JPH11269619A - Piston ring wear resistant ring made of free graphite-precipitated iron base sintering material excellent in high temperature wear resistance and thermal conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring wear resistant ring made of free graphite- precipitated iron base sintering material excellent in high temp. wear resistance and thermal conductivity and small in mating attackability. SOLUTION: A piston ring wear resistant ring is composed of a free graphite- precipitated iron base sintering material having a compsn. contg., by weight, 0.5 to 5% Cr, 0.2 to 1% Mn, 0.05 to 1% S, 0.05 to 1% B, 0.5 to 5% C, 1 to 12% Ni, 0.5 to 5% Ti and 8.5 to 20% Cu, further contg., at need, 0.1 to 2% Mo, and the balance Fe with inevitable impurities and moreover having a structure in which the base is consisting essentially of austenitic phases and precipitately grown free graphite is present in pores.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring wear ring made of a free graphite-precipitated iron-based sintered material having excellent high-temperature wear resistance and thermal conductivity and low aggressiveness (piston ring aggressiveness). It is about.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, Japanese Patent Publication No. 57-32743, a piston of a diesel engine for trucks and buses, for example, has a schematic longitudinal sectional view of FIG. Having a structure shown in the vertical sectional view of the part, and having a structure in which a piston ring wear ring is provided in the top ring groove immediately below the top land part as shown in the figure when the piston casting body is cast. It is well known. Further, the piston casting main body is mainly composed of an Al—Si alloy containing 8 to 13% by weight of Si.
Fe-Ni-Cu based sintered material with good wear resistance and low aggressiveness to the partner (composition: Fe-8 to 25% Ni-3.5 to 10)
% Cu-2.0% or less C) or a Ni-resist cast iron (composition: Fe-
1.5-3.5% Cr-0.8-1.5% Mn-3% or less C-13-22% Ni-8% or less Cu-1.0-2.
It is also well known that 8% Si, more than% by weight, and less than% represents% by weight) are widely used.

[0003]

On the other hand, exhaust gas regulations for automobiles tend to be stricter year by year. One of the measures to cope with this problem is to use a diesel engine for trucks and buses with a top just below the top land of the piston. The position of the ring groove is moved upward to reduce the volume of the void formed by the outer peripheral surface of the top land portion, the top ring upper surface, and the inner peripheral surface of the cylinder, so that the void portion is discharged to the atmosphere without burning. Attempts have been made to reduce the gas amount of the top ring groove, but when the position of the top ring groove is moved upward in this way, the temperature of the top ring groove sharply increases, and as a result, the piston ring wear ring has the above-mentioned Fe-Ni
-Even if it is composed of Cu-based sintered material or Niresist cast iron, the rapid progress of wear is inevitable, and this wear phenomenon is further accelerated with the recent increase in engine output and size, At present, gas leakage occurs from the worn portion.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoints, as a result of research to develop a piston ring wear ring that enables the piston to move upward in the top ring groove, as a result, the raw material powder is basically Fe and the alloy component is S (sulfur). ) Component, or N
an atomized Fe alloy powder containing predetermined amounts of i and S components, Cr, Mn, and S components, and if necessary, Mo components, and hexagonal boron nitride (hereinafter, h
-Indicated by BN) and / or boric acid powder;
Further titanium hydride (hereinafter, indicated by TiH _x) powders, N
Using i-powder, Mo-powder, Mn-powder, Cu-powder, S (sulfur) -powder, and graphite powder, these raw-material powders were blended into a predetermined composition, mixed under ordinary conditions, and pressed into a green compact. In this state, the green compact is heated in a reducing atmosphere to a predetermined temperature within a range of 1100 to 1250 ° C. at which a relatively high sintering temperature is obtained, and after holding for a predetermined time, a relatively slow cooling rate, desirably. Is sintered at a cooling rate of 40 ° C./min or less at a cooling rate of at least 600 ° C., Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1% B: 0.05-1%, C: 0.5-5%, Ni: 1-12%, Ti: 0.5-5%, Cu: 8.5-20%, further required Mo: 0.1 to 2%, with the balance being Fe and unavoidable impurities, and Density of Mashiku 6.0~7.2g / cm ^3,
In other words, when an iron-based sintered material having a theoretical density ratio of 80 to 95% is formed, in this iron-based sintered material, the C component ( Graphite powder) is dissolved, and the dissolved C component is combined with the B component of the h-BN powder and boric acid powder and the Fe component.
By the synergistic action of the S component dissolved in the alloy powder, during the cooling process, it precipitates as free graphite in the pores, grows, and exhibits excellent seizure resistance and high-temperature lubrication. The piston ring wear ring made of a sintered material is composed of free graphite deposited and grown in the pores, Ni, Cr, Mn,
And a Ti component and, if necessary, a Mo component as a solid solution, and a base mainly composed of an austenitic phase having excellent heat resistance, thereby exhibiting low aggressiveness to a partner and excellent high-temperature wear resistance. In addition, the present inventors have obtained a research result that the thermal conductivity becomes excellent due to the inclusion of the Cu component, and as a result, the position of the top ring groove in the piston can be moved upward.

The present invention has been made on the basis of the above-mentioned research results, wherein Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, C: 0.5 to 5%, Ni: 1 to 12%, Ti: 0.5 to 5%, Cu: 8.5 to 20%, and if necessary , Mo: 0.1 to 2%, the balance being Fe and inevitable impurities, and the base material is mainly composed of an austenite phase and has a structure in which free graphite precipitated and grown is present in pores. A piston ring made of graphite-precipitated iron-based sintered material, which has low aggressiveness to the partner and has excellent high-temperature abrasion resistance and thermal conductivity. is there.

Next, the reason why the component composition of the free graphite-precipitated iron-based sintered material constituting the piston ring wear ring of the present invention is limited as described above will be described. (A) Cr The Cr component forms a solid solution in a matrix mainly composed of an austenite phase to improve its heat resistance, and thus has the effect of contributing to the improvement of the high-temperature wear resistance of the piston ring wear ring. If the amount is less than 0.5%, a desired improvement effect on the above-mentioned effect cannot be obtained, while if the content exceeds 5%, the precipitation and growth of graphite by the B component and the S component will be suppressed. Therefore, the content is 0.5 to 5%,
Desirably, it was set to 1 to 3%.

(B) Mn The Mn component has a function of improving strength by forming a solid solution in a base material. However, if its content is less than 0.2%, a desired effect of improving strength cannot be obtained. Exceeds 1%, the graphitization by the B component and the S component is significantly inhibited. Therefore, the content is set to 0.2 to 1%, preferably 0.4 to 0.8%. .

(C) S and B These components have the function of positively precipitating and growing graphite dissolved in solid solution as fine free graphite mainly in pores during the cooling process by synergistic action. The graphitizing effect is
As for the S component, a predetermined amount of S is in principle added to Fe, Fe—Ni alloy, Fe—Ni—Mo alloy, and further to Fe—Cr—Mn alloy or Fe—Cr—Mn—Mo alloy, respectively.
Fe alloy powder formed by atomizing the molten metal containing the component, and for the B component, h-
The use of BN powder and boric acid powder as raw material powders is further promoted, but if the content of any of the S and B components is less than 0.05%, desired graphitization can be achieved. As a result, not only the improvement in seizure resistance and high-temperature lubricity, that is, the improvement in high-temperature abrasion resistance is insufficient, but also hard cementite (Fe ₃ C) is precipitated, thereby causing an attack on the opponent. When the content exceeds 1% of any of the S and B components, the sinterability is reduced and the desired strength can be secured. Not only does it disappear, but the ferrite phase appears on the base material, and as a result, the austenite phase decreases and the desired high-temperature wear resistance cannot be secured. The content of each S: 0.0
5 to 1%, desirably 0.1 to 0.5%, B: 0.05
１1%, desirably 0.1 to 0.5%.

(D) CC In addition to improving the strength by dissolving in the base material, the C component precipitates in the pores as free graphite as described above to improve seizure resistance and high-temperature lubricating properties, and thus has high-temperature wear resistance. While it has the effect of contributing to the improvement of the aggressiveness and the effect of alleviating the aggressiveness of the opponent, if the content is less than 0.5%, the desired effect of improving the effect cannot be obtained, while the content exceeds 5%. And the strength tends to sharply decrease, the content is determined to be 0.5 to 5%, preferably 1 to 3%.

(E) Ni and Ti These components form a solid solution in the matrix to promote the formation of the austenite phase, and improve the heat resistance of the austenite phase by co-dissolution with the Cr component as described above. Therefore, it has the effect of contributing to the improvement of high-temperature wear resistance. However, if its content is less than 1% of Ni and less than 0.5% of Ti, a desired improvement effect cannot be obtained in the above-mentioned effect. If the amount is Ni, the formation of austenite phase is 12%.
% Is sufficient, and in the case of Ti, if it exceeds 5%, the strength decreases. Therefore, the content is set to Ni: 1 to 12%, preferably 3 to 8%, and Ti:
0.5-3%, preferably 1-3%. Note that T
Regarding the i component, it is desirable to use TiH _x powder as a raw material powder to activate sintering and to exert a strong reducing action by decomposed hydrogen during sintering.

(F) Cu The Cu component has a function of further improving the thermal conductivity and reducing the aggressiveness of the partner in addition to the strength improvement by liquid phase sintering, but the content thereof is less than 8.5%. In the above, the desired effect cannot be obtained in the above-mentioned action, while if the content exceeds 20%,
Since the hardness rapidly decreases and the wear resistance decreases, the content is 8.5 to 20%, preferably 12%.
１８18%.

(G) Mo The Mo component has a function of improving the strength by forming a solid solution in the base material. Therefore, the Mo component is contained if necessary.
If the content is less than 1%, the desired strength-improving effect cannot be obtained, while if the content exceeds 2%, the press formability (compressibility) of the raw material powder (mixed powder) is reduced, and as a result, the density of the sintered material is reduced. There becomes less than 6.0 g / cm ^3, can not be obtained density of 6.0~7.2g / cm ³ is desirable density, since it becomes impossible to ensure a desired strength, the content of Was determined to be 0.1 to 2%, preferably 0.5 to 1.5%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The piston ring wear ring of the present invention will be specifically described with reference to examples. As the raw material powder, an atomized Fe-S alloy powder (containing 0.34% of S) and an atomized Fe-Ni-Mo-S alloy powder (N: N) each having a predetermined average particle size within a range of 10 to 150 µm.
i: 4.1%, Mo: 1.5%, S: 0.12%), atomized Fe-Cr-Mn-S alloy powder (C
r: 2.3%, Mn: 0.72%, S: 0.21%), TiH _x powder, Ni powder, Mo powder, Mn powder,
Cu powder, S (sulfur) powder, graphite powder, h-BN powder,
And boric acid powder are prepared, and these raw material powders are blended in a predetermined blending composition.
Add 7% and mix with V-type mixer for 30 minutes, 6 tons
/ Cm ^{2 at} a pressure of 1 / cm ² , press-molding the green compact in an ammonia decomposition gas atmosphere at a temperature of 1140 ° C. for 1 hour, and then gradually cooling to 550 ° C. at a cooling rate of 35 ° C./min. By sintering under the condition of standing to cool, it has the component composition shown in Tables 1 and 2, and has an outer diameter of 120 mm and an inner diameter of 10
Piston ring wear rings of the present invention (hereinafter, referred to as the present invention wear rings) 1 to 29 each having a size of 2 mm × thickness: 7 mm were produced. Each of the above wear rings 1 to 29 of the present invention has a density in the range of 6.2 to 7.1 g / cm ³ , and has a base material of an austenite phase or a base material of an austenite phase and a slight pearlite phase. , And the results of optical microscopic observation of the structure in which free graphite was precipitated in the pores were shown. Further, for comparison purposes, a melt of niresist cast iron having the same component composition as shown in Table 2 was prepared in a normal high-frequency melting furnace, and this was cast into a shell mold, and a conventional mold having the same dimensions was prepared. A piston ring wear ring (hereinafter referred to as a conventional wear ring) was manufactured.

Next, the above-mentioned various wear rings are pre-treated under ordinary conditions, ie, degreasing, drying, and temperature: 700 ° C.
After being pre-treated for immersion for 5 minutes in an Al-Si-based alloy melt having the same composition as that of a cast Al-Si-based alloy melt described later, each was placed in a piston precision casting mold, and the Al -12.1% Si-1.03% Cu-1.05
% Mg-0.87% Ni molten alloy is cast to form a piston body, and at the same time, the wear ring is wrapped around, and then the wear ring is cut along the outer peripheral surface. By forming a top ring groove having a dimension of groove depth: 7 mm × groove width: 3 mm, the distance between the top land portion upper surface and the top ring groove upper surface is 5 mm (the distance conventionally used in this type of piston). (Usually 15 mm), a piston made of an Al-Si alloy and moved above the top ring groove.

Further, these pistons are provided with a displacement of 8
Installed in a 200cc direct-injection 6-cylinder direct-injection diesel engine, rotation speed: 3500 rpm, engine cooling temperature:
Accelerated operation test is performed under the conditions of 80 ° C., operation mode: continuous operation for 500 hours, and load: full output, and high-temperature wear resistance is measured by measuring the maximum groove width of the outer peripheral surface of the top ring groove of the ring after the test. The piston ring (Fe-2.7% -3.
The aggressiveness of the opponent was evaluated by measuring the maximum wear depth on the upper and lower surfaces of a chromium-plated spheroidal graphite cast iron having a composition of 5% C. Table 3 shows the results of these measurements.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

From the results shown in Table 3, all of the wear rings 1 to 29 of the present invention show excellent high-temperature wear resistance despite the upward movement of the top ring groove, and also have an aggressiveness against the opponent. In contrast to the extremely small size, the conventional wear ring made of Niresist cast iron does not have sufficient high-temperature wear resistance. It is. As described above, the piston ring anti-wear ring of the present invention has an aluminum ring with the position of the top ring groove moved upward.
-Since it has low opponent aggression and exhibits excellent high-temperature wear resistance even when applied to a piston made of Si alloy, it can sufficiently respond to engine exhaust gas regulations and has excellent The heat conductivity has industrially useful characteristics, such as contributing to higher output and larger size of the engine.

[Brief description of the drawings]

FIG. 1A is a schematic longitudinal sectional view illustrating a piston of a diesel engine, and FIG.

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[Procedure amendment]

[Submission date] March 11, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Further, these pistons are provided with a displacement of 8
Installed in a 200cc direct-injection 6-cylinder direct-injection diesel engine, rotation speed: 3500 rpm, engine cooling temperature:
An accelerated operation test was performed under the conditions of 80 ° C., operation mode: continuous operation for 500 hours, and load: full output, and the groove width of the top ring groove of the ring after the test was measured along the outer peripheral surface.
Maximum wear calculated from the results (maximum groove width after test-test
The high-temperature wear resistance was evaluated based on the groove width before the test, and the piston ring (Fe-
The aggressiveness of the partner was evaluated by measuring the maximum wear depth on the upper and lower surfaces of a 2.7% Si- 3.5% C (Cr-plated spheroidal graphite cast iron) composition. Table 3 shows the results of these measurements.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018]

[Table 3]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B22F 5/02 B22F 5/02 C22C 33/02 103 C22C 33/02 103E

Claims (2)

[Claims] 1. Weight%: Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, C: 0.5 -5%, Ni: 1-12%, Ti: 0.5-5%, Cu: 8.5-20%, the balance being Fe and unavoidable impurities, and the base material is mainly composed of austenite phase And free graphite-precipitated iron with excellent high-temperature abrasion resistance and thermal conductivity, characterized by being composed of a free graphite-precipitated iron-based sintered material having a structure in which free graphite is deposited and grown in pores. Piston ring wear ring made of sintered material. 2. In% by weight, Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, C: 0.5 -5%, Ni: 1-12%, Ti: 0.5-5%, Cu: 8.5-20%, and Mo: 0.1-2%. A high temperature characterized by comprising a composition comprising Fe and unavoidable impurities, and a base composed mainly of an austenitic phase, and a free graphite-precipitated iron-based sintered material having a structure in which free graphite is deposited and grown in pores. Piston ring wear ring made of free graphite precipitated iron-based sintered material with excellent wear resistance and thermal conductivity.