JPH0642402A - FCD piston for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an FCD piston for an internal combustion engine in which cracks hardly occur, that is, higher strength. [Composition] 1% to 5% of silicon Si and 0.1% to 3
% Molybdenum Mo and spheroidal graphite cast iron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FCD piston for an internal combustion engine, and more particularly to a high strength FCD piston for an internal combustion engine.

[0002]

2. Description of the Related Art Recently, as a piston for an internal combustion engine (particularly a diesel engine), a lightweight aluminum piston has been replaced by a heavy weight and a low thermal conductivity, but a high workability, a high strength, and a low heat resistance. Expansion coefficient spheroidal graphite cast iron piston (material composition of FCD piston is C: 3.0 to 4.0,
Si: 2.0-3.5, Mn: 0.2-1.0, Cu:
0.1 to 0.5) is in the spotlight.

[0003]

[SUMMARY OF THE INVENTION Incidentally in high pressure test (e.g. 180 kg / cm ² or higher) and reentrant shape trials of the piston-cylinder pressure at higher output of the heavy load Diesel engines, in the conventional FCD piston The thermal conductivity is lower than that of the aluminum piston, and the piston is apt to be oxidized, which causes a disadvantage that a crack is generated locally (in particular, an oxidized portion).

It is an object of the present invention to provide an FCD piston for an internal combustion engine, which focuses on the above inconvenience and which is less likely to cause cracks and has higher strength.

[0005]

In order to achieve the above object, an FCD piston for an internal combustion engine according to the present invention has a 1%
The composition was made of spheroidal graphite cast iron containing ˜5% silicon Si and 0.1% to 3% molybdenum Mo.

[0006]

It has been found that according to the above structure, the promotion of oxidation is suppressed and the occurrence of local cracks is prevented.

[0007]

[Examples] Examples will be described below in place of test results. The test was performed using a conventional FCD piston and various silicon Si.
And spheroidal graphite cast iron F, which is the content ratio with molybdenum Mo
A durability test was performed on an FCD piston made of CD.

In the following description of the latter FCD piston, an FCD piston containing Si (0.5%) and Mo (0.05%), Si (1%) and Mo (0.1%).
%) And an FCD piston containing Si (3%) and M
FCD piston containing O (2%), Si (5
%) And Mo (3%) and FCD pistons containing Si (7%) and Mo (5%).

First, FIG. 1, which is a typical test result, will be described. The figure shows each FCD piston ~ 900 °
By increasing the amount of oxidation on the surface at high temperature of C every 100 hours, the conventional FCD piston increases the amount of oxidation with time as shown by the curve S1.
As shown by the curve S2, the D pistons have a constant amount of oxidation regardless of the change of time. Although not shown, the FCD piston is located between the curves S1 and S2 and rather close to the curve S1.

Next, FIG. 2, which is a typical test result, will be described. In the figure, each of the FCD pistons
Heating and quenching are repeated 50 times between 0 ° C. and room temperature, and the cross-sectional structure shows the state of formation of an oxide layer.
It should be noted that, although the figure is a schematic diagram of the cross-sectional structure, the FCD piston ,,, as shown in (a) of the figure, the other conventional FCD piston (and FCD piston,)
Is as shown in (b) of FIG. In the figure,
A range A is an oxide layer, a range B is a decarburized layer, and a range C is a central portion without change. If the thickness of each oxide layer is shown numerically, FC
The D piston is about 100 μm, while the conventional FCD piston is about 400 μm.

Each of the above FCD pistons was mounted on a 6-cylinder actual engine and subjected to a heavy load test. As a result, conventional FCD pistons (and FCD pistons) were found (more specifically, at the rim portion of the piston combustion chamber). , While a crack with a depth of about 0.2 mm to 0.5 mm occurred, FC
No cracks were found in the D piston.

According to the above test results, at least 1% to
FCD made of spheroidal graphite cast iron containing 5% silicon Si and at least 0.1% to 3% molybdenum Mo.
It has been found that a piston can prevent the development of an oxide film and prevent the occurrence of cracks, that is, can be a high-strength piston.

[0013]

As described above, the FCD piston for an internal combustion engine of the present invention comprises 1% to 5% of silicon Si.
Since it is made of spheroidal graphite cast iron containing 0.1% to 3% of molybdenum Mo, cracks hardly occur, that is, the FCD piston for internal combustion engine has higher strength.

[Brief description of drawings]

FIG. 1 is a graph of a holding heating test result for an FCD piston according to the related art and the present invention.

FIG. 2 is a result chart of the repeated heating test for the FCD piston of the prior art and the present invention, in which (a) is the FCD of the present invention.
Schematic diagram of cross-sectional structure of piston, (b) is a conventional FC
It is a schematic diagram of the cross-section structure of a D piston.

[Explanation of symbols]

 S1 Characteristic curve S2 Characteristic curve A Oxidized layer B Decarburized layer C Central part

Claims (1)

[Claims] 1. 1% to 5% of silicon Si and 0.1%
An FCD piston for an internal combustion engine, characterized in that it is made of spheroidal graphite cast iron containing molybdenum Mo of 3% to 3%.