DE2615664A1 - IRON-BASED PISTON RING MADE OF A Sintered alloy - Google Patents

Description

Piston ring made from a sintered iron-based alloy

The invention relates to a piston ring made of a sintered iron-based alloy, which has a high resistance to Plague eating and wear and tear as well as good mechanical and physical Possesses properties.

Sintered alloys are known for reasons of low environmental pollution, the saving of raw materials, the production costs and the like. Widely used for machine parts. There are already different sintered alloys for the piston rings of internal combustion engines have been developed and used, these piston rings under difficult operating conditions show particularly good running properties.

Piston rings for internal combustion engines or compressors or compressor must have a high resistance to galling and wear and good mechanical and physical properties ,, so that they perfectly even under difficult operating conditions, etc. _o h "friction and

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# 09805/0688

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good seal, run. In this regard, however, the previously known sintered alloys are not satisfactory.

A component made of sintered alloy generally has a A large number of pores in which oil is retained, which increases the resistance of the component to pest-eating will. In the case of a component made of sintered alloy, which is pressed to a high density to improve its strength however, most of the pores are closed and the oil retention capacity of the component is reduced as a result, which also reduces its seizure resistance. In addition, the pores do not take part directly Lubrication part, rather they only serve as an oil sump, for this reason the pores are unable to allow for prevent seizing if the lubricating oil supply is interrupted for a longer period of time.

To eliminate the aforementioned disadvantages while at the same time solving the problems relating to thermal conductivity and the The modulus of elasticity of previously used sintered alloy piston rings is, according to the invention, in a base or a base material a certain amount of graphite (which has a high self-runnability and has good oil wetting properties) as well as on one. "Carbide (with a high degree of hardness) distributed, whereby a piston ring "with the desired resistance to seizing and wear is guaranteed,

The solution according to the invention consists of a piston ring an iron-based sintered alloy in that it has an EIa-

modulus of elasticity of about 7500 - 16000 kg / mm imä has a thermal conductivity of more than about 4.0 χ 10 cal / em »s« ^u C and cl & ß oils sintered alloy, in a basic structural element distributed etv-a 1 - 1fj £ graphite phs.ss per unit area and about 1.5 «· - 25y <carbide pli2.se per unit area.

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The following are preferred embodiments of the invention explained in more detail.

Graphite is a plague lubricant with good wetting properties, so that a certain amount of graphite distributed in a piston ring, the lubricating performance of the piston ring, the in the case of the sintered alloy components used up to now depends exclusively on the pores therein and able to favor. If doing so, the amount of graphite dispersed is less than about $ 1 per unit area (by area), the graphite is unable to provide the piston ring with the necessary lubricating performance If there is more than about $ 15 graphite per unit area, the graphite degrades the strength of the piston ring. It is not necessary that the graphite used is in a special form, rather the commercially available and graphites normally used in the art can be used with success in the invention.

A certain amount of carbide is also in the base or in the Base material distributed to improve the wear resistance of the piston ring. The amount required for this is in the range from about $ 1.5-25 per unit area. Is this proportion below this range, the piston ring shows decreased wear resistance. Has a larger proportion the piston ring, on the other hand, has a lower strength For improved wear resistance of the piston ring, carbides with more than HV75O (Vickers hardness) are preferred used. It is essential that the carbides used according to the invention have good wetting properties, i.e. a have good adhesion between the structural element and the carbide, since carbides with poor wetting properties separate from the base material during operation and remain as a foreign body between the piston ring and the cylinder, which favor the wear of the piston ring. Preferably

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can for the purpose provided according to the invention one, two or more carbides of the group consisting of cementite (austenite), vanadium, chromium, tungsten, molybdenum, titanium, boron, manganese, niobium, etc. are used will.

The graphite phase with its own lubricity and good wetting properties as well as the carbide phase with a high degree of hardness are present side by side in the base material, and these two alloy elements synergistically give the piston ring high resistance to seizing and wear. With the one in operation Occurring wear or abrasion, the carbide phase, which has a high degree of hardness, remains in shape in the base material of convex sections or areas that are highly wear-resistant Form sliding surface for the sliding movement along the counter-element (cylinder wall), while other areas with less Hardness are removed so that they form concave areas that serve as oil sumps for the lubrication of the sliding surface. In addition, it prevents a self-lubricating ability and graphite phase having good wettability with oil seizure even if the lubricant film between the piston ring and Cylinder has been interrupted for a long period of time.

According to the invention, pearlite is used as a basic structural element, i.e. as the material which, in addition to graphite and carbide forms the remainder of the sintered alloy piston ring of the invention. Bainite or martensite with an addition of nickel, Molybdenum or similar. are also useful. In terms of strength, it is also advantageous to use the base material sintering with copper or the like. to impregnate. The choice of the structural element depends on the loading conditions of the Internal combustion engine.

The modulus of elasticity is in the range of about 7500-16 kg / mm ² . If it is below this range, the mass increases

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and inertia force of the piston ring to impermissible values. If, on the other hand, this modulus of elasticity is above this range, then becomes the amount of the graphite phase is too small, so that the piston ring has poor seizure resistance.

In addition to good sliding properties, piston rings must also have high thermal conductivity. The reason for this is that a piston ring with poor thermal conductivity does not radiate heat generated during combustion and transferred to the piston ring and the cylinder via the latter, so that the temperature of the piston ring rises to an undesirably high value and causes difficulties. On the basis of test results, a piston ring with a thermal conductivity of more than about 4.0 10 cal / cm.s «° C has proven to be satisfactory. Without wishing to limit the invention, it can be said that the most advantageous results with a thermal conductivity in the range of about
10 cal / cmos. »° C can be achieved.

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conductivity in the range from about 4.0 χ 10 to about 15.0 χ

The invention is described below in specific examples:

example 1

3% by weight graphite powder (-0.044 mm = -525 mesh), 3% by weight cobalt powder (approx. -0.040 mm = -350 mesh), 2% by weight ferromolybdenum powder (6% molybdenum; -0.09 mm = -150 mesh), remaining reduced iron powder (-0.149 mm = -100 mesh) were mixed together and then under a pressure of 5 t / cm pressed to piston rings and at 1100 ⁰ C in an atmosphere of a reducing gas, ie, decomposed ammonia (where reformed propane gas "could be used with equal success"), sintered * The piston ring produced in this way (No. 1) had the following dimensions:

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Diameter: 83 mm; Width: 2 mm; Thickness: 3.8mm.

The basic structural element of the piston ring No. ₀ 1 was made of pearlite in which a graphite phase was dispersed in an amount of K% per unit area and a carbide phase in an amount of $ 8 per unit area. The piston ring had a modulus of elasticity of 10,000 kg / mm, a thermal conductivity of 6.2 10 cal / cm-s »° C and a hardness of HRB 80.

Example 2

3.5 wt .- ^ graphite powder (-0.044 mm = -325 mesh), 3.5 wt .- ^ molybdenum powder £ O, 149 mm = -100 mesh), 2 wt -.% Manganese powder (-0.149 mm = -100 mesh), 1 wt .- ^ nickel powder (about -0.09 mm = -150 mesh) and reduced in residual iron powder '(- 0.14 to 9 W® = -100 mesh) were mixed together, then a ^ unte pressed pressure of 5 t / cm in the piston ring shape, and then sintered at 1100 ⁰ C in an atmosphere of a reducing gas. The piston ring produced in this way (No. 2) had a diameter of 83 mm, a width of 2 mm and a thickness of 3.8 mm.

The base material element of the No. 2 piston ring was made of bainite in which 6% graphite phase and 10% carbide phase, each based on the unit area, were dispersed. The piston-

o ring had a modulus of elasticity of 14-000 kg / mm, a thermal

conductivity of 5.8 χ 10 " ² cal / em« s «° C and a hardness of HKB 93.

To investigate the performance of the piston rings No. 1 and No. 2, the internal combustion engine described below Wear resistance tests carried out. For comparison with the piston rings according to the invention, too a conventional piston ring (No. 3) made of sintered iron-based alloy is used

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261566A

Piston ring no.3
Composition:

C Cu No rest

1.2 4.0 0.5 Pe (wt .- ^)

Hardness: HRB 85
Basic structure: pearlite

Experimental internal combustion engine

Forced air-cooled two-cylinder four-stroke gasoline engine Bore χ stroke: 83 x 73 mm
Total stroke: 790 craP
Maximum power: 36 hp / 4600 rpm

Test conditions

Speed: 500 rpm

Power: 22 hp

Load: 7 kg

Test duration: 50 h

Oil temperature: 110 ⁰ C +10 ⁰ C

Cylinder: PC 25 (according to Japanese industrial standards)

The following test results were achieved:

Piston ring wear grade No. 1 7

No. 2 5

No. ₀ 3 15

From the above test results it can be seen that the inventive Sintered alloy piston rings No. 1 and 2 have a much higher wear resistance than the conventional one Cast piston ring.

Furthermore, tests were carried out with regard to the pest seizure resistance on a rotary wear testing machine. Included

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became specimens (Nos. 1 to 3) from those described above Piston rings No. T to 5 manufactured (dimensions 15 χ 20 χ 7 mm). In these · experiments, the load at which a plague was eaten of the test specimen occurred, measured by the fact that the turntable pressing against the test specimen concerned with continuous Lubricant supply was pressed against the test specimen with gradually increasing pressure load. There were the following test conditions were met:

(a) Turntable material: FC 25

(b) Lubricant temperature: 80 ° C

(c) Amount of lubricant: 0.6 l / h.

(d) Lubricant: Dufni Oil No. 65

The following test results were achieved:

Test item no. 1 | _{No plague} f _r eat at Beia test item no. 2 J ^{Stung VOnÜ3er 5} ° ^{kg / cm2}

Sample No. 5 seizure occurred under a load of 25 kg / cm2

From the above test results it can be seen that the inventive Sintered Alloy Piston Rings No. 1 and No. 2 have a significantly higher resistance to seizing than the conventional cast piston ring.

The ones in the internal combustion engine and on the rotary wear testing machine Tests carried out thus show that the sintered alloy piston rings according to the invention are suitable for use have superior operating properties in internal combustion engines.

Although the invention is based on preferred exemplary embodiments is described in detail are to the person skilled in the art

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of course, various changes and modifications are possible without departing from the scope and basic concept of the invention is deviated.

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Claims (3)

- ίο - Claims Piston ring made of sintered alloy on an iron base, characterized in that that it has a modulus of elasticity of about 7500-16000 kg / mm and a thermal conductivity of more than about 4.0 χ 10 cal / cm »s« ° C and that the sintered alloy, distributed in a basic structural element, about 1-15 wt .- $ graphite phase per unit area and about Contains 1 * $ 5 - $ 25 carbide phase per unit area. 2. Piston ring according to claim 1, characterized in that the carbide phase consists of one or more carbides of the group made of cementite (austenite) and carbides of vanadium, chromium, Consists of tungsten, molybdenum, titanium, boron, manganese and niobium » 3. Piston ring according to claim 2, characterized in that the basic structural element is pearlite, bainite or martensite. 709809/0696