FR2889843A1 - PROCESS FOR THE PREPARATION OF CALCIUM SALTS - Google Patents

Abstract

The present invention relates to a process for the preparation of calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate and mixtures thereof, characterized in that it comprises the following steps: ) used catalysts comprising a metal or a combination of metals selected from molybdenum, vanadium, tungsten and mixtures thereof; b) the used catalysts combined in a) are roasted at a temperature ranging from 400 to 1100 degree; C, in excess of air, to obtain grilled catalysts and dusts, - c) leaching of the grilled catalysts and / or dusts obtained in b) with a basic solution, - d) on purifies the aqueous leaching solution obtained in c) and comprising the elements included in the group consisting of molybdenum, tungsten, vanadium and mixtures thereof, e) is carried out in the purified aqueous leaching solution; e) obtained in d), a precipitation of the calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate and mixtures thereof with calcium compounds.The invention also relates to the use of calcium salts selected from calcium molybdate (CaMomicronO4), calcium vanadate (CaV2O6), calcium tungstate (CaWO4) and mixtures thereof, obtained by such a process for making alloy steels.

Description

2889843 1

  The present invention relates to a process for the preparation of calcium salts, in particular calcium molybdate (CaMoO4), calcium tungstate (CaWO4) and calcium vanadate (CaV2O6), alone or as a mixture, from used catalysts from, among others, the petroleum industry (hydrotreatment, hydrodesulfurization and hydrocracking).

  In the iron and steel industry, it is sought to manufacture alloy steels, that is to say steels comprising one or more metals which provide the steel with particular desired properties, such as, for example, resistance to temperature, resistance corrosion, or high mechanical strength, etc ... for applications in different industries, such as automotive, aerospace, cutting tools or machining, or transport.

  Among the metals used in the manufacture of alloy steels, stainless steel, refractory, special or fast, we find molybdenum, tungsten or vanadium. In this case, commonly used as a source of molybdenum, tungsten or vanadium, ferroalloys, such as FeMo, FeV, FeW or oxide briquettes, for example MoO3, V2O5 and WO3. The ferroalloys or oxides mentioned above are expensive and constitute an important part of the cost of production of stainless steel or fast steel mentioned above.

  On the other hand, the use of ferroalloys or oxide briquettes is not entirely satisfactory because it requires the supply of CaO, usually made by adding quicklime. However, it turns out that the hygroscopic nature of the lime can generate defects, such as pits, blowholes or gas bubbles, which are the cause of scrap metal finished products.

  Thus, it would be advantageous to have pure products based on molybdenum, tungsten or vanadium, alone or as a mixture, which can be used in the manufacture of alloy steels, which in particular would be less expensive than the ferroalloys or briquettes of oxides and which would remedy the quality problems of the steels mentioned above.

  On the other hand, molybdenum, tungsten and vanadium are themselves expensive metals. These metals are for example used in the composition of catalysts, in particular catalysts used in the petroleum industry, for example for hydrotreating, hydrodesulfurization and hydrocracking operations.

  It is important, for economic and environmental reasons, to recover the precious metals of molybdenum, tungsten and vanadium when these catalysts are used.

  The Applicant has discovered a particular process for producing calcium salts, in particular calcium molybdate, calcium tungstate and calcium vanadate, which are particularly pure, alone or as a mixture, from used catalysts comprising molybdenum tungsten and / or vanadium.

  These calcium salts can then advantageously be used in the production of ferroalloys or as enrichment material in molybdenum, tungsten and / or vanadium in the manufacture of ferrous or non-ferrous alloys, in particular in substitution for FeMo ferroalloys. , FeV and FeW or oxide briquettes of MoO3, V2O5 and WO3.

  An object of the invention is a process for the preparation of calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate and mixtures thereof, characterized in that it comprises the following steps: a) used catalysts comprising a metal or a combination of metals chosen from molybdenum, vanadium, tungsten and mixtures thereof; b) the used catalysts combined in a) are roasted at a temperature of 400; at 1100 ° C., in excess of air, to obtain grilled catalysts and dusts, c) the toasted catalysts and / or dusts obtained in b) are leached with a basic solution; d) purifying the aqueous leaching solution obtained in c) and comprising the elements included in the group consisting of molybdenum, tungsten, vanadium and their mixtures, - e) is carried out in the aqueous leaching solution p in d), a precipitation of the calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate and mixtures thereof with calcium compounds.

  The process according to the invention makes it possible both to recover precious metals in a directly usable form and to produce either pure or combined ferroalloys or enrichment materials made of these metals which are particularly easy to use in the steel industry and in foundry. Furthermore, the calcium salts produced according to the process of the invention can be used in the manufacture of alloy steels without the addition of quicklime: such a use has the advantage of limiting the risks of pitting, blow-molding and gas bubbles. often observed when using quicklime.

  Finally, the process according to the invention makes it possible to produce calcium salts at a reduced economic cost and to limit damage to the environment by allowing the recycling of valuable raw materials such as molybdenum, tungsten and vanadium contained in end of life products.

  By virtue of a specific succession of pyrometallurgical and hydrometallurgical steps chosen, the process according to the invention makes it possible to recycle used catalysts in a simple, fast and inexpensive manner and to produce either ferroalloys or enrichment molybdenum, tungsten and / or vanadium directly usable in the iron and steel industry and in foundries.

  In a first step of the process according to the invention, starting materials are combined in the form of used catalysts comprising a metal or a combination of metals, generally supported by the catalyst, chosen from molybdenum, vanadium, tungsten and their mixtures. These catalysts are generally used in the chemical, gas treatment or petroleum industry, in particular in the cracking and refining processes, for example to desulphurize the distillation products. The metal or combination of metals may be selected from Ni-Mo, Co-Mo, Ni-Co-Mo, Ni-Mo-V, Bi-Co-Mo, Ni-W, V-W.

  The support of these used catalysts is generally chosen from alumina, silica, titanium oxide and mixtures thereof.

  Generally, the metal or combination of metals is present in the minor catalyst, preferably at a content ranging from 5 to 30%, more preferably from 15 to 30% by weight, based on the weight of the used catalyst.

  Preferably, the support is present in the used catalyst at a content ranging from 65 to 90%, more preferably from 70 to 85%, by weight, relative to the weight of the used catalyst.

  These catalysts may also include sulfur. The sulfur may be present in the spent catalyst at a level of from 3 to 25%, more preferably from 8 to 12%, by weight, based on the weight of the catalyst.

  These spent catalysts also generally include hydrocarbons and carbon from the distillation products that these catalysts have been used to desulphurize or gas treatment for example during the cracking of nitrogen oxides to limit emissions of greenhouse gases.

  These spent catalysts thus comprise mainly, in whole or in part, oxidized or sulfur compounds of molybdenum (Mo), nickel (Ni), cobalt (Co), tungsten (W), vanadium (V), bismuth (Bi), aluminum (Al), titanium (Ti) and silicon (Si), sulfur (S), carbon (C), hydrocarbons (HC) and residual metals of the arsenic type (As ), phosphorus (P).

  In a second step of the process according to the invention, these used catalysts are roasted at a temperature ranging from 400 to 1100 C, in excess of air, to obtain grilled catalysts and dust.

  Preferably, the used catalysts are selectively grilled and by campaign in a controlled and oxidizing atmosphere. Such a grid makes it possible to extract used catalysts sulfur (S), carbon (C), hydrocarbons (HC) and arsenic (As).

  In one embodiment of the process of the invention, used catalysts are grid at a temperature ranging from 700 to 800 C. This limits the formation of alumina-metal oxide spinels, which then allows better leaching during the stage. subsequent process.

  In the roasting step, the metal or combination of metals included in the group consisting of molybdenum, tungsten, vanadium and mixtures thereof, is partially sublimed. For example, molybdenum is sublimated during its oxidation as MoO3. Preferably, this MoO3 is recovered at the first stage of a bag filter. The oxidized compounds of the elements Al, As, P, V and W accompany the dust. Thus, these MoO3-rich dusts also include Al2O3, P2O5 and As2O3.

  The deep roasting makes it possible to sublimate up to 70% of the quantity of metal or of the combination of metals included in the group consisting of molybdenum, tungsten, vanadium and their mixtures, initially present in the spent catalyst: the content of metal or combination of metals included in the group consisting of molybdenum, tungsten, vanadium and their mixtures, in used catalysts is greatly reduced.

  After roasting, the carbon content (C) in spent catalysts is preferably less than or equal to 5% by weight, based on the weight of used catalysts.

  After roasting, the sulfur content (S) in the used catalysts is preferably less than or equal to 3% by weight, relative to the weight of used catalysts.

  After roasting, the content of metal or combination of metals included in the group consisting of molybdenum, tungsten, vanadium and their mixtures, in used catalysts is preferably less than or equal to 6% by weight, relative to the weight of used catalysts.

  In one embodiment of the method according to the invention, the gaseous effluents from the roasting can pass into an afterburner after leaving the roasting furnace and can be burned at more than 850 C in excess of air. After dedusting, these gaseous effluents are treated with basic salts so as to neutralize and capture in the form of a stable compound SO2 sulfur dioxide generated by roasting. The basic salts employed are calcium hydroxide Ca (OH) 2 or preferentially sodium bicarbonate as for example described in application EP 1 550 495.

  In a third step of the process according to the invention, leaching of the grilled catalysts and / or dust obtained in b) is carried out using a basic solution.

  The leaching may be carried out with sodium hydroxide NaOH, ammonia NH3 or sodium carbonate Na2CO3 in aqueous solution.

  Leaching with sodium hydroxide involves the following reactions: MoO3 + 2 NaOH> Na2MoO4 + H2O V2O5 + 2 NaOH> 2 NaVO3 + H2O Al2O3 + 2 NaOH> 2 NaAIO2 + H2O Sodium carbonate leaching involves the following reactions: MoO3 + Na2CO3 -> Na2MoO4 + CO2 WO3 + Na2CO3 Na2WO4 + CO2 V2O5 + Na2CO3 - 2 NaVO3 + CO2 Al2O3 + Na2CO3> 2 NaAlO2 + CO2 During this leaching step, particular care must be taken in minimizing the dissolution of the alumina. Indeed, the alumina is necessary later for the purification of the leaching solution and must not be dissolved in large quantities during this leaching step.

  Preferably, the used catalysts are leached with sodium hydroxide NaOH or sodium carbonate Na2CO3. Indeed, although ammonia is less aggressive than sodium hydroxide or sodium carbonate towards alumina, it dissolves the elements Co, Ni, Mo and V. However, it is important for the subsequent step to obtain a leach solution free of Co and Ni.

  Preferably, the leaching of used catalysts is carried out with a mixture of sodium hydroxide (NaOH) and sodium carbonate Na 2 CO 3, doped with hydrogen peroxide (H 2 O 2).

  The leaching parameters (pH, redox potential, residence time, flow rates, concentrations, liquid / solid ratio, etc., etc.) are adapted according to the catalyst so as to avoid excessive dissolution of the alumina.

  Preferably, the sodium hydroxide is present in excess of 20% relative to the stoichiometry of the leaching reaction for each oxide MoO3, WO3, V2O5. Such an excess of sodium hydroxide makes it possible to limit the dissolution of alumina.

  The leaching step can generally last from 30 to 120 minutes. The leaching is generally carried out at a moderate temperature ranging from 50 to 100.degree. C., preferably ranging from 70 to 90.degree. C., preferably continuously and countercurrently in a series of at least 2 tanks, for example from 3 to 12 or more bins, percolation.

  It has been observed in one example that in the case of sodium hydroxide, the extraction yield of molybdenum and tungsten, depending on the type of catalyst, is 75 to 85%: that of vanadium is between 65 and 80%.

  The leach solution obtained at the end of this step comprises the elements included in the group consisting of molybdenum, tungsten, vanadium and their mixtures as well as impurities such as P, As, Al and optionally Ni and Co. However, preferably, the Ni and Co possibly present in the used starting catalysts are not dissolved and remain on the supports of said catalysts.

  In a fourth step of the process according to the invention, the aqueous leaching solution obtained in c) and comprising the elements included in the group consisting of molybdenum, tungsten, vanadium and their mixtures is purified.

  Preferably, the leach solution is purified by neutral pH treatment. This makes it possible to eliminate by precipitation the elements P, As, Al, and the traces of Ni and Co quasi-completely. The traces of Fe and Si can also be eliminated with very high yields.

  After this purification, the respective content of each of the elements As, Al, P, Ni, Co, Fe and Si in the leaching solution is preferably less than 2 mg / l.

  The mineral acids H 3 PO 4, HNO 3, HCl and, preferably, H 2 SO 4 can be used for this precipitation by acid neutralization.

  Preferably, the treatment at neutral pH or neutralization of the purification step is at about 90 ° C. Such a temperature makes it possible to improve the precipitation of P, As, Fe and Si and simultaneously limits the possible and undesired precipitation of the molybdenum and / or vanadium.

  It has been observed that the initial Al content of the leaching solution has a significant effect on the purification and the precipitation yield of As, Mo, V, P, Ni and Co. In fact, the following behavior is observed (cf. Table 1): Precipitation yield (% by weight) Ni Co As P Mo V Al = 0.2 100 100 0 0 0 0 g / I Al = 0.5 100 100 48 56 1 1 g / l Al = 1 g / I 100 100 77 84 2 5 Al = 2 g / l 100 100 100 100 5 14 AI = 3 g / 1 100 100 100 100 7 22 Table 1: Precipitation yield of elements Ni, Co, As, P, Mo and V according to the Al content of the leaching solution The sedimentation of the precipitates formed is favored by the addition of flocculants in the presence of air bubbling.

  After the purification has been carried out, in a fifth step of the process according to the invention, precipitation is carried out of the calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate and mixtures thereof. by calcium compounds.

  In one embodiment of the invention, the purified leach solution is precipitated by addition of calcium chloride (CaCl 2) or lime milk to obtain calcium salts of the metals of the group consisting of molybdenum, vanadium, tungsten and their mixtures.

  In one embodiment of the invention, nonselective precipitation of vanadium and molybdenum is achieved; the purified leach solution is then, for example, acidified to a pH ranging from 2 to 3 by addition of hydrochloric acid HCl or nitric acid HNO 3 or by addition of CaCl 2. The reactions involved are as follows: Na 2 MoO 4 + 2 HCl> 2 NaCl + MoO 3 .H 2 O and NaVO 3 + HCl - NaCl + HVO 3 Na 2 MoO 4 + 2 HNO 3> NaNO 3 + MoO 3 .H 2 O and NaVO 3 + HNO 3 - NaNO 3 + HVO 3 Na 2 MoO 4 + CaCl 2 2 NaCl + CaMoO4 and 2NaVO3 + CaCl2 2NaCl + CaV2O6 In another embodiment of the process according to the invention, a selective precipitation of vanadium then of molybdenum is carried out; the leaching solution is then, for example, first neutralized to a pH of between 7 and 8 by addition of ammonium chloride NH4Cl. The vanadium is precipitated in the form of sodium metavanadate NH4VO3 according to the reaction: NaVO3 + NH4Cl -> NH4VO3 + NaCl A solid / liquid separation, using a filter press for example, makes it possible to expell the solution of the crystals of sodium metavanadate which are dried before conditioning.

  The sodium molybdate present in the solution thus clarified is then precipitated by addition of calcium chloride CaCl 2 according to the reaction: Na 2 MoO 4 + CaCl 2 -> 2 NaCl + CaMoO 4 In another embodiment of the process according to the invention, milk lime can also be used.

  Finally, a solid / liquid separation, using a filter press for example, makes it possible to expell the solution of the calcium molybdate crystals with or without the calcium vanadates and calcium tungstates in a mixture. These crystals can be dried or calcined before conditioning.

  In one embodiment of the process according to the invention, so as to produce a calcium molybdate free of sulfur and phosphorus, harmful impurities in metallurgical applications, the precipitation of molybdenum can be increased up to 80% molybdenum precipitate. The solution is filtered and precipitated again with production of a calcium molybdate, with or without the calcium vanadates and calcium tungstates in mixture, and containing sulfur in particular.

  The calcium molybdate (CaMoO4) obtained can be either sold as the lixiviation process is overhauled.

  In one embodiment of the process of the invention, drying and / or calcination of the salts obtained in the fifth step, namely calcium molybdate (CaMoO4), calcium tungstate (CaWO4) calcium vanadate (CaV2O6) and / or mixtures thereof.

  The process according to the invention makes it possible to recover precious metals in a directly usable form to produce pure or combined ferroalloys or to produce enrichment materials made of these precious metals that are particularly simple to use in the iron and steel industry and in foundries. Furthermore, the calcium salts produced according to the process of the invention are particularly pure and can be used in the manufacture of alloy steels without addition of quicklime: such a use has the advantage of limiting the risks of pitting, blistering and gas bubbles that are usually observed when using quicklime.

  The present invention also relates to the use of calcium salts selected from calcium molybdate (CaMoO4), calcium vanadate (CaV2O6), calcium tungstate (CaWO4) and mixtures thereof, obtained according to the process above , to make alloy steels.

  The present invention will now be illustrated using the following example:

EXAMPLE:

  In a first step, used catalysts are available from the hydrotreating of petroleum fractions, having the following composition: Element Content (wt%) Al 36.5 Mo 9.7 V 1.5 Ni 0.3 Co 3, 2 W 0.1 Si 0.5 Fe 0.2 As 0.01 P 0.3 Na 0.2 Table 2: Chemical composition of used catalyst of hydrotreatment of petroleum fractions (renormalization of the contents after removal of carbon and sulfur) Toasting: In a second step, these catalysts are roasted in excess of air at a temperature ranging from 700 to 800. Grilled spent catalysts and dusts rich in molybdenum oxides, tungsten and / or vanadium are recovered.

  Leaching: In a third step, the used grilled catalysts obtained in the preceding step are leached with sodium hydroxide.

  200 g of grilled catalysts obtained in the preceding step are leached with 150 ml of concentrated sodium hydroxide solution at 60 g / l for 3 hours at 90 ° C. Table 3 presents the results obtained.

  Residue Solution Mass or volume 174 g 280 ml pH - 10.9 Mo content 1.6% 39, 6 g / I V content 0.6% 4.3 g / I Al content 40.7% 5.2 g / I Free NaOH content 13.6 g / l Table 3: Hydroprocessing catalyst leaching results for sodium hydroxide The leaching yields of Mo, V and Al are respectively 86%, 65% and 3%.

  Purification by precipitation in an acidic medium: In a fourth step, the leaching solution obtained in the preceding step is purified by treating this solution at neutral pH. Precipitation is carried out at 90 ° C.

  A volume of 14 ml of sulfuric acid H 2 SO 4 concentrated to 100 g / l is added to 100 ml of leaching solution of pH 11.8. After adding H2SO4, the pH is increased from 11.8 to 7. The volume of the purified solution is 114 ml and the pH is 6.6. A precipitate is collected: its mass is 2 g.

  Table 4 shows the results obtained during the purification.

  Content g / I mg / I Mo V Al As Solution of 31.4 3.4 4.1 27.3 leaching Purified solution <25.3 2.1 0.8 Table 4: Results of the purification of the solution of 10 leaching of hydroprocessing catalyst with sodium hydroxide The precipitation yields of Mo, V, Al and As are respectively 8%, 28%,> 98% and 97%.

  Precipitation of V and Mo: case of selective precipitation In a fifth step, selective precipitation of vanadium and molybdenum is carried out.

  The selective precipitation of Mo and V contained in the purified leaching solution is carried out on 100 ml of purified solution at 90 ° C. with addition of 38 ml of aqueous solution of ammonium chloride NH4Cl concentrated to 100 g / l.

  The precipitation yields of molybdenum and vanadium are respectively 1.5% and greater than 95%. The solution is filtered and clarified.

  Then, the solution thus clarified and freed from vanadium is mixed with 14 ml of aqueous solution of CaCl 2 concentrated to 100 g / l.

  The precipitation yield of the molybdenum is greater than 95%. The solution is filtered and clarified.

  The moisture content of the filtered calcium molybdate in filter press is 40 to 45%. The Mo content of calcium molybdate, on a dry basis, is between 35 and 45%. Calcium molybdate is powdery after drying. A calcination step between 500 and 700 C or granulation makes it possible to obtain respectively sintered blocks (diameter less than 100 mm) or granules (diameter less than 50 mm).

  The calcination makes it possible to bring the molybdenum content, on a dry basis, between 40 and 46% Mo.

  The typical chemical composition of calcium molybdate at the filter press outlet, on a dry basis, is presented in Table 5.

  Element Content (wt%) Mo 35 - 45 Ca 20 25 V <500 ppm W <500 ppm P <200 ppm As <200 ppm Ni Traces Co Traces Si Traces Fe Traces Table 5: Chemical composition of calcium molybdate produced from hydrotreating catalysts Production of ferroalloys from calcium molybdate, calcium vanadate, calcium tungstate, pure or in mixture: Molybdates, tungstates, pure or mixed calcium vanadates produced from spent refining catalysts Petroleum cuts can be used in the production of ferroalloys of the FeMo, FeV, FeW, FeMoV, FeVW or FeMoW type, for example, or in the enrichment of ferrous or non-ferrous alloys.

  The vanadate, tungstate and calcium molybdate are advantageously charged as a material for substitution of the technical oxides MoO3, WO3 or V2O5 or ferroalloys FeMo, FeV and FeW associated.

  Ferroalloys 2889843 For example, to produce one tonne of FeMo containing 70% Mo, 1488 kg of CaMoO4 are used with a yield of 98%. This equates to 1071 kg of MoO3 technical oxide and 417 kg CaO equivalent to 435 kg of lime.

  Enrichment: For example, to produce one tonne of tool steel typically containing 5% Mo, 6% W and 1.5% V, 106 kg CaMoO4, 96 kg CaWO4 and 36 kg CaV2O6 are used.

Claims (13)

  A process for the preparation of calcium salts included in the group consisting of calcium molybdate (CaMoO4), calcium vanadate (CaV2O6), calcium tungstate (CaWO4) and mixtures thereof, characterized in that it comprises the the following steps: a) used catalysts comprising a metal or a combination of metals selected from molybdenum, vanadium, tungsten and mixtures thereof; b) the used catalysts combined in a) are roasted at a temperature ranging from from 400 to 1100 C, in excess of air, to obtain grilled catalysts and dust, - c) leaching of the grilled catalysts and / or dusts obtained in b) with a basic solution, d) purifying the aqueous leaching solution obtained in c) and comprising the elements comprised of the group consisting of molybdenum, tungsten, vanadium and mixtures thereof; e) producing in the purified aqueous leaching solution; e obtained in d), a precipitation of calcium salts included in the group consisting of calcium molybdate, calcium vanadate, calcium tungstate, and mixtures thereof, with calcium compounds.   2. Method according to claim 1, characterized in that, in step b), the used catalysts are grid at a temperature ranging from 700 to 800 C.   3. Method according to claim 1 or 2, characterized in that, in step c), leaching is carried out spent catalysts with a mixture of sodium hydroxide (NaOH) and sodium carbonate Na2CO3, doped with water oxygenated (H2O2).   4. Method according to the preceding claim, characterized in that the sodium hydroxide is present in excess of 20% relative to the stoichiometry of the leaching reaction for each oxide MoO3, WO3, V2O5.   5. Method according to any one of the preceding claims, characterized in that, in step c), the leaching is carried out at a moderate temperature ranging from 50 to 100 C, preferably ranging from 70 to 90 C.   6. Method according to any one of the preceding claims, characterized in that, in step d), the leaching solution is purified by treatment at neutral pH.   7. Method according to the preceding claim, characterized in that the treatment at neutral pH is at about 90 C.   8. Method according to any one of the preceding claims, characterized in that, in step e), the purified leach solution is precipitated by addition of calcium chloride (CaCl 2) or lime milk to obtain salts of Calcium of the metals of the group consisting of molybdenum, vanadium, tungsten and their mixtures.   9. Process according to any one of the preceding claims, characterized in that, in step e), non-selective precipitation of vanadium and molybdenum is carried out.   10. Process according to the preceding claim, characterized in that the purified leaching solution is acidified to a pH ranging from 2 to 3 by addition of hydrochloric acid HCl or nitric HNO3.   11. Process according to any one of claims 1 to 8, characterized in that, in step e), a selective precipitation of vanadium and molybdenum is carried out.   12. Process according to any one of the preceding claims, characterized in that a drying and / or calcination of the salts obtained in step e) is carried out.   13. Use of calcium salts selected from calcium molybdate (CaMoO4), calcium vanadate (CaV2O6), calcium tungstate (CaWO4) and mixtures thereof, obtained according to the process according to any one of claims 1 to 12, to make alloy steels.