Piston for internal combustion engines, and use of a piston for internal combustion engines

Abstract

A diesel engine piston is cast in one piece and consists of almost fully pearlitic cast iron with spheroidal graphite as the piston material. Such a piston is used for “light vehicle” diesel engines, “heavy duty” diesel engines and “large bore” diesel engines.

Claims

1. A piston for internal combustion engines, comprising: a one piece casting consisting of almost fully pearlitic cast iron with spheroidal graphite as the piston material; the piston material comprising the following elements in wt. %: C: 3.23 to 3.81; Si: 2.2 to 3.23; Mn: 0.04 to 0.4; Mg: 0.0025 to 0.054; P: 0.005 to 0.1; S: 0.003 to 0.020; Cr: 0.01 to 0.1; Ni: 0.006 to 0.1; Mo: 0.002 to 0.05; Nb: <0.1; Cu: 0.3 to 2.0; Pb: <0.007; B: <0.01; W: 0.001 to 0.1; Ti: <0.015; Sn: 0.05 to 0.135; V: 0.002 to 0.3; Sb: 0.001 to 0.07; and as the remainder Fe and unavoidable impurities; the piston material including a matrix of pearlite; the piston material including graphite phases with a primarily spherical morphology; the piston material including a ferrite content of ≤2.6%; and if the ferrite is present, the piston material including regions of the ferrite around the graphite phases.

2. The piston according to claim 1, wherein the ferrite content is <1.0%.

3. The piston according to claim 1, wherein the ferrite content is <0.5%.

4. The piston according to claim 1, wherein the piston material consists of the elements in wt %.

5. The piston according to claim 1, wherein the one piece casting includes a cooling channel.

6. An internal combustion engine comprising the piston according to claim 1.

Description

DETAILED DESCRIPTION

(1) A specific example of a piston material as according to the present invention is a substantially fully pearlitic cast iron with spheroidal graphite, which consists of the following elements in wt. %: C: 3.7; Si: 2.6; Mn; 0.3; Mg: 0.03; P: 0.02; S: 0.01; Cr: 0.05; Ni: 0.03; Mo: 0.01; Nb: 0.01; Cu: 0.6; Pb: 0.001; B: 0.0001; W: 0.001; Ti: 0.01; Sn: 0.06; V: 0.1, and as the remainder Fe and unavoidable impurities.

(2) As a further example of the present invention an automobile diesel engine piston was cast by way of a gravity sand casting process and the following chemical composition was determined in wt. %: C: 3.38%; Si: 3.05%; Mn: 0.160%; P: 0.065%; S: 0.007%; Cr: 0.025%; V: 0.006%; Mo: 0.005%; Ni: 0.015%; Cu: 0.737%; Mg: 0.054%; Ti: 0.0084%; W: 0.0050%; Sn: 0.0980%; Nb: 0.0048%; Al: 0.0219%; Ca: 0.0013%; Pb: 0.0006%; N: 0.0077%; Co: 0.0065%; As: 0.0057%; Bi: 0.0018%; Ce: 0.0164%; Sb: 0.0007%; Te: 0.0010%; La: 0.0032%; Zn: 0.0004%.

(3) Cross sections of this piston were produced and samples were taken at different points in the piston, which were tested with respect to the mechanical properties thereof and for which structural analyses were also carried out. On the basis of eleven samples taken, an average hardness HB 187.5/2.5 of 300 was determined. Overall, the piston had good homogeneity in terms of this hardness value, i.e. there were no significant fluctuations in hardness across the cross section of the piston. The samples taken at the corresponding points of the piston cross section were prepared metallographically and tested microscopically with respect to the different phases, and a substantially uniform distribution of spheroidal graphite in a pearlite matrix as well as only very small contents of ferrite in the microstructure were determined.

(4) Tables 1 and 2 below list a series of compositions (Samples 1 to 11) of casting alloys which represent the material of the piston according to the invention and which were determined in correspondingly produced pistons.

(5) TABLE-US-00001 TABLE 1 Sample 1 2 3 4 5 Component in wt. % C 3.691 3.673 3.663 3.669 3.65 Si 3.09839 3.02632 2.99495 2.96243 3.220427 Mn 0.0408 0.0401 0.03963 0.03998 0.062328 P 0.03832 0.03883 0.03841 0.03876 0.076619 S 0.0129 0.0101 0.0104 0.0115 0.0075 Cr 0.01349 0.01305 0.0126 0.01246 0.026776 V 0.00747 0.00722 0.00732 0.00733 0.007335 Mo 0.00301 0.00278 0.00277 0.00275 0.003535 Ni 0.01242 0.01215 0.012 0.01202 0.015239 Cu 0.72771 0.73109 0.42569 0.42531 0.417631 Mg 0.03901 0.0359 0.03442 0.03121 0.038429 Ti 0.00746 0.00724 0.00724 0.00714 0.007456 W 0.00126 0.00093 0.00102 0.00095 0.0002 Sn 0.0566 0.0516 0.07648 0.07774 0.099729 Nb 0.00089 0.00081 0.0009 0.00087 0.000946 Al 0.01489 0.01464 0.01393 0.01296 0.017827 Ca 0.00093 0.00083 0.00092 0.00075 0.000313 Pb 0.00045 0.00049 0.00054 0.00054 0.000906 N 0.00315 0.00349 0.00334 0.00347 0.005176 Co 0.00656 0.0066 0.00664 0.00667 0.007799 As 0.0034 0.00348 0.00373 0.00393 0.005986 Bi 0.00072 0.00079 0.00089 0.00086 0.000739 Ce 0.01353 0.01343 0.01357 0.01235 0.012057 Sb 0.0004 0.0004 0.0004 0.0004 0.000479 Te 0.0008 0.0008 0.0008 0.0008 0.0008 La 0.00282 0.00281 0.00274 0.00253 0.001638 Zn 0.00015 0.00014 0.00013 0.00014 0.000175 Fe Remainder + Remainder + Remainder + Remainder + Remainder + impurities impurities impurities impurities impurities

(6) TABLE-US-00002 TABLE 2 Sample 6 7 8 9 10 11 Component in wt. % C 3.26 3.23 3.68 3.36 3.38 3.36 Si 2.737827 2.736052 3.230111 2.85172 3.047143 2.960463 Mn 0.317789 0.314292 0.057017 0.171237 0.159732 0.159244 P 0.074836 0.074415 0.075642 0.069684 0.064893 0.064661 S 0.014 0.014 0.009 0.01 0.0068 0.0096 Cr 0.059092 0.060118 0.020318 0.023744 0.025457 0.025186 V 0.007076 0.007158 0.00828 0.007839 0.006491 0.006295 Mo 0.006718 0.006809 0.002762 0.006728 0.005099 0.004876 Ni 0.025739 0.025695 0.013558 0.018661 0.015426 0.015051 Cu 0.75797 0.75999 0.432448 0.787839 0.736804 0.746286 Mg 0.042563 0.045771 0.043171 0.033834 0.053795 0.047091 Ti 0.007716 0.007585 0.007532 0.007826 0.008394 0.008458 W 0.002548 0.002477 0.001271 0.005461 0.005027 0.004383 Sn 0.133554 0.134397 0.087247 0.120429 0.097966 0.099455 Nb 0.012062 0.01717 0.000675 0.00608 0.0047966 0.004713 Al 0.014324 0.014725 0.016096 0.019275 0.021852 0.020247 Ca 0.00402 0.000371 0.000799 0.000625 0.001292 0.00112 Pb 0.000231 0.000255 0.00057 0.000663 0.000595 0.000603 N 0.003582 0.002003 0.00413 0.007155 0.007662 0.007529 Co 0.007931 0.008036 0.007317 0.007493 0.006549 0.006485 As 0.004618 0.004283 0.005674 0.006559 0.005716 0.005799 Bi 0.00099 0.000904 0.001046 0.001431 0.001707 0.001746 Ce 0.010462 0.01077 0.012976 0.012453 0.016401 0.015374 Sb 0.001776 0.001577 0.000923 0.001032 0.000683 0.001233 Te 0.000996 0.0008 0.001329 0.001067 0.001032 0.00123 La 0.001724 0.001722 0.002855 0.002314 0.003197 0.003048 Zn 0.000147 0.000121 0.000404 0.000296 0.000386 0.000372 Fe Remainder + Remainder + Remainder + Remainder + Remainder + Remainder + impurities impurities impurities impurities impurities impurities