汽车行业挤压铸造SQUEEZE CAST AUTOMOTIVE

2024年1月4日发(作者：桃树作文)

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SQUEEZE CAST AUTOMOTIVE

APPLICATIONS AND DESIGN

CONSIDERATIONSZ. Brown, C. Barnes, J. Bigelow , P. DoddWith an increasing emphasis on vehicle weight reduction, the demand for lighter weight automotive compo-nents continues to increa. Squeeze casting is an established shape-casting process that is capable of produ-cing lightweight, high integrity automotive components that can be ud for structural applications.

In recent years the squeeze casting process has been ud with various aluminum alloys to produce

near-net shape components requiring high strength, ductility, pressure tightness or high wear resistance

[1]. Squeeze casting has proven to be an economical casting process for high volume applications and

offers design and materials engineers an alternative to conventional casting process such as gravity

permanent mold (GPM), low pressure die casting (LPDC), sand cast aluminum/ iron, and conventional

high pressure die casting (HPDC).

This paper describes Contech’s squeeze casting technology (P2000TM) and provides examples of high

volume automotive components manufactured at Contech. This paper also includes product design

considerations, an overview of process simulation techniques, a comparison of mechanical properties, and ca

studies for lect automotive DS: squeeze casting, aluminum, automotive applications, die casting, safety critical

INTRODUCTION

Conventional HPDC is a well-established process for the

manufacturing of a wide variety of aluminum automotive

components such as engine blocks, pump housings, oil

pans, and transmission components. Conventional HPDC

has many advantages including near-net shape capability,

low manufacturing cost, and excellent dimensional ac-curacy and repeatability.

Achievable casting performance is limited however, due to de-fects that emerge during the casting process such as gas and

shrink porosity, laminations, and inclusions. In addition,

HPDC components are not considered heat treatable, which

further limits achievable performance.

For applications that require higher component integrity

(high strength and ductility, reduced porosity, uniform

microstructure, and ability to heat treat), alternative cast-Zach Brown, Chuck Barnes, Joe Bigelow

Contech U.S. LLC

Paul Dodd

Contech UK LLC

Paper prented at the International Conference “High Tech

DieCasting”, Montichiari, 9-10 April 2008, organid by AIMing process such as squeeze casting should be considered.

Squeeze casting is an established process that builds upon con-ventional HPDC practices and is ud to manufacture vari-ous automotive components that require high strength and

ductility, as well as applications that require high pres-sure tightness or wear resistance. Examples include steer-ing column components, steering knuckles, control arms,

suspension links, pump housings, and various powertain

components [1]. The squeeze casting process is capable

of producing components with dimensional accuracy and

near-net shape capability that is equal to conventional HPDC.

Unlike HPDC however, the squeeze casting process is capable

of producing higher integrity components. As a result,

design engineers are able to further optimize current alumi-num designs or substitute aluminum in place of heavy materi-als such as steel and cast iron.

SQUEEZE CASTING TECHNOLOGY (P2000TM)

Squeeze casting can be divided into two categories; “direct”

and “indirect”. Direct squeeze casting, often termed “liquid-metal forging”, consists of pouring metal into a lower die con-tained within a hydraulic press. The upper die clos over the

lower die and high pressure is applied throughout the entire

solidification process. In contrast, indirect squeeze casting con-sists of pouring molten metal into the cold chamber of a die

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sFig. 1 Schematic of P2000 casting della macchina di colata . 2 Design process for aluminum shock urazione del processo per la produzione di un

supporto anti-urto in g machine, ejecting the metal into the cavity at relatively

slow shot speeds, and applying pressure through the shot sys-tem during solidification [2].

Contech’s proprietary P2000TM process is considered an indi-rect squeeze casting process. Fig. 1 shows the schematic of a

typical casting machine. The vertical cold chamber is designed

to tilt back prior to pouring the metal into the cold chamber.

The metal is poured down the sidewall of the cold chamber to

minimize turbulence, thereby minimizing porosity and the

formation of oxide skins.

This is done outside of the casting cycle during the spray-ing pha so overall cycle time is minimized. The metal is

slowly forced into the preheated die cavity, and pressure is

applied throughout solidification. The slow injection speed

reduces turbulence resulting in minimal air entrapment. The

continuous application of pressure helps minimize shrink

porosity and creates rapid heat transfer at the mold/metal in-terface resulting in a fine microstructure (small dendrite arm

spacing (DAS) and fibrous silicon morphology). The reduced

amount of shrink and gas porosity, fine microstructure, and

ability to heat treat are factors responsible for the improved

part integrity [3].

The proprietary CONTECH P2000TM squeeze casting process

has been in high-volume production for over 25 years and

has been continuously refined throughout this timeframe.

TMAs a result, the P2000 casting process takes into account all

factors that can influence the quality of the casting including

die cooling systems, gating and venting configurations,

casting process parameters, die lube lection and applica-tion, alloy lection, metal handling, heat treatment, and

condary operations. If all of the factors are considered dur-ing the design and product development pha, components

can be optimized to not only meet functional requirements

but also manufacturing requirements.

DESIGN CONSIDERATIONS

With ongoing emphasis on weight reduction, designers are

challenged with developing components that meet weight

and cost targets, while meeting functional and manufactur-ing requirements.

Examples of functional requirements include strength,

durability, stiffness, hardness/wear resistance, surface ap-pearance, and packaging. Manufacturing requirements in-clude castability, dimensional capability, cycle time optimi-zation, tooling reliability, machining stock minimization, and

overall casting quality. Determining the proper balance be-tween the factors can be challenging. It is recommend

therefore that design engineers collaborate cloly with cast-ing engineers as early as possible during the development of a

new product.

Design Process

Creating a fully optimized casting design requires multiple

design iterations and analysis techniques. Fig. 2 shows an

example of the design process that was ud to convert a

steel stamped shock mount asmbly to a single aluminum

squeeze casting. Solid modeling software was ud to de-velop the initial casting models. Finite element analysis (FEA)

was ud to optimize the component geometry and ensure

all strength, durability, and stiffness requirements were met.

Process simulation tools were ud to ensure manufacturing re-quirements were met and to indentify potential casting flaws

(i.e. porosity, flow related defects, etc.). The final design

was validated through component testing of the prototype

castings. The aluminum shock mount weighed approximate-ly 30% less than the steel design. The number of individual

stamped and welded components was reduced from ven to

one.

By using both FEA and process simulation tools simul-taneously, design engineers can take advantage of the full

material potential, resulting in lighter weight designs. Simula-tion results can be compared to FEA results to determine if po-tential casting defects are near high stress regions, potentially

resulting in lower than expected casting performance. In

addition, specific geometries that improve manufacturability

and component integrity can be incorporated into the design

in the early stages of development. By using this type of

approach, design engineers can take full advantage of the

castings true potential.

Process Simulation

Process simulation tools, when ud properly, are an effec-tive method of evaluating potential casting integrity, estab-lishing process ttings, predicting residual stress, and deter-mining optimal gating and die cooling configuration.

2

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sFig. 3 Example of an aluminum bearing cap that was

converted from GPM to the P2000TM squeeze cast

process. All condary machining operations were

o di una calotta in alluminio prodotto mediante

squeeze casting (P2000TM) anzichè in gravità in

conchiglia. Tutte le operazioni condarie di lavorazione

sono state . 4 Example of P2000TM squeeze cast o di snodo prodotto con la tecnica di squeeze

zing condary machining operations. Fig. 3 shows an

example of an aluminum bearing cap that was converted from

gravity permanent mold to squeeze casting. Due to the near net

shape capability of the squeeze casting process, all condary

machine operations were eliminated. The u of precision

cores with minimal draft (less than .5º per side) eliminated

the need for a condary drilling operation. The flatness

Solidification simulations are ud mainly to predict shrink and surface finish requirements were achieved in the as-porosity and evaluate directional solidification. Fill simula-cast condition, eliminating the milling operation.

tions are ud to identify potential fill related issues such For applications that require high mechanical stiffness, de-as laminations due to merging flow fronts, turbulence, and sign engineers must consider both the modulus of elasticity

improper venting. and ction modulus. Modulus of elasticity is a function of the

Tooling design engineers rely on the tools when optimizing stiffness of the alloy itlf and is fairly similar for most alumi-gating size and location, cooling line placement, cooling media num casting alloys. Section modulus is a function of stiffness

and temperature, die configuration, and process development. from the casting geometry. Increasing the ction modulus

New process simulation techniques are now being ud through design can offt issues with a lower modulus of

to predict the microstructure at various locations through-elasticity. Complex geometries such as ribs, pockets, and

out the casting. Since strength and ductility are influenced by u-shaped ctions can be ud to increa ction modulus. It

the microstructure, this tool can be ud to predict mechani-is recommended to avoid drastic wall thickness changes and

cal properties at various locations throughout the casting. This isolated thick ctions. By avoiding localized thick ctions and

information can then be ud when interpreting FEA results. drastic wall thickness changes, the tendency to form shrink

Other new developments allow for the prediction of residual porosity is greatly reduced. Isolated thick ctions can also in-stress induced during the casting and heat treating proc-duce stress concentration points and cau casting defects such

ess. Most commercially available FEA software does not as hot tears and heat sinks.

consider residual stress. High residual stress can result in

lower than expected component performance and dimensional

Material Selection

capability. One important advantage of the squeeze casting process is that

it is can be ud with various alloy/ heat treat combinations

Design Recommendations

that can be tailored to meet design requirements. Primary al-The squeeze casting process is capable of producing com-loys, such as A356 (AlSi7Mg) are ud in the T6 condition for

plex geometries with high dimensional accuracy and repeat-applications that require high strength and ductility such as

ability. This allows designers to create near-net shapes, thus control arms, steering knuckles, and suspension links. Second-ary alloys such as

Alloy-Temper Yield (MPa)

Tensile (MPa)

Hardness (HBN)

ADC12 (AlSi11Cu3Fe) are ud in the

% Elongation

as-cast, T5, and T6 conditions for ap-A356- T6 220-260 9-15 85-100290-340

plications that require high strength,

ADC12-F 140-170 2-3.5 95-105200-270

pressure tightness, and wear resist-ance. Typical mechanical properties

ADC12- T5 230-260 1-3 110-130280-320

are shown in Tab. 1.

ADC12- T6 290-320 2-5 120-140344-380

sTab. 1 indici di prestazione dei materiali als indexes for candidate materials.P2000TM APPLICATIONS

Fig. 4 shows an example of a squeeze

cast front steering knuckle. In this

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sFig. 5 P2000TM rack & pinion housing for a full size

truck iamento pignone per camion prodotto con la

tecnologia ation, a direct conversion was made from cast iron to

a much lighter-weight, near net-shape aluminium squeeze

casting. Since steering knuckles are considered safety critical

components, rigorous testing is required prior to shipment. Ex-amples of tests include material property measurements, com-ponent strength and fatigue testing, dimensional checks, x-ray,

and ultrasonic inspection. The P2000TM squeeze casting process

was able to meet, and in some cas, exceeded all customer re-quirements and expectations with A356.2 alloy and a T6 tem-per [3]. This high-volume knuckle (120,000 parts annually) has

been in production for veral years.

Fig. 5 shows an example of a squeeze cast rack and pinion

housing for a high-volume full size truck. The integrity of the

cast housing is critical to the overall function of the hydraulic

steering system. Leakage of hydraulic fluid from any pres-surized area of the casting can create a drop in hydraulic pres-sure, thereby creating a potential malfunction of the vehicle

steering system. Through the years rack and pinion housings

have primarily been made via the conventional HPDC process.

For this particular application, the customer required higher

mechanical properties and burst requirements than the HPDC

process could deliver. The P2000TM squeeze casing process was

ideally suited for this type of component due to the superior

physical and mechanical properties, dimensional capabilities,

and prior success with similar applications. The annual re-quirement of 400,000 castings is achieved using a two-cavity

die, ADC12 alloy, and a T6 temper.

CONCLUSION

Squeeze casting is an established shape-casting process that

is capable of producing lightweight, high integrity, automo-tive components that can be ud for structural applica-tions. The squeeze casting process has many advantages

over other casting process including high mechanical

properties, near-net shape capability, minimal gas and shrink

porosity, and the ability to heat treat.

Even with the many advantages of the squeeze casting

process, desired quality level cannot be guaranteed without

proper design and upfront engineering. Carefully planned

casting geometries and tooling designs can offt issues

with manufacturability and casting performance. Advanced

computer aided engineering software such as solid modeling,

process simulation, and finite element analysis are powerful

tools that can be ud to assist with product development,

tooling design, and process engineering. The u of the

tools, combined with the design and casting engineers

knowledge and experience, can result in lighter weight

casting designs that meet or exceed all performance and

cost targets. The u of lightweight castings will assist the

automobile manufacturers in improving fuel economy and re-ducing vehicle emissions.

REFERENCES

1) S. CORBIT. and R. DASGUPTA, Squeeze cast automotive ap-plications and squeeze cast aluminum alloy properties (1999-01-0343). SAE International Congress and Exposition (1999).

2) D. APELIAN and M. MAKHLOUF (eds.), High integrity

aluminum die casting: alloys, process, & melt preparation.

North American Die Cast Association (NADCA), Romount,

Illinois (2004).

3) R. DASGUPTA, C. BARNES, P. RADCLIFFE, and P. DODD,

Squeeze casting of aluminum alloy safety critical components

for automotive applications. World Foundry Congress (2006).

ABSTRACTAPPLICAZIONI DI “SQUEEZE CASTING” NEL

SETTORE AUTOMOBILISTICO E CONSIDERAZIONI

PER LA PROGETTAZIONE

Parole chiave: alluminio e leghe, pressocolata, processi

Per la crescente enfasi sulla riduzione del peso nei veicoli, continua ad

aumentare la domanda di componenti automobilistici più leggeri. Lo

“squeeze casting” è un processo che permette di produrre componenti

leggeri e ad alta integrità che possono esre impiegati per applicazioni

strutturali sugli autoveicoli. Negli ultimi anni il processo di “squeeze ca-sting” è stato utilizzato con varie leghe di alluminio per la produzione di

componenti “near-net-shape” che richiedono alta resistenza meccanica,

duttilità, tenuta a pressione o alta resistenza all’usura [1]. Il processo di

“squeeze casting” si è dimostrato un processo economico per applicazioni

ad alti volumi di produzione ed offre ai progettisti una alternativa rispetto

ai processi convenzionali, come la colata a gravità in conchiglia (GPM), la

colata in bassa pressione (LPDC), la colata in sabbia di alluminio / ghisa,

e la pressocolata convenzionale (HPDC).

Il prente documento descrive la tecnologia di squeeze casting (P2000TM)

sviluppata dalla Contech; fornisce anche empi di alti volumi di produ-zione per componenti di autoveicoli fabbricati presso tale azienda. Il do-cumento prenta anche delle considerazioni relative alla progettazione

dei prodotti, una panoramica delle tecniche di simulazione del processo, il

confronto delle proprietà meccaniche, alcuni studi di casi per componenti

automobilistici specifici.4

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