JP2620237B2 - Composite structure rotary tool and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new structure of a rotary tool such as a drill, an end mill, a hob, a tap, and a method for manufacturing the same.

(B) Conventional Technology High-speed tool steel is often used as a material for rotary tools such as drills, end mills, hobs, and taps. This is an alloy that contains Cr, Mo, W, V, etc. as alloy components in steel and precipitates carbides of these components by heat treatment, and has higher wear resistance than ordinary steel. The next most commonly used cemented carbide is WC sintered with Co.

Compared to high-speed tool steel, it has a larger amount of carbide (WC), has significantly improved wear resistance, and has a small decrease in hardness at high temperatures, enabling high-speed cutting. But,
In terms of toughness, it is inferior to high-speed steel, and until now its use has been limited.

Various improvements have been made to fill the gap between the high speed tool steel and the cemented carbide. First, as improvements from high-speed tool steel, there are powder high-speed tool steel and coated high-speed steel. Powdered high-speed tool steel is a high-speed tool steel alloy powder with increased alloy components such as Cr, Mo, W, V, etc., made by atomizing method etc., and sintered by hot isostatic pressing etc. . In the conventional smelting method, coarsening of carbide particles is unavoidable when the alloy component is increased, and the toughness is significantly reduced.However, by the powder method, it is possible to disperse these carbides finely, without impairing toughness It has succeeded in improving heat resistance and wear resistance. Next, coated high-speed tool steel is applied to the surface of conventional high-speed tool steel by PVD
Hard ceramics such as iC and TiN are coated to a thickness of several μm to several tens μm, and the ceramics improve wear resistance.

As an improvement from cemented carbide, WC particles are extremely fine (1μ
m or less) to improve the strength of the alloy and increase the reliability.

(C) Problems to be Solved by the Invention Among the conventional techniques, high-speed tool steel (including powdered high-speed tool steel and coated high-speed tool steel) is an iron-based alloy, which has an increased amount of carbide or a coating on the surface. However, the heat resistance has not been essentially improved, and the tempering temperature of 600 ° C or less rapidly softens the cutting edge in the upper temperature range, making it unusable. In this case, the cutting speed cannot be increased, and it is not possible to cope with an improvement in machining efficiency.

Next, with cemented carbide, although the strength is about the same as high-speed tool steel, it is still a brittle material, and the cutting edge suddenly breaks or breaks from the root. Therefore, the reliability was poor and it was difficult to cope with unmanned processing.

In addition, although the tool in which the two were joined was certainly improved in toughness as compared with the cemented carbide, it sometimes cracked from the joint, and the performance was not sufficiently satisfactory.

B. Configuration of the Invention (a) Means for Solving the Problems The configuration of the present invention is as follows.

As a means for solving the above problem, in a composite-structure rotary tool having a central portion made of steel (preferably high-speed tool steel), an outer surface including a cutting edge thereof is made of a cemented carbide, and a thickness of a cemented carbide portion is reduced. Provided is a composite structure rotary tool having an outer diameter of 1% or more and 10% or less. Also, as its manufacturing method,
A steel material processed into a desired tool shape is placed in a reaction chamber, and a gas phase synthesized WC particle flow and a Co particle flow mixed therein are introduced into the reaction chamber, and a mixture of WC and Co is applied to the surface of the steel material. Deposit. Thereafter, the temperature of the steel material in the reaction chamber is increased to 1200 ° C.
By maintaining the temperature at 1500 ° C. or less, the WC-Co mixed layer on the surface is sintered to obtain a composite structure rotary tool.

(B) Action Steel serving as the center bears the toughness of the entire tool, and the cemented carbide on the outer surface including the cutting edge bears heat resistance and wear resistance. The thickness of the cemented carbide on the outer surface, including the cutting edge, ranges from 1% to 10% of the tool outer diameter. If it is 1% or less, the desired heat resistance and wear resistance cannot be obtained, and if it is 10% or more, the toughness significantly decreases.

The composition of the cemented carbide on the outer surface, including the cutting edge, is WC5-9
5 (wt%) Carbides or nitrides of Group IVa, Va, VIa metals other than WC are 0 to 95 (wt%), and Fe group metals are 3 to 40 (wt%).

WC is responsible for heat resistance and wear resistance of cemented carbide, but 5%
Below, heat resistance and abrasion resistance are not sufficient, and if it exceeds 95%, toughness decreases.

Carbides or nitrides of Group IVa, Va and VIa metals have the function of further improving the heat resistance and wear resistance of the alloy. However, if the content exceeds 95%, the toughness also decreases.

The Fe group metal plays a role in the toughness of the alloy. However, if the content is less than 3%, the effect is not obtained. If the content exceeds 40%, the wear resistance is deteriorated.

Next, the manufacturing method is described. First, WC particles obtained by producing WC by vapor phase synthesis become ultrafine particles of 100 nm (0.1 μm) or less, and the sinterability is remarkably improved,
This has the effect of increasing the strength of the cemented carbide after sintering and increasing the toughness. As a method of gas phase synthesis, W is vaporized by arc discharge in a hydrocarbon atmosphere to combine hydrocarbon carbon, and W halides (WF ₆ , WCl ₆ etc.) are decomposed in high temperature hydrocarbons. And a method of sublimating an oxide of W, and reducing and carbonizing the same in a mixed gas stream of hydrogen and hydrocarbon. The method of producing Co fine powder includes an arc in a gas atmosphere and a method using an electron gun, but resistance heating is sufficient.

Next, these are introduced into the reaction chamber. Since the powder is in the form of fine powder, each particle can be easily introduced by reducing the pressure in the reaction chamber. WC before putting in the reaction chamber
Mixing with Co is desirable to obtain a uniform alloy.

Further, according to this method, it is also possible to continuously change the composition of the cemented carbide from the interface with the central steel material to the surface. In other words, at the interface with the steel material, by increasing the amount of the Fe group metal, the cemented carbide and the steel material can be sufficiently joined together, and the Fe group metal can be reduced toward the surface to increase the wear resistance. .

Next, in the sintering process, this may be done by taking out the WC-Co mixed powder from the reaction chamber and recharging it into the sintering furnace, but the temperature can be raised as it is in the reaction chamber. This is preferable from the viewpoint of preventing oxidation because it requires less time and effort to move and is not exposed to the atmosphere. Sintering temperature is WC
The temperature is preferably as low as possible from the viewpoint of suppressing grain growth, and a good range is 1200 ° C to 1500 ° C.

Example 1 A high speed tool steel drill (SKH51, blade diameter 9.0 mm) was used as a base material, and this was put into a vacuum chamber equipped with a heating device and 1 × 10 ^-2 To.
Vacuum was pulled to rr. A WC gas phase synthesis device and a Co fine powder production device are connected to this vacuum tank via a mixing tank.

The WC gas phase synthesizing apparatus and the Co evaporator are operated, the WC particles and the Co particles are introduced into a mixer, mixed, and then introduced into a vacuum chamber, and the WC-Co mixing tank is placed on the surface of the drill. Was deposited.

 The WC gas phase synthesis was performed under the following conditions.

W Evaporation method: arc discharge (discharge voltage 20v discharge current 80A) W evaporation: 450 g / hr introduced amount of _{gas: CH 4 1 / min H 2} 3 / min Pressure: 200 Torr Co evaporation is carried out by resistance heating, the 50 g / hr H ₂
It was kept at 200 Torr at 3 / min.

One hour later, when the apparatus was stopped, the thickness of the WC-Co mixed layer was 0.65 mm.

Next, while keeping this in a vacuum chamber,
After holding for a time, it was cooled to room temperature.

Then I took out the drill and checked the outer diameter 10.1mm
Therefore, this was polished and adjusted to a drill with a blade diameter of 10 mm. The composition of the outer superhard part was WC-10% Co and had a continuous structure in which the interface between the base metal and the superhard part could not be confirmed.

Next, the drill of the present invention is made of 10φ high speed tool steel drill (SKH51) powder high speed tool steel drill, coated high speed tool steel drill, and cemented carbide (WC-10C).
o) The drill was tested under the following conditions.

Condition 1 Work material S50C Cutting speed 40m / min Feed 0.2mm / rev Hole depth 40mm (penetration) Evaluation Number of processed holes Condition 2 Work material SKD11 Cutting speed 20m / min Feed 0.15mm / rev Hole depth 20mm (stop) Workpiece table feed 50mm / min ~ (during machining) Evaluation Table feed leading to breakage Here, condition 1 is a test for examining the wear resistance of the drill, and condition 2 is that the work material being processed is moved sideways. Is a test for applying a lateral load to the drill and examining the resistance to breaking.

 Table 1 shows the test results.

As can be seen, the product of the present invention has both abrasion resistance comparable to carbide and toughness comparable to high speed tool steel. It is considered that the reason why the wear resistance of the product of the present invention is superior to that of a cemented carbide even though it has the same composition is that the WC has a very fine particle size due to the vapor phase synthesis method.

Example 2 An end mill SKH59 made of high-speed tool steel (diameter: 4.5 mm) was used as a base material, and was placed in the same apparatus as in Example 1 to deposit a WC-Co mixed layer.

Here, Co was evaporated by resistance heating as in Example 1, but WC was formed by decomposition of WCl ₆ . Condition is 600
° C., H ₂ flow rate of 10 / min, and a CH ₄ flow rate 1 / min. The average particle size of the obtained WC was 50 nm.

Next, this end mill was heated and heated, and sintered at 1350 ° C. for 1 hour. After that, this was newly processed into an end mill with a blade diameter of 5.0 mm, and compared with existing high-speed tool steel cemented carbide.

Work material: Inconel 750 Axial depth of cut 7.0mm Cutting speed: 20m / min Radial depth of cut 1.0mm Feed: 0.3mm / rev Use of water-insoluble cutting oil Judgment Cutting length until VB = 0.20mm C. Effect of the Invention As described above, according to the present invention, the toughness can be improved to the same level as that of high-speed tool steel while maintaining the wear resistance of the cemented carbide, so that the reliability of drills, end mills, taps, hobs, etc. If high-speed tool steel has been used in the cutting field where cutting performance is particularly required, the cutting speed and feed rate can be increased, and the machining efficiency is greatly improved. In such a case, the feed rate can be increased, and the processing efficiency is improved. It is preferable to coat the obtained composite structural tool with ceramics such as TiC, TiN, and Al ₂ O ₃ by using a CVD method or a PVD method from the viewpoint of improving wear resistance.

[Brief description of the drawings]

FIG. 1 is an example of an apparatus for making a tool of the present invention.
This is also a schematic of the apparatus used in Example 1. 1 is a vacuum chamber, 2 is a material to be processed (drill), 3 is a support base for supporting the rotation and left and right movement of the material to be processed, 4 is a heater for heating, 5 is a mixer, 6 is a Co evaporator, 7 Denotes a heater heater power supply, 8 denotes a cobalt lump, 9 denotes a WC synthesizing apparatus, 10 denotes an arc discharge power supply, and 11 denotes a tungsten lump.

Claims (4)

(57) [Claims] An outer surface including a cutting edge thereof is made of a cemented carbide, and the thickness of the cemented carbide portion is 1% to 1% of the entire diameter of the tool. Ten
% Rotary tool with a composite structure. 2. The composition according to claim 1, wherein the composition of the cemented carbide is from 5 to 95% of WC, and from 0 to 95% of carbides and nitrides of Group IVa, Va, and VIa metals other than WC. A composite structure rotary tool comprising 3 to 40% of Fe group metal. (3) WC is synthesized in the gas phase, and the WC is deposited on the steel as the central material while mixing the WC with the Co fine powder in the gas phase.
A method for manufacturing a rotary tool having a composite structure, comprising sintering at a temperature of from 00 ° C to 1500 ° C. 4. The composition of the cemented carbide part after sintering is controlled by controlling the ratio of WC and Co during deposition in claim (3) to make the surface rich with Co at the interface with the steel material. A method for manufacturing a rotary tool with a composite structure, characterized in that the amount of Co is changed so as to gradually decrease as the temperature increases.