October 29, 2018

Preparation method of cast tungsten carbide powder

Tungsten carbide powder (WC) is the main raw material for the production of cemented carbides. Known as, tungsten carbide powder black hexagonal crystal, metal luster, hardness similar to diamond, is a good conductor of electricity and heat. Melting point 2870 degrees, boiling point 6000 degrees, relative density 15.63 (18 degrees). Tungsten carbide is insoluble in water, hydrochloric acid and sulfuric acid. Pure tungsten carbide is fragile. If mixed with a small amount of metals such as titanium and cobalt, brittleness can be reduced. Tungsten carbide, used as a cutting tool for steel, is often added with titanium carbide, tantalum carbide, or a mixture of them, to enhance the ability to resist explosion. Tungsten carbide is chemically stable.

 

A method for preparingcast tungsten carbide powder is characterized by the following steps:

(1) in 200 ~ 250 g block graphite, puts the crusher in the crushing and 150 mesh sieve, graphite powder, graphite powder and put in 1 l beaker, and to add 600 ~ 700 ml beaker mass fraction is 85% sulfuric acid, stirring evenly mixed, and then to join in a beaker of 7 ~ 8 g potassium permanganate, stirring and heating heating to 70 ~ 70 degrees, 1 ~ 2 h reaction;

(2) after the reaction, then to join in a beaker mixture quality 15 ~ 20% mass fraction is 17% hydrogen peroxide solution, stirring evenly mixed, and put the beaker in 0 ~ 2 degrees ice water bath, freezing crystallization 50 to 55 min after the crystallization of mixture in the centrifuge in centrifugal separation, the control speed is 200 ~ 220 r/min, the centrifugal 40 ~ 45 min, stay after the separation, collection of centrifugal, will collect the centrifugal content on temperature is 60 ~ 70 degrees oven drying after 1 ~ 2 h, then put in ball mill ball mill and 170 mesh sieve, get nano graphite powder;

(3) in 200 ~ 250 g, metal tungsten to place it in the furnace and zhongtong into the calciner to calcine furnace volume two-thirds of oxygen, stay bubbled into complete, calcination, control the calcination temperature is 800 ~ 850 degrees, calcination, after 1 ~ 2 h using spray gun to the preparation of nano graphite powder injection to calcine furnace, control air injection rate is 0.20 ~ 0.25 kg/s.

(4) at the same time, access to the calcination furnace burning furnace, a third volume of hydrogen stay bubbled into complete, improve the calcination furnace temperature to 1200 ~ 1350 degrees, calcined reaction after 2 ~ 3 h, using liquid nitrogen to make it cool within 50 ~ 60 s to the 500 ~ 600 degrees, the heat preservation after 10 ~ 15 min, cool again to 100 ~ 250 degrees, heat preservation after 7 ~ 8 min, finally to 30 ~ 40 degrees, cooling heat preservation after 10 ~ 15 min, then put in mill grinding and 200 mesh sieve, can cast tungsten carbide powder preparation.

 

Posted by: hannahgwendolyn at 09:55 AM | No Comments | Add Comment
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October 24, 2018

Application of hot runner system of tungsten carbide nozzle in actual production

GF (glass fiber) is often needed to enhance the mechanical properties of PC materials in the actual production process of enterprises. As for the mold adopting the hot runner system, the wear of the nozzle of the hot runner system will be accelerated due to the addition of glass fiber in PC, resulting in a greatly reduced product qualification rate. This paper discusses the advantages of the hot runner system oftungsten carbide nozzlein the actual production aiming at the application of the hot runner system of tungsten carbide nozzle in the actual production. Mould is the basic industry of our country national economy, it is the important basic craft equipment of manufacturing industry. Mold manufacturing has an important position in the manufacturing industry, making the mold manufacturing capacity and technical level become an important standard to measure the national manufacturing level and innovation capacity. With the continuous progress of the society and the continuous development of the economy, a variety of commodities are produced continuously, most of which depend on the diversification of the mold. With the use of plastic products in society more and more extensive injection mold has become the most widely used mold type. With the continuous development of the society, people's requirements for environmental protection and plastic products are higher and higher. Therefore, mold adopting heat flow system should be born and widely used. The mold mainly adopts the hot runner system has the following advantages: (1) shortening the casting cycle. Because there is no restriction on the cooling time of the runner system, the parts can be produced in time after being formed and solidified. Many thin-walled parts produced by hot runner moulds can take less than 5 seconds to shape. (2) saving plastic materials. Because there is no cold runner in the pure hot runner mould, there is no production waste. This is particularly significant for reducing raw material costs. In fact, the main manufacturers of hot runner in the world are in the era of high prices of roommates and plastic raw materials have been rapidly developed. Because of the efficient way to reduce waste and cost of hot runner technology. (3) reduce waste and improve product quality. The temperature of plastic melt is controlled accurately in the system of hot runner mould. The plastic can flow into the cavities in a more uniform state to produce parts of uniform quality. In addition, the quality of the sprue is good, the residual stress is low and the deformation of the part is small. Therefore, many high quality products on the market are produced by hot runner mold. (4) eliminate subsequent processes, which is conducive to production automation. After the hot runner mold is formed, the finished product, without the need to trim the gate and recycle and process the cold runner, is conducive to the realization of production automation. (5) expand the scope of injection molding process application. Many advanced plastic forming processes are developed on the basis of hot runner technology.

 

The material of this product is PC, and glass fiber (GF) needs to be added to enhance the mechanical properties of the product. The product appearance cannot leave the mark of glue inlet, and the raw material of the product cannot be reused. It is well known that PC is a colorless or yellowish thermoplastic engineering plastic without fineness, odorless, non-toxic and high transparency. It has excellent physical and mechanical properties, good heat resistance and low temperature resistance, and stable mechanical properties and dimensional stability in a wide range of temperature. The most important processing method of this material is injection molding. When PC is using hot runner mould for injection molding, BECU is usually used for the material of the nozzle tip of hot runner. In general, no problems will occur in the production process. According to the requirements of the customer, the appearance of the product cannot leave gate marks and the raw materials cannot be reused, which decides that the mold should be designed and manufactured by using the hot runner system. Due to the influence of glass fiber added to PC material, the heat flow nozzle tip of the mold is made of BECU material. However, it was found in the production process that there was no problem with the products of the mold at the beginning of production. After a period of production, the products began to fail in large areas, and no obvious improvement was made after the equipment debugging. Thus it can be seen that the problem should be above the mold. It was found that the reason was that the nozzle tip of the hot flow nozzle was worn seriously, resulting in quality problems.

 

Related article:

http://www.wococarbide.com/Transaction/en_article_info/id/466.html

 

Posted by: hannahgwendolyn at 10:00 AM | No Comments | Add Comment
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