FR2875816A1 - Extruded rod used in the production of a forged piston in combustion engines is made from an aluminum alloy containing alloying additions of silicon, copper, magnesium, chromium, nickel and titanium - Google Patents

Abstract

Extruded rod is made from an aluminum alloy containing (in wt.%): 10.5-11.8 Si, 3.3-4.0 Cu, 0.4-0.7 Mg, 0.05-0.20 Cr, 0.28-0.42 Ni, 0.03-0.1 Ti, 0-0.05 Zn, 0-0.05 Mn, 0-0.30 Fe and a balance of aluminum. The alloy optionally contains 0.01-0.03 Sr.

Description

2875816 Forged aluminum alloy piston

  Field of the Invention The invention relates to a forged aluminum alloy piston of the Al-Si-Cu type with high fatigue resistance, in particular for use in combustion engines.

  STATE OF THE ART In internal combustion engines, pistons molded aluminum alloy type Al-Si are commonly used. These alloys are resistant to abrasion, thermal and mechanical stresses, and fatigue in a temperature range typically between -20 C and 400 C.

  Patent Application DE 198 29 047 A1 (Aisin Seiki KK) discloses a molded piston alloy of composition Si 13 16 Cu 2 5 Mg 0.2 1.3 Ni 1.0 2.5 V 0.05 0.2 P 0.004 0.02.

  If 11.0 14.0 Cu 5.6 8.0 Mg 0.5 -1.5 Ni 0.05 0.9 Mn 0 -1.0 Ti 0.05 1.2 Zr 0.12 -1.2 Zn 0.05 0.9 Fe 0 0.8 Sr 0.001 0.1.

  For the same application, patent application DE 198 45 279 A1 (Alcan Deutschland GmbH) offers alloys of the Al-Si type with a much higher nickel content of up to 12%.

  US Pat. No. 6,399,020 (United States of America) discloses a cast piston composition alloy. Forged pistons are also known, which generally have better fatigue strength than molded pistons. Patent EP 924 310 BI (Federal Mogul) proposes for this purpose an alloy of composition Si 10.5 13.5 Cu 2.0 4.0 Mg 0.8 1, 5 Ni 0.5 2.0 Co 0.3 0.9 P> 20 ppm Ti 0.05 0.2 or (Zr and / or V 0 0, 2).

  Cobalt leads to the formation of small intermetallic phases, which act favorably on the heat resistance of the alloy.

  UK Patent Application 2,300,198 A (British Aluminum Holdings Ltd) discloses a forged piston alloy of composition Si 10.5 -12.5 Cu 2, 8 4.0 Mg 1.1 -1.8 Ni 1, 0 -1.8 Fe 0.3 1.0 Mn 0 0.5 B, V, Zn, Cr, Ti 0 0.2 each and <0.5 in total.

  EP 790 325 B1 (Corus) discloses spun products of composition Si 11.0 -13.5 Cu 0 0.35 Mg 0.5 2.0 Mn 0 1.2 Ni, Zr, Cr, Zn 0 0, 1 each Fe, Bi, Pb, Sn 0 1.0 each Sr 0.02 0.1.

  This patent proposes the use of this alloy for the manufacture of spun components for hydraulic and pneumatic systems, at temperatures not exceeding 150 C.

Description of figures

  Figure 1 shows the fatigue strength of alloys A (symbol: black filled diamond) and B (symbol: square not filled), measured on cylindrical test pieces during a fatigue test in axial stress with R = 0,1 .

Description of the invention

  (a) Definitions Unless otherwise stated, all information relating to the chemical composition of alloys is expressed in percent by mass. Therefore, in a mathematical expression, 0.4 Zn means: 0.4 times the zinc content, expressed in percent by weight; this applies mutatis mutandis to other chemical elements. The designation of the alloys follows the rules of The Aluminum Association, known to those skilled in the art. The metallurgical states are defined in the European standard EN 515. The chemical composition of standardized aluminum alloys is defined for example in the standard EN 573-3. Unless otherwise stated, the static mechanical characteristics, ie the breaking strength Rm, the yield strength RP0,2, and the elongation at break A, are determined by a tensile test according to the EN standard. 10002-1, the location and direction of sample collection being defined in EN 755-1 and EN 754-1. Fatigue strength is determined by a test according to ASTM E 466. The term spun product includes so-called stretched products, i.e., products that are made by spinning followed by drawing.

  Unless otherwise stated, the definitions of the European standard EN 12258-1 apply.

  b) Detailed description of the invention

  The present invention can be applied to aluminum alloys of the Al-Si type (series 4xxx) containing between 8 and 14% of silicon, and preferably between 10.5 and 13.0% of silicon, between 0.6 and 4 , 0 of copper, between 0.4 and 1.3% of magnesium, and between 0.25 and 1.3% of nickel. The alloy may also contain titanium (0.02 0.05%), strontium (0.01 0.03%), chromium (at most 0.20%), and, as impurities, iron (not more than 0.50%), manganese (not more than 0.10%) and zinc (not more than 0.10%). A composition in which Fe + Mn + Ti does not exceed 0.60% is preferred.

  Copper leads to the structural hardening of the alloy. Magnesium contributes to the hardening of the alloy. Nickel contributes to the stability of the alloy at high temperatures. The titanium and zirconium elements refine the grain.

  In a particularly preferred embodiment, the alloy has the following composition: Si 10.5 11.8 and preferentially 10.6 11.7 Cu 3.3 4.0 Mg 0.4 0.7 and preferably 0.45 0.65 Cr 0.05 0.20 and preferentially 0.10 0.14 Ni 0.28 0.42 Ti 0.03 0.1 and preferably 0.03 0.05 Zn 0 0.05 Sr 0.01 0.03 Mn 0 - 0.05 Fe 0 - 0.50 and preferably 0 0.30 other elements 0.05 each and 0, 15 in total.

  In another advantageous embodiment, the alloy has the following composition: Si 11.0 -12.5 Cu 0.7 -1.3 Mg 0.8 -1.3 Ni 0.8 1.3 Ti 0 - 0, 05 Zr 0 - 0.03 Fe0-0.50 Mn0-0.05 Zn0-0.10 Cr0-0.05 Fe + Mn + Ti0.60 Other elements 0.05 each and 0.15 in total.

  The alloy is typically cast into spinning billets according to known techniques, homogenized, hot-spun into bars, and optionally quenched on a press. Reverse spinning is preferred which leads to a more even microstructure along the bar. Spun bars are cut into forging blanks of appropriate size. The forging is typically at a temperature between 400 and 480 C. It is followed by quenching. Forged parts are put in solution, typically at a temperature between 460 and 530 C, and quenched. Then they undergo an income treatment.

  The forged piston according to the invention is particularly suitable for use in a racing car engine, which must have the highest possible performance for a very short time of use, of the order of tens of hours, see even a few hours only. By way of example, the piston according to the invention can be used in an engine for a Formula 1 racing car. The concept of Formula 1 refers to a particular competition regulation, and involves the use of racing cars. specifically adapted to this competition. More particularly, a Formula 1 racing car engine is typically subjected to maximum stress during the competition period (of the order of a few hours), and then subjected to an intensive technical inspection, during which it can be replaced worn parts. The longevity of the piston is not a particularly important criterion in this context, unlike passenger vehicles intended for use on the public road network. On the other hand, fatigue resistance is an important criterion for these applications. The piston according to the invention can have a fatigue strength greater than 106 cycles (R = 0.1) for a stress of 300 MPa; a piston with the composition according to claim 4 even holds more than 106 cycles (R = 0.1) for a stress of 350 MPa.

  The forged piston according to the invention can also be used in other racing vehicles, especially in cars, motorcycles or racing ships. The piston according to the invention can also be used in vehicles intended for the general public as well as in commercial vehicles. It can also be used in hydraulic or pneumatic installations, especially at elevated temperatures.

  In the examples which follow, advantageous embodiments of the invention are illustrated by way of illustration. These examples are not limiting in nature.

Examples:

  Two cylindrical bars were spin-spinned from two alloys A and B, the approximate chemical composition of which is shown in Table 1.

Table 1

  If Cu Mg Cr Ni Ti Sr A 11.2 3.65 0.55 0.12 0.35 0.04 0.02 B 11.8 1.0 1, 0 1.0 Their mechanical properties in the sense L (meaning long) are collated in Table 2. Ag is the extended elongation, and n is the hardening coefficient. Table 2 Room temperature 150 C Rpo. 2 Rm Ag A n Rpo.2 R.A [%] [MPa] [MPa] [%] [%] (2-20%) [MPa] [MPa] A 355 443 7.49 0.074 318 362 11, The fatigue strength was also determined by an axial stress test with R = 0.1 at room temperature on smooth surface cylindrical samples. The results are given in Table 3 and Figure 1.

Table 3

  Alloy Stress [MPa] Number of cycles A 300 10 803 100 (*) A 300 12 495 400 (*) A 360 2 784 400 A 420 26 900 A 400 29 500 A 380 61500 A 370 1 135 200 A 360 130 900 ( **) A 350 2 041 500 A 350 4 117 800 A 360 2 174 400 A 370 2 444 300 A 360 1 956 000 A 350 6 337 700 A 340 6 670 000 A 380 746 800 A 330 10768000 A 400 165 700 B 340 77 600 B 340 122 700 B 300 13 055 100 (*) B 320 142 600 B 320 87 100 B 300 1 146 100 B 300 10 803 100 (*) test piece not broken (**) initiation of failure on surface defect For sample A, micrographs after anodic etching show a fairly fine grain recrystallization (diameter about 50 m to 100 m).

  From these bars, cylindrical pistons were forged. They are finished by machining.

Claims (7)

  1. Forged alloy aluminum alloy piston Si 8.0 -14.0% Cu 0, 6 4.0 Mg 0.4 -1.3 Ni 0.25 -1.3 Cr 0 0.20 Fe 0 0.50 Mn0 0.10 Zn0 0, 10 other elements 0.05 each and 0.015 in total, the remaining aluminum, said alloy possibly containing: Ti 0.02 0.05 Sr 0.01 0.03 Forged piston according to claim 1, characterized in that Si 10.5 - 11.8 Cu 3.3 4.0 Mg 0.4 0.7 Ni 0.28 0.42 Cr 0.05 0.20 Fe 0 0.30 Mn0 0.05 Zn0-0.05 Ti0.03 0.1.   3. Forged piston according to claim 2, characterized in that Si 10.6 11.7 Mg 0.45 0.65 Cr 0.10 0.14 Ti 0.03 0.05.   Forged piston according to claim 1, characterized in that Si 11.0 12.5 Cu 0.7 -1.3 Mg 0.8 -1.3 Ni 0.8 1.3 Zr <0.03 Cr < 0.05 Mn 0 0.05 Fe + Mn + Ti <0.60.   Forged piston according to any one of claims 1 to 4, characterized in that it has been manufactured by forging a spun bar.   6. forged piston according to claim 5, characterized in that it was forged at a temperature between 400 C and 480 C, and then treated with a sequence of steps comprising the quench after forging, the dissolution in a temperature solution between 460 C and 530 C, quenching after dissolution, and the income.   7. Use of a piston according to any one of claims 1 to 6 in a Formula 1 racing car engine.