Continued from the preceding paragraph, we will discuss the key technologies of tungsten copper composite powder warm compacting process according to the aspects above.

2. Lubricant: In the traditional process, lubricant used in general when the temperature was raised to 120-150 ℃, it is difficult to ensure the fluidity of the powder, the powder is mixed performance by a certain influence. Therefore, the choice of lubricant is also can not be ignored. It should meet the glass transition temperature of 130-150 ℃, low coefficient of friction (temperature, friction coefficient further reduced in favor of a metal powder and die wall friction and powder particles to a minimum, thereby reducing the pressure and pressing off clamping force), soluble in volatile solvents (powder dry and easy to make the surface of the powder particles uniformly coated with a thin layer of lubricant film), can effectively prevent or slow down the oxidation of tungsten-copper alloy powder (usually metal powder is oxidized, increased oxygen content will affect its final properties), the decomposition temperature range is wide (should be more gentle lysis, avoid large amounts of gas, resulting in the expansion of the volume of powder metallurgy parts), non-toxic lubricant after decomposition, do not pollute the environment .

3. Temperature Control: Temperature and pressure molding preheating temperature between 100 ~ 150 ℃. Because usually between room temperature and the temperature of hot pressing temperature is between, this has been known as warm compacting process. The temperature and pressure above the temperature control of the glass transition temperature of the polymer lubricant or below the melting point of the lubricant in the viscous flow state, both have a certain cohesiveness and some lubrication, it is conducive to the particle surface and spread flow. Whether temperature is too high or too low will destroy the lubricant film and caused failure.

Warm compacting process is a kind of new process of high precision powder metallurgy that develops based on conventional molding process. Compared with conventional process, warm compacting process is in the process of pressing the powder in a conventional method and the mold is heated to a certain temperature after pressing to obtain high-density powder compact, which achieves sintered body with high density and high performance. Warm compacting process can be suitable for whether iron-based materials or tungsten (W), copper (Cu), aluminum (Al) and other metal powder, which has many advantages, such as higher compacting and sintering density, uniform distribution, higher compacting strength, lower releasing pressure, lower spring back and cost. The influencing factors include the powder (apparent density, the granularity, the content and porosity, etc.), the choice of lubricant, the temperature and other parameters controlling, which are the key technologies to ensure the molding process. Next, we will discuss the key technologies of tungsten copper composite powder warm compacting process according to the aspects above.

1. Powder: The choice of powder includes that the granularity, the content, apparent density, the porosity and so on. Tungsten-copper composite powders for warm molding not only require good compressibility in heating, transport and pressing process, liquidity and stability constant bulk density, and require consistency between the performances of the parts made of It is also high. Particle size, size distribution and powder itself mixed powder formulations are to some extent determines the density of the material and non-porosity. Related foreign researchers developed a patented powder, heated at 130 ℃ to either incubated or in powder 130 ℃ under cooling to room temperature, warming cycle effect, the powder flowability and bulk density as well as 600MPa by pressing the blank density are very stable.

N Carbide and alloy performance is largely determined by the quality of tungsten trioxide. Common methods of preparing tungsten trioxide including the following major steps: first of all, removing palladium, silicon, fluorine, phosphorus, and molybdenum by solution purification, secondly, the precipitation of artificial scheelite is based on calcium chloride solution. Thirdly, using hydrochloric acid to decompose artificial scheelite; finally, the tungsten trioxide is prepared by washed, filtered, and dried steps. This article focuses on the methods of determination for palladium in high-purity tungsten trioxide.

The definition of Colorimetry is based on the color reaction of the colored compound by measuring or comparing. As a method of quantitative analysis, the basic requirements of the Colorimetry are: high sensitivity and selectivity, stable colored compound and different color. The color reaction and control of the reaction conditions is the key for colorimetric analysis.

Determination of palladium in High-Purity Tungsten Trioxide Method
Burning the high-purity tungsten trioxide at 1400 ℃, and the resultant of palladium sulfide reacts with oxygen form palladium dioxide. This compound is condensed with formaldehyde, and the purple compound can generate in 560nm colorimetric determination. The experiment of the color, the time and the sample of absorption time can reduce combustion conditions such as blank test. Finally, we can obtain the amount of available mercuric chloride, sodium, chromogenic agent, the influence of magenta and fading. Detection limit of this method is 0.5ppm; the relative standard deviation is ± 4.8%.

Ammonium paratungstate is chemical substance, and it is mainly white crystal. There are two kinds of sheet-like or needle-like, they are for the manufacture of yellow tungsten oxide or blue tungsten oxide powder. Ammonium paratungstate is used to make other tungsten compounds that are used in petrochemical industry, such as additive. The series of downstream products, such as tungsten and other electric vacuum materials; series of alloys, such as tungsten carbide, hard alloy, alloy blades, drill bits alloys, mold; wear, pressure, machinery and equipment and other high-temperature components.

Tungsten trioxide is an important η-type semiconductor oxide, it has a variety of crystal structure, and is has been applied in electrochromic, photochromic, sensing and catalysis, in which the quasi-spherical particle diameter of the tungsten trioxide is 100nm-700nm, spherical particle diameter of the tungsten trioxide is 20-200nm, both tungsten trioxide particles can be used as precursors nanometer tungsten carbide.

Vapor phase method is the most effective method for the preparation of nanostructures present; various vapor deposition techniques can form solid film, whiskers and particles. And a vapor deposition method from a high concentration of the reactants is not prepared in high purity product. But the disadvantage of the conventional vapor deposition method is very limited, since the product was collected under high vacuum or high temperature, continuous production can not be achieved. We make ammonium paratungstate as raw materials, argon as carrier, and combine innovative technology with calcination, in the vapor deposition; the reaction was collected in a low temperature region, the successful implementation produce a variety of WO₃ powders.

To study the process of tungsten carbide DTH drilling buttons that can be summarized as follows several stages:

Stage I: Cracks emerge, at this stage tungsten carbide buttons just contact with the rock surface, rock stress is transmitted to the contact surface has not been fully released, brittle failure in the contact surface, meanwhile accompanied by the generation of micro-cracks;

Stage II: With the increasing stress, the rock contacted with tungsten carbide button has plastic deformation and forms cracking area;

Stage III: On the boundary of the region will have been pulverized tensile stress cracks, and gradually developed into an initial crack, the crack will be increasing stress and further expansion;

Stage IV: With the increase of stress, both side of the initial crack formation and generates corresponding tensile stress crack, was extended obliquely downward;

Stage V: Cracks form a funnel-shaped expanding and consequential damage leap forward.

In addition, except that the study on the mechanism of tungsten carbide DTH drill buttons, we should also notice that although tungsten carbide buttons have higher hardness and impact resistance, it is brittle and has lower wear resistance. The main pattern of invalid is corrosion, which includes grain wear, surface fatigue wear as well as adhesive wear. It is mainly due to in the process of drilling, the high temperature of the high-speed collision with rock buttons occurrence arising will make carbide hardness decreased and crushed quartz particles made of a soft but opposed the hard phase transition occurs. Therefore, It also put forward tungsten carbide buttons higher requirements, which can be added some element or coated with a high-performance materials to improve the wear resistance of the tooth carbide buttons.

DTH drill bit is a kind of high-performance tool, which is also the one of the most widely used in excavation, rock drilling work. It is suitable for drilling hard, hard and abrasive rock formations, relying on high impact energy have a great impact energy of rock cracking. And it has so many advantages, such as high efficiency of drilling, high impact energy, has shear crash and longer service life; especially its driving force is based on airflow, which sufficient airflow can take away the rock debris from the bottom to improve the efficiency of drilling and reduce the abrasion of tungsten carbide buttons. As for the choice of tungsten carbide button becomes essential, to be considered in accordance with DTH drill diameter as well as the impact on other aspects of work, number and position of the buttons determines whether a reasonable share DTH drill the impact on power.

Theoretically, tungsten carbide buttons used for DTH drill uses rotary impact for rock drilling, It has short impacting time, the buttons in an instant contact with the rock produces a huge impact and brittle rocks internal stress concentration, under the action of impact force generated volume very easily broken so that the efficiency of DTH drill has been improved. Furthermore, tungsten carbide DTH drill buttons while also impact rock rocks rotary cutting button and drill the ball pure axial pressure is significantly smaller than rotary cutting bit, the button wear is also reduced a lot , thereby improving the wear resistance and grinding of carbide DTH drill buttons, extended service life.