SE537464C2 - Iron and tungsten-containing briquettes - Google Patents

Abstract

SUMMARY The invention relates to jam- and tungsten-containing briquettes and a process for producing the briquettes. A briquette is prepared by mixing a jam powder and a tungsten-containing powder, as well as briquetting the mixture.

Description

TECHNICAL FIELD The present invention relates to a process for producing jam- and tungsten-containing briquettes. The invention also relates to briquettes produced by the process.

BACKGROUND WO101053231 discloses a method of making a jam- and tungsten-containing powder or powder agglomerate. A powder containing tungsten carbide is mixed with a jam oxide powder and / or a powder containing tungsten oxide and optionally a jam powder. The mixture is heated in a neutral or slightly reduced atmosphere.

WO2008091210 describes a jam- and tungsten-containing powder containing 30-60% by weight of W and the remainder jam. The powder is prepared by mixing a jam powder with a WO 3 powder. A ball can be made of the powder.

OBJECTS OF THE INVENTION It is an object of the invention to provide a new jam- and tungsten-containing material which is suitable for tungsten additive in the smelting industry, for example the steel, foundry and superalloy industry, and a process for producing such material on a comparatively cost-effective salt.

DESCRIPTION OF THE INVENTION At least one of the above objects is achieved at least to some extent by a process for producing jam- and tungsten-containing briquettes comprising the steps of: producing a mixture comprising (in weight percent): 1-jam powder containing at least 80% metallic jam, 2- Tungsten-containing powder containing tungsten oxides and / or tungsten carbides, optionally 1-carbon powder, 2-90 molybdenum-containing powders added to the mixture: a liquid, preferably water, optionally one or more of: binder, 1 slag former, desulfurizing agent, c) briquetting to produce a plurality Through this process, it is possible to produce jam- and tungsten-containing apricots.

The non-reduced briquettes can be used as a substitute for conventionally produced jam-tungsten and / or jam-molybdenum alloys, in alloying the melt in industrial production. The briquettes can be manufactured at lower costs than standard quality iron alloys. Their porous structure facilitates rapid dissolution in a steel malt.

The briquettes can be easily transported on a conveyor belt without risk of rolling.

When preparing the mixture, the total quantity of water added is about 110% by weight of the mixture, most preferably 2-5% by weight.

Preferably, neither binder nor slag former is used. When the ferrous powder is mixed in an aqueous state, it strengthens the briquettes, which makes the use of binder unnecessary. Thus, the quantity of impurities can be reduced.

Optionally, the method comprises the step of: a) drying the briquettes.

By drying the apricots, the risk of cracking is minimized due to rapid evaporation of the liquid when they are heated at high temperatures.

Preferably, the optional drying step comprises at least one of the following: drying the briquettes to a moisture content below 5% by weight, preferably below 3% by weight, drying the briquettes at a temperature in the range of 50-250 ° C, preferably 80-200 ° C, more preferably 100- 150 ° C.

When drying the briquettes, a temperature increase occurs even when no external heat is used. This is thought to be due to reactions when the iron oxidizes. The bark strength of the briquettes also increases. It makes it possible to provide sufficiently strong briquettes without the need to add binders, i.e. the jam powder replaces the need for binder. Dust problems are also minimized. 2 Many different types of industrial dryers can be used. The briquettes can also be dried without active heating, for example at ambient temperature. In a dryer, the steam can be removed with a gas steam or with a vacuum. For improved process economy, the drying time in a dryer is preferably in the range of 10-120 minutes, more preferably 20-60 minutes. But longer drying times are of course conceivable.

The moisture content is defined as the quantity of water present in the briquettes in addition to crystal water. The moisture content can be determined by an analysis of the type LOD (Loss On Drying, loss on drying) in accordance with ASTM D2216-10.

The dry matter composition refers to the composition of a dried specimen, i.e. excluding any moisture present in the briquettes.

Preferably, the method comprises the step of: b) reducing the briquettes to produce a plurality of reduced briquettes.

Preferably, the reduction moment comprises at least one of the following: reduction at a temperature in the range 800-1 500 ° C, preferably 1,050-1400 ° C, more preferably 1 100-1 300 ° C, most preferably 1 150-1 250 ° C, reduction for at least 20 minutes, more preferably at least 30 minutes, reduction in an oven fed with an inert or reducing gas, preferably fed with a weakly reducing gas, reduction at a working pressure in the range 0.1-5 atm, preferably 0.8 -2 atm, more preferred 1.05-1.2 atm.

By monitoring the formation of CO / CO2, it can be determined when the reduction process is completed. The reduction time can be optimized by feeding the formation of CO and CO2, in particular CO because CO2 is formed mainly during the first minutes of the reduction after which the CO formation dominates until the carbon dioxide is consumed or all reducible oxides have been reduced. Preferably the reduction time is at most hours, preferably at most 2 hours, more preferably at most 1 hour. Depending on the reduction time, the reduction temperature and the ratio between carbon and reducible oxides in the briquettes, the reducible oxides of the briquettes can be partially or completely reduced.

The atmosphere inside the furnace is preferably controlled by feeding an inert or a reducing gas, preferably a weakly reducing gas, into one spirit of the furnace, and evacuating gases (for example reaction gases (for example CO, CO2, and H 2 O) and the feed gas) in the opposite spirit, more preferably in that the inert or reducing gas is fed countercurrently at an outlet side of the furnace, and that gases are evacuated at an inlet side of the furnace. This means that the inert or reducing gas is preferably fed countercurrently. The inert gas or a reducing gas may be, for example, argon, N2, H2 or any mixture of H2 / N2 (for example in a ratio of 5:95 by volume).

The reduction furnace is preferably a feed furnace but the alien may be a batch furnace. In a feed-through oven, the briquettes are transported from an inlet to an outlet during the reduction. Examples of kilns are, for example, rotary kilns, rotary kilns, shaft kilns, roasting kilns, mobile roasting kilns, tunnel kilns or batch kilns. Other types of furnaces used in the direct reduction of solid state metal oxides can also be used. In a preferred embodiment, an oven with a conveyor belt is used.

Preferably, the reduction furnace operates at a pressure in the range of 0.1-5 atm, preferably 0.8-2 atm, more preferably at a pressure in the range of 1.0-1.5 atm, most preferably 1.051.2 atm.

The atmosphere inside the furnace is preferably controlled by feeding an inert or a reducing gas, preferably a weakly reducing gas, into one spirit of the furnace and gases (for example reaction gases (for example CO, CO2, and H 2 O) and the feed gas) are evacuated in the opposite spirit, more preferably by feeding the inert or reducing gas in countercurrent at the outlet side of the furnace, and evacuating gases at the inlet side of the furnace. This means that the inert or reducing gas is preferably fed countercurrently. The inert gas or a reducing gas may be, for example, argon, N2, H2 or any mixture of H2 / N2 (for example in a ratio of 5:95 by volume).

Preferably, the method further comprises the step of: c) cooling the reduced briquettes in a non-oxidizing atmosphere (eg reducing or inert) to a temperature below 200 ° C, more preferably below 150 ° C, preferably in an inert atmosphere.

The atmosphere during cooling can be, for example, argon, N2, H2 or any mixture of H2 / N2 (for example in the ratio 5:95 with respect to volume). Other atmospheres 4 can also be used. If it is undesirable to have very low levels of nitrogen in the briquettes, the briquettes can be cooled in a nitrogen-free atmosphere such as an argon gas atmosphere.

In one embodiment, briquetting is performed at a briquetting pressure in the range of 80-1000 kg / cm2, preferably 100-500 kg / cm2.

In one embodiment, briquetting is performed at a briquetting pressure in the range of 1,00010,000 kg / cm 2, preferably 2,000-5,000 kg / cm 2.

Preferably, the briquetting machine is a roller press. However, other types of briquetting machines can be used.

The briquettes may be heat-treated at a lower temperature before reduction. Preferably, the briquettes are heat-treated at a temperature in the range of 200-800 ° C, more preferably 400-700 ° C. Preferably, the possible heat treatment takes place at a lower temperature from 10 minutes to less than 2 hours, preferably less than 1 hour. By heat treatment at lower temperatures, any lubricant (if any) can be burned off in a controlled manner. In addition, molybdenum trioxide (if present) can be reduced to molybdenum dioxide. This can be used as a pre-reduction step before the reduction described in the preceding paragraph or in the production of partially reduced briquettes. The possible heat treatment at 200-800 ° C can be carried out in the same oven as the reduction. The possible heat treatment and the possible drying can also be combined.

Optionally, lubricants and / or binders and / or slag formers and / or desulfurizing agents may be added during mixing. The possible binders can be organic or inorganic binders. The binders may, for example, be a carbonaceous binder which partially replaces the carbonaceous powder. Other binders may be, for example, bentonite and / or dextrin and / or sodium silicate and / or lime. The possible slag former may be limestone, dolomite and / or olivine. The total quantity of lubricant and / or binder and / or slag-forming agent and / or desulfurizing agent may be 0.1-10% by weight of the dry matter content of the bricks, more preferably less than 5% by weight. It can be in the range 1-10% by weight. The binders are optional because the briquettes are added strong enough by adding the water and iron to be reduced in the reduction furnace without severe cracking. If lubricants are added, 0.1-2 per cent of the briquette dry matter content is preferably supplied in quantities, for example about 0.5-1% by weight. The lubricant may, for example, be zinc stearate. However, other lubricants used in powder metallurgy may be added.

Depending on the purity of the powder, the mixture of the briquettes may contain additional components including oxides which are responsible for reducing. The quantity of Adana components is mainly determined by the purity of the tungsten-containing powder and any molybdenum-containing powder, but can also come from contaminants in the iron powder, carbon powder and from reactions with components in the ambient atmosphere during heating, reduction or cooling. heat. To reduce the amount of external heat required, oxygen or tuft can be provided in a preheating zone to react with the carbon monoxide formed to form carbon dioxide gas. If air is used, the nitrogen uptake of the briquettes may increase. With the help of oxygen, nitrogen uptake during the heating and reduction operation can be minimized.

Instead of the briquettes being dried before being fed into the reduction furnace, the furnace may have a drying zone operating at a temperature in the range of 80-200 ° C, preferably 100-1 ° C. The reduction furnace may also comprise a pre-reduction zone, downstream of the drying zone if Adan is used, and operate in the range 200-800 ° C, preferably 400-700 ° C.

The yam and tungsten-containing fabrics have a dry matter composition, in weight percent, of: a) 90-100 of a mixture comprising, in weight percent of the mixture: 2-97 tungsten-containing powder containing tungsten oxides and / or tungsten carbides, optionally 0,1-carbon powder, 2- 90 molybdenum-containing powder, and the remainder 1-yam powder-containing powder, b) optionally <lubricant and / or binder and / or slag-forming agent and / or a desulfurizing agent.

Preferably the reduced jam and tungsten-containing briquettes consist of, in weight percent: W20-80 6 Mo20-80 Mo + W50-97 <<Si <Co <Other substances <and the rest Fe 2-40.

The briquettes can replace conventionally manufactured iron alloys, in the case of alloying with tungsten and possibly tungsten / molybdenum in smelting processes. The briquettes can be manufactured at lower costs than standard quality jam-tungsten. The briquettes dissolve faster than standard-quality iron — tungsten. Depending on the reduction time, the relative quantity of carbon in relation to the quantity of reducible oxides and the reduction temperature, the oxygen content of the briquettes can be reduced partially or completely. The briquettes can be easily transported on a conveyor belt without the risk of rolling.

By briquetting for reduction, it is possible to produce a briquette which has a higher porosity than a briquette formed from reduced powders. In addition, it is possible to produce a briquette that is free of binders and lubricants.

Mixture The mixture provided in step a) comprises (in% by weight): 2-97 tungsten-containing powder, optionally 0.1-carbon powder, 2-90 molybdenum-containing powder, the remainder 1-iron powder.

Preferably the jam powder is 2% by weight, more preferably 3-15% by weight.

Preferably, the tungsten-containing powder is at least 20% by weight. Preferably, the tungsten-containing powder + the molybdenum-containing powder constitutes more than a percentage by weight of the mixture, more preferably more than 70% by weight of the mixture.

In one embodiment, the mixture consists of (in weight percent): 1-40, preferably 3-15, of eft yam powder, and 75-99, preferably 85-97, of a tungsten-containing powder.

Preferably, the tungsten-containing powder contains tungsten oxides and tungsten carbides. Preferably the reducible oxides in the tungsten-containing powder and the jam powder are stoichiometrically adapted to the carbon in the tungsten carbides, so that the carbon content after a reduction is less than 10% by weight, preferably less than 5% by weight, more preferably less than 1% by weight, most preferably less than 0.5 weight percent; and the oxygen is less than a percentage by weight, preferably less than 5% by weight, most preferably less than 3% by weight.

Thereby, jam- and tungsten-containing briquettes can be produced, which essentially consist of jam and tungsten as well as unavoidable contaminants.

Jam- and tungsten-containing briquettes consisting of jam and tungsten as well as unavoidable impurities can also be produced from a mixture in which tungsten carbides are partially or completely replaced by a carbon powder, i.e. so that the carbon in tungsten carbides and / or carbon powders stoichiometrically corresponds to the reducible oxides in the tungsten-containing powder and the jam powder.

Jam- and tungsten-containing briquettes consisting of jam, tungsten and molybdenum as well as unavoidable impurities can be prepared from the mixture by adding any molybdenum-containing powder. Has the carbon from the tungsten carbides and / or the carbon powder been adapted stoichiometrically to the reducible oxides in the molybdenum-containing powder, the tungsten-containing powder and the jam powder. Preferably, the tungsten-containing powder is a tungsten carbide powder comprising at least 70% by weight of WC, preferably at least 95% by weight of WC, or a tungsten oxide powder comprising at least 70% by weight of WO 3, preferably at least 95% by weight of WO 3, or a mixture of these powders.

Preferably the carbon and oxygen are balanced so that the carbon content after reduction is less than a percentage by weight, preferably less than 5% by weight, more preferably less than 1% by weight, most preferably less than 0.5% by weight; and the oxygen is less than 8% by weight, preferably less than 5% by weight, most preferably less than 3% by weight.

The relative quantities of molybdenum and tungsten can be varied by changing the relative quantities of the tungsten-containing powder and the molybdenum-containing powder, while taking into account the carbon and oxygen balance.

In a preferred embodiment, the weight ratio of tungsten carbide to tungsten oxide (WC / WO 3) is in the range 0.5-5, preferably 1-4, more preferably 1.5-3. An optimal balance is about 2. As a result, the tungsten carbide can correspond to the tungsten oxide without the need for the addition of carbon powder.

In one embodiment, the weight ratio of molybdenum to tungsten (Mo / W) is determined to be in the range 0.25-4, preferably 0.5-2, more preferably 0.8-1.25.

Tungsten-containing powder The tungsten-containing powder is preferably any of: a tungsten-carbide-containing powder, a tungsten-oxide-containing powder, a mixture of tungsten-carbide-containing powder and tungsten-oxide-containing powder.

Tungsten carbide-containing powder The tungsten carbide-containing powder is a pithier comprising tungsten carbides enclosed in a metal matrix. Preferably, the tungsten carbide-containing powder is obtained from carbide scrap with tungsten. The tungsten carbide-containing powder preferably comprises 1-10% by weight of carbon, the remainder tungsten and unintentional impurities. The tungsten carbide-containing powder may also comprise alloy components which have formed a matrix (binding material) for the cemented carbide material with tungsten. The proportion of carbide phase is generally 70-97% of the total weight of the composite. The carbon enters the powder particles in the form of tungsten carbide grain, and the grain size is usually on average between 0.10 μm and 15 μm. Each powder particle may contain several tungsten carbide grains, especially if the particles are large. Furthermore, the tungsten carbide-containing powder may contain powder particles which are free of tungsten carbide grains; however, most of the powder particles will contain one or more grains of tungsten carbide. Some tungsten carbide powders may contain cobalt up to 15% by weight, usually around 110% by weight Co. For example, the tool material in circuit board drills usually contains fine hard metals with tungsten formed in a cobalt matrix, the quantity of which represents 6 percent of the total weight of the tool material, while coarse-grained carbides with tungsten are usually used for the tool material for mining drills, where the cobalt content is about 10% by weight. These powders can be used if cobalt can be allowed or desired in the briquette to be produced. Otherwise, these powders can be used after leaching on cobalt. For example, a commercially available tungsten carbide-containing powder from scrap containing 1-10% by weight of Co, usually in quantities of 3-8% by weight of Co, can be leached hydrometallurgically to reduce the cobalt content to less than 1% by weight of Co, preferably less than 0.5% by weight of Co, more The preference is less than 0.2% by weight of Co. Cobalt from the leaching process can be recovered and used as a commercial product in itself.

Of course, a tungsten carbide powder which is already low in content or free of cobalt can be used.

It is a powder which contains less than 1% by weight of Co, more preferably less than 0.5% by weight of Co, more preferably less than 0.2% by weight of Co.

Preferably the tungsten carbide powder contains at least 90% by weight of WC, more preferably at least 95% by weight.

Preferably at least 90% by weight, more preferably at least 99% by weight, of the particles in the tungsten carbide-containing powder pass through a test screen in accordance with ISO 3310-1: 2000 with a nominal neck size of 250 μm, more preferably 125 μm, most preferably 90 μm. Very fine powder where at least 99% by weight passes through a 45 μm test sieve can be suitably used.

Tungsten oxide-containing powder The tungsten oxide-containing powder may be a jam- and tungsten oxide-containing powder, more preferably jam-tungstate in the form of the mineral ferberite. Preferably a ferberite containing more than 60% WO 3, more preferably at least 70% WO 3. The ferberite is crushed and / or ground and / or crumbled into a powder so that at least 80% by weight of the particles, preferably at least 90%, pass through a test sieve in accordance with ISO 3310-1: 2000 with a nominal neck size of 250 μm, more preferably 125 um. The tungsten oxide-containing powder may be a pure tungsten oxide powder containing less than 5% by weight of other substances in addition to W and 0, preferably less than 1% by weight of other substances. For example, a powder containing at least 95% by weight of WO 3, preferably at least 99% by weight.

Preferably, at least 80% by weight, more preferably at least 90% by weight, of the particles in the tungsten oxide powder pass through a test screen in accordance with ISO 3310-1: 2000 with a nominal neck size of 2, preferably 125 μm, most preferably 90 μm. Very fine powder ddr at least 99% by weight passes through a 45 tm test sieve can suitably be used.

The tungsten oxide-containing powder may also be a mixture of jam tungstate and pure tungsten oxide powder.

Other available grades of tungsten oxide powder can also be used.

Molybdenum-containing powder The molybdenum-containing powder is preferably a molybdenum oxide powder. The powder preferably consists of molybdenum dioxide and / or molybdenum trioxide powder.

The molybdenum oxide powder should contain 50-80% by weight of Mo, with other components being oxygen and impurities. Preferably the impurities are less than 10% by weight, more preferably less than 5% by weight, most preferably less than 1% by weight.

Preferably at least 90% by weight, more preferably at least 99% by weight, of the particles in the molybdenum oxide powder pass through a test screen in accordance with ISO 3310-1: 2000 with a nominal neck size of 250 μm, more preferably 125 μm, most preferably 45 μm. Jam powder The jam powder is preferably a jam powder containing at least 80% by weight of metallic jam, preferably at least 90% by weight of metallic jam, more preferably at least 95% by weight of metallic jam, most preferably at least 99% by weight of metallic jam. The jam powder may be after jam mushroom powder and / or a water atomized jam powder and / or a gas atomized iron powder and / or an iron filter dust and / or after iron lamp powder. For example, filter dust X-RFS40 from flogands AB, Sweden is a suitable powder. The yolk powder can be partially or completely replaced by an iron oxide powder, for example but not limited to: powder consisting of one or more flan groups FeO, Fe 2 O 3, Fe 3 O 4, FeO (OH), (Fe 2 O 3 * H 2 O). The iron oxide powder can, for example, be crisp. Preferably the ferrous powder contains at least 50% by weight of metallic jam, more preferably at least 80% by weight of metallic Fe, most preferably at least 90% by weight of metallic Fe.

Preferably at least 90% by weight, more preferably at least 99% by weight, of the particles in the ferrous powder pass through a test screen in accordance with ISO 3310-1: 2000 with a nominal neck size of 125 gm, more preferably 90 gm. Very fine powder where at least 99% by weight passes through a 45 μm test sieve can ideally be used.

Possibly charcoal powder The briquettes preferably contain a charcoal doll. In the preferred embodiment, the carbon part is a tungsten carbide-containing powder, the carbon content of which is stoichiometrically corresponding to the oxide content of the briquettes. However, a carbon powder can be used as either in combination with a tungsten carbide-containing powder or as the sole. The carbon powder is preferably selected from the group of: subbituminosa carbons, bituminosa carbons, lignite, anthracite, coke, petroleum coke and biochar such as carbonaceous resources. The carbon powder can be, for example, soot, carbon black, activated carbon. The carbon powder can awn be a mixture of different carbon powders.

For the choice of carbon powder, consideration is preferably given to the reactivity of the carbon. Preferably, kimrok is used. German lignite, lignite, bituminosa and subbituminosa carbons also have comparatively high reactivity.

Preferably, at least 90% by weight, more preferably at least 99% by weight, of the particles in the carbon powder pass through a test screen in accordance with ISO 3310-1: 2000 with a nominal neck size of 125 μm, more preferably 45 μm, most preferably 20 μm. The quantity of the carbon part (i.e. WC powder and / or carbon powder) is preferably determined by analyzing the quantity of reducible oxides in the tungsten-containing powder, the jam-powder and the optional molybdenum-containing powder. Preferably, the quantities of the carbon dioxide are selected so that they stoichiometrically correspond to or in flakes exceed the quantity of reducible oxides in the tungsten-containing powder, the iron powder and the possible molybdenum-containing powder. However, the quantity of carbon dioxide can also be understochiometric.

The quantity of carbon dioxide can be optimized by feeding the carbon levels and oxygen levels in the reduced briquettes - and by increasing or decreasing the quantity of carbon dioxide to achieve desired levels of carbon and oxygen. Oxides that are acidic to reduce with carbon such as Si, Ca, Al, and Mg can be allowed up to certain levels depending on which applications the briquettes are to be used in. For example, in many applications in steel metallurgy, these oxides can be handled by e.g. deposited in the steel malt slag. If smaller quantities of these oxides and substances are desired, purer grades of the tungsten-containing powder, the jam powder and any molybdenum-containing powder may be used, for example grades containing less or no quantities of these oxides.

Jam- and tungsten-containing Mbriquettes The briquettes consist of the mixture provided in step a). When preparing the mixture, the total amount of added water is about 1-10% by weight of the mixture, most preferably 2-5% by weight. The briquettes can be dried to reduce the moisture content to less than 5% by weight, or less than 3% by weight.

The briquettes may optionally contain up to 10% by weight of one or more organic or inorganic binders and / or slag formers and / or desulfurizing agents and / or lubricants. In one embodiment, the briquettes are free of lubricants, binders, slag formers and desulfurizing agents.

The ravioli is surprisingly strong and it may be possible to use the dried ravioli to directly alloy a steel malt with tungsten, and possibly tungsten and molybdenum, i.e. without prior reduction of the bricks. The briquettes can be a cost-effective way to alloy with tungsten, and possibly tungsten and molybdenum. The briquettes can also be partially or completely reduced by heating the briquettes in subsequent steps.

Jam- and tungsten-containing briquettes 0, C can be ingested from 0.05 and higher. Si, Co can range from savings up to the given quantities. Preferably they are not added intentionally but can not as contaminants. Other substances in addition to W, Mo, Fe, 0, C, Si, Co can contain flang quantities up to the given quantities. Preferably they are not added intentionally but can be ingested as contaminants.

With the proposed process, jam- and tungsten-containing briquettes can be prepared which consist of, in weight percent: 20-80, preferably 30-65, more preferably 40-55, 13 Mo 20-80, preferably 30-65, more preferably 40-55 , Mo + W> 50, preferably> <10, preferably <70, 5, more preferably <3, <10, preferably <5, more preferably <1, Si <10, preferably <5, more preferably <1, Co < 10, preferably <5, more preferably <1, Second subject <5, preferably <1, and the residue Fe 2-40, preferably 3-25, more preferably 5-20, most preferably 5-15.

Preferably, the weight ratio of molybdenum to tungsten (MoIW) is determined to be in the range 0.25-4, preferably 0.5-2, more preferably 0.8-1.25.

These briquettes have a geometric density in the range 1-6 g / cm 3, preferably 2-5 g / cm 3.

These jam-, tungsten- and molybdenum-containing briquettes are suitable for alloying with tungsten and molybdenum in smelting processes. The briquettes containing iron, tungsten and molybdenum can be produced at comparatively lower costs. In addition, due to their porous structures, the briquettes dissolve quickly in a steel malt.

The quantity of other substances is mainly controlled by the purity of the tungsten-containing powder and any molybdenum-containing powder. The purity of the ferrous powder and any carbon powder can of course affect the quantity of other substances.

The nitrogen content depends mainly on the nitrogen levels in the atmosphere during heating, reduction and cooling of the briquettes. By regulating the atmosphere in these moments, the nitrogen content can be made lower by 0.5% by weight, preferably lower by 0.1% by weight and most preferably lower by 0.05% by weight. 14

Claims (9)

l. a) A process for producing iron and tungsten containing briquettes the processincluding the steps of: providing a niixture con1prising (in weight-%): 2-97 tungsten containing powder containing at least one oftungsten oxides and tungsten carbides. optionally 0. 1-25 carbon powder, 2-90 nio lybdenuni containing powder, balance 1-40 iron powder. b) adding to the niixture: a liquid, preferably water, optionally one or n1ore of: C) lubricant,binder,slag forrner, desulfurizer; briquetting to provide a plurality of green briquettes. 2. A process according to claini l wherein the niixture fulfilling the condition: > 50 n1olybdenun1 containing powder + tungsten containing powder. 3. A process according to claini l and 2 wherein the process further includes drying the green briquettes at a temperature less than 200 °C, preferably less than l50 °C, until the nioisture content is less than l0 % by weight of the briquettes, preferably less than 5 % by weight. 4. A process according to any one of claims 1- 3 wherein the process furtherincludes reducing the green briquettes at a temperature in the range of 800-1500°C, preferably 1050-1400 °C, more preferably 1100-1300 °C, most preferab1yll50-1250 °C. 5. A process according to claim 4, wherein the method includes one or more of thefollowing steps:d) cooling the reduced briquettes in a non-oxidising atmosphere to atemperature below 200 °C , more preferably below 150 °C, preferably in an inert atmosphere; 6. Iron and tungsten containing green briquettes having a dry matter composition inweight-% of:a) 90-100 of a mixture comprising in weight % of the mixture:2-97 tungsten containing powder containing at least one of tungsten oxides and tungsten carbides, optionally 0.1-25 carbon powder, 2-90 molybdenum containing powderbalance

1. -40 iron powder containing powder; b) optionally up to 10 of a binder and/or slag former and/or a desulfurizer. 7. Iron and tungsten containing briquettes consisting of in weight %: W 20-80 Mo 20-80Mo+ W 50-97O S 10C S 10Si S 10 Co S 10 Other elements S 5 and balance Fe

2. -40. . Iron and tungsten briquettes according to claim 7 consisting of in Weight %: O S 5, more preferably S 3, C S 5, more preferably S 1, Si S 5, more preferably S 1, Co S 5, more preferably S 1, Other elements S 5, preferably S 1, and balance Fe 2-40, preferably

3. -25, more preferably 5-20, most preferably 5-15. . Iron and tungsten containing briquettes according to claim 7 consisting of in Weight %: W 30-65, preferably 40-55, Mo 30-65, preferably 40-55, Mo + W >70, O S 10, preferably S 5, more preferably S 3,C S10, preferably S 5, more preferably S 1,Si S 10, preferably S 5, more preferably S 1,Co S 10, preferably S 5, more preferably S 1, Other elements S 5, preferably S 1,and balance Fe 2-40, preferably 3-25, more preferably 5-20, most preferably 5-15.