JPS6018620B2 - Zirconia wire drawing die and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zirconia wire drawing die that has excellent properties for soft metals and soft alloys (hereinafter simply referred to as soft metals) such as aluminum, aluminum alloys, copper, and copper alloys.

As for die materials for wire drawing of these European quality metals, tools, super hard alloys, stellite, etc. are generally used. There are drawbacks such as a short die life due to the welding phenomenon and poor surface gloss of the resulting wire drawn product.

Recently, dies made of diamond single crystal, diamond compax, cubic boron nitride, etc. are also being used, but all of these are expensive. Single crystal diamond provides products with excellent surface gloss, but it is very expensive and the life of the die per unit price may be short. In the case of dust materials, there are drawbacks such as the surface gloss of drawn wire products being sometimes inferior to products made of super hard alloys, so it has not been widely adopted.
The material of the present invention was developed after various studies in view of the drawbacks of the known die materials mentioned above.
．． (ii) the average crystal grain size of the sintered body is 2 m or less, and the side theoretical density is Iso. Although the specific zirconia adjoining body, which meets the three requirements of 5% or more, has lower hardness and lower elasticity than conventional ultra-hard die materials, it is compatible with soft metal wire drawing materials. The present inventors have discovered that the present invention can be achieved by discovering that because of its low properties, it can be used as a die material for a long time and provide a rolled bran product with excellent surface gloss. It is well known that a sintered body made of 100% zirconia undergoes a large volume change due to crystal type transition at 1000 to 1200 qo, and is destroyed.

Therefore, a competitive body of stabilized or partially stabilized zirconia is usually used, in which oxides of alkaline earth metals, rare earths, etc. are added to suppress the transition. Since the zirconia adhesion structure contains many closed pores inside and has coarse crystal grains, it is impossible to use it as a die material. However, the zirconia crystals of the present invention, which are produced by optimizing the blending amount of yttrium oxide, the particle size of the molding material powder, and the competitive binding conditions, have uneven theoretical density. 5% or more, there are very few closed pores, and the crystal grain size is as small as 2 meters or less, so it has been found that it exhibits extremely excellent properties as a die material. That is, the zirconia composite of the present invention is
Mirror-finished die materials have almost no spots that can be the starting point for welding of the wire drawing material, so the life of the die is long. Less loss of gloss. Furthermore, since the elastic modulus of the die material of the present invention is low, even when the die surface comes into contact with the wire-drawing material, it is difficult for crystal particles to separate from the die surface and wear occurs, and the mirror-like state can be maintained for a long period of time, resulting in excellent surface gloss. This is thought to be one of the causes. In the case of known zirconia crystals that have many closed pores, they have low affinity with wire drawing materials, but when used as die materials, welding progresses rapidly starting from spots due to the presence of spots. , the luster of the drawn wire product will deteriorate and the life of the die will be shortened. The zirconia aggregate used in the present invention usually contains 3.6 to 8.0% by weight of yttrium oxide (Y2Q) in order to impart properties necessary as a die material.
More preferably, it is contained in an amount of 4.5 to 7.0% by weight.

When the content of yttrium oxide is less than 3.6% by weight, cracks occur due to the dislocation of zirconia crystals during the competitive process.
On the other hand, 8. the desired competitive body could not be obtained. If the weight percentage exceeds bn/, the structure of the burnt stripe becomes coarse and the inside of the burnt stripe increases in number of closed pores and also includes coarse pores. Even if it is sintered after forming, it is not possible to suppress spots to the extent that it can be used as a wire drawing die. Moreover, the yttrium oxide content is 8. In order to minimize the number of sealed pores that are formed when the weight of It becomes impossible. The above spots are closely related to the density of zirconia crystals,
In order to be able to compete with other dice in terms of economy and other aspects in practical terms, the theoretical density of the die is usually sato. It is 5% or more, more preferably 99.5% or more. The theoretical density of a zirconia burnt stripe containing yttrium oxide varies not only depending on the content of yttrium oxide but also on the crystal structure of the Akatsuki compact, and is difficult to measure accurately. Therefore, Y20
The theoretical density of zirconia containing 33.6% was assumed to be 6.1 keys/base, and it was assumed that this decreases linearly as the Y208 content increases, and for zirconia containing 8% Y2Q, it becomes 6.05 key/base. . Furthermore, the crystal grain size in the zirconia crystals used in the present invention is required to be 2 mm or less, and 1
．． It is preferable that the length is 51 m or less. Even if a sintered twill body is obtained from an ultra-high purity starting material, those with large crystal grain sizes may be affected by impurities mixed in during the manufacturing process, minute cracks present in the sintered twill body, or the interaction between crystal grains and grain boundaries. Defects specific to polycrystalline materials, such as large differences in properties, shorten die life. Therefore, it is essential to reduce the thickness of the grain boundary layer, which is the origin of defects in polycrystals, by setting the grain size to 2 m or less, and when the grain size exceeds 2 m, the thickness of the grain boundary layer decreases. The heterogeneity caused by the increase in the number of coarse spots reduces and extends the wear resistance of the die, which not only shortens the life of the die but also deteriorates the surface gloss of the drawn wire product. The dice of the present invention are usually manufactured as follows.

It is essential that the zirconia powder containing 3.6 to 8.0% by weight of yttrium oxide, which is a starting material, has an average particle size of its primary particles of 0.5 m or less, and 0.3 m
It is more preferable that it is below. In addition, in the powder, it is preferable that yttrium oxide is homogeneously dispersed or solidified in zirconia, so it is preferable to manufacture by the following method rather than the method of directly mixing zirconia powder and yttrium oxide powder. preferable. (i) After mixing solutions containing a zirconium compound and a yttrium compound in a liquid phase state, the solution is stirred at about 400 to 120 pi.

(ii) After homogeneously mixing a solution containing a zirconium compound and yttria, or a solution of zirconia and a yttrium compound, they are mixed in the same manner as above.

If the primary particles of the powder obtained by the above method are strongly agglomerated, the powder is dispersed by wet pulverization and then dried to obtain a powder for molding.

In order to further improve the strength of the molded product obtained by pressure molding or to make the density of the molded product more homogeneous, the powder may be treated with a molding aid such as polyvinyl alcohol, stearic acid, or wax emulsion. The average particle size is 1
The powder may be sized to about 0 to 300 m, and used as a powder for molding. Next, the obtained powder or granulated material is molded into a predetermined shape under a pressure of n/ of 0.5 or more, preferably 1 to 3 tons/kg from an economical point of view, and then processed into the shape of a die nib. In the present invention, hot isostatic pressing (HIP) treatment is performed following firing in the atmosphere in order to obtain a die having a higher theoretical density. That is, the processed molded product is fired in the atmosphere at 1,200 to 1,650 q○, more preferably 1,250 to 160,000 to achieve a theoretical density of 95.
% to about 98%, and then at a temperature of 1200 to 155 psi under a pressure of 500 k9/mass or more in an inert gas atmosphere such as argon or nitrogen gas, more preferably 500 k9/mass or more. 1250~1500q under the pressure of
Perform HIP treatment at a temperature of ○. Thus, the counter-theoretical density group. It is possible to obtain dies that have a yield of 5% or more, usually as much as 99.5% or more, and the dies provide a product with a long life and excellent surface gloss. If the mP treatment temperature is less than 120 psi or the pressure is less than 500 k9/y, the theoretical density of the crystal body may not reach 98.5%. on the other hand,
When the processing temperature exceeds 155 and 0, the pressure increases to 500k9/
Even in the c-flow, the crystal grain size may be 2 wm or more, and the life of the die is likely to be shortened, making it impossible to achieve the object of the present invention. Example 1 Purity 99. Base weight% zirconium oxychloride and purity 9
9. An aqueous solution containing yttrium chloride in an amount of % by weight is heated and hydrolyzed under the rope frame.

The ratios of the two types of compounds are adjusted to the ratios shown in Table 1 as Z02 and Y203.

After adding n-octyl alcohol to the hydrolyzed solution and dehydrating and drying it by distillation to obtain fine particles of a zirconium-containing compound, the fine particles of the zirconium-containing compound were agitated at 85,000 ni. and the crystal particle size is 100~
A powder consisting of 300A zirconium oxide primary particles is obtained. The obtained powder is wet-milled using ethyl alcohol in a ball mill for 48 hours to be dispersed, dried, and sized to obtain a powder for molding having a uniform size of 100 m. (1) The obtained molding powder was molded into a cylindrical shape by the HIP method under the pressure shown in Table 1, and after processing this into the shape of a die nib, it was fired in the atmosphere under the atmospheric pressure conditions shown in Table 1. By competing with each other, the dice materials shown in Table 1 are obtained.

(0) The compacts obtained in the same manner as in (1) above were fired in the atmosphere under normal pressure firing conditions according to the sample numbers and others in Table 1, resulting in theoretical densities of 96% and 97.5%, respectively. A burnt striped body was obtained, placed in a high-pressure container equipped with a heater, and held in an argon gas atmosphere under the HIP conditions shown in Table 1 for 1 hour.

The obtained Akatsuki concretions are shown as G and skin in Table 1. still,
Only sample number (xi) has an average primary particle diameter of 0.8
Powder from Yamam was used as a raw material.

Furthermore, when all samples except (i), G and skin in Table 1 were subjected to Hm treatment under the conditions shown in Table 2, the theoretical density of all samples except sample numbers MD and (xi) was 99.
0% or more, and on the other hand, there was almost no change in the average grain size before and after the HIP treatment. Table 1 Table 2 The inner and outer surfaces of the die material obtained in (1) and (b) above are ground to the specified dimensions using a diamond grindstone, and the inner surface is mirror-finished with diamond powder to be used as a wire drawing die. do.

The obtained wire drawing die was used for wire drawing of aluminum, copper, brass, and steel alloys, and the results were as follows. 1 In a wire drawing die using aluminum a sample M with a die diameter of 6.3 and a skin of 0, even after drawing 2 tons of wire, the gloss and finish accuracy of the wire drawing were superior to those made with a cemented carbide die, and Expected to have a long life.

On the other hand, in the die using sample MD, welding occurred after 2 tons of wire drawing, and the gloss of the drawn wire deteriorated, so that it could no longer be used. Further, it was found that the die of sample (xi) was completely unsuitable as a die because welding occurred soon after use. b When used as a wire drawing die with a die diameter of 4.5 mm, each sample side has a diameter of 17 mm.
On the sample side, no welding occurred even after drawing 12 tons of wire, the surface gloss and finish accuracy of the wire drawing were good, and a product with a longer life and better quality than the cemented carbide die was obtained.

Steel A The amount of wire drawn using a wire drawing die with a die diameter of 2.6 ribs on the sample side reached 25 tons.

On the other hand, the life of the die using carbide tool grade GI is
The weight was about 20 tons, and the surface gloss of the drawn wire product was also significantly inferior to that of the product of the present invention.

When using a wire drawing die with a die diameter of 5.6 mm, the inner surface of the die will remain almost unchanged from before use even after drawing 1,000 wires (each length is about 1 h). , and the surface gloss of wire drawing was also good.

On the other hand, in a die of the same diameter as the sample, 100
After drawing 0 wires, the mirror surface of the inner surface of the die where the wire drawing material was in contact with the highest stress had become somewhat rough, and welding was expected to occur with subsequent use. Ta. When hot extrusion was performed using a wire drawing die with a die diameter of 2.3 using the W Cu-P-Fe-based copper alloy sample side, it withstood 40 extrusion operations.

On the other hand, the use limit for the Stellite die is 1 to 2 times, and the use limit for the die made of carbide tool grade GI is 2 countries, which clearly shows the excellent durability of the die of the present invention.

Claims (1)

[Claims] 1. A zirconia sintered body containing 3.6 to 8.0% by weight of yttrium oxide, the average crystal grain size of the sintered body is 2 μm or less, and the theoretical density is 98.5. % or more. 2 (1) 3.6 to 8.0% by weight of yttrium oxide
A step of dispersing aggregates of primary particles of zirconia powder containing zirconia powder and having an average crystal grain size of 0.5 μm or less, and further sizing as necessary to form a shaped powder, (2) the obtained shaped powder 5
A process of pressure molding at a pressure of 00 kg/cm^2 or more, (
3) Sintering the obtained molded body in the atmosphere at 1200 to 1650°C to obtain a pre-sintered body with a theoretical density of 95 to 98%,
(4) The obtained pre-sintered body was heated to 50°C in an inert gas atmosphere.
0 kg/cm^2 or more and a step of hot isostatic pressing under conditions of 1200 to 1550°C, and (5) a step of polishing the wire-drawing material passing surface of the sintered body. A manufacturing method for a soft metal wire drawing die.