JPH0459362B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a low-alloy iron powder for sintering, which is a high-density, high-strength sintered material that is applied to structural machine parts and the like. (Prior art) In general, there is a desire to increase the strength of iron-based sintered materials, which are often used as machine component materials, and in response to this, various strengthening methods such as alloying, densification, and homogenization are used to increase the strength. Sintered materials with excellent properties are being developed. For example, as a method of achieving high strength of materials by alloying (hereinafter referred to as alloying strengthening method), powders of alloying elements such as copper (Cu), nickel (Ni), manganese (Mn), and chromium (Cr) are individually In addition, there are mixing methods in which iron powder is mixed with
A pre-alloying method using a pre-alloyed powder that is pre-alloyed with Mn, Cr, etc.) is used. In addition, as a method for strengthening densification, 2press−
2sinter method, sinter forging method (P/F), etc. are used. Furthermore, as a homogenization strengthening method, a homogenization method is used in which high temperature sintering is performed when sintering a sintered material. In addition to the above, strengthening measures such as the spheroidization method, which spheroidizes the pores of structural mechanical parts, are known. However, although all of the above-mentioned various strengthening methods are effective in strengthening the sintered material, each method includes some problems. In other words, 2press− as a densification strengthening method
In the 2sinter method, sinter forging method (P/F), etc.
High density of structural mechanical parts, etc. is achieved by changing or adding to the manufacturing process and performing strong processing such as compression, so it is necessary to manage atmosphere management, temperature settings, etc. when performing strong processing. This has led to the problem that the number of steps has increased, making the manufacturing process complicated, and thus manufacturing costs have increased significantly. In addition, in the mixed method among alloying strengthening methods,
There is a problem in that it takes a long time to sufficiently diffuse the added alloying elements into iron (Fe).
Additionally, active metals such as chromium (Cr) and manganese (Mn) have the problem of oxidizing and preventing diffusion unless the sintering atmosphere is strictly controlled. Furthermore, even in the prealloying method, alloying increases the hardness of the powder and reduces compression moldability, thus preventing higher density of structural mechanical parts. By the way, various proposals have been made to solve the problem of deterioration in compression formability in the prealloying method, such as "method for producing low alloy powdered iron".
(Japanese Patent Publication No. 45-9649) proposes to improve compression moldability by attaching alloying elements to the surface of iron powder by a special reduction method. (Problems to be Solved by the Invention) However, although the above-mentioned conventional method for manufacturing low-alloy powder iron has improved compression formability, the price of the powder itself is lower than that of commercially available low-alloy steel powder. It is quite expensive, and raw material costs account for a high proportion of the manufacturing cost, which has been a major obstacle when forming structural mechanical parts using sintered materials. (Means for Solving the Problems) The present invention has been made in view of the above-mentioned circumstances to overcome the problems. The purpose is to provide low alloy iron powder for sintering. A feature of the present invention for achieving the above object is that molybdenum (Mo) is contained in the low alloy iron powder in a weight percentage.
Contains 0.2 to 2.0% of carbon (C), 0.05% or less of carbon (C), and 0.2% or less of oxygen (O), as well as silicon (Si),
The total content of chromium (Cr), copper (Cu), and nickel (Ni) is suppressed to 0.2% or less, and the remainder, which includes unavoidable impurities, is substantially composed of iron (Fe). (Function) In the low-alloy iron powder for sintering according to the present invention configured as described above, molybdenum (Mo) is contained in the iron (Fe) powder because molybdenum (Mo) is compressed when prealloyed. Without losing moldability,
This is also because sufficient hardenability can be ensured. However, if molybdenum (Mo) is less than 0.2%, the mechanical properties after heat treatment will deteriorate;
%, compression moldability tends to deteriorate and strength after heat treatment tends not to improve in spite of the addition of Mo. Furthermore, silicon (Si), chromium (Cr), copper (Cu)
and nickel (Ni) with a total content of 0.2
% or less because each of the metal elements has the effect of lowering compression moldability.
Other unavoidable impurities include P, S, Mn, etc. Further, if carbon (C) exceeds 0.05% and oxygen exceeds 0.2%, the compression moldability of the alloy will be significantly deteriorated, so the respective weight percentages are suppressed to the above-mentioned weight percentages, which work effectively to improve the compression moldability. As described above, since the metal element is contained in the iron (Fe) powder at the above weight percentage, it is possible to provide a low-alloy powder for sintering that has high compression moldability and excellent hardenability at a low cost. Can be done. (Example) Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 A molten metal adjusted to a target composition is prepared in a melting furnace, and after this molten metal is flowed out from a tundish, high-pressure water is sprayed onto the flowed out molten metal to make it powder (hereinafter referred to as water spray method). The powder formed by the water spray method was heated at 900 °C in an atmosphere of decomposed ammonia.
After reduction treatment for 60 minutes at °C, pulverize, and then
It was classified using an 80mesh sieve to obtain -80mesh powder. The composition of this powder is as shown in the relevant column of Table 1: iron (Fe) and molybdenum (Mo) 0.3%, oxygen (O) 0.08%, carbon (C) 0.02%, silicon (Si) + chromium ( Cr) + copper (Cu) + nickel (Ni) in various weight percentages of 0.2% or less. We decided to conduct a test to obtain the compression moldability value for the above-mentioned -80mesh powder.
The test was conducted in accordance with 64 (Metal Powder Compressibility Test Method). Tests were conducted on these three levels using molding pressures of 3t, 5t, and 7t per square centimeter, and the results were 6.22g/cm ³ , 6.87g/cm ³ , and 7.21g, respectively, as shown in Table 2. g/cm ³ , and the density of the compact at a molding pressure of 7 t/cm ² is shown in FIG. Next, to measure the tensile strength after heat treatment
A tensile test was conducted using a tensile test piece of sintered metal JSPM2-64. This tensile test piece was prepared by mixing the powder shown in Table 1 with 0.5% graphite powder and 0.8% lubricant, and then molding the mixture to a compact density of approximately 7.0 g/cm ³ in a decomposed ammonia atmosphere. Inside
This sintered body was sintered at 1200℃ for 40 minutes.
It was heat treated at 870°C for 30 minutes, cooled by soaking in an oil quenching fluid to prevent quench cracking and thermal distortion, and then tempered at 170°C for 90 minutes. The tensile test was conducted at a crosshead speed of 2 mm/min. The results are shown in FIG. 2, and in this example, a strength of 97 Kgf/mm ² was obtained. Table 1 also shows the compositions of the powders of Examples 2 to 4 and Comparative Examples 1 to 4, and Table 2 also shows the compact density of each of the above examples against the molding pressure under each condition. ing. In addition, Figure 1 graphically shows the characteristics of the compact density at a molding pressure of 7t/cm ² not only for Example 1 but also for each of the above examples, and Figure 2 shows the tensile strength of each example after heat treatment. A comparison graph is also shown. Example 2 A powder formed by a water spray method was used in Example 1.

【table】

【table】

[Table] After carrying out ring treatment and classification in the same manner as in [Table], molybdenum (Mo) was 0.6% and oxygen (O) was 0.08% by weight.
%, carbon (C) by 0.02%, and silicon (Si) + chromium (Cr) + copper (Cu) + nickel (Ni) by 0.2% or less, respectively. Compression moldability and tensile strength tests were conducted on the low alloy iron powder having the above composition. As shown in Table 2, the compression moldability was 6.20 g/cm ³ , 6.85 g/cm ³ , and 7.19 g/cm ³ at molding pressures of 3 t/cm ² , 5 t/cm ² , and 7 t/cm ² , respectively. The tensile strength of the test piece after heat treatment was 105 Kgf/mm ² as shown in FIG. 2. Example 3 Powder formed by the water spray method in the same manner as in the above two examples was subjected to ring treatment and classification treatment, and the weight percentage of molybdenum (Mo) in iron (Fe) was 1.0%, oxygen (O) was 0.07%, 0.01% carbon (C), silicon (Si)
+ Chromium (Cr) + Copper (Cu) + Nickel (Ni) by 0.2
% or less of each was obtained. A test was conducted under the same conditions and method as in Examples 1 and 2 to examine the compression moldability and tensile strength of this low alloy iron powder. The result is 7.17g/cm ³ at 7t/cm ²
The compact density was 110 Kgf/mm ² and the tensile strength was 110 Kgf/mm 2 . Example 4 Similar to Examples 1 to 3, the powder formed by the water spray method was subjected to reduction treatment and classification treatment, and molybdenum (Mo) was added to iron (Fe) at a weight percentage of 1.5.
%, oxygen (O) 0.08%, carbon (C) 0.02%,
A low alloy iron powder containing 0.2% or less of silicon (Si), chromium (Cr), copper (Cu), and nickel (Ni) was obtained. Using this low alloy iron powder, compression moldability and tensile strength tests were conducted in the same manner as in Examples 1 to 3 above, and the compact density was 7.14 g/cm ³ at 7 t/cm ² and 112 Kgf/mm ² respectively. Tensile strength values were obtained. Comparative Example 1 Comparative Example 1 is a typical commercially available low-alloy iron powder produced by an oil spray method. The oil spray method uses oil as the spray medium, which suppresses oxidation during powdering and produces powder with low oxygen (O) + carbon (C) content, which has excellent compressibility. Removal is costly. Chemical analysis of this powder revealed that it contained 0.23% molybdenum (Mo) and chromium (Cr) in iron (Fe).
It was found that it contained 0.95% manganese (Mn) and 0.76% manganese (Mn). As a result of testing Comparative Example 1 under the same conditions as in each of the examples above, the compression moldability was 7.15 g/cm ³ at 7t/cm ² , but the tensile strength of the test piece after heat treatment was 7.15 g/cm 3 . It was not as good as any of the examples. Comparative Example 2 Comparative Example 2 is a commercially available low alloy powder formed by a water spray method, and its composition is as shown in Table 1, with a weight percentage of 0.52% molybdenum (Mo) and 0.16% manganese (Mn). , 1.79% Nickel (Ni)
Contains each. The total amount of reinforcing elements nickel (Ni) and manganese (Mn) is 1.95%, which is the highest in each example, so the density of the compact, which indicates compression moldability, does not show a very high value, but the tensile strength of the heat-treated product It has the highest tensile strength of 103 Kgf/mm ² among the comparative examples. Comparative Example 3 This example uses a ferroalloy powder prepared by pre-alloying molybdenum (Mo) and copper (Cu).
Molybdenum (Mo) is expressed as a percentage by weight.
0.6%, copper (Cu) 0.4%, silicon (Si) 0.01%,
It is a low alloy iron powder containing 0.01% carbon (C) and 0.08% oxygen (O). Using this low alloy iron powder, compression moldability and tensile strength tests were conducted in the same manner as in the above examples, and it was found that the addition of copper (Cu) significantly reduced the compression moldability. It was also found that the tensile strength was not as good as any of the examples. Comparative Example 4 In Comparative Example 4, the composition of the low alloy iron powder is expressed as a weight percentage of iron (Fe), and molybdenum (Mo) is 0.6%,
0.5% chromium (Cr), 0.13% manganese (Mn)
%, containing 0.12% oxygen (O) and 0.01% carbon (C). When this low-alloy iron powder was subjected to compression moldability and tensile strength tests, it was found that because molybdenum (Mo) and chromium (Cr) were added, the tensile strength of the comparative example was similar to that of comparative example 3, as shown in Figure 2. 2 and each example, but
As shown in Table 2 and FIG. 1, the density of the compact, which indicates compression moldability, was not very high, indicating that the compression moldability was extremely low. Comparative Examples 5 to 8 As shown in Table 1, Comparative Examples 5 to 8 have a basic composition similar to that of Example 3, but have low molybdenum (Comparative Example 5), high molybdenum (Comparative Example 6), and High oxygen (Comparative Example 7) and high carbon (Comparative Example 8) were produced by subjecting the powder formed by the water spray method to reduction treatment and classification treatment in the same manner as in each of the above Examples. JSPM as in the example
It was subjected to compression moldability and tensile strength tests according to Standard 1-64 and JSPM Standard 2-64. From the results of the compression moldability test shown in Table 2 and the results of the tensile test shown in FIG. 2, it can be seen that although Comparative Example 5 with low molybdenum (Mo) has better compression moldability than each of the Examples, Comparative Example 6 with high molybdenum (Mo) has low tensile strength and high tensile strength, but
Compression moldability is poor, and Comparative Example 7 with high oxygen (O) is inferior in both compression moldability and tensile strength, and Comparative Example 8 with high carbon (C) is significantly inferior in compression moldability and tensile strength, both of which are satisfactory. It turned out that it was not possible to obtain the desired performance. From the above results, even when structural mechanical parts are formed using the low alloy iron powder for sintering according to the present invention, it has excellent compression moldability and also has tensile strength as a mechanical property, so it can be commercially available. It has been found that not only is it comparable to those using expensive low-alloy iron powder for sintering as a raw material, but by adjusting the content to a suitable level, it is possible to achieve better results than commercially available products. . (Effects of the Invention) As described above in detail, the low alloy iron powder for sintering according to the present invention provides the following effects. 0.2 to 2.0% by weight of molybdenum (Mo) and carbon (C) in a powder consisting essentially of iron (Fe)
Machine component parts contain 0.05% or less, oxygen (O) 0.2% or less, and the total content of silicon (Si), chromium (Cr), copper (Cu), and nickel (Ni) is suppressed to 0.2% or less. When used as a raw material for
It has excellent compressibility at the same molding pressure and also has excellent strength when made into molded parts.Moreover, it can be manufactured using an inexpensive manufacturing method called water spraying, reducing the proportion of raw materials in manufacturing costs. It is possible to provide an inexpensive low-alloy iron powder for sintering.

[Brief explanation of the drawing]

Figures 1 and ² are for explaining the low-alloy iron powder for sintering according to the present invention. FIG. 4 is a characteristic diagram of tensile strength measured for Examples 1 to 4 and Comparative Examples 1 to 4, respectively.

Claims (1)

[Claims] 1 Molybdenum (Mo) in weight percentage from 0.2 to
2.0%, carbon (C) 0.05% or less, oxygen (O)
The total content of silicon (Si), chromium (Cr), copper (Cu), and nickel (Ni) is suppressed to 0.2% or less, and the remainder containing unavoidable impurities is substantially iron (Fe). ) Low alloy iron powder for sintering.