JPH0519908B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a dot wire for dot printers that has excellent wear resistance and chipping resistance. [Prior Art] Conventionally, high speed steel and cemented carbide are mainly used for dot wires. High speed steel has poor abrasion resistance compared to cemented carbide, and has the disadvantage that printed characters and symbols tend to become blurred when used for a long time, so cemented carbide is increasingly being used for dot wires. On the other hand, although cemented carbide has excellent wear resistance, it is less tough than high speed steel and may break. [Problems to be Solved by the Invention] The purpose of the present invention is to improve fracture resistance, which is a drawback of cemented carbide, and to provide a high-performance fine-grained cemented carbide dot wire with excellent fracture resistance. shall be. [Means for solving the problem] The hardness of cemented carbide depends on the average interparticle distance of the binder phase, and the smaller the average interparticle distance, the harder it becomes.
Therefore, when comparing the hardness of cemented carbide with the same amount of binder phase, the finer the grain size of the carbide, the smaller the distance between carbides, and accordingly the average distance between particles of the binder phase becomes smaller, making it harder. Therefore, when the carbide grain size is made finer, the amount of binder phase can be increased to achieve the same hardness level, and the toughness of the alloy can thereby be significantly improved. Moreover, when the binder phase is Fe-Ni based, further improvement in toughness is observed. By making the grains finer in this way, it is possible to increase the amount of binder phase and greatly improve toughness, so carbides, nitrides, and carbonitrides can be deposited on the surface, which could not be used as a cause of toughness deterioration in the past. coating is also possible, and wear resistance can be significantly improved without deteriorating breakage resistance. Next, we will explain the reason for limiting the numerical values. If tungsten carbide is contained less than 50%, the desired wear resistance cannot be obtained, and if it is contained more than 90%, chipping is more likely to occur due to deterioration of toughness.
And so. Tantalum carbide, vanadium carbide, and chromium carbide are added to suppress grain growth during sintering of tungsten carbide, but if they are less than 0.1%, their effect is small, and if they are added in excess of 1.5%, they significantly reduce the toughness. It was set at 0.1 to 1.5% to cause deterioration. If the binder phase is less than 10%, the toughness will deteriorate, and if it is more than 50%, the wear resistance will be extremely poor, so the content was set at 10 to 50%. Next, if the average particle size of the hard phase exceeds 0.7 μm, the hardness becomes too soft and the wear resistance deteriorates.
Furthermore, if the amount of binder phase is reduced in order to prevent a decrease in hardness, the toughness deteriorates and desired properties cannot be obtained. Also 0.3μm
If the diameter is less than 0.3 to 0.7 μm, the starting material is limited in order to obtain the desired grain size. If the thickness of the film is less than 0.1 μm, no effect on abrasion resistance will be observed, and if it exceeds 2 μm, the breakability will deteriorate, so the thickness was determined to be 0.1 to 2 μm. [Example] Hereinafter, the properties of the alloy of the present invention and a comparative alloy will be compared based on Examples. As the raw material powder, tungsten carbide with an average particle size of 0.6 μm was weighed to have the composition shown in Table 1, mixed in a ball mill, then a plasticizer was added and kneaded, and a round bar of φ0.5 mm was formed using an extrusion molding machine. then 1350
After vacuum sintering at ℃ for 1 hour, a dot wire material with a diameter of 0.3 mm was produced by centerless polishing. Furthermore, TiN and TiC were coated to a thickness of 1.9 to 2.0μ by physical vapor deposition. The results of the comparison of physical properties are also listed in Table 1. Here, the transverse rupture force was measured at a span distance of 10 mm.
The comparative alloys of sample numbers 5 to 7 have component compositions equivalent to JIS K40 cemented carbide, which is commonly used in the past. It is recognized that the dot wire made of the fine-grained alloy of the present invention is significantly superior to comparative alloys in terms of transverse rupture strength and absorbed energy. Next, use these dot wires to cantilever,
Table 2 shows the results of a fatigue test conducted under the conditions of amplitude 4 mm, stress 130 Kg/mm ² and 50 Hz. The alloy of the present invention has a large amount of binder phase, and its fatigue resistance is also significantly superior to that of comparative alloys. Next, a mounting test was conducted and the amount of wear after the test was measured. The results are shown in Table 3. Furthermore, the wear amount measurement position is shown in FIG. b is the original shape before use, c is the shape after use, and a was measured to determine the amount of wear.

【table】

【table】

〔Effect of the invention〕

As described above, the surface-coated fine-grained cemented carbide dot wire of the present invention has improved toughness and absorbed energy without reducing wear resistance, compared to conventionally commonly used dot wires equivalent to JIS K40 cemented carbide. Since it has a significantly improved fatigue strength, it has superior fracture resistance and high performance compared to conventional cemented carbide dot wires.

[Brief explanation of drawings]

FIG. 1 schematically shows the wear pattern of the dot wire after the mounting test. a is the amount of wear,
b shows the original shape before use, and c shows the shape after use.

Claims (1)

[Claims] 1. In a surface-coated fine-grained superalloy dot wire, the hard phase is composed of 50 to 90% by weight of tungsten carbide and 0.1 to 1.5% by weight of at least one or two or more of tantalum carbide, vanadium carbide, chromium carbide, and molybdenum carbide, A cemented carbide whose remaining binder phase is composed of one or more iron group metals is used, with the average particle size of the hard phase being 0.3 to 0.7 μm, and further 0.1 μm on the surface.
A surface characterized by being coated with one type of single layer or two or more types of multilayer coating selected from carbides, nitrides, and carbonitrides of metals of groups 4a, 5a, and 6a of the periodic table to a thickness of ~2 μm. Coated fine-grain cemented carbide dot wire.