Metallurgy Of Tungsten Carbide Powder

In recent years, metallurgy technology of tungsten carbide powder developed rapidly. Sintered casting, temperature and pressure skills, injection molding, sinter hardening are used more and more widely. At present, powder casting is a primary forming skills in tungsten carbide powder metallurgy mechanical parts industry. Its shape has been changed by hot forging or cold forging. It has completed high density.

Chinese car and motorcycle market have very great potential. On one side, the motorcycle is still occupy the first market. But with a series of resolution and plan have been carried out, motorcycle market will be further expanded in the China West. On the other hand, the current national car market carried out another round of market competition.The revival and development of this occupation offered key point to tungsten carbide powder metallurgy.

From the international development trend, carbonized tungsten powder metallurgy gear can reduce the advantages of parts components and attracted more and more attention to the field due to its cheap price. For example, the number of each tungsten carbide powder metallurgy part in car has been increased quickly in the area of north America and Europe since 1990.

  

Improve Service Life Of Tungsten Carbide Die

Tungsten carbide die a kind of composite material that made by powder metallurgy method. Tungsten carbide has high hardness and good wear resistance. It owns high elastic modulus and working temperature. Tungsten carbide can made for som dies. While the service life of dies also could improved several times and even more than dozens of times. Tungsten carbide is regarded as die material, and is mainly used for drawing die, cold extrusion with little impact force and cold punching mold. At present, China can produce each types of tungsten carbide and basically meet the needs of the domestic market.

In order to improve the service life of tungsten carbide die, people had better pay attention to following tips.

Firstly, the selection of tungsten carbide die and hot treatment for insert all should obey the rule of national standards and specifications. At the same time, people who use the tungsten carbide die had better maintain it in time and ensure that the die steel will not be rust and alloy core oxidation. Secondly, structure of tungsten carbide die must be reasonable. Finally, it must be precise in the process of manufacture. And tolerances is required to control strictly.

Return Tungsten Processing Method

The sprayed surface need to remove after tungsten carbide body service and spray again. That could make the workpiece repaired. Ordinary  mechanical processing is difficult to remove tungsten carbide surface. Because hardness of tungsten carbide surface can reach about HV1400 which is too hard.

People usually adopt chemical method to remove tungsten. Such as hydrofluoric acid, nitric acid, hydrochloric acid. But these chemical substances is very harmful to the human body. High concentrations of hydrochloric acid can cause chronic poisoning, rhinitis, bronchitis, emphysema and other disease. Some will even get allergies, dermatitis, eczema and so on. Hydrochloric acid is very volatile and it can reaction with the water vapor in the air. Then forming hydrochloric acid fog and sodium hypochlorite. These are perishable goods and harm to human body, plants and animals. Certainly they have a damaging effect on the workpiece surface.

There is another method to remove tungsten without any harm to human body. While it is also non-toxic, environmental protection and in low cost. Firstly cleaning the tungsten carbide workpieces. Use cleaning fluid to clean the tungsten carbide workpieces and then use clear water to wash. Secondly Make the tungsten carbide workpiece clamped. So the tungsten carbide workpiece can rotatable fixed in the electrolysis groove. Thirdly prepare electrolyte and remove the coating. Finally washing the tungsten carbide workpiece with clear water.

Wear Principle Of Tungsten Carbide Balls

Tungsten carbide balls can made for shotgun cartridges. The shotgun cartridge is not same as ordinary cartridge. It is a ball full of something. The bullet is dispersed into many small balls when shoot from gun muzzle. Explosive power is acting on each balls. Every ball has lower energy. In the hunting activities, people are usually main for shooting birds or other small animals.

Mill ball produces amounts and relative sliding after it has loaded. The connect surface temperature of mill ball parts become rise and oxidation also become more quickly. From the test, we all know that the release energy in the process of fretting wear has been mostly used up with heating. Fretting wear area of mill steel ball often appear fatigue crack. But the contact stress is only produced in the shallow surface of the ball. And generally speaking, these crackles will no longer extension.

Fretting wear of the steel ball mill is difficult to eliminate completely. However take proper measures can reduce the wear degree. Such as reduce the fretting contact area, mill ball change to the whole structure, some of connect surface hardening, improve the ball tube finish, spray hard metal on the surface, improve the mill steel ball contact stress or increase the friction between the contact surfaces. Adding the material with high elastic strain limit can uptake fretting amplitude. This can  prevent the ball tube fretting wear.

Advantages And Disadvantages Of Tungsten Carbide Roll Rings

Tungsten carbide roll rings are also called hard alloy roll ring. They have good performance, stable quality, high precision processing and good  impact resistance and wear resistance.

Tungsten carbide roll rings have high hardness and its hardness variation with temperature is very small. Hardness value is four times of high speed steel at 700 ℃. But the elastic modulus, compressive strength, flexural strength and thermal conductivity are all higher than the tool steel more than one times. The hard alloy roll has high thermal conductivity, so the cooling effect is good. Hard alloy roll are more resistant to corrosion and thermal fatigue resistance than the tool steel roller.

Tungsten carbide roll rings have many advantages. Firstly they can improve the quality of steel products and make the surface quality and dimensional tolerances improved thoroughly. Secondly they can reduce replace times and down time. Certainly they can reduce the scrap rate and the labor intensity of the production workshop. Finally reduce the cost is an effective way for enterprises to increase.

However tungsten carbide roll rings have high sensitivity to crack and unable to withstand cold and hot with high hardness and big brittleness. Otherwise it easily to lead destructive accidents.

Tungsten carbide balls can made for shotgun cartridges. The shotgun cartridge is not same as ordinary cartridge. It is a ball full of something. The bullet is dispersed into many small balls when shoot from gun muzzle. Explosive power is acting on each balls. Every ball has lower energy. In the hunting activities, people are usually main for shooting birds or other small animals.

Mill ball produces amounts and relative sliding after it has loaded. The connect surface temperature of mill ball parts become rise and oxidation also become more quickly. From the test, we all know that the release energy in the process of fretting wear has been mostly used up with heating. Fretting wear area of mill steel ball often appear fatigue crack. But the contact stress is only produced in the shallow surface of the ball. And generally speaking, these crackles will no longer extension.

Fretting wear of the steel ball mill is difficult to eliminate completely. However take proper measures can reduce the wear degree. Such as reduce the fretting contact area, mill ball change to the whole structure, some of connect surface hardening, improve the ball tube finish, spray hard metal on the surface, improve the mill steel ball contact stress or increase the friction between the contact surfaces. Adding the material with high elastic strain limit can uptake fretting amplitude. This can  prevent the ball tube fretting wear.

Tungsten Carbide Blade Needs Improvement

The current machine development trend is high speed, high precision and high quality. High speed operation has more and more high requirement to mold, cutting tools, surface treatment. Prolong the service life, reduce the production cost and create higher profits are the common goal that the industry pursuit. The improvement of cutting tool has become an important factor in order to meet the high speed machining, save processing time and cost. Tungsten carbide blade has high wear resistance and hardness. You must choose the appropriate surface treatment to get best benefit from processing.
This part is usually used for cold forging punch, hydraulic drawing die, tungsten carbide wire drawing, pump tube. Titanium aluminum nitride with high aluminum content is very easy to be formed alumina dura on the surface. This film can make the oxidation temperature up to 923 degrees. And can protect tungsten carbide blade keep hardness under the high temperature. However titanium nitride and titanium carbon nitride will also generate titanium oxide film at high temperatures. It is not easy to adhesion in epidural.That make dura lack of protection, oxidation rapidly and degradation.
So no matter under high temperature or low temperature, the surface treatment of coating must choose appropriate thermal treatment  and stable substrates. And also with  grinding and precision polishing processing. At present super high temperature resin binder still can not meet the requirements of mass production tool fully. There is still room for the quantity and quality to further development.

Notes For High Tungsten Carbide Roll Ring

Tungsten carbide roll ring is a roll which is regard tungsten carbide and cobalt as materials and made by powder metallurgy method. There are some tips for using the tungsten carbide roll rings. Firstly the cooling water should be accurately rushed to the trough. Secondly you should check the groove wear after rolling. Finally stop to supply water until red steel completely finished or pile of steel rolling cooling.
When you need to change the tungsten carbide roll rings, you can change according to the following steps:
1.Review whether the specifications, roller diameter and processing of backup roll ring can meet production requirements.
2.Check all install equipment and tools to ensure they can work normally and carry the good roll rings to the assembly trolley.
3.Take the mill shaft protection sleeve after the mill stopped, use a hydraulic motor to change the roll ring. And remove it with special hoisting tool, then put to the assembly.
4.Use acetone and the cutting of toilet paper to clean mill shaft and roller ring gasket until clean without dirt.
5.After a reasonable set of roll gap, put the cleaning roller ring along the roller shaft and cone sleeve flat head until it touches the roll ring gasket.
6.Using special roller tool to make the roll ring pressing. The pressure indicated by  pressure gauge should be consistent in the removing and installing roll process.
7. Ensure the mill flush alignment of groove and has not been blocked.