JPH0649585A - Cast iron for cylinder liner - Google Patents

Abstract

PURPOSE:To obtain cast iron for a cylinder liner excellent in corrosion and wear resistance and high temp. wear resistance by specifying the compsn. constituted of C, Si, Mn, P, Cr, Cu, B and Fe. CONSTITUTION:The cast iron for a cylinder liner is constituted of, by weight, 3.1 to 3.5% C, 2.0 to 2.6% Si, 0.5 to 1.0% Mn, 0.1 to 0.4% P, 0.15 to 0.5% Cr, 0.5 to 1.5% Cu and 0.02 to 0.06% B, and the balance substantially Fe and is excellent in corrosion and wear resistance and high temp. wear resistance. In a cylinder obtd. by melting the same cast iron and executing metal mold centrifugal casting, the corrosive wear loss and high temp. dry wear loss are both reduced to about <=1/2 as compared with those in the conventional one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast iron for a cylinder liner which is excellent in corrosion resistance and high temperature resistance.

[0002]

2. Description of the Related Art A thin-walled cylinder liner used on the inner peripheral surface of a cylinder of an internal combustion engine must slide on a piston ring and maintain airtightness. Baking property is required. Conventionally, for this purpose, as a cylinder liner material, special cast iron having A-type graphite in its structure and containing Cr, B, P, etc. as wear resistance improving elements has been used. In addition, in the liner casting, conventionally, sand mold casting and sand mold centrifugal casting, which can reduce the solidification rate, have been applied in order to crystallize A-type graphite. However, Japanese Patent Publication No. 58-36664 discloses the technique. As disclosed, it has also come to be manufactured by die centrifugal casting.

[0003]

However, exhaust gas regulations are planned to be strengthened, maintenance-free and high output are strongly demanded, and conventional liner materials have problems in corrosion wear resistance and high temperature wear resistance. . In particular, when exhaust gas is passed through an EGR (exhaust gas circulation device) as a NOx control measure for a diesel vehicle, sulfuric acid is generated and corrosion wear becomes remarkable.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cast iron for a cylinder liner which is excellent in corrosion wear resistance and high temperature wear resistance.

[0005]

The cast iron for cylinder liner of the present invention has a chemical composition of wt% and C: 3.1 to 3.
5%, Si: 2.0 to 2.6%, Mn: 0.5
~ 1.0%, P: 0.1 ~ 0.4%, C
r: 0.15 to 0.5%, Cu: 0.5 to
1.5%, B: 0.02 to 0.06%, and the balance substantially Fe.

[0006]

The chemical composition of the cast iron for cylinder liner of the present invention is limited for the following reasons. The unit is% by weight. C: 3.1 to 3.5% C is necessary for crystallization of graphite and formation of carbides. If it is less than 3.1%, it becomes difficult to crystallize graphite and the amount of carbides decreases, resulting in wear resistance. , Seizure resistance is reduced. on the other hand,
If it exceeds 3.5%, both mechanical properties and wear resistance decrease.

Si: 2.0 to 2.6% Si is necessary for crystallizing graphite, and if it is less than 2.0%, it becomes difficult to crystallize graphite and the seizure resistance decreases. On the other hand, if it exceeds 2.6%, ferrite is likely to be deposited and mechanical abrasion resistance and seizure resistance are deteriorated. Mn: 0.5 to 1.0% Mn is added to improve the hardness, and if it is less than 0.5%, its effect cannot be expected, while if it exceeds 1.0%, the hardness becomes too high and the workability is descend.

P: 0.1 to 0.4% P is necessary for forming a phosphorus eutectic (stedite), and if it is less than 0.1%, the eutectic amount is too small and the hardness improving effect is little. If it exceeds 0.4%, the eutectic amount becomes excessive and it becomes brittle. Cr: 0.15 to 0.5% Cr forms chromium carbide and is added to improve hardness and wear resistance. If it is less than 0.15%, it has little effect, while 0.5%. If it exceeds, the amount of carbide becomes excessive and the workability deteriorates.

Cu: 0.5 to 1.5% Cu is added to improve matrix strength and corrosion resistance by densifying pearlite, and if it is less than 0.5%, it has almost no effect, while 1.5% is added. If it exceeds, the base hardness becomes too high and the corrosion resistance effect is saturated. B: 0.02 to 0.06% B acts to promote the precipitation of carbide and is 0.02
If it is less than 0.1%, the effect cannot be expected. On the other hand, if it exceeds 0.06%, the precipitation of carbide becomes excessive and the hardness becomes too high.

In addition to the above alloy components, the balance of the cast iron of the present invention is substantially Fe. Since S makes the material brittle, it is desirable that the content be small, and it is preferable to keep S: 0.1% or less.

[0011]

EXAMPLE A cast iron having the chemical composition shown in Table 1 below was melted,
Centrifugal die casting at a casting temperature of 1400 ° C and a die rotation speed of 1800 rpm, outer diameter 90 mmΦ, wall thickness 8 mm, length 18
A liner material of 00 mm was obtained. During casting, the die preheating temperature was set to 200 ° C., and wet spray coating was used to form a 0.8 mm thick coating mold with diatomaceous earth as the main material and water glass as a binder on the inner peripheral surface of the mold. Was done.

[0012]

[Table 1]

A sample for observing the structure was taken from the above liner material.
When taken and observed under a microscope, all samples were found in the tissue.
Crystallization of A-type graphite was observed. Also, cut the same material
Obtain a cylindrical liner sample with a length of 200 mm and finish it
Then, it was subjected to a corrosion wear test and a high temperature dry wear test.
For the corrosive wear test, the Kaken type wear tester was used
Rotate around the axis at 0.25m / sec, P on the outer surface
H = 2.0 H₂SO _Four1.5 cc / min of aqueous solution
Drop under the conditions, and the tip contact part is shaped with a radius of 10 mm
Press the formed pressure member with a load of 2 kg and press it 3
The amount of wear per hour was measured. The pressure member is 17C
r Steel is nitrided and has a surface hardness of Hv8
It was 00. On the other hand, the high temperature dry wear test
Using the same conditions, rotate the sample under the same conditions and apply the initial oil to the outer surface.
After application, wipe off and apply a pressure of 6 kg to the pressure member.
The amount of wear per 4 hours was measured. In this case, the axis of the sample
Insert a rod-shaped heater into the sample and keep the sample temperature at 180 ℃.
It was The test results are shown in Table 2 below.

[0014]

[Table 2]

From Table 2, No. 1 according to the embodiment of the present invention. 1
Nos. 4 to 4 of the conventional example. On the other hand, it is recognized that the corrosion wear amount and the high temperature dry wear amount are both reduced to about 1/2 or less.

[0016]

As described above, since the cast iron for cylinder liner of the present invention is formed of a specific component containing Cu: 0.5 to 1.5%, seizure resistance due to crystallization of A-type graphite. It also has excellent corrosion resistance and high temperature wear resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Yoshino 64 Nishimukojima-cho, Amagasaki City, Hyogo Prefecture Kubota Co., Ltd. Amagasaki Plant

Claims (1)

[Claims] 1. The chemical composition is% by weight, C: 3.1 to 3.5%, Si: 2.0 to.
2.6%, Mn: 0.5-1.0%, P: 0.1-
0.4%, Cr: 0.15 to 0.5%, Cu: 0.5 to
Cast iron for a cylinder liner, characterized in that 1.5%, B: 0.02 to 0.06%, and the balance being substantially Fe.