The high-temperature chemical method of tungsten diiodide is legally produced by the reaction of elemental tungsten and elemental iodine at temperatures between 600 and 800°C: W+I₂→WI₂. Generally, the temperature selected for the reaction is 800°C, and tungsten diiodide is produced using the reaction of tungsten powder with iodine.

There are three direct preparation methods for tungsten diiodide, which are obtained by high-temperature chemotaxis, halide exchange reaction, and reaction of tungsten hexacarbonyl with elemental iodine. Meanwhile, tungsten diiodide can also be obtained by indirect method.

Tungsten diiodide (WI₂) has good stability at room temperature but readily reacts chemically at high temperatures and in the presence of oxygen. Tungsten diiodide is an inorganic compound with the following chemical properties.

Tungsten diiodide is a transition crystal. Transitional crystals are different from many substances in nature with regular geometrical shapes, such as ionic crystals, molecular crystals, atomic crystals, and metal crystals. The inter-particle role of the lattice junctions of the transitional crystals has changed, and the interactions between particles of the crystalline structure and the nature of the crystal between the different types of crystalline forms, which is difficult to be classified as any of the above-mentioned typical crystals, and there are a lot of actual crystals belonging to the transitional crystals.

Tungsten Diiodide is an inorganic compound with the molecular formula WI₂ and a relative molecular mass of 437.7. It is a metal salt of tungsten and hydroiodic acid, characterized by black or dark brown crystals, usually in powder or lump form. Tungsten diiodide has good solubility in alkalis but is insoluble in cold water, ethanol, and carbon disulfide. It has a density of 6.79 g/cm³ and a melting point of about 300°C, which allows it to remain stable at everyday ambient temperatures.

The solubility of tungsten diiodide has no specific pattern. For inorganic solvents, tungsten diiodide is soluble in alkali but insoluble in water at room temperature; for organic solvents, tungsten diiodide is insoluble in ethanol and carbon disulfide (CS₂).

Tungsten diiodide ( WI₂) is the iodide of tungsten (II), which is the metal salt of tungsten and hydroiodic acid. Its English name is Tungsten Diiodide, CAS number : 13470-17-2, relative molecular mass : 437.65.

Tungsten diiodide(IUPAC name: Tungsten Diiodide, molecular formula:WI₂) is an inorganic compound composed of tungsten and iodine after chemical reaction. The valence electron configuration of tungsten atom in tungsten diiodide is 5d⁴6s², which can form compounds with oxidation value from +2 to +6. Among them, the compounds with oxidation value of +6 are more stable. In tungsten diiodide, the valence state of tungsten is +2, and iodine is -1. So the molecule is composed of one tungsten atom and two iodine atoms.

To improve the service life of cemented carbide top hammer and pressure cylinder, thereby reducing hammer consumption:

1. Improve the performance of cemented carbide

(1) Increasing the cobalt content can improve the strength of the cemented carbide. From the comprehensive consideration of economic benefits, the cobalt content in a certain part can only be increased. Experiments show that increasing the cobalt content can improve the service life of the cemented carbide anvil and the pressure cylinder.

(2) The grain size of tungsten carbide has obvious influence on the performance of cemented carbide. With the increase of WC particle size, the compressive strength, hardness and elastic modulus decreased, while the flexural strength increased. Therefore, controlling the particle size of tungsten carbide is an effective way to improve the life and reduce the plastic deformation.

(3) If the structure of the cemented carbide is defective, it will cause stress concentration during synthesis, accelerate the fatigue failure of the anvil, and reduce its life. In order to improve the life of the top hammer, some alloying elements (such as niobium carbide, titanium carbide, vanadium carbide, tantalum carbide, etc.) The service life of the top hammer is greatly improved.

2. Change the shape of the top hammer

Some researchers suggested that if the flat-bottomed top hammer is changed to a spherical bottom, the strength of the spherical top hammer is better than that of the plane, because the uniformity of the force on the spherical top hammer is better, and the maximum tensile stress value acting on the 46° slope of the top hammer, The spherical surface is smaller than the flat surface, the maximum shear stress value acting on the central axis at 1/3 of the top hammer height from the top surface, the spherical surface is smaller than the flat surface, and the maximum compressive stress value on the 46° inclined surface is larger than that of the flat surface Small, changing the shape can also reduce the height of the anvil, save alloys, and reduce the "size effect". Therefore, changing the top hammer to a ball bottom can not only improve the stress distribution state in the top hammer body, reduce the peak value of external stress and thermal stress, improve the life of the top hammer, but also save alloy materials and reduce the "scale effect".

3. Carbide heat treatment

Heat treatment can improve the bending strength, impact toughness and durability of the top hammer, reduce brittle fracture, reduce porosity, increase density, reduce the source of fracture, and thus increase the service life of the top hammer. Heat treatment can change the magnetic properties, increase the coercive force and reduce the magnetic permeability. After heat treatment of fine-grained cemented carbide, the toughness will be improved, the loading deformation energy will be increased, and the durability in the high-pressure chamber will be improved.

4. Appropriately increase the thickness of the gasket

Increasing the thickness of the gasket is beneficial to prolong the life of the anvil. However, increasing the thickness is not arbitrary, and should be limited to not reducing the stability of the gasket and reducing the deformation of the gasket.

In order to achieve sufficient sealing conditions, improve the utilization rate of external load pressure and protect the function of the top hammer, it is required that the side length of the top hammer surface and the width of the chamfer and the side length of the pyrophyllite block have a certain proportional relationship, and the angle of the top hammer chamfer Be suitable. This is mainly to ensure that the pyrophyllite gasket has an appropriate width and thickness, an important condition for forming sufficient sealing force and reducing the influence of thermal stress, so as to achieve the effect of maintaining a constant pressure in the cavity and prolonging the service life of the anvil.

5. Improve the neutrality of the equipment, and adjust the anvil in place

Before starting up, check the centering synchronization of the equipment, ensure the accuracy of the pressure holding performance and the stability of the heating system, check whether the various parts of the press are normal, and the anvil must be accurately installed and debugged in place.

6. Cooling water cooling

Adding appropriate cooling water during synthesis can effectively lower the temperature and reduce thermal stress concentration.

7. Reduce synthesis pressure and temperature, shorten synthesis time

While ensuring the synthesis effect, try to reduce the pressure and temperature of the synthesis and shorten the synthesis time.

8. In order to eliminate the internal stress of the top hammer, it is recommended to put the top hammer and steel ring on hold for two or three months, and then use them after the internal stress is released to reduce longitudinal splitting or top hammer cracks and crushing.

9. The baking process of auxiliary materials such as pyrophyllite should be strictly controlled.

10. Adding a layer of protective metal Mo, Ti, etc. on the surface of the conductive top hammer can improve the temperature distribution of the top hammer, make the top hammer evenly heated, improve thermal stress concentration, and reduce hammer consumption.

11. Classify and use the top hammer, such as using ultrasonic and magnetic flaw detection to inspect the quality of cemented carbide molds. Those with micro defects are used for non-electric heating hammers, and those without defects are used for electrified heating hammers. This will prolong the service life of the top hammer Clearly there are benefits.

Tungsten carbide anvil is a key component for the synthesis of superhard materials such as artificial diamond by high temperature and high pressure (HPHT). The anvil is an important consumable inside the synthetic press, and the synthetic press is the core equipment for producing diamond single crystals and growing diamonds. Since the anvil is subjected to complex and severe compression, shearing, and tensile stresses, and the instantaneous temperature of the hammer surface reaches 500-600°C during heating, which requires nearly ten thousand times of repeated service life, the anvil is mostly made of tungsten drill series. Made of high-quality alloy, it has the characteristics of high hardness, good rigidity, high strength and excellent heat resistance.

The main products of synthetic diamonds include industrial diamonds and lab-grown diamonds. Among them, industrial diamonds are mainly used in mineral development, machinery manufacturing, household appliances, photovoltaic power generation and other fields; the application fields of cultivated diamonds include jewelry, precision optical instruments, cutting molds, optical materials, etc.

At present, one of the core high-pressure and high-temperature equipment for the production of synthetic diamond in my country is the six-sided top press, and the cemented carbide anvil is the key consumable inside the six-sided top press. The working principle of the cemented carbide top hammer is to equip a cemented carbide top hammer on each of the six sides of the six-sided top press. Under high temperature and high pressure conditions, the graphite in the high-pressure cavity is converted for the diamond process.

Grade

Grades suitable for cemented carbide anvils include YG6, YG8 and YG12x, etc. YG6 cemented carbide, the composition is 94%WC + 6%Co, mainly medium-sized WC powder and Co powder. The higher WC content of the hard phase ensures the compressive performance requirements of the cemented carbide anvil. However, the low content of Co in the binder phase affects the tensile strength of the anvil to a certain extent, and cracks are prone to occur during the diamond synthesis process. In addition, there are certain difficulties in controlling the C content of the YG6 cemented carbide anvil, and free C or η phases are prone to appear during the synthesis process, which affects the performance of the anvil; YG8 cemented carbide contains 92% WC And 8% Co belongs to medium grain cemented carbide, which not only has good compressive properties, but also has good tensile properties. It has a long service life, and there are fewer cases of cracking hammers in the early stage; YG12x cemented carbide is a kind of fine-grained cemented carbide. When the Co content is constant, the finer the grain size of WC, the corresponding density, The comprehensive properties such as hardness and compressive strength have been significantly improved, and it is an ideal one among cemented carbide anvil materials.

Performance

1. High hardness and compression resistance (HRA>85, bearing pressure above 5000MPa);

2. High strength and high toughness (the slope of the cemented carbide anvil must bear a large tensile stress > 35kg/mm2 when it is working);

3. High temperature resistance, wear resistance and corrosion resistance (in the process of synthesizing diamond, the transition temperature of C element is about 2000 ℃, and the added catalyst should not only facilitate the synthesis but also not react with the top hammer).

Chinatungsten Online (Xiamen) Manu. & Sales Corp. specializes in the production of hard paper alloy six-sided anvils, which can be customized according to customer sizes or samples (drawings).