ALUMINUM ALLOY PISTON MATERIALS
Chemical composition%
| NO. |
Cu |
Mg |
Ni |
Si |
Ti |
Fe |
Zn |
Mn |
| JIS AC8A LM13, A132 |
0.8-1.3 |
0.8-1.5 |
1.0-1.5 |
11.0-13.0 |
<0.2 |
<0.8 |
<0.5 |
<0.5 |
| JIS AC8B LM26, F132 |
2.0-4.0 |
0.5-1.5 |
0.5-1.0 |
8.5-10.5 |
<0.2 |
<0.8 |
<0.5 |
<0.5 |
| TS-20(TWL) |
0.5-2.5 |
0.5-1.5 |
0.5-1.5 |
19.0-22.0 |
<0.5 |
<0.8 |
<0.5 |
<0.5 |
| JIS AS-23 LM29 |
0.5-2.5 |
0.5-2.5 |
0.5-1.5 |
22.0-24.0 |
<0.5 |
<0.8 |
<0.5 |
<0.5 |
| JIS AC9A |
0.5-2.5 |
0.5-1.5 |
0.5-1.5 |
22.0-24.0 |
<0.2 |
<0.8 |
<0.2 |
<0.5 |
| JIS AC9B |
0.5-2.5 |
0.5-1.5 |
0.5-1.5 |
22.0-24.0 |
<0.2 |
<0.8 |
<0.2 |
<0.5 |
| AC9C |
0-2.5 |
0.5-1.5 |
0.5-1.5 |
18.0-20.0 |
<0.2 |
<0.8 |
<0.2 |
<0.5 |
Mechanical Properties
| NO. |
(Heat-treatment) |
(Tensilestrength)
(kg/mm2) |
(Hardness) |
(Elongation)
% |
(Thermal Expansion) |
(Specificgravity)
g/cm3 |
| 20o-100oC |
20o-200oC |
20o-300oC |
| AC8A |
T6
T7 |
>28
>25 |
64-74
55-65 |
>0.5
>0.6 |
19.2 x 10-6 |
20.6 x 10-6 |
21.9 x 10-6 |
2.73 |
| AC8B |
T5
T6
T7 |
>23
>28
>25 |
57-69
64-74
54-66 |
>0.5
>0.5
>0.6 |
20.2 x 10-6 |
21.6 x 10-6 |
23.1 x 10-6 |
2.75 |
| TS-20 |
T5
T6
T7 |
>20
>22
>21 |
57-69
64-74
55-65 |
>0.3
>0.3
>0.3 |
7.2 x 10-6 |
18.6 x 10-6 |
20.1 x 10-6 |
2.70 |
| AS23 |
T6
T7 |
>18
>18 |
63-75
54-66 |
>0.3
>0.3 |
16.5 x 10-6 |
16.5 x 10-6 |
18.0 x 10-6 |
2.68 |
Heat Treatment
| Type |
Annealing |
Hour |
Quenching |
Re-annealing Hour |
| T5 |
|
|
|
170o-200oC
10HR |
| T6 |
475o-510oC |
8HR |
475o-510oC |
175o-205oC
10-12HR |
| T7 |
470o-510oC |
8HR |
470o-510oC |
210o-240oC
10-16HR |
Chemical composition limits of piston pin %
| No. |
C |
Si |
Mn |
P |
S |
Mo |
Cr |
| SCM-415H |
0.13-0.18 |
0.15-0.35 |
0.60-0.85 |
<0.030 |
<0.030 |
0.15-0.35 |
0.90-1.20 |
Chemical composition limits of Ni-Resist (Ai-fin) %
Hardness: HB 130-200
HRB: 73-93
| No. |
T.C |
Si |
Mn |
Ni |
Cu |
Cr |
Fe |
| Ni-Resist |
<3.0 |
1.0-2.8 |
0.5-1.5 |
13.5-17.5 |
5.5-7.5 |
1.5-2.5 |
Ba1 |
Chemical composition limits of CYL. LINER %
| No. |
C |
Si |
S |
P |
Mn |
Ni |
Cr |
Cu |
| Centrifugal Cast
Zrayiron |
3.25-3.65 |
2.20-2.60 |
<0.10 |
<0.20 |
0.45-0.65 |
0.05-0.20 |
0.20-0.40 |
0.45-0.75 |
ILLUSTRATION OF SOME IMPORTANT PISTON DESIGNS
 |
1.Auto-Thermic pistons have cast-in steel struts
between the skirt and pin bosses. When the piston
heats up, these struts have the effect of limiting the
expansion of the piston in the direction of the thrust
axis. Transverse slots at the same time prevent
passing of heat. Potential weakness and less
combustion press endurance is the obvious defect
for this type of pistons. |
 |
2.This kind of piston also has cast-in steel struts, but
without transverse slots in the ring groove. It
combines extremely smooth running with a high
degree of strength for high-output engines. |
 |
3.The top and sometimes lower compression ring
grooves are machined into Ni Resist Bonded insert.
This insert counteracts the high degree of wear
occurring in the top groove, This type is applied to
Diesel engines, particularly those with turbocharging. |
 |
4.Special head shape (combustion chamber)
especially for diesel engines. |
 |
5.Pistons with cooling channel are used whenever
high operating temperature occurs. This intensive
oil cooling counteracts the high temperatures in the
piston crown and ring belt. |
A DESCRIPTION OF FOUR TYPICAL PISTON TYPES
1.PLAIN, SOLID SKIRT, OPEN-ENDED
This type is very strong but heavier and has its skirt connected to its
head region all the way round.
It is necessary to allow more clearance,
especially at the top of skirt to avoid seizure.
2.TRANSVERSE SLOT,
OPEN-ENDED
Such a piston is thermally compensating and can usually be operated at smaller clearances at the top
of the skirt in the interests of noise
reduction.
3.SOLID SKIRT SLIPPER
This type of piston has no thermal slot but the skirt is heavily cut away
in the pin axis to reduce
weight and avoid swaying. It is also more rigid and
usually needs greater clearance than other types,
but is the strongest one.
4.TRANSVERSE
SLOT SLIPPER
Contrary to solid skirt slipper type, this type has a cast or milled
transverse slot in the oil ring
groove for thermal compensation.
Smaller clearance at the top of the skirt is requried , in the interest of
quiet operation.
IMPORTANT PISTON TERMS
|
|
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N.
+.
-. |
Cylinder Bore Dia. (Std. Size)
Piston Pin Dia.
Compression Height
Ring Land
Ring Groove Dia. (Comp. Ring)
Bottom Ring Groove Dia.
Piston Pin Length
Upper Oil Ring Groove Dia.
Circlip Width
Upper Oil Ring Width
Oil Hole Dia.
Piston Length
Distance between the Bossen
Comp. Ring Width
Height of Dome
Depth of Dish |
|
