Drilling hard rock with water jet is considered to be an efficient way to improve the work life of the cemented carbide blade. In this paper, cemented carbide material YG-6 is used on the drill bit in limestone drilling with water jet. Wear characteristics of the cemented carbide blades in drilling limestone with water jet is studied. Experiment results showed that the water jet pressure and nozzle diameter played an important influence on the wear rates of the cemented carbide blades in the drill bits.

The wear rates of YG-6 blades decreased when the jet pressure increased. But the decline speed of wear rates was not eve n, it declined more and more s lowly when t he jet pressure upon 10 M Pa. It w as also showed that wear rates decrease with the increase of the nozzle diameter in the drill bit , for the bigger nozzle diameter could provide  more impact force which could reduce the mechanical force on t he YG-6 b lades. SEM photographs were taken to characterize the wear mechanism of the cemented carbide blades in limestone drilling with water jet. Surface analysis demonstrated that cemented carbide blades in limestone drilling with water jet showed circular action of brittle fracture, grain pullout and polishing, which induced material removal process.

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Football tungsten dart rule is a fun game for two teams of 1-4 players. The rules are very simple, but the game is quite challenging.

The Object: The object is to be the first to score a predetermined number in a manner similar to American football.

The Scoring: One player from each team throws one dart a bulls-eye, closest to the bulls-eye goes first. The team names are written on the board in order and a 0 placed next to each name to indicate the current score. The teams pick a side of the board to be their "goal line", either 11 or 6.

The Play: Each team has four "downs" to try to move the ball across the board and into their opponent’s goal. Each down consist of three darts thrown and players on the team alternate for equal opportunity to play.

The playable area of the board is the Double-11, Large-11, Triple-11, Small-11, Bulls-eye, Double-Bulls-eye, Bulls-eye, Small-6, Triple-6, Large-6 and Double-6. One team’s goal line is the Double-11 and the other team's goal line is the Double-6. The Double-Bulls-eye is the "50 yard line".

The first team starts at their own goal line, for example Double-6. They try to hit one dart in each number in order across the board. The team plays all 4 of it downs (a total of 12 darts) in a row to try to move the ball as far across the field as possible. At the end of the 4 downs, the other teams "takes possession of the ball" where the original team left it and has 4 downs to try to move it back across the goal line.

If a team scores a goal (sequentially hitting all the target numbers across the board ending in the other team's goal line {the double 6 or 11}) that team earns 6 points and has an opportunity to throw for an extra point. An extra point is scored by throwing one dart in the 20.

After a goal is scored, the other team takes possession of the ball in its own goal regardless of how many darts or downs the scoring team had left.
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Strategy: Take your time and concentrate on the bulls-eyes. They are hard to hit, but once you get across, it's all down hill and the other team has to get the ball back across.
 

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Futbol tungsten dart rule is kind of an odd game that really sharpens your ability to hit bulls-eyes. This game can be played with 2 players or 2 teams.

The Object: To score at least the same number of points faster than your opponent was able to.

The Scoring: Four tallies are marked each side of the board to represent the four "downs" that the offense possesses the ball. The player’s names are written at the top of each column.

The Play: Both players throw one dart at bulls-eye, closest to the bull throws first and the option of "receiving the ball". If the player "receives" he will play offense first and try to score points. If the player chooses not to receive he will play defense and try to stop the other player from scoring too many points.

The offensive player throws first and tries to score as high a score as possible with three darts. The thin outer ring is the "double" and counts as two time the number scored. The thin inner ring is the "triple" and counts as three times the number scored. Any score 41 or greater is added to the offensive player's score.

Next, the defensive player throws three darts at bulls-eye. Any darts that hit the bulls-eye remove one down each (two if it is a double bulls-eye). Erase one tally from the offensive player's side for each bulls-eye the defense scored.

Play continues alternating players until the defense has removed all four downs from the offensive player. Once all four downs are removed, "possession of the ball" is turned over to the original defensive player. The offensive player now plays defense and the defensive player now plays offense.

The goal of the new offensive player is to score more points than the original offensive player scored.

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In accordance with a typical processing sequence, the tungsten containing particulated mineral concentrate is blended with an appropriate quantity of a powdered carbonaceous reducing agent in addition to a desired quantity of supplemental iron powder and/or iron oxide, whereafter appropriate quantities of binder are added. The resultant mixture is agglomerated into pellets of the desired size and shape and the green pellets are subsequently dried and transferred to a pellet storage hopper. The resultant pellets can be charged to a vacuum smelting furnace either on a batchwise basis or on a continuous basis, as may be desired, to effect a heating thereof to an elevated temperature in the absence of oxygen and under a relatively high vacuum so as to effect a direct reduction of the tungsten oxide constituents and any iron oxide constituents present and an extraction of the volatile contaminating constituents including the gaseous reaction products of the oxidized carbonaceous reducing agent, such as in the form of carbon monoxide. The vacuum furnace may suitably be evacuated employing a vacuum pump which preferably is of a steam ejector type and also effects a transfer of the vaporized constituents through suitable condensers for effecting a selected recovery thereof as by-products.

 

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It is also important that the briquettes or pellets formed are of sufficient green strength so that they will not crush or deform when loaded as a static three-dimensional bed in a vacuum furnace, thereby assuring the retention of the porosity of the bed through which the volatile constituents and gaseous reaction products can escape during the vacuum smelting reaction. Adequate green strength to enable a preliminary handling of the pellets, as well as providing the requisite final strength necessary during the initial stage of the vacuum smelting operation, can be imparted to the agglomerates by incorporating any one of a variety of inexpensive binder materials which volatilize without leaving any substantial residue under the temperature and vacuum conditions present in the reactor. For this purpose, binder materials including starches, gelatins, sugars, molasses, sodium silicate, etc., can be employed, of which a dilute molasses solution has been found as being particularly satisfactory. Such binder materials are generally incorporated in amounts ranging from about 2% up to about 10%, with the specific amount used in any particular situation varying in consideration of such factors as the particular size of the tungsten mineral concentrate particles, the manner of agglomerating the particulated mixture and the size of the resultant pellets desired.

 

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Preferably, the carbon reducing agent is employed in excess of that stoichiometrically required and is usually controlled within a stoichiometric ratio of from about 1.05 to about 1.20 times that theoretically required. Amounts of carbon above about 20% in excess of that stoichiometrically required are undesirable due to the retention of excessive carbon in the resultant ferrotungsten alloy pellets, rendering them less desirable as an alloying addition agent in some instances. It is also contemplated that small percentages of the carbonaceous reducing agent, such as carbon, can be incorporated when the iron bearing material comprises metallic iron powders for the purpose of reducing any oxides present on the iron particle surfaces. Generally employing the carbonaceous reducing agent in amount up to about 1% of the iron-bearing material employed is effective for this purpose and provides for ferrotungsten alloys of relatively high purity.

The mineral concentrate, the carbonaceous reducing agent and any supplemental iron-bearing constituent are blended mechanically in appropriate proportions to form a substantially homogeneous or uniform blend. It is important that the particulated mixture is first agglomerated into briquettes or pellets of a size which facilitates their handling and also assures the formation of a porous bed to permit an escape of the volatile constituents and gaseous reaction products of the oxidized reducing agent from the agglomerates during the vacuum smelting operation. The particular configuration and size of the pellets are not critical, and to some extent, will be dictated by the particular type of agglomerating process and equipment employed. Generally, pellets of a spherical configuration, such as derived from a disc-type pelletizing apparatus, having diameters ranging from about 1/8 inch up to about 1/2 inch, are satisfactory.

 

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When a metallic iron powder is employed as the iron-bearing constituent, the average particle size is not critical and may range from about 175 microns to about 74 microns, and preferably is controlled at an average particle size of about 125 microns to about 100 microns. When iron oxide is employed as the iron-bearing material, the iron oxide may suitably be introduced in the form of a fine-sized powder, preferably of an average particle size ranging from about 44 microns to about 10 microns. The iron oxide powder preferably comprises ferric oxide (Fe2 O3), which may be conveniently derived from sources such as millscale, a by-product of hot rolling steel, or the like. When all or a portion of the iron-bearing constituent is introduced in the form of an iron oxide compound, an appropriate amount of carbonaceous reducing material or reducing agent is incorporated in the mixture to effect a substantially complete reduction of the iron oxide to the corresponding metallic state.

In addition to the mineral concentrate and any iron-bearing material, if employed, the particulated mixture contains a fine-sized particulated carbonaceous reducing agent, of which carbon powder itself of an average particle size ranging from about 44 microns to about 10 microns constitutes the preferred material. The quantity of carbon or other carbonaceous reducing agent is employed in an amount at least equal to that stoichiometrically required to effect a substantially complete reduction of the tungsten oxide and any iron oxide present to the metallic state in accordance with the following typical reaction equations: WO3 + 3C ➝ W + 3CO 2Fe2 O3 + 6C ➝ 4Fe + 6CO

 

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Rare earth usually contains one or two kinds of Y, La, Ce, Pr, Gd, Nd, etc. And the main form of adding is rare earth metal, oxide or mixed rare earth. There are some improvements of rare earth: One is due to rare earth lively properties and easily combined with Oxygen nitrogen carbon and sulfur, tungsten carbide impurities will come into being rare earth compounds and distribute in the grain boundary, which prevent liquid Co phase from dissolving and moving grain boundary. Therefore, the region growth of WC grain has been suppressed and refines the particle.

The other one is due to the spherical compound and impurity elements combine to form a rare earth element, it played on the binder phase dispersion strengthening effect, which remove impurities further and purified grain boundaries. In addition, rare earth element can also reduce the sintering temperature of tungsten carbide nozzle, to reconcile the contradiction between grain growth and sintering density and remarkably improve the toughness and bending strength of tungsten carbide.

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Some scientists have developed a new type of inhibitor, which adds the insoluble metal carbides into Co-rich matrix to form a solid solution as inhibitors. It decrease the added inhibitors Co-rich carbide substrate drops below the melting point of 1200 ℃, and formed the stable metal / non-metal atoms in the liquid phase Co group, which is W, V, Cr / C radicals.

This radical prevent W atom and C atom from moving between the grains in liquid phase, which decreases the speed of WC grain growth further and improves the compactness and the lifespan of tungsten carbide buttons. Aside from the grain growth inhibitor above, rare earth element also serves as a common inhibitor used to inhibit tungsten carbide grain growth and improve properties of tungsten carbide nozzle during sintering.















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In addition to the tungsten containing mineral concentrate, the mixture may further contain controlled amounts of an iron-bearing material which may comprise a finely-divided iron powder or an iron oxide powder present in a controlled amount so as to adjust the total iron concentration in the particulated mixture to produce a resultant ferrotungsten alloy having the desired iron content. Ferrotungsten alloys usually contain iron concentrations of from about 0.2% up to about 20%. When employing mineral concentrates derived from wolframite or ferberite, which inherently contain iron concentrations of from about 10% to as high as about 20%, the addition of a supplemental iron bearing material to the particulated mixture is normally not required. However, when employing mineral concentrates derived from heubnerite or scheelite, or when higher iron concentrations are desired in the resultant ferrotungsten alloy, the mixture can be supplemented by the addition of a metallic iron powder or iron oxide powder, as well as a mixture thereof to provide the requisite iron concentration. When the mixture contains an excessive concentration of iron, a controlled amount of iron can be removed by volatilization during the vacuum smelting operation by employing temperatures in the upper portion of the permissible temperature range.

 

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