Automobile Casting: Everyting You Need to Know

Casting is the most flexible method to manufacture complex parts.

The application of advanced casting technology has brought new vitality to the manufacturing industry.

With the advent of numerous software and the rapid development of computer technology, it is possible to provide accurate and reliable information for the production of castings that meet the requirements in terms of geometry, size and service performance.

Automobile Casting: Everyting You Need to Know 1

About 15% ~ 20% of automotive parts are produced by different casting methods, which are mainly the key parts of power system and important structural parts.

At present, the production technology of automobile castings in the developed countries of automobile industry is advanced, the product quality is good, the production efficiency is high, and the environmental pollution is small.

The casting raw and auxiliary materials have been serialized and standardized, and the whole production process has been mechanized, automated and intelligent.

With the rapid development of automotive technology, rapid molding technology, CAE technology, 3D modeling, CNC technology and other technologies are adopted to provide reliable support for shortening the production preparation period of castings and reducing the risk of new product development.

Automobile Casting Technology

1. Casting process

Casting mainly includes sand casting and special casting.

Ordinary sand mold casting

It uses sand as the mold material, is also called sand casting.

It includes wet sand mold, dry sand mold and chemical hardening sand mold.

However, not all sand can be used for casting.

The advantage is that the cost is low because the sand used in the mold can be reused;

The disadvantage is that the production of the casting mold is time-consuming, and the casting mold itself cannot be reused, and the finished product can be obtained only after it is destroyed.

Special casting

According to the molding materials, special casting can be divided into two types: special casting with natural mineral sand and stone as the main molding materials (such as investment casting, mud mold casting, shell mold casting, negative pressure casting, full mold casting, ceramic mold casting, etc.) and special casting with metal as the main molding materials (such as metal mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.).

Classification of casting process

Fig. 1 Classification of casting process

In the automotive field, the main casting processes used include the following two categories:

1.1 Gravity casting (GDC)

Gravity casting refers to the process in which molten metal is injected into the mold under the action of the earth’s gravity, also known as gravity casting.

The molten metal is poured into the mold, and the molten metal occupies the space in the cavity under the action of gravity.

If the part must be hollow, it is also necessary to set a sand core in the mold cavity.

Sometimes, in order to ensure proper metal flow, the pouring device may be inclined, and this device is called “inclined GDC”.

In a broad sense, gravity casting includes sand mold casting, metal mold casting, investment casting, lost foam casting, mud mold casting, etc.

Among them, sand mold casting is the most widely used in the automotive industry.

1.1.1 Sand casting

At present, the most widely used cast iron automobile parts are still wet sand molding, especially the appearance of static pressure or air impact molding with air flow pre compaction, which shows more advantages – low energy consumption, low noise, less pollution, high efficiency and reliable operation.

Recently, foreign equipment manufacturers have continuously improved the molding machine.

They have successively adopted air impact compaction, air impact plus compaction with air flow gain, static pressure plus compaction, active multi contact compaction, molding extrusion compaction and other improvement methods to make the hardness of the sand mold more uniform.

sand casting process

Fig. 2 sand casting process

With the development of high-power semiconductor components, computers and microelectronics technology, the electric servo system is used to replace the hydraulic and pneumatic drive used in the molding line, which further accelerates the rhythm of the molding line and greatly improves the operation reliability.

At the same time, the hydraulic control system is obviously simplified, and the maintenance workload is correspondingly reduced.

The casting and gate can be pre cleaned at the same time when the molding line adopts the double barrel sand dropping machine.

The pouring of molding line often restricts the starting rate of the whole line, and automatic pouring equipment should be used.

Some manufacturers adopt the air pressure ladle and contact pouring process, which is conducive to saving molten iron, ensuring quality and protecting the sand box.

During the pouring process, more flow inoculation is adopted, and some adopt the combination of in mold inoculation and filtration.

In the casting process, for the use of sand cores, according to the different conditions of each plant, the cold core box is used for core making, the hot core box for core making or the shell core for core making.

Other sand cores, including the crankcase sand core, the cylinder barrel and the top sand core, and the front sand core of the front and rear end faces, are mostly made with the cold core box to ensure the dimensional accuracy and energy saving.

The cold core box is more and more widely used.

The cold core is mainly made by ISO cure triethylamine hardening method (more advanced ISO Max has been developed in the United States).

In order to improve the quality of the inner surface and the cleanliness of the inner cavity of the casting, the sand core should be coated with water-based coating instead of alcohol based coating, which is beneficial to prevent pollution.

Microwave drying after coating has high efficiency and energy saving, and the quality of sand core is better than that of traditional gas and natural gas drying.

The KCY-CORE process is adopted, and the process hole opened on the sand core is used for secondary sand filling and solidification, so that multiple sand cores are integrated into a combined sand core, and then the whole is coated and dried. In this way, the dimensional accuracy of the casting can be greatly improved, and the overall dimensional error is less than 0.3mm.

In the molding sand system, there are old sand magnetic separation equipment, sand block crushing equipment, screening equipment and old sand cooling equipment to ensure the quality of recycled old sand.

At the same time, the new sand, coal powder, bentonite and other added materials shall be accurately and quantitatively fed according to the proportion determined by the process, and the water addition shall be adjusted at any time according to the real-time control data to ensure the molding sand performance.

There are also closed-loop real-time control of molding sand performance of the whole system or online expert system control of molding sand quality.

It should be noted that the molding sand turnover of the molding sand system is large and the inertia is strong.

The adjustment of the molding sand performance should be judged by the trend, and predictable adjustment measures should be taken to ensure the quality stability of the molding sand system.

Common castings include: engine block, cylinder head, gearbox housing, intake manifold, etc.

1.2 Die casting

When the cross-section of the required casting is quite complex, or the wall thickness in some specific places is very thin (as shown in Fig. 3), it is impossible to ensure that the molten metal completely fills the mold cavity under the influence of gravity alone.

In this case, the metal liquid can be pressed into the mold cavity under the pressure to ensure that the metal liquid can completely fill the mold cavity.

The setting can be high-pressure die casting (HPDC) or low-pressure die casting (LPDC).

The castings produced by HPDC process have good dimensional consistency and similar tolerance, about + / – 0.2mm.

This kind of accuracy can not be achieved in GDC or even LPDC.

With the rapid development of automotive technology, high-pressure die casting technology has become one of the hot spots of automotive casting.

Automobile Casting: Everyting You Need to Know 2

Fig. 3 complex thin wall parts

1.2.1 High pressure casting

High pressure casting is a method that liquid or semi liquid metal is rapidly pressed into the mold under high pressure, and then crystallized and solidified under pressure to obtain the casting.

The main process of high-pressure casting can be divided into three stages: mold closing, injection and ejection.

high pressure casting process flow

Fig. 4 high pressure casting process flow

In the process of die casting, the injection parameters have great influence on the porosity of die casting parts, and must be adjusted reasonably.

With the closed injection end time control system, the flash free die casting can be realized.

X-ray flaw detection and ultrasonic testing can be used to detect the quality of die castings.

Vacuum casting and oxygen filled die casting developed on the basis of high pressure casting technology are aimed at eliminating casting defects, improving internal quality and expanding the application scope of die casting.

In the process of squeeze casting, the melt is filled and solidified under pressure, which has the advantages of stability, no metal splashing, less oxidation loss of molten metal, energy saving, safe operation and reduction of casting hole defects.

It has been widely used in the development and application of high-performance aluminum alloy castings such as aluminum alloy subframe.

Vacuum die casting

In order to reduce or avoid the porosity and porosity of the casting caused by the high-speed involvement of the gas with the molten metal in the process of die casting, it is most common to use the vacuum casting of the mold before die casting.

According to the vacuum degree of the pressure chamber and the cavity, vacuum die casting can be divided into ordinary vacuum die casting and high vacuum die casting.

Automobile Casting: Everyting You Need to Know 3

Fig. 5 process flow chart of vacuum die casting

The key of high vacuum die casting is to obtain high vacuum in a very short time.

Fig. 6 is the working principle diagram of the suction type high vacuum die casting machine.

It uses vacuum to suck the metal liquid into the pressure chamber, and then carries out rapid injection to obtain a high degree of die casting vacuum.

Principle of high vacuum die casting: before die casting, the air in the whole pressure chamber and the cavity shall be pumped out from the vacuum tube.

The speed of the vacuum pumping process must be as fast as possible, so that the metal liquid in the crucible and the pressure chamber will have a large pressure difference, so that the metal liquid in the crucible will enter the pressure chamber along the liquid riser, and then the pressure injection punch will start to conduct pressure injection.

suction high vacuum die casting machine

Fig. 6 suction high vacuum die casting machine

Oxygen filled die casting

Oxygen filled die casting is to fill dry oxygen into the pressure chamber and die casting mold cavity to replace the air and other gases therein.

The schematic diagram of oxygen filled die casting process is shown in Fig. 7.

Oxygen filled die casting is only applicable to aluminum alloy.

When the aluminum alloy liquid is pressed into the pressure chamber and die-casting mold cavity, it will react with oxygen to generate Al2O3, and form small particles of Al2O3 with uniform distribution (diameter less than 1um), thus reducing or eliminating the porosity and improving the compactness of the casting.

These small particles are dispersed in the casting, accounting for about 0.1% – 0.2% of the total mass, and do not affect machining.

Schematic diagram of oxygen filled die casting

Fig. 7 Schematic diagram of oxygen filled die casting

2. Casting equipment

The equipment used in the automobile casting industry must be fast paced, efficient and reliable equipment suitable for continuous work.

Due to the high quality requirements of car castings, these casting equipment must be of high precision.

The main casting equipment includes: molding machine, sand mixer, core making machine, molding equipment, dust removal equipment, smelting furnace, die casting machine, machining equipment, shot blasting machine, cleaning machine, testing equipment, etc.

The die casting machine and smelting furnace are introduced.

2.1 Smelting furnace

The smelting furnace uses the medium frequency power supply to establish the medium frequency magnetic field, so that the induction eddy current is generated inside the ferromagnetic material and generates heat, so as to achieve the purpose of heating the material.

The medium frequency electric furnace uses 200-2500Hz medium frequency power supply for induction heating, smelting and heat preservation.

The smelting furnace is mainly used for smelting carbon steel, alloy steel, special steel, and also for smelting and temperature raising of non-ferrous metals such as copper and aluminum.

Related reading: Ferrous vs Non-ferrous Metals

The equipment is small in size, light in weight, high in efficiency, low in power consumption, fast in melting and heating, easy to control the furnace temperature, and high in production efficiency.

The whole set of smelting furnace equipment includes intermediate frequency power cabinet, compensation capacitor, furnace body (two), water-cooling cable and reducer.

The furnace body is composed of four parts: the furnace shell, the induction ring, the furnace lining, and the tilting reduction box.

The furnace shell is made of non-magnetic materials.

The induction coil is a spiral cylinder made of rectangular hollow tubes.

During smelting, cooling water is passed through the tubes.

The copper bar led out of the coil is connected with the water-cooled cable.

The furnace lining is close to the induction ring and is made of quartz sand.

The tilting of the furnace body is directly rotated by the tilting reduction box.

The furnace tipping reducer is a two-stage turbine speed change, with good self-locking performance and stable and reliable rotation.

In case of emergency power failure, the furnace tipping shall be stopped to avoid danger.

The control of the motors of the tilting reduction boxes of the two furnaces can be selected through the furnace selection switch.

The switch box with four core rubber wire can enable the operator to stand at the appropriate position to control the tilting and resetting of the furnace body.

At present, many foundry factories are still in the state of industrial 2.0, and urgently need to be improved in terms of environmental protection, automation, intelligence and safety.

With the arrival of industry 4.0, all parameters in smelting will be recorded through sensors working in extremely high temperature environment.

From the filling level of heating furnace to the pollution degree of molten pool will become the basic data for realizing intelligent networked smelting furnace.

In the future, in a smelting furnace factory, the cleaning work can be completed by a robot.

The robot knows all the parameters of the furnace and can take timely actions before the pollution reaches the critical line.

2.2 Die casting machine

Die casting machine is a machine used for pressure casting. Including hot compression chamber and cold compression chamber.

Later, they are divided into two types: straight type and horizontal type.

Under the pressure of the die casting machine, the molten metal is hydraulically injected into the mold for cooling and forming.

After the mold is opened, the solid metal casting can be obtained.

Die casting machine is mainly composed of clamping mechanism, injection mechanism, hydraulic system and electric control system.

In addition, the die casting machine also has parts and bases, other devices, auxiliary devices and other parts.

basic structure of die casting machine

Fig. 8 basic structure of die casting machine

In the past 30 years, the die casting machine has developed rapidly in the aspects of large-scale, automation, unitization and flexibility.

In recent years, high and new technologies such as integration and lightweight of automobile die casting have constantly put forward higher and newer requirements for die casting machines.

Among them, the body integrated forming technology, as the current hot topic, has pushed the heavy ton die casting machine to the forefront.

Recently, Tesla purchased another 8000 ton die casting machine from Italy DRA, which is 30% heavier than the 6000 ton die casting machine used on model y.

I believe this record will be constantly refreshed.

Here, let’s analyze why heavy-duty die casting machine is the future development direction and what advantages it has.

Advantage 1: single station material forming cost advantage

Fig. 9 is a structural diagram of Tesla Model y frame.

The yellow part is an integrated large part of the rear part of the body and the wheel arch on the top of the rear axle tower.

With the help of large-scale die-casting machine, this complex part that needs multiple stations and processes can be completed in one go.

Therefore, it has an absolute advantage in cost.

Automobile Casting: Everyting You Need to Know 4

Fig. 9 structural diagram of model Y frame

Advantage 2: integrate stamping and welding, and optimize the overall rhythm

Tesla’s goal is to be the Toyota Volkswagen in the new energy industry, so the production rhythm becomes extremely important.

In order to improve the tempo of the 8000 ton die casting machine, during the pressure sealing process of casting parts, some technologies can form a cavity between the casting half films on both sides, and inject molten metal with temperature protection into the cavity.

Since the cavity is in a negative pressure state, it can effectively eliminate the air bubbles generated by the casting turbulence, which is very helpful for the consistency of materials and the casting speed during die casting.

According to the data released by Tesla, each casting will inject about 80 kg of aluminum alloy liquid into the cold chamber mold at the speed of 10 meters per second.

The beat is about 85 seconds, and the number of pieces per hour is 42, which is an optimization of the current beat.

The advantages are also accompanied by some disadvantages.

For example, there are still challenges in the perspective of exercise mechanics under this process, and mold design is also a great challenge.

On the road of developing large-scale die-casting machines, these are the technical problems we will tackle in the future.

3. Casting materials

3.1 Cylinder block

The traditional automotive engine block material is cast iron, which still occupies a dominant position today.

However, with the gradual improvement of engine performance and the demand for lightweight, the engine block material is also undergoing rapid innovation.

There are three main directions:

  • Improve the grade of cast iron to improve the strength and performance of the cylinder;
  • The use of vermicular graphite cast iron to produce engine cylinder block has the advantages of high strength and good fatigue performance, and is conducive to thin-walled design. It can withstand greater burst pressure, reduce cylinder deformation, and increase power by 10% ~ 20%;
  • Aluminum alloy cylinder block, with the fastest development momentum, represents the key development direction of passenger car cylinder block.

Generally, it needs to be inlaid to reduce the quality and reduce the energy consumption of the vehicle.

However, limited by the strength and thermal fatigue performance of aluminum alloy, it can not meet the requirements on the high-power engine block, and the cost is relatively high.

3.2 Cylinder head

Engine cylinder head is the main application field of aluminum alloy, especially in the passenger car cylinder head market, which is basically monopolized by aluminum alloy materials.

In the truck market, cast iron is rarely used for the cylinder head of high-power engine, and vermicular iron cylinder head is replaced, which can solve the problem of cracking of gray cast iron cylinder head.

3.3 Crankshaft

The important performance upgrading process of automobile engine for energy saving and emission reduction is the application of engine supercharging technology.

Whether it is gasoline engine or diesel engine, especially in the truck market, the use performance of Pearlite Nodular Iron Crankshaft used in the past can not meet the requirements due to the increase of engine explosion pressure, and it is made of forged steel materials such as 40Cr.

However, with the development of technologies such as fillet rolling and induction hardening of Pearlite Nodular Iron Crankshaft, nodular iron crankshaft occupies a large market share in the passenger car and medium and low horsepower engine truck market.

In addition, the engine crankshaft made of isothermally quenched ductile iron has also been studied at home and abroad.

3.4 Others

Other automotive castings, such as the support parts and structural parts of various engines and chassis, such as various brackets, discs, shells, steering parts, etc., are made of cast iron materials according to the requirements of service performance.

With the development of automotive environmental protection requirements, the application proportion of gray cast iron and cast steel is gradually decreasing, while the high-performance ductile iron, Mg alloy, Al alloy and special cast iron materials are further increasing.

3.5 Development trend

At present, the castings represented by cast iron are the main part of automotive castings.

In particular, the application of ductile iron has replaced many steel castings and gray iron castings, and the application of malleable iron in automotive parts has almost disappeared.

Its excellent strength and toughness performance and easy to control production mode have gradually increased its application proportion.

The R & D and production of high-strength and high-toughness ductile iron will become an important basis for the continuous application of ductile iron.

Another excellent engineering material, isothermally quenched ductile iron, has excellent mechanical properties.

It has made rapid development and good application abroad.

It has made gratifying achievements in the application research of crankshaft, gear, bracket and structural parts, and has been applied in practice.

Since the invention of vermicular graphite cast iron in 1948, its stable production range is narrow, and its performance has not attracted people’s attention, so its application has been less.

Until the advanced production control technology is successfully researched and put into use, it is possible for vermicular graphite cast iron to be used in the production of complex castings.

Vermicular graphite cast iron has higher tensile strength (75%), elastic modulus (40%) and fatigue strength (100%) than cast iron and Al, making it an ideal material for the design of engine cylinder block and head.

The requirement of automobile lightweight is to use mg and Al alloy to manufacture automobile castings.

For every 10% reduction in vehicle weight, the fuel consumption will be reduced by 5.5%, and the emission will be reduced by about 10%. However, the density of Al alloy is only 1 / 3 of that of Fe, and its strength is equivalent to that of gray cast iron.

It is an ideal material to replace gray cast iron for manufacturing engine cylinder block and cylinder head.

Al alloy castings have achieved rapid growth in the world in recent years, and Mg alloys with lighter density have been rapidly applied in automobile steering wheel, seat frame, instrument panel, cover and other parts with the deepening of research and application.

The requirement of automobile lightweight is to use Mg and Al alloy to manufacture automobile castings.

For every 10% reduction in vehicle weight, the fuel consumption will be reduced by 5.5%, and the emission will be reduced by about 10%.

However, the density of Al alloy is only 1 / 3 of that of Fe, and its strength is equivalent to that of gray cast iron.

It is an ideal material to replace gray cast iron for manufacturing engine cylinder block and cylinder head.

Al alloy castings have achieved rapid growth in the world in recent years, and Mg alloys with lighter density have been rapidly applied in automobile steering wheel, seat frame, instrument panel, cover and other parts with the deepening of research and application.

Development direction of Automobile Casting

1. Development direction of castings

Integrated design of automotive castings

With the increasing requirements of energy saving and environmental protection of automobiles and reducing production costs, the advantages of casting forming are fully utilized to realize the casting forming of integrated parts through reasonable design and structural optimization of several parts formed by stamping, welding, forging and casting, which can effectively reduce the weight of parts and reduce unnecessary processing processes, thus realizing the lightweight and high-performance of parts.

The development trend of Automobile Casting integration is more obvious in non-ferrous alloy casting.

In order to make full use of the casting process to realize the production of complex structural castings, integrated design high-pressure castings such as door inner panel, seat frame, instrument panel frame, front-end frame and firewall have emerged.

Their size is significantly larger than that of the currently produced castings, and it requires a 4000-5000t or even larger tonnage die casting machine for production.

Automobile Casting: Everyting You Need to Know 5

Fig. 10 Tesla Model Y integrated casting body

Lightweight of automotive castings

On the premise of ensuring the strength and safety performance of the vehicle, the curb weight of the vehicle shall be reduced as much as possible to achieve lightweight, so as to improve the power performance of the vehicle, reduce fuel consumption and reduce exhaust pollution.

The fuel consumption per 100 km can be reduced by 0.3 ~ 0.6L for every 100 kg reduction in the vehicle curb weight.

If the vehicle weight is reduced by 10%, the fuel efficiency can be increased by 6% ~ 8%.

With the need of environmental protection and energy saving, the lightweight of automobile has become the trend of the world automobile development, and the lightweight of automobile castings has also become one of the important development directions of automobile castings.

The realization of lightweight will mainly develop from the following three points:

1) Lightweight design

The main drawback of equal thickness design is that it can not give full play to the structural performance and lead to the increase of casting weight.

CAE analysis, topology optimization and other means are used to optimize the design of parts and components, so that the stress value of each part is close, that is, the wall thickness of each part is inconsistent, and the material thickness of the part with small stress is reduced, so as to reduce the weight of the part.

Considering that casting forming can realize the forming of complex structure castings and various irregular cross-sections.

During the design, CAE or topology optimization are used to analyze the stress of components.

According to the force distribution, the shape of the parts and the specific local material thickness are determined.

The weight of parts can be greatly reduced by reinforcing the casting, digging holes and changing the section.

2) Application of light alloy materials

The use of light alloy materials such as aluminum and magnesium is the main weight reduction measure of automobile manufacturers in various countries.

The density of aluminum is only 1 / 3 of that of steel, and it has excellent corrosion resistance and ductility.

The density of magnesium is smaller, only 2 / 3 of that of aluminum, and its fluidity is excellent under high-pressure casting conditions.

The specific strength of aluminum and magnesium (the ratio of strength to mass) is quite high, which plays an important role in reducing self weight and improving fuel efficiency.tion.

However, it should be noted that the raw material price of light alloys such as aluminum and magnesium is much higher than that of steel materials, which limits its wider application in the automotive industry.

However, despite the high price of raw materials, the single vehicle consumption of magnesium and aluminum castings has increased year after year.

On the one hand, the increase in cost is compensated by technological progress; on the other hand, market competition forces automobile manufacturers to reduce profits and adopt more light alloys.

However, the development of advanced forming technology is one of the keys to greatly increase the amount of light alloy and reduce the purchase price of magnesium aluminum ingots.

3) High performance of casting materials

It is one of the effective methods to reduce the weight of castings to improve the performance of materials and make the parts per unit weight bear higher loads.

Bracket structural casting accounts for a large proportion of automotive casting, so the development of its casting has become one of the focuses.

Through heat treatment and other measures, the microstructure of the material can be changed, so as to improve the strength, rigidity or toughness of the parts and effectively reduce the weight of the parts.

Isothermally quenched ductile iron not only has higher strength than ordinary cast steel, but also has lower density than steel.

Its density is 7.1g/cm3, while that of cast steel is 7.8g/cm3.

It is widely recommended in recent years.

Isothermally quenched ductile iron is adopted, which is 10% lighter than steel castings under the same casting size.

Table 1 lightweight effect of isothermally quenched ductile iron material replacement

spare partsIsothermally quenched ductile iron weight (kg)Cast steel weight / kgWeight reduction ratio /%
Front suspension upper cross10.252559.00
Lower cross arm of front suspension32.466449.28
Front suspension upper spring bracket21.2834.638.50
Rear suspension lower spring bracket20.7433.1637.45
Rear suspension lower cross member9.3250.1684.58

In terms of aluminum alloy and magnesium alloy castings, high-strength and high-toughness materials are also used for replacement.

On the basis of weight reduction of the original light alloy, high-performance materials are used for further weight reduction.

General Motors of the United States uses high-performance AE44 alloy to replace the original aluminum alloy, and uses high-pressure casting to produce the frame.

On the basis of weight reduction of the aluminum alloy, the weight is further reduced by 6kg.

Digital development of automotive castings

The comprehensive combination of Automobile Casting Development and digital technology can significantly improve the level of casting technology and shorten the cycle of product design and trial production.

At present, digital manufacturing technology has been widely used in the development of automotive castings.

In the stage of casting structure design and casting process design, 3D design software such as Pro / E, CATIA and UG has been widely used, and some advanced casting enterprises have realized paperless design.

Software such as magma, ProCAST and Huazhu CAE have been widely used to simulate the solidification process, microstructure, component segregation and material properties of automotive castings.

It can also simulate the velocity field, concentration field, temperature field, phase field and stress field in the casting process, which can ensure that the process scheme is optimized before mass production.

In order to meet the needs of rapid development of automotive castings, RP (Rapid Prototyping Technology) has been widely used in rapid trial production of automotive castings based on the design and development of CAD / CAE.

After obtaining the original CAD / CAE data, the casting prototype or the mold prototype required by the casting is obtained by the method of layer by layer stacking through bonding, fusion or sintering.

The former can be used for trial production of casting samples by investment casting, gypsum casting and other methods.

The latter can be directly used as a mold to manufacture sand cores, and the castings can be poured out through core assembly molding.

In addition, powder laser sintering method (SLS) can be used to directly complete the production of sand core and sand mold, so as to obtain the sand mold required for the trial production of castings.

For the outer mold with relatively simple structure, the CNC machine tool can also be used for cam processing with Machinable plastic to obtain the core box and pattern required for the trial production of the casting, or the sand block can be directly processed to directly obtain the sand mold of the outer mold.

Generally speaking, the digital technology has run through the design, development and trial production of castings, effectively improving the development speed and efficiency of castings.

At present, the main problem is that the digital technologies of design, analysis and rapid manufacturing are independent. When the development process is transformed from one stage to another, it still needs to carry out quite tedious data conversion work.

It is hoped that in the future, a unified data interface platform can be developed for the digital technology applied in each link of casting development, a standardized data conversion standard can be established, and seamless data conversion between different software can be realized, so as to further improve the speed of casting development.

2. Development direction of Automobile Casting Technology

Production technology of thin wall complex structure casting

With the development of automobile industry and the demand of energy saving and emission reduction, automobile parts are becoming lighter and lighter.

It is an important development direction of engine block to achieve lightweight through thin-walled design.

According to the 3mm thin-wall characteristics of the cylinder block, the core assembly and vertical casting process put forward strict requirements for both core making and core assembly.

The core making center can realize the high intelligence and automation of core making production.

From the addition of raw sand and resin, the whole process of sand mixing, core making, core repair, assembly, coating and drying to molding and core assembly and lowering can be highly automated, so that the core making quality, assembly quality, i.e. dimensional accuracy and coating drying quality of the sand core can be stably guaranteed, thus avoiding the quality and dimensional risks caused by human factors and meeting the needs of large-scale cylinder core production.

It can effectively solve the problem of unstable and high waste rate during mass production.

Meanwhile, due to the improvement of the dimensional accuracy of the sand core, the cleaning workload and cost are greatly reduced, and the requirement of 3mm wall thickness can be effectively guaranteed.

Manufacturing technology of large aluminum magnesium alloy structural parts

With the increasing requirements of energy saving, environmental protection and reducing the cost of components, the large-scale structural casting of aluminum magnesium alloy has become an important development trend, and its manufacturing technology has also become the current development hotspot.

At present, the main production technologies of aluminum magnesium alloy large-scale structural parts include high-pressure casting, squeeze casting and low-pressure casting.

Due to the high production efficiency and good product quality of high-pressure casting, it has become the main production process at present.

The development of its manufacturing technology mainly focuses on the improvement of air entrainment in the process of high-pressure casting, the formation of air holes in the casting and the heat treatment problems.

The high vacuum die casting described above can effectively solve the air entrainment problem and prevent the generation of air holes.

Vacuum die casting technology has been successfully applied to the mass production of automotive structural castings, providing advanced forming methods and processes for the application of high-quality light alloy castings.

Precision casting technology for Castings

With the development of automobile casting forming technology, casting precision forming is a kind of casting forming method.

The castings produced by this kind of forming method can be directly used without cutting or less cutting.

With the improvement of the dimensional accuracy of castings, the casting precision forming technology has been rapidly developed in recent years.

A series of casting forming methods such as precision sand casting, lost foam casting, controllable pressure casting and pressure casting have emerged.

Vacuum casting, oxygen filled die casting, semi-solid metal rheological or thixotropic die casting and other process methods developed on the basis of high-pressure casting technology are aimed at eliminating casting defects, improving internal quality and expanding the application scope of die casting.

In the process of squeeze casting, the melt is filled and solidified under pressure, which has the advantages of stability, no metal splashing, less oxidation loss of molten metal, energy saving, safe operation and reduction of casting hole defects.

It has been widely used in the development and application of high-performance aluminum alloy castings such as aluminum alloy subframe.

The continuous growth of automobile production urgently requires the casting production to develop in the direction of high quality, excellent performance, near net shape, multiple varieties, low consumption and low cost.

About 15% ~ 20% of the parts of a complete vehicle are castings.

This requires the foundry industry to continuously apply various new technologies and materials to improve the overall level of casting.

Casting precision casting technology can meet the above requirements of automotive castings, and its application will also cover different casting production processes of automotive castings.

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