Stamping Tungsten Crucible

Introduction

Because of manufacturing process of stamping wolfram crucible is simple, production cost is relatively low. It does not require the operator to have a high level of skill but can quickly produce a large number of wolfram crucible with a high production efficiency. Surface quality of the stamping tungsten crucible.

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 accuracy of its size and shape are much better than others.What’s more, stamping wolfram crucible has a long life time that is not easily to be damaged, therefore, shape of the W-boat from the same production batch is exactly alike whose quality is also stable.

Disadvantages

During the stamping process, the device will produce noise and vibration which would have a great influence on operators.

Physical Properties

Stamping tungsten crucible's density is about 18.5-19.0g / cm3, the outer diameter is 50-300mm and the tungsten content is above 99.95%.

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Riveting Tungsten Boat

Introduction

Riveting two tungsten plates with rivet to form the shape of tungsten boat. The manufacturing processes are drilling holes → (burring) → inserting rivets → using backform up to the rivets → forming the final product with rivet bucker. A great strength is the main character of riveting wolfram boat, due to the rivet connection, the connection tightness of its joint is better. Riveting W-boat can be formed to a large size.

Manufacturing Process

Riveting can be divided into active riveting, fixed riveting, sealing riveting. Active riveting conjunction can be rotated with each other, whose flexibility is strong. Conjunction of fixed riveting cannot active. Sealing riveting is to use lockbolts, threaded hollow rivets, self-plugging rivets in some parts which require no oil leaking, water leaking and gas leaking. Firstly drilling holes in the connection part of tungsten plate, and then burring. Next is to insert the wolfram rivets, and finally against the rivet with backform, using rivet bucker to form wolfram boat.

Advantages

The riveting and bolting joint of riveting W-boat belong detachable connection, so it is possible to change the vulnerable parts which has a good sealing performance. Tungsten boat made by sealing riveting can greatly eliminate the gap of its structure, blocking pathways of leaking. It is easy for riveting W-boat to check and rectify the fault. Tool using is flexible, simple and inexpensive.

Disadvantages

Geometry of rivet and BHF and clearance of concave die have a greater impact on the quality of riveting.

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Spinning Tungsten Crucible

Introduction

Flat and hollow billets are fixed at spinning machine, and then heat mix flame which consists of hydrogen and compressed air, after spinning it for some times, wolfram plate becomes the shape of the crucible. Wall of spinning W-crucible is thick which would cling to the mould. It has a high density, but due to the slow development of it manufacturing process, the process maturity is not enough.

Manufacturing Process

When use this method for making tungsten crucible, users should prepare tungsten billet before. And then make it into a sheet which conforms to the design by hot-rolling process to hot-rolled, and process it into a few pieces of wafers, and put it on a hot spinning machine. After that heat mix flame which consists of hydrogen and compressed air at the temperature of 1000℃. After spinning it for a few times, tungsten plate becomes the shape of the crucible, and freeze it.

Advantages

Spinning tungsten crucible have the characteristics of high density, low roughness of surface, good quality, a good tensile strength as well as an excellent hardness

Disadvantages

Due to complexity of hot rolling process and the spinning process, it is difficult to operate.

Physical Properties

Spinning tungsten crucible's density is about 18.5-19.0 g/cm3, the outer diameter is 50-300 mm and the tungsten content is above 99.95%.

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Sintering Tungsten Crucible

Introduction

Sintering refers to a traditional process of processing the powdery raw materials into the dense bodies. Generally, after preparing powder, the dense body can be obtained by sintering which is a polycrystalline material, the microstructure of it consists of the vitrella, vitreous composition and porosity. Sintering process directly affect grain size, pore size distribution of the shape of the vitrellathe of microstructure. Raw materials of sintering wolfram crucible is W-powder. Sintering wolfram crucible can be characterized by the large-size production.

Manufacturing Process

Today one of the main preparation method of industrial production of tungsten crucible is sintering. Firstly, install mould in accordance with the required dimensions, and then put wolfram powder which achieve the national standard in mould and seal it up. Next is to put it in an isostatic-press with a pressure of 180-250 MPa to press. After that, put the press compact in high-temperature sintering furnace with 80-150 ℃ / h for holding 4-8 hours. Finally, the product is processed in accordance with the requirements. After processing, inspect the appearance, size, density and other quality of finished product.

Advantages

The size of sintering tungsten crucible is much bigger. Compared to stamping tungsten crucible, it has a longer life, more stable quality which is well received by many manufacturers. In china, the manufacturing process of large-sized sintering wolfram crucible has reached the international advanced level, therefore,the quality and productivity of this type are also at a high level.

Disadvantages

During the process, due to the change of materials in frequency sintering furnace would decrease, temperature difference between its inside and outside is relatively large, resulting that temperature will be greater different at different points when measure it . This makes it difficult to reflect the true temperature of tungsten crucible.

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Forging Tungsten Crucible

Introduction

Forging method has a long history whose processing is more mature. Therefore, forging tungsten crucible has a high density which is generally above 19.0 g/cm3 and a good performance. What's more, due to its density almost reach ideal theoretical density with a long time, so the properties of the high tensile strength and high-temperature resistance deformation of forging W-crucible are better than other types of wolfram crucibles.

Manufacturing Process

Forging process is a manufacturing process involving the shaping of metal using localized compressive forces. Adopting this process to make tungsten crucible mainly consist of three steps: billet preparation, forging and machining. In general, the relative density of the billet is between 90% and 95%. In the preparation of the billet, the size and quality of the wolfram rod are needed to calculate in accordance with the requirements of the finished product. Then put the wolfram rod in a hydrogen furnace to heat under a temperature of 1400-1600 ℃. After keeping warm for a while, forging the billet, and then repeated heating and forging billets for some times until the size of billet meet the requirements. After the forging, the billet can be annealed, and then processed in accordance with the size and the outlook of the finished product.

Advantages

Forging wolfram crucible is formed through thick wolfram particles hit crumbled into small and uniform tungsten particles, and each of them tightly compacted together. After forging the the original pores, the internal organization of the crucible would be firmer, so this type W-crucible has a high density, and a long using time.

Disadvantages

Affected by equipment and forging process, size of forging wolfram crucible is relatively small, generally less than a diameter of 100 mm.

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Electron Gun Filament

Introduction

A small amount of tungsten is used as heating material for high-temperature furnace, the heaters of electron tubes and rib reinforcement of composites. Most of them are used as the filament for incandescent lamps and halogen lamps and gas discharge lamp electrodes. As a gas discharge lamp electrodes, in order to reduce work function of electron, tungsten or tungsten rods shall be added 0.5% to 3% of thorium which called thorium tungsten wire. The properties of electron gun filament include its small size, non-sagging, good breaking resistance. On the one hand, it has a nice corrosion resistance. On the other hand, the electron gun filament has a long life for plating as well as the high thermal conductivity.

Classifications of Electron Gun Filament

Electron gun filament mainly consists of filament, cathode and grid configuration which can be divided into six types: mosquito coils, pull-type, U-shaped, U-shaped with folding tails, half-moon and straight shape.

Applications of Electron Gun Filament

1. Electron gun filament can be used for filament cathode tube emission. The electron gun filament can be applied to the filament cathode tube emission, under bombardment on kV high voltage conditions, electron gun filament can emitting a large number of electron by heating the filament and the cathode.

2. Electron gun filament can be applied in vacuum coating. A vacuum coating is a kind of technology, which can produce the thin film material by physical method. The electron beam heating has a higher flux density than that of the electric heating. What’s more, the electron beam can evaporate the high melting point materials. The kinetic energy of evaporating particles of the electron beam tungsten filament is large.

Actually, electron gun tungsten filament has extensive application in many fields. But people should know the correct way to use it, or its properties would be decreased.

Electron Gun Filament and Cathode

The cathode is the most important part of the electron gun filament whose quality directly determine on the quality of the electron gun filament. Cathode of electron gun filament means refers to the pole that gains electrons which would produce reduction reactions. Under the same emission intensity conditions, if the work function of materials is lower, then it can greatly reduce the temperature of the electron gun filament, so that it would be better to maintain the use of the electron gun filament. If you want to extend the life time of the electron gun filament, you need a higher melting point and a smaller evaporation rate cathode materials.

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