CN116179903A - Low-carbon heat-free high-pressure cast aluminum alloy - Google Patents

Abstract

The application discloses low carbon exempts from heat treatment's high pressure casting aluminum alloy, low carbon exempts from heat treatment's high pressure casting aluminum alloy includes: 6.0 to 7.5 weight percent silicon; 0.15 to 0.3 wt% iron; 0.02 to 0.1 weight percent copper; 0.02 to 0.15 wt% zinc; 0.4 to 0.6 wt% manganese; 0.02 to 0.15% by weight of chromium; 0.1 to 0.4 weight percent magnesium; 0.02 to 0.1 wt.% vanadium; 0.02 to 0.1 wt% titanium; 0.01 to 0.03 weight percent gallium; 0.01 to 0.03 weight percent strontium; 0.02 to 0.3 weight percent of rare earth single impurity element is at most 0.03 weight percent, and the balance is aluminum, wherein Fe+Mn is 1.5+Cr+2+V is 2.5 and is more than 1.3 and less than 1.6.

Description

Low carbon high pressure casting aluminum alloy without heat treatment

Technical Field

The invention relates to the field of high-pressure cast aluminum alloys, in particular to a low-carbon, heat-treatment-free high-pressure cast aluminum alloy.

Background Art

With the development of new energy vehicles, lightweight design has become a trend in the development of new energy vehicles. Studies have shown that for every 100kg weight reduction of new energy vehicles, the driving range can be increased by 10%-11%, and the battery cost and daily loss cost can be reduced by 20%.

As the preferred material for lightweight automobiles, aluminum alloy has the advantages of weight reduction, energy conservation, environmental protection, recyclability, good corrosion resistance, and improved vehicle driving balance and safety. Die-casting parts have shifted from functional parts to structural parts, and the development trend tends to be thin-walled parts, integrated, and structurally complex integrated die-casting parts, which require high strength and high elongation of the materials so that the parts will not crack when riveted. However, many die-casting structural parts currently require heat treatment to meet performance requirements, but there are many uncontrollable factors in the heat treatment process, which will eventually lead to deformation of die-casting structural parts after heat treatment, low yield, and high cost. Tesla's use of heat-treatment-free materials to die-cast automotive structural parts has gradually emerged, but in the heat-treatment-free materials currently used, the iron content is controlled very low to ensure the plasticity of the material, making it difficult to use recycled aluminum for production.

With the in-depth promotion of carbon peak and carbon neutrality policies, carbon emission indicators have been continuously lowered. Recycled aluminum has shown the obvious advantage of low energy consumption, and has gotten rid of the aluminum industry's dependence on "price increases with electricity". Taking recycled aluminum as a leading industry is more conducive to the healthy, stable and long-term development of the aluminum industry. The carbon emissions of recycled aluminum are significantly lower than those of thermal electrolytic aluminum. One ton of thermal electrolytic aluminum emits about 12 tons of carbon dioxide, while the production of one ton of recycled aluminum only emits about 300 kg of carbon dioxide. The production of one ton of recycled aluminum saves 3.4 tons of standard coal, 14 cubic meters of water, and reduces solid waste emissions by 20 tons. Calculated based on the emission of 3 tons of carbon dioxide per ton of standard coal, plus the carbon emissions of other auxiliary materials, one ton of recycled aluminum can reduce carbon dioxide emissions by about 11.5 tons in total. At the same time, recycled aluminum has significant economic benefits. The production of primary aluminum involves the mining of bauxite and long-distance transportation. Alumina consumes a lot of energy in the process of electrolysis by thermal power, hydropower or wind power. In particular, thermal power is currently the main energy supply. The price of primary aluminum produced by wind power or hydropower is generally 300-700 yuan higher than that of thermal power aluminum. The cost is high and the supply is unstable. Therefore, the heat-treatment-free material produced by recycled aluminum is the current trend of integrated die castings.

Summary of the invention

One advantage of the present invention is to provide a low-carbon, heat-treatment-free high-pressure cast aluminum alloy, wherein the high-pressure cast aluminum alloy has a tensile yield limit Rp0.2 of >120MPa in the cast state, an elongation at break A of >13.0%, and a tensile strength Rm of >240MPa, and in particular, the raw material of the high-pressure cast aluminum alloy is produced from recycled aluminum and the die-cast parts do not require heat treatment.

An advantage of the present invention is to provide a low-carbon, heat-treatment-free high-pressure casting aluminum alloy, wherein the high-pressure casting aluminum alloy is produced from recycled aluminum and has higher hardness and plasticity.

In order to achieve at least one of the above advantages, the present invention provides a low-carbon high-pressure casting aluminum alloy that does not require heat treatment, wherein the high-pressure casting aluminum alloy that does not require heat treatment comprises:

6.0-7.5 wt% silicon;

0.15-0.3 wt.% iron;

0.02-0.1 wt. % copper;

0.02-0.15 wt. % zinc;

0.4-0.6% by weight of manganese;

0.02-0.15 wt. % chromium;

0.1-0.4 wt% magnesium;

0.02-0.1 wt. % vanadium;

0.02-0.1 wt.% titanium;

0.01-0.03 wt.% gallium;

0.01-0.03 wt% strontium;

0.02-0.3 wt% rare earth, a single impurity element is at most 0.03 wt%, the rest is aluminum, of which Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.3 and less than 1.6;

According to an embodiment of the present invention, the iron content is 0.15-0.3 wt %.

According to one embodiment of the present invention, the rare earth content is 0.02 to 0.3% by weight.

According to an embodiment of the present invention, the rare earth is selected from at least one of lanthanum, cerium and erbium.

According to an embodiment of the present invention, the heat treatment-free high pressure casting aluminum alloy includes 0.02-0.1 wt % copper.

According to an embodiment of the present invention, the heat treatment-free high pressure casting aluminum alloy includes 0.4-0.6 weight % manganese.

According to an embodiment of the present invention, the heat treatment-free high pressure casting aluminum alloy includes 0.02-0.1 wt % nickel.

According to an embodiment of the present invention, the heat treatment-free high pressure casting aluminum alloy includes 0.02-0.15 wt % zinc.

According to an embodiment of the present invention, the heat treatment-free high pressure casting aluminum alloy includes 0.02-0.1 wt % of vanadium.

According to one embodiment of the present invention, Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.3 and less than 1.6;

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a metallographic image of a low-carbon aluminum alloy die-casting part body sample;

DETAILED DESCRIPTION

The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and the summary of the invention is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

The low-carbon heat-treatment-free high-pressure casting aluminum alloy comprises:

6.0-7.5 wt% silicon;

0.15-0.3 wt.% iron;

0.02-0.1 wt. % copper;

0.02-0.15 wt. % zinc;

0.4-0.6% by weight of manganese;

0.02-0.15 wt. % chromium;

0.1-0.4 wt% magnesium;

0.02-0.1 wt. % vanadium;

0.02-0.1 wt.% titanium;

0.01-0.03 wt.% gallium;

0.01-0.03 wt% strontium;

0.02-0.3 wt% rare earth, a single impurity element is at most 0.03 wt%, the rest is aluminum, of which Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.3 and less than 1.6;

It is worth mentioning that the content of iron in high pressure cast aluminum alloy is at most 0.3% by weight, and preferably 0.2-0.3% by weight, because it can maximize the use of recycled aluminum. In addition, the increase in iron content can improve the strength of the cast aluminum alloy, but it will reduce the plasticity of the cast aluminum alloy.

The addition of Mn can change the morphology of the β-Fe phase and turn it into α-AlFeSi. This is because Mn and Fe have similar atomic radii. Therefore, Mn can be replaced by Fe, and the β-Fe phase can be transformed into α-AlFeSi. If excessive Mn is added continuously, large pieces of α-AlFeSi will also be formed, which is considered to be sludge and is not conducive to the mechanical properties of the alloy. It can be seen that Mn causes the transformation of β-AlFeSi to α-AlFeSi, so the manganese content is controlled within 0.5-0.6 weight%, but it is difficult to integrate the excessive Fe phase in the aluminum alloy;

The added Cr forms intermetallic compounds such as (CrFe) _Al7 and (CrMn) _Al12 in aluminum, which hinder the nucleation and growth process of recrystallization, have a certain strengthening effect on the alloy, and can also improve the toughness of the alloy and reduce the sensitivity of stress corrosion cracking. Excessive addition of chromium will increase the sludge index in the aluminum alloy, resulting in an increase in furnace bottom sediments, affecting product quality. The preferred Cr content is between 0.07 and 0.13 weight percent.

The proportion of vanadium in aluminum alloy is up to 0.1% by weight. The addition of vanadium makes the average length of β-Fe phase gradually decrease with the increase of V content. This is because the addition of V generates AlSiVFe phase with Al, Si and part of Fe, that is, the addition of V consumes part of Fe. In the presence of manganese, V spheroidizes the fishbone-shaped α-AlFeMnSi and improves the plasticity of the material. When the V content is low or absent, the use of recycled aluminum of the material is limited. The use of recycled aluminum to produce high iron content cannot guarantee the plasticity of the material.

It is worth mentioning that the addition of the rare earth elements can increase the recrystallization temperature of the alloy and significantly refine the grains.

Especially for the wall thickness of large castings of cast aluminum alloys, rare earth elements can refine the size of the aluminum matrix and improve the morphology of the iron phase, thereby increasing the tensile strength, elongation and hardness of the product.

In summary, the main effect of adding manganese, chromium, vanadium and rare earth is to change the iron phase in the aluminum alloy produced by recycled aluminum, and reduce the influence of high iron content of recycled aluminum on the elongation of the material. However, considering the precipitation of heavy metal manganese, chromium and vanadium compounds and the complete change of needle-shaped iron phase during the use of the material, Fe+Mn*1.5+Cr*2+V*2.5 is controlled to be greater than 1.3 and less than 1.6;

After controlling Fe+Mn*1.5+Cr*2+V*2.5 to be greater than 1.3 and less than 1.6, if it is lower than 1.3, mold sticking will occur during the high-pressure casting process and casting cannot be produced. If it is higher than 1.6, excessive iron, manganese, chromium and vanadium will produce more metal compounds with high melting points and higher than aluminum, resulting in precipitation during the production process, component segregation and inability to produce.

In addition, in the above-mentioned embodiment, in the high-pressure cast aluminum alloy, the proportion of silicon in the high-pressure cast aluminum alloy is 6.0-7.5% by weight. The die-cast aluminum alloy within this range belongs to a hypoeutectic aluminum alloy, which has excellent natural aging and good fluidity after die-casting, and the tendency of castings to hot cracking is extremely small.

By adding 0.01-0.1 wt % copper and 0.02-0.15 wt % zinc, copper and zinc form a strengthening phase in the aluminum alloy, which can improve the strength and hardness of the material, but will reduce the elongation of the material. Limiting the elongation of the material to a certain range can maximize the use of recycled aluminum while taking into account the elongation of the material.

Especially in the high pressure casting aluminum alloy mentioned above, when the proportion of magnesium in the high pressure casting aluminum alloy is 0.1-0.4 weight %, magnesium can enhance the strength and hardness of the alloy, because adding a small amount of magnesium to the aluminum silicon alloy can form a _Mg2Si phase, and the specific content of magnesium can be adjusted according to the practical requirements of material properties, but the elongation will decrease as the magnesium content increases.

According to the test, for every 0.1% increase in magnesium content, the tensile strength and yield strength will increase by 5Mpa to 10Mpa, but the elongation will decrease by 1% to 2.5%.

The proportion of titanium in cast aluminum alloy is 0.02-0.1% by weight. Titanium can be added in the form of AlTi alloy and AlTiB. Titanium and aluminum produce AlTi ₃ , which can play a role in refining grains. However, the increase in titanium content will cause aluminum liquid to segregate and precipitate when it is stationary, and will reduce the fatigue strength of the product.

The addition of strontium can modify the morphology of eutectic silicon and avoid the formation of coarse flaky silicon phases. In other words, after adding strontium, fine rod-shaped eutectic silicon structure can be formed. Therefore, the modified eutectic silicon has a great influence on the mechanical properties of casting products, especially it can greatly improve the elongation at break.

According to another aspect of the present invention, the present invention provides a method for preparing a low-carbon heat-treatment-free high-pressure casting aluminum alloy, wherein the method for preparing a low-carbon heat-treatment-free high-pressure casting aluminum alloy comprises:

S1, melting the recycled aluminum raw material and controlling the aluminum liquid temperature between 710 and 730°C;

S1, according to the low carbon heat-free high pressure casting aluminum alloy including the following components:

6.0-7.5 wt% silicon;

0.15-0.3 wt.% iron;

0.02-0.1 wt. % copper;

0.02-0.15 wt. % zinc;

0.4-0.6% by weight of manganese;

0.02-0.15 wt. % chromium;

0.1-0.4 wt% magnesium;

0.02-0.1 wt. % vanadium;

0.02-0.1 wt.% titanium;

0.01-0.03 wt.% gallium;

0.01-0.03 wt% strontium;

0.02-0.3 wt% rare earth, a single impurity element is at most 0.03 wt%, the rest is aluminum, where Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.0 and less than 1.6;

adding the components into the filtrate and melting the added components by heating the aluminum liquid;

S2, pressing a sodium-free refining agent into the aluminum alloy through a degasser for refining, adding an aluminum-strontium master alloy containing 0.01 to 0.03 weight percent of strontium during refining, and refining for a predetermined time to remove gas from the aluminum liquid;

S3, detecting the gas content by a hydrogen meter, and when the gas content reaches below 0.15 ml/100 g, die-casting is performed by an aluminum alloy high-pressure casting device to form the low-carbon high-pressure casting heat-treatment-free aluminum alloy.

Preferably, the method for producing aluminum alloy by high pressure casting without heat treatment comprises the steps of:

S4, material preparation and furnace cleaning: prepare materials according to the alloy composition ratio, and clean the furnace after material preparation.

It is worth mentioning that the alloying elements are added in the form of pure alloys or master alloys.

For example, the Cu element is added in the form of Al-Cu master alloy, the Si element is added in the form of elemental 3303 silicon, the Mg element is added in the form of pure Mg ingot, the Mn element is added in the form of Al-Mn master alloy, the Ti element is added in the form of Al-Ti master alloy, the Cr element is added in the form of a master alloy, the Sr element is added in the form of a Sr master alloy, the V element is added in the form of a V master alloy, and rare earth elements such as lanthanum, cerium, and scandium are added in the form of master alloys.

In the melting aluminum ingot, after the surface of the recycled aluminum raw material is cleaned, the pure aluminum ingot and 3303 silicon are placed in a resistance crucible for heating and melting, and the aluminum liquid temperature is controlled between 710 and 730°C;

When adding the master alloy: when the temperature of the aluminum liquid reaches 720℃, add the dried Al-Cu master alloy, magnesium ingot, Al-Ti and other master alloys into the aluminum liquid, heat the aluminum liquid to 740℃, and keep it warm for 15 minutes to ensure that all the added master alloys are melted;

During refining, modification and degassing, when the temperature of the aluminum liquid drops to 710-730℃, the aluminum alloy sodium-free refining agent is pressed into the mobile rotary degasser for refining, and the aluminum strontium master alloy is added during refining. The refining time is set. Preferably, it is 10-30 minutes, and then the slag is removed and the mixture is allowed to stand. If the mixture is allowed to stand for 1 hour, the gas content is detected by an online hydrogen meter after standing. If the gas content reaches 0.15ml/100g or less, die casting is performed. If the requirement is not met, the above refining, modification and degassing process is continued.

Die casting production verification:

1) Production equipment and auxiliary accessories: 280T LK die-casting machine, automatic ladle feeder, mold temperature controller, brand vacuum machine, imported mold release agent for die-casting structural parts on the market, imported granular beads, 3mm*80mm*250mm self-made test piece mold (Figure 1), 50mm punch and melting cup;

2) Die-casting process control: The temperature of die-casting aluminum liquid is controlled at 680-690℃, the temperature of the mold temperature controller is controlled at 160～170℃, the high speed is controlled at 2.7-2.9m/S, the vacuum degree is controlled between 10～40mbar, and the boost pressure is 65Mpa;

3) The following are the performance tests of die-casting test pieces with different composition ratios after cutting according to GBT228 standard test piece wire using Sansi tensile testing machine and imported extensometer.

The high pressure cast aluminum alloys of the five embodiments were respectively manufactured by the above-mentioned preparation process, and their properties were tested, as shown in Table 1 below.

Table 1

It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims (10)

1. The high-pressure cast aluminum alloy of low-carbon heat-free treatment, it is characterized in that, the high-pressure cast aluminum alloy of described low-carbon heat-free treatment comprises: 6.0-7.5% by weight of silicon; 0.15-0.3% by weight of iron; 0.02-0.1 wt% copper; 0.02-0.15% by weight of zinc; 0.4-0.6% by weight of manganese; 0.02-0.15% by weight of chromium; 0.1-0.4% by weight of magnesium; 0.02-0.1% by weight of vanadium; 0.02-0.1% by weight of titanium; 0.01-0.03% by weight of gallium; 0.01-0.03% by weight strontium; 0.02-0.3% by weight of rare earth, a single impurity element is at most 0.03% by weight, and the rest is aluminum, wherein Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.3 and less than 1.6. 2. The low-carbon heat-free high-pressure cast aluminum alloy according to claim 1, characterized in that the iron content is 0.15-0.3% by weight. 3. The low-carbon heat-free high-pressure cast aluminum alloy according to claim 1, characterized in that the content of the rare earth is 0.02-0.3% by weight. 4. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1 to 3, wherein the rare earth is selected from at least one of lanthanum, cerium, and scandium. 5. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1-3, characterized in that the heat-free high-pressure cast aluminum alloy includes 0.02-0.1% by weight of copper. 6. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1-3, characterized in that the heat-free high-pressure cast aluminum alloy includes 0.4-0.6% by weight of manganese. 7. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1-3, characterized in that the heat-free high-pressure cast aluminum alloy includes 0.02-0.15% by weight of chromium. 8. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1-3, characterized in that the heat-free high-pressure cast aluminum alloy includes 0.02-0.15% by weight of zinc. 9. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1-3, characterized in that the heat-free high-pressure cast aluminum alloy includes 0.02-0.1% by weight of titanium. 10. The low-carbon heat-free high-pressure cast aluminum alloy according to any one of claims 1 to 3, characterized in that Fe+Mn*1.5+Cr*2+V*2.5 is greater than 1.3 and less than 1.6.

Images