JPS61261453A - Cermet for wire dot printer and wire for dot printer - Google Patents

Abstract

PURPOSE:To provide the titled cermet and the titled wire having excellent bending strength and small specific gravity by forming the same of a hard phase consisting of TiC and N expressed by the specific chemical formula and binder phase consisting of a specific weight ratio of Fe and Ni. CONSTITUTION:The titled cermet is constituted substantially of 30-90wt% hard phase expressed by the chemical formula TiCxN1-x (0.1<=x<=0.95), 5-30wt% Mo2C and 5-40wt% binder phase consisting of Fe and Ni at 1.0-4.0 weight ratio (Fe/Ni). The titled wire is formed of such cermet. The cermet of this invention and the wire made thereof has the substantial bending strength and wear resistance. The cermet and wire have the small specific gravity and have therefore many effects including the extended life of a dot printer, the increased speed thereof, etc. The examples of the properties of the above- mentioned cermet and wire (* mark) are tabulated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cermet that has excellent bending strength and low specific gravity and is used for dot printer wire, and a dot printer wire manufactured using this cermet. .

[Conventional technology]

Conventionally, powdered high speed steel has been mainly used for dot printer wires, such as the one disclosed in Patent Publication No. 58-175673. However, dot printer wires made from this powdered high speed steel have poor wear resistance. However, it was still insufficient, and there was a limit to the period of use.

For this reason, attempts have been made to use cemented carbide or cermet, which have excellent wear resistance.

[Problem that the invention seeks to solve]

However, since cemented carbide has a high specific gravity and cermet has low bending strength, it has been difficult to apply them to wires for dot printers, which reciprocate at high speed while being subjected to bending action.

The object of the present invention is to improve the whitening strength, which was a problem with conventional cermets, to make them suitable for wires for dot printers, and to provide wires for dot printers using this cermet. be.

[Means for solving problems]

The cermet for wire dot printers of the present invention has the chemical formula T 1CxN 1-x (where 0.1≦x≦
0.95) hard phase expressed as 30-90%1 (wt%
, hereinafter the same), Mo2C5-30% by weight, Fe and N
i and its weight ratio (Fe/Ni) is 1.0-4
．． The wire for dot printers is made by molding a cermet having the above composition.

[For production]

Conventional cermets have a transverse rupture strength value of only about 200 kg/mm" when manufactured through normal processes, apart from experimental values under specially controlled conditions.
However, it was confirmed that the cermet of the present invention exhibits a transverse rupture strength value of 300 kg/-12 or more.

The reason why such a high transverse rupture strength value is exhibited is that the binder in the present invention 1 is a Fe--Ni binder.

In other words, although there are some differences depending on manufacturing conditions,
The weight ratio of Fe to Ni (F e/N i ) is 1.
If it is in the range of 0 to 4.0, the binder after sintering and cooling will exist in an austenite phase when no external stress is applied, and when further external stress is applied, the austenite phase changes to martenite. It was found that there is stress-induced transformation into the site phase.

The present inventors further conducted a detailed study on this stress-induced transformation behavior and found that by causing the binder to undergo stress-induced transformation, the transverse rupture strength can be dramatically improved.

The reason is that the binder near the stress concentration field at the tip of the crack generated by external stress is martensite I! It is presumed that the local volumetric expansion at this time prevents the growth of cracks.

If the Fe/Ni ratio of the binder phase exceeds 4.0, the amount of austenite phase remaining after sintering and cooling will be small, making it impossible to improve the self-strength.

Furthermore, when Fe/Ni is less than 1.0, the bending strength is lowered, although the reason is unknown.

Further, if the total amount of Fe 2 +Ni in the binder phase is less than 5%1, satisfactory bending strength cannot be obtained, and if it exceeds 40%, the abrasion resistance is poor and it cannot be applied to wires for dot printers.

The hard material of the cermet of the present invention is mainly composed of TiCxNtx and MozC. Since this T1CN has a relatively small density of around 5 g/Cm', it can sufficiently follow the speed increase of dot printers which are influenced by inertial force.

In the chemical formula TiCxN+-, X is 0.1≦x≦0.
95 is because, as is well known, when x < 0.1, nitrogen dissociates rapidly near the sintering temperature, making it difficult to obtain a sintered body with a sufficiently high density. This is because the effect of suppressing nitrogen grain growth is small and sufficient bending strength cannot be obtained.

As is well known, M O2C improves the wettability of the hard phase and binder in cermets. However, M O2
If the C content is less than 5%, the effect of improving wetness is small (if it exceeds 30%, a decrease in bending strength is observed. Therefore, Mo2
C was set at 5 to 30%.

Furthermore, depending on the type of ink, corrosion resistance may become a problem. In this case, addition of Cr or Ru is effective in improving this. Further, in this case, a compound containing Or* or Ru may be added.

When adding Cr, it is desirable to add Cr in an amount of 1 to 20% based on the total amount of Fe+Ni in the binder.

In other words, if it is less than 1%, there is little effect on improving corrosion resistance;
If it exceeds 0%, sufficient bending strength cannot be obtained.

When Ru is added, it is desirable to add Ru in an amount of 0.05 to 5% based on the total amount of Fe+Ni in the binder.

That is, if it is less than 0.05%, there is little effect on improving corrosion resistance, and if it exceeds 5%, sufficient bending strength cannot be obtained.

〔Example〕

Hereinafter, the test results of the cermet dot printer wire of the present invention and a comparison wire will be compared and explained.

The raw material powder was mixed and pulverized for 96 hours using Ball Mill/L, 1 to have the composition shown in Table 1, and after adding a plasticizer, kneading was carried out.
Extrusion molded to 0.5 mm, degreased to 1250~
A wire was prepared by sintering at 1400° C. for 30 minutes, and this wire was centerless ground to a diameter of 0.31 to form a wire for a dot printer.

The physical properties of these wires are also listed in Table 1.

Transverse rupture strength is the result of a three-point bending test with a span distance of 10 mm.

Next, with a cantilever, the amplitude is 41.50 Hz, and the stress is 150 kg.
The fatigue test was performed 10 times at 1000 ms/am'', and the average value of the number of fatigue failures was determined.

This is shown in Table 2.

A mounting test was also conducted, and the amount of wear 2 at the tip of the wire 1 at the position shown in FIG. 1 was measured.

The results are also summarized in Table 2.

Table 2 Table 2 (Continued) Table 2 (Continued) From the above results of the wire of the present invention, it can be concluded that the cermet wire for dot printers of the present invention can clearly improve wear resistance without deterioration of toughness. it is obvious.

The specific gravity of the alloy of the present invention is 9.5 g/Cm' or less, which is about half that of conventional WC-based cemented carbide, and can sufficiently follow the speed increase of dot printers in the future.

〔Effect of the invention〕

As mentioned above, the cermet of the present invention and the wire using the same have sufficient bending strength, are excellent in abrasion resistance, and have a small specific gravity, so they contribute to a longer life and higher speed of dot printers, etc. It has the following effects.

[Brief explanation of drawings]

FIG. 1 is an enlarged front view showing the state of wear at the tip of the wire. 1: Wire 1 agent patent attorney Takashi Honma ~/Wire

Claims (4)

[Claims] (1) Chemical formula TiC_xN_1_-_x (however, 0.
1≦x≦0.95), 30 to 90% by weight of the hard phase, 5 to 30% by weight of Mo_2C, Fe and Ni.
5 to 40% by weight of a binder phase whose weight ratio (Fe/Ni) is 1.0 to 4.0.
A cermet for wire dot printers, which is characterized by containing unavoidable impurities. (2) A cermet for a wire dot printer according to claim 1, characterized in that 1 to 20% by weight of the total amount of Fe and Ni in the binder phase is replaced with Cr metal. (3) A cermet for a wire dot printer according to claim 1, characterized in that a total amount of 0.05 to 5% by weight of Fe and Ni in the binder phase is replaced with Ru or a compound containing Ru. (4) Chemical formula TiC_xN_1_-_x (however, 0.
1≦x≦0.95), 30 to 90% by weight of the hard phase, 5 to 30% by weight of Mo_2C, Fe and Ni.
The weight ratio (Fe/Ni) is 1.0 to 4.0.
A wire for a dot printer, characterized in that it is formed from a cermet comprising 5 to 40% by weight of a binder phase and other unavoidable impurities.