COMPOSITE FOR WEAR-RESISTANT RING HAVING EXCELLENT HEAT CONDUCTIVITY

Abstract

Provided is a composite for a wear-resistant ring having excellent heat conductivity. In the composite for a wear-resistant ring, an iron-based sintered compact for a wear-resistant ring having a composition that contains, by mass, C of 0.4 to 1.5% and Cu of 20 to 40%, and having a structure in which pores exist continuously at a porosity of 15 to 50% in terms of volume fraction, and in which a matrix is pearlite, and in which a free Cu phase or further dispersion particles are dispersed in the matrix, is insert-cast in an aluminum alloy, and has the pores impregnated with the aluminum alloy.

Claims

1. A composite for a wear-resistant ring having excellent heat conductivity, which is formed by insert-casing an iron-based sintered compact for a wear-resistant ring in an aluminum alloy, wherein the iron-based sintered compact for a wear-resistant ring is an iron-based sintered compact comprising: a composition that comprises, by mass, C of 0.4 to 1.5% and Cu of 20 to 40% and is composed of a balance of Fe and inevitable impurities, and a structure in which pores exist continuously at a porosity of 15 to 50% in terms of volume fraction, a matrix is pearlite, and a free Cu phase is dispersed in the matrix, the aluminum alloy is impregnated into the pores, and a thermal conductivity is more than or equal to 40 W/m/K and a radial crushing strength is more than or equal to 300 MPa.

2. The composite for a wear-resistant ring according to claim 1, wherein, in addition to the thermal conductivity and the radial crushing strength, a linear expansion coefficient from room temperature to 300 C. is 13.6 to 16.910.sup.6/K, and a boundary strength with respect to the aluminum alloy is higher than or equal to 1.5 times a boundary strength with respect to an aluminum alloy of a composite formed by insert-casting a wear-resistant ring made of Ni-resist cast iron subjected to aluminum plating treatment in the aluminum alloy.

3. The composite for a wear-resistant ring according to claim 1, wherein the structure of the iron-based sintered compact for a wear-resistant ring is a structure in which, in addition to the free Cu phase, dispersion particles containing Mo or Si are further dispersed in the matrix at a total of 2% by mass or less.

4. The composite for a wear-resistant ring according to claim 2, wherein the structure of the iron-based sintered compact for a wear-resistant ring is a structure in which, in addition to the free Cu phase, dispersion particles containing Mo or Si are further dispersed in the matrix at a total of 2% by mass or less.

Description

EXAMPLES

[0067] Cu powder, graphite powder, or further powder for dispersion particles of types shown in Table 1 were blended into pure iron powder adjusted as iron-based powder in particle size distribution in which particles passed through a 60-mesh sieve and did not pass through a 350-mesh sieve at a blending amount (% by mass) shown in Table 1, and lubricant particle powder was further blended at a blending amount (parts by mass) shown in Table 1 and was mixed into mixed powder by a mixer. An average particle diameter of the graphite powder, the Cu powder, the powder for dispersion particles was set to 150 m or less.

[0068] The obtained mixed powder was charged into a mold, and was formed into a compact having a ring shape (outer diameter 90 mminner diameter 60 mmthickness 5 mm) by a forming press. Next, the obtained compact was subjected to sintering treatment, and was formed into an iron-based sintered compact for a wear-resistant ring. The sintering treatment was conducted in a nitrogen gas atmosphere at a temperature ranging from 1000 to 1200 C.

[0069] A test piece was taken from the obtained iron-based sintered compact for a wear-resistant ring, a composition and porosity of the sintered compact were measured to observe a structure. The porosity was converted from a density measured by an Archimedes method. It was checked whether existing pores were continuous pores. The sintered compact was immersed in liquid was or the like for 60 minutes, caused the wax or the like to permeate the sintered compact, and was converted from a variation in weight before and after the permeation. That variation was obtained and set to an amount of the continuous pores. A value defined by a formula as follows was calculated:

Ratio of amount of continuous pores (={(Amount of continuous pores)/(Amount of all pores)}100%)

[0070] It was evaluated that a case in which the ratio exceeds 50 was the continuous pores. Here, a total amount of the pores was converted from the density obtained the Archimedes method.

[0071] For the structure, the test piece for observing the structure was taken from the iron-based sintered compact, a cross section thereof in a pressing direction was polished and etched (an etchant: a natal solution), and identification of a matrix phase structure and the presence or absence of the free Cu phase and the dispersion particles were observed by an optical microscope. Further, amounts of dispersion of the free Cu phase and the dispersion particles were measured. For the amounts of dispersion, an area ratio between the free Cu phase and the dispersion particles was measured by a surface analysis using EPMA, and was converted into an area ratio with respect to the entire matrix phase. In regard to the dispersion particles, the amount of dispersion was further converted from the obtained area ratio with respect to the entire matrix phase into the mass % with respect to the total amount of the sintered compact.

[0072] The obtained results are shown in Table 2.

[0073] Any of the iron-based sintered compacts used in the examples of the present invention is the sintered compact that has a composition that contains C of 0.4 to 1.5% and Cu of 20 to 40% and a structure in which the matrix is a pearlite matrix and the free Cu phase or further the dispersion particles are dispersed in the matrix, and that has the continuous pores at a porosity of 15 to 50%. Meanwhile, comparative examples are sintered compacts in which C and/or Cu is out of the scope of the present invention, and the matrix is a pearlite matrix containing ferrite or cementite, the free Cu phase is not dispersed in the matrix, the porosity deviates from the scope of the present invention or does not become the continuous pores, or the dispersion particles deviate from the scope of the present invention.

[0074] In regard to the sintered compacts (Nos. 25 to 29) in which the dispersion particles containing Mo or Si are dispersed, amounts of Mo and Si are not given to the column of the chemical component of the sintered compact. It goes without saying that the sintered compact contains the amount of Mo or the amount of Si corresponding to the amount of dispersion of the dispersion particles.

[0075] Next, the obtained iron-based sintered compact for a wear-resistant ring was mounted at a predetermined position in the mold for forming the aluminum alloy member, and a melt of the aluminum alloy (having the composition of JIS AC8A) was injected into the mold under high pressure by die casting, so that the composite for a wear-resistant ring in which the iron-based sintered compact for a wear-resistant ring is insert-cast was obtained. When the porosity was low, the aluminum alloy cannot be sufficiently impregnated, and the composite cannot be obtained.

[0076] A test piece was taken from the obtained composite for a wear-resistant ring, and the thermal conductivity, the linear expansion, the radial crushing strength, and the boundary strength were measured. A test method is as follows.

[0077] (1) Measurement of Thermal Conductivity

[0078] A test piece (size: (10 mmthickness 3 mm) for measuring the thermal conductivity was taken from the obtained composite for a wear-resistant ring, and the thermal conductivity was measured at room temperature by a laser flash method.

[0079] (2) Measurement of Linear Expansion

[0080] A linear expansion test piece (size: 2 mm2 mmlength 20 mm) was taken from the obtained composite for a wear-resistant ring, and the linear expansion was measured from room temperature to 300 C. by a linear expansion measuring device, and an average linear expansion coefficient between room temperature and 300 C. was obtained.

[0081] (3) Measurement of Radial Crushing Strength

[0082] A test piece (outer diameter 85 mminner diameter 4.65 mmthickness 4 mm) for measuring the radial crushing strength was taken from the obtained composite for a wear-resistant ring, a radial crushing strength test was carried out in conformity with the regulation of JIS Z 2507, and the radial crushing strength of the composite was measured.

[0083] (4) Measurement of Boundary Strength (Bonding Strength)

[0084] A tensile test piece (size: 8 mm3 mmlength 10 mm) containing a bonding boundary between the aluminum alloy and the composite was taken from the obtained composite for a wear-resistant ring, a tension test was carried out, and the boundary strength (bonding strength) was obtained. A direction in which the tensile test piece was taken was set to a direction containing an interface at a right angle to an axis of the test piece. The boundary strength was evaluated by the ratio to the boundary strength .sub.E (boundary strength ratio), /.sub.E, when the wear-resistant ring made of Ni-resist cast iron subjected to aluminum plating treatment (Al-fin treatment) was insert-cast in the aluminum alloy. .sub.E was 30 MPa.

[0085] The obtained results are shown in Table 2 together.

TABLE-US-00001 TABLE 1 Mixed powder Powder for Iron-based dispersion powder* Graphite powder Cu powder particles Type*: Blending Blending Blending Type**: Blending Lubricant particle powder Mixed powder amount amount amount amount Blending amount**** No. (% by mass) (% by mass) (% by mass) (% by mass) Type*** (parts by mass) Remarks 1 A: 99.0 1.0 a 1.0 Comparative example 2 A: 95.0 1.0 4 a 1.0 Comparative example 3 A: 95.5 0.5 4 a 1.0 Comparative example 4 A: 89.0 1.0 10 a 1.0 Comparative example 5 A: 79.0 1.0 20 a 1.0 Preferred example 6 A: 78.5 1.5 20 a 1.0 Preferred example 7 A: 74.0 1.0 25 a 1.0 Preferred example 8 A: 69.0 1.0 30 a 1.0 Preferred example 9 A: 64.1 0.9 35 a 1.0 Preferred example 10 A: 59.2 0.8 40 a 1.0 Preferred example 11 A: 59.7 0.3 40 a 1.0 Comparative example 12 A: 59.5 0.5 40 a 1.0 Preferred example 13 A: 54.3 0.7 45 a 1.0 Comparative example 14 A: 69.2 0.8 30 a 1.0 Preferred example 15 A: 68.3 1.7 30 a 1.0 Comparative example 16 A: 67.0 1.0 30 w: 2.0 a 1.0 Preferred example 17 A: 67.5 1.0 30 x: 1.5 a 1.0 Preferred example 18 A: 66.0 1.0 30 x: 3.0 a 1.0 Comparative example 19 A: 68.0 1.0 30 y: 1.0 a 1.0 Preferred example 20 A: 68.0 1.0 30 z: 1.0 a 1.0 Preferred example *A: Pure iron powder **w: Mo powder, x: 60% FeMo powder, y: 45% FeSi powder, z: SiC powder ***a: Zinc stearate powder ****(iron-based powder + powder for dispersion particles + Cu powder + graphite powder): 100 parts by mass

TABLE-US-00002 TABLE 2 Sintered compact Composite Composition Linear Free Cu Dispersion Heat expansion Porosity phase particle Radial conductivity Linear Sintered Mixed Chemical component (% Porosity Amount of Amount of crushing Thermal expansion Boundary Composite compact powder by mass) (% by Continuous Matrix dispersion dispersion strength conductivity coefficient strength No. No. No. C Cu Balance volume) pore* phase** (% by area) (% by mass) (MPa) (W/m/K) (K.sup.1) ratio*** Remarks 1 1 1 1.0 Fe 34 P 360 27 11.7 0.9 Comparative example 2 2 2 1.0 4 Fe 33 P 380 30 11.8 1.1 Comparative example 3 3 3 0.5 4 Fe 35 P + F 1 260 29 11.9 1.0 Comparative example 4 4 4 1.0 10 Fe 29 P 8 408 37 12.5 1.4 Comparative example 5 5 5 1.0 20 Fe 22 P 18 376 41 13.6 1.7 Example 6 6 6 1.5 20 Fe 22 P 18 365 42 13.8 1.8 Example 7 7 7 1.0 25 Fe 32 P 22 326 46 14.3 2.8 Example 8 8 7 1.0 25 Fe 27 P 23 424 47 14.6 2.2 Example 9 9 8 1.0 30 Fe 31 P 27 340 47 14.7 3.0 Example 10 10 8 1.0 30 Fe 26 P 28 444 54 15.1 2.4 Example 11 11 8 1.0 30 Fe 14 X P 28 Cannot be formed into composite Comparative example 12 12 8 1.0 30 Fe 41 P 28 311 44 16.1 3.2 Example 13 11 8 1.0 30 Fe 53 P 27 240 40 16.3 3.3 Comparative example 14 14 8 1.0 30 Fe 10 X P 28 Cannot be formed into composite Comparative example 15 15 9 0.9 35 Fe 30 P 33 353 51 15.1 3.1 Example 16 16 9 0.9 35 Fe 25 P 32 440 54 15.0 2.6 Example 17 17 9 0.9 35 Fe 20 P 33 525 55 14.5 1.8 Example 18 18 10 0.8 40 Fe 31 P 38 310 60 15.3 3.1 Example 19 19 10 0.8 40 Fe 45 P 37 301 50 16.5 3.2 Example 20 20 11 0.3 40 Fe 35 P + F 37 270 43 15.0 3.3 Comparative example 21 21 12 0.5 40 Fe 30 P 38 305 52 15.3 2.9 Example 22 22 13 0.7 45 Fe 35 P 42 180 62 15.9 3.1 Comparative example 23 23 14 0.8 30 Fe 31 P 26 330 47 14.7 2.9 Example 24 24 15 1.7 30 Fe 31 P + C 28 295 42 14.2 2.7 Comparative example 25 25 16 1.0 30 Fe 30 P 25 1.9 370 51 14.2 2.2 Example 26 26 17 1.0 30 Fe 31 P 26 1.5 330 48 14.3 1.9 Example 27 27 18 1.0 30 Fe 31 P 24 3.0 310 49 14.2 1.4 Comparative example 28 28 19 1.0 30 Fe 31 P 27 0.9 325 48 14.1 1.7 Example 29 29 20 1.5 30 Fe 31 P 26 1.0 316 48 14.0 1.6 Example *: When a rate of continuous pores exceeds 50%, X: The others **P: Pearlite, C: Cementite, F: Ferrite ***Boundary strength/Boundary strength when Ni-resist cast iron subjected to aluminum plating treatment is insert-cast

[0086] Any of the examples of the present invention becomes the composite for a wear-resistant ring in which the aluminum alloy is impregnated into the pores, the radial crushing strength is more than or equal to 300 MPa, and the thermal conductivity is more than or equal to 40 W/m/K, and which has excellent heat conductivity. In the examples of the present invention, in comparison with the conventional wear-resistant ring made of Ni-resist cast iron, the heat conductivity is improved about twice or more (the thermal conductivity of the Ni-resist cast iron material is about 20 W/m/K). Each of the examples of the present invention becomes an excellent composite for a wear-resistant ring in which the linear expansion coefficient is in a range of 13.6 to 16.910.sup.6/K, and the boundary strength (the bonding strength) with respect to the aluminum alloy is high and is more than or equal to 1.5 times the boundary strength (the bonding strength) with respect to the aluminum alloy the composite obtained by insert-casting the wear-resistant ring made of Ni-resist cast iron.

[0087] Meanwhile, the comparative examples deviating from the scope of the present invention become composites cannot secure desired characteristics because the radial crushing strength does not satisfy a desired value, the thermal conductivity is lower than a predetermined value, and the heat conductivity is reduced, the boundary strength is reduced when the boundary strength with respect to the aluminum alloy is less than 1.5 times the boundary strength when the wear-resistant ring made of Ni-resist cast iron is insert-cast in the aluminum alloy, or the linear expansion coefficient is less than 13.610.sup.6/K.