JPS6338501A - Composite sintered hard alloy and its production - Google Patents

Abstract

PURPOSE:To obtain a composite sintered hard alloy having high strength and impact resistance by sintering a fine particulate super alloy member having an average grain size of a hard phase of a specific value or below integrally on the surface of a main material consisting of an ordinary sintered hard alloy having the average grain size of the hard phase in excess of a specific value. CONSTITUTION:The main member consisting of the ordinary sintered hard alloy consists of the hard phase (consisting of tungsten carbide, etc.) and the bonding phase (consisting of iron family element), and the average grain size of the hard phase is >1mum. The fine particulate sintered hard alloy consists of the element components similar to the components of the above-mentioned main material, but the average grain size of the hard phase is limited to <=1mum. Wax is added to the kneaded with the powders of the respective member components mentioned above in order to render fluidity thereto and the mixture is pelletized. Either main member or surface member (fine particulate super alloy material) is injection-molded first, then the other member is injection-molded in succession thereto. The resulted composite molding is degreased and sintered. The sintered hard alloy having the hardness equiv. to the hardness of the fine particulate sintered hard alloy and has the high strength and impact resistance is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a composite cemented carbide suitable for cutting edges of drills, grinders, etc., and a method for manufacturing the same.

[Conventional technology]

Normally, cemented carbide is composed of a hard phase mainly composed of tungsten carbide and a binder phase mainly composed of iron group elements such as metallic cobalt.The fine powders of each phase are mixed and formed, and then placed in a high-temperature furnace. Manufactured by sintering.

The surface hardness of a product depends on the average particle size of the hard phase that constitutes it, and when this becomes 1 μm or less, the hardness reaches a significant upper limit, and it has recently attracted attention as a fine-grained cemented carbide.

However, fine-grained cemented carbide has the drawback of being inferior in bending strength and impact resistance. In addition, fine-grained cemented carbide powder is delicate to handle during the manufacturing process, and furthermore, it easily absorbs moisture, making it difficult to concentrate the components, and selective grain coarsening occurs during sintering. Variations in characteristic values are likely to occur. Therefore, despite its advantage in hardness, fine-grained cemented carbide has disadvantages in terms of strength, manufacturing process control, and manufacturing cost, and its applications are limited to extremely small diameter trills and small-diameter gourd cups. Currently, press forming or extrusion forming is used for forming before sintering, but the shape of the product obtained in this case is limited to a one-dimensional elongated form with a single cross section, and complex shapes are not possible. It's difficult to make things.This low degree of freedom in shape selection also limits its uses.

[Problem that the invention seeks to solve]

The present invention aims to improve the strength and impact resistance of the above-mentioned fine-grained cemented carbide, thereby reducing production costs and increasing the degree of freedom in selecting product shapes.

[Means for solving problems]

The present invention provides a composite cemented carbide material in which a surface component is made of a fine-grained hard phase cemented carbide with excellent hardness, and main components of a normal cemented carbide with excellent strength are integrally sintered with the surface component. This solved problems in terms of strength and cost. Here, in the surface member of fine-grained cemented carbide, the hard phase has a grain size of 1
It contains tungsten carbide of micrometer or less, or one or more kinds of other metal carbides or metal nitrides, and its binder phase consists of one or more kinds of cobalt or other iron group elements. The elemental composition of the main constituent member is the same as that of the surface member, but the average particle size of the hard phase is
It may be larger than μm.

When joining a surface member made of fine-grained cemented carbide and a main member usually made of cemented carbide, the present invention employs a method in which both parts are molded in close contact and then simultaneously sintered, without using post-processing such as brazing or welding. Take. When molding each component, injection molding, which is widely used for plastic molding, will be used instead of press molding or extrusion molding. In order to make injection molding possible, first 5.0 to 5.4% by weight of paraffin wax is added to the powder of each component component to give it fluidity, and this is kneaded and granulated into pellets. Either the surface member or the main member is injection molded into a mold selected depending on the final shape. The injection conditions were a temperature of 80 to 120°C;
The pressure shall be 1000 to 1500 kg/m. After molding the first member, it is embedded in another mold, and the remaining members are injection molded. Through this double molding method, a composite molded body in which both parts are integrated is obtained, which undergoes a degreasing process at around 300°C, a sintering process at around 1400°C, and final processing to form a composite superstructure. Obtain hard metal.

In the composite cemented carbide obtained through the above steps, since the image constituent members are sintered at the same time, the strength of the interface is sufficiently strong, and there is no fear of cracking or breaking at the interface. In addition, since the injection molding method is used for molding, by appropriately changing the mold, it can be applied to products with relatively complex shapes. °Surface hardness is the most important characteristic required for cemented carbide, but the surface hardness of such composite cemented carbide is equivalent to that of fine-grained cemented carbide, and is generally comparable to that of cemented carbide. Integration improves toughness, making it resistant to breakage and breakage. In addition, since a small amount of fine-grained cemented carbide components are used, manufacturing costs are reduced, and overall properties and economy are far superior to existing cemented carbide materials.

〔Example〕

Examples of the present invention will be described below.

The actual production of a bar-shaped composite cemented carbide with a soutachi plate size of 5 sm x 5 sm x 40 m and the results of evaluating mechanical properties using this test piece are shown below.

First, a fine-grained alloy member is made by adding a predetermined weight % of Co powder and 1 weight % of vanadium powder to tungsten carbide powder with an average particle size of 0.6 μm, and wet-pulverizing it in a ball mill. Mixed. Add 5.0 to 5.4 heavy cans of paraffin wax to this, and after kneading at 100°C,
Granulate into pellets. Normally, alloy powder m is prepared by adding 1% Co powder of a specified type to tungsten carbide powder with an average particle size of 5 μm, wet-pulverizing and mixing in a ball mill, and then adding 5.0 to 5.4% by weight of paraffin wax to 100% The mixture was kneaded at ℃ and granulated into pellets. These pellets,
Double molding is carried out using an injection molding machine. First, the pellets of the fine-grained alloy part are injected into a square mold at a temperature of 100°C and an injection pressure of 1200 kg/ryu. Next, a similar-shaped square mold with a deep bottom is injected. was transferred to a mold, and pellets of normal alloy powder were injection molded thereon under the same injection conditions.The resulting composite molded body was held at 300°C, degreased, and heated to 1400°C (±2
After sintering in a high temperature sintering furnace (0°C), surface grinding was performed to produce a rod-shaped composite cemented carbide. The thicknesses of the fine-grained alloy part and the normal alloy part of the obtained test piece were 211 and 3u, respectively.
It is.

Table 1 shows the results of mechanical tests conducted using this as a test piece in comparison with conventional ordinary cemented carbide and fine-grained cemented carbide. Here, the hardness was measured on the surface of the fine grain alloy, the bending strength was evaluated by three-point bending measurement with the fine grain alloy surface as the top surface, and the impact strength was evaluated by Charpy impact test with the fine grain alloy surface as the front surface.

Table 1 1.2 shows the characteristic values for test specimens of the same size of normal alloy and fine-grained alloy single-phase materials, respectively, and 3 to 5 are the composite cemented carbide according to the present invention in which 40% of the total is made of fine-grained alloy. is the characteristic value of The alloy of the present invention exhibits a significant improvement in hardness compared to normal alloys, while also being superior to fine-grained alloys in bending strength and impact strength, and is significantly more economically advantageous.

Disastrous Hero 1 A cutting blade was manufactured using composite cemented carbide as follows. First, tungsten carbide powder with an average particle size of 0.6 μm was
5% Co powder and 1% by weight to prevent grain coarsening
of vanadium carbide powder was added and mixed by wet pulverization in a ball mill, and another was prepared by adding 10% by weight of Co powder to tungsten carbide powder with an average particle size of 5 μm and wet pulverizing and mixing in a ball mill. . Add 5.4% by weight of paraffin wax to these and heat to 100°C.
After kneading and granulating into pellets and pellets, the pellets using fine tungsten powder were first injection molded into a mold with concave holes at a temperature of 100°C and a pressure of 1300 kg/cm; It was placed in a separate mold, and regular grain alloy pellets were injection molded on top of it under the same conditions to create a composite. This compact was subjected to degreasing at 300°C, preliminary sintering, processing, and final sintering, and was sharpened in the final processing to obtain a sintered rod having a cross-sectional shape as shown in FIG. The cutting performance of the product of the present invention is
The whole was compared with one made of fine-grained alloy, and there was no difference. Also, manufacturing costs were reduced by about 10%.

〔Effect of the invention〕

As described above, according to the present invention, it was possible to produce a cemented carbide having a hardness equivalent to that of fine-grained cemented carbide and excellent strength and impact resistance at a cost lower than conventional ones. Furthermore, according to the present invention, products with relatively complex shapes can be manufactured by selecting a mold during molding.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the molded body obtained in Example 2. Patent applicant: Sumitomo Kinku Mining Co., Ltd. Figure 1

Claims (2)

[Claims] (1) A composite cemented carbide formed by integrally sintering a fine-grained cemented carbide member whose hard phase has an average grain size of 1 μm or less on the surface of a normal cemented carbide main member whose hard phase has an average grain size of more than 1 μm. (2) Normal cemented carbide pellets made by kneading a binder phase powder consisting of a hard phase powder with an average particle size exceeding 1 μm and an iron group element with wax, and a hard phase powder with an average particle size of 1 μm or less and a binder phase powder consisting of an iron group element. It is characterized by first injection molding one of the fine cemented carbide pellets prepared by kneading binder phase powder with wax, then successively injection molding the other pellet, and sintering the composite molded product after degreasing. A method for manufacturing composite cemented carbide.