JPS63255342A - Wire for dot printer - Google Patents

Abstract

PURPOSE:To obtain a lightweight wire for a dot printer having high wear resistance and toughness by using a powdery high-speed tool steel contg. a specified percentage by area of unsolid solved carbide dispersed uniformly in the hardened and tempered matrix. CONSTITUTION:A wire for a dot printer is made of a powdery high-speed tool steel contg. >=25% by area of unsolid solved carbide dispersed uniformly in the hardened and tempered matrix. Since the wire has high wear resistance and toughness and is light in weight, increased printing speed and prolonged service life can be ensured. A chemical compsn. consisting of 1.1-4.0% C, <=1.5% Si, <=1.0% Mn, 3.0-8.0% Cr, <=20.0% W, <=15.0% Mo (15%<=W+2Mo<=35%), 3.0-16.0% V, <=16.0% Co and the balance Fe with inevitable impurities or further contg. <=0.2% N is suitable for the wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing wire used in a dot matrix printer head.

[Conventional technology]

Currently, the following three material characteristics are required for printing wires used in dot matrix printer heads.

1. The wire has high wear resistance. The tip of the wire also hits the ink ribbon with a 10" recovery ball, so the tip wears out.
Printing becomes unclear. Furthermore, since the wire is constantly sliding against the guide, the side surfaces of the wire are worn out, which causes printing accuracy to deteriorate.

2. The wire must be lightweight. The printing wire must move at high speed, and in order to increase the printing speed,
It is necessary that the wire be lightweight.

3. The wire has high tenacity. Since the wire is arranged in a curved manner by an intermediate guide, it is easily broken during wire assembly or printing, so it is necessary to use a material with high toughness.

Conventionally, this type of printing wire generally uses a cemented carbide thin wire, a tungsten thin wire, a high-speed tool steel thin wire, or the like. Among these, cemented carbide has excellent wear resistance, but its high specific gravity makes the wire heavy, making it unsuitable for high-speed printing. Also,
It also has low toughness, so it may break during use or assembly, making it unsatisfactory in terms of reliability.

Fiber & II! Tungsten has a high specific gravity and is processed through strong plastic processing! ! A is likely to develop and split into two pieces,
It has drawbacks such as insufficient wear resistance.

High-speed steel has a lower specific gravity, about half that of cemented carbide and tungsten, and has high toughness, and moreover) 1v700 ~
It has a high hardness of 900 and has an appropriate amount of undissolved carbide dispersed in it, so it has excellent wear resistance and is widely used as printing wire for dot printers. There are two types of high-speed tool steel: those manufactured using the normal melting process and those manufactured using the powder process.Powdered high-speed tool steel has higher wear resistance, however, as printing printers become faster and faster. In order to extend tool life, the wear resistance of conventional powder high-speed tool steels is still insufficient, and it is necessary to improve the wear resistance.

Techniques for improving the abrasion resistance of printing wires include 1, for example, as disclosed in Japanese Patent Application Laid-open No. 110121/1983,
A method of bonding a hard metal tip to the tip of a wire, a method of impact hardening the tip by laser irradiation as disclosed in JP-A-54-54713, JP-A-52-96
A method of coating the wire surface with a hard compound by chemical vapor plating, as disclosed in No. 119, has been proposed.

[Problem that the invention seeks to solve]

Among the conventional methods for improving the wear resistance of printing wires, there is a method of bonding a hard metal tip to the tip of the wire;
Methods such as impact hardening the tip using laser irradiation, coating the wire surface with a hard compound using chemical vapor plating, etc. are not suitable for mass production and are expensive, so they are currently not practical on an industrial scale. has not been converted.

In response to the above-mentioned conventional techniques, the applicant has proposed a method for improving the wear resistance of powdered high-speed tool steel by increasing the average particle size of undissolved carbides to 1.0μ or more (Japanese Patent Application Laid-Open No. 6
1-199055). Although this method is effective in improving wear resistance, it has been found that if the particle size is too large, there is a slight problem with drawing performance, and the wire may break during the drawing process for manufacturing fine wire. reached.

Therefore, the present invention suppresses breakage during the drawing operation of fine powdered high-speed tool steel wire used as wire for dot printers, and improves the wear resistance in a more economical manner, thereby making it possible to achieve higher speeds and longer lifespans. It is intended to provide a printing wire.

[Means for Solving the Problems] The present invention provides a method for uniformly dispersing undissolved carbide in an area ratio of 25% or more in a quenched and tempered matrix in a thin wire used as a printing wire for a dot matrix printer. The above-mentioned problem is solved by using a powdered high-speed tool steel.

The present invention will be explained in detail below.

As mentioned above, the inventor of the present application
In the wire made of powdered high-speed tool steel in which the average particle size of undissolved carbides is 1.0 μm or more, fractures occur during drawing operations, and this fracture is caused by undissolved carbides contributing to improved wear resistance. It was found that this phenomenon occurs when the particle size of the particles is too large. As a result of various studies on this point, we found that by setting the amount of the undissolved carbides to 25% or more in terms of area ratio, sufficient wear resistance can be achieved without excessively increasing the particle size of the undissolved carbides. The present invention was completed based on the finding that this can suppress breakage during the pulling operation.

Although it is not clear why the above effects are obtained when the amount of undissolved carbide is increased to 25% or more in terms of area ratio,
It is estimated that this is due to the following effects.

When powdered high-speed steel wire is used for printer wire,
Its wear resistance is due to the hardness of the tempered martensite base,
It can be considered that it is influenced by the distribution, size, amount, etc. of undissolved carbides. The undissolved carbide is a mixture of two types of carbide: M, C type and MC type, but the hardness of M and C type carbide is Hv 1600 to 2400, and MC type carbide is Hv 2500 to 3.
500, which is significantly harder than the hardness of the base Hv700-900. Therefore, the base of the wire first wears out due to contact with the ink ribbon or sliding with the guide, and the undissolved carbide remains floating and contributes to wear resistance, but eventually falls off as the base wear progresses. .

Figure 1 is a schematic diagram of this. When there are few undissolved carbides in (a), the area of tempered martensite is large and the distance between carbides is large, and due to this wear, the undissolved carbides fall off quickly. . When there are many undissolved carbides as in (b), the area of the tempered martensite is small and the distance between the undissolved carbides becomes small, making it difficult for this martensite to wear out and the undissolved carbides to fall off. (This is advantageous for wear resistance.

This is believed to be the reason why the wear resistance of the material of the present invention is superior to that of conventional powdered high-speed steel wire.

If the content of undissolved carbide is less than 25%, the above effects will not be noticeable, so in the present invention, the undissolved carbide is limited to 25% or more in terms of area ratio.

In addition, ordinary high-speed steel thin wire produced by melting does not have a uniform distribution of undissolved carbides, and is inferior in wear resistance and toughness, so that it does not satisfy the object of the present invention.

Therefore, in the present invention, powdered high-speed tool steel is used.The raw material powder for powdered high-speed steel is dispersed by high-speed Nz gas, water, etc. when molten steel is dropped through a narrow nozzle, and is rapidly solidified into powder. It is something that Therefore, the powder has an extremely fine solidified structure, and the powder high-speed tool steel manufactured from this powder has carbides uniformly distributed both inside and outside the steel material.゛The amount of undissolved carbide was limited to that at the time of quenching and tempering.For powdered high-speed tool steel fine wire, the amount of undissolved carbides is limited to that at the time of quenching and tempering. This is because the wire is hardened by being subjected to quenching and tempering heat treatment before being used as a dot wire.

The chemical composition of the powder high speed steel suitable for making the undissolved carbide of the fine powder high speed steel wire 25% or more and for other characteristics required for a dot printer is as follows.

That is, C1.1-4.0%, Si≦1.5%,
Mn≦1.0%, Cr3. 0-8.0%, WS20
．． 0%, Mo≦16.0% (however, 15%≦W+2M,
≦35), V3, 0-16.0%, Co≦16.0
%, the balance is Fe, or N is added in an amount of 0.2% or less. Furthermore, even if the material contains unavoidable impurities of other elements, the present invention will not be hindered.

The effects of each element will be described below.

C forms a carbide together with Cr, W, Mo, and V that are added at the same time, and some of the carbon forms a solid solution in the matrix, thereby having the effect of increasing wear resistance. Therefore, the content of C is not determined solely by Cr.

The appropriate amount should be determined in relation to the content of W, Mo, V, etc. In the content range of the above combination elements, C content is 1! t
If it is less than 1.1%, the hardness of the base will be low, the amount of undissolved carbide required by the present invention will not be obtained, and the wear resistance will be insufficient. On the other hand, if it exceeds 3.5%, it becomes extremely brittle, so the C content was set to 1.1 to 3.5%.

Si is added for deoxidation during refining and for the purpose of increasing the tempering hardness of the base. However, if it exceeds 1.5%, it becomes brittle, so Si≦1.5% was selected.

Like St, Mn is also added for deoxidation and to improve hardenability. However, if it exceeds 1.0%, the effect is saturated, so Mn≦1.0% was set.

Cr forms carbides and has the effect of increasing wear resistance, hardenability, and oxidation resistance. If Cr is less than 3%, this effect will not be sufficient, and if it exceeds 8%, the toughness will decrease, so Cr is set at 3.0 to 8.0%.

W and Mo form carbides to improve wear resistance, and some of them are solidly dissolved in the matrix to increase tempering hardness. Since No is about % of the atomic weight of W, Mo
1% has the same effect as W2%, W+2Mo1
You can see the effect in 1. WS20.0
%, in the range of Mo≦16.0%, W+2Mof
When i is less than 15%, there is no effect because the amount of carbide is small.

On the other hand, if W+2Mof exceeds 35%, the amount of carbides becomes too large and becomes brittle, so 15%≦W+2Mo≦35%
And so.

V also has the same effect as W and Mo. ■Content is 3
．． If it is less than 0%, the wear resistance will be low, and if it exceeds 16.0%, wire drawing will be difficult, so v3.0 to 16.0
%.

Co dissolves in the base and has the effect of increasing the hardness of the base, but if it exceeds 16.0% it becomes brittle, so Go≦16.0%.
And so.

N has the effect of forming nitrides with V to increase wear resistance, and has the effect of increasing base hardness by forming a solid solution in some bases, but 0
．． If it exceeds 2%, wire drawing becomes difficult, so if it is added, it should be 0.2% or less.

〔Example〕

Next, embodiments of the present invention will be described.

Fine powder high-speed steel wires having a wire diameter of φ0.3R shown in Table 1 were produced, and the amount of wear at the tip of the wire after a certain number of dots was measured using a printer wire life tester.

For each sample, N2 gas atomized powder was placed in a mild steel capsule, compacted using a hot isostatic press, soaked, hot rolled, and then cold drawn to a diameter of 0.3 m. After processing to the wire diameter, it was quenched and tempered.

The quenching temperature is 1190℃ for symbols A, B, and D, and 12℃ for symbol C.
00℃, tempering at 550℃×(1+1+
1) Hr.

Hardness after quenching and tempering is symbol AHv965, symbol BH
v985, symbol CHv704, symbol DHv990.

When we conducted a printer wire life test using this wire material, the amount of wire tip wear after 50 million strokes was marked A.
30-40μ, symbol 820-30μ, symbol D20-30
It was confirmed that the wear resistance was superior to the conventional material C70 to 90μ in terms of μ.

In addition, no breakage occurred during the drawing operation in any of the samples A to D with the above symbols.

〔Effect of the invention〕

As described above, according to the present invention, the abrasion resistance of the wire for dot printers can be significantly improved, and since it is lightweight and has high toughness, it has a remarkable effect as a wire for high-speed, long-life printers.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the wear mechanism of printer wires having different contents of undissolved carbides. l: undissolved carbide, 2: tempered martensite base, a: when there is little undissolved carbide, b: when there is a large amount of undissolved carbide.

Claims (1)

[Claims] 1. A dot printer wire characterized by being made of powdered high-speed tool steel in which undissolved carbides are uniformly dispersed in an area ratio of 25% or more in a quenched and tempered matrix. . 2. Chemical composition: C1.1-4.0%, Si≦1.5%,
Mn≦1.0%, Cr3.0-8.0%, W≦20.0
%, Mo≦15.0% (however, 15%≦W+2Mo≦3
5%), V3.0 to 16.0%, Co≦16.0%, and the balance is Fe and unavoidable impurities. 3. Chemical composition: C1.1-4.0%, Si≦1.5%,
Mn≦1.0%, Cr3.0-8.0%, W≦20.0
%, Mo≦15.0% (however, 15%≦W+2Mo≦3
5%), V3.0-16.0%, Co≦16.0%, N
The wire for a dot printer according to claim 1, comprising ≦0.2%, the balance being Fe and unavoidable impurities.