Explanation of Tungsten Heater for Vacuum Plating——Carrier Oil

Two processes carrier oil and drying and curing of tungsten heater for vacuum plating require the following notices. At first, in the respect of structure, part of the vacuum coating layer is composed of a layer (carrier oil), plating (coating) and surface (surface oil) three parts. Carrier oil are used to mask or make up for possible small defects on the surface of products, such as pinholes, pitting, scratches, etc., to provide a flat, smooth base surface for vacuum plating. On the other hand, it can improve the adhesion of the film, which play an important role for weak crystallinity, and poor adhesion of plastic film, such as polyethylene plastic and polypropylene plastic. In addition, the carrier oil can reduce or inhibit outgassing amount of volatile matter on a plastic surface, thus ensuring the quality of deposition.

This requires that the adhesion of carrier oil and plastics should be good, which cannot react chemically with the coating film, and have similar softening temperature to plastic parts. Carrier oil is actually lacquer type organic coating, usually use modified polyester-modified polyurethane varnish or paint as a base material. In process of the carrier oil, operators should maintain the cleanliness of injection mold parts, the oil should be uniform, do not gather the oil to avoid scratch. Workshop environment should keep dry, dust and moisture. When arrange the oil, it should be in strict accordance with the requirements of the process.

Vacuum plating process also includes derosination. Derosination is to clear dirt and greasy oil on the surface of the injection mold parts in order to ensure adequate coating milling inserts adhesion. General degreasing agent uses an organic solvent degreasing, selection principle of the organic solvent is not to prejudice the plastic surface, and it should evaporate quickly. In fact, in addition to the method of degreasing organic solvent, there are acidic degreasing, alkaline degreasing and others.

Cold Rolling Tungsten Copper Sheet

The cold rolling process of tungsten copper sheet not only has the advantages of low energy consumption, low equipment investment and high production efficiency, but also can rapidly improve the cold working plasticity of tungsten copper alloy.

Nowadays, the processing method of tungsten copper has lots of problems. For example: long production cycle, high energy consumption, most using equipment is the high power processing equipment, high investment, etc. The cold rolling of tungsten copper sheet not only can solve the problem of low energy consumption, but also can enhance productivity, shrink area, improve the processing Common Turning Inserts plasticity of tungsten copper.

The Crystallization of Ammonium Paratungstate

Ammonium paratungstate (APT) is an important tungsten intermediate product, mainly with white crystals.

 

It have flakes, needles and strips three kind, used in the manufacture of tungsten trioxide or blue tungsten oxide, TP,  also used for manufacturing ammonium metatungstate and other tungsten compounds.

Because the production of tungsten oxide, morphology and particle size of tungsten powder has genetic relationship with APT, so the production process is not only to the tungsten APT purification, but also to control the crystal morphology and particle size of paratungstate tungstate.

 

In the 1950s, in the book "Tungsten and Molybdenum Metallurgy" by A.H rickman, used the reaction 5(NH₄)₂O·12WO₃·nH₂O to describe the APT formula, used the evaporation crystallization process to get n=5 flaky crystal, and used the acid neutralization process for n=11 needle crystal. After that in China are all using this view, that of ammonium tungstate solution producing is a ammonia chemical process of paratungstate tungstate lost, the crystallization process of chemical reaction is:

 

12(NH₄)2WO₄===5(NH₄)₂O·12WO₃·5H₂O+2H₂O +14NH₃

 

(N=5 temperature> 50 °C to obtain flaky crystals)

 

12(NH₄)2WO₄+4H₂O===5(NH₄)₂O·12WO₃·11H₂O+1grooving Inserts 4NH₃

 

(N=11, temperature <50 °C to obtain needle-like crystals)

 

APT crystal water content and crystal shape depends on the crystallization conditions, the current study that APT has three crystalline morphology.

 

 APT·10H₂O is needle-like or strip-like orthorhombic structure, it is unstable in the industrial crystallization conditions, at least 50 °C below the crystal can be obtained in this crystal.

 

2. APT·12H₂O is a triad flake crystal, which is a crystal in the state of metastable state in water. It is a metastable phase at the boiling point of (NH₄) 2WO₄ solution, and only when the concentration of WO₃ in the solution is more than 30%, the concentration of NH₃ more than 5% of the conditions can be generated, with the extension of storage time, it will happen recrystallization and turn into APT·4 H₂O.

 

APT·4H₂O is a monoclinic cubic structure, which is always stable under industrial crystallization,  means from WO₃ concentration higher than 30%, NH₃ concentration is greater than 5% to WO₃ concentration less than 10%, in a solution of NH₃ was 1%, slightly better in 90-100 °C temperature range as long as there is APT·4 H₂O exists, the seed can produce APT·4 H₂O crystallization.