Sintering Tungsten Boat

Introduction

Sintering tungsten boat is mainly applied in the manufacturing process of wolfram powder by anhydrous wolframic acid. Sintering W-boat is an important carrier for making powder. Or load ammonium paratungstate (APT) in firing W-boat to make tungsten powder, the APT is white crystal, which include schistose and acicular, it is applied in the manufacturing process of tungsten metal powder by anhydrous wolframic acid or blue tungsten oxide.

Manufacturing Process

Sintering tungsten boat is mainly prepared by welding. Firstly, soldering the tungsten plates at a high temperature to melt the joint of boat, and finally cooling it to form the finished sintering W-boat. Because sintering process requires high temperature, the soldering wolfram boat by welding has a good thermostability.

Application

Sintering W-boat is mainly used in the preparation of tungsten powder. The powder or powder compact is put into firing W-boat, which was then heated below the temperature of melting point of the essential ingredients, and then cooling it into room temperature. Sintering is divided into three stages, namely the low temperature burn-in step, the medium temperature firing step and keeping warm in a high temperature. In the low-temperature burn-in step is mainly to volatilize the gas and moisture content which is adsorbed in wolfram boat. Anhydrous wolframic acid is a raw material of wolfram powder, and W-boat is the carrier of it.

Advantages

At the time of firing, sintering tungsten boat can remove a portion of the harmful impurities, such as sulfur, potassium, sodium and others. This type of W-boat reduces the adverse effects of harmful ingredients (water, oxygen, nitrogen) of the product under vacuum sintering. It is in favor of eliminating the adsorbed gas and the residual gas of the pores which can promote post-sintering shrinkage.

Disadvantages

During sintering, due to the high temperature, sintering stove would emit large amounts of waste heat.

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Evaporating Tungsten Boat

Introduction

Evaporating tungsten boat is also known as coating tungsten boat which is widely applied in vapor deposition industry. Due to its high melting point, low saturated vapor pressure and stable chemical properties, this type of W-boat has been widely used as resistance evaporation source in vacuum evaporation coating industry. while evaporating or coating materials, the melting point of the material cannot higher than the melting point of wolfram boat. Evaporating W-boat, as an essential part for vacuum coating equipment, the selection of wolfram boat determines the quality of the coating.

Manufacturing Process

Evaporating is a kind of process to put semi-film forming matter in vacuum for evaporation or sublimation, so that the film can be separated out on the surface of workpiece or substrate. Manufacturing process of evaporating wolfram boat is similar to the process of stamping tungsten boat, the difference is that the former has the holes for exhalation on the cover.

Application

Evaporating W-boat is widely used as resistance evaporation source. Its working methods is to make tungsten film into the shape of the boat firstly, then install it in two electrodes. Add materials in the center of tungsten boat, and then energize the electrodes slowly. After the current pass tungsten boat, the tungsten boat will give out the heating power. Low voltage and high current would transfer the heating power to the coating material, when quantity of heat of tungsten boat is higher than the melting point of the coating material, the material would obtain the sublimation or evaporation.

Advantages

The appearance of the evaporating W-boat is similar to the stamping W-boat, except that the surface of the former has holes which is conducive to sublimation and evaporation and improve coating efficiency.

Disadvantages

Evaporating tungsten boat needs to operate at high vacuum environment, therefore the demand of work environment is relatively strict.

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Welding Tungsten Boat

Introduction

Welding tungsten boat is also called heating tungsten boat, which is made of tungsten plates through welding in a high temperature. This type of wolfram boat have pores for evaporating on each side which are very dense. Holes of the bottom of the boat are more scattered. It has a very high thermostability that the temperature is 2000℃. Since that this type of W-boat is welded by two or more tungsten plates, its size is large.

Manufacturing Process

Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. In order to improve the quality of welding wolfram boat, users can use argon, carbon dioxide and other gases to avoid atmosphere so that it can protect the arc and rate of furnace hearth while welding. Finally, a boat shape is formed by welding.

Advantages

Its size is relatively large, so it can be used for large-scale evaporation device or a large number of material evaporation. Compared to riveting tungsten boat, welding W-boat can save material of 10% -20%, and it doesn't need to scribing, drilling, assembling, and other complex processes.

Disadvantages

Since welding W-boat is made of two or more plates, which cannot be made on one time, so the preparation time will be longer.

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Folding Tungsten Boat

Introduction

Folding tungsten boat is formed by the repeated folding and forging, and folding the ends of tungsten plate. The permeability of W-boat is strong. Its two folding ends are a small corner or the shape of branch. Compared to other types of wolfram boats, folding tungsten boat consists of its cover and body. Generally speaking, there exists holes on its cover for evaporating which are circular holes, its diameter is 1mm, distance between holes is 2mm.

Manufacturing Process

While folding, the folded part should be consistent with the direction of the metal flow lines around. Starting location of folding is associated to radius of corner of semifinished product. If the corner radius is too small, at forming folded part may enter the interior, on the contrary, then it cannot be consistent with the same folded part. Firstly, the tungsten plate should be punched into the standardized size and thickness sheet, and then bend it into a certain angle at a high temperature heating. Finally process it into sizes that meet customer requirement.

Advantages

The ends of folding W-boat have been folded for many times, so that it have the function of reinforcement, improving the quality of this type W-boat, and look more attractive. Solid structure also makes it have a longer life. Folding tungsten boat is characterized by high hardness and toughness, the better effect of repeated using. Since the interface adopted in the coating process are larger than 1mm, the holes of its cover can effectively prevent material from spilling, ensuring the high quality of products, and saving raw materials.

Disadvantages

After quenching, it is able to cracking or becoming fatigue initiation while using. The end of the folded part is usually a small corner which would be out of shape or crack while forging.

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Stamping Tungsten Boat

Introduction

Stamping tungsten boat is mainly made by tungsten sheet through a high-temperature pressure whose price is relatively low. It is widely used in vacuum coating industry, sintering furnace, annealing boat industry and electronics industry for its good electrical conductivity, thermal conductivity, high temperature resistance and other excellent characteries.

Manufacturing Process

First of all, tungsten plate should be blended into a certain angle, or bending the blended workpiece again. After that, it should be pressed into any hollow shape by mould, or bending the hollow mould workpiece further deformation. Afterward the hole or the outer edge of tungsten plate should be folded into a straight wall by mould. Forcing an outward radial force on the hollow member by mould, so that the local diameter can be expanded. After expansion, pressing the outside-in radial pressure on the hollow member so to narrow the local diameter. Next, putting the bloom into the die cavity, squeeze it out from the gap of mould to form the hollow or solid workpiece. Roll the panel into a ball peen whose shape approximate to a close one. Finally, press the bended or stretched workpiece into a right W-boat shape.

Advantages

The main characteristic of the stamping W-boat is the high rate of final products. Because that this type of W-boat adopting the stamping equipment and stamping mould, the accuracy of size and shape the stamping wolfram crucible are much higher. What’s more, it has a long life time and it is not easily to be damaged, therefore, the shape of the W-boat from the same production batch is almost the same whose quality is also stable. On the other hand, pressure of stamping device is accurate, so that it will not damage the surface quality of the finished W-boat.

Disadvantages

During the stamping process, the device will produce noise and vibration which would have a great influence on operators. Furthermore, the mould is an essential material for stamping process, so the quality of the mould determines the quality of the W-boat.

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Tungsten Boat

Introduction

Tungsten boat is also known as evaporated tungsten boat or coated tungsten boat which is formed by tungsten sheet through high-pressure. Nowadays, W-boat is widely used in vacuum coating industry and sintering furnace and annealing boat industry. It is also widely used in electronics industry, such as kinescope, mirror making, toys, household appliances, mobile phones, electrical enclosure. It has good characteristics for electrical conductivity, thermal conductivity, high temperature resistance, wear resistance, corrosion resistance. Wolfram boat, as an essential part for vacuum coating equipment, the selection of it determines the quality of the coating.

Stamping Tungsten Boat

Stamping type tungsten boat is formed by conventional or special stamping equipment to put pressure on wolfram plate to produce plastic deformation in stamping die. The main processing of stamping W-boat is hot stamping. Tungsten boats made by stamping can increase its rigidity, because the press generally do not have chips and the consumption tungsten plate is less and the low cost, therefore, the price of stamping wolfram boat will be relatively low.

Folding Tungsten Boat

Manufacturing process of the folding tungsten boat is more complicated. Through the repeated folding and forging on tungsten plate, and then both ends of a tungsten plate will be folded, forming the shape of the boat. Folding wolfram boat has a strong permeability. Compared to other types of W-boat, this type of W-boat has a series of complement: cover and its body.

Welding Tungsten Boat

Welding W-boat is also known as heating wolfram boat. Welding is connected directly to connecting position of the two metals together by the melting at high temperature. Heating and pressing five pieces of tungsten plates at a high temperature so that the connection can be melted together, cooling it after welding, forming the final shape of the boat. However, it would take long time to produce a welding W-boat, because that it can be made for one time. Welding of pure tungsten is generally divided into fusion welding and braze. The sizeof this type of wolfram boat is relatively large.

Riveting Tungsten Boat

A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. Generally, using wolfram clinch bolts to connect two tungsten plates. Thus, the strength of riveted joints of riveting W-boat is stable and reliable that can improve the tightness of tungsten boat. In other words, riveting W-boat is made by two wolfram plates which have the same thickness, make a hole in the joint, and then use the wolfram clinch bolts to connect them so that the two tungsten plates can fit together. On the other hand, it can to form a complex structure of the tungsten boat.

Evaporating Tungsten Boat

Evaporating tungsten boat is widely used as source for evaporation resistance and component of the boat is made of tungsten metal. And then connect both ends of the component by wire, and put a low melting point metal in the middle of the concave position. Under the electrify condition, the temperature of tungsten boat would rise to about 2000 degrees, so that the metal can evaporate into gas and deposited on the surface of the workpiece.

Sintering Tungsten Boat

Sintering tungsten boat is mainly used in the production of tungsten powder. Burning ammonium into yellow tungsten oxide or blue tungsten oxide, and then make tungsten powder in hydrogen. During the manufacturing process, tungsten oxide should be placed in a tungsten boat and then put in the reduction furnace. After recycling the hydrogen, remove the tungsten boat.

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