PARTING TOOL INSERTS,TURNING INSERT,TUNGSTEN CARBIDE INSERTS

How to Detect Internal Defects of Tungsten Crucible？

Due to the different maturity of manufacturing process for tungsten crucible, there are some potential problems of the finished products which are difficult to find. Wolfram crucible is mainly formed by the tungsten powder molding which requires a lot of pressure during the pressing process. With the increase of inner stress of tungsten Shoulder Milling Inserts product, the inside of wolfram crucible would crack. Therefore, after the manufacturing process of the wolfram crucible, inside of it should be carefully examined. The followings will give a brief introduction of the steps for detecting internal defects of wolfram crucible.

Phased array ultrasonic testing equipment is the essential tool for detecting internal defects of wolfram crucible which is divided into three parts, choosing the best configuration of phased array ultrasonic testing equipment to test them respectively by ultrasonic detecting. It takes a short time to finish the examination only for10 minutes, and the operation is not complicated, with a high effect that can be applied to large-scale wolfram crucible producing.

Since wall of wolfram crucible is thin with a large area, it can be detected by double crystal probe in phased array ultrasonic testing. The structure of wolfram crucible bottom is relatively simple with a smooth surface, so inspector can use a high-frequency linear probe to detect it. The structure of the junction between wolfram crucible wall and bottom of the crucible is complex, deformation surface is relatively large, so inspector can use high sensitivity test block for its detection which can detect the smallest equivalent of 0.2mm hole.

Because of the particularity of the manufacturing process of the wolfram crucible, it would cause instable quality of wolfram crucible. The inside of wolfram crucible is easy to have cracks, holes and other defects. If it cannot be noticed in time which would cause further more severe crack during application or lead to a wolfram crucible burst, even result in serious accidents. Therefore, the detection of internal defects of finished wolfram crucible is necessary. Detecting by this method can ensure quality of product, and the detection result of the method is more intuitive, the cost of the process is low and it’s suitable for large-scale industrial production of wolfram crucible. Quality of wolfram crucible directly determines the quality of the follow-up work. Development of testing technology for nondestructive wolfram crucible has a great significance for industry. People should think highly of its applications.

Studying Tungsten Trioxide Structural Phase Transition Law

Structural phase transition region is divided into two basic types: remodeling and displacement type. Such classification is based on the grid by the formation of chemical bonds through periodic phase change. Strictly speaking, the non-reconstruction-type structural phase transitions are classified as displacement. Obviously, this is difficult to include atoms, molecules, cells and equivalent groups in a deep potential. For the reconstruction phase transition, we can include structural changes in carbon, graphite and diamond, which including the reconstruction phase transition and displacement phase transition, order - disorder phase transition, hybrid phase transition, and electron-phonon interaction associated phase transition. Of course, it does not include the superconducting phase transition, because its system structure.

Structure of tungsten trioxide can be described as WO₆ octahedron vertices that sharing three-dimensional network structure, however, WO₃ symmetry is relatively low, because it is deformed over ReO₃ structure. The lattice phonons and electronic structure of the combined effect of the changes is produced by several crystalline phases, these types carbide cutting tools of crystalline phases are the evolution from low to high symmetry with increasing temperature.

By studying the structure of the tungsten trioxide phase transformation, the phase change can be found in its crystalline order: monoclinic Pc (ε- WO₃)→triclinic PT (ζ- WO₃)→orthogonal Pbcn (β- WO₃)  →quartet P4 / ncc (α- WO₃) → P4 / nmm, which presents different phase ramp in a different reaction temperature. In 2002, we found a new crystalline phase by continuous research. The high resolution neutron powder diffraction method confirms the existence of a new monoclinic phase at a temperature region of 720 ℃ to 790 ℃.

Bismuth Tungstate Photocatalyst Modification

In recent years, because bismuth tungstate (Bi₂WO₆) has narrower band gap and wider visible range than titanium dioxide (TiO₂), it has a great tendency to replace TiO₂.

 

 

However, in practical applications, it was found that bismuth tungate is good, but there are some shortcomings, mainly in its photogenerated electrons and holes easy to complex, quantum efficiency is not high. Therefore, scholars believe that bismuth tungstate should be added with some elements to excite the photocatalytic potential of bismuth tungstate.

 

Some scholars have made Au (Ag) / Bi₂WO₆ nanocomposites with bismuth tungstate doped with gold or silver. The results show that the degradation efficiency of RhB solution is 40% using Au (Ag) / Bi₂WO₆ nano photocatalyst, and the efficiency is 99.2%, higher than that of pure Bi₂WO₆.

 

Some scholars have suggested that the carbide cutting inserts Pt/Bi₂WO₆ composite can be used for photocatalytic degradation of Mo methyl orange by doping bismuth with platinum. The results show that the photocatalytic activity of Mo solution is reduced to 100% by using 0.3Pt/ Bi₂WO₆ composite photocatalyst, and the photocatalytic activity of the photocatalyst is still active and recyclable.

 

It is said that the nano crystalline Bi₂WO₆ powder is mixed with a small amount of TiO₂ powder and is hydrothermally mixed. The structure of the photocatalyst is still Bi₂WO₆ crystal structure, however, the properties of the two compounds show good visible light response range and catalytic activity.

 

Of course, if you think the doped TiO₂ material is too low, then change to the king of new material graphene, it is found that graphene is an excellent conductor, and graphene, as an efficient electron promoter, can be combined with Bi₂WO₆ catalyst to increase its light capture capability and enhance its catalytic capability. The results show that rGO/Bi₂WO₆ has a catalytic effect on dye wastewater. The decolorization rate is 92%, which is about 30% higher than that of pure bismuth tungstate.

 

Recently, some scholars have proposed a more comprehensive doping scheme, which is based on bismuth tungstate as the main catalyst and doped graphene and titanium dioxide. TiO₂ assisted Bi₂WO₆ to generate more holes, and graphene assisted Bi₂WO₆ to capture electrons. By combining, the potential of bismuth tungstate is fully activated. It not only has a photocatalytic rate of 99% of methyl waste water, but also has strong degradation ability to pesticide wastewater and organic wastewater.

 

With the development of bismuth tungstate photocatalyst, more bismuth tungstate photocatalytic activity will be improved in the future. In addition, another point to mention is that by chemical methods bismuth tungstate in polyester or acrylic fiber load, it is more favorable for the recovery and reuse of bismuth tungstate photocatalyst in practice.

 

Tungsten Carbide Ball Grinding Methods (1／2)

With the development of technology, the grinding methods of tungsten carbide ball are developing rapidly. There are conventional grinding methods (includes single V-slot, double V-slot and conical slot), fluid polishing (magnetic fluid, non-magnetic fluid) and high precision grinding (eccentric V-slot, active control of rotation), etc. Single V-slot grinding, the value of rotation angle depends on the angle and ball milled blank disc slot diameter, in a closed loop process almost from the corner does not change, and since the angle is very small, but only for a relatively compact carbide balls orientation change (i.e. ball billet rotation axis and the revolution axis angle of the same size) grinding motion.

The contact point of blank ball and polishing discs trace ball billet was formed on the surface of the center axis of the rotation axis of the ring. The defect of this method is that it can not ensure quickly billet surface grinding ball uniform, thereby reducing the efficiency and accuracy of carbide cemented carbide inserts and sphericity processing. Therefore, the related researchers modified in part designed to travel around the grinding disc moving grooves, making the ball spin axis changes can be made randomly. Compared with single V-slot grinding, both of the upper and lower grinding tray of tungsten carbide ball double V-slot grinding are V-shaped, while single V-slot only the lower grinding tray is V-shaped.

TIG welding and Tungsten Electrode Property Requirements

TIG welding is also known as inert gas shielded arc welding. It usually uses high melting point metal such as thorium tungsten, cerium tungsten, tungsten and other refractory metal as non-consumable electrode of electric arc, using inert gas as the medium of electric arc and protective atmosphere, so that weld pool and electric arc will not affected by air during welding. It was tungsten carbide inserts proposed in 1930 when aviation industry has strived to develop at that time. On the other hand, SMAW and SAW welding can not meet airline industry non-ferrous metal welding. Besides, atomic hydrogen welding is more dangerous, and there will be welding line problems. Therefore, in order to meet the aviation industry non-ferrous metal welding requirements, TIG emerged.

Using TIG welding for metal welding not only has stable arc length and tungsten electrode difficult to melt, but also it has good protect effect and reliable crafts. It is suitable for welding non-ferrous metals and their alloys and welding material thickness is generally less than 3mm. TIG welding equipment including: welding power supply, ignition unit and control system; protection gas supply device; cooling water; welding gun and so on.

Tungsten electrode is an important part of TIG welding. Tungsten electrodes, thorium tungsten electrodes, cerium tungsten electrodes, zirconium tungsten electrode, yttrium tungsten electrode, lanthanum tungsten electrode and other composite tungsten electrodes are usually used in TIG welding. Each tungsten electrodes species has its own characteristics. Depending on different welding application can take different tungsten electrodes type. Tungsten electrodes are used in TIG welding having some property requirements:
1. Arc is easy ignition and stable;
2. The arc happens at the electrode front-end, without cathode spots climbing;
3. During welding, electrode consumption and deformation will not affect the property of the arc.