JPS6254055A - Drill made of hard alloy - Google Patents

Abstract

PURPOSE:To prevent sticking of chips to cutting edge as well as breaking of cutting edge and to improve drill life by forming the whole drill of sintered hard alloy consisting of WC, TiC, TiN, Mo or Mo2C, and iron group metals. CONSTITUTION:The whole twist drill is formed by use of a sintered hard alloy having a composition consisting of, by weight, 10-60% WC, 5-40% TiC, 3-20% TiN, 5-20% Mo or Mo2C and 5-20% of iron group metals such as Co, Ni, Fe, etc. If necessary, 5-30% TaC or TaN is incorporated to the above sintered alloy. On application of a drill having the above composition, the occurrences of breaking and chipping caused by sticking and separation of chips to and from cutting blade are prevented and accordingly drill life can be improved. Moreover, the expected drilling capacity can be maintained even after regrinding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a twist drill for drilling holes in metal and the like.

[Prior art]

Conventionally, the sharpeners used to drill holes in metals and the like using twist trigs made of special steel often suffer wear and tear on their cutting edges, making it impossible to drill holes economically.

In addition, with a twist drill made of cemented carbide, chips generated during drilling are likely to compress or separate from the cutting blade, causing the cutting blade to crumple or slit, resulting in a shortened drill life.

Coating drills, which have recently started to attract attention, have a cutting edge coated with a coating of titanium nitride or titanium carbide, which can increase the lifespan of the drill, but the cutting edge wears out and requires re-grinding. The problem is that the life of the next bird /I/'# is greatly reduced.

[Purpose of the invention]

The present invention has been developed in view of the above-mentioned problems, and reduces the wear and tear of the cutting edge, and also prevents the generation and welding of chips to the cutting edge as much as possible, thereby improving the evacuation of chips to the cutting edge. The purpose of the present invention is to provide a twist drill that can prevent chipping and chipping caused by crimping and separation of chips, extend the life of the drill, and maintain the desired drilling ability even after regrinding the drill μ. It is something.

[Means for solving problems]

The present invention solves the above-mentioned problems with the following configuration.

That is, 10 to 60 inches of tungsten carbide, 5 to 20 inches of titanium carbide, 5 to 20 inches of titanium nitride, 5 to 20% of molybdenum or molybdenum carbide, and 5 to 20% of iron group metals such as cobalt, nickel, and iron. The first gist is a hard alloy tripod in which the entire twist drill is formed from a hard sintered alloy consisting of a hard sintered alloy consisting of a
Alternatively, the second aspect is a hard alloy drill containing TaN in a weight ratio of 5 to 30%.

[Action of the invention]

The present invention has excellent heat resistance due to the above-described configuration, and hardness is increased without causing a significant decrease in transverse rupture strength, and can be adapted to cutting conditions specific to drills.

In other words, titanium carbide is the most suitable element for reducing secondary wear and rake face wear when cutting steel or high-grade cast iron.

Therefore, it is advantageous to increase the proportion of titanium carbide as much as possible as far as wear is concerned, but there is a risk that various problems will arise due to the extremely low thermal conductivity of titanium carbide, and for this reason, titanium carbide is In order to use it at a high i-rate, it is conceivable to use tungsten carbide, tantalum carbide, niobium carbide, etc. as a solid solution.

However, during sintering, titanium carbide-containing solid solutions tend to fuse together and grow into large particles from the contact areas. The size of these particles is a major influencing factor for cutting edge wear.
In any case, it is desirable that the particle size of the titanium-containing solid solution is small.

However, grain growth can be prevented by adding an appropriate amount of titanium nitride. Titanium nitride can suppress the grain growth of solid solution particles often found in titanium carbide and make crystal grains finer, while maintaining the nucleated structure with titanium carbide as the core, which is unique to titanium carbide-based alloys.

Furthermore, titanium nitride has higher thermal shock resistance than titanium carbide, and has a smaller coefficient of friction with steel, so the amount of heat generated is also lower, improving thermal shock resistance. In this way, the addition of titanium nitride makes the grains finer, so the hardness is high and the wear resistance is significantly improved.The friction coefficient is also small, so when the hole is The generated chips are smoothly ejected without welding to the cutting edge, eliminating the problem of chipping and chipping of the cutting edge that previously occurred due to crimping or dispersion of the cutting chips. At the same time as preventing the j of the cutting edge! ! ! Loss can also be reduced and the desired drilling capacity can be maintained over a long period of time.

It should be noted that the content of titanium carbide and titanium nitride in the alloy is preferably within the ranges described above; if it exceeds this, the toughness will be poor, and if it is below the above range, it will not have sufficient heat resistance or wear resistance. I can't get it.

Tantalum carbide or nitride tank μ is used to efficiently contain titanium carbide, but tank
It is difficult to separate niobium from niobium during smelting, and tanks often contain niobium. Therefore, since this solid solution does not show a significant difference in performance from the tank M alone, a portion of the tank μ may be replaced with niobium.

In addition, it is well known that molybdenum or molybdenum carbide is effective in suppressing grain growth when the content of titanium carbide is high, but adding 5 to 20% of molybdenum improves the impact resistance of the alloy. It has the effect of reducing chipping or chipping of the cutting edge even if chips collide.

〔Example〕

The raw materials are mixed in the component ratio shown in the table below, put into a ball mill, and mixed for about 118 hours. The powder is then pressure-molded and sintered at 11,100~1u30℃. A hard sintered alloy that can be formed into

〔Effect of the invention〕

The above hard sintered alloy was machined to form a twist drill. The drill according to the present invention was tested under the following cutting conditions.

For comparison, a conventional twist drill made of cemented carbide with a titanium coating formed by the PvD method was also tested under the same conditions as the present invention. In addition, tests were also conducted on the Tori μ according to the present invention and the Tori μ for comparison after re-grinding the cutting edge portions.

Test conditions (a) Work material: 330C (raw material) (b) Cutting speed: 30! - (c) sending ri: α
15"/rev) Depth of cut: 24 = (Blind hole) (E) Drill /L/Diameter: 8 Cutting oil: Hosoika Soto E'M (diluted 11 to 5 times and applied externally) The above test results showed that both the drill according to the present invention and the coated drill for comparison had no defects even after drilling 400 holes.

However, in a test after re-grinding the cutting edge of the drill, the coated drill used for comparison showed that the cutting edge was significantly worn after drilling 100 holes, and in some cases, drilling 2 holes. In contrast, each doy1v according to the present invention maintained the expected performance.

Claims (2)

[Claims] (1) Tungsten carbide 10~60%, titanium carbide 5~
The entire twist drill is made from a hard sintered alloy consisting of 10% titanium nitride, 3 to 20% titanium nitride, 5 to 20% molybdenum or molybdenum carbide, and 5 to 20% iron group metals such as cobalt, nickel, and iron (by weight). A hard alloy drill characterized by a formed. (2) In claim 1 above, TaC
Alternatively, a hard sintered metal drill characterized in that the entire twist drill is formed from a hard sintered metal containing 5 to 30% by weight of TaN.