WO2000053914A1

WO2000053914A1 - Method for manufacturing internal combustion engine pistons

Info

Publication number: WO2000053914A1
Application number: PCT/US2000/006238
Authority: WO
Inventors: Oscar Akramovich Kaibyshev; Vadim Gennadievich Trifonov
Original assignee: General Electric Company; Institute Of Metals Superplasticity Problems Of The Russian Academy Of Sciences
Priority date: 1999-03-12
Filing date: 2000-03-10
Publication date: 2000-09-14
Also published as: JP2002539357A; KR20010109311A; CA2365335A1; RU2176943C2; IL145203A0; EP1163438A1

Abstract

A piston production method produces an internal combustion engine piston. The method comprises forging a billet from an initial billet comprising an aluminum alloy that comprises silicon, intermetallic particles, and injected hardening particles, the forging is conducted under at least one of super-plasticity and hot deformation conditions; and heat treating the forged billet. The forging comprises forging at a temperature in a range from about 0.8 Tmelt to about 0.98 Tmelt. The forging also comprises forging at a STRAIN rate in a range from about 5x10-2 s-1 to about 5x10-5 s-1. The piston being formed with a configuration that enables other parts to be connected to the piston. The initial billet comprises at least one of: coarse grain silicon, intermetallic particles, and injected hardening particles having at least one of a lamellar, comprehensive shape, and fine grain silicon, intermetallic particles, and injected hardening particles being globular in shape. The silicon, intermetallic and injected hardening particle volume content is in a range from about 25 % to about 60 %, and an average grain size of the silicon, intermetallic, and injected hardening particles is less than about 15 νm2.

Description

METHOD FOR MANUFACTURING INTERNAL COMBUSTION ENGINE PISTONS

BACKGROUND OF THE INVENTION

This invention is relates to the manufacture of internal combustion engine pistons, such as, but not limited to, internal combustion engine pistons used in automobiles engines, treaded or crawler-type machinery, aeronautical engines, and marine based motors.

A piston is typically a highly-stressed engine component. While a piston is in motion, the top or crown of the piston may be subjected to high temperatures. Any grooves formed in the piston, for example grooves for compression rings, may be subjected to high impact stresses. Additionally, if the piston comprises a wrist pin port, the port may be subjected to adverse cyclical loads. These piston features undergo varying operational stresses, loads, temperatures, and other operation characteristics (hereinafter "operational characteristics") and may lead to different piston areas needing different mechanical attributes and qualities (also known as "piston characteristics") to endure these operational characteristics.

A piston's mechanical attributes may be determined by its properties. Pistons, such as, but not limited to, engine internal combustion pistons, often comprise aluminum alloys. These aluminum alloys include, but are not limited to, silumins, which can possess a silicon content in a range from about 1 1 % to about 35%. Additionally, if the piston comprises silumin alloy-based compounds, the piston may also comprise hardening agents, such as silicon carbides (SiC) and aluminum oxides (A1₂0₃). The silicon and intermetallic particles in the alloys, in combination with the above agents, may enhance a material's heat resistance and wear properties. However, a material's resistance to metal fatigue and plasticity may decrease with the enhancement of its heat resistance and wear properties.

If a piston's base materials do not provide it with desired properties, piston areas that may undergo stress can be formed from a material that can be hardened The hardening may be conducted by incorporating at least one ot terrous- based alloy and ceramic mateπals For example, a piston portion may include an iron- holder, which is generally recognized as heat resistant that can reduce a compression πng groove wear This piston portion can be reinforced by plasma-arc welding and injecting alloying constituents, such as nickel, iron, and other such reinforcing constituents, into the piston The heat resistant nature of these mateπals protects the piston

Piston design and production may depend on the desired application of the piston. For example, pistons can be formed by casting, as set forth Yu, et al.,

"Aluminum Alloys in Tractor Building", Machine Building, 1971 This casting method provides a relatively efficient and low cost production method, which permits casting of pistons with reinforcements thereon These reinforcements include, but not limited to, piston πng holders and brackets However, these aluminum-cast pistons are generally used in low dynamic loads (pressures) applications because the aluminum-cast pistons can only be subjected to low mechanical stress levels

Another known piston production process compnses hot-deformation forging from an aluminum alloy billet, as disclosed in Yu et al., "Isothermal Forging of Pistons from an Alloy", Forging Production, 1979 This forging method may be more expensive than a casting method, however, forging silumin-alloy pistons can provide enhanced mechanical properties. Thus, these silumin-alloy pistons can be used in applications that undergo powerful loads The forging method typically is conducted for small and relatively simple pistons because of silumin's low plasticity under hot-deformation forging conditions Therefore, reinforcements are added to overcome this plasticity deficiency, for example brackets can be added by being mounted on a piston This reinforcement can complicate a piston's design and increase its production costs. Further, the forging method may be limited by forging temperatures that do not provide a desired quantity and size of the silicon and other hardening particles in the silumm-alloy Therefore, known forging processes may prevent an silumm-alloy piston from achieving desired plasticity and mechanical properties Therefore, a need exists for a piston production method that can produce pistons with desired plasticity and mechanical properties Further, a need exists for a piston production method that overcomes the above-noted deficiencies Also, a need exists for a piston production method for producing silumin-alloy pistons

SUMMARY OF THE INVENTION

A piston production method produces an internal combustion engine piston The method compπses forging a billet from an initial billet compπsing an aluminum alloy that compπses silicon, intermetallic particles, and injected hardening particles, the forging is conducted under at least one of super-plasticity and hot deformation conditions; and heat treating the forged billet The forging compπses forging at a temperature in a range from about 0 8 T_meι_t to about 0 98 T_meu The forging also compπses forging at a strain rate in a range from about 5xl0^"2 s^'1 to about 5xlO^"5 s^"1 The piston being formed with a configuration that enables other parts to be connected to the piston The initial billet compnses at least one of coarse grain silicon, intermetallic particles, and injected hardening particles having at least one of a lamellar, comprehensive shape, and fine grain silicon, intermetallic particles, and injected hardening particles being globular in shape The silicon, intermetallic and injected hardening particle volume content is in a range from about 25% to about 60%, and an average gram size of the silicon, intermetallic, and injected hardening particles is less than about 15 μm².

These and other aspects, advantages and salient features ot the invention will become apparent from the following detailed descπption, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration of piston production system, and method in which the left side of the axis is before deformation occurs, and the πεht side of the axis is after deformation has occurred,

Figure 2 is a schematic illustration of piston in a πng holder production system with a billet and πng holder in a piston die,

Figure 3 is a schematic illustration of piston in a πng holder production system with the forging of the piston crown on left side of the axis, and with the forging of the piston inner part on the πght side of the axis,

Figure 4 is a schematic illustration of fused piston production system, in which the left side of the axis illustrates before deformation, and the πght side of the axis illustrates after deformation,

Figure 5 is an exploded schematic illustration of pressing a πng holder,

Figure 6 is a schematic illustration of band-shaped piston with a πng holder;

Figures 7-12 are schematic illustrations of composite piston being forged by a process, as embodied by the invention, in which Fig 7 illustrate,, a tup- shaped inner case; Fig 8 illustrates a cup-shaped outer piston case, Fig 8 illustrates fitting an inner case into an outer case; Fig 9 illustrates a compound piston after forging; Fig. 10 illustrates a washer-shaped outer case and a cup-shaped inner case, and Fig. 12 illustrates washer-shaped inner and outer cases;

Figure 13 is a schematic illustration of a billet being fit into a piston die, as embodied by the invention;

Figure 14 is a photograph of vaπous sized billets as produced by the piston production method, as embodied by the invention;

Figure 15 is a photograph of cross-sectional pistons with brackets, as embodied by the invention,

Figure 16 is a photograph of a silumins microstructure with silicon and intermetallic particles having a size less than about 6 μm², and

Figure 17 is a photograph of a silumins microstructure with silicon and intermetallic particles sized less particles having a size greater than about 15 μm²

DESCRIPTION OF THE INVENTION

A piston production method and its associated system, as embodied by the invention, enables pistons compπsing silumin alloy to be produced The piston production method can form pistons by forging The silumm-alloy pistons that are produced by forging, as embodied by the invention, compπse varying mechanical properties and characteπstics combined in one piston These mechanical properties and characteπstics may be further dependent upon a silumin-alloy piston's initial configuration and microstructure Also, mechanical properties and characteπstics may be dependent upon a silumin-alloy piston's configuration and microstructure produced by deformation treatments in the piston production method, as embodied by the invention.

The piston production method, as embodied by the invention, is schematically illustrated with the piston die system of Fig 1 In Fig 1, the piston die system compπses a piston die matπx 1, a piston die 2, a pusher 3, a heater element 4, at least one lmer plate 5, a billet 6, and forged piston 7 Figure 2 also illustrates features of the piston die system and related structures for the piston production method, as embodied by the invention. Figure 2 illustrates a πng holder 8, a spπng 9, a piston die matπx guide 10, a piston billet with πng groove 11, a piston blank, πng holder, and crown 12, and a piston compπsing a πng holder 13 Figure 3 illustrates fused mateπal 14 that has been formed by a piston production method, as embodied by the invention

Further features of the piston die system and related structures are illustrated in the remainder of the figures These features include an aligning flange 15, a partially formed billet inner part 16, a πng 17, a band-shaped πng holder 18, a cup-shaped billet outer case 19, a cup-shaped billet inner case 20, a washer-shaped outer billet case 21 , and a washer-shaped inner billet case 22.

The silumin-alloy piston production method, as embodied by the invention, can produce silumin-alloy pistons by forging fully formed pistons including structural reinforcements features (hereinafter "reinforcements") The reinfotcements compπse, but are not limited to, πng holders and piston brackets. The piston production method, as embodied by the invention, can be used to form pistons of varying sizes, for internal combustion engines, such as pistons used in automobiles, aeronautical and maπne applications, and large treaded machinery. The piston production method, can increase piston production efficiency by providing pistons with mechanical properties and characteπstics that meet those desired mechanical properties and characteπstics for an intended application.

The piston production method, as embodied by the invention, compπses forging a billet, which can compπse an aluminum alloy composition. The aluminum alloy composition compπses at least one of silicon, intermetallic particles, and injected hardening particles. The following descπption of the invention will describe an aluminum alloy composition as set forth above, however other compositions are within the scope of the invention. The particles can be provided in a lamellar configuration. The composition for the initial billet, for example an aluminum alloy composition, may also comprise at least one of fine silicon, intermetallic particles, and injected hardening particles. The injected hardening particles can be generally globular in configuration.

The forging step of the piston production method can be followed by a heat treatment step. In the piston production method, as embodied by the invention, the forging can produce large-sized pistons and pistons that comprise reinforcements. The piston production method also permits pistons to be formed with a configuration that enables piston components to be readily connected with the piston. The forging is typically conducted in a temperature range from about 0.8 T_meι_t to about 0.98 T_meι, of the piston material. The forging of the piston production method is generally conducted with a strain rate of in a range from about 5xlO^'2 s ' to about 5x10 ³ s '. The piston production method may also compπse forging steps that are conducted under super-plasticity or common hot deformation conditions These conditions are generally provided if at least one of silicon intermetallic particles, and injected hardening particles have a volume content in a range trom about 25% to about 60% of the aluminum alloy composition, with an average gram size ot silicon intermetallic particles, and injected hardening particles less than about 15 μm² If the billet mateπal composition includes a particle content and size that is outside of the above ranges, forging may be conducted under hot deformation conditions Thus, a larger a silicon or particle size can provide forging steps with a lower strain rate For example, forging with a strain rate in a range from about 10^'J s ' to about 5 10 ^ s ' and a lower forging temperature range, for example a temperature range from about 0.83 T_meι, to about 0.89 T_raeit can be conducted

Billet mateπal composition and configuration characteπstics can be considered in determining piston production method parameters. For example, if a billet mateπal composition compπses a particle weight content that is greater than about 20% and an average gra size that is greater than about 15 μm^", the initial billet configuration and the disposing of a billet into a forging device can be considered for piston production. These billet mateπal composition and configuration characteπstics may decrease deformation that occurs dunng a piston production method, as embodied by the invention The piston production method, which can include forging, as descπbed above, may compπse a one-step process The piston production method that includes a one-step process can be conducted under hot deformation and super-plasticity conditions.

Alternatively, the piston production method can be conducted in a temperature range from about 0.90 T_men to about 0.98 T_meit and at strain rate in a range from about 5xl0^'2 s ' to about 10 ³ s ' These temperature and strain rate ranges are employed with a piston production method that uses billet mateπal composition compπsing at least one of silicon, intermetallic particles, and injected hardening particles with an average grain size that is less than 6 μm² In the piston production method of a billet with such a billet mateπal composition, the billet can undergo pπmary deformation before forging steps The pπmary deformation can occur in a temperature range from about 0 79 T_meι_t to about 0 86 T_meι_t and in a strain rate range from about 5x 10 ⁴ s ' to about 5x10 ³ s '

Alternatively, the piston production method, as embodied bv the invention, can form pistons from a billet that compπses a billet mateπal composition with at least one of average grain sized silicon, or intermetallic particles, and injected hardening particles with a size that is in a range from about 6μm" to about 15 μm² The parts per million (ppm) for this billet mateπal composition can compnse hot deformation forging that is conducted in a temperature range from about 0 84 T_meι, to about 0.96 T_mei_t and in strain rate range from about 10 ³ s ' to about 5x 10 ⁴ s '

Further another alternative of the piston production method, as embodied by the invention can form pistons a billet that compπses at least one of silicon, intermetallic particles, and injected hardening particles with an average grain size less than about 15 μm², and where the injected hardening particles have a generally globular configuration In this aspect of the piston production method, as> embodied by the invention, a volume percent of silicon particles, intermetallic particles, and the injected hardening particles is in a range from about 25% to about 60% With such a billet matenal composition, the piston production method compnses forging conducted under super-plasticity conditions in a temperature range from about 0 88 T_meu to about 0 98 T_meι_t and m strain rate range from about 5x 10 ⁵ s ' to about 1x10 's '

Furthermore, the piston production method can form pistons from a billet that has a billet mateπal composition compπsing at least one of silicon, intermetallic particles, and injected hardening particles with volume less than about 15% of the total billet mass This piston production method, as embodied by the invention, can use the billet matenal that can be provided with a generally tapered- cone configuration. The billet, which can be a casting, compπses a billet matenal composition with a configuration that contact of the billet and the piston die matnx is achieved only by side surface, that is more than about 30% of its area A gap distance that can occur in the piston production method between a billet's lower butt end a ,d a piston die matnx base The gap distance can be determined by the billet mateπal configuration For example, the gap distance can be determined with respect to the size and content of at least one ot the silicon particle. intermetallic particles, and hardening particles This gap distance is generally is equal to:

h=dK7CVF

where d is an internal diameter of the bottom of the piston die matnx, (mm), C is a content of at least one of silicon, intermetallic particles, and hardening particles injected, (% for mass); F is an average area of at least one of silicon particles, and intermetallic particles, and injected hardening particles (μm²); and K is a coefficient that is reflective of the shape and size of a forging piston die-bit and is typically provided in a range from about 0.5 to about 10. Therefore, with a billet that compnses an average grain size of silicon, intermetallic particles, and injected hardening particles that is less than about 15 μm², any deformation is generally at a certain temperature essentially equal to a quenching temperature Any quenching cooling that is immediately after the deformation process can complete the piston production method.

If a billet compπses average grain size of silicon, intermetallic particles, and injected hardening particles less than 15 μm², and contains less than 15% silicon particles, intermetallic, and injected hardening particles, a πng holder can be made from alloys containing about 20% to about 45% by volume silicon, intermetallic particles, and injected hardening particles, with a size of 20 μm" In addition, a πng holder for the piston production method, as embodied by the invention, can be mounted with an interference fit on a piston side and against a butt end of a piston die matnx surface Thus, any hot deformation forging can be conducted and may result in a piston crown being shaped first followed by an inner part.

The piston production method, as embodied by the invention, can be used with a billet matenal composition that compnse silicon, intermetallic particles, and injected hardening particles with an average grain size are less than about 15μm^~ and a volume in a range from about 25% to about 60% In this combination, a πng holder compπsing an alloy having silicon, intermetallic, and injected hardening particles with an average size less than 20μm² and in a volume range from about 20% to about 45% can be used. If the πng holder is mounted with an interference fit on a piston side and disposed against a butt end of the piston, the forging steps can be conducted under super plasticity conditions. Therefore, the piston crown can be shaped followed by shaping of an inner part of the piston.

A billet that comprises silicon, intermetallic particles, and injected hardening particles with an average grain size are less than about 15μm² and that contains less than about 15% silicon, intermetallic, and injected hardening particles, can use a ring holder made from pig-iron or steel. Additionally, a πng holder can be mounted with an interference fit on a side and against a butt end of the piston die matπx in the piston for such billet. Any forging of the piston in the piston production method, as embodied by the invention, can be conducted under super plasticity conditions. Therefore, the piston crown can be shaped first and then followed by shaping of the inner part of a piston.

A billet that compπses silicon, intermetallic particles, and injected hardening particles with an average grain size less than about 15μm² and that contains silicon, intermetallic, and injected hardening particles in a range from about 25% to about 60%, can use a ring holder made from pig-iron or steel. Additionally, a πng holder can be mounted with an interference fit on a side and against a butt end of the piston die matrix in the piston for this type of billet. Any forging of the piston in the piston production method, as embodied by the invention, can be conducted under super plasticity conditions. Therefore, the piston crown can be shaped first and then followed by shaping of the inner part of a piston.

Another aspect of the invention can provide aligned surfaces of a πng holder and piston's body billet that comprise a conical shape. The conical shape may comprise an angle in a range from about 1° to about 10°. The body's billet can be made with a ring shoulder having a negative angle in a range from about 1 to about 3°. The nng holder can be placed into a πng shoulder with an interference fit size in a range from about 0.1mm to about 0.2mm in diameter. The positioning of the ring holder is generally conducted at room temperature in the piston production method, as embodied by the invention.

The piston production method that comprises forging can be conducted in two steps. First, the forging can comprise placing a ring holder in a piston die matrix. The placing step can be followed by providing an interference fit between the ring holder's outer surface and an inner surface of the piston die matrix. The interference fit can be calculated as follows:

1.0017< d/D < 1.0035

where d is a ring holder outer diameter at a forging temperature, and D is a piston die matrix inner diameter at the forging temperature. The forging can be conducted by physically moving the piston die matrix in the forging direction with the ring holder being fixed during any subsequent piston crown forging.

The ring holder in the piston production method, as embodied by the invention, can be coated with a layer of an aluminum-containing alloy. The coating and piston case can be made from essentially the same composition.

Two billets can be used to forge a piston with an inner and outer case by the piston production method, as embodied by the invention. For example, and in no way limiting of the invention, a billet for the piston production method can comprise about 15% (total) silicon, intermetallic particles, and injected hardening particles. This billet can be used to make a piston outer case. Another exemplary billet material composition comprises about 15% (total) silicon, intermetallic particles, and injected hardening particles. This billet material composition can be used to make a piston inner case, in which the outer case can be mounted by an interference fit to a side surface of the piston. The piston production method, which comprises forging of two billets, can use a billet having an exemplary billet material composition with about 45% to about 60% (total) silicon, intermetallic particles, and injected hardening particles by volume. This billet material composition can be used to make the piston outer case. An exemplary billet material composition comprises a range of about 25% to about

40% (total) silicon, intermetallic particles, and injected hardening particles by volume can be used to make the piston inner body. While forging such a piston, the piston die can be heated to a temperature that enhances deformation of an inner billet, such as under super plasticity conditions. The piston die matrix can be heated to a temperature that enhances deformation of the outer billet under super plasticity conditions. Further, this piston production method can use billets that are generally washer shaped. Alternatively, piston production method, which comprises forging of two billets, can use billets that are cup-shaped with an outer cup-shaped billet comprising a taper to a butt end of the billet. In the piston production method, which comprises forging of two billets, pressing an inner cup into an outer cup can complete an assembly of a compound billet, as embodied by the invention.

The billet for the piston production method, as embodied by the invention, can include a protuberance, shoulder, or other extension. The shoulder's surface can comprise a wave-shaped surface, with a wave period L (Fig. 6). A billet material composition with an increase of silicon, intermetallic, particle size, and injected hardening particles may result in an increase in wave period L. For example, the piston production method, as embodied by the invention, can further employ a steel washer, spacer, or other separating device. The spacer can be placed on the shoulder's surface. The washer's thickness generally satisfies the following condition:

IJl=4-42.

Additionally, a relationship between the billet's height and shoulder can be determined so that a wave-shaped washer can be on a same general .level at the piston's compression ring groove when forging is complete. A billet with silicon, intermetallic particles, and injected hardening particles having an average gram size less than about 15μm^" can be placed in a piston die matnx against a bracket, in which the bracket mirrors a billet's surface This oπentation results in a lock joint being formed after the piston has been forged for example forged using hot deformation. The bracket surface area S that is created in the formed lock joint can be determined by the formula:

S=KP/SιnαF,

where P is a separation force required to overcome a dynamic force created dunng motor performance; K is a reliability coefficient; F is a aluminum alloy flow resistance at a working temperature; and a is an angle between a shoulder and a piston movement direction.

Alternatively, a billet with silicon, intermetallic particles, and injected hardening particles having an average grain size less than about 15μm² and that comprises a total volume content of silicon, intermetallic, and injected hardening particles in a range between about 25% and about 60% can be placed in a piston die matrix dunng a piston production method, as embodied by the invention The placement can include placement against a bracket that mirrors a billet's surface This placement can result in a lock joint being formed after the piston has been forged under super-plasticity conditions. The bracket surface area S may be determined by the formula:

S=KP/SinαF,

as above.

As another alternative, a billet with silicon, intermetallic particles, and injected hardening particles having an average grain size less than about 15μm", and comprising a total volume silicon, intermetallic, and injected hardening particles in a range from about 25% to about 60%, can be placed in a piston die matnx against a bracket. The bracket can be formed from a porous ceramic mateπal, such as a porous ceramic mateπal that is infiltrated with an aluminum alloy The porosιt\ of the porous ceramic mateπal is in a range from about 35% to about 50% Thus, forging in the piston production method, as embodied by the invention, can be conducted under super-plasticity conditions The same aluminum alloy composition can used for infiltration of the porous ceramic mateπal as is used in production of a piston case

After forging steps, a piston that is formed by the piston production method, as embodied by the invention, can be subjected to turther deformation Foi example, the further deformation compnses deformation in a close-end piston die at a strain rate in a range from about 10 ⁵ s ' to about 10 ^"4 s^"1 for at time in a range from about 0.5 minutes to about 5 minutes. For billet matenal compositions compπsing silicon, intermetallic particles, and injected hardening particles having an average grain size less than about 15μm², a hardened layer can be deposited on a piston surface. In this scenano, hot deformation forging can be conducted at a temperature of in a range from about 0.9 T_meι_t to about 0.96 T_meι_t and at a strain rate in a range from about 5 x 10 ² s ' to about 10 ³ s^'1.

The piston production method, as embodied by the invention, can enhance forging conditions in the production of pistons This enhancing can be conducted by consideπng a billet's initial microstructure and chemical composition Expeπments reveal that desired forging temperature intervals may be provided to develop desirable mechanical properties Forging of complex-shaped and large-sized billets can be achieved in the above-descπbed temperature and strain rate intervals, while conducting techniques of disposition of the billet in the piston die, as embodied by the invention.

Pistons, such as simple shaped pistons that are unhaidened oi ithout reinforcing elements added thereto, can be employed in low-rated motors. These pistons can be produced from billets by mold casting, in a further piston production method, as embodied by the invention. This piston production method can produce pistons with relatively low manufactuπng costs Casting is the most inexpensive method of billet production The raw mateπal for mold casting can compπse a coaise microstructure compπsmg silicon, intermetallic particles w ith an av erage gi in size greater than about 15μm

For example, silumins comprising this microstructure typically exhibit low levels of plasticity under hot deformation conditions These silumins also ma\ exhibit high plasticity at temperatures in a range from about 0 86 T_meι_t to about 0 91 ot

T_mei_t and at a strain rate in a range from about 10 's ' to about 5x10 ^"" s ' Fine-grained structured silumins, with particles compnsing an average grain size less than about 6 μm², may exhibit higher plasticity and may be is acceptable for use in production of complex- shaped pistons and large pistons If the piston production method compπses pre-forged billets with this microstructure, continuous casting and hot deformation forging can be provided, for example, by a pressing step A decrease in alloy particle size can permit an increase in a deformation temperature range The temperature and strain rate at which deformation forging in the piston production method is conducted can influence a silumin mateπal's mechanical properties These influenced properties can be recognized after the forging step of the piston production method following any subsequent heat treatment

The piston production method, as embodied by the invention, can produce pistons from fine grain microstructure alloys The fine grain microstructure alloys can develop desirable mechanical properties after deformation in a temperature range from about 0 9T_meι_t to about 0 96 T_meι_t and strain rate in a range from about 5 x

10^"2 s-¹ to about 1 x 10³ s-¹. These properties, which are formed in the above- descπbed ranges, can be attπbutable to a formation of micropores in the billet mateπal near silicon, intermetallic, and injected hardening particles. The micropores can form under high temperature deformation conditions of the piston production method The micropore size can increase with a decrease in an applied strain rate dunng the piston production method This decrease can be attπbutable to the mechanical properties that are attained at high strain rates, as embodied by the invention.

Conversely, the piston production method can also produce pistons from coarse grain microstructure alloys. It has been determined that coarse grain microstructure alloys can develop desired mechanical properties alter deformation at a strain rate in a range from about 10 ^J s ' to about 5 x 10² s Further, detormation conditions for an billet matenal composition compnsing silicon, intermetallic particles, and injected hardening particles with an average gra size in a range from about 6μm² to about 15 μm² have also been determined These deformation conditions compπse deformation at a temperature in a range from about 0 84 T_II |, to about 0.96 T_meit and at a strain rate in a range from about 10 ³ s ' - 5 x lO ³ s '

A fine gram alloy for the piston production method that compπses silicon, intermetallic particles, and injected hardening particles with an average grain size less than about 6 μm² in the billet can be produced by hot deformation of cast billets, in which the cast billets compπse a coarse lamellar grain microstructure The piston production method conditions for deformation forging of such silicon and intermetallic particles are at a temperature in a range from about 0 79 T_melt to about 0.96 T_mei_t and at a strain rate in a range from about 5xl0^"4s ^l to about 5xl0^"3 s ^''.

The piston production method, as embodied by the invention, can be used to produce pistons, which compnse vanous compositions, microstructures. and grain sizes, under super-plasticity conditions. For example, and in no way limiting ot the invention, pistons compπsing bπttle mateπals for example eutectic silumins reinforced with hardened particles can be produced by the piston production method, as embodied by the invention Alternatively, pistons compπsing a complex shape and being hardened with low stress-flow mateπals, which are matenals that decrease nng holder deformation and displacement relative to the piston itself, can be formed by the piston production method, as embodied by the invention As a further alternative, pistons compπsing a large size that are stamped by low iorce presses can be toi ed by the piston production method.

Super-plastic deformation conditions for the piston production method, as embodied by the invention, may be used with silicon, intermetallic, and injected hardening particles compnsing an average grain size that is less than about 15 μm" Further, super-plastic deformation conditions compnse a volume ol silicon, intermetallic, and injected hardening particles in a range between about 25% to about 60% A strain rate in a range from about 5x10 ⁵ s ¹ to about 5x 10 ^J s ', and a deformation temperature in a range trom about of 0 88 T_me|_t to about 0 98 T_meι_t can be used as super-plastic deformation conditions for the above-noted grain size

The piston production method, as embodied by the invention can torge billets that compπse greater than about 15% by weight ol silicon, intermetallic, and injected hardening particles, all of which have an average grain size of more than about 15 μm² Such a billet mateπal composition typically exhibits low levels of plasticity Dunng the piston production method, contact between the piston billet and piston die matnx's surfaces should occur within about 30% to about 100% of a side surface area, until a piston die-bit contacts a butt end This contact should prevent at least one of billet cleaving and formation of cracks

Further, the piston production method should provide a maximum distance between a billet base and piston die matnx base. The distance generally is dependent on a plasticity of the billet mateπal composition, for example, but not limited to at least one of a quantity and size of silicon, intermetallic, and ιn]ected hardening particles, a billet diameter, and a size and shape of the piston die A shorter distance between the base of a piston billet and base of a piston die matπx can be provided if the billet mateπal composition is bπttle This distance is desired to prevent distortion of the billet as a piston die bit is disposed in the piston die matnx

The piston production method, as embodied by the invention, can compnse quench-coo ng after forging is complete, if a piston has been forged at an essentially same temperature for quenching This procedure reduces piston production method time since a heating for quenching step will be redundant, and thus can be skipped Further, an absence ol "heating for quenching" can prevent crystal growth in solidifying aluminum of the billet mateπal composition This procedure may also provide a finer grain microstructure in a final piston

Ring grooves in the piston can be reinforced in the piston production method for limiting disintegration of piston πng grooves while a motor operates The πng grooves can be reinforced with metal nng holder, which provide strength at working temperature that is generally is greater than that of the billet matenal For example, if a piston is formed as a casting, a nng holder can usually compnse pig-iron that is reinforced by coating formed by molten metal Alternatively, if a piston is forged, a πng holder can compnse a microstructure including coarse grain silumin with silicon, intermetallic, and injected hardening particles, since silumin typically possesses higher strength charactenstics than the piston billet matenal

For example, fine grain sihmins or intermediate mateπals with silicon, intermetallic, and injected hardening particles that have an average grain size less than about 15 μm², and that compπse silicon, intermetallic, and injected hardening particles less than about 15% volume can be used in a piston production method, as embodied by the invention. These matenals can exhibit plasticity that can enable forging with a πng holder formed from silumins The silumin can compπse about 20% to about 45% silicon, intermetallic, and injected hardening particles, with silicon, intermetallic, and injected hardening particles having an average grain size greater than about 20 μm²

The nng holder can be placed on the billet, and placed with billet into the piston die matπx. An interference fit can be established between a piston billet surface and butt end sides of the piston die matπx to prevent the blank from cracking A piston crown can be formed first and enable a πng holder to be located on a billet and avoid deformation Stress on the billet mateπal is typically lower than that applied to reinforcing πng holder mateπal dunng any hot deformation treatments Thus, the reinforcing matenal will fill a space around the πng holder, in which the πng holder normally undergoes minimal deformation, such as less than about 20% A piston billet with a "microduplex structure", which means that the billet compπses a billet mateπal composition having a volume content of particles in a range from about 25% to about 60%, can undergo piston production method, as embodied by the invention, under super-plasticity conditions In this piston production method, forging is conducted with a press and a πng holder expeπences less deformation A ring holder, which compnses at least one of pig iron and steel, with an average grain size of the silicon, intermetallic, and injected hardening particles less than about 15μm^", an be used with the piston production method to prevent ring holder relocation and avoid ring holder deformation or destruction. To accomplish this prevention, a ring holder can be inserted into a piston die matrix with an interference-fit on the side surface and against butt end surface. The piston crown is forged first followed by the piston inner part under super-plasticity conditions, which simplifies forging.

A reliable joint should be formed between a ring holder and piston in piston production method, as embodied by the invention. Such a joint can be created by piston material filling a ring holder cavity followed by joint deformation. If an oxide film is provided on the ring holder, such as by previous treatments, removal of film occurs when the ring holder is placed on the piston blank. Mating surfaces of the ring holder and piston blank can be cone shaped with a conical angle in a range from about 1° to about 10°. The piston and billet ring shoulder can comprise a negative angle in a range from about 1° to about 3°. Further, the ring holder can be pressed with a temperature in a range from about 15°C to about 540°C with an interference fit in a range from about 0.1mm to about 0.2mm at the diameter. The forging conditions, as embodied by the invention, can produce reliable diffusion joint between the ring holder and piston. The negative angle prevents mating surfaces of the butt end of the ring holder and piston billet from oxidizing during heating and forging. A closed cavity can then form because of different shapes between a lower end of the ring holder and ring shoulder. Additionally, contact of these surfaces with furnace atmosphere is prevented, which can lower piston billet and ring holder oxidation rates during forging.

Further, deformation at the ring holder base and shoulder can occur during forging because of shape differences. The deformation can reduce the oxide film, and in turn, promotes formation of a diffusion joint between the ring holder base and shoulder surface. Forging a piston with nng holder can be conducted in a two-stage piston production method. First, the billet can be placed butt end against the piston die with its πng groove zone disposed upwardly. A piston die stamps the piston crown that is followed by the πng holder being pressed. The piston blank can then be inverted so the crown now faces downwardly, and a second piston piυductiυn stage commences with the formation of the piston inner.

The nng holder can be located in the piston die matnx where by an interference fit forms between the nng holder outer surface and piston die matnx inner surface. This disposition can prevent a nng holder from cracking, while the piston is undergoing hot deformation treatment. The disposition can also prevent distorting caused by vanations in metal flow rates dunng formation of the piston inner. The interference fit characteristics can be calculated as follows:

1.0017≤ d D ≤ 1.0035

where d is the nng groove outer diameter at forging temperature and D is the piston die matπx inner diameter at forge temperature.

If an interference fit is less than desired, cracking and distortion of the ring holder may occur. A close interference fit may complicate insertion of the piston billet with ring holder within the piston die matπx. If the piston production method compπses placing a ring holder on a cylmdπcally shaped billet with very little or no gap therebetween, the piston die matrix can provide enhanced πng holder stability during the piston production method, as embodied by the invention. This oπentation can also prevent uneven metal distπbution above and below a πng holder. This orientation, in combination with a ring holder position dunng forging, can provide a stable platform for the ring holder.

Aluminum may be diffusion coated on the πng holder. The diffusion coating at high temperatures can provide the aluminum, for example man aluminum alloy for penetrating the steel ring holder. This procedure may remove oxide films from the aluminum alloy piston and πng holder surfaces. To enhance piston case and πng holder joint reliability, any alloys for example for coatings, used in the piston production method, as embodied by the invention, should possess a similar it not the same coefficient of linear extension

A two-layer piston configuration, and the piston production method used to form such a two-layer piston configuration, can provide reliable piston performance dunng initial motor startup The two-layer piston configuration can also provide enhanced reliability when a motor is hot and under stress A two-layer piston configuration with high silicon, intermetallic, and injected hardening particle content can provide desired strength characteπstics at operating temperatures However, at low temperatures, such as when a motor is initially started, mateπals used for the two- layer piston configuration may offer low levels of plasticity. However, a two-layer piston configuration compπsing an alloy with low silicon, intermetallic, and injected hardening particle content that has a high plasticity level can offer fatigue resistance

Dunng motor startup and warming, the two-layer piston configuration can transmit wπst pm forces to a piston inner portion. The piston inner portion can be formed from an alloy compnsing low silicon, intermetallic, and injected hardening particles. A motor with pistons formed by the piston production method, as embodied by the invention, dunng operating can achieve a temperature in the nng groove zone m a range from about 250°C to about 350°C, and higher if fully stressed The piston outer case alloy compnses a composition with high content silicon, intermetallic, and injected hardening particles that can prevent at least one of the piston nngs from destroying a piston πng groove and piston base from burning out at high operating temperatures.

Vaπations in a piston thickness can be determined to enhance piston production method characteπstics, piston wear resistance, and plasticity For example, a working temperature while the motor operates around a piston lower edge can be lower than the temperature at a πng groove zone. Dunng cold startup of an engine, a piston skirt lower edge can be subjected to impact stress as the piston moves from top deadcenter through to bottom deadcenter This stress may cause a piston skirt lower edge to comprise a material with a high plasticity and sufficient resistance to wear. These characteπstics can be provided by minimizing a piston outer body thickness. If the plasticity is sufficient for forging, piston billets can be washer shaped (as discussed above) since the shape is conductive to forging. Conv ersely, if alloy plasticity is insufficient for either forging or pressing, the piston billets can be cup shaped.

Assembling a compound piston billet before forging can facilitate removal of oxide films that coat inner and outer case contact points. The removal may comprise pressing an inner case into an outer case. The exemplary forging steps for producing a diffusion joint may comprise providing a wave-shaped piston billet.

The billet shape can be provided by a low weight piston and reinforced ring holder. The ring holder reinforcement blank can also comprise a thin washer placed on the wave-shaped piston billet butt end. After initial forging, this washer also assumes the wave shape. During forging of the piston crown, molten metal from the piston billet can pour between the washers. The molten metal can fill any space between the washers. Moreover, during forging of a blank comprising silicon, intermetallic. and injected hardening particles with an average grain size about 15 μm², a gap free joint 1 around the ring holder with an interval of: 1/1 = 4 - 14 may result. Forging a blank with average grain sized silicon, intermetallic particles, and injected hardening particles with an average grain size greater than about 15 μm² can create a gap free joint with ring holder. The gap free joint 1 comprises an interval that is determined by 1/1 = 15 - 42.

A piston production method that utilizes a washer, as discussed above, can comprise steps of cutting a groove in the washer, for accepting a compression ring. A compression ring is in physical contact with a ring groove and can decrease a ring groove wear rate. A ring holder weight and groove ware rate can be enhanced by a reinforcement washer.

A piston production method, can also comprise attaching a bracket, which is formed of heat resistant material, to a piston case. The attachment can compnse any appropnate means, such as but not limited to attaching by bolts This bolt attachment step can be time consuming and costly, therefore the piston production method, as embodied by the invention, can compnse attaching brackets to the piston The brackets can be formed as integral flanges, so the bracket can be attached to a piston without bolts The formed mechanical joint can be created by a flange surface area, and its onentation relative to a dynamic force generated dunng motor operation The joint can overcome inertia withm a motor, and thus should be sufficient to hold a bracket and piston case together. Pounng ol molten piston mateπal into the bracket cavity dunng forging in the piston production method, as embodied by the invention, can provide for super-plastic deformation conditions, including those discussed above.

Brackets can compnse porous ceramic mateπals, which can be infused with aluminum alloy in order to reduce its weight. The ceramic mateπal can compnse an open porosity with a porosity value in a range from about 35% to about 50% to provide frame strength. The infusing of the ceramic matenal frame with aluminum alloy can be followed by bonding an aluminum layer to a surface, which can mate with the piston case. This bonding step can result in a diffusion joint formed between the bracket and piston case after deformation If both the infusion mateπal and piston case compπse the same composition, then the formed joint reliability can be enhanced because differences in coefficients of the linear extension have been eliminated

Additional deformation in a close end piston die, for example those exposed to compression from all sides, can be applied under a strain rate in a range from about 10 ^"5 s^"1 to about 10 ^"4 s ^~l for time peπod in a range from about 0.5mιn to about 5mιn This time peπod can result in elimination of micropores, which may result in enhanced mechanical properties in the piston.

Wear in the πng groove can be attπbuted to a decrease in piston alloy strength. The decrease results from exposure to high temperatures dunng the piston production method. An increase in matenal strength at the nng groove zone can be provided by plasma welding. The plasma welding compnses melting of mateπal in a πng groove zone often relying on a plasma arc. This plasma welding can be followed by alloying element injection into the melt. However, these steps of mateπal melting and resultant properties are essentially the same for hot deformation and cast pistons. Any differences therebetween may result when fusing steps are used on a piston billet and not used on the piston case.

A fused material may be characterized by large feπous or nickel-based intermetallic plates, and shrinkage holes. Deformation of the fused material can be conducted while the piston is being forged. The deformed fused material may possess levels of hardness and ultimate strength that often remain the same even after heating to up to temperatures of about 250°C. Any enhanced characteristics in the material can be attributed to a dispersed microstructure as intermetallic particle fragmentation can occur during hot deformation treatments. Further, enhanced characteristics can also be attributed lack of stress points, such as but not limited to shrinkage holes. The absence of shrinkage holes can contribute to an increase in a material's ultimate strength, since the absence can increase the materials' plasticity.

A set of examples of piston production methods within the scope of the invention will now be described. The following operative steps for the piston production method, as embodied by the invention, should not be construed as limiting, but merely provide guidance to steps within the scope of the invention. The values set forth below are approximate, unless specified as exact.

A piston blank and piston die can undergo primary heating. Any deformation is conducted under isothermal conditions. The forging temperature is selected dependent on a piston blank initial microstructure and configuration. The billet shape can depend on billet material composition and average grain size of the silicon, intermetallic particles, and injected hardening particles therein. The subsequent heat treatment steps for the piston production method comprises quenching and artificial aging.

Example 1. A cylindrical piston billet comprising an approximate alloy composition of 12% Si, 2.2 % Cu,. 1.1% Mg, 0.1% Ti, 1.1% Ni, 0.4% Mn, 0.8% Fe, with Al as a balance. The billet was cut from a bar of stock. This bar was made by hot pressing an ingot at 440°C or 0.86 T_meit with a strain rate of 90%s^''. T_meι_t for the above alloy is equal to 552°C and was chosen from a phase diagram for Al- and Mg-based systems. The resulting billet's microstructure compπses globular silicon and intermetallic particles with an average gra size of about 5 μm². The billet was deformed in a piston die system, as in Fig. 1, at 520°C (0.96 T_meu) with a strain rate of lxlO^"2 s^"1. Quench cooling occurred in water at 20°C was conducted after the deformation process. Aging was conducted at 210°C for 10 hours. Microstructural analysis of the matenal indicated an absence of defects, such as microcracks and micropores. The matenal had the following mechanical property: σ_b = 390MPa.

Example 2. A piston billet of alloy composition compnsing 21%Si,

1.6%Cu, l.l%Mg, 0.1%Ti, l.l%Nι, 0.5%Mn, 0.7%Fe with Al as the balance was made by block mold casting. An average grain size of silicon and intermetallic particles is about 120 μm² with lamellar shapes. The billet was tampered to a cone shape with a 4° angle. The billet size was such that when fit into a piston die matrix, which has an inner diameter of 150mm and a cone angle of 4°, 50% of the surface area made contact with the piston die matrix. A distance from the billet's lower butt end to that of the piston die matrix lower butt end may be determined as:

H = dK/C F,

where d = 150, K = 5, C = 21, F = 120. The distance was calculated at 3.2 mm. The billet was deformed in a piston die system (Fig.l) at 480°C (0.91

T_mei_t) at an average strain rate of lxlO^"4 s ^"'. The heat treatment sequence included quenching at 510°C and aging at 210°C for 10 hours. The resultant piston was determined to be essentially defect free. Further testing showed that σ_b = 250MPa.

Example 3. A billet with comprising an part was forged at a temperature of 520°C (0.96 T_meit) and strain rate of lxlO^"2 s^'1 from a cylindrical blank in the piston die system of Fig 1. The blank was cut from a pressed ingot. The pressing temperature was in a range from about 440 to about 450°C (0.86 T_mei_t to about 0.88 T_me.t) with a strain of 90%. The ingot composition compnsed 12%Sι, 2 2%Cu, 1 l %Mg, 0 l%Tι, 0 4%Mn, 0 8%Fe with Al as a balance, and compnsed an average grain size ot silicon and intermetallic particles about 6 μm² Mechanical treatment to the head of the billet's conical surface with nng shoulder was conducted to form a cone angle about 6°, and negative shoulder angle of about 3° A nng holder with a flat lower butt end was formed from aluminum alloy with about a 18% silicon content The πng holder was pressed into the billet's head using a πng against the shoulder at 20°C

In this seπes of above-descnbed steps, a closed cavity was formed between the flat butt end of the πng holder and billet's nng shoulder The billet with pressed πng holder and can be heated in a furnace to a temperature of 510°C The billet was fit in a piston die system with simultaneous pressing of the nng holder and forming a piston fire chamber Forging was conducted under isothermal conditions at 510°C (0 95 Tmei_t) using a hydraulic press with strain rate of 10^"3 s ' After forging the πng holder, the piston was quenched in water and aged at 210°C for 10 hours Strength testing revealed the joint between the piston body and πng holder to be

140MPa.

Example 4 A piston blank compπsing aluminum alloy with a composition compnsing 12%Sι, 2 2%Cu, 1 l%Mg, 0 l%Tι, 1 l%Nι, 0 4%Mn, 0 8%Fe, with Al as a balance is used in a piston production method The alloy compnsed an average grain size of silicon and intermetallic particles at 5μm² and the grains were globular in shape. An aligning protuberance was formed on the piston, and a pig-iron πng holder was installed against the protuberance The pig-iron nng holder was installed by pressing the nng holder into the protuberance Pnor to its installation on the billet, the πng holder was coated with a layer of aluminum alloy melt, which compπses essentially the same composition as the billet The billet with nng holder was fit into the piston die matπx with an interference fit therebetween Forging was conducted under hot deformation conditions at 490°C (0 93 T_meu) with a average strain rate of 10^"3 s ' The piston crown was formed first (left side of Fig 2), and then its inner part (πght side of the figure) Subsequently, steps ol iorging, quenching, and artificial aging were conducted An aluminum alloy can be coated on the holder in this example After cooling, the aluminum alloy coating was fusion joined to the nng groove surface As the nng holder was pressed into the piston billet, the oxide film coatings from both the piston billet and πng holder surfaces were removed. High temperature and deformation that occur dunng forging provide conditions for creation of a permanent fusion joint. The strength of this joint is typically sufficient to prevent a gap from developing between the piston body and nng holder dunng subsequent heat treatment and use.

Example 5. An aluminum alloy billet that compnsed 12%Sι, 2.2%Cu, 1.1 %Mg, 0.1%Ti, 0.4%Mn, 8%Fe and Al as a balance, further comprised an average grain size of silicon and intermetallic particles at 12μm². This billet was formed with an integral shoulder. A butt end surrounding the shoulder was wave-shaped, as described above. The ring holder was made from wave-shaped sheet steel with a thickness of 3mm. The billet and ring holder wave period was calculated using the formula:

L = 1(4-14)

where 1 is a thickness of the sheet from which a ring holder was made, for example 3 mm. Using the above-formula above, L is in a range from about 12mm to about 42mm. For the experiment, L was about 30mm. The ring holder was fixed to the blank and placed into the piston die matπx. The piston was then forged. The subsequent heat treatment included quenching and artificial aging.

Example 6. A compound piston compnsed two cases, an inner and outer case. The billet for the outer case comprised an aluminum alloy with 21%Sι, 1.6%Cu, 1.1 %Mg, 0.1 %Ni, 0.5%Mn, 0.7%Fe, with Al as the balance. It also comprised silicon and intermetallic particles with an average grain size of 30μm²

The inner case billet was formed from an alloy compπsing 12%Sι, 2.2%Cu, 1.1 %Mg. 0.1%Ti, l.l%Ni, 0.4%Mn, 0.8%Fe and a balance Al, with silicon and intermetallic particles having an average grain size of 5μm , and being globular in shape. The outer and inner case billets were washer shaped. The piston was forged by simultaneously forging both billets at 490°C (0 93 T_mell) with a deformation rate ot 10 ^' s ' Subsequent heat treatment sequence included quenching and artificial aging

Example 7 A piston billet body was made from the aluminum alloy with a composition of 12%Sι, 2.2%Cu, 1 l%Mg, 01.%Tι, 1 l%Nι, 0 4%Mn, 0 8%Fe and a balance aluminum. An aluminum alloy piston blank compnsed an alloy with a composition of 21%Sι, 1 6%Cu, 1 l%Mg, 0 l%Tι, 0 5%Mn. 0 7%Fe and a balance of Al. The alloy included an average grain sized of silicon and intermetallic particle of 120μm². A bracket made from silica mulhte with 40% porosity was infused with an aluminum alloy having a same composition as the piston billet. The inner bracket surface was coated with an aluminum alloy layer and had a thickness of 2 mm The bracket and billet were fit into the piston die piston die matnx and heated to 480°C (0.91 T_mei_t) The deformation was conducted a strain rate of 10^"4 s ' After forging quench cooling was conducted in open air. Aging was conducted at 350°C for 8 hours. The joint between piston and bracket was determined to be reliable and permanent.

Example 8. A blank cut from hot pressed aluminum alloy rod was formed with a composition of 12%Sι, 2.2%Cu, l.l%Mg, 0.1%Tι, l. l%Nι, 0 4%Mn, 0.8%Fe, with Al as a balance. The alloy compnsed an average grain size of silicon and intermetallic particles of 6μm with a globular shape. At a distance ot 20mm from an end, a piston nng section was melted, and injected with a nickel-chrome flux, for example nickel-chrome wire. Melting was conducted using a solid electrode in an argon atmosphere in a three step or 3 turns operation. The first step involved a nickel- chrome flux injection rate of 65m/hour and a welding speed of

In second and third steps, welding was conducted without injecting alloying elements, and a welding rate was 25 m/hour. Electnc current dunng the steps was in a range from about 680 A to about 700 A, and the voltage was 220 V. The melt depth was 7 mm.

A billet with a melt layer with a nickel content of 7% and chrome content of 2 % was heated in a furnace to 470°C (0.9 T_meι_t). The billet was then placed in a piston die matπx piston die mounted under a hydraulic press. Billet, joint, and melted layer deformation was conducted with a strain rate of 10^"J s^{" 1} Forging was conducted under isothermal conditions with the blank and piston die temperature at about 470°C with an average strain rate of 10 V¹. The piston was removed from the piston die with the help of a pushei Quenching w as conducted at a temperature of 510±10°C in water. Aging was conducted at a temperature of 210°C for 10 hours. Dunng final mechanical processing of the piston the nng groove was formed. No microcracks or micropores were found.

While vanous embodiments are descnbed herein, it will be appreciated from the specification that vanous combinations of elements, vaπations or improvements therein may be made by those skilled in the art, and are within the scope of the invention.

Claims

WE CLAIM

1 A piston production method for producing an internal combustion engine piston, the method compnsing

forging a billet from an initial billet compnsing an aluminum alloy that compπses silicon, intermetallic particles, and injected hardening particles, the forging is conducted under at least one of super-plasticity and hot deformation conditions,

heat treating the forged billet;

wherein the forging compnses forging at a tempeiature in a range tiom about 0 8 T_mei_t to about 0.98 T_meι_t the forging also compnsing forging at a strain rate

9 1 S I in a range from about 5x10^" s to about 5x10 s , the piston being formed with a configuration that enables other parts to be connected to the piston, and

the initial billet compnses at least one of-

coarse grain silicon, intermetallic particles, and injected hardening particles having at least one of a lamellar, comprehensive shape, an

fine gra silicon, intermetallic particles, and injected hardening particles being globular in shape,

and the silicon, intermetallic and injected hardening particle volume content is in a range from about 25% to about 60%, and an average grain size of the silicon, intermetallic, and injected hardening particles is less than about 15 μm²

2. A piston production method according to claim 1, wherein the lower strain rate is in a range from about 10^"3 - 5xl0^"5 s^"' and temperature is in a range from about 0.83 - 0.89 T_meι_t) a particle content greater than 20%, and average gram size greater than 15 μm²

3. A piston production method according to claim 1. wherein the initial billet compπses silicon, intermetallic particles, and injected hardening particles having an average grain size less than about 6 μm^", and the forging comprises hot deformation forging that is conducted in a temperature range from about 0 90 T„,_L|, to about 0 98 T_mei_t and at strain rate in a range from about 5x 10 ^" s ' to about 10 s '

4 A piston production method according to claim 3, the method further compnsing deformation at a temperature in a range from about 0 79 T_meι_t to about 0 96 T_meι_t and at a strain rate in a range from about 5x10⁴ s ^l to about 5x 10 ^J s '

5 A piston production method according to claim 1 further compπsing deformation forging at a temperature in a range from about 0 84 T_mei_t to about 0.96 T_mei_t and at a strain rate in a range from about 10 ³ s ' to about 5x 10 ⁴ s ' for billets compπsing an average gram size of silicon, intermetallic particles, and injected hardening particles in a range from about 6μm² to about 15 μm²

6 A piston production method according to claim 1 , wherein forging is conducted under super plasticity conditions at a temperature in a range from about of 0.88 T_mei_t to about 0.98 T_meit and at a strain rate in a range from about 5x10 ³ s ' to about 1x10 ^~'s ^_1 for billets compnsing an average grain size of silicon, intermetallic particles, and injected hardening particles less than about 15 μm² with a globular shape, and with a volume content of the silicon, intermetallic particles, and the injected hardening particles in a range from about 25% to about 60%

7. A piston production method according to claim 1, wherein for billets with silicon, intermetallic particles, and injected hardening particles being less than about 15%, billets compπse a tapered cone shape and are set within a piston die matπx in such way that contact of the billet and piston die matπx are in contact at side surfaces, and the contact compπses at least 30% of its area

8. A piston production method according to claim 7, wherein a distance between a lower butt end and a piston die matπx base equal to h = dK CVF,

where d is the internal diameter of the bottom of the piston die matnx (mm), C is the silicon content, and intermetallic particles, and hardening particles injected, (% for mass), F is the average area of the silicon, intermetallic particles, and injected hardening particles (μm"), and K is a coefficient that factors a shape and size of the upper die, where K is in a range from about 0.5 to about 10.

9 A piston production method according to claim 1, wherein deformation is conducted at a temperature equal to a quenching temperature, and quenching cooling occurs after the deformation for billets compnsing silicon. intermetallic particles, and injected hardening particles having an average grain size less than about 15 μm².

10. A piston production method according to claim 1, wherein billets that compπse silicon, intermetallic particles, and injected hardening particles with an average grain size less than about 15 μm², and that compπse less than about 15% silicon, intermetallic, and injected hardening particles, a ring holder can be provided in which the ring holder compnsing alloys compπsmg silicon, intermetallic particles. and injected hardening particles with a size greater than about 20 μm² in a weight range from about 20% to about 40%, and the πng holder being mounted with an interference fit on a piston die matnx surface.

11. A piston production method according to claim 1, wherein billets that compπse silicon, intermetallic particles, and injected hardening particles with an average size less than 15μm and a volume of silicon, intermetallic particles and injected hardening particles in a range from about 25% to about 60%, a nng holder compnsing silicon particles, intermetallic, and injected hardening particles with an average size less than 20μm in a range from about 20% to about 45%.

12. A piston production method according to claim 1, wherein billets comprising silicon, intermetallic particles and injected hardening particles compπse an average grain size less than 15μm² and that compnses less than 157c silicon, intermetallic, and injected hardening particles, a ring holder made from at least one pig-iron or steel is provided on the piston.

13. A piston production method according to claim 1, wherein a billet having silicon, intermetallic particles, and injected hardening particles compπse less than 15μm² and a volume of silicon, intermetallic particles, and injected hardening particles in a range from about 25% to about 60%, a ring holder comprises pig-iron or steel is provided on the piston.

14. A piston method production according to claim 12, further comprising forming aligned surfaces of the nng holder and piston's body billet with a conical shape having an angle between about 1° to about 10° and forming a ring- shoulder with a negative angle between about of 1° to about 3 °, and the ring holder is placed into the ring-shoulder with the interference fit diameter in a range from about 0.1 mm and about 0.2 mm in diameter, wherein placement of the ring holder is at room temperature.

15. A piston production method according to claim 12, wherein the forging comprises two steps .

16. A piston production method according to claim 12, wherein placement of the ring holder in the piston die matrix comprises and providing interference fit between the ring holder outer surface and piston die matrix inner surface, wherein the interference fit is calculated by:

1.0017< d/D < 1.0035

where d is the ring holder outer diameter at forging temperature, and D is the piston die matrix inner diameter at forging temperature, and forging comprises physically moving the piston die matrix in the direction of forging along with a fixed ring holder during piston crown forging.

17. A piston production method according to claim 12, further comprising coating a ring holder with aluminum alloy.

18. A piston production method according to claim 16, comprising providing the coating and piston case formed from same alloy.

19 A piston production method according to claim 1, the method compπsing providing two billets to forge a piston when a billet compπses 15% silicon, intermetallic particles, and injected hardening particles, the bi llet being used to make piston inner case, with an outer body being mounted with interference fit on a side surface.

20 A piston production method according to claim 1, wherein forging a piston compπses forging from two billets, one billet compπses silicon, intermetallic particles, and the injected hardening particles in a range from about 45% to about 60% by volume to make a piston outer case, and a billet compnsing 40% silicon, intermetallic particles, and the injected hardening particles in a range from about 257c to about 40% by volume to make the piston inner case, and dunng forging the die is heated to a temperature for deformation under super plasticity conditions

21. A piston production method according to claim 19, wherein the billets are washer shaped.

22. A piston production method according to claim 19, wherein the billets are cup shaped and an outer cup tapered to a butt end

23. A piston production method according to claim 21, further compπses wherein pressing the inner cup into the outer cup to form a compound billet

24. A piston production method according to claim 1 , wherein the billet compπses a wave shaped protuberance with a wave penod L, and a steel washer disposed on the surface, wherein washer has a thickness that satisfies the following condition

IJ1 = 4 - 42, wherein the relationship between a billet height and a shoulder is determined so that the washer is on a same level as a nng gioove when forging is complete.

25 A piston production method according to claim 1, wherein a billet comprises silicon, intermetallic particles, and injected hardening particles with an average grain size of less than 15μm that is placed in a piston die matπx against a bracket that mirrors the billet's surface, and results in forming a lock joint after the piston has been forged under hot deformation conditions, the bracket surface area S may be determined by:

S=KP/Sin F,

where P is a separation force required to overcome the dynamic force created during motor performance, K is a reliability coefficient, F is an aluminum alloy flow resistance at a working temperature, α is an angle between the protuberance and the direction of piston movement.

26. A piston production method according to claim 1, wherein a billet comprises silicon, intermetallic particles, and injected hardened particles with an average grain size less than 15μm² and a volume content of silicon, intermetallic, and injected hardening particles in a range from about 257c to about 607o, the billet is placed in a matrix against a bracket that mirrors the billet's surface, to form lock joint forming after the piston has been forged from aluminum alloy under super-plasticity conditions, and the bracket surface area S may be determined by:

S=KP/SinaF,

where P is a separation force required to overcome the dynamic force created during motor performance, K is a reliability coefficient, F is an aluminum alloy flow stress at the working temperature, α is an angle between plane of the protuberance and the direction of piston movement.

27. A piston production method according to claim 1, wherein a billet comprises silicon, intermetallic particles, and injected hardened particles with an average grain size less than 15μm , and a volume content of silicon, intermetallic, and injected hardening particles in a range from about 257o to about 60%, the billet is placed in a piston die matrix against a bracket made from a porous ceramic material infiltrated with aluminum alloy, the porosity of the ceramic frame is in a range from about 35% to about 50%, and forging is conducted under super plasticity conditions

28. A piston production method according to claim 26. wherein the same aluminum alloy is used for the ceramic frame and piston case.

29. A piston production method according to claim 1. wherein the piston is subjected to further deformation in a close-end piston die at a strain rate in a range from about 10^"5 to about 10 ^"4 s^"1 for a time penod from about 0.5 mm to about 5 min.

30. A piston production method according to claim 1, the method compπses providing billets comprising silicon, intermetallic particles, and injected hardening particles with an average grain size less than 15μm², and forming a hardened layer a piston surface, conducting hot deformation forging is conducted at a temperature in a range from about 0.9 T_meit to about 0.96 T_meι_t and at strain rate in a range from about 5 x 10^"2 to about 10^"3 s^"1.