JPH1053802A - High carbon iron-base alloy powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a powder spheroidized so that diffusion and disappearance can be practically prevented at the time of powdering by means of water atomization, by setting ratio of manganese to silicon so that specific apparent density is obtained in a high carbon iron-base alloy powder. SOLUTION: This high carbon iron-base alloy powder is produced by powdering a molten iron-base alloy containing >=0.8wt.% carbon by water atomization. In this case, the ratio of manganese to silicon(Mn/Si) of the molten alloy is set at a value capable of giving >=3.0g/cm<3> apparent density (AD). It is preferable that this alloy powder has a composition cosisting of, by weight, 2.0-4.0% carbon, <=2.0% silicon, 0-25.0% nickel, 20.0-40.0% chromium, 10.0-40.0%, by tungsten equivalent, of molybdenum and tungsten, <=5.0% impurities, and the balance iron. Respective powder grains are spheroidized and minimal in diffusion during sintering and have excellent characteristics required for hard grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality powder suitable for hard particles mixed in order to improve the abrasion resistance and the like of a sintered product produced by compression-molding a powdered metal into a required shape. It relates to carbon iron alloy powder.

[0002]

2. Description of the Related Art For example, a valve seat of an automobile is manufactured by compressing and molding powder metal such as general steel powder in a container and then sintering. In order to compensate for this, high-carbon iron alloy powder is mixed as a hard particle at a required ratio to compensate for the low wear resistance.

[0003] The high carbon iron alloy powder is made into fine powder by spraying molten metal,
For example, by passing a stream of molten metal that falls by gravity to a focal position where water pressure fluid is injected and concentrated in an inverted cone shape, and finely pulverizing the molten metal, Carbon iron alloy powder is produced.

[0004]

When the high carbon iron alloy powder is pulverized by a water atomization method (water atomization method), as shown in the micrographs of FIGS. A whisker-like projection or a flat shape is formed on the powder particles. For this reason, during sintering, the hard particles tend to diffuse into the mixed general steel powder, and as a result, the hard particles disappear or are altered, and the function as the hard particles is lost. there were. In addition, this tendency increased as the powder of carbon (C) became higher.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks inherent in the prior art, and has been proposed to solve the problem in a favorable manner. It is an object of the present invention to provide a high carbon iron alloy powder having a simplified shape.

[0006]

In order to overcome the above-mentioned problems and achieve the intended object, the high carbon iron alloy powder according to the present invention contains at least 0.8% by weight of carbon (C), The manganese-silicon ratio (Mn / Si ratio) is set so that the density (AD) is 3.0 g / cm ³ or more.

[0007] In order to achieve the above object, a high carbon iron alloy powder according to another invention of the present application comprises carbon (C) 2.0
4.0% by weight, 2.0% by weight or less of silicon (Si), 0 to 25.0% by weight of nickel (Ni), 20.0 to 40.0% of chromium (Cr).
0% by weight, molybdenum (Mo) and tungsten (W) have impurities of 10.0 to 40.0% by weight or less and 5.0% by weight or less in terms of tungsten equivalent, and the apparent density (AD) of iron is 3 .
0 g / cm ³ or more and becomes as manganese - silicon ratio (Mn / Si
Ratio) is set.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a high carbon iron alloy powder according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments.

The inventor of the present invention has repeatedly conducted trials for a hard particle powder having a high compounding ratio of carbon (C), which is formed into a powder by a water spraying method, in order to obtain a powder having an excellent spherical shape. By setting the manganese-silicon ratio (Mn / Si ratio) so that AD) is 3.0 g / cm ³ or more, the above requirement can be met.

The hard high-carbon iron alloy powder according to the embodiment is obtained by pulverizing a molten iron alloy containing 0.8% by weight or more of carbon (C) by a water spray method. In this case, the manganese-silicon ratio (Mn / Si ratio) of the molten iron alloy is set to a value at which the apparent density (AD) becomes 3.0 g / cm ³ or more (see FIG. 3). Thus, in the high carbon iron alloy powder obtained by the water spraying method, as shown in the micrograph of FIG. 1, each powder particle is rounded and spherical. That is, as in the related art, a whisker-like projection is not formed on the powder particles, or the powder particles are flat and do not curl at the ends, so that diffusion during sintering is reduced, and characteristics excellent as hard particles are obtained. Incidentally, the apparent density (AD) of the hard high carbon iron alloy powder shown in the micrograph of FIG. 1 is 3.08 g / cm ³ .

It is known that, in a low carbon steel, as the manganese-silicon ratio (Mn / Si ratio) increases, the powder becomes spherical and the apparent density (AD) increases. The effect of the manganese-silicon ratio (Mn / Si ratio) on the apparent density (AD) of the present invention appears at 0.8% by weight or more of carbon (C) and is remarkable at 2.0% by weight or more. Also, excessive addition of carbon lowers the melting point of the alloy and impairs the above effects, so it is recommended that carbon (C) be less than 4.0% by weight. Furthermore, in order to minimize the effect of the increase in the oxygen concentration on the powder surface due to the water during spraying, it is preferable to make silicon (Si) 0.5% by weight or more and preferentially oxidize silicon (Si).

Here, for example, carbon (C) 2.0 to 4.0.
0 wt%, silicon (Si) 2.0 wt% or less, nickel (N
i) 0 to 25.0% by weight, chromium (Cr) 20.0 to 40.0% by weight, molybdenum (Mo) and tungsten (W) have a tungsten equivalent of 10.0 to 40.0% by weight or less; When powdering a molten alloy having a component ratio of 0% by weight or less by a water spray method, the manganese-silicon ratio (Mn / Si ratio) is adjusted so that the apparent density (AD) becomes 3.0 g / cm ³ or more. Also by setting, each powder particle is made into a spheroid to reduce the diffusion during sintering and to obtain characteristics excellent as hard particles.

Carbon (C) and chromium (Cr), molybdenum (M
o) In order to form a hard carbide by bonding with tungsten (W), iron (Fe), and silicon (Si), it is recommended that each component be added in the following ratio. About chrome (Cr)
20.0-40.0% by weight, preferably 32.0-40.0
% By weight. For tungsten (W) and molybdenum (Mo), the tungsten equivalent is 10.0 to 40.0% by weight, preferably molybdenum (Mo): 5.0 to 12.0% by weight, and tungsten (W): 10.0. ~ 16.0% by weight. (Tungsten equivalent = tungsten weight% + molybdenum weight% × 2) For silicon (Si), 2.0 wt% or less, preferably 0.5-1.5 wt% is added. It should be noted that nickel (Ni) diffuses into the sintering matrix during the sintering of the present alloy and improves the oxidation resistance and heat resistance of the matrix. Therefore, 0 to 25.0% by weight, preferably 17. 0 to 25.0% by weight is added. In addition, the same as vanadium (V), titanium (Ti), niobium (Nb), tantalum (Ta), zircon (Zr) carbide-forming elements, and nickel (Ni) added intentionally to improve the strength of carbides The austenite-forming elements of cobalt (Co) and copper (Cu), which improve heat resistance, even if containing 5.0% by weight or less as impurities, change the apparent density (AD) of the manganese-silicon ratio (Mn / Si ratio). Is not impaired, but the amount of heavy metal elements such as the inevitable impurity elements and rare earth elements other than the above mixed in the raw material of the iron alloy and the melting and spraying process is 1.0% by weight.
It is preferable to set the following.

[0014]

[Experimental Example] FIG. 3 is a graph showing the results of measuring the apparent density (AD) of the high carbon iron alloy powder obtained by pulverizing the molten metal having the component ratios shown in FIG. Was. FIG. 1 shows a micrograph of the high-carbon iron alloy powder having the above component ratio, and FIG. 4 shows a micrograph of the high-carbon iron alloy powder having the above component ratio.
From this micrograph, the apparent density (AD) is 3.08 g / cm ³
In the high carbon iron alloy powder, the powder particles are rounded and spherical, while the apparent density (AD) is 2.04.
g / cm ³ and 2.00 g / cm ³ of high carbon iron alloy powder, each powder particle has a whisker-like projection,
It turns out that it is flat and the end is curled. That is,
If the apparent density (AD) is 3.0 g / cm ³ or more, the powder particles are spherical, so that unnecessary diffusion during sintering due to beard-like projections and flattening can be prevented. is there. From the graph of FIG. 3, it was found that the manganese-silicon ratio (Mn / Si ratio) needs to be about 0.15 or less in order to make the apparent density (AD) 3.0 g / cm ³ or more. I do. As described above, the high carbon iron alloy powder whose manganese-silicon ratio (Mn / Si ratio) is set to about 0.15 or less and whose apparent density (AD) is 3.0 g / cm ³ or more is obtained by the following method. Due to the spheroidization, there is little diffusion during sintering, and excellent characteristics as hard particles can be obtained.

When the above-mentioned iron alloy powders were analyzed, it was found that unavoidable elements such as aluminum, boron, oxygen, nitrogen and phosphorus were 1.0% by weight or less. In addition,
Although copper, cobalt, and vanadium were also found, the total amount including the unavoidable elements was 5.0% by weight or less.

[0016]

As described above, since the high carbon iron alloy powder according to the present invention has an apparent density (AD) of 3.0 g / cm ³ or more, each powder particle is spherical. Due to this, there is little diffusion during sintering and excellent characteristics as hard particles. That is, when mixed with general steel powder, etc.,
In addition to being able to be uniformly dispersed and mixed throughout, the container can be densely filled, and desired compression deformation resistance and abrasion resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a photomicrograph of a high carbon iron alloy powder according to a preferred embodiment of the present invention.

FIG. 2 is a table showing apparent densities of high carbon iron alloy powders having six kinds of component ratios.

FIG. 3 is a graph showing a relationship between an apparent density (AD) and a manganese-silicon ratio (Mn / Si ratio) based on the results of FIG.

FIG. 4 is a micrograph of a high carbon iron alloy powder according to a conventional technique.

Claims (3)

[Claims] Claims 1. The composition contains at least 0.8% by weight of carbon (C),
A high carbon iron alloy powder characterized in that a manganese-silicon ratio (Mn / Si ratio) is set so that an apparent density (AD) is 3.0 g / cm ³ or more. 2. Carbon (C) 2.0 to 4.0% by weight, silicon (Si) 2.0% by weight or less, nickel (Ni) 0 to 25.0% by weight, chromium (Cr) 20.0 to 2.0% by weight. 40.0% by weight, molybdenum
(Mo) and tungsten (W) have a tungsten equivalent of 10.0
40.0 wt% or less, the balance being iron having 5.0 wt% or less of impurities, as manganese apparent density (AD) is 3.0 g / cm ³ or more - silicon ratio (Mn / Si ratio) is set High carbon iron alloy powder characterized by being made. 3. The high carbon iron alloy powder according to claim 1, wherein the molten alloy is powdered by a water spray method.