JPH0347904A - Manufacture of strip-state porous metal plate - Google Patents

Abstract

PURPOSE:To execute mass-production of strip-state porous metal plate with good uniform quality by continuously forming a strip-state formed body having the specific void ratio from metal powder having the specific particle diameter and particle size distribution with twin rolls and continuously sintering this under non-oxidizing atmosphere. CONSTITUTION:The metal powder having particle size of the certain value in the range of 20 - 300mu average particle diameter and composing >=90% the total powder of particle diameter from 1/2 to 3/2 the above certain value, is continuously supplied between the twin rolls 6a, 6b arranged facing at the pre scribed gap from a hopper 7 to make the strip-state formed body 8 having the prescribed thickness and 10 - 50% the void ratio. Successively, this strip-state formed body 8 is introduced into heating zone 3 and cooling zone 4 in a continu ous sintering furnace 2 under non-oxidizing atmosphere in order, and sintered and cooled to wind this into a coiler 5. By this method, the porous metal strip having good gas permeability and excellent uniform quality can be continuously manufactured and is useful for metallic filter, sound absorber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a porous metal plate used for metal filters, sound absorbing materials, and the like.

[Conventional technology]

Conventionally, various porous metal materials using metal powder, metal fibers, metal foam, etc. have been used as metal filters, metal catalyst supporting substrates,
It is used for sound-absorbing materials, bearings, etc. Among these, sintered metal powder is the most widely used.

As a method for manufacturing porous materials by sintering metal powder,
A common method is to form the powder into a mold and then sinter it into a product. Mold forming methods include a pressureless sintering method in which metal powder is filled in a mold and sintered without applying pressure, a method in which metal powder is pressurized with a press to form a compact, and then sintered.
There is a method of adding pine goo to metal powder, forming it into a slurry, and sintering this.

[Problem that the invention seeks to solve]

The most common method for obtaining plate-shaped products of porous metal materials was to press them into plate-shaped compacts and then sinter them. There were problems such as the equipment becoming larger and the size of the product being limited. In addition, since pressing and sintering are done in a batch process, production efficiency is low and quality control to produce uniform products is a heavy burden, which poses problems in mass production using a line process. Although this method has the advantage of being able to mold into articles close to the shape of the final product, it has the inherent drawback that it is difficult to mold thin objects using molding, so the porous material obtained is limited to relatively thick objects. It also included the issue of being exposed.

On the other hand, the pressureless sintering method has the problem that the strength after sintering is low because there are few contact points of the metal powder, and the advantage of metal materials, which are higher strength than organic porous materials, cannot be demonstrated. In addition, methods using binders have problems such as deterioration of the material due to contamination with impurities and the need for degreasing, which complicates the manufacturing process.

The present invention has been made with the aim of solving such problems.

[Means to solve problems]

The inventors of the present invention have found that even if a method is adopted in which metal powder is compacted into a continuous band-shaped compact by powder rolling, it is possible to roll the metal powder so that the predetermined particle size and particle size distribution are appropriate and have a predetermined porosity. We have discovered that if we do this, we can obtain a strip with a self-supporting strength that allows for continuous threading, and that we can produce a strip-shaped porous metal coil by continuous sintering in a sintering furnace. That is, the present invention continuously supplies metal powder between two rolls that rotate in opposite directions and are arranged facing each other with a predetermined gap between them, so that the metal powder has a thickness corresponding to the gap between the rolls and a porosity of 10 to 50%. To provide a method for producing a strip-shaped porous metal plate, which comprises forming a strip-shaped compact, and subsequently passing the strip-shaped compact through a continuous sintering furnace maintained in a non-oxidizing atmosphere to sinter and cool it. It is something. At that time, the metal powder to be fed to the twin rolls should have an average particle size of 2
It is best to use a powder that has a certain value within the range of 0 to 300 μm and has a particle size distribution in which 90% or more of the total powder falls within the particle size range from 1/2 to 3/2 of that certain value. good.

[Detailed description of the invention]

FIG. 1 shows an outline of the equipment for carrying out the method of the present invention. 1 is a powder rolling mill, 2 is a continuous sintering furnace, in which a heating zone 3 is formed at a predetermined distance from the inlet side of the strip-shaped material passing through it, and a cooling zone 4 is formed next to it. . 5
indicates a winder. In the illustrated example, the twin-roll powder rolling mill consists of twin rolls 6a and 6b that are arranged opposite to each other with a predetermined gap and have horizontal axes that rotate in opposite directions. Powder is continuously fed from the hopper 7. At that time, by appropriately controlling the rolling speed and the amount of metal powder supplied to the roll gap set to a predetermined value, the roll has a thickness corresponding to the roll gap from the narrowest part of the roll and a porosity of 10 to 10. A 50% continuous strip shaped body 8 is produced. This strip-shaped compact 8 is then continuously passed through the sintering furnace 2.

Sintering is completed while passing through the heating zone 3, and then it is continuously cooled in the cooling zone 4 and exits the furnace to become a porous product strip that is wound up on three winders.

According to the invention, such an installation makes it possible to continuously produce, for example, gas-permeable porous metal sheets. At that time, powder rolling machines do not have friction between the mold and metal powder as in press forming, so powder compacting can be performed efficiently with less energy, and the plate thickness can be increased without using forming aids such as binders. It can be compacted relatively easily into a product as thin as 0.5 mm, and strip-shaped molded products can basically be manufactured continuously without any length limitations.

In carrying out the present invention, the type of metal powder used is not particularly limited, but one suitable powder is water atomized powder, which is inexpensive and has relatively good moldability.

Although the type of metal is not particularly limited, 1. The method of the present invention is excellent in mass productivity, so its advantages are demonstrated in the case of general-purpose metals such as steel and copper alloys. 2. For example, in cases where corrosion resistance is required, Stainless steel powder is used.

The particle size of the powder determines the size of the voids in the porous metal plate product, and is also important for obtaining a strip-shaped molded product with self-supporting strength, so it is necessary to select it appropriately. According to the test results conducted by the present inventors, the 2-average particle size has a certain value within the range of 20 to 300 μm, and the entire particle size range is from 1/2 to 3/2 of that certain value. powder 9
It has been found that it is necessary to have a particle size distribution to which 0% or more belongs. In the case of fine powders with an average particle size of less than 20 μm, the fluidity of the powder decreases and the tap density decreases, making it difficult to form by rolling, as well as the porosity of the product plate. Problems also arise, such as the voids that characterize the W'FA becoming so fine that it loses its properties as a porous W'FA, and the manufacturing cost of the metal powder increases. On the other hand, if the average particle size exceeds 300 μm, the formability decreases, making it difficult to create a strip-shaped powder compact with self-supporting strength by rolling, and even if it can be created, the strength after sintering will decrease. The problem arises that the

On the other hand, the particle size distribution of the metal powder must be appropriately adjusted since it affects the formability in powder rolling and the quality of the product porous metal plate. If powders that are significantly finer or coarser than the average particle size are mixed, the strength of the thin strip-shaped molded product will be uneven in some places during powder rolling, and the porosity distribution will be biased, resulting in poor formability. Moreover, the distribution of the pore diameters of the obtained porous metal plate also becomes uneven. For example, when using the porous metal plate obtained by the present invention as a metal filter, in determining the grade of the metal filter, it is necessary that the pores be uniform to a certain extent, and this allows the size of the material to be filtered out to be determined. You will be able to decide. The particle size distribution of such metal powder that does not have problems in terms of formability and quality is based on the results of numerous tests conducted by the present inventors. It has been found that it is desirable that the ratio is 90% or more. That is, the average particle size is <20 to 300 μm as described above.
Using a powder with a certain value within the range of
% or more is used. For example, even if the average particle size is in the fine range of 20 to 30 μm, if the proportion of powder that is significantly finer or coarser than this is large, the pore size may become too small or the moldability may deteriorate. Become. For this reason, it is necessary to avoid mixing in fine powder or coarse powder that deviates too much from the average particle size. Note that, depending on the type of metal powder, when using a metal powder that has particularly poor formability even within the particle size and particle size distribution ranges mentioned above, treatment to improve the formability by pre-mixing a binder as a forming aid, etc. It is also possible to produce a porous sintered metal plate by the method according to the present invention.

In a powder rolling mill, such a metal powder is used to continuously produce a strip-shaped compact having a porosity of 10 to 50%. The porosity is controlled by appropriately controlling the roll gap in the powder rolling mill, the rotational speed of the rolls, and the powder supply speed depending on the metal powder used. The porosity of the strip-shaped compact is approximately equal to the porosity of the sintered product. Therefore, the porosity during rolling is determined to a certain value within the above range depending on the required characteristics of the product. If the porosity of the band-shaped body is less than 10%, the absolute amount of voids is small (inner voids do not penetrate to the surface, so-called closed bore state, and the product after sintering does not pass through. Not only does it lose its porous property (for example, it cannot be used for filters, etc.), but it is also necessary to forcibly increase the amount of powder fed into the roll gap of a twin-roll powder rolling mill.
Therefore, special consideration must be given to steady-state operation, making it difficult to stably produce porous and uniform products.

On the other hand, if the porosity of the strip-shaped compact exceeds 50%, the strength of the strip-shaped compact decreases significantly, making it difficult to form a strip that can self-support, making it difficult to stabilize the strip-shaped compact. Therefore, it becomes impossible to continuously pass the sheet through the continuous sintering furnace. For this reason, it is desirable that the porosity in compacting is in the range of 10 to 50%.

The strip-shaped molded product rolled in this way is as follows.

While maintaining this flow, it is continuously guided to a continuous sintering furnace, where it is heated and cooled in a non-oxidizing atmosphere. In general, when compacted products are heated in an oxidizing atmosphere such as the air, oxidation occurs, which not only makes it difficult for sintering to occur, which is a bonding phenomenon between metal powders due to the diffusion of metal atoms at the metal powder interface, Scale forms on the product surface and the product value is lost. Therefore, the atmosphere during heating and cooling in the sintering furnace is H2 and C.
It is necessary to maintain a non-oxidizing atmosphere using a reducing gas containing O or an inert gas such as Ar. As mentioned above, in the heating zone in the sintering furnace, it is necessary to select a temperature that will cause bonding at the portions where the metal powders come into contact with each other during powder compaction. This temperature varies depending on the type of metal powder and the powder rolling conditions, but for example, in the case of steel, it is necessary to set the heating temperature to 800'C or higher, and in the case of copper alloy, it is necessary to set the heating temperature to about 500'C or higher. Due to the continuous sintering in which the product is passed through the sintering furnace in a continuous flow, the sintering time is relatively shorter than in the case of H/7T sintering, so that sufficient sintering and therefore sufficient product can be achieved. In order to obtain strength, it is desirable to set the heating and holding temperature higher than in the case of normal batch sintering.After sintering in the heating zone, it is cooled,
This cooling is also preferably performed in the furnace. This is because oxidation progresses even during cooling, and scale formation, etc., occurs in the same way as during heating. Therefore, it is necessary to cool the furnace in a non-oxidizing atmosphere to a low temperature at which oxidation does not significantly proceed.

The strip-shaped sintered body discharged from the continuous sintering furnace can be cut into plates by shearing or the like, but it can also be made into coil-shaped metal strips by using a winder. By making it into a coil, it can be processed in the same way as regular metal strips, including skin pass rolling and trimming for subsequent shape correction, as well as secondary processing such as jarring and punching.9 This makes manufacturing efficient. is possible.

[Example 1] A porous sintered metal plate was manufactured using stainless steel metal powder having a composition of 5US304L according to the JIS standard.

All of the powders used were water atomized powders, and the average particle size and particle size distribution were adjusted by classification.

1 2 No binder was added. A rolling mill with a roll diameter of 400 mm was used for powder rolling, and the powder was compacted with a porosity of 8 to 60%, a plate thickness of 0.5 to 2.0 mm, and a plate width of 180 mm to obtain a strip-shaped compact. This continuous strip-shaped compact was directly passed through a continuous sintering furnace and sintered. The atmosphere in the heating zone and the cooling zone was ammonia decomposition gas, and the heating conditions in the heating zone were 1200"C and held for 5 minutes and 6 minutes. Also, the temperature at the outlet of the continuous sintering furnace was 150"C.
Cooling was performed in a cooling zone so that The cooled sintered body was wound into a coil with an internal diameter of 508 mm.

The pore diameter and pressure loss when air was passed through the samples collected using these coils were measured. The results are shown in Table 1. Examples of cross-sectional observations are shown in FIGS. 1 and 2.

14 As is clear from Table 1, the average particle size of the powder is 300μ
Comparative example 1 exceeding m. Comparative Example 2, in which the average particle size is 300 μm or less, but 10% or more of the powder has a particle size exceeding 300 μm. and Comparative Example 4 in which the porosity of powder molding exceeds 50%, the strength of the molded body is low in both cases.
The molded body could not be stably introduced into the continuous sintering furnace, and a sintered body could not be obtained. In other comparative examples, a sintered body as a coil was obtained, but in Comparative Example 3, the porosity of powder compacting was less than 10%. In Comparative Example 5, in which the average particle size is 20 μm or more, but the powder with a particle size of less than 20 μm accounts for 10% or more, there are few voids or the size of the voids is small, so the pressure loss when passing through air is It was extremely large, and its function as a porous material was limited.

On the other hand, in Examples 1 to 6 of the present invention, typical cross-sectional structures are shown in Fig. 2 (porous sintered metal plate of Inventive example 1) and Fig. 3 (porous sintered metal plate of Inventive example 4). As shown in the board),
A porous sintered metal plate having an average pore diameter of 10 to 18 μm was obtained, and sufficient ventilation was possible. therefore,
A porous metal plate suitable as a filter material or catalyst carrier substrate was obtained.

[Example 2] From the coils of Examples 1 and 4 of the present invention manufactured in Example 1,
A tensile test piece of JI No. 56 was cut out by cutting and tested. In addition, as a comparative example, a sintered plate was manufactured using conventional press molding and batch sintering. The metal powder used for this was the same 5US3 as used in Example 1.
04L water atomized powder, average particle size is 125μ
It is m. For manufacturing, the width is 15mm and the length is 100m.
A molded body having a plate thickness of 2.0 mm and a porosity of 32% was made using a press load of 60 tons using a rectangular mold of size 2.0 mm, and this molded body was subjected to hatch sintering at 1150° C. for 60 minutes. A JIS No. 6 tensile test piece was cut out from this rectangular sintered plate and tested. The pore diameter and pressure loss during ventilation were also measured. The results are shown in Table 2.

As shown in Table 2, all of the examples of the present invention have strength equal to or higher than the comparative examples of porous sintered metal plates manufactured in a conventional batch manner, and they are also inferior in ventilation characteristics. It can be seen that there is no porosity and that the material can be sufficiently applied as a porous metal plate.

〔Effect of the invention〕

As described in detail above, according to the present invention, a gas permeable porous metal strip can be continuously produced. Therefore, compared to conventional batch-type methods, mass productivity is significantly improved, and product homogeneity is also excellent. In addition, by obtaining a coiled product, it is easy to apply it to applications that require a relatively large area, and it can be processed using the same method as ordinary metal strips, which significantly expands the application. It can be expanded to provide inexpensive, high-quality materials for fields such as filter materials, catalyst carrier substrates, and even sound-absorbing materials.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional system diagram showing an example of equipment for carrying out the method of the present invention, and FIGS. 2 and 3 are photographs showing the structure of a porous metal plate manufactured by the method of the present invention. The figure is a metallurgical microscope photograph of the metal plate obtained in Example 1, and FIG. 3 is a metallurgical microscope photograph of the metal plate obtained in Example 4. 1. Powder rolling mill, 2. Continuous sintering furnace. 3... Heating zone 4... Cooling zone 5... Winder, 6a, 6b... Twin rolls. 7. Hopper, 8. Band-shaped molded body. 7 8

Claims (4)

[Claims] (1) Metal powder is continuously supplied between two rolls that rotate in opposite directions and are arranged facing each other with a predetermined gap, so that the metal powder has a thickness corresponding to the gap between the rolls and a porosity of 10 to 50%.
1. A method for producing a strip-shaped porous metal plate, the method comprising: forming a strip-shaped compact, and subsequently passing the strip-shaped compact through a continuous sintering furnace maintained in a non-oxidizing atmosphere to sinter and cool the strip. (2) The metal powder supplied to the twin rolls has an average particle size of 20
~300 μm, and 1 of that value
2. The method for producing a strip-shaped porous metal plate according to claim 1, having a particle size distribution in which 90% or more of the total powder falls within a particle size range of /2 to 3/2. (3) The method for producing a strip-shaped porous metal plate according to claim 1 or 2, wherein the continuous sintering furnace comprises a heating zone and a cooling zone, and both zones are maintained in a non-oxidizing atmosphere. (4) Claim 1, wherein the metal powder is stainless steel powder.
, 2 or 3. The method for manufacturing a strip-shaped porous metal plate according to .