Some standard content:
UDC669.27+669.28:001.4
National Standard of the People's Republic of China
GB4198-—84
Downgraded to SJ/T10744-96
Special technical terms in production of tungsten and molybdenum wires1984-03-09Published
National Bureau of Standards
TTTKKAca
Implementation on 1984-11-01
National Standard of the People's Republic of China
Special technical terms in production of tungsten and molybdenum wiresThis standard specifies the definitions of terms in the production and performance testing of tungsten and molybdenum wires. 1Wolframite
wolframite
UDC669.27+669
.28:001.4
GB4198-84
The chemical name is wolframite, represented by (Fe, Mn) WO. It is a series of isomorphous mixtures of iron tungstate and manganese tungstate. The components at the two ends of this series are wolframite (FeWO) and wolframite (MnWO,). Usually, the mineral with a ratio of FeWO:MnWO.80:20 is called wolframite; and the mineral with a ratio of FeWO,:MnWO,<20:80 is called wolframite; the mineral with this value between the two is called wolframite. Its mineral crystal is monoclinic, difficult to dissolve in acid, black, brown or reddish brown, and the reddish brown color is significant when the manganese content increases. 2Scheelite
scheelite
The chemical name is calcium tungstate. It is represented by CaWO. It is white, yellow (brass), gray, green or brown. Its mineral crystals are tetragonal and often contain isomorphous impurities, such as calcium molybdate (CaMoO,). Scheelite dissolves in acid and alkali. 3Molybdenite
molybdenite
The ore is mainly molybdenite, whose molecular formula is MoS2, hexagonal crystal system, density 4.7~4.8g/cm2, appearance like graphite, very soft. The grade of molybdenite in the ore is very low, generally only 0.1%~0.8%, but the content of molybdenite concentrate, MoS, made after beneficiation can be increased to 80%~95%.
4Concentrate and tailings
Concentrate and tailings
The original ore is beneficiated to obtain concentrate and tailings. The part with a high content of effective ingredients that meets a certain specified standard is called concentrate. The content of WO in tungsten concentrate is generally greater than 60%. The part III with very low effective component content and reaching the level of waste is called tailings. Under certain conditions, a third mineral may be obtained, whose effective component content is between the two, and this ore is used as a medium ore. It still needs to be processed again to obtain qualified secondary concentrates and tailings. Scheelite concentrate and black tungsten concentrate are the main raw materials for the production of ammonium paratungstate and tungsten trioxide. Molybdenum concentrate is the main raw material for the production of molybdenum trioxide and ammonium paramolybdate. 5 Soda roasting process
soda roasting process
Before wet smelting, the black tungsten concentrate is mixed with soda and roasted in a rotary kiln at high temperature. This method is called soda roasting, which is one of the methods for industrial processing of black tungsten concentrate. The purpose is to remove impurities such as P, S, Si, As and organic matter, and at the same time increase the reaction activity of the concentrate, promote the complete oxidation of Fe and Mn, and improve the leaching rate of tungsten. The main reactions are as follows: Issued by the National Bureau of Standards on March 9, 1984
TTYkAoNrKAca
Implementation on November 1, 1984
6 Alkali decomposition method
GB4198—84
+-O2=2Na2WO.+Fe2Og+2C02
2FeWO,+2Na,CO3+
+=02=3Na,WO,+MngO,+3CO2
3MnWO.+3Na,CO,+
caustic leaching process
The method of selectively dissolving tungsten from tungsten ore with an aqueous solution of a certain chemical reagent is called leaching, or leaching. It is a chemical processing process that transfers tungsten from solid ore to solution. The reagent used for leaching is called leaching agent. Alkaline leaching agent is used to leach tungsten ore, so that tungsten is transferred from solid ore to liquid phase in the form of sodium tungstate solution. This leaching process is called alkaline decomposition method. Wolframite is difficult to dissolve in acid, so alkaline decomposition method is used. The ground wolframite concentrate is added to the concentrated sodium hydroxide solution. NaOH should be excessive to produce the following reaction:
FeWO,+2NaOH=Na,WO,+Fe(OH)2
MnWO.+2NaOH=NazWO,+Mn(OH)2
The ferrous hydroxide and manganous hydroxide generated by the above reaction are oxidized by oxygen in the solution to generate Fe(OH)2 and MnO2·HO and remain in the insoluble residue.
7. Autoclave- soda process
In order to increase the leaching speed and leaching rate of tungsten, a process of alkaline decomposition under high temperature and high pressure is adopted. This processing method is called autoclave. This method refers to the decomposition of calcium tungstate ore (or wolframite) with soda or sodium hydroxide solution in an autoclave. The autoclave generally uses a high-pressure scoop, and the pressure inside the scoop can reach 15atm and the temperature can reach 200℃. The reaction equation is as follows: CaWO (week) + Na,CO (liquid) = NazWO. + CaCO (solid) The autoclave is also suitable for adding low-grade intermediates and tailings containing WO, 4% to 5%. 8 Acid leaching process
acid leaching process
Use acid (generally hydrochloric acid) as a leaching agent to treat solid tungsten ore, and separate tungsten in the form of insoluble tungstic acid and soluble calcium salt. This process is called acid decomposition. Add finely ground scheelite concentrate to hot hydrochloric acid to produce the following reaction: CaWO (week) + 2HCI (liquid) = H,WO, (solid) + CaCl2 (liquid). The leached CaCl2 and impurities such as P, As, and F in the scheelite concentrate are dissolved in hydrochloric acid, while H,WO, is insoluble. Crude tungstate slurry is obtained by filtration.
9Leakage rate
leaching rate
The percentage of tungsten dissolved in the leaching solution to the total tungsten in the ore before leaching is called the leaching rate. It can be calculated by the leaching solution calculation method or the leaching residue calculation method (taking the alkaline method as an example). Tungsten concentration in leachate × leachate volume liquid meter leaching rate =
slag meter leaching rate = (1
tungsten grade in ore × ore dosage
tungsten grade in slag × slag weight
tungsten grade in ore × ore dosage
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—×100%
10tungstic acid
GB4198--84
tungsten acid
Molecular formula: H,WO4, is an amorphous yellow powder, density 5.5g/cm3, insoluble in water and acid solution. It dissolves in strong alkaline solution and ammonia solution to form tungstate. Tungstic acid is usually prepared by the reaction of hydrochloric acid and calcium tungstate: CaWO,+2HCI=H,WO,+CaCl2
If cold hydrochloric acid is used, hydrated tungstic acid, H,WO,·H,O, is obtained, which is a white colloid, more stable in water than H,WO,. If hot hydrochloric acid is used, a colloidal precipitate of yellow tungstic acid (WO,·nH,O) is obtained. 11Isopoly tungstic acid and isopoly tungstate
isopoly tungstic acid and isopoly tungstateIsopoly tungstic acid can be regarded as an acid formed by the shrinkage of two or more simple oxygen-containing acid molecules of the same kind, also known as polyacid (the corresponding salts are called polyacids and isopolyacids). Its general composition formula is yWO3·aH,O (y>x). The structure of this type of tungsten compounds is relatively complex. In order to express clearly, they are often expressed by molecular formulas instead of their names. When the simple oxygen-containing acid ions of tungsten are acidified, various isopoly acid ions are generated successively, and their complexity increases with the increase of acidity. The reaction is reversible, but some steps are very slow, so it takes a long time to reach half equilibrium. For example, when the sodium tungstate (NazWO) solution is gradually acidified, a white colloidal precipitate, white tungstic acid or hydrated tungsten trioxide, is first precipitated. With a slight shake, the precipitate is redissolved to form tungstate. If acid is continued to be added, the precipitated hydrated tungsten trioxide will no longer be redissolved. The condensation reaction of orthotungstate ion is summarized as follows: HW.O%
paratungstate
(A) ion
12Heteropoly acid of tungsten
pseudochromic acid
root ion
WO2HO or wO.·3H,0
hydrated tungsten trioxide (tungstic acid)
paracalcic acid
(B) ion
H2Wi20f
metatungstate ion
heteropolytungstic acid
Tungstate solution is mixed with salt solution as the central atom (impurity atom), and tungsten heteropoly acid is generated by heating or acidification. For example, tungstate solution is mixed with salt solution of Si, P, As, B to generate heteropolyacid of tungsten: SiO1-+12WO2-+28H+=H[SiW12OJ+12H,0There are about 30 elements that can be used as the central atom (impurity atom) to form heteropolyacid. 3
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13Tungstate
tungstate
GB4198—84
Tungstic acid is dissolved in caustic soda, soda and ammonia solution to generate tungstate. Different pH values of the solution will produce various tungstates with different ratios of tungsten trioxide and monovalent metal oxide: orthotungstate
paratungstate
metatungstate
tungsten bronze
14 ammonia solution
M2O.WO..nH,O
5M,O.12WO,·nH,O
3M,0.7WOg·nH,0
4M,0.10WO，·nH,O
3M,0.8WO3 ·nH,0
M20.4WO, ·nH,0
MwO,(0<81)
degstion of the tungstic acid in aqueous ammoniaTungstic (molybdenum) acid produced by industrial methods has a high impurity content (generally 0.2%~3.0%). Impurities have a serious impact on the production of dense metals. In order to remove these impurities, the properties of tungstic (molybdenum) acid that is easily dissolved in ammonium hydroxide, while impurities such as Si, Fe, Mn, Ca, etc. simultaneously generate insoluble residues, are used to achieve the purpose of purification through precipitation and filtration. This process is called ammonia dissolution. The solution temperature and ammonia concentration during ammonia dissolution are the main factors controlling the dissolution process, dissolved products and product quality. 15 Evaporation and crystallization
evaporation of the ammonium tungstate solution The ammonium tungstate solution is evaporated in an evaporator to precipitate ammonium paratungstate crystals. This process is called evaporation and crystallization. The reaction equation is: 12(NH)zWO=5(NH)2O.12WO，.5H,0+14NH，+2H,O During the crystallization process, some impurities, especially molybdenum, are removed. The temperature of evaporation and crystallization is an important factor in controlling the crystal system of the product, and the crystallization time is also a noteworthy factor in controlling the quality of ammonium paratungstate.
16 Neutralization process
Neutralization of ammonium tungstate solution with hydrochloric acid to precipitate ammonium paratungstate crystals. This process is called neutralization process. The neutralization process can precipitate needle-shaped ammonium paratungstate crystals containing 11 molecules of crystal water from the cold solution. The reaction equation is: 12(NH)2WO+14HC1+4H,O=5(NH)2O12WO,11H,O+14NH,CIThe operation of adding HCI to neutralize the ammonium tungstate solution should be carried out slowly and carefully under the condition of continuous stirring to avoid the production of metatungstate due to local excess of hydrochloric acid. The neutralization reaction is carried out until pH=7.3. 17 Mother solution
mother solution
After the ammonium tungstate solution is evaporated or neutralized to precipitate ammonium paratungstate crystals, the remaining solution is called mother liquor. The mother liquor contains a large amount of soluble impurities, especially aluminum. Controlling the specific gravity of the mother liquor is an important means to ensure product quality. 4
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.18Ammonium paratungstate
GB4198-84
ammoniumparatungstate(APT)
Ammonium in the ammonium tungstate solution is volatilized continuously to precipitate ammonium paratungstate crystals with low solubility. Its decomposition formula is: 5(NH)2O12WO3nHzO, where n may be 11.7 and 5.
Tungstic acid and ammonia solution interact to form ammonium tungstate. Concentrating the ammonium orthotungstate solution or neutralizing the ammonium orthotungstate solution with acid can obtain ammonium paratungstate crystals. The reaction formula is as follows:
H,WO,+2NH,OH=NH)2WO,+2H,O
12(NH,)2WO,+14HC1=5(NH)2O.12WO,nH,O+14NH,CI+(7-n)H,0藤发
12(NH)2WO4
→5(NH,)2.12WO3·nH,O+14NHst+(7-n)H20When the ammonium tungstate solution evaporates and crystallizes, if the crystallization temperature is lower than 50℃, orthorhombic ammonium paratungstate crystals containing 11 crystal waters are obtained; at 50~70℃, monoclinic ammonium paratungstate crystals containing 7 crystal waters are obtained, and at 70~100℃, monoclinic hexagonal crystals containing 5 crystal waters are obtained. By using the acid neutralization method, ammonium paratungstate of different crystal systems (containing different crystal waters) can also be obtained according to different acidities. In the powder metallurgy of tungsten, ammonium paratungstate containing 5 crystal waters is the most commonly used. Ammonium paratungstate containing 88.8% WO3 is heated in hydrogen, and turns blue at about 350℃, turns reddish purple at about 400℃, turns brown at about 500~600℃, and turns gray at about 600~900℃. Ammonium paratungstate is completely decomposed into tungsten trioxide when heated to above 600℃ in air. 19Ammonium paramolybdate
ammonium paramolybdate
Dissolve MoO: in concentrated ammonia solution, heat and concentrate to precipitate ammonium paramolybdate 3(NH,)20·7MoO3·4H,O:7Mo03+6NH,OH+H,0—>3(NH,)20:7Mo034H,0Heating and decomposing ammonium paramolybdate is an important way to obtain high-purity MoO,. 20Ammonium metatungstate
ammonium metatungstate
Heat ammonium paratungstate at 205～215℃ for a long time (24～40 hours) and then dissolve it in water, and make the solution crystallize: or adjust the pH value of the orthotungstate solution to 4 to make it crystallize, and ammonium metatungstate can be obtained, and its molecular formula is (NH,)2O.4WO3·8HzO. Its crystal grains are coarse and metallic, and are tetragonal octahedral. It loses crystal water at 100℃, starts to lose ammonia at 120℃, and aggregates into glassy colloidal tungstate with the composition of (NH.)2W. O1g·4H,O or 6H,O at 250℃. 21 Tungsten Bronze
tungsten bronze
In the past, people used to call tungsten oxide with a crystal structure similar to bronze tungsten bronze. Modern research shows that tungsten bronze does not refer to a specific phase structure, but a general term for ternary metal oxides of tungsten with the following properties. a. Luster and color, and the color range refers to various colors from yellow to black. b. It has metallic conductivity or semiconductor properties. c. The main lattice is stable.
d. Resistant to chemical corrosion by non-oxidizing acids. Tungsten oxides can generate tungsten bronze with alkali metals, alkaline earth metals, rare earth elements, copper, silver, lead, ammonia, and needles.
The density of tungsten bronze is 6.5~7.5g/cm3, and its chemical properties are relatively stable. It is insoluble in water, but soluble in alkali. Tungsten bronze can be made by the following methods:
a. Reducing acidic tungstate with hydrogen, coal gas, zinc or iron at a relatively high temperature, 5
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GB4198-84
b. Electrolytically reducing the molten tungstate,
Electrolytically reducing the molten mixture of tungstic acid and metal carbonate; c.
d, in the absence of air, tungstate or acid tungstate and tungsten dioxide melt together. 22 Yellow tungsten oxide
yellow tungsten oxide
Roasting tungstic acid or ammonium paratungstate can produce yellow oxide, commonly known as tungsten trioxide (WO,), also called tungsten anhydride. WO: There are three variants: α-WO, (stable from room temperature to 720℃), B-WO3 (stable from 720~1100℃), y-WO (stable above 1100℃). Tungsten trioxide is a yellow powdery substance, which turns orange-yellow when heated. The depth of its color depends on the roasting temperature and the coarseness of the powder. The density of tungsten trioxide is 7.2~7.4g/cm3, the melting point is 1430℃, it sublimates significantly at 850℃ in air, and the boiling point is between 1700~2000℃. Tungsten trioxide is insoluble in water or acid, but dissolves in alkali metal hydroxide and sodium carbonate solution to form stable tungstate. Yellow tungsten oxide is one of the important raw materials for tungsten powder metallurgy. 23 Blue tungsten oxide
blue tungsten oxide
A series of non-stoichiometric intermediate compounds are obtained by reducing tungsten trioxide with hydrogen at 350-480°C. The color is blue and they are collectively called blue tungsten oxide, for example: WO2.g (W20O), WO2.72 (W18O4g). The important characteristics of blue tungsten oxide are large specific surface area, many cracks on the particles, high surface activity, easy to react with dopants, easy to reduce, and easy to control the powder particle size. 23.1 β-tungsten oxide
β-WO (2.83
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