is mainly composed of salt substances such as fluoride and chloride, these substances will absorb moisture when exposed to the air and thus have a certain amount of water. Therefore, the additive A is dried at a certain temperature to remove the water to prevent the water from affecting the subsequent smelting.

[0019] Furthermore, the oxygen content of the aluminum alloy powder obtained in step (3) is below 10 ppm, and the proportion of hollow powder is below 0.5%. The present invention adopts a vacuum atomization powder making method, and reasonably controls conditions such as atomization pressure and atomization gas flow rate, so as to obtain aluminum alloy powder with low oxygen content and stable structure, ensuring that the aluminum alloy powder can have good deterioration and grain refinement performance.

[0020] Furthermore, in step (4), the rare earth aluminum alloy powder obtained in step (2), auxiliary agent A and auxiliary agent B are placed in a mixer and mixed for 0.5 to 1.0 hour to obtain a mixture.

[0021] Compared with the prior art, this technical solution has the following beneficial effects:

[0022] 1. The modification and grain refiner for Al-Si die-casting aluminum alloy of the present invention has the function of simultaneously modifying eutectic Si and refining α-Al matrix grains, and can also play a refining role on aluminum alloy melt.

[0023] 2. The present invention prepares powder by atomizing a rare earth aluminum alloy with an inert gas in a vacuum atomizing furnace. The high cooling rate provided by the atomization process can refine the size of the intermetallic compounds inside the rare earth aluminum alloy powder, and obtain a distribution state of intermetallic compounds with small size and dispersed distribution. In this way, the rare earth elements can be evenly dispersed in the aluminum alloy melt, thereby improving the modification and grain refinement effects of the Al-Si die-casting aluminum alloy. DETAILED DESCRIPTION

[0024] The present invention is further described by the following examples, but is not intended to be limiting of the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods commonly known to those skilled in the art.

[0025] Embodiment 1:

[0026] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 75% rare earth aluminum alloy powder, 24.6% auxiliary agent A, and 24.6% auxiliary agent B. 0.4%; in the rare earth aluminum alloy powder, the rare earth element La accounts for 6.2% of the total amount, the rare earth element Ce accounts for 5.5% of the total amount, Fe and Si account for 0.09% of the total amount, and the balance is aluminum; the auxiliary agent A includes the following components in mass percentage: light calcium carbonate: 2.5%, sodium cryolite 6%, potassium cryolite 5%, sodium fluorosilicate 3%, lithium fluoride 3%, potassium fluoride 1.5%, sodium fluoride 11%, aluminum fluoride 3%, sodium chloride 16%, potassium chloride 16%, potassium fluoroborate 6%, magnesium chloride 3%, hexachloroethane 24%; the auxiliary agent B includes the following components in mass percentage: polyethylene glycol 46%, stearamide 54%; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0027] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0028] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 940°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 400 r / min and kept warm for 1.5 hours, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 25 minutes, the flow rate of the argon gas is 80m / s. 3 / h, after refining, the slag is removed and allowed to stand for 16 min, and then cast into ingots to obtain rare earth aluminum alloy ingots; the rare earth compounds are lanthanum oxide and cerium oxide; the flux includes the following components in mass percentage: NaF 15%, NaCl 30%, KCl 48%, cryolite 7%; the mass ratio of the aluminum ingot to the flux is 4.3:1; the casting temperature is 880°C;

[0029] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 840°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1.5 hours, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 4.5MPa, and the atomization gas flow rate is 8Nm 3 / min; the oxygen content of the obtained aluminum alloy powder is 7ppm, and the proportion of hollow powder is 0.37%;

[0030] (3) First, the additive A is dried at a temperature of 120° C. for 1.5 hours, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are put into a mixer and mixed for 45 minutes to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0031] Embodiment 2:

[0032] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 70% of rare earth aluminum alloy powder, 29.5% of auxiliary agent A, and 0.5% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth element Y accounts for 4.8% of the total amount, rare earth element Er accounts for 5.6% of the weight, Fe and Si together account for 0.08% of the total amount, and the balance is aluminum; the auxiliary agent A comprises the following components in mass percentage: 1% of light calcium carbonate, 5% of sodium cryolite, 5% of potassium cryolite, 3% of fluorosilicic acid, 4% of lithium fluoride, 3% of potassium fluoride, 10% of sodium fluoride, 3% of aluminum fluoride, 15% of sodium chloride, 13% of potassium chloride, 5% of potassium fluoroborate, 3% of magnesium chloride, and 30% of hexachloroethane; the auxiliary agent B comprises the following components in mass percentage: 45% of polyethylene glycol and 55% of stearamide; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0033] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0034] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 980°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 300 r / min and kept warm for 1.5 hours, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 20 minutes, the flow rate of the argon gas is 4m / s. 3 / h, after refining, the slag is removed and allowed to stand for 15 minutes, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is yttrium fluoride and erbium fluoride; the flux comprises the following components in mass percentage: NaF 10%, NaCl 35%, KCl 50%, cryolite 5%; the mass ratio of the aluminum ingot to the flux is 4:1; the casting temperature is 850°C;

[0035] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 820°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1 hour, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 4.5MPa, and the atomization gas flow rate is 8Nm 3 / min; the oxygen content of the obtained aluminum alloy powder was 10ppm, and the proportion of hollow powder was 0.45%;

[0036] (3) First, the additive A is dried at a temperature of 110° C. for 1 hour, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are put into a mixer and mixed for 30 minutes to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0037] Embodiment 3:

[0038] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 75% of rare earth aluminum alloy powder, 24.9% of auxiliary agent A, and 0.1% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth element Sc accounts for 2.5% of the total amount, rare earth element Er accounts for 6.3% of the weight, Fe and Si account for 0.08% of the total amount, and the balance is aluminum; the auxiliary agent A comprises the following components in mass percentage: 3% of light calcium carbonate, 6% of sodium cryolite, 5% of potassium cryolite, 3% of sodium fluorosilicate, 8% of lithium fluoride, 3% of potassium fluoride, 10% of sodium fluoride, 9% of aluminum fluoride, 20% of sodium chloride, 15% of potassium chloride, 5% of potassium fluoroborate, 3% of magnesium chloride, and 10% of hexachloroethane; the auxiliary agent B comprises the following components in mass percentage: 50% of polyethylene glycol and 50% of stearamide; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0039] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0040] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 1000°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 350 r / min and kept warm for 1.2 hours, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 25 minutes, the flow rate of the argon gas is 6m / s. 3 / h, after refining, the slag is removed and allowed to stand for 18 minutes, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is erbium fluoride and scandium fluoride; the flux includes the following components in mass percentage: NaF 18%, NaCl 30%, KCl 47%, and cryolite 5%; the mass ratio of the aluminum ingot to the flux is 5:1; the casting temperature is 860°C;

[0041] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 800°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1.2 hours, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 3.0 MPa, and the atomization gas flow rate is 12 Nm 3 / min; the oxygen content of the obtained aluminum alloy powder was 7ppm, and the proportion of hollow powder was 0.41%;

[0042] (3) First, the additive A is dried at a temperature of 100° C. for 1.5 hours, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are placed in a mixer and mixed for 50 minutes to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0043] Embodiment 4:

[0044] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 80% of rare earth aluminum alloy powder, 19.6% of auxiliary agent A, and 0.4% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth element Sc accounts for 2.8% of the total amount, Fe and Si account for 0.08% of the total amount, and the balance is aluminum; the auxiliary agent A comprises the following components in mass percentage: 3% of light calcium carbonate, 6% of sodium cryolite, 5% of potassium cryolite, 3% of sodium fluorosilicate, 4% of lithium fluoride, 3% of potassium fluoride, 10% of sodium fluoride, 3% of aluminum fluoride, 15% of sodium chloride, 20% of potassium chloride, 5% of potassium fluoroborate, 3% of magnesium chloride, and 20% of hexachloroethane; the auxiliary agent B comprises the following components in mass percentage: 40% of polyethylene glycol and 60% of stearamide; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0045] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0046] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 950°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 500 r / min and kept warm for 1.5 hours, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 25 minutes, the flow rate of the argon gas is 7m / s. 3 / h, after refining, the slag is removed and allowed to stand for 15 min, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is scandium fluoride; the flux comprises the following components in mass percentage: NaF20%, NaCl 35%, KCl 35%, and cryolite 10%; the mass ratio of the aluminum ingot to the flux is 4.5:1; the casting temperature is 900°C;

[0047] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 880°C, and the vacuum degree is ≤10 -2Pa, and after keeping warm for 1 hour, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 4.5MPa, and the atomization gas flow rate is 8Nm 3 / min; the oxygen content of the obtained aluminum alloy powder was 10ppm, and the proportion of hollow powder was 0.49%;

[0048] (3) First, the additive A is dried at a temperature of 90° C. for 2 hours, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are put into a mixer and mixed for 69 minutes to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0049] Embodiment 5:

[0050] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 60% of rare earth aluminum alloy powder, 39% of auxiliary agent A, and 1.0% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth element Y accounts for 2% of the total amount, Fe and Si account for 0.1% of the total amount, and the balance is aluminum; the auxiliary agent A comprises the following components in mass percentage: 1% of light calcium carbonate, 5% of sodium cryolite, 10% of potassium cryolite, 6% of sodium fluorosilicate, 6% of lithium fluoride, 4% of potassium fluoride, 15% of sodium fluoride, 6% of aluminum fluoride, 15% of sodium chloride, 15% of potassium chloride, 5% of potassium fluoroborate, 2% of magnesium chloride, and 10% of hexachloroethane; the auxiliary agent B comprises the following components in mass percentage: 42% of polyethylene glycol and 58% of stearamide; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0051] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0052] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 850°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 450 r / min and kept warm for 1.5 hours, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 30 minutes, the flow rate of the argon gas is 4m / s. 3 / h, after refining, the slag is removed and allowed to stand for 15 min, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is yttrium fluoride; the flux comprises the following components in mass percentage: NaF 10%, NaCl 35%, KCl 50%, and cryolite 5%; the mass ratio of the aluminum ingot to the flux is 4.6:1; the casting temperature is 850°C; the oxygen content of the obtained aluminum alloy powder is 9ppm, and the proportion of hollow powder is 0.41%;

[0053] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 760°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1.5 hours, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 2.0 MPa, and the atomization gas flow rate is 5 Nm 3 / min;

[0054] (3) First, the additive A is dried at a temperature of 80° C. for 2 hours, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are put into a mixer and mixed for 30 minutes to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0055] Embodiment 6:

[0056] A modification and grain refiner for Al-Si die-casting aluminum alloy, comprising the following components in mass percentage: 80% of rare earth aluminum alloy powder, 19% of auxiliary agent A, and 1.0% of auxiliary agent B; in the rare earth aluminum alloy powder, rare earth elements account for 2-20% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the auxiliary agent A comprises the following components in mass percentage: 5% of light calcium carbonate, 10% of sodium cryolite, 5% of potassium cryolite, 3% of sodium fluorosilicate, 6% of lithium fluoride, 1% of potassium fluoride, 10% of sodium fluoride, 5% of aluminum fluoride, 16% of sodium chloride, 17% of potassium chloride, 8% of potassium fluoroborate, 4% of magnesium chloride, and 10% of hexachloroethane; the auxiliary agent B comprises the following components in mass percentage: 40-50% of polyethylene glycol and 50-60% of stearamide; the purity of each component in the modification and grain refiner for Al-Si die-casting aluminum alloy is ≥99.9%.

[0057] The method for preparing the modification and grain refiner for Al-Si die-casting aluminum alloy described in this embodiment comprises the following steps:

[0058] (1) Rare earth compound, flux and aluminum ingot are weighed in proportion, the aluminum ingot is first charged into a furnace and heated to 1250°C to obtain a melt, rare earth compound and flux are added to the melt A for smelting, the melt A is continuously stirred at a speed of 400 r / min and kept warm for 1 hour, and then 99.99% high-purity argon gas is introduced into the melt A for refining for 30 minutes, the flow rate of the argon gas is 10m / s. 3 / h, after refining, the slag is removed and allowed to stand for 20 min, and then cast into ingots to obtain rare earth aluminum alloy ingots; the rare earth compound is any one or a combination of two of lanthanum oxide, cerium oxide, yttrium fluoride, erbium fluoride, and scandium fluoride; the flux includes the following components in mass percentage: NaF 20%, NaCl 20%, KCl 50%, and cryolite 10%; the mass ratio of the aluminum ingot to the flux is 4.8:1; the casting temperature is 850°C to 900°C;

[0059] (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 900°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1 hour, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 5.0 MPa, and the atomization gas flow rate is 15 Nm 3 / min; the oxygen content of the obtained aluminum alloy powder was 8ppm, and the proportion of hollow powder was 0.43%;

[0060] (3) First, the additive A is dried at a temperature of 120° C. for 1 hour, and then the rare earth aluminum alloy powder obtained in step (2), the additive A and the additive B are put into a mixer and mixed for 1.0 hour to obtain a mixture, and the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

[0061] Comparative Example 1:

[0062] An Al-Ti-B master alloy comprises the following components in percentage by mass: 4.9% Ti, 1.0% B, 0.15% Fe, 0.12% Si, and the balance being aluminum.

[0063] The Al-Ti-B master alloy preparation method comprises the following steps:

[0064] (1) Load the aluminum ingot into the smelting furnace, heat the aluminum ingot to 950°C and keep it warm;

[0065] (2) When the charge in step (1) is completely melted, add K2TiF6 to the resulting melt and set the melting temperature to 950°C.

[0066] (3) When the charge in step (2) is completely melted, KBF4 is added to the obtained melt, the melting temperature is set to 950°C, and the melt is continuously stirred and kept warm for 1.5 hours;

[0067] (4) After the reaction in step (3) has been carried out for 0.5 hour, the melt is refined by introducing argon into the melt, and the refining temperature is set to 950°C and the refining time is set to 30 min;

[0068] (5) After refining, the slag is removed, allowed to stand for 20 min, and then cast into ingots to obtain an Al-Ti-B master alloy.

[0069] Comparative Example 2:

[0070] An Al-Sr master alloy comprises the following components in weight percentage: 9.8% Sr, 0.17% Fe, 0.14% Si, and the balance being aluminum.

[0071] The Al-Sr master alloy preparation method comprises the following steps:

[0072] (1) Loading the aluminum ingot into a smelting furnace, heating the aluminum ingot to 820°C and keeping it warm, and adding a surface covering agent;

[0073] (2) When the charge in (1) is completely melted, add metallic strontium to the resulting melt and press it into the melt. The melting temperature is 820°C and the temperature is maintained.

[0074] (3) After the reaction in (2) has been carried out for 0.5 hour, the melt is refined by introducing argon into the melt, and the refining temperature is set to 820°C and the refining time is set to 30 min;

[0075] (4) After refining, the slag is removed, allowed to stand for 20 min, and then cast into an ingot to obtain an Al-Sr intermediate alloy with a Sr content of 9.0~10.0%.

[0076] Comparative Example 3:

[0077] An Al-La-Ce rare earth master alloy is prepared by weighing a rare earth compound, a flux and an aluminum ingot in proportion, first charging the aluminum ingot into a furnace and heating it to 940° C. to obtain a melt, adding the rare earth compound and the flux to the melt A for smelting, stirring the melt A for 3 consecutive times, and keeping the temperature for 1.5 hours, then introducing 99.99% high-purity argon gas into the melt A for refining for 25 minutes, wherein the flow rate of the argon gas is 80 m / s. 3 / h, after refining, the slag is removed and allowed to stand for 16 minutes, and then cast into ingots to obtain Al-La-Ce rare earth master alloy; the rare earth compounds are lanthanum oxide and cerium oxide; the flux comprises the following components in mass percentage: NaF 15%, NaCl 30%, KCl 48%, and cryolite 7%; the mass ratio of the aluminum ingot to the flux is 4:1; the casting temperature is 880°C, and the La content in the Al-La-Ce rare earth master alloy is 6.2%, and the Ce content is 5.5%.

[0078] Experimental example:

[0079] Modification and grain refinement agents were prepared according to the methods described in Examples 1 to 6, and different master alloys were prepared according to the methods described in Comparative Examples 1 to 3, which were used to prepare Al-Si die-cast aluminum alloys, and eutectic Si modification effect tests, secondary dendrite arm spacing measurements, and hydrogen content tests were performed. Examples 1 to 6 were added at a ratio of 1 / 200 of the weight of the aluminum alloy, the Al-Ti-B alloy of Comparative Example 1 was added at a ratio of 1 / 200 of the weight of the aluminum alloy, the Al-Sr master alloy of Comparative Example 2 was added at a ratio of 0.02% of the weight of the aluminum alloy, and the bulk Al-La-Ce master alloy of Comparative Example 3 was added at a ratio of 1 / 200 of the weight of the aluminum alloy. The specific results are shown in Tables 1 and 2.

[0080] Table 1 Test results of eutectic Si modification effect

[0081]

[0082] Table 2 Secondary dendrite arm spacing measurement and hydrogen content test results

[0083]

[0084] As can be seen from Table 1, the method of the present invention has both the effect of modifying and refining the grains of two kinds of Al-Si die-casting aluminum alloys, and can effectively control the hydrogen content in the alloy at a lower level; Al-Ti5-B1 ​​alloy can only refine the aluminum alloy matrix grains, but cannot produce a modifying effect on eutectic Si, and does not have the effect of refining and dehydrogenation; Al-Sr10 alloy only produces a modifying effect on eutectic Si, but cannot refine the aluminum alloy matrix grains, and because the Sr element is more active, the alloy hydrogen content is higher. The effect of the intermediate alloy in Comparative Example 3 is not as good as that obtained by the present invention, indicating that simply using a rare earth intermediate alloy does not necessarily achieve good results. Therefore, the modifying and grain refining agent for Al-Si die-casting aluminum alloys described in the present invention has obvious modifying and grain refining effects on Al-Si aluminum alloy materials, and has the effect of dehydrogenation and impurity removal, and has a wide range of applications.

[0085] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a modification and grain refiner for Al-Si die-casting aluminum alloy, characterized in that: The modification and grain refiner for Al-Si die-casting aluminum alloy comprises the following components in mass percentage: rare earth aluminum alloy powder 60-80%, auxiliary agent A 19-39%, auxiliary agent B 0.1-1.0%; in the rare earth aluminum alloy powder, rare earth elements account for 2-20% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the rare earth element is any one or a combination of two of La, Ce, Y, Er, and Sc; the auxiliary agent A includes the following components in mass percentage: light calcium carbonate 1-5%, sodium cryolite 5-10%, potassium cryolite 5-10%, sodium fluorosilicate 3-6%, lithium fluoride 3-8%, potassium fluoride 1-4%, sodium fluoride 10-15%, aluminum fluoride 3-9%, sodium chloride 15-20%, potassium chloride 15-20%, potassium fluoroborate 5-8%, magnesium chloride 2-4%, and hexachloroethane 10-30%; the auxiliary agent B includes the following components in mass percentage: polyethylene glycol 40-50%, stearamide 50-60%; The preparation method comprises the following steps: (1) Weighing rare earth compounds, flux and aluminum ingots in proportion, first charging the aluminum ingots into a furnace and heating them to 850°C to 1250°C to obtain melt A, adding rare earth compounds and flux to melt A for smelting, stirring melt A continuously and keeping the temperature for 1 to 1.5 hours, then introducing 99.99% high-purity argon gas into melt A for refining for 20 to 30 minutes, the flow rate of the argon gas being 4 to 10 m / s. 3 / h, after refining, the slag is removed and allowed to stand for 15 to 20 minutes, and then cast into an ingot to obtain a rare earth aluminum alloy ingot; the rare earth compound is any one or a combination of two of lanthanum oxide, cerium oxide, yttrium fluoride, erbium fluoride, and scandium fluoride; the flux comprises the following components in mass percentage: NaF 10 to 20%, NaCl 20 to 35%, KCl 35 to 50%, and cryolite 5 to 10%; the mass ratio of the aluminum ingot to the flux is (4 to 5):1; (2) The rare earth aluminum alloy ingot obtained in step (1) is placed in a vacuum atomization furnace. The temperature in the induction melting chamber of the vacuum atomization furnace is first raised to 760°C to 900°C, and the vacuum degree is ≤10 -2 Pa, and after keeping warm for 1 to 1.5 hours, melt B is obtained, and melt B is transferred to the atomization chamber of a vacuum atomization furnace for inert gas atomization to obtain rare earth aluminum alloy powder; the inert gas uses 99.99% high-purity argon, the atomization pressure is 2.0 to 5.0 MPa, and the atomization gas flow rate is 5 to 15 Nm 3 / min; (3) The rare earth aluminum alloy powder, additive A and additive B obtained in step (2) are placed in a mixer to mix to obtain a mixture, and then the mixture is pressed into blocks to obtain a round cake-shaped modification and grain refiner for Al-Si die-casting aluminum alloy.

2. The preparation method according to claim 1, characterized in that: The modification and grain refiner comprises the following components in percentage by mass: rare earth aluminum alloy powder 70-80%, auxiliary agent A 20-29.6%, auxiliary agent B 0.2-0.4%; in the rare earth aluminum alloy powder, rare earth elements account for 2-15% of the total amount, the total amount of Fe and Si is ≤0.1%, and the balance is aluminum; the rare earth element is any one or a combination of two of La, Ce, Y, Er, and Sc; the auxiliary agent A includes the following components in mass percentage: light calcium carbonate 2-4%, sodium cryolite 5-7%, potassium cryolite 5-7%, sodium fluorosilicate 3-5%, lithium fluoride 3-6%, potassium fluoride 1-3%, sodium fluoride 10-13%, aluminum fluoride 3-5%, sodium chloride 15-18%, potassium chloride 15-18%, potassium fluoroborate 5-6%, magnesium chloride 2-3%, and hexachloroethane 15-25%; the auxiliary agent B includes the following components in mass percentage: polyethylene glycol 40-45%, and stearamide 55-60%.

3. The preparation method according to claim 1, characterized in that: In step (1), rare earth compounds and flux are added to the melt A for smelting, and the melt A is continuously stirred at a speed of 300 to 500 r / min.

4. The preparation method according to claim 1, characterized in that: The casting temperature in step (1) is 850°C to 900°C.

5. The preparation method according to claim 1, characterized in that: In step (3), the auxiliary agent A is first dried at a temperature of 80 to 120° C. for 1 to 2 hours.

6. The preparation method according to claim 1, characterized in that: The aluminum alloy powder obtained in step (3) has an oxygen content of less than 10 ppm, and a proportion of hollow powders of less than 0.5%.

7. The preparation method according to claim 1, characterized in that: In step (3), the rare earth aluminum alloy powder, auxiliary agent A and auxiliary agent B obtained in step (2) are placed in a mixer and mixed for 0.5 to 1.0 hour to obtain a mixture.

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