Die-casting forming method for improving density of casting

Abstract

The invention relates to a die-casting forming method for improving the density of a casting, belongs to the technical field of aluminum alloy casting, and solves the problems of high porosity, low density and low mechanical property of an aluminum alloy thick-wall die casting in the prior art. A die-casting forming method for improving the density of a casting comprises the following steps that firstly, an aluminum alloy metal raw material is added into a preheated smelting furnace, melting and heating are conducted, aluminum alloy liquid is obtained, and a refining modifier is added and stirred; 2, degassing treatment is conducted on the aluminum alloy liquid, and surface scum is removed after standing; 3, a die-casting die is preheated, and a layer of release agent is sprayed on the die-casting die; 4, the molten aluminum alloy is cooled and poured into a pouring gate of the die-casting die, the thickness of the pouring gate is 8-12 mm, and the molten aluminum alloy is slowly injected into a cavity of the die-casting die through an injection punch; and 5, the aluminum alloy die casting is taken out, the die casting is placed in a water tank to be quenched, and the high-density die casting is obtained. And preparation of the high-density aluminum alloy thick-wall die casting is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy casting, and in particular to a die-casting method for improving the density of castings. Background Art

[0002] Aluminum alloy die-casting technology is suitable for the preparation of metal parts with thin-wall features due to its process characteristics of high-speed filling and high-pressure solidification and shrinkage feeding. For thick-walled castings, such as automobile fixing seats and load-bearing bracket parts, the high-pressure shrinkage feeding of traditional die-casting technology cannot completely eliminate the shrinkage and shrinkage defects in the thick parts of the castings, and the final castings have problems of high porosity and low density.

[0003] The existing technology mainly meets the requirements of low porosity and high toughness of thick-walled aluminum alloy parts by reducing the die-casting speed. However, in actual production, due to the reduction of the injection speed, defects such as cold shut, flow marks, and undercasting are easily caused, and there are still problems such as high porosity and high gas content. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a die-casting method for improving the density of castings, so as to solve at least one of the problems of existing aluminum alloy thick-walled die-castings, such as high porosity, low density, and low mechanical properties.

[0005] The embodiment of the present invention provides a die-casting method for improving the density of a casting, comprising the following steps:

[0006] Step 1, adding aluminum alloy metal raw materials into a preheated smelting furnace, melting and heating to obtain aluminum alloy liquid, and adding a refining modifier to the aluminum alloy liquid and stirring;

[0007] Step 2, degassing the aluminum alloy liquid prepared in step 1, and removing the surface scum after standing;

[0008] Step 3, preheating the die-casting mold, and evenly spraying a layer of release agent on the inner surface of the die-casting mold cavity;

[0009] Step 4, cooling the aluminum alloy liquid treated in step 2, pouring it into the inlet gate of the die-casting mold treated in step 3, the inlet gate thickness is 8-12 mm, and using an injection punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold;

[0010] Step 5: Open the die-casting mold, take out the aluminum alloy die-casting from the cavity, place the die-casting in a water tank for quenching, and obtain a high-density die-casting.

[0011] Furthermore, in step 1, the content of the aluminum alloy components is calculated by mass percentage as follows: Si: 11-13.5%, Cu: 0.5-1.3%, Mg: 0.8-1.2%, Ni: 0.5-1.3%, Mn: 0.01-0.05%, Ti: 0.01-0.05%, Fe: 0.02-1.0%, and the rest is Al.

[0012] Preferably, in step 1, the aluminum alloy metal raw material is melted and heated to 710-730°C.

[0013] It should be noted that in step 1, the refining modifier is a mixture of aluminum-titanium-boron master alloy and aluminum-strontium master alloy, and the aluminum-titanium-boron master alloy and the aluminum-strontium master alloy account for 0.1-0.4% of the total mass of the alloy respectively.

[0014] Exemplarily, in step 2, degassing is performed by rotary blowing of argon.

[0015] Specifically, the degassing time is 20-30 minutes, the argon flow rate is 1-5 L / min, and the mixture is left standing for 20-30 minutes.

[0016] Furthermore, the preheating temperature of the die-casting mold in step 3 is 150-200°C.

[0017] Preferably, in step 4, the aluminum alloy liquid is cooled to 670-690°C.

[0018] Furthermore, in step 4, the injection speed is 0.05-1.2 m / s, the casting pressure is 110-150 MPa, and the holding time is 2-10 s.

[0019] Furthermore, in step 5, the quenching temperature is 30-60°C.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] 1. The present invention achieves grain refinement and Si morphology modification by adding aluminum-titanium-boron master alloy and aluminum-strontium master alloy refiners during the aluminum alloy smelting process and controlling the added amount, so that the eutectic silicon is transformed from coarse needle-like to fine fiber-like, which plays a metamorphic role. The grain refinement can reduce the gaps between the grains, improve the density of the material, meet the density requirements required for subsequent heat treatment, and improve the strength and plasticity of the alloy.

[0022] 2. The present invention uses a rotary argon injection method to degas the aluminum alloy liquid, effectively reducing the gas content in the aluminum alloy liquid, avoiding defects such as pores and shrinkage cavities in the aluminum alloy liquid during the die-casting process, and effectively improving the density of the die-casting part.

[0023] 3. The die-casting process of the present invention adopts a relatively high casting pressure (110-150 MPa) combined with a relatively large gate thickness ratio (0.5-1.2), which effectively compensates for the thermal section of the casting and significantly improves the density of the casting.

[0024] 4. The present invention optimizes the alloy element composition, and the alloy composition is in the Al-Si alloy eutectic range, with low viscosity and good fluidity. It can better compensate for the shrinkage of the internal holes of the casting in the later stage of casting solidification, which helps to reduce shrinkage holes and shrinkage defects in the casting; and when the alloy changes from liquid to solid, α-Al and Si phases are formed at the same time, which is beneficial to improve the mechanical properties of the alloy.

[0025] 5. The present invention solves the problems of shrinkage, shrinkage cavities and other defects that are often prone to occur in thick-walled aluminum alloy die-castings by optimizing element composition and die-casting molds, adding an appropriate amount of refining modifiers, and cooperating with higher casting pressure, thereby improving the density of aluminum alloy die-castings, meeting the requirements of T6 and T7 heat treatments, and making the aluminum alloy die-castings meet the use requirements; the aluminum alloy die-castings prepared by the present invention have dense structure, low porosity, and excellent strength and plasticity indicators after heat treatment, with tensile strength ≥400MPa, yield strength ≥330MPa, and elongation ≥4%.

[0026] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 This is a microstructure diagram of the die casting prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0030] A specific embodiment of the present invention discloses a die-casting method for improving the density of a casting, comprising the following steps:

[0031] Step 1, adding aluminum alloy metal raw materials into a preheated smelting furnace, melting and heating to obtain aluminum alloy liquid, and adding a refining modifier to the aluminum alloy liquid and stirring;

[0032] Step 2, degassing the aluminum alloy liquid prepared in step 1, and removing the surface scum after standing;

[0033] Step 3, preheating the die-casting mold, and evenly spraying a layer of release agent on the inner surface of the die-casting mold cavity;

[0034] Step 4, cooling the aluminum alloy liquid treated in step 2, pouring it into the inlet gate of the die-casting mold treated in step 3, the inlet gate thickness is 8-12 mm, and using an injection punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold;

[0035] Step 5: Open the die-casting mold, take out the aluminum alloy die-casting from the cavity, place the die-casting in a water tank for quenching, and obtain a high-density die-casting.

[0036] Furthermore, in step 1, the content of the aluminum alloy components is calculated by mass percentage as follows: Si: 11-13.5%, Cu: 0.5-1.3%, Mg: 0.8-1.2%, Ni: 0.5-1.3%, Mn: 0.01-0.05%, Ti: 0.01-0.05%, Fe: 0.02-1.0%, and the rest is Al.

[0037] The following is a detailed description of the effects and dosage of the components in the present invention:

[0038] Si: forms primary Si and eutectic Si in the structure to ensure the wear resistance and fluidity of the alloy. The addition amount is within the range of Al-Si alloy eutectic. The preferred Si content is 11-13.5%.

[0039] Cu and Ni: Cu and Ni form Al7Cu4Ni phase, which improves the high temperature performance of the alloy. Too much addition reduces the elongation of the alloy. The preferred Cu content is 0.5-1.3%, and the Ni content is 0.5-1.3%.

[0040] Mg: Forms Mg2Si phase, forms dispersed Mg2Si strengthening phase during heat treatment, improves alloy strength and plasticity. Too much addition reduces alloy elongation. The preferred Mg content is 0.8-1.2%.

[0041] Mn: Improves the Fe phase morphology. Too much Mn will form a Mn-rich second phase, which will reduce the alloy properties. The preferred Mn content is 0.01-0.05%.

[0042] Ti: refines the grain structure. Too much addition forms a coarse Ti-rich phase, which reduces the alloy properties. The preferred Ti content is 0.01-0.05%.

[0043] Fe: Reduces the tendency of sticking to the mold. Too much addition reduces the elongation of the alloy. The preferred Fe content is 0.02-1.0%.

[0044] Depend on Figure 1 It can be seen that the microstructure after die casting is fine and dense, the α-Al phase in the structure presents a fine dendritic morphology, the average grain size is 30-50μm, and there is a high area fraction of short rod-shaped eutectic Si phase at the grain boundary, which provides the alloy with better fluidity. At the same time, since the Si content is in the eutectic range, there is a blocky primary Si phase in the structure, which can improve the wear resistance of the alloy.

[0045] Preferably, in step 1, the aluminum alloy metal raw material is melted and heated to 710-730°C.

[0046] Exemplarily, in step 1, the refining modifier is a mixture of aluminum-titanium-boron master alloy and aluminum-strontium master alloy, and the aluminum-titanium-boron master alloy and the aluminum-strontium master alloy account for 0.1-0.4% of the total mass of the alloy, respectively, and there is no restriction on the addition ratio between the two. Specifically, the addition amount of aluminum-titanium-boron master alloy accounts for 0.1%, 0.2%, 0.3%, and 0.4% of the total mass of the alloy; the addition amount of aluminum-strontium master alloy accounts for 0.1%, 0.2%, 0.3%, and 0.4% of the total mass of the alloy.

[0047] The aluminum-titanium-boron master alloy is composed of Al5TiB, and the addition amount is 0.1-0.4%. After addition, Al3Ti and TiB2 are formed in the melt, which can serve as grain nucleation particles and play a role in refining grains. Too much addition will form coarse Al3Ti phase and reduce the mechanical properties of the alloy.

[0048] The composition of aluminum-strontium master alloy is Al10Sr, and the addition amount is 0.1-0.4%. After addition, Sr atoms can inhibit the growth of Si phase and cause the Si morphology to undergo a fiber transformation, that is, from coarse needle-like to fine fiber-like, which plays a metamorphic role. If the addition amount is too much, the metamorphic effect will not continue to improve.

[0049] By adding two kinds of refiners, aluminum-titanium-boron master alloy and aluminum-strontium master alloy, grain refinement and Si morphology modification can be achieved. Grain refinement can reduce the gaps between grains, increase the density of the material, and thus improve the strength and plasticity of the alloy.

[0050] Furthermore, in step 2, degassing is performed by rotary blowing of argon, the degassing time is 20-30 minutes, the argon flow rate is 1-5L / min, and the mixture is allowed to stand for 20-30 minutes; the introduction of argon can effectively reduce the gas content in the aluminum alloy liquid, thereby improving the mechanical properties of the aluminum alloy; the argon gas can be broken into tiny bubbles by rotary blowing, and the bubbles carry away the gas and scum in the aluminum liquid during the rising process, thereby achieving the purpose of purifying the aluminum liquid.

[0051] It is worth noting that in step 3, the preheating temperature of the die-casting mold is 150-200°C.

[0052] Improper mold temperature setting will affect the performance of the casting. Too low a temperature will lead to difficulty in casting molding, incomplete filling and cold shut defects; too high a temperature will lead to defects such as bubbles, sticking and shrinkage holes on the casting surface, and reduce the service life of the mold.

[0053] Specifically, in step 4, the aluminum alloy liquid is cooled to 670-690°C.

[0054] Furthermore, in step 4, the thickness of the gate of the die-casting mold is 8 to 12 mm. The average wall thickness of the die-casting is 8 to 20 mm.

[0055] Exemplarily, in step 4, the injection speed is 0.05-1.2 m / s, the casting pressure is 110-150 MPa, and the holding time is 2-10 s. Specifically, the injection speed is 0.05 m / s, 0.1 m / s, 0.15 m / s, 0.2 m / s, 0.5 m / s, 0.8 m / s, 1 m / s, 1.2 m / s; the casting pressure is 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa.

[0056] Higher casting pressure (110-150MPa) combined with a larger gate thickness ratio (0.5-1.2) can effectively compensate for the thermal expansion of the casting and significantly improve the density of the casting. The alloy composition is close to the Al-Si eutectic and has better fluidity, which can better compensate for the internal pores of the casting in the later stage of casting solidification.

[0057] Preferably, in step 5, the quenching temperature is 30-60° C., and the surface hardness of the casting is increased by quenching, thereby reducing the wear and corrosion of the casting during use.

[0058] T6 heat treatment refers to complete artificial aging after solution treatment, which is suitable for products that are no longer cold processed. T7 heat treatment refers to stabilization treatment after solution treatment, which is suitable for products whose strength exceeds the peak point during artificial aging. Both heat treatments require the alloy to have a certain density to ensure that there will not be excessive pore expansion or other defects during the heat treatment process, thereby ensuring the mechanical properties and dimensional stability of the alloy.

[0059] In summary, the present invention solves the problems of shrinkage porosity, shrinkage cavities and other defects that are often prone to occur in thick-walled aluminum alloy die castings, thereby improving the density of aluminum alloy die castings, meeting the requirements of T6 and T7 heat treatments, and enabling aluminum alloy die castings to meet use requirements; the aluminum alloy die castings prepared by the present invention have a dense structure, low porosity, and excellent strength and plasticity indicators after heat treatment, with a tensile strength of ≥400MPa, a yield strength of ≥330MPa, and an elongation of ≥4%.

[0060] The die-casting method for improving the density of castings of the present invention is described below in conjunction with specific embodiments.

[0061] Example 1

[0062] This embodiment provides a die-casting method for improving the density of a casting.

[0063] The composition of the aluminum alloy is in percentage by mass: Si: 12.4%, Cu: 1.1%, Mg: 1.0%, Ni: 0.5%, Mn: 0.05%, Ti: 0.04%, Fe: 0.3%, and the rest is Al, as shown in Table 1.

[0064] The average wall thickness of the casting is 10mm.

[0065] The molding method comprises the following steps:

[0066] Step 1, adding aluminum alloy metal raw materials into a preheated melting furnace to melt the aluminum alloy metal raw materials and heat them to 730° C. to obtain aluminum alloy liquid;

[0067] Step 2, adding a refining modifier to the aluminum alloy liquid obtained in step 1, and then stirring the aluminum alloy liquid and the refining modifier together;

[0068] The refining modifier is aluminum-titanium-boron master alloy and aluminum-strontium master alloy, wherein the addition amount of aluminum-titanium-boron accounts for 0.1% of the total mass of the alloy, and the aluminum-strontium master alloy accounts for 0.4% of the total mass of the alloy;

[0069] Step 3, the aluminum alloy liquid prepared in step 2 is degassed by a rotary argon blowing method, the degassing time is 20 minutes, the argon flow rate is 3L / min, and the mixture is allowed to stand for 20 minutes, and then the surface scum is removed after standing;

[0070] Step 4: preheat the die-casting mold to 180°C, and spray a layer of release agent on the inner surface of the die-casting mold cavity;

[0071] Step 5, cool the aluminum alloy liquid in the smelting furnace to 690°C, pour it into the inlet gate of the die-casting mold, the mold inlet gate thickness is 10mm (the gate thickness ratio is 1), and use the injection punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold; the slow injection speed is 0.1m / s, the casting pressure is 110Mpa, and the holding time is 8s;

[0072] Step 6: Open the die-casting mold, then take out the aluminum alloy die-casting from the cavity, and place the die-casting in a water tank for quenching at a quenching temperature of 50° C. to obtain a high-density die-casting.

[0073] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0074] Example 2

[0075] This embodiment provides a die-casting method for improving the density of a casting.

[0076] The components of the aluminum alloy are calculated by mass percentage: Si: 12.9%, Cu: 1.3%, Mg: 1.0%, Ni: 1.2%, Mn: 0.05%, Ti: 0.05%, Fe: 0.3%, and the rest is Al, as shown in Table 1.

[0077] The average wall thickness of the casting is 12mm.

[0078] The molding method comprises the following steps:

[0079] Step 1, adding aluminum alloy metal raw materials into a preheated melting furnace to melt the aluminum alloy metal raw materials and heat them to 730° C. to obtain aluminum alloy liquid;

[0080] Step 2, adding a refining modifier to the aluminum alloy liquid obtained in step 1, and then stirring the aluminum alloy liquid and the refining modifier together;

[0081] The refining modifier is aluminum-titanium-boron master alloy and aluminum-strontium master alloy, wherein the addition amount of aluminum-titanium-boron accounts for 0.2% of the total mass of the alloy, and the aluminum-strontium master alloy accounts for 0.4% of the total mass of the alloy;

[0082] Step 3, the aluminum alloy liquid prepared in step 2 is degassed by a rotary argon blowing method, the degassing time is 30 minutes, the argon flow rate is 1L / min, and the mixture is allowed to stand for 30 minutes, and then the surface scum is removed after standing;

[0083] Step 4: preheat the die-casting mold to 180°C, and spray a layer of release agent on the inner surface of the die-casting mold cavity;

[0084] Step 5, cool the aluminum alloy liquid in the smelting furnace to 670°C, pour it into the inlet gate of the die-casting mold, the mold inlet gate thickness is 8mm (gate thickness ratio is 0.67), and use a shot punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold; the slow injection speed is 0.1m / s, the casting pressure is 130Mpa, and the holding time is 8s;

[0085] Step 6: Open the die-casting mold, then take out the aluminum alloy die-casting from the cavity, and place the die-casting in a water tank for quenching at a quenching temperature of 50° C. to obtain a high-density die-casting.

[0086] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0087] Example 3

[0088] This embodiment provides a die-casting method for improving the density of a casting.

[0089] The composition of the aluminum alloy is in percentage by mass: Si: 11.6%, Cu: 1.0%, Mg: 0.9%, Ni: 1.0%, Mn: 0.05%, Ti: 0.05%, Fe: 0.3%, and the rest is Al, as shown in Table 1.

[0090] The average wall thickness of the casting is 16mm.

[0091] The molding method comprises the following steps:

[0092] Step 1, adding aluminum alloy metal raw materials into a preheated melting furnace to melt the aluminum alloy metal raw materials and heat them to 730° C. to obtain aluminum alloy liquid;

[0093] Step 2, adding a refining modifier to the aluminum alloy liquid obtained in step 1, and then stirring the aluminum alloy liquid and the refining modifier together;

[0094] The refining modifier is aluminum-titanium-boron master alloy and aluminum-strontium master alloy, wherein the addition amount of aluminum-titanium-boron accounts for 0.3% of the total mass of the alloy, and the aluminum-strontium master alloy accounts for 0.3% of the total mass of the alloy;

[0095] Step 3, the aluminum alloy liquid prepared in step 2 is degassed by a rotary argon blowing method, the degassing time is 30 minutes, the argon flow rate is 1L / min, and the mixture is allowed to stand for 30 minutes, and then the surface scum is removed after standing;

[0096] Step 4: preheat the die-casting mold to 180°C, and spray a layer of release agent on the inner surface of the die-casting mold cavity;

[0097] Step 5, cool the aluminum alloy liquid in the smelting furnace to 670°C, pour it into the inlet gate of the die-casting mold, the mold inlet gate thickness is 10mm (gate thickness ratio is 0.63), and use a shot punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold; the slow injection speed is 0.06m / s, the casting pressure is 150Mpa, and the holding time is 8s;

[0098] Step 6: Open the die-casting mold, then take out the aluminum alloy die-casting from the cavity, and place the die-casting in a water tank for quenching at a quenching temperature of 50° C. to obtain a high-density die-casting.

[0099] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0100] Comparative Example 1

[0101] This embodiment provides a die-casting method for improving the density of a casting.

[0102] The components of the aluminum alloy are in percentage by mass: Si: 8.9%, Cu: 1.1%, Mg: 0.9%, Ni: 0.7%, Mn: 0.05%, Ti: 0.05%, Fe: 0.3%, and the rest is Al, as shown in Table 1.

[0103] The molding method is the same as that in Example 1.

[0104] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0105] Comparative Example 2

[0106] This embodiment provides a die-casting method for improving the density of a casting.

[0107] The composition of the aluminum alloy is in percentage by mass: Si: 11.2%, Cu: 0.1%, Mg: 0.9%, Ni: 1.1%, Mn: 0.02%, Ti: 0.03%, Fe: 0.2%, and the rest is Al, as shown in Table 1.

[0108] The molding method is the same as that in Example 1.

[0109] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0110] Comparative Example 3

[0111] This embodiment provides a die-casting method for improving the density of a casting.

[0112] The composition of the aluminum alloy is in percentage by mass: Si: 10.2%, Cu: 0.6%, Mg: 2.9%, Ni: 0.8%, Mn: 0.02%, Ti: 0.03%, Fe: 0.5%, and the rest is Al, as shown in Table 1.

[0113] The molding method is the same as that in Example 1.

[0114] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0115] Comparative Example 4

[0116] This embodiment provides a die-casting method for improving the density of a casting.

[0117] The composition of the aluminum alloy is the same as that of Example 1 in terms of mass percentage.

[0118] The molding method is basically the same as that of Example 1, except that in step 5, the thickness of the gate of the die-casting mold is 4 mm (the gate thickness ratio is 0.4).

[0119] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0120] Comparative Example 5

[0121] This embodiment provides a die-casting method for improving the density of a casting.

[0122] The composition of the aluminum alloy is the same as that of Example 1 in terms of mass percentage.

[0123] The forming method is basically the same as that of Example 1, except that in step 2, the amount of aluminum, titanium and boron added is 0.03% of the total mass of the alloy, and the aluminum strontium master alloy is 0.01% of the total mass of the alloy.

[0124] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0125] Comparative Example 6

[0126] This embodiment provides a die-casting method for improving the density of a casting.

[0127] The composition of the aluminum alloy is the same as that of Example 1 in terms of mass percentage.

[0128] The molding method is basically the same as that in Example 1, except that in step 5, the slow injection speed is 0.1 m / s, the casting pressure is 60 MPa, and the holding time is 5 s.

[0129] The yield strength, tensile strength and elongation of the aluminum alloy die castings after T6 heat treatment were determined according to the test standard GB / T228.1-2021. The results are shown in Table 2.

[0130] Table 1 Aluminum alloy composition and mass percentage (wt%) of the embodiment and comparative example

[0131] serial number Si Cu Mg Ni Mn Ti Fe Example 1 12.4 1.1 1.0 0.5 0.05 0.04 0.3 Example 2 12.9 1.3 1.0 1.2 0.05 0.05 0.3 Example 3 11.6 1.0 0.9 1.0 0.05 0.05 0.3 Comparative Example 1 8.9 1.1 0.9 0.7 0.05 0.05 0.3 Comparative Example 2 11.2 0.1 0.9 1.1 0.02 0.03 0.2 Comparative Example 3 10.2 0.6 2.9 0.8 0.02 0.03 0.5 Comparative Example 4 12.4 1.1 1.0 0.5 0.05 0.04 0.3 Comparative Example 5 12.4 1.1 1.0 0.5 0.05 0.04 0.3 Comparative Example 6 12.4 1.1 1.0 0.5 0.05 0.04 0.3

[0132] Table 2 Mechanical properties of aluminum alloy die castings after heat treatment in Example and Comparative Example

[0133]

[0134]

[0135] The alloy composition of Examples 1 to 3 of the present invention meets the requirements of the present invention. The aluminum alloy die-castings produced by the die-casting method of the present invention have excellent strength and plasticity indicators after heat treatment, with a tensile strength of ≥400MPa, a yield strength of ≥330MPa, and an elongation of ≥4%, indicating that the aluminum alloy die-castings produced by the die-casting method of the present invention have low porosity and high density.

[0136] In Comparative Example 1, the Si element content is low, the fluidity of the aluminum alloy liquid after smelting is reduced, the shrinkage compensation effect during the solidification process of the casting is poor, and the mechanical properties of the casting after heat treatment are reduced; the Cu element content in Comparative Example 2 does not meet the requirements of the present invention, and the Mg element content in Comparative Example 3 does not meet the requirements of the present invention; in Comparative Example 4, the thickness of the die-casting mold inlet gate is small, and the inlet gate thickness and the gate thickness ratio do not meet the requirements of the present invention, which is not conducive to providing more molten metal during the solidification process of the casting to compensate for the shrinkage inside the casting; in Comparative Example 5, the amount of refining modifier added is small, and grain refinement cannot be achieved; in Comparative Example 6, the casting pressure is low, and the solidification shrinkage compensation effect is poor; all of these lead to a decrease in the mechanical properties of the casting.

[0137] In summary, the present invention solves the problems of shrinkage porosity, shrinkage cavities and other defects that are often prone to occur in thick-walled aluminum alloy die-castings, thereby improving the density of the aluminum alloy die-castings, meeting the requirements of subsequent heat treatment, and making the aluminum alloy die-castings meet the use requirements; the aluminum alloy die-castings prepared by the present invention have a dense structure and low porosity, and have excellent strength and plasticity indicators after heat treatment, with a tensile strength of ≥400MPa, a yield strength of ≥330MPa, and an elongation of ≥4%.

[0138] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A die casting method for improving the density of a casting, characterized in that: The following steps are involved: Step 1, adding aluminum alloy metal raw materials into a preheated smelting furnace, melting and heating to obtain aluminum alloy liquid, and adding a refining modifier to the aluminum alloy liquid and stirring; Step 2, degassing the aluminum alloy liquid prepared in step 1, and removing the surface scum after standing; Step 3, preheating the die-casting mold, and evenly spraying a layer of release agent on the inner surface of the die-casting mold cavity; Step 4, cooling the aluminum alloy liquid treated in step 2, pouring it into the inlet gate of the die-casting mold treated in step 3, the inlet gate thickness is 8-12 mm, and using an injection punch to slowly inject the aluminum alloy liquid into the cavity of the die-casting mold; Step 5: Open the die-casting mold, take out the aluminum alloy die-casting from the cavity, place the die-casting in a water tank for quenching, and obtain a high-density die-casting.

2. The method according to claim 1, characterized in that In step 1, the composition of the aluminum alloy components is as follows by mass percentage: Si: 11-13.5%, Cu: 0.5-1.3%, Mg: 0.8-1.2%, Ni: 0.5-1.3%, Mn: 0.01-0.05%, Ti: 0.01-0.05%, Fe: 0.02-1.0%, and the rest is Al.

3. The method according to claim 1, characterized in that In step 1, the aluminum alloy metal raw material is melted and heated to 710-730°C.

4. The method according to claim 1, characterized in that: In step 1, the refining modifier is a mixture of aluminum-titanium-boron master alloy and aluminum-strontium master alloy, and the aluminum-titanium-boron master alloy and the aluminum-strontium master alloy account for 0.1-0.4% of the total mass of the alloy respectively.

5. The method according to claim 1, characterized in that In step 2, degassing is performed by rotary blowing of argon.

6. The method according to claim 5, characterized in that The degassing time is 20-30 minutes, the argon flow rate is 1-5 L / min, and the mixture is left to stand for 20-30 minutes.

7. The method according to claim 1, characterized in that The die-casting mold preheating temperature in step 3 is 150-200°C.

8. The method according to claim 1, characterized in that In step 4, the aluminum alloy liquid is cooled to 670-690°C.

9. The method according to claim 1, characterized in that: In step 4, the injection speed is 0.05-1.2 m / s, the casting pressure is 110-150 MPa, and the holding time is 2-10 s.

10. The method according to claim 1, characterized in that In step 5, the quenching temperature is 30-60°C.

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