introduce

In the complex field of automotive manufacturing, die casting plays a vital role, especially in manufacturing high-performance automotive components. This guide takes an in-depth look at the world of die-cast automotive parts, revealing its applications, benefits, and technological innovations that are driving the automotive industry forward.

Enhance your automotive knowledge: Explore die casting applications

Understand die casting in automobile manufacturing

The evolution of die casting technology

Die-casting technology continues to develop and evolve over time to adapt to the needs and changes in the automotive manufacturing industry. Here’s how die-casting technology has evolved in automotive manufacturing:

• Initial stage: Early die-casting technology was mainly used to produce small, simple metal parts. Due to the small scale of the die-casting machine, the parts produced are also relatively small in size. Die-casting technology at this stage mainly focuses on improving production efficiency and reducing costs.
• Mature stage: With the development of the automobile industry, the demand for die-cast parts is gradually increasing. Die-casting machines are gradually becoming larger and more complex, capable of producing larger and more complex parts. At the same time, various aspects of die-casting technology have also been improved and optimized, such as mold design, material selection, production technology, etc.
• Innovation stage: In recent years, with the continuous advancement and innovation of science and technology, die-casting technology has also undergone many changes. For example, new die-casting materials such as aluminum, magnesium and other lightweight materials are widely used to improve the quality and performance of parts. At the same time, innovations in die-casting technology also include digital twin technology, 3D printing and other technologies, which can realize the manufacturing of complex-shaped parts and improve production efficiency and quality.

Die-casting technology has experienced multiple stages of development and evolution in automobile manufacturing. From traditional die-casting methods to modern innovative processes, die-casting technology is constantly improving to adapt to the needs and changes of the automotive manufacturing industry. In the future, with the continuous advancement and innovation of science and technology, die-casting technology will continue to develop and evolve, bringing more opportunities and challenges to the automobile manufacturing industry.

The Importance of Auto Parts Precision

In automotive parts manufacturing, precision is a crucial factor. For die-casting technology, precision directly affects the quality, performance and safety of parts. Here’s how precision plays a key role in die-cast automotive parts:

1. Quality Assurance: Precision is a key factor in ensuring the quality of die-cast parts. During the die-casting process, the design and manufacturing accuracy of the mold, the control and filling of materials, the adjustment of pressure and temperature, etc. all need to be precisely controlled to ensure that the dimensional accuracy and surface quality of the final product meet the requirements. Only by reaching a certain level of accuracy can the reliability and service life of components be guaranteed.
2. Performance improvements: Precision also directly affects the performance of die-cast parts. For example, high-precision die-cast parts can reduce friction and wear, improve transmission efficiency and service life. In addition, precision can also improve the strength, stiffness and fatigue resistance of components, thereby improving the overall performance of the vehicle.
3. Safety guarantee: The precision of die-cast auto parts is also directly related to the safety of the vehicle. For example, high-precision braking system components can ensure the accuracy and timeliness of braking, and improve the braking performance and safety of vehicles. In addition, precision can also ensure the safe operation of other key components such as engines, gearboxes, etc., and avoid safety issues caused by component failures.
4. Reduce costs: By improving the precision of die-cast parts, the difficulty and time of subsequent processing and trimming can be reduced, and production costs can be reduced. At the same time, high-precision parts can also reduce scrap and repair rates, thereby reducing overall operating costs.
5. Realization of innovative designs: High-precision die-casting technology can support more complex and sophisticated automotive parts design. Designers can integrate more innovative ideas into product design to achieve more efficient, lightweight and high-performance automotive parts.

Precision plays a vital role in die-cast automotive parts. By improving the level of precision control of the die-casting process, the quality, performance and safety of parts can be ensured, production costs can be reduced, and the realization of innovative designs can be supported. Therefore, for die-casting technology, continuously improving precision is an important way to achieve the sustainable development of the automotive manufacturing industry.

Materials shaping the future: die-cast alloys

Die-cast alloys play a vital role in automotive manufacturing, as they directly impact the durability, strength and overall performance of automotive components. Here are some commonly used die casting alloys and their characteristics:

• Aluminum alloy: Aluminum alloy is one of the most commonly used alloys in die casting. It has the advantages of light weight, corrosion resistance, and good thermal conductivity. In automobile manufacturing, aluminum alloys are widely used to manufacture automobile parts, such as engine parts, braking system parts, etc. The strength and hardness of aluminum alloys are relatively low, but can be improved through heat treatment and the addition of alloying elements.
• Zinc Alloy: Zinc alloy is a relatively inexpensive die-cast alloy with good casting properties and corrosion resistance. In automobile manufacturing, zinc alloy is mainly used to make appearance parts and decorative parts, such as wheels, door trims, etc. Zinc alloys have relatively low strength and hardness, making them unsuitable for use in the manufacture of load-bearing components.
• Magnesium alloy: Magnesium alloy is a lightweight, high-strength die-cast alloy with good casting properties and corrosion resistance. In automobile manufacturing, magnesium alloys are widely used to manufacture load-bearing parts and appearance parts, such as hoods, doors, etc. Magnesium alloy has higher strength and hardness than aluminum alloy and zinc alloy, but the cost is also relatively high.
• Steel Alloy: Steel alloy is a die-cast alloy with high strength, high hardness and good corrosion resistance. In automobile manufacturing, steel alloys are mainly used to make load-bearing parts and safety parts, such as frames, airbags, etc. The cost of steel alloys is relatively low, but the casting performance is poor and the casting process needs to be strictly controlled.

When selecting a die-casting alloy, factors such as the use of the parts, performance requirements, and cost need to be considered. Different alloys have different advantages and disadvantages and need to be selected according to actual conditions. For example, for load-bearing parts that require high strength and corrosion resistance, you can choose magnesium alloys or steel alloys; for decorative parts that require good casting performance and beautiful appearance, you can choose zinc alloys or aluminum alloys.

In summary, die-cast alloys are an integral part of automobile manufacturing. Different alloys have different characteristics and application ranges, and they need to be selected according to actual conditions. With the continuous advancement and innovation of science and technology, future die-cast alloys will be more efficient, environmentally friendly and sustainable, bringing more opportunities and challenges to the automobile manufacturing industry.

Applications in the automotive industry

Engine components: providing power performance

Die-casting technology plays an important role in the manufacture of engine components and can increase the power and efficiency of internal combustion engines. The following are the applications of die casting in engine components:

1. Cylinder Head: The cylinder head is an important part of the engine that encloses the cylinder and houses the piston. Die-casting technology can be used to manufacture cylinder heads. Through high-precision mold and material control, it can be ensured that the size and shape accuracy of the cylinder head meet the requirements. Die-cast cylinder heads are lightweight and high-strength to increase engine power and efficiency.
2. Piston: The piston is one of the core components of the engine, and together with the cylinder, it forms the combustion chamber. Die-casting technology can be used to manufacture pistons, achieving lightweightness and miniaturization of the pistons through precise mold and material control. Die-cast pistons offer high strength, corrosion resistance and good thermal conductivity, which improves engine performance and reliability.
3. Crankshaft: The crankshaft is a key component in the engine, used to transmit power and drive the piston movement. Die-casting technology can be used to manufacture crankshafts, achieving high strength, lightweight and corrosion resistance through high-precision mold and material control. Die-cast crankshafts increase engine power and efficiency and reduce fuel consumption.
4. Camshaft: The camshaft is an important component in the engine and is used to control the opening and closing of the valves. Die-casting technology can be used to manufacture camshafts, achieving high precision and miniaturization through precise mold and material control. Die-cast camshafts offer high strength, corrosion resistance and good thermal conductivity, which improves engine performance and reliability.
5. Flywheel: The flywheel is an important component in the engine and is used to store and release kinetic energy. Die-casting technology can be used to manufacture flywheels, achieving high strength, lightweight and corrosion resistance through precise mold and material control. Die-cast flywheels improve engine efficiency and fuel economy.

Transmission Housing: Seamless Power Transmission

Die casting plays an important role in the manufacture of gearbox housings. Through precision casting, high-quality, high-efficiency gearbox housings can be produced, helping to achieve seamless power transmission and optimizing the performance of automotive gearboxes.

First, die casting can produce gearbox housings with complex shapes and structures. Due to the good fluidity and filling ability of the molten metal during the die-casting process, thin-walled and complex structures can be manufactured, achieving lightweight and efficient production. This complex structure can improve the performance of the gearbox and increase transmission efficiency.

Secondly, the gearbox housing produced by die-casting has high precision and stable quality. Precision casting technology can ensure precise control of casting dimensions, thereby ensuring assembly accuracy and performance of the gearbox. In addition, the uniform filling and solidification of molten metal during the die-casting process can reduce defects such as stress concentration and shrinkage cavities, and improve the reliability and service life of the gearbox.

Finally, the die-cast gearbox housing enables customized production. Different car models and brands have different requirements for the performance and design of gearboxes, and die-casting technology can customize production according to different needs. This flexibility allows automakers to quickly adjust production plans based on market demand to meet the needs of different customers.

Chassis and Structural Components: Balancing Strength and Weight

Die casting plays an important role in the manufacture of chassis and structural components to achieve the perfect balance between strength and weight, which is crucial for vehicle safety and stability.

First, die casting can produce high-strength chassis and structural components. Due to the good fluidity and filling ability of the molten metal during the die-casting process, components with thin walls and complex structures can be manufactured, achieving lightweight and efficient production. At the same time, the uniform filling and solidification of molten metal during the die-casting process can reduce defects such as stress concentration and shrinkage cavities, and improve the strength and reliability of components. This high-strength chassis and structural component improves vehicle safety and stability.

Second, die casting can produce chassis and structural components with complex structures and precise dimensions. Precision casting technology can ensure precise control of casting dimensions, thereby ensuring assembly accuracy and performance of components. This precise size and structure reduces friction and vibration between components, improving vehicle stability and comfort.

In addition, die casting also has the capability of mass production. Due to the good fluidity and filling properties of the molten metal during the die-casting process, multiple parts can be manufactured and mass production can be achieved. This mass production capability can reduce production costs and improve production efficiency while meeting market demand for vehicle chassis and structural components.

Finally, die casting also enables customized production. Different vehicle models and brands have different requirements for the performance and design of chassis and structural components, and die-casting technology can customize production according to different needs. This flexibility allows automakers to quickly adjust production plans based on market demand to meet the needs of different customers.

3. Surface treatment technology

Die-casting surface treatment technology is critical to improving the aesthetics and corrosion resistance of automotive components. The following are several commonly used surface treatment technologies:

1. Shot peening: Shot peening is a surface strengthening process that sprays projectiles onto the surface of the workpiece through high-speed airflow, causing plastic deformation on the surface of the workpiece, thereby improving the fatigue strength and corrosion resistance of the workpiece. Shot peening can be applied to die-cast automotive parts, such as cylinder heads, pistons, etc., to enhance their corrosion resistance and aesthetics.
2. Powder spraying: Powder spraying is a commonly used surface coating process. The powder coating is evenly sprayed onto the surface of the workpiece through electrostatic spraying or fluidized bed spraying to form a dense coating. Powder coating can be applied to die-cast automotive parts, such as body panels, wheels, etc., to improve their corrosion resistance and aesthetics.
3. Electroplating: Electroplating is a process that deposits metal onto the surface of a workpiece through the principle of electrolysis. It can form a layer of metal coating with special properties on the surface of the workpiece. Electroplating can be applied to die-cast automotive parts, such as bushings, gears, etc., to improve their corrosion resistance and wear resistance.
4. Anodizing: Anodizing is a process that oxidizes the metal surface into an oxide film through the principle of electrolysis. It can form a dense oxide film on the metal surface to improve the corrosion resistance and aesthetics of the metal. Anodizing can be applied to die-cast automotive parts, such as aluminum alloy parts, to improve their corrosion resistance and aesthetics.

Die-casting surface treatment technology is critical to improving the aesthetics and corrosion resistance of automotive components. Different surface treatment technologies have different characteristics and application ranges, and need to be selected according to actual conditions. With the continuous advancement and innovation of science and technology, future surface treatment technology will be more efficient, environmentally friendly and sustainable, bringing more opportunities and challenges to the automobile manufacturing industry.

4. Frequently Asked Questions

What materials are commonly used for die-cast auto parts?
Aluminum, zinc and magnesium alloys are commonly used for die-cast automotive parts due to their lightweight nature and excellent mechanical properties.

How do die castings improve vehicle fuel efficiency?
The precision and lightweight properties of die-cast components help reduce vehicle weight and improve fuel efficiency by reducing energy consumption.

Are die-cast auto parts environmentally friendly?
Yes, die casting is an environmentally friendly process as it minimizes waste and the materials used are recyclable and consistent with sustainable manufacturing practices.

Can die castings be used for electric vehicle parts?
Of course, die casting is widely used in the manufacture of electric vehicle parts, contributing to their lightweight design and overall efficiency.

How do die castings ensure the safety of automobile structural parts?
The precision of the die-cast parts ensures that the structural components meet strict safety standards, providing durability and reliability in a variety of driving conditions.

What advancements are expected in die-casting technology for automotive applications?
Continuing advancements in die-casting technology include improved alloy formulations, increased automation, and increased efficiency in the production of complex parts.

Conclusion: Promoting the future of excellent automobiles

To sum up, die-cast automotive parts have become the backbone of modern automotive manufacturing, embodying precision, efficiency and innovation. As the automotive industry evolves, the role of die casting continues to drive excellence and shape the vehicles of the future.

The post Die-cast automotive parts: revolutionizing vehicle performance first appeared on MindWell.

Cast aluminum alloys can be divided into five categories according to the main elements they contain: cast aluminum-silicon alloys, cast aluminum-copper alloys, cast aluminum-magnesium alloys, cast aluminum-zinc alloys, and cast aluminum rare earth alloys. Among them, cast aluminum-silicon alloy and cast aluminum-copper alloy are commonly used.

The expression method of cast aluminum alloy code is different from that of copper-gold alloy. It expresses a certain aluminum alloy with a certain numerical code. For example ZL101, where ZL means cast aluminum. The first number in the three numbers indicates aluminum alloys with different chemical compositions, 1 is aluminum-silicon alloy, 2 is aluminum-copper alloy, 3 is aluminum-magnesium alloy, 4 is aluminum-zinc alloy, and the following two numbers indicate different codes of the same aluminum alloy.

Composition of commonly used cast aluminum alloys

• Aluminum-silicon alloys, also known as “silicon-aluminum” or “silicon-aluminum”. It has good casting performance and wear resistance, and has a small thermal expansion coefficient. It has the most varieties and the largest amount of alloys in cast aluminum alloys. The silicon content is 4% to 13%. Sometimes 0.2% ~ 0.6% magnesium is added to silicon-aluminum alloy, which is widely used in structural parts, such as shells, cylinders, boxes and frames. Sometimes adding an appropriate amount of copper and magnesium can improve the mechanical properties and heat resistance of the alloy. Such alloys are widely used in the manufacture of components such as pistons. the
• Aluminum-copper alloy, the alloy containing 4.5% to 5.3% copper has the best strengthening effect, and the addition of manganese and titanium can significantly improve the room temperature, high temperature strength and casting performance. It is mainly used to make sand castings with large dynamic and static loads and uncomplicated shapes. the
• Aluminum-magnesium alloy, the cast aluminum alloy with the lowest density (2.55g/cm3) and the highest strength (about 355MPa), containing 12% magnesium, has the best strengthening effect. The alloy has good corrosion resistance in the atmosphere and seawater, and has good comprehensive mechanical properties and machinability at room temperature. It can be used as radar bases, aircraft engine casings, propellers, landing gear and other parts, and can also be used as decorative materials. the
• Aluminum-zinc alloys, silicon and magnesium elements are often added to improve performance, often called “zinc-silicon-aluminum”. In the as-cast condition, the alloy has a quenching effect, that is, “self-quenching”. It can be used without heat treatment, and the casting has higher strength after metamorphic heat treatment. After stabilization treatment, the size is stable, and it is often used to make models, templates and equipment supports.

Cast aluminum alloys have the same alloy system as wrought aluminum alloys, and have the same strengthening mechanism as wrought aluminum alloys (except for strain strengthening). Their main difference is that the maximum content of alloying element silicon in cast aluminum alloys exceeds that of most wrought aluminum alloys. In addition to strengthening elements, the cast aluminum alloy must also contain a sufficient amount of eutectic elements (usually silicon) so that the alloy has considerable fluidity and is easy to fill the shrinkage gap of the casting during casting. At present, there are only the following 6 types of basic alloys：

• ① Al-Cu alloy
• ②Al-Cu-Si alloy
• ③ Al-Si alloy
• ④ Al-Mg alloy
• ⑤Al-Zn-Mg alloy
• ⑥ Al-Sn alloy

Defect analysis of aluminum alloy die casting

Oxidation slag

Defect characteristics: Oxidized slag inclusions are mostly distributed on the upper surface of the casting, in the corners of the mold that are not ventilated. The fracture is mostly off-white or yellow, which can be found by X-ray perspective or during mechanical processing, and can also be found during alkali cleaning, pickling or anodizing.

cause:

1. Furnace charge is not clean, excessive use of returned charge
2. Poor gating system design
3. The slag in the alloy liquid is not cleaned
4. Improper pouring operation, bringing in slag inclusions
5. Not enough standing time after refining and deterioration treatment

Prevention method:

1. Furnace charges should be sand blown, and the amount of returned charge should be appropriately reduced
2. Improve the gating system design and improve its slag retaining ability
3. Use appropriate flux to remove slag
4. When pouring, it should be stable and pay attention to slag blocking
5. After refining, the alloy liquid should be allowed to stand for a certain period of time before pouring

Stomatal bubbles

Defect characteristics: The pores in the wall of the three castings are generally round or oval, with a smooth surface, usually shiny oxide skin, sometimes oily yellow. Surface pores and bubbles can be found by sandblasting, and internal pores and bubbles can be found through X-ray perspective or mechanical processing, and the pores and bubbles appear black on the X-ray film.

cause:

1. Casting alloy is not stable, gas is involved
2. Organic impurities (such as coal dust, grass root horse manure, etc.) are mixed into the mold (core) sand
3. Poor ventilation of mold and sand core
4. Shrinkage cavity on cold iron surface
5. Poor gating system design

Prevention method:

1. Correctly grasp the pouring speed to avoid getting involved in gas.
2. The mold (core) sand shall not be mixed with organic impurities to reduce the gas generation of the molding material
3. Improved venting capacity of (core) sand
4. Proper selection and handling of cold iron
5. Improved gating system design

Shrinkage

Defect characteristics: Shrinkage porosity of aluminum castings generally occurs at the thick and large part of the root of the flying riser near the inner runner, the thickness transition of the wall and the thin wall with a large plane. The fracture is gray in the cast state, and light yellow after heat treatment, it is grayish white, light yellow or gray black, and it is cloudy on the X-ray film. Severe filamentous shrinkage can be found by inspection methods such as X-ray and fluorescence low-magnification fracture. the

cause:

1. Riser feeding effect is poor
2. Too much gas in the charge
3. Overheating near the ingate
4. The sand mold has too much moisture, and the sand core has not been dried
5. Coarse Alloy Grain
6. Improper position of the casting in the mold
7. The pouring temperature is too high and the pouring speed is too fast

Prevention method:

1. Replenishing molten metal from the riser to improve the design of the riser
2. Charge should be clean and free from corrosion
3. Riser is set at the shrinkage part of the casting, and chilled iron is placed or used in combination with chilled iron and riser
4. Moisture control of molding sand, and sand core drying
5. Take measures to refine the grain
6. Improve the position of the casting in the mold to reduce the pouring temperature and pouring speed

crack

Defect characteristics:

1. Casting cracks. Developing along the grain boundary, often accompanied by segregation, is a kind of crack formed at a higher temperature, which is prone to appear in alloys with larger volume shrinkage and castings with more complex shapes.
2. Heat treatment cracks: Transgranular cracks are often caused by heat treatment overburning or overheating. It is often caused by excessive cooling of alloys with large stress and thermal expansion coefficient. Or when there are other metallurgical defects Causes:
3. The structure design of the casting is unreasonable, there are sharp corners, and the thickness of the wall varies greatly.
4. Sand mold (core) yield poor
5. Local overheating of the mold
6. Pouring temperature is too high
7. Premature removal of casting from mold
8. Overheating or overheating in heat treatment, excessive cooling rate

Prevention method:

1. Improve the structural design of castings, avoid sharp corners, strive for uniform wall thickness, and smooth transition
2. Take measures to increase the yield of the sand mold (core)
3. Ensure simultaneous solidification or sequential solidification of all parts of the casting, and improve the design of the gating system
4. Appropriately reduce the pouring temperature
5. Control mold cooling time
6. The thermal correction method is used when the casting is deformed
7. Correctly control the heat treatment temperature and reduce the quenching cooling rate

Pore analysis

Among the defects of die castings, the most common ones are pores.

stomatal features. It has a smooth surface and is round or oval in shape. Manifestations can be on the surface of the casting, or subcutaneous pinholes, or inside the casting.

(1) Gas source

• 
  1) Alloy liquid precipitation gas—a is related to raw materials b is related to smelting process
  2) The gas involved in the die-casting process ¬—a is related to the die-casting process parameters b is related to the mold structure
• 3) The release agent decomposes to generate gas ¬—a is related to the characteristics of the coating itself b is related to the spraying process
  

(2) Analysis of raw materials and gases generated during the smelting process

The gas in molten aluminum is mainly hydrogen, accounting for about 85% of the total gas. the
The higher the smelting temperature, the higher the solubility of hydrogen in molten aluminum, but the solubility in solid aluminum is very low, so during the solidification process, hydrogen is precipitated to form pores. the

Source of Hydrogen:

• 1) Water vapor in the atmosphere, and the molten metal absorbs hydrogen from the humid air. the
• 2) The hydrogen content of the raw material itself, the surface of the alloy ingot is wet, and the returned material is dirty and oily. the
• 3) Tools and flux are wet. the

(3) Analysis of gas generated in the die casting process

Since the pressure chamber, gating system, and cavity are all connected to the atmosphere, and the molten metal is filled at high pressure and high speed, if an orderly and stable flow state cannot be achieved, the molten metal will generate eddy currents and gas will be involved.

The following issues need to be considered in the formulation of die casting process:

• 1) Whether the molten metal can flow cleanly and smoothly in the pouring system without separation and eddy current.
• 2) Are there sharp corners or dead zones?
• 3) Is there any change in the cross-sectional area of the gating system?
• 4) Is the position of exhaust groove and overflow groove correct? Is it big enough? Will it be blocked? Can the gas be discharged effectively and smoothly?

The application of computer to simulate the filling process is to analyze the above phenomena and make judgments to select reasonable process parameters.

(4) Gas analysis of coatings

Coating properties: If the gas generation is large, it will directly affect the porosity of the casting.
Spraying process: Excessive use, resulting in a large amount of gas volatilization, too much punch lubricant, or burnt, are all sources of gas.

(5) Ways to solve the porosity of die castings

First analyze what causes the pores, and then take corresponding measures.
1) Dry and clean alloy material.
2) Control the melting temperature, avoid overheating, and perform degassing treatment.
3) Reasonable selection of die-casting process parameters, especially injection speed. Adjust the starting point of high-speed switching.

4) Sequential filling is conducive to the discharge of gas from the cavity, and the sprue and runner have sufficient length (>50mm) to facilitate the smooth flow of the alloy liquid and the opportunity for gas to be discharged. The gate thickness and gate direction can be changed, and overflow grooves and exhaust grooves can be set at the positions where pores are formed. The sum of the cross-sectional areas of the overflow products should not be less than 60% of the sum of the cross-sectional areas of the ingates, otherwise the slagging effect will be poor.
5) Select paint with good performance and control the amount of spraying.

Solutions

Equipment adjustment

Since the cause of each defect comes from many different influencing factors, in order to solve the problem in actual production, in the face of many reasons, is it right to adjust the machine first? Or refuel first? Or modify the mold first? It is recommended to deal with it according to the degree of difficulty, first simple and then complex, in order:

• 1) Clean the parting surface, clean the cavity, and clean the ejector pin; improve the coating and spraying process; increase the clamping force and increase the amount of pouring metal. These measures can be implemented with simple operations. 2) Adjust process parameters, injection force, injection speed, filling time, mold opening time, pouring temperature, mold temperature, etc. the
• 3) Refueling, select high-quality aluminum alloy ingots, change the ratio of new materials to recycled materials, and improve the melting process. the
• 4) Modify the mold, modify the gating system, increase the inner gate, add overflow grooves, exhaust grooves, etc. For example, the causes of flashing in die castings are:

1) Die casting machine problem: The clamping force is not adjusted correctly. the

2) Process problem: the injection speed is too high, and the pressure shock peak is too high. the

3) Mold problems: deformation, debris on the parting surface, wear and tear on inserts and sliders, and insufficient strength of the template. The order of measures to solve the flash: clean the parting surface → increase the clamping force → adjust the process parameters → repair the worn parts of the mold → increase the rigidity of the mold. From easy to difficult, every step of improvement should be tested first, and if it fails, proceed to the second step. the

cast aluminum alloy raw material additives

Adding rare earths to cast aluminum alloys can effectively improve the defects of cast aluminum alloys. the

1. The refining effect of rare earth in aluminum alloy

Adding an appropriate amount of rare earth elements to aluminum alloy can promote the refining effect. Rare earth elements can improve the shape of inclusions and purify grain boundaries. Vacuum suction casting method was used to study the influence of Al RE master alloy on the fluidity of A356 alloy. The experimental results proved that adding an appropriate amount of rare earth elements to the alloy melt can reduce the temperature difference between solid and liquid phase lines, reduce the paste solidification tendency of the alloy, and reduce the surface tension of the alloy melt. In addition, it also has the refining effect of degassing and impurity removal, which will improve the fluidity of the melt and reduce the viscosity, which is conducive to the removal of inclusions and gases. A new aluminum alloy flux containing rare earth compounds has been researched and developed. Through a series of physical and chemical reactions, the flux can not only reduce the hydrogen content of A356 alloy melt from more than 0.30ml/100g(Al) to below 0.10ml/100g(Al) at 720℃, and has a significant degassing effect, but also increases the room temperature tensile strength of A356 alloy by 7.27%, and the elongation rate increases by 85.58%. However, excessive rare earth elements will also aggravate the aggregation of RE-rich phases and become inclusions, thereby reducing the fluidity of the alloy melt. the

2. The refinement effect of rare earth on aluminum alloy
   Purposefully suppress the growth of columnar crystals and double columnar crystals, and promote the formation of fine equiaxed crystals. This process is called grain refinement. Due to the refinement of grains, the performance of the alloy is improved, and at the same time, defects such as shrinkage porosity, thermal cracking, and pinholes are reduced. The most basic method of refinement is to suppress nucleation, and to add foreign nucleation particles of grain refiner to the melt. At present, the method of adding a refiner has become the most effective and practical method. There are three types of grain refiners commonly used in cast aluminum alloys: binary Al-Ti alloys, binary Al-B alloys and ternary Al-Ti-B alloys. The master alloy (grain refiner) is added to the aluminum alloy melt to dissolve, release the intermetallic compound phase, and become the foreign nucleation core. the

Adding rare earths to aluminum alloys can not only refine the grains, but also significantly refine the dendrite structure (reduce the secondary dendrite spacing), and the best effect corresponds to different rare earth contents. However, its refining effect is weaker than that of Ti, B and other elements. The critical value of rare earth addition is closely related to the melting and casting conditions of the alloy. Only under certain production process conditions, a certain amount of rare earth will have the best refining effect. With the use of general refiners, the refinement effect gradually declines with the prolongation of the standing time of the aluminum liquid; with the use of Al-5Ti-1B-10RE master alloy, the rare earth elements can prevent the aggregation and precipitation of refinement elements, and have a certain promotion effect on the refinement of Ti and B, which can effectively inhibit the decline of the grain size of the aluminum-silicon alloy during the long-term standing process, and is suitable for mass production of automotive aluminum alloy castings.

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