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Brazing Tungsten Carbide Components

Details: Category: Tungsten Information; Published on Thursday, 11 September 2014 16:17; Written by jwy; Hits: 591

Tungsten carbide components are commonly joined to steels and other materials by brazing. Brazing involves placing a metallic braze alloy along with a fluxing agent between the components to be joined and then heating the assembly until the braze alloy melts and flows to fill completely the small gap between the two components. Soldering is similar to brazing, but is performed at lower temperatures with lower melting point alloys. Soldered joints, however, generally lack the mechanical or thermal strength to satisfy the requirements of many applications.

Although many variables determine the quality and strength of the bond between two brazed components, attention to a few important principles usually leads to a satisfactory result. Both the carbide and the steel components must be clean so that the molten braze alloy wets their surfaces completely and forms a strong chemical bond with each. Tungsten carbide components are often grit blasted, sanded, or ground to create clean, new surfaces, or plated or treated in salt baths to prepare the surfaces for brazing. Similarly, steel components are vapor degreased or cleaned with solvents or caustic solutions. The presence of any residual grease, oil, oxidation, dirt, or other surface contaminants adversely affects the wetting of component surfaces by the braze alloy and results in an inferior joint. Various tests of the flow of molten braze alloys over component surfaces are commonly used to assess the “brazeability” of the components. The relative importance of clean surfaces will, however, vary with the design and application of the brazed assembly.

Under the right conditions all common braze alloys from pure copper to silver alloys will readily wet cemented carbide surfaces. The most popular braze alloys (American Welding Society designations shown in parentheses) consist of approximately 50% silver and include alloys with cadmium (BAg-6), without cadmium (BAg-24), with manganese (BAg-22), and with tin (BAg-7). These alloys possess moderate melting points in the range 1150 to 1300ºF and can be purchased in wire, rod, or ribbon form or as a trimetal braze in which a copper shim is “sandwiched” between two layers of silver alloy. Braze alloy manufacturers are a good source of detailed information on the selection and use of these products.

For high temperature applications copper is typically used as the brazing material. Although copper has a lower tensile strength than the silver alloys at room temperature, copper retains much of its strength to temperatures approaching 1000ºF . If brazing is carried out in an oxidizing environment, borax is an effective flux for copper. Normally, however, copper brazing is performed in a hydrogen atmosphere where no flux is needed. Other high temperature brazes include high nickel alloys containing some chromium, boron, and silicon. These alloys flow at temperatures exceeding 1800ºF. It should be noted that high brazing temperatures may cause grain growth or other unwanted changes in the steel component.

Fluxes are generally used in combination with the braze alloy to minimize the oxidation of surfaces to be joined during the heating of the assembly. Both “white” and “black” fluxes are commonly used in combination with the silver alloys listed above. The two are similar except that the “black” flux has a higher boron content and therefore is more effective at higher brazing temperatures.

The basic brazing steps follow.

Lightly apply flux to the steel surface.

Position a precut piece of braze alloy on the steel and lightly coat with flux.

Position the tungsten carbide component and coat the outside surfaces with flux.

Heat the assembly evenly throughout its volume to the proper temperature.

Once the braze alloy is molten, jiggle the carbide slightly to allow any flux or fumes to escape. Do not press too firmly or the braze alloy will be forced out of the joint.

Allow the assembly to cool slowly. Make no attempt to cool the assembly quickly.

Wash off any excess flux with hot water.

The optimal thickness of a braze joint is believed to be about 0.004 inches. This thickness represents a compromise between the high strengths associated with very thin joints and the superior ability of thicker brazes to absorb thermal and mechanical strains acting on the joint. Brazing strains are minimized by brazing only one surface between the carbide and steel components. Cemented carbides expand and contract only about one-half as much as most steels. If the carbide component is constrained during either heating or cooling, excessive stresses can develop and failure by cracking may occur. If the braze joint consists of two or more surfaces, the design of the joint must allow the carbide component adequate room during heating and cooling. The brazing of a carbide ring to a steel core, for example, is a very tricky case. Brazing strains become more significant in larger or longer joints. In such cases, various design considerations are utilized alone or in combination to avoid the problem.

Methods of heating the assembly to be brazed include hand torches, batch furnaces, and high frequency induction coils. Torch flames should be somewhat reducing to minimize oxidation of component surfaces. It is important to heat the entire assembly uniformly to minimize thermal gradients and stresses and to reach, but not exceed the proper brazing temperature. Underheated brazes will not melt and flow properly. Overheating may cause low boiling point constituents in the braze alloy to boil off. This alters the properties of the alloy and may result in entrapped gas bubbles in the braze joint. Any environmental factor that influences the rates of heating and cooling of the braze joint must be controlled to insure that the quality of the braze joint does not vary.

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Tungsten Alloy Applications in the Military Industry

Details: Category: Tungsten Information; Published on Thursday, 11 September 2014 12:45; Written by yewq; Hits: 590

New materials, also known as Advanced Materials, refers to the new materials, which was found in recent successful studies and undergoing researches, with superior features, functions and able to meet the need of high-tech. Development of human history shows that material is the material basis and pilot of social development and the new material is a milestone of social progress.Materials technology has been a very important field in the world's national science and technology development planning, together with information technology, biotechnology, energy technology, are recognized as high-tech in today's society and for a long time dominate human technology. National defense force is often the prior user of new materials technology achievement, and the study and development of new material technology play a decisive role in the development of national's defense industry and weapon equipments.

The melting point of tungsten is the highest in metals, and its outstanding advantages is the high-temperature strength and crossion-resistance, which showing excellent properties inmilitary industry , especially weapon manufacturing.It is mainly used for manufacturing armor piercing bullet in weapon industry.

The armor-piercing bullet that in China's main battle tank 125 Ⅱ type is made of W-Ni-Fe, with variable density of sintering press, the average performance can achieve tensile strength 1200 MPa, elongation of more than 15%, tactical and technical index of 2000 meters homogeneous from the breakdown of 600 mm thick steel armor. Presently, tungsten alloys are widely used in large ratio armor-piercing in main battle tank, small and medium-caliber anti-aircraft penetrators and high-speed anti-piercing material , which makes this kind armor-piercing with more powerful breakdown.

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Tungsten Walking Fishing Sinkers

Details: Category: Tungsten Information; Published on Thursday, 11 September 2014 08:42; Written by Sherry; Hits: 538

These fishing sinkers are the bread and butter of many live-bait, walleye fisherman. They resemble a rectangle with rounded, outside edges. The top features an eye for the line. The fishing sinker's bottom is slightly wider and larger in size than the top, holding more weight. The bottom is also slightly rounded and bent upwards.

This weight distribution positions the sinker with its round edge on bottom, so it will easily glide over rocks, greatly reducing its changes of snagging on the bottom. The semi-flat design also prevents it from rolling along bottom in fast currents.

These sinkers are often used to drag live bait rigs along the bottom, and are sometimes called a live bait rig. To tie the rig, first thread the sinker on the line with the bottom bend pointing to the line's tag end.

Next, select a swivel large enough so it will not pass through the sinker's eye. Tie one end to your main line to the swivel. Then, you can add anything from a floating jig head, a plain hook, or a worm harness to complete the rig. This rig is not only snag-resistant, but it also allows line to slide through its eye when a fish picks up the bait.

This latter feature prevents a fish from feeling weight. Yet, when an angler keeps a tight line on the rig, the swivel will stop at the sinker's opening, allowing the leader's length to remain consistent and in the strike zone.

tungsten-fishing-weights

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Tungsten Alloys in the Construction of National Defense

Details: Category: Tungsten Information; Published on Thursday, 11 September 2014 11:58; Written by yewq; Hits: 568

1.In the aerospace industry applications. China developed the first generation of tungsten heavy alloy performance good in the 1960s, since immediately after the birth of self-developed China’s first artificial satellite navigation device has been successfully applied, then this new material has the first in China an intercontinental missile and developed by a variety of new fighters, helicopters, has been successfully applied. Developed to meet the needs of Chinese communications satellite, but also successfully developed a new type of density up to 18.5g/cm3 high proportion of tungsten-based alloys. A variety of high-performance W-Cu alloys in the rocket (missile) combustion chamber, nozzle, throat, rudder and other parts of the development of high temperature has been applied.

2.Military industrial applications. China has successful developed the W-Ni-Fe heavy alloy, provides of a variety of wear, shaped charge of the development a key material. W-Ni-Cu heavy alloys also play an important role in doing gyrorotor high proportion of material in China’s first nuclear submarine of the research and development.

3.In the civilian industry and nuclear industrial applications. In the nuclear power industry, used for nuclear reactor insulation and shielding materials, tungsten heavy alloy has a good prospect. In civilian industry, high-density tungsten alloy has been more widely used, mobile phones and golf oscillator rod weight will be a wide range of products. Processing done in the electric performance of the anvil block material to make electrical upsetting of hundredfold increase production efficiency, has significant economic benefits.

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Application of Tungsten Alloy Ball

Details: Category: Tungsten Information; Published on Wednesday, 10 September 2014 16:23; Written by jwy; Hits: 571

Tungsten alloy ball is used as the hunting shot for shotguns. A shotgun is a firearm that is usually using pellet filled shells instead of using bullets. The shot pellets from a shotgun spread upon leaving the barrel, and the power of the burning charge is divided among the pellets, which means that the energy of any one ball of shot is fairly low. In a hunting context, it makes shotguns useful primarily for hunting birds and other small games.

Advantages of Tungsten Alloy Ball in Military

Tungsten alloy ball provide a safer, non-toxic and environmentally friendly alternative to lead. Their higher density enables them to hold their shape better, even under extreme conditions. While depleted uranium offers comparable density, its volatile nature and the special licensing requirements needed for radioactive materials make working with it difficult and expensive. We offers a variety of high-density alloys, available as ROTF (Rough, Over-sized to Finish) material, bars, spheres, plates or rods. We also have extensive machining capabilities, allowing us to provide crankshaft weights in standard sizes or custom products finished to your exact specifications.

Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com

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Brazing Tungsten Carbide Components

Tungsten Alloy Applications in the Military Industry

Tungsten Walking Fishing Sinkers

Tungsten Alloys in the Construction of National Defense

Application of Tungsten Alloy Ball

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