JPH06184692A - Rotary compressor roller - Google Patents

Abstract

PURPOSE:To improve the sliding characteristics, such as wear resistance, of a rotary compressor roller by refining flake graphite to refine a matrix and regulating the amounts of hard Cr and vanadium to specific values, respectively. CONSTITUTION:Flake graphite cast iron having a composition consisting of, by weight, 2.6-3.6% carbon, 1.8-3.2% silicon, 0.4-1.2% manganese, <=0.2% phosphorus, <=0.15% sulfur, 0.1-0.5% chromium, 0.5-2.0% nickel, 0.5-2.0% Mo, 0.05-0.5% vanadium, and the balance iron with inevitable impurities is subjected to oil quenching at 880 deg.C for 2hr and to tempering at >=250 deg.C for 2hr, by which a hardness of about HRC50 can easily be obtained. Although the temp. of the roller during operation of compressor is generally said to rise to 250-300 deg.C, the occurrence of deterioration in hardness during use can be prevented by using the material of this invention.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller for a rotary compressor, and more particularly to a roller for a small compressor such as a compressor for a refrigerator or a compressor for a room air conditioner.

[0002]

2. Description of the Related Art As shown in FIG. 2, a rotary compressor is a roller in which the tip of a vane 1 fitted in a groove formed in a cylinder 3 is biased inside the cylinder by using a dedicated spring. When the roller 2 is eccentrically rotated by a power source (not shown), the space defined by the roller 2, the cylinder 1 and the vane 3 causes a volume change to compress the gas. Conventionally, in such a compressor, the roller 2 is composed of eutectic cast iron and flake graphite cast iron (F
C25 material, etc. and monichrome cast iron in which steadite was precipitated were also used, which were subjected to heat treatments such as quenching and tempering. On the other hand, as the vane slidingly contacting the roller 1, high speed steel (SKH51), high chromium bearing steel (SUJ-2), die steel (SKD11, SKD12) and high carbon / high chromium stainless steel (SUS440C) were used. . In some cases, these materials were nitrided before use.

Monichrome cast iron is a Ni-Cr-Mo type flake graphite alloy cast iron, which is intended to improve friction characteristics by flake graphite and improve wear resistance etc. by a matrix in which phosphide is dispersed. Is. An example of the metallographic structure of monichrome cast iron is shown in the photograph (B) of FIG. 1, which is composed of flake graphite g having sharp tips, martensite m (base), and phosphide s.

[0004]

A rotary compressor for a gas compressor is often used at a high rotation speed due to its compact size and light weight, so that the sliding condition of the roller is becoming severe. Further, as a compressor for a refrigerator or a compressor for a room air conditioner, R-12, which has been used as a refrigerant until now, has been banned in the near future due to concern over destruction of the ozone layer. R-12
The alternative new refrigerant of (3) has poor lubrication oil retention properties, which deteriorates the sliding conditions. Therefore, the usage environment of the rollers of the rotary compressor is becoming more severe.

Under such circumstances, with the current combination of rollers and vanes, sliding problems such as seizure and wear of sliding parts have occurred even in the case of monichrome cast iron having good sliding performance. In the structure of monichrome cast iron shown in FIG. 1 (B), the flake graphite is large, the matrix structure is rough, and the phosphide is brittle. This cast iron causes adhesive wear when sliding in a new refrigerant environment. It is thought that the cause is easy and poor in durability. The present invention, which was conceived in view of the situation in which the improvement of the durability of such a member is desired, makes the flake graphite fine,
It is an object of the present invention to provide a roller for a rotary compressor having improved sliding characteristics such as wear resistance by making a matrix fine and forming a metal structure with a strong carbide of chromium or vanadium.

[0006]

The rotary compressor roller according to the present invention has a carbon content of 2.6 to 3.6%, silicon of 1.8 to 3.2% and manganese of 0.4 to 1 by weight. 0.2%, phosphorus 0.2% or less, sulfur 0.15% or less, chromium 0.1
0.5%, nickel 0.5 to 2.0%, molybdenum 0.
5 to 2.0%, including vanadium 0.05 to 0.5%,
It is composed of flake graphite cast iron containing the balance iron and unavoidable impurities.

The reasons for limiting the composition of the flake graphite cast iron of the present invention will be described below. Carbon is an element that forms flake graphite. If the carbon content is less than 2.6% by weight, chilling occurs and the machinability deteriorates, while if it exceeds 3.6% by weight, coarse graphite occurs and the hardness and abrasion resistance decrease. Therefore, the carbon content needs to be in the range of 2.6 to 3.6% by weight.

Silicon is an element necessary for promoting the formation of flake graphite. If the silicon content is less than 1.8% by weight, chilling will make machining difficult, while if it exceeds 3.2% by weight, coarse graphite will be generated to lower the hardness. Therefore, the silicon content is 1.8 to 3.2.
It must be in the range of wt%.

Manganese is an element that improves hardenability. If the content of manganese is less than 0.4% by weight, the hardenability is lowered, resulting in deterioration of wear resistance, while if it exceeds 1.2% by weight, chilling makes machining difficult, and residual austenite becomes excessive. As a result, the dimensional change during heat treatment becomes large. Therefore, the manganese content is 0.4-
It should be 1.2% by weight.

Phosphorus is an impurity, and if it exceeds 0.2% by weight, it forms steadite and makes cast iron brittle, so it must be 0.2% by weight or less. Sulfur is an impurity of 0.1
If it exceeds 5% by weight, not only the toughness and strength decrease, but
Since it binds to vanadium and molybdenum and deteriorates the intended performance, it is necessary to set it to 0.15% by weight or less.

Chromium improves wear resistance by forming carbides and refining graphite. When the content of chromium is less than 0.1% by weight, carbides become too small and coarse graphite is generated to deteriorate wear resistance. On the other hand, when the content of chromium exceeds 0.5% by weight, chilling occurs and machinability deteriorates. Therefore, the content of chromium is 0.
It should be 1 to 0.5% by weight.

Nickel improves wear resistance by improving hardenability. If the nickel content is less than 0.5% by weight, hardenability is low, while 2.0% by weight
When it exceeds, the residual austenite becomes excessive and the dimensional change during heat treatment becomes large. Molybdenum also improves wear resistance by improving hardenability. When the content of molybdenum is less than 0.5% by weight, hardenability is low,
On the other hand, if it exceeds 2.0% by weight, the residual austenite becomes excessive and the dimensional change during heat treatment becomes large.

Vanadium is an element necessary for forming carbides and improving wear resistance by fine graphitization. If the vanadium content is less than 0.05% by weight, the amount of carbides is too small and coarse graphite is generated. On the other hand, if the vanadium content exceeds 0.5% by weight, the carbides become excessive and machining becomes difficult. The amount of carbide is preferably 3 to 10% (area ratio).

Although the above-mentioned various properties are secured to some extent even in the as-cast condition, even better results can be obtained if a tempered martensite structure in which secondary carbides are dispersed by quenching and tempering treatment is obtained. In this case, HRc = 45-5
It is preferable to set the heat treatment conditions so as to obtain a hardness of 5, more preferably 50 to 55. Generally, the temperature of the roller is said to rise to 250 to 300 ° C. during the compressor operation, and the tempering temperature of the roller is also 250 ° C.
Is normal. However, in order to secure the hardness around HRC50, the conventional FC25 and monichrome cast iron were often limited to a tempering temperature of 220 to 250 ° C. This roller is oil-cooled at 880 ℃ for 2 hours and 250 ℃.
The hardness of about HRC50 is easily obtained by tempering for 2 hours or more, and therefore tempering at a temperature equal to or higher than the working temperature of the roller is possible.

[0015]

[Function] As described above, the contents of carbon and silicon are determined so that graphite can be easily deposited, and manganese, nickel and molybdenum improve the hardenability, and chromium and vanadium make the flake graphite fine and strong at the same time. The metallographic structure of the roller is shown in FIG.
As shown in the photograph of (A), fine flake graphite f
g, fine tempered martensite fm, and carbide c.

Further, since the cast iron of the present invention has a high hardness after quenching, the tempering temperature for obtaining a hardness of HRc of 50 or higher can be increased. Hereinafter, the present invention will be described in detail with reference to examples.

[0017]

Example: Dissolved materials were mixed in a high-frequency furnace at a predetermined mixing ratio to 150
Melt at 0 ° C, add a predetermined amount of manganese, chromium, nickel, molybdenum iron alloy so that the composition is as shown in Table 1, inoculate with silicon / iron alloy immediately before tapping from the furnace, and continue to produce raw sand at 1400 ° C. It was cast into and used as a roller casting material. The casting material is roughly processed into a cylinder with an outer diameter of 46 mm, an inner diameter of 30 mm, and a height of 40 mm, followed by quenching under oil-cooling conditions at 880 ° C. for 2 hours and tempering heat treatment at 250 ° C. for 2 hours. did. Then, the outer diameter was cylindrically polished. The hardness of the roller was HRC50. Table 1 shows an example thereof.

[0018]

[Table 1]  Heat treatment after abrasion resistance No. TC Si Mn PS Cr Ni Mo V Fe Hardness Abrasion  FC25 1 3.35 2.40 0.68 0.08 0.12 0.06 − − − Remaining HRC48 × Monikuro 2 3.49 2.51 0.81 0.25 0.15 0.51 0.20 0.18 − Remaining HRC50 × cast iron  Invention 3 2.68 1.89 0.75 0.09 0.15 0.16 0.88 0.95 0.10 Remaining HRC46 ○ ↑ 4 3.48 2.77 0.75 0.09 0.15 0.37 1.50 1.37 0.29 Remaining HRC51 ○ ↑ 5 3.58 3.02 1.16 0.10 0.18 0.48 1.97 1.91 0.48 Remaining HRC52 ○

The roller thus formed is SKH
A wear test was conducted by combining 51 materials and a stainless steel vane nitride. The wear test condition was a peripheral speed of 2 m / se.
c. The load was 15 kgf, and the wear amount was measured by using the profile measuring device to measure the change in the tip shape before and after the test. In addition, wear resistance is the same as that of the current Monichrome cast iron roller and SUS44.
When the amount of wear was small due to the combination with 0C nitride vane, it was evaluated as ◯, and conversely, it was evaluated as x. further,
As shown in the results of the pin-drum type wear test in FIG. 3, the roller of the present invention has good compatibility with the mating material and the amount of wear of itself is small.

[0020]

As described above, the combination of the current roller and the current vane was not sufficient in the sliding property, but according to the present invention, carbon 2.6 to 3.6%, silicon 1. 8-3.2%, manganese 0.4-1.2%, phosphorus 0.2% or less, sulfur 0.15% or less, chromium 0.1-
0.5%, nickel 0.5 to 2.0%, molybdenum 0.
A roller made of flake graphite cast iron containing 5 to 2.0% of vanadium and 0.05 to 0.5% of vanadium (both by weight) and having a composition range of the balance of iron, and heat treatment of quenching and tempering the roller. A roller having a hardness of HRC45 to 55 is expected to exhibit excellent performance in sliding under severe conditions.

[Brief description of drawings]

FIG. 1A is a photograph showing a metallographic structure of a roller of the present invention (magnification: 460 times), and (B) is a photograph showing a metallographic structure of a conventional roller (magnification: 400 times).

FIG. 2 is a schematic diagram of a rotary compressor.

FIG. 3 is a graph showing the results of a pin-drum type wear test.

[Explanation of symbols]

 1 vane 2 roller 3 cylinder

Claims (2)

[Claims] 1. By weight%, carbon 2.6-3.6%, silicon 1.8-3.2%, manganese 0.4-1.2%, phosphorus 0.2% or less, sulfur 0.15. % Or less, chromium 0.1
0.5%, nickel 0.5 to 2.0%, molybdenum 0.
5 to 2.0%, including vanadium 0.05 to 0.5%,
Rotating compressor roller made of flake graphite cast iron consisting of balance iron and unavoidable impurities. 2. A flake graphite cast iron rotary compressor roller having the composition of claim 1, heat treated and having a hardness in the range of HRC 45-55.