KR20180008730A - A mixed powder for iron powder metallurgy, a method for producing the same, and a sintered body - Google Patents

Abstract

The iron powder metallurgy mixed powder of the present invention contains a powder containing calcium anhydrous type II calcium sulfate such that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less. The powder containing the anhydrous type II calcium sulfate preferably has a volume-average particle diameter of 0.1 to 60 탆 and is preferably one or more selected from the group consisting of a Ca-Al-Si-based oxide and a Ca-Mg-Si-based oxide It is preferable to further include a ternary oxide. The weight ratio of the ternary oxide to CaS after sintering is preferably 3: 7 to 9: 1.

Description

A mixed powder for iron powder metallurgy, a method for producing the same, and a sintered body

The present invention relates to a mixed powder for iron powder metallurgy and a sintered body produced using the same. More specifically, the present invention relates to a mixed powder for iron powder metallurgy comprising a specific amount of anhydrous calcium sulfate of type II, To a sintered body.

Powder metallurgy is widely used as an industrial production method for various mechanical parts. The iron powder metallurgy is firstly prepared by mixing an iron powder, an alloy powder such as copper (Cu) powder or nickel (Ni) powder, graphite powder and a lubricant. Next, this mixed powder is filled in a metal mold, press molded, and sintered to produce a sintered body. Finally, the sintered body is subjected to cutting such as drilling or turning to adjust it to a mechanical part of a desired shape.

The ideal of powder metallurgy is to process the sintered body so that it can be used as a mechanical part without cutting the sintered body. However, the sintering may cause uneven shrinkage of the raw material powder in some cases. In recent years, dimensional accuracy required for mechanical parts is high, and the shape of parts is complicated. For this reason, it is necessary to subject the sintered body to a cutting process. From such technical background, machinability is imparted to the sintered body so as to smoothly process the sintered body.

As a means for imparting the machinability, there is a method of adding MnS powder to the mixed powder. The addition of manganese sulfide powder is effective for relatively low-speed cutting such as drilling. However, addition of manganese sulfide powder is not necessarily effective in recent high-speed cutting processing, there is a problem that the sintered body is contaminated, and mechanical strength is lowered.

Patent Document 1 (Japanese Patent Publication No. 52-16684) discloses a method of imparting machinability other than the addition of manganese sulfide. Patent Document 1 discloses an iron-based raw material powder containing 0.1 to 1.0% of calcium sulfide (CaS), 0.1 to 2% of carbon (C), 0.5 to 5.0% Of copper (Cu).

The inclusion of the calcium sulfide disclosed in Patent Document 1 in the iron-based raw material powder has a problem that the strength of the mechanical parts is greatly reduced and that the mixed powder changes in time and the quality is not stabilized. Further, when the sintered steel disclosed in Patent Document 1 is machined by a cutting tool, it is difficult for the chip to be finely divided. From this, it can not be said that the sintered steel disclosed in Patent Document 1 is excellent enough to satisfy the demand for the current chip processability.

The present invention has been made in view of the above problems, and an object thereof is to provide a mixed powder for iron powder metallurgy capable of producing a sintered body of stable quality and performance.

Japanese Patent Publication No. 52-16684

The iron powder metallurgy mixed powder of the present invention contains a powder containing calcium anhydrous type II calcium sulfate such that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less.

A method for producing a mixed powder for iron powder metallurgy according to the present invention comprises the steps of: preparing a powder containing calcium anhydrous type II calcium sulfate by heating a powder containing a gypsum or a semi-gypsum at a temperature of 350 ° C to 900 ° C; , And mixing the iron powder with the powder containing the anhydrous type II calcium sulfate.

1 is an image showing an example of the appearance of a chip with good chip processability.
2 is an image showing an example of the appearance of a chip with poor chip processability.
Fig. 3 is an image of an abraded portion of the tool cutting surface after turning the sintered body manufactured in Example 26 with a cermet tip. Fig.
Fig. 4 is an image of an abraded portion of the tool cutting surface after turning the sintered body manufactured in Example 30 with a cermet tip. Fig.
5 is an observation image of the abrasion portion of the tool cutting surface after turning the sintered body manufactured in Example 32 with a cermet tip.
6 is an observation image of the abrasion portion of the tool cutting surface after turning the sintered body manufactured in Example 33 with a cermet tip.
Fig. 7 is an image of an abraded portion of a tool cutting surface after turning the sintered body manufactured in Example 34 with a cermet tip. Fig.
8 is an observation image of a wear portion of the tool cutting surface after turning the sintered body manufactured in Reference Example 1 with a cermet tip.

In order to achieve the above object, the present inventor investigated why sintered bodies disclosed in Patent Document 1 were degraded in quality and performance over time. The inventors of the present invention have found that the quality and performance of the sintered body are deteriorated because the sintered body contains calcium sulfide and hemihydrate (hereinafter, these two components are referred to as "CaS component"). That is, the present inventors have found that the CaS component changes into calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) by absorbing moisture in the atmosphere, or the CaS component aggregates by the curing reaction to form a coarse grain of 63 μm or more I found that. As a result, it has become clear that the CaS component is dispersed unevenly in the mixed powder or the sintered body to lower the machinability of the sintered body, or the water adsorbed to the CaS component expands during the sintering to lower the strength of the sintered body.

The present inventor has completed the present invention described below by further examining the crystal structure of calcium sulfate having low hygroscopicity based on the above findings.

According to the present invention, it is possible to provide a mixed powder for iron powder metallurgy capable of producing a sintered body having stable quality and performance.

Hereinafter, the mixed powder for iron powder metallurgy of the present invention and a method for producing the same will be described in detail.

<Mixed powder for iron powder metallurgy>

The iron powder metallurgy mixed powder of the present invention is a mixed powder obtained by mixing iron powder and powder containing anhydrous type II calcium sulfate (hereinafter also referred to as &quot; type II CaSO ₄ powder &quot;). Various additives such as a ternary oxide, a binary oxide, an alloy powder, a graphite powder, a lubricant, and a binder may be appropriately added to the mixed powder. In addition to these, a small amount of unavoidable impurities may be contained in the mixed powder during the production of the iron powder metallurgy mixed powder. The sintered body can be obtained by filling the iron powder metallurgy mixed powder of the present invention with a metal mold, molding and then sintering. The sintered body thus produced can be used for various mechanical parts by performing cutting processing. The use and manufacturing method of the sintered body will be described later.

<Iron powder>

The iron powder is a main component constituting the mixed powder for the iron powder metallurgy, and it is preferable that the iron powder is contained at a weight ratio of 60 wt% or more with respect to the whole iron powder powder metallurgical mixed powder. On the other hand, the weight% of the iron powder here means the ratio of the iron powder powder to the total weight other than the lubricant in the mixed powder for metallurgical metallurgy. In the following, in the case where the weight% of each component is specified, it means that the weight ratio of the component powder to the total weight of the iron powder metallurgy mixed powder excluding the lubricant is all.

Examples of the iron powder include pure iron powder such as atomized iron powder and reduced iron powder, partially-diffused alloyed steel powder, fully alloyed steel powder, or hybrid steel powder obtained by partially diffusing an alloy component into a completely alloyed steel powder Can be used. The iron-based powder preferably has a volume-average particle diameter of 50 탆 or more, and more preferably 70 탆 or more. When the volume average particle diameter of the iron powder is not less than 50 占 퐉, the handling property is excellent. The iron-based powder preferably has a volume-average particle diameter of 200 탆 or less, more preferably 100 탆 or less. When the volume average particle diameter of the iron powder is not more than 200 mu m, it is easy to form a precise shape and sufficient strength can be obtained.

<Type II CaSO ₄ powder>

The iron powder metallurgical mixed powder of the present invention is characterized by containing a powder (type II CaSO ₄ powder) containing anhydrous type II calcium sulfate. The present invention overturns the conventional technology (for example, Patent Document 1) which was thought to increase the machinability of a sintered body simply by adding a component that becomes calcium sulfide (CaS) after sintering. In other words, water-absorbing gypsum (CaSO ₄ · 2H ₂ O), anhydrous type III calcium sulfate (III-type CaSO ₄ ), and _semi -gypsum (CaSO ₄ · 1 / 2H ₂ O) The machinability of the sintered body may be lowered. On the other hand, the anhydrous calcium sulfate II has low hygroscopicity and does not absorb moisture in the atmosphere. Therefore, even when stored in a state of being contained in a mixed powder for iron powder metallurgy, the mass does not increase. In addition, the calcium sulfate anhydrous type II is changed to CaS after sintering to increase the machinability of the sintered body. For this reason, mixed powders for iron powder metallurgy including type II CaSO ₄ powder were prepared by mixing gypsum (CaSO ₄ · 2H ₂ O), anhydrous calcium sulfate (III type CaSO ₄ ), hemihydrate (CaSO ₄ · 1 / 2H ₂ O), it is possible to stably increase various performances of the sintered body.

II-form CaSO ₄ powder but containing as a main component of calcium sulfate in the form of anhydrous II, gypsum _{(CaSO 4 · 2H 2 O)} , in the form of anhydrous III calcium sulfate (III type CaSO _4), half of gypsum (CaSO ₄ · 1 / 2H ₂ O), and the like. The weight ratio of the type II CaSO ₄ powder to the anhydrous type II calcium sulfate is more preferable, and the weight ratio of the anhydrous type II calcium sulfate is more preferably 70 wt% or more, more preferably 80 wt% or more, And is preferably composed only of anhydrous type II calcium sulfate. The type II CaSO ₄ powder may be coated with a lubricant or a binder to be described later.

The II-type CaSO ₄ powder is preferably contained in the mixed powder for iron powder metallurgy such that the weight ratio of CaS after sintering is 0.01 wt% or more and 0.1 wt% or less. II-CaSO ₄ powder is more preferably in a weight ratio of CaS at least 0.02% by weight after sintering, and more preferably the weight ratio of CaS after sintering is at least 0.03% by weight. The sintered body containing CaS at such a weight ratio is particularly excellent in machinability. The type II CaSO ₄ powder is contained so that the weight ratio of CaS after sintering is 0.09 wt% or less, more preferably 0.08 wt% or less. By including CaS in such a weight ratio, the strength of the sintered body can be increased.

Here, the &quot; weight ratio of CaS after sintering &quot; means the weight ratio of CaS in the sintered body obtained by sintering the iron powder metallurgy mixed powder. The weight ratio of CaS contained in the sintered body after the sintering can be adjusted by the weight ratio of the type II CaSO ₄ powder contained before sintering.

The weight ratio of CaS contained in the sintered body is determined by calculating the weight of Ca obtained by quantitatively analyzing the weight of Ca contained in the sample piece by collecting the sample piece by processing the sintered body with a drill or the like, . This conversion is carried out by dividing by the atomic weight of Ca (40.078) and integrating the molecular weight of CaS (72.143). Since Ca rarely disappears in reaction at sintering, the weight of Ca does not change before and after sintering, and Ca and S are bonded at a ratio of 1: 1.

The volume average particle size of the II-form CaSO ₄ powder is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more. The volume average particle diameter of the II-form CaSO ₄ powder is preferably 60 μm or less, more preferably 30 μm or less, and further preferably 20 μm or less. This type II CaSO ₄ powder having a volume average particle size can be obtained by grinding and classifying, for example, a _semi- gypsum obtained by heating a gypsum at a temperature of 350 ° C or more and 900 ° C or less for 1 hour to 10 hours or less. The volume average particle diameter of type II CaSO ₄ powder smaller, even if the amount of the II-form CaSO ₄ powder in a small amount can improve the machinability of the sintered body. The volume average particle diameter is a value of the particle size D ₅₀ at an integrated value of 50% in the particle size distribution obtained by using a laser diffraction particle size distribution measuring apparatus ("Micro Model" MODEL9320-X100, manufactured by Nikkiso Co., Ltd.).

When the volume average particle size of the II-type CaSO ₄ powder is R (μm) and the weight ratio of CaS contained in the sintered body after sintering is W (% by weight), the lower limit of R ^1/3 / W is preferably 15 or more, More preferably 20 or more, and still more preferably 25 or more. Further, the upper limit of R ^1/3 / W is preferably 400 or less, more preferably 340 or less, still more preferably 270 or less. This rule is based on the inventor's experience that the relationship between the volume average particle size and weight ratio proportional to the cubic root of the volume ratio correlates with various characteristics of the sintered body. By satisfying such a numerical range, it is possible to obtain a sintered body having both excellent pressure resistance, machinability and chip processability.

<3-element oxide>

The ternary oxide may be added in order to improve the machinability when the sintered body is used for cutting for a long time. The ternary oxide can remarkably increase the machinability of the sintered body in conjunction with the addition of the II-type CaSO ₄ powder. Here, the ternary oxide refers to a composite oxide of three kinds of elements, specifically, three kinds of elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn And more preferably a Ca-Al-Si-based oxide, a Ca-Mg-Si-based oxide, or the like. Examples of the Ca-Al-Si-based oxide include 2CaO-Al ₂ O ₃ -SiO ₂ and the like. As the Ca-Mg-Si-containing oxide, and the like 2CaO · MgO · 2SiO _2. Among them, it is preferable to add 2CaO.Al ₂ O ₃ .SiO ₂ . The _{2CaO · Al 2 O 3 · SiO} 2 may be reacted with TiO ₂ contained in the coating carried out in or during a cutting tool cutting tool, so to form a protective film, and significantly improves the wear resistance of the cutting tool on the surface of the cutting tool have.

The shape of the ternary oxide is not particularly limited, but it is preferably a spherical shape or a distorted shape thereof, that is, a shape having a rounded shape as a whole.

The lower limit of the volume average particle diameter of the ternary oxide is preferably 0.1 占 퐉 or more, more preferably 0.5 占 퐉 or more, and further preferably 1 占 퐉 or more. The smaller the volume average particle diameter, the more the machinability of the sintered body can be improved by the addition of a small amount. The upper limit of the volume average particle diameter of the ternary oxide is preferably 15 占 퐉 or less, more preferably 10 占 퐉 or less, and further preferably 9 占 퐉 or less. If the volume average particle diameter is too large, it is difficult to improve the machinability of the sintered body. The volume average particle diameter of the ternary oxide is a value measured by the same measurement method as the II type CaSO ₄ powder.

The lower limit of the content of the ternary oxide is preferably 0.01 wt% or more, more preferably 0.03 wt% or more, and still more preferably 0.05 wt% or more. The upper limit of the content of the ternary oxide is preferably 0.25% by weight or less, more preferably 0.2% by weight or less, and still more preferably 0.15% by weight or less. By incorporating in such a weight ratio, it is possible to obtain a sintered body having excellent machinability even in a long-term cutting process while suppressing the cost. By using the ternary oxide in combination with the II-type CaSO ₄ powder, machinability in long-time cutting can be improved even if the amount of the ternary oxide added is small.

The weight ratio of the ternary oxide and CaS after sintering is preferably in a ratio of 1: 9 to 9: 1, more preferably 3: 7 to 9: 1, and still more preferably 4: 6 to 7: 3 . By including both components in such a weight ratio, the machinability of the sintered body can be remarkably improved.

&Lt; Binary Oxides >

The binary oxide may be added in order to improve the machinability at the beginning of cutting when the sintered body is used for cutting. Herein, the binary oxide means a composite oxide of two kinds of elements, specifically, two kinds of elements selected from the group consisting of Ca, Mg, Al, Si, Co, Ni, Ti, Mn, Fe and Zn , More preferably a Ca-Al-based oxide, a Ca-Si-based oxide, or the like. As the Ca-Al-based oxide, and the like _{CaO · Al 2 O 3, 12CaO} · 7Al 2 O 3. Examples of the Ca-Si-based oxide include 2CaO-SiO ₂ and the like.

The shape of the binary oxide, the volume average particle diameter, the measuring method thereof, and the weight ratio are preferably the same as those of the above-mentioned ternary oxide.

<Binary Oxides and Ternary Oxides>

The iron powder metallurgical mixed powder of the present invention preferably contains both a binary oxide and a ternary oxide in an amount of 0.02 wt% or more and 0.3 wt% or less in total weight. The total weight of the oxides is preferably 0.05 wt% or more, and more preferably 0.1 wt% or more. From the viewpoint of cost, the weight ratio of the binary oxide and the ternary oxide is preferably as small as possible. The total weight of the oxide is preferably 0.25% by weight or less, more preferably 0.2% by weight or less. When the total weight of the oxides is 0.25 wt% or less, the pressing strength of the sintered body can be sufficiently secured.

The weight ratio of the binary oxide and CaS after sintering is preferably in a ratio of 1: 9 to 9: 1, more preferably 3: 6 to 9: 1, and still more preferably 4: 6 to 7: 3 . By including both components in such a weight ratio, it is possible to manufacture a sintered body having excellent machinability at the beginning of cutting.

<Powder for Alloy>

The powder for alloying is added to promote the bonding between the iron powder and to increase the strength of the sintered body after sintering. Such an alloy powder is preferably contained in an amount of 0.1 wt% or more and 10 wt% or less with respect to the total of the iron powder metallurgy mixed powder. When the content is 0.1% by weight or more, the strength of the sintered body can be increased. When the content is 10% by weight or less, dimensional accuracy at the time of sintering of the sintered body can be secured.

Examples of the alloy powder include copper (Cu) powder, nickel (Ni) powder, Mo powder, Cr powder, V powder, Si powder, Mn powder and the like, and copper oxide powder. Or two or more of them may be used in combination.

<Lubricant>

The lubricant is added to the mixed powder for iron powder metallurgy in order to make it easy to take out the molded body obtained by compressing the mixed powder for iron powder metallurgy in the mold from the mold. That is, when the lubricant is added to the mixed powder for iron powder metallurgy, the extraction pressure at the time of taking out the molded body from the metal mold can be reduced, so that cracking of the molded body and damage of the metal mold can be prevented. The lubricant may be added to the mixed powder for iron powder metallurgy or may be applied to the surface of the metal mold. When the lubricant is added to the iron powder metallurgy mixed powder, the lubricant is preferably contained in an amount of not less than 0.01% by mass and not more than 1.5% by mass, more preferably not less than 0.1% by mass and not more than 1.2% by mass, based on the weight of the iron powder metallurgy mixed powder , And more preferably 0.2 mass% or more and 1.0 mass% or less. When the content of the lubricant is 0.01 mass% or more, an effect of reducing the extraction pressure of the formed article is easily obtained. When the content of the lubricant is 1.5% by mass or less, it is easy to obtain a high-density sintered body, and a sintered body having high strength can be obtained.

The lubricant may be selected from the group consisting of metal soap (lithium stearate, calcium stearate, zinc stearate, etc.), stearic acid monoamide, fatty acid amide, amide wax, hydrocarbon wax and crosslinked (meth) More than species can be used. Among them, it is preferable to use an amide-based lubricant from the viewpoints of a good ability to adhere alloy powder, graphite powder, etc. to the surface of the iron powder, and to ease segregation of the iron-base mixed powder.

<Binder>

The binder is added in order to attach alloy powder, graphite powder or the like to the iron powder surface. The binder may be a butene-based polymer, a methacrylic acid-based polymer, or the like. As the butene-based polymer, it is preferable to use a 1-butene homopolymer made of butane alone or a copolymer of butene and an alkene. The alkene is preferably a lower alkene, preferably ethylene or propylene. Examples of the methacrylic acid-based polymer include a methacrylic acid-based polymer having 1 to 10 carbon atoms selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, ethylhexyl methacrylate, lauryl methacrylate, More than species can be used.

The binder is preferably contained in an amount of 0.01 mass% or more and 0.5 mass% or less, more preferably 0.05 mass% or more and 0.4 mass% or less, further preferably 0.1 mass% or less, relative to the weight of the iron powder metallurgy mixed powder. Or more and 0.3 mass% or less.

&Lt; Method for producing mixed powder for iron powder metallurgy &

In the production of the iron powder metallurgy mixed powder of the present invention, the II-type CaSO ₄ powder contained in the mixed powder for iron powder metallurgy is first prepared. The II-form CaSO ₄ powder is preferably obtained by heating _semi- gypsum or gypsum having a volume average particle diameter of 0.1 μm or more and 60 μm or less at 300 ° C. or more and 900 ° C. or less. The volume average particle size of the _semi -gypsum or gypsum is preferably equal to or slightly smaller than the volume average particle size of the II-type CaSO ₄ powder in consideration of coagulation during heating. The lower limit of the heating temperature is preferably 350 占 폚 or higher, and more preferably 400 占 폚 or higher. The upper limit of the heating temperature is preferably 800 DEG C or lower, more preferably 700 DEG C or lower, and further preferably 500 DEG C or lower. By the heating temperature is less than 900 ℃, it can be as a powder for mixing the iron powder to obtain the II type CaSO ₄ powder having the following typical particle size 100μm. Particularly, when the heating temperature is 700 캜 or less, coagulation of _semi -gypsum or gypsum hardly occurs, and a II-type CaSO ₄ powder can be obtained while maintaining the volume average particle size of the _semi -gypsum or gypsum. When the heating temperature is high, it is preferable to carry out the pulverizing step because strong aggregation occurs. When the heating temperature is 300 占 폚 or higher, the water of the _semi -gypsum gypsum or gypsum gypsum can be dehydrated to form the II-type CaSO4 powder. When the heating temperature is low, it is not preferable that anhydrous type III CaSO ₄ is formed instead of anhydrous type II CaSO ₄ .

It is preferable that the heating time is such that the time for dewatering the semi-gypsum or gypsum to II-form calcium sulfate is secured, and it is preferably not less than 1 hour and not more than 8 hours. The higher the heating temperature, the shorter the heating time. When the heating time is short, a part of the semi-gypsum gypsum may not remain as the II-type calcium sulfate, and may remain in the form of semi-gypsum or may change to the anhydrous type III calcium sulfate. Therefore, the heating time is preferably 2 hours or more, and more preferably 3 hours or more.

The iron powder metallurgy mixed powder of the present invention can be produced by mixing iron powder and II-type CaSO ₄ powder prepared above, for example, by using a mechanical stirring type mixer. In addition to these powders, various additives such as a ternary oxide, an alloy powder, a graphite powder, a lubricant, a binary oxide, and a binder may be appropriately added. Examples of the mechanical stirring type mixer include a high speed mixer, a Nauta mixer, a V type mixer, and a double cone blender. The mixing order of the powders is not particularly limited. The mixing temperature is not particularly limited, but is preferably 150 DEG C or lower from the viewpoint of suppressing the oxidation of the iron powder in the mixing step.

&Lt; Manufacturing method of sintered body >

The iron powder powder metallurgical mixed powder prepared above is filled in a metal mold, and a pressure of 300 MPa or more and 1200 MPa or less is applied to produce a green compact. The molding temperature at this time is preferably 25 ° C or more and 150 ° C or less.

The sintered body can be obtained by sintering the above-mentioned powder compacted body by a usual sintering method. The sintering condition may be a non-oxidizing atmosphere or a reducing atmosphere. It is preferable that the above-mentioned compacted compact is sintered at a temperature of 1000 占 폚 to 1300 占 폚 for 5 minutes to 60 minutes in a nitrogen atmosphere, a mixed atmosphere of nitrogen and hydrogen, and an atmosphere of hydrocarbon.

<Sintered body>

The sintered body manufactured as described above can be used as a mechanical part such as an automobile, an agricultural equipment, an electric power tool, and an electric appliance by machining with various kinds of tools such as a cutting tool if necessary. Examples of the cutting tool for machining the sintered body include a drill, an end mill, a cutting tool for pricing, a cutting tool for turning, a reamer, and a tap.

According to the mixed powder for iron powder metallurgy of the above embodiment, a sintered body having stable quality and performance can be produced. Since the anhydrous type II calcium sulfate contained in the mixed powder for the iron powder metallurgy of the above embodiment has low hygroscopicity and does not absorb moisture in the atmosphere, the powder containing the anhydrous calcium sulfate type II, Is not increased. Therefore, by using powders (II-type CaSO ₄ powder) containing calcium sulfate anhydride type II rather than calcium sulfide and hemihydrate as components to be sintered to become CaS, it is possible to stably increase various performances of the sintered body have.

In the above embodiment, the II-type CaSO ₄ powder has a volume-average particle diameter of 0.1 μm or more and 60 μm or less, so that the machinability of the sintered body can be increased.

When the volume average particle diameter of the II-type CaSO ₄ powder is R μm and the weight ratio of CaS contained in the sintered body after sintering is W% by weight, R ^1/3 / W is 15 or more and 400 or less, A sintered body having good chip processability can be obtained.

The iron powder metallurgical mixed powder of the above embodiment additionally contains at least one kind of ternary oxide selected from the group consisting of Ca-Al-Si oxide and Ca-Mg-Si oxide, The machinability can be improved.

The weight ratio of the ternary oxide to the CaS after sintering is 3: 7 to 9: 1 in the iron powder metallurgy mixed powder of the above embodiment, so that the machinability in the long-time cutting can be improved.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

(Example 1)

First, commercially available semi-gypsum powder was classified by sieving to -63 / + 45 mu m (volume average particle diameter 54 mu m). The classified gypsum was heated in an atmospheric furnace at 350 ° C for 5 hours to obtain an anhydrous type II calcium sulfate powder (type II CaSO ₄ powder). This type II CaSO ₄ powder was classified by sieving to -63 / + 45 μm (volume average particle size 54 μm). The yield of the obtained type II CaSO ₄ powder was 100%. This yield is a value obtained by calculating the percentage of the weight of the II-type CaSO ₄ powder after heating, minus the weight of the II-type CaSO ₄ powder removed by classification from the weight.

Next, 2 wt% of a copper powder (product name: CuATW-250 (manufactured by Fukuda Metal Powder Co., Ltd.)) and 0.8 wt% of graphite powder (product name: Atmel 300M (product of Kobe Steel Co., (Manufactured by Nippon Graphite Kogyo Co., Ltd.), 0.75 wt% of an amide-based lubricant (Accra Wax C (manufactured by LONZA)), and the II-type CaSO ₄ powder prepared above, To prepare a mixed powder. The graphite powder was added in such an amount that the amount of carbon after sintering was 0.75% by weight. The type II CaSO ₄ powder was added in such an amount that the weight of CaS after sintering became 0.5 wt%.

Two kinds of sintered bodies were produced using the iron powder metallurgy mixed powder. One is a sintered body (hereinafter referred to as &quot; sintered body immediately after &quot; hereinafter) produced by using a mixture powder for iron powder metallurgy immediately after its production, and the other is a mixture powder for iron powder metallurgy (Hereinafter referred to as &quot; sintered body after 10 days &quot;).

Immediately after the sintered body was manufactured, a mold was filled with a powder mixture for iron powder metallurgy immediately after fabrication, and a test piece was molded in a ring shape having an outer diameter of 64 mm, an inner diameter of 24 mm and a thickness of 20 mm, and a molding density of 7.00 g / cm ³ . Next, this ring-shaped test piece was sintered at 1130 캜 for 30 minutes under an atmosphere of 10% by volume of H ₂ -N _{2 to} prepare a sintered body. On the other hand, after 10 days, the sintered body was fabricated in the same manner as the sintered body immediately after the iron powder metallurgy mixed powder was prepared, except that the iron powder powder was filled in the mold after being left in the atmosphere for 10 days.

(Examples 2 to 8)

In Examples 2 to 8, a sintered body was produced in the same manner as in Example 1 except that the heating temperature of the powder of the gypsum gypsum was changed as shown in the column of "heat treatment temperature" in Table 1.

(Comparative Examples 1 to 3)

In Comparative Examples 2 to 3, a sintered body was produced in the same manner as in Example 1 except that calcium sulfate anhydrous type II was changed to the material shown in the column of &quot; CaS component &quot; In Comparative Example 1, a sintered body was produced in the same manner as in Example 1, except that calcium sulfate anhydrous type II was not added.

<Evaluation>

In Table 1, the results of the evaluation of the compact density, the sinter density, the pressing strength and the tool wear amount are described as &quot; sintered body immediately after / 10 days after sintering &quot;. This notation is the evaluation result of the sintered body immediately after the value on the left side with the slash interposed therebetween, and the evaluation result of the sintered body after 10 days on the right side with the slash in between.

The densities of the sintered bodies immediately after each of the Examples and Comparative Examples and the densities of the sintered bodies after 10 days and the density of the sintered bodies were measured according to the Japanese Powder Metallurgy Industry Association (JPMA M 01). The sintered body of each of the Examples and Comparative Examples was measured in accordance with JIS Z 2507-2000. The higher the pressing strength, the more difficult it is to break the sintered body and the higher the strength.

Using a sintered body manufactured in each of the examples and comparative examples, a sintered body having a circumferential speed of 160 m / min, an infeed of 0.5 mm / pass and a feed of 0.1 mm / rev using a cermet tip (ISO product number: SNGN120408 nonbreaker) , The tool wear amount (μm) of the cutting tool when it was turned at 1150 m under the dry condition was measured by a tool microscope. The results are shown in the column of &quot; tool wear amount &quot; in Table 1. On the other hand, the smaller the value of the tool wear amount, the better the machinability of the sintered body.

The embodiments shown in Table 1 in the Examples and from the respective comparative example, a result, by containing the II-form CaSO ₄ powder as CaS ingredients, with each of the examples, various properties immediately after the sintered body, and 10 days of the sintered body (sintered body density, aphwan strength and The amount of tool wear) were found to be substantially equal. On the other hand, in Comparative Examples 2 and 3, since CaS single component or hemihydrate gypsum was contained as a CaS component, various characteristics of the sintered body after 10 days were remarkably deteriorated as compared with that of the immediately after sintered body.

The reason why the quality and performance of the sintered body deteriorated after 10 days in Comparative Examples 2 and 3 is that CaS or hemihydrate gypsum in the mixed powder for iron powder metallurgy absorbs moisture while the mixed powder for iron powder metallurgy is left for 10 days It is thought to be caused by one thing. That is, in Comparative Examples 2 and 3, the CaS single body or semi-gypsum in the mixed powder for iron powder metallurgy absorbed moisture during storage under the atmosphere for 10 days, whereby the density of the sintered body was lowered or the pressing strength was lowered I think. On the other hand, in Comparative Example 1, since the CaS component was not contained, the sintered body immediately after sintering after 10 days had a significantly increased amount of tool wear, and the machinability of the sintered body was remarkably low.

In addition, the sintered body after 10 days of Example 8 has various performance deterioration as compared with those of Examples 1 to 7 after the sintered body immediately after the sintered body. This is because the heating temperature for the semi-gypsum of Example 8 was lower than those of Examples 1 to 7 so that part of the gypsum gypsum did not change to calcium type II sulfate and changed to calcium type III sulfate, It is considered that these components remain in the form of half-gypsum and that these components exhibit hygroscopicity. However, the stability of various performances of the sintered body obtained in Example 8 is remarkably superior to that of Comparative Examples 1 to 3. Therefore, as in Example 8, it became clear that the effect of increasing the stability of the sintered body can be obtained even if all of the semi-gypsum is not made of calcium sulfate II.

Paying attention to the "yield" in Examples 1 to 7 of Table 1, the higher the heating temperature of the semi-gypsum, the lower the yield is. The reason for this is believed to be that as the heating temperature is raised, the II-form calcium sulfate coagulates to form a large granular material, and the large granular material is removed by classification. Therefore, in order to efficiently obtain a powder composed of calcium sulfate II, it has become clear that it is preferable to set the heating temperature of the gypsum gypsum to not less than 350 ° C and not more than 600 ° C.

From the results shown in Table 1, by including the II-type CaSO ₄ powder as the CaS component, various characteristics (sinter density, pressing strength and tool wear amount) of the immediately after sintered body and the sintered body after 10 days became almost equal, And the performance is stable, and the effect of the present invention has been shown.

(Examples 9 to 29)

Except that the volume average particle size of the II-type CaSO ₄ powder and the weight ratio of CaS after sintering were changed as shown in the column of "volume average particle size" and "CaS weight ratio" in Table 2, And each item was evaluated by the same method as in Example 1. [ The results are shown in Table 2. The adjustment of the volume average particle size of the II-type CaSO ₄ powder used in each example was carried out by subjecting the heat-treated II-type CaSO ₄ powder to various pulverization and classification.

On the other hand, in Examples 9 to 29, two kinds of sintered bodies immediately after the sintered body and 10 days later were produced and evaluated for their respective properties in the same manner as in Example 1. However, in both of the evaluation items, . In Table 2, only one measurement value is described. From the results shown in Table 2, it can be seen that the sintered bodies produced using the iron powder metallurgy mixed powders of Examples 9 to 29 have stable quality and performance, and the effect of the present invention has been shown.

The &quot; chip processability &quot; in Table 2 is a result of evaluating the appearance of a chip produced by turning using a cermet tip based on the following evaluation criteria.

(Evaluation criteria of chip processability)

?: The number of turns (number of turns) on the spring is one or less (for example, Fig. 1).

○: The number of curls is within one to three books.

X: The number of curls exceeds three (for example, Fig. 2).

As shown in Fig. 1, if the chips are finely divided, the cleaning frequency of the chip hopper of the cutting machine can be suppressed. On the other hand, as shown in Fig. 2, if the chip is elongated in a coil-like shape, the chips are complicatedly entangled in the chip hopper, resulting in troublesome cleaning and a frequent cleaning of the chip hopper, , The tool wear amount can be reduced, but the automatic operation can not be performed for a long period of time, so that it is difficult to increase the workability and efficiency.

From the results shown in Table 2, it was found that a sintered body having excellent both of the pressing strength, the amount of tool wear and the chip disposability can be manufactured by having R ^1/3 / W of 20 or more and 340 or less. On the other hand, when R ^1/3 / W is less than 20, the chip processability tends to deteriorate. When R ^1/3 / W exceeds 340, a tendency to increase the pressing strength and a tendency that the amount of tool wear tends to remarkably increase.

(Examples 30 to 34 and Reference Examples 1 to 2)

In Examples 30 to 34, as in Example 26 except that a part of II-form CaSO ₄ powder was replaced with 2CaO-Al ₂ O ₃ -SiO ₂ or 2CaO-MgO 2SiO ₂ as shown in Table 3 To prepare a sintered body. In Reference Examples 1 and 2, a sintered body was produced in the same manner as in Example 26 except that the entirety of the type II CaSO ₄ powder was replaced by 2CaO.Al ₂ O ₃ .SiO ₂ or 2CaO.MgO 2SiO ₂ . On the other hand, 2CaO.Al ₂ O ₃ .SiO ₂ and 2CaO.MgO 2SiO _{2 each} having a volume average particle diameter of 2 μm were used. Further, the II-type CaSO ₄ powder was used with a volume average particle diameter of 18.4 μm.

Each item was evaluated by the same method as in Example 26 for each of the sintered bodies produced in the respective Examples and Comparative Examples thus manufactured. The results are shown in Table 3. On the other hand, in each of Examples 30 to 34, two sorts of the sintered body immediately after the sintering and the sintered body after 10 days were manufactured and their respective characteristics were evaluated. However, since the measured values in both evaluation items were the same or negligible, Table 3 shows only one measurement value. Therefore, the sintered bodies produced by using the iron powder metallurgy mixed powders of Examples 30 to 34 were found to have stable quality and performance, and the effect of the present invention was exhibited.

From the results shown in Table 3, it was found that the amount of tool wear can be further reduced by replacing part of the II-form CaSO ₄ powder with a ternary oxide. In particular, as shown in the results of Examples 32 to 34, it became clear that the amount of tool wear can be remarkably reduced when the weight ratio of the ternary oxide and CaS after sintering is 3: 7 to 9: 1.

The reason why the amount of tool wear can be reduced in this way is believed to be the result of the interaction between the II-type CaSO ₄ powder and the ternary oxide.

The reason for this reason is that the wear type of the cutting surface of the tool and the components of the abrasion portion were different in the case of using the II-type CaSO ₄ powder and the ternary oxide in combination and in the case of the ternary oxide alone. Figs. 3 to 8 are images obtained by observing the abraded portion of the tool cutting surface after turning the sintered body manufactured in Examples 26, 30, 32 to 34, and Reference Example 1 with a cermet tip by an optical microscope. As shown in Figs. 4 to 7, when the II-type CaSO ₄ powder and the ternary oxide were used in combination (Examples 30 and 32 to 34), adhesion of iron was reduced, and wear of the groove was not observed. On the other hand, in the case where only the ternary oxide was added without adding the II-type CaSO ₄ powder (Reference Example 1), as shown in Fig. 8, groove wear was formed and adhesion of iron was observed. Further, in the abrasion parts of Examples 30 and 32 to 34, ternary oxide components were detected in the entire abraded surface, while in the abraded parts of Reference Example 1, ternary oxide was detected in only part of the abraded parts in half a month. On the other hand, in the case where only the II-form CaSO ₄ powder was added without adding the ternary oxide (Example 26), the area of the half-moon abrasion portion of the tool cutting surface was smaller than those of Examples 30 and 32 to 34 Area), and the partial adhesion of iron (Fe) was large. The iron adhered to the tool repeatedly adheres to and detaches from the tool, so that the wear of the cutting tool tends to proceed or the surface of the workpiece may not be smooth.

From the above results, it is clear that the machinability of the sintered body is superior by using the II-type CaSO ₄ powder and the ternary oxide in combination as in Examples 30 to 34.

Claims (8)

Wherein the powder containing calcium anhydrous type II calcium sulfate is contained in an amount of not less than 0.01% by weight and not more than 0.1% by weight of CaS after sintering. The method according to claim 1,
Wherein the powder containing calcium anhydrous type II calcium sulfate has a volume-average particle diameter of 0.1 占 퐉 or more and 60 占 퐉 or less. 3. The method according to claim 1 or 2,
Ca-Al-Si-based oxide, and Ca-Mg-Si-based oxide. The method of claim 3,
Wherein the weight ratio of the ternary oxide to the CaS after sintering is 3: 7 to 9: 1. The method according to claim 1,
The volume average particle diameter of the powder containing the anhydrous type II calcium sulfate was set to R 占 퐉,
When the weight ratio of CaS contained in the sintered body after sintering is W% by weight,
R ^1/3 / W is not less than 15 and not more than 400, and iron powder is a mixed powder for metallurgy. The method according to claim 1,
Wherein the powder containing the anhydrous type II calcium sulfate is coated with a lubricant or a binder. A sintered body produced by sintering the iron powder metallurgy mixed powder according to claim 1. A step of producing a powder containing calcium anhydrous type II calcium sulfate by heating a powder including iridescent or semi-iridescent gypsum at 350 DEG C or higher and 900 DEG C or lower;
And mixing the iron powder with the powder containing the anhydrous type II calcium sulfate.

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