JPS6327402B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field The present invention relates to a method for processing mixed powder when molding raw mixed powder into various shapes in the manufacturing method of cemented carbide and ceramics. (b) Purpose of the Invention The method of the present invention facilitates molding during pressing with a mold or extrusion molding, reduces the amount of organic binder and lubricant added, and makes it possible to form more complex shapes or thicker shapes. The purpose is to make it possible to mold products with a diameter of 100 mm, and to manufacture high-quality powder metallurgy products. (c) Technology background WC main component cemented carbide, TiC cermet,
Ceramics mainly composed of Al ₂ O ₃ and Si ₃ N ₄ ceramics are widely used in the mechanical industry as cutting tools and wear-resistant tools. As the scope of its use expands, the variety of its compositions increases, and products of various shapes are required. When manufacturing products of various shapes, the above-mentioned hard alloys and ceramics are molded by molding, extrusion, etc. after thoroughly mixing raw material powders, but these hard powders usually have poor lubricity. Since this is not available, 0.5 to 20% of organic auxiliaries are mixed in advance before molding. As this organic auxiliary agent,
Binders such as methylcellulose and glue, and lubricants such as paraffin, glycerin, and camphor are used, and are essential for molding the hard material powders mentioned above, which allow the powder particles to flow smoothly within the mold. This has the effect of reducing friction with the mold wall and maintaining the strength of the molded product. However, on the other hand, these organic auxiliary agents need to be removed by heating at a predetermined temperature before sintering, and if there is a large amount of auxiliary agents, it will take time to remove them by heating, and if the removal is incomplete, sintering will be required. It causes pores in the body, and free carbon remains, which adversely affects the strength of the sintered body. In particular, in the case of extrusion molding, for example, a large amount of the above-mentioned organic auxiliary agent is mixed into the cemented carbide powder to give it plasticity and then molded using an extruder. Since cavities increase and a good quality sintered body cannot be obtained, it is usually applied only up to a diameter of 2 to 3 mm. In addition, in a mold press, if the amount of organic auxiliary agent is small, the molding pressure becomes excessively high and cracks may occur after molding. In particular, when the hard powder that is the raw material becomes fine, the frictional resistance between the particles is large, requiring a large amount of organic auxiliary, and the heat treatment after molding takes a lot of time, and in some cases, cracks may occur. This is often the case. If the amount of organic auxiliary agent is large, the sintering shrinkage in the subsequent process will be large and it will be difficult to maintain the dimensional accuracy of the sintered body. Therefore, it is important to consider how to mix a small amount of an organic auxiliary agent into a hard mixed powder made of several types of materials to facilitate molding. (d) Disclosure of the invention The present invention proposes a method for solving the above-mentioned problems, and its characteristics are as follows: As a pretreatment before adding an organic auxiliary agent to a hard powder, the powder is first treated with acetone, especially This treatment method is characterized by making the primary particle surfaces of powder particles lipophilic after washing and activation. Usually, these hard powders are composed of several types of mixed powders. For example, in the case of cemented carbide, it is a mixed powder containing WC as a main component and TaC, TiC, NbC, and Co. The inventor studied how to uniformly disperse these powders in the oil-based lubricant phase, and found that
Noting that these individual powders can be either hydrophilic or lipophilic, it has been found that the problem can be solved by changing the hydrophilic powder to a lipophilic powder. When examining the surface properties of various powders (compositions), we found that WC, WC-TiC (double carbide), Co,
It was found that Al ₂ O ₃ is hydrophilic, and TiC, TaC, NbC, etc. are lipophilic. It was also found that the properties vary depending on the particle size of the powder. To make the above hydrophilic powder lipophilic,
An alkyl group such as CH ₃ may be bonded to an alkoxyl group, and an esterification reaction using an alcohol may be used. Hard powder is generally considered to be a fine powder with carbide and metal surfaces that are slightly oxidized.
If the main constituent element is Mi, the esterification reaction is Mi〓OH+RO〓→MiOR+H ₂ O However, Mi〓OH is a surface hydroxyl group of carbide etc. According to the above formula, if H ₂ O is dehydrated, alkyl groups (-R) and alkoxyl groups (-OR) will be formed on the surface.
The particles become lipophilic. Note that primary alcohols and secondary alcohols are suitable as alcohols used in the present invention. It has been found that by carrying out the above-mentioned treatment of the present invention, a significantly smaller amount of organic auxiliary agent is required for molding. As a result, the time for removing the auxiliary agent has been shortened, and the sintered body has fewer cavities and free carbon, and the shrinkage rate has been reduced, making it possible to improve dimensional accuracy. Also, in the case of extrusion molding, it has become possible to mold rods with a larger diameter than before. As a method for making the surface of the powder particles lipophilic, any method may be used as long as the above-mentioned esterification reaction occurs, and autoclave methods, reflux methods, steam methods, etc. are preferable. In particular, the autoclave method is industrially advantageous because the reaction time is short. Next, an example will be explained. Example 1 Cemented carbide powder containing 94% by weight of WC, 1% by weight of TaC, and 5% by weight of Co with a particle size of 1μ was treated with benzene four times.
After washing with acetone three times to sufficiently remove surface contamination, 10g of C ₁₆ H ₃₃ OH and 65 ml of hexane (C ₆ H ₁₄ ) were added to 100 g of the mixed powder, and the mixture was placed in an autoclave at 234°C and 29 Kg/cm ² for 30 minutes. Processed. This powder was mixed with 3.75% grease and 1.25% paraffin wax to add plasticity, and then extrusion molded to produce a 4 mm diameter sintered rod. Table 1 shows the necessary additives and their effects when obtaining a sintered body with a size of 4 mmφ compared to when the same cemented carbide powder is extruded and sintered without lipophilic treatment. Note that the above-mentioned cetanol C ₁₆ H ₃₃ OH acts so that the lubricant sufficiently wets the surface of the powder.

[Table] As shown in Table 1, by adding the treatment of the present invention, only half the amount of additives is required compared to conventional ones, the strength of the molded product is high and it is easy to handle, and the heating time required to remove the organic agent is It was found that the shrinkage during sintering was reduced to 1/4, and dimensional accuracy was improved. Example 2 Ceramic powder containing 0.4% Al ₂ O ₃ powder V, Y ₂ O ₅ and MgO with a particle size of 0.5μ as sintering aids was washed three times with benzene and three times with acetone to sufficiently remove surface contamination. After removing, about 100g of mixed powder
10 g of C ₁₆ H ₃₃ OH and 65 ml of hexane (C ₆ H ₁₄ ) were added, and the mixture was treated in an autoclave at 234° C. and 29 Kg/cm ² for 30 minutes. This powder was mixed with 3% fine paraffin wax as a lubricant and then mechanically press-molded to produce a sintered body of 20 x 40 x 15 mm. In the above case, when the same ceramic powder was not subjected to lipophilic treatment, the dewaxing time was shortened to 1/3 from 72 hours to 24 hours, compared to when press molding and sintering was performed. Fine paraffin wax without lipophilic treatment required 9%. Productivity is significantly improved by the process of the present invention,
It also saves on materials and significantly expands the range of shapes that can be manufactured. Example 3 A cemented carbide powder containing 0.5μWC, 87.5% by weight, and 13% by weight of Co was washed 4 times with benzene and 3 times with acetone to sufficiently remove surface contamination, and then the mixed powder was prepared.
The mixture was treated by a reflux method in which 20 ml of decanol and 82 ml of tridecane were added per 100 g and refluxed at 218°C for 1 hour, trapping and separating the water produced. Add 0.5% by weight of paraffin wax to this powder, wet mix, and dry the powder into a 15mm cube at 0.5T/cm ²
It was pressed and sintered at a press pressure of . Table 2 shows the effects when compared with the case where the same cemented carbide powder was not treated with lipophilic treatment.

[Table] As shown in Table 2, the reflux method also shows excellent effects similar to the autoclave method.

Claims (1)

[Claims] 1. In a method for treating ultra-hard powder to be subjected to molding, after the ultra-hard mixed powder is washed and activated, the surface of the primary particles of the powder is made into an alkyl group or an alkoxyl group to make it lipophilic. A method for processing ultrahard powder, characterized by converting it. 2. The method for treating ultrahard powder according to claim 1, wherein the ultrahard powder is made lipophilic by either an autoclave method or a reflux method. 3 The ultrahard powder is a cemented carbide powder whose main component is WC, a cermet powder whose main component is TiC, Si ₃ N ₄ ,
2. The method for treating ultra-hard powder according to claim 1, wherein the ceramic powder is mainly composed of Al ₂ O ₃ .