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Tungsten alloy with high mechanical strength properties and good corrosion and wear resistance is used as metal electrodes for melting of kaolinit.
Long time ago, the ferrite-martensitic electrodes used involve the disadvantage that the molten weld metal has a very poor ductility immediately after welding. For this reason, in order to avoid crack formation, a preheating treatment had to be applied during the welding operation proper and a stress relieving had to be carried out immediately after the completion of the welding operation. In certain cases, when a subsequent tempering could not be carried out, the welding was performed with austenitic stainless electrodes. However, as these electrodes yield a weld metal with a yield point and a hardness substantially lower than of ferrite-martensitic electrodes, this method gave rise to problems in the welded construction under unfavorable operation conditions.
It has been discovered by a great number of experiments that it is possible to eliminate the disadvantages which are connected with the welding of stainless steels having a predominantly martensitic or ferrite-martensitic structure, by using a welding electrode of a special type of alloy so composed that it deposits a weld metal, the microstructure of which consists of ferrite, martensite and austenite, in combination with an extra low carbon content.
It is essential for the new electrode that at the same time as the carbon content is reduced to the lowest possible value, the alloying elements affecting the structure are to be kept within narrow limits and the ferrite forming elements be balanced in relation to the austenite forming elements according to instructions given in the following. By proceeding in this way, the welding electrode will yield a weld metal with a three-phase microstructure, composed of ferrite, martensite and austenite, which structure under the prerequisite conditions mentioned imparts to the weld metals its characteristic properties, viz. high mechanical strength properties in combination with good corrosion and wear resistance.
The new welding electrode shows a further characterizing property, viz. that the deposited weld metal allows for temperatures at stress relieving which are lower than those used at welding with conventional stainless electrodes. This results in great advantages in the manufacture of pressure vessels, reactors or other welded constructions where a stress relieving is desired. By stress relieving within said temperature range, there is only a minimum risk of deformation and distortions.
Kaolinite is a clay mineral with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in kaolinite are known as china clay or kaolin. (http://en.wikipedia.org/wiki/Kaolinite)
Thus, tungsten alloy becomes a very suitable material for electrons for melting kaolinite. So if you have any interest in this kind of products, please do not hesitate to contact us at saels@chinatungsten.com. Price will be offered based on size, density, quantity, hardness, and any other specific requirements.
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