MIXED POWDER FOR IRON-BASED POWDER METALLURGY AND SINTERED BODY PRODUCED USING SAME

Abstract

The mixed powder for iron-based powder metallurgy of the present invention comprises: at least one ternary oxide selected from the group consisting of CaAlSi oxides and CaMgSi oxides, and at least one binary oxide selected from the group consisting of CaAl oxides and CaSi oxides. The ternary oxide and the binary oxide are contained in a sum weight of 0.025 wt % or more to 0.3 wt % or less.

Claims

1. A mixed powder, comprising at least one ternary oxide selected from the group consisting of CaAlSi oxides and CaMgSi oxides, and at least one binary oxide selected from the group consisting of CaAl oxides and CaSi oxides, wherein the ternary oxide and the binary oxide are contained in a sum weight of 0.025 wt % or more to 0.3 wt % or less.

2. The mixed powder according to claim 1, wherein the ternary oxide and the binary oxide are contained at a weight ratio of 9:1 to 1:9.

3. The mixed powder according to claim 1, wherein the ternary oxide and the binary oxide are contained in a sum weight of 0.05 wt % or more to 0.2 wt % or less.

4. The mixed powder according to claim 1, wherein the binary oxide is at least one selected from the group consisting of CaO.Al.sub.2O.sub.3, 2CaO.SiO.sub.2, and 12CaO.7Al.sub.2O.sub.3.

5. The mixed powder according to claim 1, wherein the ternary oxide is at least one selected from the group consisting of 2CaO.MgO.2SiO.sub.2 and 2CaO.Al.sub.2O.sub.3.SiO.sub.2.

6. A sintered body prepared by sintering the mixed powder according to claim 1.

Description

EXAMPLES

[0063] Hereafter, the present invention will be described in further detail by way of Examples; however, the present invention is not limited to these.

Examples 1 to 6 and Comparative Examples 1 to 6

[0064] In each Example and in each Comparative Example, a pure iron powder (trade name: ATOMEL 300M (manufactured by Kobe Steel, Ltd.)) was mixed with 2 wt % of copper powder (trade name: CuATW-250 (manufactured by Fukuda Metal Foil & Powder Co., Ltd.)), a binary oxide and/or a ternary oxide having a composition in wt % shown in the section of binary oxide and/or ternary oxide in Table 1, graphite powder (trade name: CPB (manufactured by Nippon Graphite Industries, Co., Ltd.)), and 0.75 wt % of zinc stearate, so as to prepare a mixed powder for iron-based powder metallurgy. The graphite powder was added at an amount such that the amount of carbon after the sintering would be 0.75 wt %. For both of the binary oxide and the ternary oxide, those having a volume-average particle size of 2 m were used.

[0065] The above mixed powder for iron-based powder metallurgy was put into a mold, and a test piece was molded so as to have a ring shape with an outer diameter of 64 mm, an inner diameter of 24 mm, and a thickness of 20 mm and to have a molding density of 7.00 g/cm.sup.3. Next, this test piece having a ring shape was sintered at 1130 C. for 30 minutes in a 10 vol % H.sub.2N.sub.2 atmosphere, so as to prepare a sintered body.

[0066] The sintered body thus prepared was turned on a lathe by using a cermet tip (ISO type number: SNGN120408 non-breaker) under conditions with a circumferential speed of 160 m/min, a cutting rate of 0.5 mm/pass, and a feed rate of 0.1 min/rev, and with a dry type, so as to measure a tool wear amount of the cutting tool. For the tool wear amount, a wear amount (m) of the cutting tool after the sintered body was cut for 330 m from the start of cutting and a wear amount (um) of the cutting tool after the sintered body was cut for 1150 m from the start of cutting were measured with a tool microscope. The evaluation results of the wear amounts are shown in the section of tool wear amount in Table 1. The smaller the value of the wear amount is, the more excellent the machinability of the sintered body is.

TABLE-US-00001 TABLE 1 Examples Comparative Examples Composition 1 2 3 4 5 6 1 2 3 4 5 6 Ternary 2CaOMgO2SiO.sub.2 0.05 0.05 0.05 0.1 oxide 2CaOAl.sub.2O.sub.3SiO.sub.2 0.05 0.05 0.05 0.1 (wt %) Binary oxide CaOAl.sub.2O.sub.3 0.05 0.05 0.1 (wt %) 2CaOSiO.sub.2 0.05 0.05 0.1 12CaO7Al.sub.2O.sub.3 0.05 0.05 0.1 Sintered body density (g/cm.sup.3) 6.94 6.94 6.94 6.95 6.95 6.95 6.94 6.94 6.94 6.95 6.94 6.94 Radial crushing strength (MPa) 890 883 899 910 906 900 915 900 889 907 904 901 Tool wear Cutting distance 19.4 20.6 21.2 18.3 18.4 19.6 89.4 22.1 26.4 24.1 23.4 21.1 amount (330 m) (m) Cutting distance 58.4 60.1 60.7 45.2 44.5 50.2 253.0 83.8 69.6 58.5 86.8 90.2 (1150 m)

[0067] In Table 1, the sintered body density was a value as determined by making measurements in accordance with Japan Powder Metallurgy Association Standard (JPMA M 01). The radial crushing strength was a value as determined by making measurements in accordance with JIS Z 2507-2000. The higher the radial crushing strength is, the less likely the sintered body is broken, so that the sintered body has a higher strength.

[0068] Referring to Table 1, Examples 1 to 6 are each a sintered body containing a binary oxide and a ternary oxide in combination. Comparative Example 1 is a sintered body containing neither a binary oxide nor a ternary oxide. Comparative Examples 3 and 4 are each a sintered body containing a ternary oxide alone. Comparative Examples 2, 5 and 6 are each a sintered body containing a binary oxide alone. In Comparative Example 2, a component disclosed in Patent Literature 1 (CaO.Al.sub.2O.sub.3) is used. In Comparative Example 3, a component disclosed in Patent Literature 3 (2CaO.MgO.2SiO.sub.2) is used. In Comparative Example 4, a component disclosed in Patent Literature 4 (2CaO.Al.sub.2O.sub.3.SiO.sub.2) is used.

[0069] With respect to the sintered bodies of Examples 1 to 6, it has been made clear that the tool wear amount can be considerably reduced both in cutting for 330 m (initial wear) and in cutting for 1150 m (long-time wear), as compared with those of Comparative Examples 1 to 6. The reason therefor probably seems to be that the binary oxide improves the machinability at an initial stage of cutting and the ternary oxide improves the machinability in cutting for a long period of time, so that these effects are combined to enhance the machinability of the sintered body both at an initial stage of cutting and in cutting for a long period of time.

[0070] When Comparative Example 1 is compared with Comparative Examples 2, 5, and 6, it will be understood that the addition of a binary oxide produces an effect of suppressing the initial wear of the cutting tool. Further, when Comparative Example 1 is compared with Comparative Examples 3 and 4, it will be understood that the addition of a ternary oxide produces an effect of suppressing the wear of the cutting tool in cutting for a long period of time.

[0071] From the results of the Examples and the Comparative Examples shown in Table 1, it has been made clear that, when the binary oxide and the ternary oxide are contained in a sum weight of 0.1 wt %, a sintered body that can be easily machined both at an initial stage of cutting and in cutting for a long period of time can be obtained, thereby showing the effect of the present invention.

Examples 7 to 18

[0072] In Examples 7 to 18, a mixed powder for iron-based powder metallurgy and a sintered body were prepared in the same manner as in Example 1 except that the sum weight of the binary oxide and the ternary oxide was fixed to 0.1 wt % and that the weight ratio and the composition thereof were changed to the composition and wt % shown in the sections of binary oxide and ternary oxide in Table 2. On the sintered body thus prepared, evaluation of the tool wear amount was made by the same method as in Example 1. The results of these are shown in the following Table 2.

TABLE-US-00002 TABLE 2 Examples Composition 7 8 9 10 11 12 13 14 15 16 17 18 Ternary oxide 2CaOMgO2SiO.sub.2 (wt %) 2CaOAl.sub.2O.sub.3SiO.sub.2 0.09 0.08 0.03 0.01 0.09 0.08 0.03 0.01 0.09 0.08 0.03 0.01 Binary oxide CaOAl.sub.2O.sub.3 0.01 0.02 0.07 0.09 (wt %) 2CaOSiO.sub.2 0.01 0.02 0.07 0.09 12CaO7Al.sub.2O.sub.3 0.01 0.02 0.07 0.09 Tool wear Cutting distance 20.4 20.1 19.6 23.2 20.3 18.7 18.4 23.8 23.6 22.5 21.3 23.0 amount (330 m) (m) Cutting distance 54.3 48.3 54.5 80.9 50.1 43.3 52.1 78.8 52.3 48.8 53.6 87.4 (1150 m)

[0073] From the results shown in Table 2, it has been made clear that, when the ternary oxide and the binary oxide are contained at a weight ratio of 9:1 to 1:9, the machinability at an initial stage of cutting and the machinability in cutting for a long period of time are compatible with each other. In particular, when the weight ratio is 9:1 to 3:7, the machinability at an initial stage of cutting and the machinability in cutting for a long period of time are highly compatible with each other.

Examples 19 to 21 and Comparative Examples 7 to 9

[0074] In Examples 19 to 21 and Comparative Examples 7 to 9, a mixed powder for iron-based powder metallurgy and a sintered body were prepared in the same manner as in Example 1 except that the weights of the binary oxide and the ternary oxide were changed to the composition and wt % shown in the sections of binary oxide and ternary oxide in Table 3. On the sintered body thus prepared, evaluation of the wear amount was made by the same method as in Example 1. The results of these are shown in the following Table 3.

TABLE-US-00003 TABLE 3 Examples Comparative Examples Composition 19 20 21 7 8 9 Ternary oxide (wt %) 2CaOAl.sub.2O.sub.3SiO.sub.2 0.025 0.10 0.15 0.005 0.01 0.20 Binary oxide (wt %) CaOAl.sub.2O.sub.3 0.025 0.10 0.15 0.005 0.01 0.20 Sum content of oxides (wt %) 0.05 0.20 0.3 0.01 0.02 0.40 Radial crushing strength (MPa) 913 840 802 916 915 720 Tool wear amount Cutting distance (330 m) 20.2 16.1 15.4 26.7 25.3 14.4 (m) Cutting distance (1150 m) 56.4 40.4 37.9 204 103.3 36.6

[0075] From the results shown in Table 3, it has been made clear that, when a sum content of the binary oxide and the ternary oxide is 0.025 wt % or more to 0.3 wt % or less, the machinability at an initial stage of cutting and the machinability in cutting for a long period of time are compatible with each other, thereby showing the effect of the present invention. On the other hand, it has been made clear that, when a sum weight % of the binary oxide and the ternary oxide is less than 0.025 wt % (Comparative Examples 7 and 8), the effect of improving the machinability cannot be sufficiently obtained, and that, when a sum weight of the binary oxide and the ternary oxide exceeds 0.3 wt % (Comparative Example 9), the radial crushing strength is lower than 800 MPa, thereby giving an insufficient strength of the sintered body.