JPH03100104A - Manufacture of iron-copper series powder metallurgical product - Google Patents

Abstract

PURPOSE:To manufacture a large scale Fe-Cu series powder metallurgical product having excellent strength at low cost by sintering together with a molding mold after packing ferrous powder into the molding mold under non-pressurizing and successively, infiltrating the specific composition of Cu series infiltrant. CONSTITUTION:The fine powder of pure iron or alloy steel is packed into the compacting mold having the prescribed shape while vibrating under non- pressurizing and sintered under inert gas atmosphere or reducing atmosphere. The Cu series infiltrative material obtd. by adding and containing <= 8 wt.% infiltration improving agent of Mn, Zn, etc., to and in mixed material having composition composed of 2-9 wt.% Fe, 3-13 wt.% one or more kinds of Ni, Cr and Mo in total and the balance Cu, is infiltrated to the sintered product. As the other way, the above compositionof infiltrant is laid on the feerous powder green compact and heated under non-oxidizing atmosphere to execute the sinter of green compact and the infiltration of infiltrant at the same time. The sintered product having excellent strength can be manufacture in the simple process at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing large sintered members such as molds, and particularly to a method for manufacturing large-sized sintered members such as molds, and in particular, the main objective is to increase the strength of the members.

[Prior Art 1] Large sintered members such as molds are manufactured by applying powder metallurgy. The inventors of the present invention discovered in Japanese Patent Application No. 62-3 that complex-shaped parts can be manufactured in a short period of time by this method.
It was disclosed in Japanese Patent No. 22869 and Japanese Patent No. 62-322870.

These methods involve filling a mold with iron-based powder without pressure and sintering it together with the mold to obtain a large component. This is a manufacturing method that fills the voids by infiltrating with an infiltrating material.

[Problems to be Solved by the Invention] However, since the above method is filled without pressure, the packing density of the iron-based powder is relatively small, and even if the voids are filled with an infiltrant,
The problem still often arises that the strength of the sintered body is insufficient.

In order to improve the strength, the first step is to use Ni and Cr as iron-based powders.
There is a method of using alloyed copper powder containing , Mo, etc.

However, in order to increase the packing density of iron-based powder even a little, the particle size structure is important, and alloy steel powder with a special particle size is difficult to obtain at a low price, resulting in cost problems.

Second, a method using a mixed powder in which powders such as Ni, Cr, and Mo are added to iron powder is considered as the iron-based powder.

However, in this case as well, the particle size structure of the mixed powder is important;
If the particle size of the Ni powder is limited in order to ensure the packing density, the problem of increased cost arises.

Thirdly, there is a method of containing Ni etc. in addition to Cu as a copper-based infiltrant.
In the publication, an infiltrant consisting of 15 to 30% by weight of Ni, 25 to 35% by weight of Mn, and the balance Cu is dissolved in a container,
Discloses a method of pouring and infiltrating a packed body of iron-based powder. In this method, the infiltrant is melted in a container and then poured into the iron-based powder filling, which is a different method from normal infiltration, so the dimensions are matched to the iron-based powder filling. Compared to a method in which iron-based powder is infiltrated with an infiltrant that is brought into contact with the iron powder, uniform infiltration is difficult to achieve, and the equipment also has complicated ancillary mechanisms, resulting in high costs.

Further, in the method of bringing an infiltrant into contact with a filler of iron-based powder to infiltrate it, there is a problem that the infiltrant having the above composition does not sufficiently penetrate into the iron-based powder.

As described above, there is currently no method of obtaining sufficient strength by infiltration of a non-pressurized filler, depending on the prior art and the technology analogous to it.

[Means to solve the problem]

The present inventors have completed the present invention as a result of intensive research to solve the above problems.The present invention involves filling iron-based powder into a mold without pressure and heating it together with the mold. Sintered, and then infiltrated into the sintered body with a copper-based infiltration material consisting of Fe: 2 to 9% by weight, Ni% Cr and Mo: 3 to 13% by weight in total of one or more types, Cu and unavoidable impurities: the balance. Iron characterized by
A method for manufacturing a copper-based powder metallurgy product is provided, in which the copper-based infiltrant can contain an infiltration aid of 8% by weight or less of the infiltrant.

According to the method of the present invention, inexpensive iron powder can be used as the iron-based powder, the preparation of the infiltrant is extremely easy, there are great cost advantages, and the effect of increasing strength is excellent.

[Effect] Hereinafter, the operation of the method of the present invention will be described in detail.

The amount of Fe in the infiltrant is 2 to 9% by weight. This is because the iron-based powder filled without pressure is eroded by the Cu melt and the filling uniformity deteriorates, pores are reduced, and infiltration is interrupted midway, resulting in a decrease in strength. If Fe is less than 2% by weight, this effect will be insufficient, while if it exceeds 9% by weight, the infiltration property will deteriorate.

One or more of Ni, Cr, and Mo is contained in the infiltrant.

All of these elements are dissolved in Fe to increase the strength, and since they can be easily handled by hand in the form of powder, it is easy to prepare an infiltration agent. The total amount of one or more of Ni, Cr, and Mo is 3 to 13% by weight. If it is less than 3% by weight, the reinforcing effect will be insufficient, and if it exceeds 13% by weight, the infiltration properties will deteriorate and the effect of reinforcing Fe will be saturated, resulting in a decrease in strength.

The remainder of the infiltrant other than the above-mentioned components consists of copper and unavoidable impurities. Unavoidable impurities include Si1.1. Possible examples include C. The presence of these materials in conventional amounts does not inherently adversely affect the effectiveness of the process.

The infiltrant of the present invention can contain up to 8% by weight of an infiltration aid. Mn, Zn, etc. are used as infiltration aids, and infiltration is carried out very smoothly, and even if these are contained, the strength of the sintered member is not reduced.

In the method of the present invention, it is preferable to use pure iron powder as the iron-based powder in terms of cost, but alloy steel powder can also be used.
A material having a maximum particle size of 500 LLm and containing fine powder with a particle size of 10 gm or less is preferably used.

The iron-based powder is filled into a mold prepared in advance. The mold may have sufficient strength up to the temperature at which the powder improves its strength through sintering and correctly transfers the shape of the mold, and does not impair the transfer of the molding due to significant reaction with the powder. Usually, a ceramic mold is used because it can maintain its strength up to high temperatures.

The shape of the mold is such that the sintered body can function as a mold or the like after the sintering process, either as it is or without significant processing. The production method may be by machining or by the production method of ceramic molds used in precision casting. It's also good.

Filling is done in a dry manner, and the packing density can be improved by adding vibration. The vibration method may be any method such as electromagnetic vibration or mechanical vibration.

In addition, by applying extremely lower pressure during vibration than in conventional pressure molding methods, filling properties can be further improved. This pressure is usually 1 kg/crn'' or less (applying pressure not only improves the filling property but also has the advantage of improving the transferability of the edge portion of the mold. By using such a filling method, , it is possible to mold large-sized products easily and inexpensively without using the expensive press machines used in normal powder metallurgy, making it extremely suitable for manufacturing injection molds as large as 1m x 1m. .

Next, the mold filled with powder is placed in a furnace and sintered. Sintering is done in a reducing atmosphere, an inert atmosphere.

Or do it in a vacuum and do not break the mold after sintering.

Since the obtained sintered body alone does not have sufficient strength as a mold, etc., it is infiltrated with a copper-based infiltrant having the above-mentioned composition in the pores remaining in the sintered body to increase its strength. Infiltration can be carried out in a reducing atmosphere, inert atmosphere or vacuum.

Incidentally, even if the sintering and infiltration steps are performed in one step, that is, in one heat cycle, the effect obtained remains the same.By using one step, there is an advantage that the manufacturing process can be shortened.

As described above, according to the present invention, large-sized powder metallurgy products with high strength can be manufactured at low cost.

[Example] Example 1 As iron-based powder, average particle size 230 μm (particle size range 150 μm)
35 parts by weight of atomized pure iron powder with an average particle size of 29 μm (particle size range 15 to 63 μm), 35 parts by weight of atomized pure iron powder with an average particle size of 4.8 μm (particle size range 10 μm)
An iron powder whose particle size structure was adjusted by mixing 30 parts by weight of carbonyl iron powder (less than m) was used.

A ceramic mold with a surface roughness (Ra value) of 0.3 μm was used as a mold, and the mixed powder was filled by vibration. A copper-based infiltrant material formed by press-molding the powder described later into a molded body was placed on the surface of the filling body, and the ceramic mold, the powder filling body, and the infiltration material were placed in a furnace, and heated in a nitrogen gas atmosphere for 10 minutes.
After heating at 0°C for 70 minutes to sinter the filler, the temperature was raised to 1180°C over 2 hours to melt the infiltrant and advance infiltration. The holding time at 1180°C was 100 minutes, and then the furnace was cooled.

After cooling, the infiltrated sintered body is taken out from the ceramic mold and is 6 (height) x IOC width) x 35 (length) mm.
A test piece was cut out and the transverse rupture strength was determined.

As the copper-based infiltrant, atomized copper powder of -150 μm as Cu, electrolytic nickel powder of -150 μm as Ni,
65% Cr-containing ferrochrome (Fe-Crl crushed powder o) -150 μm as Cr and Fe
Using reduced molybdenum powder of After adding 0.8% by weight to the mixture, it was molded at a pressure of 4t/crn' and used.

The transverse rupture strength of each test piece is shown in Table 1.

As is clear from Table 1, for No. 1, which does not contain any of Fe, Ni, Cr, or Mo, 3.4.5.9.1O513,14,15,18,1 was obtained by the method of the present invention.
No. 9, 20, 22, 23, and 24.25.26.27 all have high strength with a transverse rupture strength of 150 kg f/mrn. On the other hand, No. 2.7%8 .1
2.17 is Fe.

The strength is insufficient due to the lack of any one of Ni, Cr, and Mo, while the strength of Dynamic 6.11.16.21 is actually reduced due to an excess of any one of them.

〔Effect of the invention〕

With the present invention, large-sized powder metallurgy materials with high strength can be produced at low cost.

Claims (1)

[Claims] 1. Iron-based powder is filled into a mold without pressure, heated and sintered together with the mold, and then the sintered body is coated with Fe: 2 to 9% by weight, Ni, Cr, and Mo: 1 The total amount of 3 to 13% by weight of Cu and unavoidable impurities: the iron is infiltrated with a copper-based infiltrant consisting of the balance.
A method for producing copper-based powder metallurgy products. 2. The method for manufacturing an iron-copper powder metallurgy product according to claim 1, wherein the copper-based infiltrant contains an infiltration aid in an amount of 8% by weight or less of the infiltrant.