At present, the main way to inhibit grain growth Carbide nozzle WC powder is to add in an amount of grain growth inhibitor for controlling continuous and discontinuous situation WC grains growth. There are three methods of adding grain growth inhibitor: One is that adds in WC, Co and the inhibitor three kinds of powders at the same time during the powder wet grinding. Secondly, adds the inhibitor before W carbonizing. And the last one is to add grain growth inhibitor before WO_2.90（WO₃）reduction, which mix the inhibitor with the salt solution.

The first method is convenient and easily to achieve, which is suitable for industrial applications, but the inhibitory effect is worse than the other two methods. The second method, Cr element is sufficient on the WC subkingdom found in the carbonization process, and leads to the decomposition of WC particles, which can prevent WC grains from growing.






















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Tungsten carbide body drills are intended primarily for use in hand held, air or electric drill motors, in a sheet metal, thin wall tubing or any shallow hole drilling. Because of their short flute design and heavy web construction, they are considerably more rigid and durable than jobber or screw machine lengths. Tungsten carbide body drills breakage is significantly reduced or eliminated and tool life is greatly increased.

Style S – body drills 135° split point is used in hand or machine drilling without guide bushings, and where burring is not a problem. This point centers quickly and may be used successfully in tougher, harder materials.

Style F – body drills fishtail point is used in hand drilling thin material or machine drilling where the ratio of hole size to material thickness is very large, and where burr free holes are desired. A guide bushing must be used to center the drill point.

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This paper describes the fundamental theory, addition methods, optimum addition weight of scheelite instead of ferrotungsten in steelmaking and the yield of tungsten as well as the influence of using scheelite on the quality and the properties of steel. Results show that the optimum addition weight of scheelite is 5% W, the yield of tungsten is about 98 % and the economic and social benefit are obvious on the premise of having no influence on heat time and power consumption.

Scheelite is a calcium tungstate mineral with the chemical formula CaWO4. It is an important ore of tungsten. Well-formed crystals are sought by collectors and are occasionally fashioned into gemstones when suitably free of flaws. Scheelite has been synthesized via the Czochralski process; the material produced may be used to imitate diamond, as a scintillator, or as a solid state lasing medium. It was also used in radium paint in the same fashion as was zinc sulphide, and Thomas Edison invented a fluoroscope with a calcium tungstate-coated screen, making the images six times brighter that those with barium platinocyanide; the latter chemical allowed Röntgen to discover X-rays in early November 1895.


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Tungsten carbide tipped core drills four flute taper shank are core drills with increased flute capacity, remove more material from a cored or cast hole than a reamer. This often eliminates a final reaming or boring operation. Specifically designed for cast iron, non-ferrous and high temperature alloy applications. We offer a wide variety of carbide tipped and solid carbide cutting tools.

Used to enlarge and straighten cored or drilled holes. Because of their rigidity, these tools generate closer tolerance holes and better finish than standard drills. They may be used to enlarge holes as small as 60% of the tool diameter.

Core drills are made from a variety of materials that are chosen according to the degree of precision, hardness, durability and wear resistance required for your application.

Carbide tips cuts faster than high speed steel. It is commonly used on ferrous and nonferrous metals including cast iron, steel and steel alloy.

Solid carbide provides better rigidity than high speed steel. It is extremely heat resistant and used for high speed applications on cast iron, nonferrous materials, plastics and other tough-to-machine materials.

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Tungsten carbide rock drill bits are specially used in core drilling, and the cylindrical steel drill bits are covered by a layer of tungsten carbide. Threaded (screwed) connection core tube and water channel have been designed for it.

The ordinary tungsten carbide bits are suitable for drilling strata (formation) from Ⅱ to Ⅶ grade, and needle-like tungsten carbide bits are quite appropriate for drilling rocks from Ⅵ to Ⅷ grade.

Regarding the packaging, individual bit will be packed in a paper box, and a batch of this kind of bits will be packed in export-standard plywood boxes.

Features of Tungsten carbide rock drill bits:

1.They can be used in drilling complex objects, and high drilling velocity is always available.

2.The blades are made of high-performance carbide, which can greatly reduce the possibility of blade collapsing, as well as ensure good wear resistance.

3.Multi-layer geometric cutting edge is designed to improve its discharging property, as well as to lower its cutting resistance.

4.Various handle shapes are available in order to suit as many drill rigs as possible.

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Sodium hydroxide tests were performed to test the digestibility of the completely oxidized ferrotungsten material. Two digestion procedures were used, "low NaOH" and "high NaOH." The "low NaOH" tests were performed by adding the desired amount of NaOH to 0.2 1 of deionized (DI) water. The molar ratio of NaOH/W for each test is given in Table 1. Each "low NaOH" test was roughly sized for approximately 150 ml of 25% (8 to 9N) NaOH per 60 g of WO₃. The caustic solution was cooled to between 10° C. to 15° C. and the completely oxidized ferrotungsten material was added. After slurrying for 1 hour, the slurried material was added to a stainless steel reactor and digested at 120° C. for 4 hours. The slurry was diluted with 0.2 to 0.3 1 of DI water and filtered. The solids were slurried with about 0.3 1 of hot DI water for 1 hour and filtered. Both filtrates were combined and analyzed for tungsten by atomic absorbance (AA). The solids were analyzed by x-ray fluorescence (XRF). The "high NaOH" digestions were performed by adding the desired amount of NaOH to a stainless steel reactor and heating to 120° C. These tests were roughly sized for approximately 150 ml of 50% (.about.19N) NaOH per 60 g of contained WO₃. The completely oxidized ferrotungsten was slowly added to the reactor and digested for 3 hours. The slurry was diluted with 0.5 1 of DI water and filtered. The solids were twice slurried with 0.5 1 of DI water and filtered. A final wash was performed in the filter with 0.3 l of DI water. The filtrates were combined and analyzed by AA. Solids were analyzed by XRF. The results of the digestion tests are given in Table 1. The tungsten recovery efficiency is defined as the total tungsten recovered in solution divided by the sum of the tungsten recovered in solution and the tungsten remaining in the solids.


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In the first set experiments, approximately 100 grams of ferrotungsten was placed into a heated laboratory tube furnace. The oxygen content of the oxidizing gas flowing through the furnace was maintained at 20% by volume (balance nitrogen) while effects of different gas flow rates and furnace temperatures were evaluated. After two hours, the boat was removed and allowed to cool. Once, the weight of the partially oxidized ferrotungsten was recorded, the partially oxidized ferrotungsten was placed in a second tube furnace and completely oxidized (900° C., air (21% O₂) , 6 scfh). The final weight of the completely oxidized material was used to calculate the percent oxidation of the partially oxidized material at 2 hours. In the second set of experiments, the experimental setup was the same as the first except that the oxygen content was varied and the flow rate was fixed at 6 scfh.

FIG. 3 shows that the increase in the flow rate of gas through the furnace had a larger effect on the amount of oxidation after 2 hours than the increase in the furnace temperature. The highest percentage of oxidation after 2 hours was achieved using the combination of high temperature and high flow rate, i.e., 900° C. and 10 scfh. FIG. 4 shows that the increase in the oxygen content of the gas flowing through the furnace yielded a substantially greater percentage of oxidation after 2 hours than did the increase in furnace temperature. Again, the greatest amount of oxidation after 2 hours was obtained using the combination of higher O₂ content and higher furnace temperature, i.e., 30% O₂ and 900° C. Thus, the results of both experiments indicate that increasing the oxygen content of the furnace atmosphere either by increasing the flow rate of the oxygen containing gas or by increasing the oxygen content of the gas itself can significantly improve the oxidation rate.


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The effect of particle size on the oxidation rate of ferrotungsten was determined using a procedure similar to the method used to evaluate the effect of temperature on the oxidation rate. In this set of experiments, the furnace temperature was maintained at a constant 950° C. and the crucibles were removed at approximately 1 hour intervals. The ferrotungsten was separated into five fractions by sieving through a series of screens. The screens sizes were "big," 1/4 mesh, 10 mesh, and 30 mesh. The "big" screen had diamond shaped opening measuring 5/16 by 7/8 inches. The oxidation curves for the different fractions are given in FIG. 2. The finer fractions (-30 mesh, +30 to -10 mesh, and +10 to -1/4) appear to completely oxidize in about 9.5 hours. The two larger fractions require a much longer time, approximately 23 hours. Accordingly, it is desirable to reduce the particle size of the ferrotungsten to -1/4 mesh in order to minimize the time required to completely oxidize the ferrotungsten.

Two additional sets of experiments were conducted in a laboratory tube furnace to determine the effect of the gas flow rate and oxygen content of the gas on the rate of oxidation. Collectively, both parameters dictate the amount of oxygen present in the furnace atmosphere during oxidation.


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FIG. 1 demonstrates the effect of temperature on the oxidation rate of ferrotungsten. In FIG. 1, the percent weight gain of the ferrotungsten (FeW) at different temperatures is plotted against time. The data in FIG. 1 reveal that there is a significant increase in the oxidation rate of ferrotungsten above about 900° C. Unfortunately, the increase rate of oxidation at higher temperatures becomes limited by the ability of the calciner to effectively operate at the higher temperatures while handling production quantities of ferrotungsten. For a typical commercial calciner, the calciner is normally limited to operating at temperatures less than about 1000° C. because the calciner tube must be made out of alloys which have sufficient strength to handle the heavy and abrasive ferrotungsten. This excludes higher temperature tube materials such as alumina and silicon carbide which do not possess the needed strength. Therefore, to increase the rate of oxidation further, it is necessary to either decrease the particle size of the ferrotungsten being calcined or increase the oxygen content of the calciner atmosphere. The effects of these parameters on the oxidation rate of ferrotungsten are described below.

FIG. 1 is a graphical representation of the effect of temperature on the oxidation of ferrotungsten.


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The rate of oxidation can be further enhanced by reducing the ferrotungsten particle size to -1/4 mesh size. The size reduction may be achieved by mechanical milling or sieving to remove the larger fraction. Additionally, the rate of oxidation may also be increased by enhancing the concentration of oxygen in the calciner atmosphere. This may be accomplished by increasing the flow rate of the oxidizing gas into the calciner or by augmenting the amount of oxygen in the gas.

The following examples are provided to enable those skilled in the art to more clearly understand and practice the invention. These examples should not be considered as a limitation upon the scope of the invention, but merely as being illustrative and representative thereof.

Oxidation tests on representative ferrotungsten samples were performed in air at different temperatures in a muffle furnace. Samples of ferrotungsten were weighed and placed in previously weighed crucibles. The crucibles were then placed in a muffle furnace which had been heated to the desired temperature. The crucibles were removed at approximately 2 hours intervals, cooled, and weighed. Heating in the muffle furnace was continued until no further weight gain was observed. The data for these experiments are represented in FIG. 1.

FIG. 1 is a graphical representation of the effect of temperature on the oxidation of ferrotungsten.


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