JPS61162367A - Guide plate for wire dot printer and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a guide plate having high dimensional accuracy and high service durability and abrasion resistance, by forming a guide plate from a composite body comprising a sintered porous body of silicon carbide with open pores filled with metallic silicon. CONSTITUTION:A silicon carbide powder, polyvinyl alcohol water solusion are mixed with each other in a ball mill, and the mixture is dried. An appropriate amount of the dried mixture is agglomerated, and the agglomerated material is molded by a metallic die. A multiplicity of such molded bodies are produced, are placed into graphite crucibles, and are fired in a Tamman furnace in an atmosphere consisting mainly of argon gas at 1atm. Open pores of sintered porous bodies of silicon carbide thus obtained are filled with metallic silicon to an extent of 95vol% to produce composite bodies, thereby obtaining guide plates.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a guide plate for a wire dot printer made of a composite in which the pores of a porous silicon carbide sintered body are filled with metallic silicon, and a method for manufacturing the same. In particular, the present invention relates to
A composite in which metallic silicon is filled in the air release holes of a porous silicon carbide sintered body having open pores, which is sintered without substantially causing shrinkage of the shape of the formed body formed into a predetermined shape. The present invention relates to a guide plate for a wire dot printer made from the present invention, and a method for manufacturing the guide plate at low cost and easily without substantially requiring finishing processing such as machining.

[Conventional technology]

Conventional guide plates for wire dot printers (hereinafter simply referred to as guide plates) are made of various plastic materials, glass photo-etched materials, alumina sintered bodies, ruby or sapphire, and the like.

In the print head of a wire dot printer, an impact wire generally made of a hard metal such as tungsten or tungsten carbide and having a circular cross section is provided toward a guide at the tip.

Therefore, the guide plate made of the plastic material suffers from significant wear and has a short service life, and the guide plate made of the glass photo-etched material is difficult to align the holes in a straight line, resulting in high cost. Not only is it expensive, but it also has the drawbacks of being easily damaged and having a short service life.

-4. Guide plates made from alumina sintered compacts, ruby, sapphire, etc. have relatively high hardness, so it is difficult to finish them by machining, etc. Not only is the cost expensive, but they are also relatively brittle. It has poor workability and is extremely difficult to drill independent circular holes at small intervals.

Furthermore, for example, according to Japanese Patent Application Laid-Open No. 56-89962, ``the base of a dot printer guide plate made of carbon is reacted with silicon oxide to convert the entire base to a silicon carbide layer, or the entire base is converted into a silicon carbide layer. "A guide plate for a wire dot printer, characterized in that the entire surface or a dispersed partial surface is formed with a silicon carbide layer."

The wire dot printer guide described above is used by the impact wire reciprocating by the solenoid F and sliding on the guide plate when printing, and the tip of the impact wire hits the ribbon to print characters. It is something that Since the impact wire operates very quickly and reciprocates many times, the guide plate is likely to wear out due to sliding of the impact wire. Also, the smaller the distance between the dots that make up one character, the easier it is to read, so the distance between the holes in the guide plate should be as small as possible.

JP-A-56-89962 discloses a converge run guide plate in which the entire or surface of the substrate is converted to silicon carbide by reacting silicon oxide with a carbon substrate. The reaction for converting the carbon substrate surface into silicon carbide is as follows.

2C+8i0→SiC+■ Therefore, it is generally difficult to adjust the size of SiC particles produced by the above reaction formula, and the produced 3i
Since the particles of C are thick (they grow and the surface particles become rough), it is not usable unless the inner surface of the hole is polished.

[Problem that the invention seeks to solve]

The present invention aims to eliminate and improve the drawbacks of the conventional guide plates made of various materials, and to improve the high dimensional accuracy, abrasion resistance, durable strength, and prevention of powder falling off during use, which are originally required for guide plates. The present invention provides a guide plate for a wire dot bunly made of a composite material in which the open pores of a porous repurchased silicon sintered body are filled with metallic silicon and has all of the various characteristics, and a method for manufacturing the same.

That is, for the above purpose, metal silicon is filled into the open pores of a silicon carbide sintered body, which is a porous body having open pores and is sintered in a predetermined shape without substantially shrinking during firing. The present invention provides a guide plate with high dimensional accuracy, excellent practical durability strength and wear resistance, and a method for manufacturing the same.

[Means for Solving the Problems] According to the present invention, a porous silicon carbide sintered body having open pores and sintered into a predetermined shape without substantially shrinking is used as a base material. need to do.

In general, silicon carbide sintered bodies have high hardness, high thermal shock resistance, and high strength at high temperatures, and have excellent wear resistance, oxidation resistance, and corrosion resistance, and have good thermal conductivity and low coefficient of thermal expansion. Because it has excellent chemical and physical properties, it is widely used as a wear-resistant sliding material for mechanical seals and bearings, and as a durable material for pump parts that require corrosion resistance.

However, silicon carbide sintered bodies having high hardness, like the alumina sintered bodies, ruby, or sapphire, have the disadvantage that they are difficult to finish by machining and are expensive. Especially for guide plates for wire dot printers, for example, the vertical dimension is 6wnx and the horizontal dimension is 3.
ff, the plate thickness is 1 ff, and as illustrated in Figures 1 and 2, the finishing cost is low for a plate with 9 to 24 holes with a diameter of 200 to 3000 μm. It has the disadvantage of being expensive.

Therefore, the present invention provides a silicon carbide sintered body sintered by a method that does not substantially cause firing shrinkage, that is, a porous body having open pores, and a first
A large number of molded bodies having the shapes and dimensions described above as illustrated in Figure 2 or Figure 2 are sintered in the predetermined shape with almost no sintering shrinkage, and then subjected to finishing processing such as machining. The base material is a porous silicon carbide sintered body that does not require substantially any porous material.

If such a silicon carbide sintered body is used as the base material of the guide plate, there is no need to finish finishing materials with relatively high hardness such as conventional alumina sintered bodies, ruby, or sapphire. The amount required can be manufactured at a low cost.

Further, the inherent properties of the silicon carbide sintered body itself, particularly its high hardness and excellent wear resistance, as well as its excellent corrosion resistance against ink and other chemicals, can be utilized as is.

Further, according to the present invention, it is necessary to provide a composite body in which the open pores of the silicon carbide sintered body sintered in the predetermined shape are filled with metallic silicon by a method such as impregnation. Metallic silicon is compatible with silicon carbide sintered bodies, and not only can it improve the durability and strength of the porous silicon carbide sintered bodies, but also metal silicon itself has excellent wear resistance and corrosion resistance. It can be used advantageously because of its characteristics.

The filling rate of the metal silicon is the open pores 10
Preferably, it is at least 50 parts by volume compared to 0 parts by volume. The reason for this is that if the amount of metallic silicon is less than 50 parts by volume, not only will the amount of printer ink that penetrates into the open pores of the porous silicon carbide sintered body become excessive, but also the durability of the silicon carbide sintered body will be reduced. This is because the strength cannot be sufficiently improved, the abrasion resistance cannot be improved, and powder falling off of the sintered body cannot be sufficiently prevented.

Further, it is preferable that the silicon carbide sintered body has an average grain size of crystals of 5 μm or less. The average particle size is 5 μm
This is because, if it exceeds this value, the surface roughness of the sintered body surface will increase, making it difficult for the guide plate surface to become smooth, and furthermore, the dimensional accuracy of the sintered body itself will deteriorate.

The density of the silicon carbide sintered body is 1.4 to 2-6.
Preferably it is f/c4. The density is 1.41
This is because a sintered body smaller than 7d has fewer bonding points between silicon carbide particles, making it difficult to make a sintered body with sufficient durable strength.On the other hand, a sintered body smaller than 2.6f/d This is because it is extremely difficult and impractical to obtain a density of the formed body corresponding to the density of the aggregate.

Next, a method for manufacturing a guide plate according to the present invention will be explained.

According to the present invention, a ceramic raw material containing silicon carbide powder as a main component is formed into a predetermined shaped formed body, and the formed formed body is
A porous material having open pores obtained by sintering in a non-oxidizing atmosphere controlled at a temperature range of 00°C to 2100°C with high dimensional accuracy without substantially shrinking the shape of the formed body. It is necessary to make a composite body in which the open pores of a silicon carbide sintered body are impregnated with metallic silicon.

The silicon carbide powder has an average particle size of 5 μm or less.
It is preferable to use type silicon carbide fine powder. The reason is 5.
Silicon carbide with a grain size larger than μm is preferable for suppressing firing shrinkage, but there are fewer bonding points between grains within the sintered body (this makes it difficult to obtain a high-strength silicon carbide sintered body). This is because it not only deteriorates the surface roughness of the surface.

Incidentally, the crystal systems of silicon carbide include α-type, β-type and amorphous, and according to the present invention, any of them or a mixture thereof can be used, and among them, β-type It is easy to obtain a powder having a diameter of 5 μm or less, which is the object of the present invention, in the form of a fine powder.

In addition, β-type crystals have relatively rounded particles, do not abrade the material of the sliding part, and have good surface roughness.

Moreover, it is possible to produce a sintered body with relatively high strength.
Among these, it is advantageous to use silicon carbide powder containing 50% by weight or more of β-type silicon carbide. Matoko, the starting materials are at least 6
1-; 1.1! of silicon carbide starting material containing 0% by weight of β-type, 2H-type and amorphous silicon carbide sintered body; :
It is advantageous to do so. The reason for this is that β-type crystals, 2H-type crystals, and amorphous silicon carbide crystals are low-temperature stable crystals that are synthesized at relatively low temperatures.
This is because not only does it easily undergo a phase transition to a high-temperature stable α-type crystal such as H, 6H or 15R type, forming plate-shaped crystals, but it also has excellent crystal growth properties.
It is advantageous to use a starting material consisting of more than 0% by weight of β-type silicon carbide.

Further, according to the present invention, the shrinkage rate due to the sintering is substantially 2% or less, and the composite body is made of a composite body with high dimensional accuracy and configured in a state that approximates the predetermined shape of the formed body. is preferred.

In other words, in order to obtain a sintered body with high dimensional accuracy as described above, the firing shrinkage rate when sintering without substantially shrinking is 2.
% or less, and more preferably 1% or less.

Further, the formed body is fired within a temperature range of 800 to 2100°C. In particular, when manufacturing a high-strength sintered body, firing is performed in an atmosphere where the partial pressure of at least one of CO or N2 in the atmosphere is maintained at 100 Pa or more at a temperature range of 1700 to 2100°C for at least 10 minutes. It is preferable that The reason is that the CO in the atmosphere is kept in the temperature range for at least 10 minutes.
Or at least the gas partial pressure of N2 is 100P
By making it more than a, the growth of the neck is promoted,
This is also because firing shrinkage during sintering of silicon carbide can be effectively suppressed.

It is advantageous for the silicon carbide sintered body of the present invention to be fired by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled. The reason why it is advantageous to charge the material into a heat-resistant container and fire it while controlling the firing atmosphere is that it can promote the bonding of adjacent silicon carbide crystals and the growth of necks. . The reason why bonding between adjacent silicon carbide crystals and neck growth can be promoted by charging the formed body into a heat-resistant container and firing while controlling the firing atmosphere as described above is because silicon carbide This is thought to be because movement of silicon carbide between particles due to evaporation-recondensation and/or surface diffusion can be promoted.

As the heat-resistant container, materials such as graphite and silicon carbide, and materials having functions equivalent to these materials can be advantageously used.

Furthermore, it is advantageous to control the volatilization rate of silicon carbide to 5% by weight or less during firing by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled and firing it.

Further, according to the present invention, the produced body has a particle size of 800 to 210
It is fired within a temperature range of 0°C. The reason for this is that if the temperature is lower than 800"C, it is difficult to sufficiently develop the necks that connect the grains, making it impossible to obtain a sintered body with high strength. On the other hand, if the temperature is higher than 2100"C Once a neck has grown, a neck smaller than a certain size becomes constricted, or in severe cases disappears, resulting in a decrease in strength, and some particles become coarser, causing the surface to deteriorate. This is because the surface roughness deteriorates.

Note that the formed body is fired in a non-oxidizing atmosphere without substantially shrinking. The reason is that shrinkage during sintering is desirable for improving the strength of the sintered body, but
Generally, the amount of shrinkage during sintering greatly affects the density of the formed body, so in order to generate uniform shrinkage, it is important to obtain a formed body with uniform density. but,
Since it is extremely difficult to obtain a green body with such uniform density, it is difficult to produce a sintered body with extremely high dimensional accuracy, which is the object of the present invention, by causing firing shrinkage. It is from.

Further, according to the manufacturing method of the present invention, it is advantageous that the formed body for manufacturing the silicon carbide sintered body has a density of 40 to 80% by volume.

The reason for this is that if the density of the formed body is lower than 40% by volume, there will be fewer points of contact between the silicon carbide particles, which will inevitably result in fewer bonding points, making it difficult to obtain a strong sintered body. Ah, on the other hand, because formed forms higher than 80% by volume are difficult to manufacture.

Note that, as long as carbides other than silicon carbide have a sintering mechanism similar to that of silicon carbide, it is possible to obtain a sintered body with excellent dimensional accuracy and strength as in the present invention.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

〔Example〕

Example 1 Silicon carbide powder used as starting material was 94.6% by weight
is a β-type crystal and the rest is a 2H-type crystal in terms of actual height, and 0.
29 wt% free carbon, 0.17 wt% oxygen, 0.0
It mainly contained 3% by weight of iron, 0.03% by weight of aluminum, and had an average particle size of 0.28 μm, and no boron was detected.

5N parts of polyvinyl alcohol and 300 parts by weight of water were blended with 100 parts by weight of the silicon carbide powder, mixed in a ball mill for 5 hours, and then dried.

An appropriate amount of this dry mixture was taken, granulated, and then molded using a metal mold at a pressure of 3000 kQ/d.

The dimensions of this generated feature are 6111 x 3 fl x thickness IM
So, the density is 2. Q f/cd (62% by volume). Then, nine holes with a diameter of 0.2 fl were drilled in the formed body using a carbide drill, as shown in FIG.

A large number of the above-mentioned green bodies were produced, placed in a graphite crucible, and fired in a Tammann-type firing furnace in an atmosphere of mainly argon gas at 1 atm. The heating process is 1 in 450°σ hours.
The temperature was raised to 900°C and maintained at the maximum temperature of 1900°C for 10 minutes. The CO gas partial pressure during sintering is from room temperature to 1700℃.
300±50 at temperatures below opa and higher than 1700℃
The argon gas flow rate was appropriately adjusted and controlled so that it was within the range of Pa.

The density of the obtained sintered body was 2.05 f/d, and its crystal structure, when observed using a scanning electron microscope, had a three-dimensional structure intricately intertwined in multiple directions. The rate is 0.25± in either direction.
Within the range of 0.02%, the dimensional accuracy of the sintered body is ±0.01
It was within 5fi. Further, the average bending strength of this sintered body was as high as 18.5#/-.

The open pores of the silicon carbide sintered body thus obtained were impregnated with 95% by volume of metallic silicon to obtain a composite, thereby obtaining a guide plate having a shape as illustrated in FIG.

The surface roughness of this guy plate was measured to be 2μmR.
max, and when this was temporarily used as a guide for a wire dot bunter, the conventional plastic guide plate was 1
．． 500 million dots, compared to 300 million dots for glass guide plates.

The guide plate of the present invention was found to have excellent durability, exceeding 500 million dots. As described above, according to the present invention, the durable use period such as wear resistance is approximately 2 to 3 times longer than that of the conventional method.

Example 2 The same operation as in Example 1 was repeated to produce a sintered body. The results are shown in Table 1.

As can be seen from the results shown in Table 1, the linear shrinkage rate is approximately 1,253±0.022% at the maximum, and according to the sintering conditions shown in Example 1, the linear shrinkage rate was 0.25%. It was confirmed that by shaping and sintering the formed body with the settings set to A guide plate of the present invention was obtained according to Example 1.
The usage results were also almost the same as in Example 1.

〔Effect of the invention〕

As described above, the silicon carbide sintered body for guide plates of the present invention is sintered without substantially shrinking, and is a composite whose open pores are impregnated and filled with metallic silicon. The guide plate made of this material has excellent dimensional accuracy and durable strength, and can be supplied at low cost without special machining.

[Brief explanation of the drawing]

1 and 2 are perspective views of a guide plate for a wire dot printer according to the present invention.

Claims (1)

[Scope of Claims] 1. A porous body having open pores, the open pores of which are sintered into a predetermined shape without substantially shrinking, and the open pores of which are filled with metallic silicon. A guide plate for wire dot printers made of a composite material. 2. The silicon carbide sintered body has an average crystal grain size of 5.
The guide plate according to claim 1, which has a density of 1.4 to 2.6 g/cm^2 in micrometers or less. 3. The filling rate of the metal silicon is the open pores 100
The guide plate according to claim 1, wherein the guide plate is at least 50 parts by volume. 4. A ceramic raw material containing silicon carbide powder as a main component is formed into a predetermined shape, and the formed body is heated at 800°C to 21°C.
A porous silicon carbide material having open pores obtained by sintering the formed body with high dimensional accuracy without substantially shrinking the shape and dimensions of the formed body in a non-oxidizing atmosphere controlled at a temperature range of 0.000C. A method for manufacturing a guide plate for a wire dot printer, characterized in that the guide plate for a wire dot printer is made from a composite body in which the open pores of a sintered body are impregnated with metal silicon. 5. The manufacturing method according to claim 4, wherein the silicon carbide powder is β-type silicon carbide fine powder having an average particle size of 5 μm or less. 6. The shrinkage rate due to the sintering is substantially 2% or less, and the composite body is made of a highly dimensionally accurate composite body that approximates the predetermined shape of the formed body. Manufacturing method described.