JPH0297606A - Manufacture of strip-like metal sintered body - Google Patents

Abstract

PURPOSE:To manufacture a strip-like metal sintered body having excellent cold-rolling property with sintering in a short time by executing the sintering through a continuous heating furnace after compacting the metal powder made to the specific particle diameter into the strip-like body having the specific true density ratio and coiling this. CONSTITUTION:After compacting the metal powder into the continuous strip-like body, the sintering is executed by using the continuous heating furnace and this is coiled. In the manufacture of the above strip-like metal sintered body, the average particle diameter of the above metal powder is made to <=100mum. Further, the true density ratio in the above powder compacting work is made to 60-90%. The green compact obtd. by this method is sintered in a short time, such as some few min. The strip-like metal sintered body obtd. by this method has good cold-rolling property and crack is not developed in the cold-rolling and the strip-like cold-rolled material can be obtd. at high yield and good efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a sintered metal strip, and particularly to a novel improvement for improving cold rollability.

[Conventional technology] Generally, metal materials are manufactured through processes such as melting, casting, hot working, and cold working. However, for materials that are difficult to process or materials that cause significant segregation, metal powder is compacted. It may be produced by sintering this, and then further hot or cold processing.

In the production of metal materials using such powder metallurgy methods, it is common that the material is first compacted and then sintered in batches. Furthermore, even when sintering is performed using a continuous heating furnace, the individual powder compacts are simply sintered continuously, and the objects to be processed are It is normal that the lines are not continuous.

- Regarding the application of the powder metallurgy method to the production of old root products, metal powder is once compacted into a block shape and then subjected to normal sintering or pressure sintering treatment such as HIP. Furthermore, there is a method of hot or cold rolling to obtain a strip-shaped plate product. Apart from this, there is also a method of directly compacting metal powder into a belt shape and sintering it to obtain a belt-shaped product.

In the latter method, it is conceivable to wind up a continuous belt-shaped powder compact into a coil shape and then sinter it in batches, but the problem with the compacting process is that it is difficult to wind the compact into a coil or to sinter it in batches. Because it does not have sufficient strength to be used in the sintering process,
This is a method that is difficult in practice. For this reason, the belt-shaped powder is sintered as it is in a continuous heating furnace.
An effective method is to increase the strength and then wind it into a coil.

[Problems to be Solved by the Invention] Since the conventional method for manufacturing a band-shaped metal sintered body was configured as described above, the following problems existed. In other words, the above-mentioned method of directly compacting into a strip and sintering it continuously is a simple and efficient method for producing a strip of metal sintered body, but the process of compacting and sintering is a simple and efficient method. Since the process is continuous, it is necessary to devise a manufacturing method. In other words, a method using rolls called powder rolling is used to compact powder into strips, but in order to process continuously, it is necessary to match the processing speed of sintering to the processing speed of powder compaction. be. Therefore, in powder compacting by powder rolling, it is difficult to reduce the compacting speed extremely.
The sintering processing speed must also be adjusted accordingly.
Increasing the sintering temperature is effective in achieving sufficient sintering and increasing the strength of the material to be treated, but there are limits to this, and increasing the sintering time is effective. .

However, if the sintering time is equal to that of batch type sintering, the processing speed is relatively high, so the furnace length of a continuous heating furnace will be long and unrealistic, making it impossible to realize. Therefore, in the process of strip compaction and continuous sintering,
The sintering time has to be shortened, and the strength of the sintered band-shaped metal sintered body, that is, the cold rolling property after sintering tends to be poor.

As described above, in the case of a sintered body having poor cold rolling properties, there have been problems such as cracks occurring during cold rolling, which lowers the yield, and increased costs due to an increased number of annealing steps.

The present invention has been made to solve the above-mentioned problems, and in particular, it provides a sintered metal strip that improves the cold rollability of the sintered metal strip produced by short-time sintering. The purpose is to provide a manufacturing method for.

[Means for Solving the Problems] The method for producing a band-shaped metal sintered body according to the present invention involves compacting metal powder into a continuous band shape, sintering it using a continuous heating furnace, and winding it up. In the production of a band-shaped metal sintered body consisting of a process, the average particle size of the metal powder is 100 μm or less, and the true density ratio in compaction is 60 to 90%.
This is the method.

[Function] In the method for producing a band-shaped metal sintered body according to the present invention, the average particle size of the metal powder is set to 100 μm or less, and the true density ratio during powder compacting is set to 60 to 90%. No cracks occur, and cold rollability can be greatly improved.

[Example 1] Hereinafter, a method for manufacturing a band-shaped metal sintered body according to the present invention will be described in detail with reference to the drawings. First, the average particle size of the metal powder used in the powder compacting of the present invention is limited to 100 μm or less. FIG. 1 compares the cold rolling rate at which edge cracks begin to occur when a metal sintered body is cold rolled when the average grain size is varied. The powder in this case is iron powder, and the plate thickness is 2.5 cm for powder compaction.
The true density ratio was set to 78%, and the sintering was performed at 75%H2~
The test was conducted under the conditions of 1200°C and 5m1n in a 25% N2 atmosphere (Samples No. 1 to No. 3).
As can be seen from the figure, compared to the case where large powder with an average particle size exceeding 100 μm is used, when the average particle size is reduced to 100 μm or less according to the method of the present invention, it is better to cold-roll the powder with a particle size of 100 μm or less. The cold rolling ratio at which cracks start to appear is increased, and the cold rolling properties are improved. In addition,
Figure 1 shows powder compaction performed under similar conditions, the atmosphere and temperature conditions being the same, only the time being longer at 60 ml (sample No.
o, 4) The case of long-time sintering is also noted, but in this case, even with an average grain size of 121 μm, cold rolling is possible to 49% without cracking.

In addition, in the method of the present invention, the true density ratio in powder compaction is 60 to
It is limited to 90%. That is, Fig. 2 shows a comparison of the cold rolling rates at which edge cracks begin to occur in cold rolling when the true density ratio in powder compacting is changed. It is the same iron powder as the original, the average particle size is 63μ, and the plate thickness at the time of powder compaction is also the same as 2.5Ri+. Furthermore, the atmosphere, temperature, and time conditions for sintering are also the same. In sample No. 1, which had a low true density ratio of 57%, cracks were observed in the early stage of cold rolling, but the true density ratio was 91%.
In sample No. 4, which had a high density, this may be because excessive plastic deformation was applied during powder compaction, causing distortion, and cracks had already occurred in the compact, or because of the high density, the compaction Because the bore (gap) became a closed bore that was cut off from the outside air, the reduction of the oxide film on the surface of the metal powder due to the reducing atmosphere containing H2 during sintering did not proceed sufficiently within the short sintering time. The reason for this is not necessarily clear, perhaps because the bonding between the metal powders became insufficient, but cracks occurred at relatively small rolling rates. On the other hand, sample No. has a true density ratio in the range of 65 to 90%.

In samples No. 2, No. 3, cold rolling of 50% or more could be performed without generating cracks. In addition, in Fig. 2, the true density ratio is 59
An example (sample No. 5) is shown in which a powder compact of 100% was sintered for a long time of 60 ain. This is thought to be due to the fact that sufficient time is available for the sintering to proceed, but cold rolling is now possible to a much higher rolling rate than in the case of short-time sintering.

As mentioned above, when sintering a belt-shaped powder compact in a short time continuously, in order to obtain sufficient sintering results, the average particle diameter of the metal powder and the true density ratio at the time of powder compaction are It has been found that controlling this is extremely important for improving the subsequent cold rolling properties of the sintered body.

An actual example carried out by the present applicant is as follows.

(Example 1) With the chemical composition shown in Table 1, a belt-shaped powder compact with a plate thickness of 2.5zt was manufactured using stainless steel powder manufactured by a water atomization method. The average particle size of the powder was changed by changing the powder manufacturing conditions and performing a classification operation. Further, a horizontal double rolling mill was used for powder compaction, the rolling speed was set to 2/1n, and the true density was varied by changing the powder compaction conditions.

Table 1 Table 2 The strip-shaped compacted compact was directly introduced into a continuous heating furnace heated to 1200°C, heated and cooled, and then wound onto a reel to form a strip-shaped sintered compact. Manufactured. (Inventive Examples 1 to 4, Comparative Examples 3 to 5) In sintering using a continuous heating furnace,
The compact was able to be soaked at 1200° C. for about 71 nm. Note that the atmosphere in the heating furnace was 75% H2 to 25% N2.

Separately, the strip-shaped powder compact was cut into short plates without being introduced into a continuous heating furnace, and heated to 1200°C in a batch heating furnace.
Sintering was performed by heating at −60 m1r+ to produce a short plate-shaped sintered body. (Comparative Example 1.2) The heating atmosphere was the same as in the case of a continuous heating furnace.

The above band-shaped sintered body and short plate-shaped sintered body were rolled with a roll diameter of 35 mm.
It was cold rolled in a cold rolling mill of 0.0 mm, and the occurrence of cracks was observed.

The results are shown in Table 2, which also lists the average particle size of the powder, true density ratio of the powder compact, and sintering conditions. In both Comparative Examples 1 and 2, which were sintered for a long time, a sufficient sintering effect was imparted, so that cold rolling at a rolling reduction of 47% or more could be performed without generating cracks. On the other hand, the average particle size and true density ratio of the powder compact are outside the range of the method of the present invention, and the manufacturing conditions up to compaction are the same as those of Comparative Examples 1 and 2 for powder, and only sintering is performed. In Comparative Examples 3 and 4, in which a continuous heating furnace was used for a short time, cracks began to occur at 29% and 27%, and cold rollability decreased. Moreover, in Comparative Example 5, where the true density ratio during powder compacting is higher than the range of the method of the present invention, cracks begin to occur at 11%, and good cold rollability cannot be obtained.

On the other hand, it can be seen that Examples 1 to 4 of the present invention, which are sintered bodies manufactured by the method of the present invention, have cold rollability comparable to those that have been sintered for a long time.

(Example 2) Bronze powder having the chemical composition shown in Table 3 and produced by the water atomization method was used to produce a plate with a plate thickness of 2. By carrying out the 0 classification operation in which a band-shaped powder compact of Ozt was produced, the average particle size of the powder was changed, and the true density ratio of the powder compact was also changed. Further, the powder compacting was followed by sintering, and then wound up on a reel to produce a band-shaped sintered body. (Example 5 of the present invention
．． 6. Comparative Example 6.7) The apparatus used for compaction and sintering was the same as in Example 1, and the atmosphere in the furnace was also the same.

Table 3 Table 4 In the above example, the compaction and sintering speed was 3.
．． 5z/5hin, the temperature of the sintering furnace is 850°C,
The powder compact was soaked for about 4 sins at 850°C.

The obtained sintered body was cold rolled in the same manner as in Example 1,
The cold rollability was investigated by observing the occurrence of cracks.

The results are shown in Table 4. From this table, as in the case of Example 1, the band-shaped sintered body produced by the method of the present invention does not control the particle size of the powder or the true density ratio of the compacted compact. It can be seen that the cold rollability is superior to that of the case.

[Effects of the Invention] As described above, the strip-shaped sintered body produced by the method of the present invention has excellent cold rolling properties, so there is no need to add a trimming process to remove cracks in the cold rolling process after sintering or to reduce the yield. , as well as an increase in the number of annealing operations, making it possible to efficiently produce a strip-shaped cold-rolled plate. By being able to efficiently manufacture strip-shaped cold-rolled sheets based on metal powder,
It can be said that the present invention makes an extremely large contribution to the manufacture of plate products made of materials that are difficult to process.

The band-shaped sintered body produced by the method of the present invention has improved formability not only in cold rolling but also in other forms, and is therefore effective in applications where the band-shaped sintered body is directly formed.

[Brief explanation of drawings]

FIGS. 1 and 2 are characteristic diagrams showing the relationship between crack length and cold rolling rate in the method for manufacturing a band-shaped metal sintered body according to the present invention.

Claims (1)

[Claims] In a method for manufacturing a band-shaped metal sintered body, which comprises a step of compacting metal powder into a continuous band shape, sintering it using a continuous heating furnace, and winding it up, the average particle size of the metal powder is 100 μm. A method for manufacturing a band-shaped metal sintered body, characterized in that the true density ratio in powder compacting is 60 to 90%.