JP2000337511A - Piston-ring abrasion-resistant ring made of free-graphite precipitated iron system sintered material excellent in abrasion resistance and heat conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent abrasion resistance and reduce a counter attack property in free carbon precipitated iron system sintered material by letting exist no free graphite in base material, actually depositing free graphite only in blow holes to grow, and dispersedly distributing hard metal carbide or nitride particles in the base material. SOLUTION: The sintered material is obtained by respectively containing C: 0.5-5% as free carbon forming component and base material reinforcing component, and Cr: 0.5-5%, Mn: 0.2-1%, S: 0.05-1%, B: 0.05-1%, Ni: 1-12%, Ti: 0.5-5%, Cu: 8.5-20%, as base material forming component. If necessary, it is constituted of Mo: 0.1-2%, further carbide, nitride, and carbide/nitride of 4a, 5a, 6a group metal in the periodic table (Ti, Zr, Hf, Ta, Nb, V, Cr, Mo, and W), contained with hard metal carbide-nitride: 0/1-5% showing average particle size of 0.1-5 μm in the sectional structure observation by an electron microscope, and excellent heat conductivity and wear resistance are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent thermal conductivity, exhibits excellent abrasion resistance even in practical use under conditions in which the top ring groove of the piston has moved upward, and further has an aggressiveness against the opponent. (Piston ring aggressiveness) This invention relates to a piston ring made of a free graphite-precipitated iron-based sintered material having a small resistance.

[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 unavoidable, 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, Ni and S components, or Cr, Mn and S components, and further, if necessary, an atomized Fe alloy powder containing a predetermined amount of a Mo component in addition to these components; , H-BN) powder and / or boric acid powder, and titanium hydride (hereinafter, referred to as TiHx) powder, Ni powder, Mo powder, Mn powder, Cu powder,
S (sulfur) powder and graphite powder are used, and for example, TiC, TiN, TiCN, ZrC, HfN, V
C, WC, Mo ₂ C, Cr ₃ C ₂ , (Zr, Cr) C,
Group 4a, 5a, and 6a metals (Ti, Zr, Hf, Ta, Nb, V, Cr, M) of the periodic table represented by chemical symbols such as (Ta, Nb) N and (Ti, Mo) CN.
o, and W) carbides, nitrides, and carbonitrides, and two or more of these solid solutions, and
Using a hard metal charcoal / nitride powder having an average particle size of 5 μm, blending these raw material powders in a predetermined composition, mixing them under ordinary conditions, and pressing them into a 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, preferably 40
Sintering at a cooling rate of not more than 600 ° C./min at least to 600 ° C., as a free graphite forming component and a base reinforcing component, C: 0.5 to 5%, both as a base forming component, 0.5 to 5%,%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, Ni: 1 to 12%, Ti: 0.5 to 5 %, Cu: 8.5 to 20%, and if necessary, Mo: 0.1 to 2%.
And 4a, 5a, and 6a of the periodic table
Group metals (Ti, Zr, Hf, Ta, Nb, V, Cr, M
o) and one or more of the carbides, nitrides, and carbonitrides of W), and two or more of these solid solutions, and the cross-sectional structure is observed by an electron microscope with a cross-sectional structure of 0.1%.
Hard metal charcoal / nitride particles exhibiting an average particle size of μ5 μm:
0.1 to 5%, with the balance having a composition comprising Fe as a base forming component and unavoidable impurities, and desirably a density of 6.0 to 7.2 g / cm 3, that is, 80 to 9 g / cm 3.
Observation of the cross-sectional structure by an optical microscope at a theoretical density ratio of 5%, in other words, when the piston ring wear ring is formed of an iron-based sintered material having pores of 5 to 20 area% in the entire structure, this piston In the ring bearing ring, at the sintering temperature, the C component (graphite powder) is dissolved in the Fe alloy powder forming the base, and the dissolved C component is the B component of the h-BN powder and the boric acid powder. And the Fe
Due to the synergistic action of the S component dissolved in the alloy powder, it precipitates and grows as free graphite in the pores during the cooling process, and as a result, the precipitated free graphite substantially exists only in the pores. , Excellent seizure resistance and high temperature lubricity,
On the other hand, the base is substantially free of precipitated free graphite,
Not only is it significantly strengthened, but Ni, C
The r, Mn, and Ti components and, if necessary, the Mo component form a solid solution, and the main component becomes austenite having excellent heat resistance, exhibiting low partner aggression and exhibiting excellent heat-resistant plastic deformability, Further, due to the inclusion of the Cu component, excellent thermal conductivity is obtained. As a result, even if the top ring groove of the piston is moved upward, the Vickers hardness (Hv) distributed and distributed on the substrate is 1800 to 3 V.
Research results have shown that excellent wear resistance can be exhibited over a long period of time in combination with the wear resistance improvement effect of hard metal carbon / nitride particles having a high hardness of 200.

The present invention has been made on the basis of the above research results, and contains 0.5 to 5% of C as a free graphite forming component and a base strengthening component, and Cr: 0 as a base forming component. 0.5-5%, Mn: 0.2-1%, S: 0.05-1%, B: 0.05-1%, Ni: 1-12%, Ti: 0.5-5%, Cu : 8.5 to 20%, and if necessary, Mo: 0.1 to 2%.
And 4a, 5a, and 6a of the periodic table
Group metals (Ti, Zr, Hf, Ta, Nb, V, Cr, M
o) and one or more of the carbides, nitrides, and carbonitrides of W), and two or more of these solid solutions, and the cross-sectional structure is observed by an electron microscope with a cross-sectional structure of 0.1%.
Hard metal charcoal / nitride particles exhibiting an average particle size of μ5 μm:
0.1 to 5%, with the balance being Fe as a base forming component and unavoidable impurities, and the base is substantially composed of austenite, and free graphite is substantially present in the base. The hard metal carbon / nitride particles exist in a state in which they are deposited and grown in the pores without growing, and the base is composed of a free graphite precipitated iron-based sintered material having a structure in which the hard metal carbon / nitride particles are dispersed and distributed. It has excellent heat conductivity, exhibits excellent wear resistance even when the top ring groove in the piston moves upward, and has a characteristic of a piston ring wear ring made of free graphite precipitated iron-based sintered material that has low opponent aggression. Things.

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) CC In addition to improving the strength of the C component by dissolving it in the base material, it also precipitates as free graphite in the pores due to the coexistence of the B and S components as described above to improve seizure resistance and lubricity. Thus, while contributing to the improvement of wear resistance and having an action of alleviating the aggressiveness of the partner, if the content is less than 0.5%, a desired improvement effect cannot be obtained in the above-mentioned action. 5
%, The strength tends to sharply decrease, so the content is 0.5 to 5%, preferably 1%.
３3%.

(B) Cr The Cr component mainly forms a solid solution in an austenitic matrix,
This has the effect of improving the heat resistance and the heat plastic deformation resistance, thereby contributing to the improvement of the wear resistance of the piston ring wear ring. If the content is less than 0.5%, the desired effect can be obtained. On the other hand, if the content exceeds 5%, the precipitation and growth of graphite by the B component and the S component will be suppressed, so that the content is reduced to 0.1%.
5-5%, preferably 1-3%.

(C) Mn The Mn component has a function of improving the strength by forming a solid solution in the base material, but if its content is less than 0.2%, the desired effect of improving the 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%. .

(D) S and B These components have the function of positively precipitating and growing the solid solution C component as fine free graphite in the pores during the cooling process by the synergistic action. Graphitization 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, the seizure resistance and lubricity, that is, the abrasion resistance, are not sufficiently improved, and hard cementite (F
e3 C) starts to precipitate and the aggressiveness of the opponent (piston ring aggressiveness) increases. On the other hand, when the content of any of the S and B components exceeds 1%,
Not only does the sinterability deteriorate, and the desired strength cannot be ensured, but also ferrite appears on the base material, and as a result, austenite decreases to secure the desired heat-resistant plastic deformability. Can no longer be obtained, the content is S: 0.05-1%,
Desirably, 0.1 to 0.5%, B: 0.05 to 1%, desirably 0.1 to 0.5%.

(E) Ni and Ti These components form a solid solution with the matrix to promote the formation of austenite, and as described above, co-solve with the Cr component to improve the heat resistance and the heat plastic deformation resistance of the matrix. Improve
Therefore, it has the effect of contributing to the improvement of abrasion resistance. However, if the 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. However, for Ni, 12% is sufficient for forming the base material mainly composed of austenite, and for Ti, if it exceeds 5%, the strength is reduced. Ni: 1 to 12%, preferably 3
-8%, Ti: 0.5-3%, preferably 1-3%. As for the Ti component, as a raw material powder,
It is desirable to use Hx powder to activate the 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) Hard metal charcoal / nitride particles Hard metal charcoal / nitride particles are all Hv: 1800
Although it has a predetermined high hardness in the range of 3200 and contributes to improvement of wear resistance, if its content is less than 0.1%, it is not possible to secure desired excellent wear resistance. If the proportion exceeds 5%, the aggressiveness against the ball stud as the mating member increases, and the wear of the ball stud is remarkably promoted. Therefore, the content is 0.1 to 5%, preferably 0%. 3-4%. In this case, the average particle size of the hard metal carbon / nitride particles is set to 0.1.
In order to reduce the particle diameter to less than 1 μm, the raw material powder has an average particle diameter of 0.1 μm.
It is necessary to use a hard metal charcoal / nitride powder having a particle diameter of less than 1 μm. However, adjusting the average particle diameter of the hard metal charcoal / nitride powder having a particle diameter of less than 0.1 μm not only causes an increase in cost but also increases the average particle diameter. When the average particle diameter is less than 0.1 μm, it is difficult to obtain a desired excellent effect of improving wear resistance.
If it exceeds m, the strength of the base material is inevitably reduced, and the aggressiveness against the ball stud as a mating member is also increased. Therefore, the average particle size is 0.1 to 5 μm, preferably 0.5 to 4 μm. It was decided.

(H) Mo The Mo component is dissolved as needed in the base material and has the effect of further improving its strength. Therefore, the Mo component is contained if necessary. When 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 6.0 g / g. cm @ 3, and the desired density of 6.0 to 7.2 g / cm @ 3 cannot be obtained, and the desired strength cannot be secured. , Preferably 0.5 to 1.5%.

[0014]

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 in the 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%), TiHx powder, Ni powder, Mo powder, Mn powder,
Cu powder, S (sulfur) powder, graphite powder, h-BN powder,
And boric acid powder, and as raw material powders for forming hard metal carbon / nitride particles, TiC powder, TiN powder, TiN powder each having a predetermined average particle size in the range of 0.1 to 5 μm.
CN powder, ZrC powder, HfN powder, VC powder, WC powder, Mo ₂ C powder, Cr ₃ C ₂ powder, (Zr, Cr) C
[By weight ratio (hereinafter the same), ZrC / Cr ₃ C ₂ = 1 /
2] powder, (Ta, Nb) N [TaN / NbN = 2 /
1] Powder and (Ti, Mo) CN [TiN / Mo ₂
C = 1/3] powder, and these raw material powders are shown in Tables 1 and 2
And 0.7% of zinc stearate was added as a lubricant, mixed with a V-type mixer for 30 minutes, and pressed into a green compact at a pressure of 6 ton / cm @ 2.
This green compact is heated in an ammonia decomposition gas atmosphere at a temperature of 11
After holding at 40 ° C. for 1 hour, cooling at 35 ° C./min.
By sintering under the condition of gradually cooling to 50 ° C. and then allowing to cool, it has substantially the same composition as the composition shown in Tables 1 and 2, and has an outer diameter of 120 mm × an inner diameter of 102 mm × thickness:
Piston ring wear rings of the present invention (hereinafter referred to as the present invention wear rings) 1 to 29 having a size of 7 mm were produced, respectively. Each of the above wear-resistant rings 1 to 29 of the present invention is 6.2 to 6.2.
It has a density in the range of 7.1 g / cm 3, and its arbitrary cross section is observed for its structure using an optical and an electron microscope. As a result, the base material is made of austenite, or the base material is austenite and a slight pearlite is present, In addition, free graphite precipitates and grows in the pores, substantially no free graphite is deposited on the substrate, and the substrate shows a structure in which metal carbon / nitride particles are dispersed and distributed. Further, an optical microscope (magnification: 100 times) and an electron microscope (magnification: 1000)
The ratio of pores (free graphite) in the whole structure and the average particle size of the hard metal carbon / nitride particles were measured based on the structure photograph observed at 0 ×), and the results shown in Table 3 were shown. Further, for the purpose of comparison, in a normal high-frequency melting furnace, a melt of niresist cast iron having the same component composition as shown in Table 2 was prepared and cast into a shell mold.
A conventional piston ring wear ring having the same dimensions (hereinafter referred to as a conventional wear ring) was manufactured.

Next, the above-mentioned various wear rings are pretreated 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
Built into a 200cc direct-injection 6-cylinder diesel engine, rotation speed: 3600 rpm, engine cooling temperature:
An acceleration operation test is performed under the conditions of 90 ° C., operation mode: continuous operation for 500 hours, and load: full output, and the groove width of the top ring groove of the wear-resistant ring after the test is measured along the outer peripheral surface, and calculated from the measurement result. The wear resistance was evaluated based on the maximum wear amount (the maximum groove width after the test—the groove width before the test), and the piston ring (Fe-2.7) fitted in the top ring groove was used.
% Si-3.5% C made of spheroidal graphite cast iron
The aggressiveness of the partner was evaluated by measuring the maximum abrasion depth on the upper and lower surfaces of the r-plated one. Table 3 shows the results of these measurements.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

According to the results shown in Table 3, all of the wear rings 1 to 29 of the present invention have the free graphite-precipitated iron-based sintered material constituting the top ring groove despite the upward movement of the top ring groove. Free graphite does not exist in the base material, free graphite substantially only precipitates and grows in pores, and hard metal carbon / nitride particles are dispersed and distributed in the base material,
While it shows excellent wear resistance and has extremely low aggressiveness, the conventional wear ring made of Niresist cast iron does not have sufficient wear resistance. It is evident that not only the progress has been significantly accelerated, but also the opposition aggression is relatively large. As described above, the piston ring wear ring of the present invention has a small aggressiveness even when applied to an Al-Si alloy piston in a state where the position of the top ring groove is moved upward, and has excellent wear resistance. Because of its performance, it can fully satisfy the exhaust gas regulations of the engine, and its excellent thermal conductivity contributes to high output and large size of the engine. It has something.

[Brief description of the drawings]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16J 9/00 F16J 9/00 A 9/26 9/26 A // C22C 33/02 103 C22C 33/02 103E

Claims (2)

[Claims] 1. The composition according to claim 1, wherein the free graphite forming component and the base reinforcing component are:
5 to 5%, each as a base forming component, Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, Ni: 1 to 12%, Ti: 0.5 to 5%, Cu: 8.5 to 20%, and carbides, nitrides, and carbonitrides of metals of groups 4a, 5a, and 6a of the periodic table. Hard carbon / nitride particles comprising one or more of these two or more solid solutions, and exhibiting an average particle size of 0.1 to 5 μm by cross-sectional structure observation with an electron microscope: 0. 1 to 5%, and the balance is composed of Fe and inevitable impurities as a base forming component, and the base is substantially composed of austenite, and free graphite is substantially not present in the base. Exist in a state of being precipitated and grown in the pores, and the above-mentioned hard gold Piston ring made of free graphite-precipitated iron-based sintered material with excellent wear resistance and thermal conductivity, characterized by being composed of a free graphite-precipitated iron-based sintered material having a structure in which carbon and nitride particles are dispersed and distributed. ring. 2. In% by weight, as a free graphite forming component and a base reinforcing component, C: 0.
5 to 5%, each as a base forming component, Cr: 0.5 to 5%, Mn: 0.2 to 1%, S: 0.05 to 1%, B: 0.05 to 1%, Ni: 1 to 12%, Ti: 0.5 to 5%, Cu: 8.5 to 20%, Mo: 0.1 to 2%, and metals of groups 4a, 5a, and 6a of the periodic table. Consisting of one or more of carbides, nitrides, and carbonitrides, and two or more of these solid solutions, and exhibiting an average particle size of 0.1 to 5 μm by cross-sectional structure observation with an electron microscope. Metal carbon / nitride particles: 0.1 to 5%, the balance being Fe as a base forming component and inevitable impurities, and the main body of the base is substantially composed of austenite. Substantially non-existent in the substrate, present in a state of being deposited and grown in pores, and The structure is composed of a free graphite-precipitated iron-based sintered material having a structure in which the above-mentioned hard metal carbon / nitride particles are dispersed and distributed. Piston ring bearing ring made of free graphite precipitated iron-based sintered material with excellent properties.