The most common grain growth inhibitors are VC, Cr₃C₂, TaC, TiC, NbC and so on. The inhibitor in the liquid binder phase solubility depends on the chemical stability of the carbide, which has low chemical stability in the binder phase exhibits a high saturation concentration. And the inhibitor effects depend on the solubility of the binder phase itself. Generally, the lower chemical stability of grain inhibitors higher solubility in the binder phase, the inhibitory effect is more obvious. In addition, the eutectic temperature of inhibitor and Co Inhibitor thinning effect is also the main factors of the inhibitor refinement, the lower Co eutectic temperature, the higher solubility in the adhesive phase, the effect of suppressing is better.












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The tungstic oxide (WO3) constituent of the particulated mixture is introduced in the form of a finely-particulated tungsten containing mineral concentrate which preferably comprises predominately tungstic oxide. In accordance with conventional practices, tungstic oxide containing feed materials are commercially available as concentrates derived from various ore beneficiation processes to reduce the gangue and other contaminating constituents to concentrates usually containing at least 60%, and preferably at least 70%, tungstic oxide. Such beneficiation processes usually employ crushing, grinding, magnetic or gravity separation, flotation, or special chemical reactions to produce a particulated tungstic oxide concentrate. Common mineral sources containing tungsten oxide compounds which are suitable for producing concentrates for use in accordance with the practice of the present process include wolframite [(FeMn)WO4 ]; ferberite [FeWO4 ], which is the iron member of the wolframite family and contains some manganese; huebnerite [MnWO4 ], which is the manganese member of the wolframite family and contains some iron; and scheelite [CaWO4 ], which comprises essentially calcium tungstate.
 

The average particle size of the tungsten mineral concentrates for forming the mixture may range from about 10 microns to about 250 microns, while average particle sizes of from about 50 microns to about 125 microns are particularly satisfactory. Usually, beneficiation processes commercially employed effect a grinding or pulverizing of the mineral during the concentration process to an average particle size within the required range and no further supplemental grinding is required. However, in those instances in which the mineral concentrate is of an average particle size generally greater than about 250 microns, the concentrate is first subjected to a grinding operation to reduce its average particle size within the desired range.

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Description of the preferred embodiments

The composition and concentration of the various feed materials, products, by-products and intermediate by-products, are described in the specification and subjoined claims in terms of percentages by weight unless clearly indicated to the contrary.

Sintered, dense pellets or briquettes of a ferrotungsten alloy of the desired composition are produced in accordance with the present process by forming a substantially uniform mixture of a finely-particulated tungsten ore concentrate, a carbonaceous reducing agent and some supplemental iron-bearing material, if necessary, to adjust the iron content within the desired concentration range. The mixture is agglomerated and thereafter heated at an elevated temperature in an environment devoid of oxygen and in a substantial vacuum in a manner to effect a direct reduction of the tungstic oxide constituent to form metallic tungsten and an alloying thereof with the iron constituent present to produce the ferrotungsten alloy.



 

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Summary of the invention

The benefits and advantages of the process comprising the present invention are achieved by forming a substantially uniform mixture composed of controlled amounts of a finely-particulated tungsten ore concentrate derived from minerals, such as wolframite, scheelite, ferberite and/or huebnerite; a supplemental quantity of a finely-particulated iron-bearing material present in an amount to adjust the iron content of the mixture to provide the desired iron concentration in the resultant ferrotungsten alloy produced, and a carbonaceous reducing agent such as carbon present in an amount slightly in excess of the stoichiometric quantity required to reduce the tungstic oxide and any iron oxide compounds present in the mixture to the metallic state. The resultant uniform mixture is agglomerated into a plurality of shape-retaining pellets, which thereafter are heated to an elevated temperature ranging from about 2500° F. to about 3100° F. under a vacuum of less than about 0.5 Torr (500 microns) for a period of time sufficient to effect a reduction of substantially all of the tungsten oxide compounds and any iron oxides present to the metallic state and to effect an alloying of the reduced metallic tungsten and iron to form a ferrotungsten alloy. The vacuum smelting of the pelletized feed material further effects a volatilization of the contaminating constituents in the pelletized feed material, which are continuously withdrawn together with the gaseous reaction products of the oxidized carbonaceous reducing agent. The gaseous effluent can be treated to effect an extraction and recovery of certain valuable volatilized constituents therein, such as manganese, for example, and the balance of the gaseous effluent after appropriate treatment can be harmlessly discharged to the atmosphere. The resultant ferrotungsten alloy in the form of relatively dense sintered pellets are cooled to a temperature of about 300° F. or below, and thereafter are extracted from the vacuum smelting furnace.

Additional advantages and benefits of the present invention will become apparent upon a reading of the description of the preferred embodiments taken in conjunction with the specific examples provided.

 

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Background of the invention

The process as described in the aforementioned U.S. Pat. No. 3,966,459, is directed to a vacuum dissociation of a pelletized molybdenite concentrated feed material at an elevated temperature, producing pellets of relatively pure metallic molybdenum and the process as described in the aforementioned copending continuation-in-part application is directed to the further embodiment of producing ferromolybdenum alloys containing controlled amounts of iron and molybdenum by the vacuum smelting of a pelletized mixture comprised of a molybdenite concentrate and an iron-bearing material at an elevated temperature, producing ferromolybdenum alloy pellets which are eminently suitable for use as an alloying addition agent in steel-making operations and the like. The present continuation-in-part application is directed to still another embodiment of producing ferrotungsten alloys containing controlled amounts of iron and tungsten, which also are suitable for use as an alloying addition agent in iron and steelmaking operations.

Ferrotungsten alloys are produced in accordance with prior art practices by either employing a thermite process or an electric furnace reduction process. Both of these techniques require substantial amounts of labor and energy and are, therefore, somewhat costly. In the thermite process, for example, a tungstic oxide feed material derived from a chemical pretreatment of a tungsten ore concentrate is mixed with reducing agents, such as silicon and/or aluminum, which through an exothermic thermite-type reaction, produces an ingot or button of the ferro-alloy. The ferro-alloy button usually is of a segregated structure and further requires crushing and sizing prior to shipment and use. The slag produced, for economic reasons, is usually subjected to further treatment for recovery of residual metal values and the treated residue is discarded. In addition to the relatively high costs of the reducing agents required in the thermite process, further problems are presented from an environmental standpoint as a result of the disposal of the slag produced and the treatment required of the gases evolved during the exothermic reaction.

The present process overcomes many of the problems and disadvantages associated with prior art techniques for producing ferrotungsten alloys by utilizing a tungsten ore concentrate directly as the starting material without requiring costly chemical pretreatments to extract the tungstic oxide. Carbon is employed as a low-cost reducing agent, eliminating the formation of any slag, whereby a ferrotungsten alloy is obtained which is of a nonsegregated structure and is in the form of pellets, avoiding the necessity of subjecting the ferro-alloy to a crushing operation as in the case of buttons produced by the thermite process.

 

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Tungsten carbide step drill bits are used to drill metal up to 1/4 of an inch thick. Step drill bits are designed to enlarge a hole as the bit drills through the sheet metal. Each step on the bit is larger in diameter than the step before. Smaller step drill bits are self-starting and no pilot bit is required to start the hole. On larger step drill bits, you need to have a hole pre-drilled that is equal in diameter to the smallest step on the bit.

-Put on appropriate eye protection (safety glasses or goggles).

-Place the tip of the center punch on the metal to be drilled at the location of the desired hole. Hit the blunt end of the center punch with the hammer to leave an indentation (referred to as a center mark). This indentation will provide a place for the drill bit to "catch" so it doesn't drift to the wrong location on the work.

-Secure the self-starting step tungsten drill bit into the chuck of the drill motor. Apply cutting and tapping fluid to the center mark and the step drill drill bit.

-Align the tip of the self-starting step drill bit with the center mark on the metal's surface. Depress the drill's trigger to start drilling the hole. Run the small step drill bit completely through the metal. Apply additional cutting and tapping fluid as necessary to keep the step drill bit cool.

-Release the chuck of the drill motor to remove the small step drill bit. Secure the large step drill bit into the chuck of the drill motor. Insert the small tip of the large step drill bit into the hole you created in the metal. Apply cutting and tapping fluid onto the large tungsten carbide step drill bit and around the hole in the metal.

-Depress the trigger of the drill motor to run the large-diameter step drill bit into the hole. Stop drilling frequently to apply additional cutting and tapping fluid to the drill bit. Stop drilling when the hole has reached the desired diameter.

-Remove the large step drill bit from the drill motor. Clean both step drill bits with a rag to remove metal shavings from the bits. Clean the metal shavings from around the hole that you drilled in the metal. Store the drill bits in a tool box or drill bit container to avoid dropping them or otherwise damaging them.

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Tungsten carbide HT drills bits are specially created for drilling tile, marble, porcelain, ceramics, etc.

Usually HT drill bits have the following dimension types:

DIAMETER   TOTAL LENGTH

1/8″                    3″

5/32″                  4″

3/16″                  4″

1/4″                    4″

5/16″                4-3/4″

3/8″                  4-3/4″

1/2″                    6″

And the below application characteristics:

-Titanium Tungsten TSM carbide. 110° tip angle

-Straight flute entry

-1,120° Low-Stress high temperature brazing.

-Asymmetric spiral flute.

-Highest quality steel.

-Surface hardened

-Use in Rotary mode only!

-Tile: 1200-600 RPM

-Glass: 800-400 RPM (Small diameters use higher rpm, Large diameters use lower RPM)

-Apply high contact pressure if necessary.

-Allow for 20 seconds cooling time between holes for longer bit life

-For use in all materials up to scratch hardness of 9.

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Carbide tipped hard steel die drills have heavy duty hardened tool steel bodies to provide shock resilient support for the thick, long carbide tip. They have straight flutes and straight shank. The drill body diameter is smaller than tool diameter.

Die drills may be run at speeds from 75 to 100 SFPM. Apply light feed (.001-.003 I.P.R.) with steady pressure.

Carbide tipped die bits are recommended for those occasions when you need to remove a broken bolt, a broken easy out or threaded fastener.

Carbide tipped die bits:

118° point  – negative edge (for steels in the range of 50 Rc to 65 Rc)

118° point – positive edge (for cast iron, high temperature alloys and steels up to 50 Rc)

140° Point  – negative edge (for steels in the range of 50 Rc to 65 Rc)

140° point – positive edge (for cast iron, high temperature alloys and steels up to 50 Rc)

The above can be used for coring out pre-existing holes.

Carbide tipped die bits are recommended for those occasions when you need to remove a broken bolt, a broken easy out, or threaded fastener. The left hand cutting action assists with backing the object out of the hole, by it’s counter clockwise spin.

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Tungsten is an important alloying element in high-speed and other tool steels, and is used to a lesser extent in some stainless and structural steels. Tungsten is often added to steel melts as ferrotungsten, which can contain up to 80% tungsten. World ferrotungsten production is dominated by China, which in 2008 exported 4,835 t (gross weight) of the alloy. Ferrotungsten is relatively expensive, with the prices around $31–44 per kilogram of contained tungsten.

A process for producing ferrotungsten alloys by forming a uniform mixture comprised of a finely-particulated tungsten-containing mineral, such as wolframite, scheelite, ferberite, and/or huebnerite; a supplemental quantity of a particulated iron-bearing material and a controlled amount of a carbonaceous reducing agent which is agglomerated into a plurality of pellets which are heated to an elevated temperature under a controlled vacuum for a period of time sufficient to effect a reduction of the tungstic oxide constituent to the metallic state and volatilization and extraction of the volatile constituents in the pellets, and an alloying of the metallic tungsten with the iron constituent, producing substantially dense sintered ferrotungsten alloy pellets.


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However, the last method belongs to a theoretical ideal and the operation is also complicated. The specific processes is that after the coated powder of WO2.90 (WO3) through thermal decomposition reduction, the inhibitor can be distributed more uniformly on the surface of the particles W, and then carbonized, add Co triturated wet mixing meanwhile. Furthermore, the adding amount of grain growth inhibitor is generally based on liquid binder phase inhibitor concentration, and the finest microstructure can be obtained simultaneously. And the use of inhibitors usually reduces the toughness of cemented carbide nozzles, so the control of the adding amount is very significant.











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