Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
  • C22C21/04—Modified aluminium-silicon alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings

Definitions

• the invention relates to aluminum alloys that can be cast into high-quality aluminum cylinder blocks, utilizing a low-cost low pressure sand casting process, for automotive engines having good mechanical properties and wear and scuffing resistance; so that according to the present invention the engine blocks can be manufactured without the need for insertion of iron (or costly aluminum) liners in order to have effective cylinder walls.
• Background of the Invention Most of the automotive and aviation cylinder engine blocks made out of aluminum alloys are currently manufactured by casting the block body in silica sand molds using sand cores and inserting a set of cast iron liners to form the cylinder-piston contact surfaces.
• US Patent 4,068,645 issued January 17, 1978 to David Charles Jenkinson teaches that the microstructure of a hypereutectic Al-Si alloy can be modified with strontium and/or sodium for obtaining Brinell hardness in the range of 70 - 150 by including magnesium up to about 4 wt.%.
• This patent teaches that the desired microstructure must avoid the formation of primary aluminum or primary silicon phases and that there must be a high-volume fraction of finely dispersed eutectic silicon which provides the wear resistance to the cast article.
• the desired micro structures are provided by careful selection and combination of four parameters: (a) silicon content, (b) modifier content, (c) growth rate during solidification and (d) temperature gradient at the solid/liquid interphase during solidification.
• Ni, Fe and Mn are interchangeable with each other, being the ranges as follows: Fe + Mn between 0.2 and 1.5%; Fe + Ni between 1.1 and 3.0%; and Fe + Ni + Mn between 1.2 and 4.0%.
• Titanium is added to improve castability and the mechanical properties of this alloy.
• This alloy however has a high cost due to the high content of Ni 3 in contrast with the alloy of the present invention having less than about 0.4 — 0.8%Ni.
• the lower concentration Ni thus particularly makes the alloy of the present invention more competitive.
• US patent 4,648,918 issued March 10, 1987 to Kasuhiko Asano, et al. teaches an abrasion-resistance aluminum alloy having a composition comprising: 7.5 - 15% Si; 3.0 - 6.0% Cu 3 0.3 - 1.0% Mg, 0.25 - 1.0% Fe; 0.25 - 1.0% Mn; and a balance of Al and other components.
• the alloy of this patent is directed to improve the extrudability, forgeability and mechanical properties of ingots.
• the Cu content is higher than the alloy of the present invention and the heat treatment and final processing of this alloy are far different from the sand-casting process of the present invention.
• US patent 5,019,178 issued May 28, 1991 to John Barlow et al. discloses a production method of an aluminum-silicon liner produced from a melt consisting essentially of 14 - 16% Si; 1.9 - 2.2% Cu; 1.0 - 1.4 Ni; 0.4 - 0.55 Mg; 0.6 - 1.0% Fe; 0.02 - 0.1% Sr; and 0.3 -0.6 Mn.
• the alloy of this patent is formed into cylinder liners under pressure during the solidification stage of the casting process. This patent does not teach or suggest that the whole engine block be made of the claimed alloy in a low-pressure sand-casting process.
• US patent 5,217,546 issued June 8, 1993 to John A. Eady, et al. discloses a cast hypereutectic Al-Si alloy having 12 - 15% Si; more than 0.10% Sr; more than 0.005% Ti; 1.5 - 5.5% Cu; 1.00 - 3.00 Ni; 0.1 - 1.0 Mg; 0.1 - 1.0% Fe; and other components.
• the microstructure obtained is such that any primary Si formed is substantially uniformly dispersed and is substantially free of segregation, with the microstructure predominantly comprising an eutectic matrix.
• the alloy of this patent however relies on Ti and an excessive amount of Ni, which makes it tqo expensive an alloy for competitive mass production of engine blocks.
• US patent 5,484,492 issued January 16, 1996 to Kevin P. Rogers et al. discloses a hypereutectic Al-Si alloy essentially having at least one element selected from a first group of elements consisting of 0.005% up to 0.25% of Cr, Mo, Nb, Ta, Ti, Zr, V and Al; at least one element selected from a second group of elements consisting of 0.1 to 3.0 % Ca, Co, Cr, Cs, Fe, K, Li, Mn, Na, Rb, Sr, Y, Ce, elements of the Lanthanide series and elements of the Actinide series; and a third group of elements consisting of: 12 - 15% Si; 1.5 - 5.5 Cu; 1.0 — 3.0% Ni; 0.1 - 1.0% Mg; 0.1 - 1.0% Fe; 0.1 - 0.8% Mn; 0.01 - 0.1 Zr; 0 - 3.0% Zn; 0 - 0.2% Sn; 0 - 0.2% Pb; 0 - 0.1% Cr; 0.00
• US patent 6,399,020 issued June 4, 2002 to Jonathan A. Lee et al. discloses an aluminum alloy suitable for high-temperature applications, such as pistons and other internal combustion engines applications, having the following composition: 11.0 — 14.0% Si; 5.6 — 8.0% Cu; 0 - 0.08 Fe; 0.5 - 1.5 Mg; 0.05 - 0.9Ni; 0 - 1.0 Mn; 0.05 - 1.2 Ti; 0.12 - 1.2 Zr; 0.05 - 1.2 V; 0.05 - 0.9 Zn; 0.01 - 0.1 Sr; with the balance Al.
• the ratio of Si/Mg is 10 — 25
• the ratio of Cu/Mg is 4 - 15.
• the alloy of the applicants' invention differs from the alloy composition disclosed in this patent, mainly in the Si/Mg ratio and in the amount of Sr. Since Sr is an expensive element, the alloy of the present invention is more cost-competitive. In addition, the present invention does not include Zr or V and has a maximum of 0.3% Mg.
• US patent 6,592,687 issued July 15. 2003 and US patent 6,918,970 issued July 19, 2005, both to Jonathan A. Lee et al. disclose an aluminum-silicon alloy having the following composition in weight percent: 14 - 25.0 Si; 5.5 - 8.0 Cu; 0.05 - 1.2 Fe; 0.5 - 1.5 Ni; 0.05 - 0.9 Mn; 0.05 - 1.2 Ti; 0.05 1.2 Zr; 0.05 - 1.2 V; 0.05 - 0.9 Zn; 0.001 - 0.1 P; and with the balance being Aluminum.
• the '970 patent's alloy has an extended range of Si (6.0 - 25.0%) plus Sr (with a range of 0.001-0.1).
• the Si/Mg ratio is 10 - 25 and the Cu/Mg ratio is 4 - 15.
• This alloy has as key elements Ti, V and Zr that modify the lattice parameters of the aluminum matrix by forming compounds of the type AI 3 X having LI 2 crystal structures, wherein X stands for Ti, V or Zr.
• the alloy comprises by weight, 9.5 - 12.5 % Si; 0.1 - 1.5 % Fe; 1.5 - 4.5% Cu; 0.2 - 3% Mn; 0.1 - 0.6% Mg; 2.0% maximum Zn; 0 - 1.5% Ni; 0.25% maximum Ti; up to 0.05% Sr; with the balance being aluminum.
• An important feature of this Patentee's invention is the proportion of Mn to Fe.
• the weight ratio Mn/Fe is between 1.2 to 1.75 or high ⁇ r when the Fe content is equal to or greater than 0.4% and the weight ratio Mn/Fe is at least 0.6 to 1.2 when the Fe content is less than 0.4% of the alloy.
• the Si range of the present invention is 13-14%.
• the desired microstructures in the Al-Si alloys are produced by a right combination of growth rate during solidification and temperature gradient.
• the proposed invention herein described and claimed is an aluminum-silicon alloy composition which, when cast, meets the manufacturing and performance conditions required for cylinder engine blocks and further can be cast using low-cost casting processes such as silica-sand molds.
• the alloy of the present invention comprises (in weight percent):
• Figure 1 shows a microphotograph of the microstructure (100 ⁇ m) obtained from an unlined aluminum cylinder surface of an engine block cast from the alloy of the present invention.
• Figure 2 shows a contrasting microphotograph of the microstructure (100 ⁇ m) obtained from an unlined aluminum cylinder surface of an engine block cast from the alloy known as A390.
• Figure 3 is a schematic phase diagram of Al-Si alloys showing the preferred range of Si content for the alloy of the invention as contrasted to prior art alloys known as A380, A390,
• the aluminum alloy blocks to be manufactured demand strictly controlled characteristics and mechanical properties in order to perform as expected in modern vehicles.
• Blocks without liner inserts must have high wear resistance in the running surfaces and withstand high pressures on the order of 100 to 200 bar in those engines having high peak firing pressures.
• the porosity level must be below 1 % and the maximum pore size must be below 500 microns in the running surfaces.
• the aluminum alloy has a high thermal conductivity in order to sustain high heat transfer rates from the hot areas of the engine to the cooling liquid of the engine cooling system, as well as having good corrosion resistance to the cooling media.
• the high-efficiency modern engines also demand that the alloys from which the engine blocks are cast show high strength and high resistance to fatigue and creep at elevated temperatures, in the range of 180°-200°C.
• machining high-silicon alloys means greater wear of tools and high machining cost, as in the case of the A390 alloy.
• primary silicon formation is suppressed resulting in a fully eutectic microstructure despite its high silicon content. This characteristic of the microstructure of the castings of the invention assures good machinability. Tool life is comparable to machining an A356 alloy but with superior surface finish.
• the alloy of the present invention is based on the Al-Si-Cu-Mg-Ni-Mn-Fe system to enhance maximum wear resistance. It provides the required characteristics demanded by modern engine-blocks having unlined cylinders, while also maintaining a competitive low manufacturing cost.
• the casting process of the invention utilizes a thermal core (or massive chill) in combination with silica-sand cores and molds.
• the chill provides the right direction of the solidification process as well as the necessary solidification rate which results in high fatigue properties of the castings.
• the alloy of the present invention is particularly suited for the production of linerless aluminum alloy blocks at a lower cost than the currently used alloys.
• Table 1 compares the typical concentration of the elements of the prior-art alloys with the composition of the present invention.
• Alloy 390 (A) is the historical choice for wear-resistance cast motor elements, but as discussed above it is not applicable for sand casting processes. Alloy 3HA (B) is also an alloy of choice for those applications, but its cost is high because of its high content of nickel (2%). The high concentration of Ni increases the alloy cost by 35% ($15,000 US/Ton of Ni) 5 and the 2000 ppm of Sr further combines to make it even more expensive. Near eutectic alloys (C) do not have sufficient silicon content to provide the required wear resistance.
• the alloy of the present invention provides sufficient Si content for achieving the desired wear resistance in the casting surfaces and the other components of the alloy make it suitable for its casting in silica sand molds having relatively lower heat dissipation properties than molds of other casting processes. At the same time, the alloy of the present invention is less expensive than other prior art alloys having similar wear resistance particularly because of its lower Ni content.
• the alloy of the present invention provides a cost competitive process for massive engine blocks casting without the need of cylinder liners, particularly when cast in silica sand molds and cores.
• the wear resistance provided by the alloy avoids the necessity of inserting iron liners in the cylinder bores. Consequently, the manufactured blocks are smaller and lighter, (saving the weight and cost of iron liners) and can increase the engine capacity without increasing engine size (for example from 2.3 to 3.0 liters).
• the alloy of the invention has better thermal characteristics regarding heat dissipation
• the alloy also allows for tighter clearances because the thermal expansion coefficients of both pistons and the blocks are similar (in contrast with the greater differentiation of thermal expansion coefficients between the piston aluminum alloy and the iron liners). This advantage provides a quieter engine operation and makes the engines environmentally cleaner.
• the linerless engines made from the alloy of the present invention are also easier to recycle, since no separation of iron cylinder liners from aluminum is required.
• the alloy of the invention further provides very good machining characteristics, and although the tool life is comparable and similar to machining of the currently-known A356 .alloy, the surface finish in the cylinder bores is significantly better.
• the manufacturing cost of unlined engine blocks is reduced by about 40% by using the alloy and method of the invention as compared with the manufacturing cost when using the known alloys of the prior art.
• Example 1 An Al-Si alloy was prepared according to the present invention and a block was cast in silica sand molds and cores. The alloy had the following composition (in weight percent):
• the alloy was poured into the mold at a temperature of 750 0 C. The results were as follows: The microstructural segregation was reduced.
• test set-up provides a reciprocating line contact between a dowel and a plate.
• the hardened dowel is used to simulate the piston ring while a flat ground plate is used to simulate the cylinder liner.
• the oil used was a commercially available automotive petrol engine mineral oil heated to 100 C°.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (3)

Family

ID=39029354

Family Applications (1)

Country Status (9)

Cited By (1)

Families Citing this family (18)

Family Cites Families (19)

• 2006
  • 2006-08-04 US US11/499,165 patent/US20080031768A1/en not_active Abandoned
• 2007
  • 2007-08-03 BR BRPI0714884-4A patent/BRPI0714884A2/pt not_active IP Right Cessation
  • 2007-08-03 CN CN200780037074A patent/CN101627138A/zh active Pending
  • 2007-08-03 CA CA002660137A patent/CA2660137A1/en not_active Abandoned
  • 2007-08-03 WO PCT/IB2007/004235 patent/WO2008053363A2/en active Application Filing
  • 2007-08-03 KR KR1020097004541A patent/KR20090048492A/ko not_active Application Discontinuation
  • 2007-08-03 MX MX2009001319A patent/MX2009001319A/es unknown
  • 2007-08-03 AU AU2007315791A patent/AU2007315791A1/en not_active Abandoned
  • 2007-08-03 EP EP07866603A patent/EP2054535A4/en active Pending
• 2010
  • 2010-03-22 US US12/728,975 patent/US20100288461A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events