KR20020080409A - Porous agglomerates containing iron and at least one further element from groups 5 or 6 of the periodic table for use as an alloying agent - Google Patents

Abstract

The present invention relates to a mass comprising iron and at least one of the elements of group 5 or group 6 of the periodic table and relates to a mass having a porosity of 20 to 65% by volume, in particular 30 to 45% by volume. Thus, the massive material in the molten metal rapidly melts.

Description

POROUS AGGLOMERATES CONTAINING IRON AND AT LEAST ONE FURTHER ELEMENT FROM GROUPS 5 OR 6 OF THE PERIODIC TABLE FOR USE AS AN ALLOYING AGENT FOR ALUMINUM ADDITIVES, }

In DE-A-196 22 097, the mass water is formed of iron / molybdenum containing 60 to 80% by weight of molybdenum and is described as being used as an alloying additive in iron and molybdenum-containing metal melts.

Molybdenum is used for molybdenum-containing steels, corrosion-resistant steels, acid-resistant steels, heat-resistant steels and nickel-based alloys, as well as high-strength structural steels containing molybdenum and alloying elements for producing alloy steels.

When making molybdenum containing alloys, steel and cast iron, most of the molybdenum required to contribute to alloying is molybdenum-containing glass revert scrap or briquetted molybdenum trioxide (MoO ₃ ) because of economic reasons, To the melt.

Molybdenum can be added in an oxidizing form because iron acts as a reducing agent in the molten steel, so that MoO ₃ is transformed into metal molybdenum. However, this method of adding molybdenum differs in operation. Care should be taken to ensure that the MoO ₃ penetrates deep into the melt, as the MoO ₃ is very easily vaporized and / or vaporized or placed in the slag at a temperature at which the steel is liquid, since MoO ₃ is poorly soaked and can lead to significant losses during manufacture.

During the so-called secondary metallurgy post-treatment, the amount of molybdenum is precisely determined for the so-called massive ferromolybdeum for the finishing of steel smelting, the reduction of polluting gas components (oxygen and nitrogen), the precise setting of the desired casting temperature, It is effective to set.

Ferromolybdenum is an iron / molybdenum alloy containing 60 to 80% by weight of molybdenum and is produced through a metal thermodynamic process. When metal iron and molybdenum are melted together, the thermodynamic process complicates the fabrication of the metal thermodynamically. It is required to use a high-priced reducing agent such as aluminum or ferrosilicon. The process can only be done automatically to a limited extent. These results show that ferromolybdenum becomes expensive as compared with molybdenum trioxide (MoO ₃ ).

The disadvantage of ferromolybdenum prepared according to the thermite process is that when alloying a relatively high bulk density (for example about 8.8 g / cm ^{3 for a} standard FeMo 70), for example a steel melt (density of about 7.5 g / cm ³ ) , The components sink into the bottom of the melting vessel and form a hard-to-melt deposit that only dissipates in subsequent melting. Melting of the ferromolybdenum block or the like in a liquid bath is more difficult because the melting point of the material is as high as about 1950 DEG C in the case of ordinary commercial FeMo 70 quality. Since the temperature in the steel bath is considerably lower than this level, the current FeMo component melting can only be affected by the diffusion process and thus takes a long time.

Melting of ferromolybdenum produced according to the thermite process is basically carried out according to the following mechanism. Alloy masses that are immersed in the liquid melt sink to the bottom of the treater. This is caused by the high density of the components, which is higher than the density of the iron in the liquid phase. The outer layer of solidified steel is formed on the mass, which is due to the quenching effect of the submerged cooled FeMo mass. As the heat transfer from the melt to the mass of the alloy progresses, the outer layer gradually melts again. However, if the melting point of the alloy mass is higher than the temperature of the liquid bath, the alloy mass can be melted only by the diffusion of iron from the steel bath into the boundary layer of the melt and the mass of the alloy and the melting point associated therewith.

According to the abovementioned DE-A-196 22 097, the mass is produced from iron / molybdenum by firing and the iron / molybdenum mixture is obtained by reducing the molybdenum-trioxide / iron oxide mixture, which is a fine particle, . Firing is carried out by adding a binder such as water glass to improve particle bonding. A mass with a bulk density greater than 3.5 g / cm < ³ > is formed here.

On the other hand, the disadvantage of this process is the use of a binder that injects impurities such as silicon, sulfur, and hydrogen into the steel, and on the other hand, molybdenum is slagged due to its low bulk density and resistance to components useful in this process Is lost.

U.S. Patent No. 5,954,857 describes the manufacture of briquettes consisting of molybdenum oxide mixed with NaOH as binder. When such briquettes are injected into a liquid iron melt, the molybdenum oxide is reduced to molybdenum metal by liquid iron, where iron oxides are formed. A disadvantage of this process is that there is a risk that the molybdenum oxide is lost due to the iron loss that occurs during the reduction of the molybdenum oxide, which is absorbed into the slag on the surface of the iron in the liquid phase.

U.S. Patent No. 4,400,207 discloses a method for producing a metal alloy in which, for example, molybdenum oxide is mixed with fine ferrosilicon powder in a stoichiometric ratio. As a binder, bentonite is mixed up to 5%, and then the mixture is granulated. When such briquettes are introduced into the steel melt, the contained ferrosilicon acts as a reducing agent for the molybdenum oxide passing through the steel melt in a metal form.

This disadvantage is that silicon oxide is formed as a reaction product which must be placed in the slag and is only possible if additional measures are taken in the steelmaking processes used today.

The present invention relates to a mass comprising iron and at least one element selected from Group 5 or Group 6 elements of the periodic table, its use and production method, and molybdenum and tungsten may be considered as additional elements.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the pore size distribution of the FeMo mass produced in the process according to the invention.

Fig. 2 is an exemplary diagram showing the comparison of the melting rates of FeMo and standard FeMo of the present invention.

FIG. 3 is a graph comparing the melting rates of the FeMo mass of the present invention with standard FeMo. FIG.

FIG. 4 is a graph comparing the melting rates of feromolybdenum produced according to the thermite process and the thermite process of the inventive mass.

5 is a diagram illustrating a further embodiment in which the melt velocity of the FeMo mass of the present invention is compared with the standard FeMo melt velocity.

6 is a diagram illustrating a further embodiment in which the melt velocity of the FeMo mass of the present invention and standard FeMo are compared.

The present invention provides a mass which further contains iron and at least one of the elements of group 5 or group 6 in the periodic table to handle the melt at low cost, and aims to have improved cost-melting properties in the metal melt. In particular, the bulk material should not be immersed in the bottom of the metal melt and should be sufficiently resistant to storage and transport. Also, the quality of the metal melt should not be impaired by, for example, impurities in the mass that act as a binder, and loss of molybdenum and iron should be avoided.

According to the present invention, this object is achieved if the porosity of the agglomerate is in the range of 20 to 65% by volume, especially 30 to 45% by volume.

The mass according to the invention has a pore and on the other hand the slag which has penetrated due to the bulk density can be covered on the metal melt and allows the mass to penetrate the metal melt. On the other hand, the pores of the mass of the present invention, on the other hand, fill the pores of the mass with the metal melt by the capillary phenomenon, causing an expansion of the interface between the metal melt and the massive substance, thereby rapidly melting the region filled with the metal melt. Here, melting means a uniform distribution of the melt and bulk component of the mass in the metal melt.

The melting process of the mass of the present invention in a metal melt can be described as follows.

After the massive water passes through the slag covered with the molten bath and is immersed in the melt, a boundary layer of solidified steel is formed on the surface of the massive water, and the steel is produced according to the rapid cooling effect of the cooled mass. This boundary layer is much thinner than the layer formed when producing the iron-based alloy produced by the thermite process if the heat capacity of the mass is low due to high porosity.

Even if the density of the massive water is lower than the density of the liquid steel, the massive water is immersed in the melt due to the kinetic energy of the component to cover the corresponding dropping height before entering the steel bath.

After melting of the outer zone, the liquid steel penetrates into the pores of the massive water. As a result, the large interface between the mass produced and the melt rapidly heats and the iron diffuses into this boundary layer, eventually melting the mass. In addition, the gas contained in the pores of the mass is rapidly heated and enters the metal melt and expands. Thus turbulence formed on the surface of the mass rapidly reduces the concentration gradient present on the alloy additive between the interface and the melt and increases the diffusivity depending on the concentration gradient according to Fick's law.

Time and cost savings can be achieved due to the high melting rate in the manufacture of alloyed metal melts.

According to a preferred embodiment, the mass of the present invention contains 45 to 85% by weight of molybdenum as an additional element, preferably 60 to 80% by weight. Bulk density The bulk water is preferably that of 4.2 ~ 6.3g / cm ³ is preferred, and 4.5 ~ 5.7g / cm ^3.

According to another preferred embodiment, the agglomerate contains from 60 to 90% by weight of tungsten as an additional element, preferably from 70 to 85% by weight. Bulk density The bulk water is preferably that of 4.7 ~ 8.4g / cm ³ is preferred, and 5.8 ~ 7.4g / cm ^3.

The present invention also relates to the use of agglomerates in the manufacture of ferroalloy metal melts, particularly when producing molybdenum-alloyed metal melts and / or tungsten-alloyed metal melts.

The present invention also relates to a process for producing bulk material, wherein the massive iron oxide and at least one of the Group 5 or Group 6 elements of the periodic table are reduced to respective metals.

U.S. Patent No. 3,865,573 relates to a process for the production of molybdenum powder and / or ferromolybdenum wherein a mixture of molybdenum oxide and / or molybdenum oxide and iron oxide is reduced in a two-step flow imaging process.

U.S. Patent No. 4,045,216 describes a process for producing molybdenum oxide pellets that are directly reduced based on two-stage reduction of molybdenum oxide pellets under a hydrogen containing atmosphere. The shaft is used as a reducing cohesive medium while moving to the opposite flow by the product and the reducing gas. This process produces pellets with low density and low frictional resistance.

The process according to the invention is characterized in that the reduced metal is compacted, in particular by briquetting by the addition of no binder, and the compact product formed is sintered.

The sintering is preferably effected at a temperature of 1000 to 1400 DEG C in the atmosphere or preferably in an inert gas atmosphere for 15 to 60 minutes. At the sintering temperature of the present invention, iron contained mainly in the bulk material acts as a binder for the particles contained in the sintering active phase and the mass. Therefore, it is possible to eliminate the negative effect on the melting of the bulk material in the metal melt by preventing the compacting of the bulk material during the sintering process.

Hereinafter, the present invention will be described in more detail with reference to three exemplary embodiments and FIGS. 1 to 6.

First Embodiment

A powder mixture prepared by reducing a mixture of oxides of technical impurities of both metals under a hydrogen atmosphere, consisting of 74% of molybdenum, 21% of iron, 5% of oxidative contaminants such as silica, aluminum oxide and calcium oxide, It is made compact by massive water of 60mm in diameter and 40mm in height.

The thus compressed components are sintered at different temperatures in an experimental sintering furnace under a nitrogen atmosphere at 1170 ° C. After the components are cooled and removed from the sintering furnace, the sample is separated from the components and the porosity is measured.

Table 1 below shows the porosity of the FeMo mass as a function of sintering time and bulk density by sintering. The porosity was measured as Hg pore size. For comparison, the density and porosity of conventional FeMo masses are shown as comparative examples.

[Table 1]

Figure 1 shows the pore size distribution of the FeMo mass produced in the process according to the invention. The particle size of the agglomerate is 2 to 4 mm. The measurement was performed with a Hg pore meter at a mercury pressure of 200 mm.

The graph of Sample 1 shows the pore size distribution of the FeMo mass after sintering at 1170 ° C as in Table 1. The molybdenum content of this mass is 74%. The graph of Sample 2 shows the pore size distribution of the FeMo mass. And the graph of Sample 3 shows the pore size distribution of the mass according to Sample 3. [ From this, only the selection of the different sintering parameters (temperature and time period) can change the number of vacancies and pore size distribution over a wide range.

The mass produced according to the method of the present invention and the components of sample 1 of Table 1 are melted into a steel melt in a laboratory electric arc furnace. (See the second embodiment)

Figure 2 shows the comparison of the melting rates of FeMo of the present invention with standard FeMo (made by silicothermal process) in an exemplary manner. When a high-speed steel (S-6-5-2, 1.3343) having a molybdenum content of 5% is melted, a curve is obtained. The composition of the steel produced in the experiment is shown in Table 2 below.

[Table 2]

Data details of the experimental electric arc furnace

Power data: 3 phase, maximum power 200kw

Voltage: 52 / 63.5 / 75 / 86.5 / 90/110/120/150 V

Electrode: graphite diameter 100mm, automatic adjustment

Non-refractory: Supply of magnesite with cast nose with effective volume of approximately 1001

The weight of the experimental melt is 300 kg. The melt was used in a three phase electric arc furnace as a set-up charge. That is, the steel composition is set to a pure iron melt by adding a corresponding amount of iron alloy. As a first step, all alloying elements except Mo are added and set according to the target analysis. The steel bath is covered with calcium aluminate slag to prevent re-oxidation.

In the first experimental melt, the amount of molybdenum is set according to the thermite process set by adding ferromolybdenum having a particle size of 5 to 50 mm. After FeMo is added, the sample is extracted from the melt in a short time. Except for this, the melt in the second experimental melt is prepared in the same way, and the inventive mass is used to set the amount of molybdenum. It can be seen that the mass of the present invention (indicated by the dashed line in Fig. 2) melts much faster than the standard FeMo (indicated by the solid line in Fig. 2).

An important advantage of the mass according to the invention is that the mass is melted faster in the molten steel than in the standard FeMo, which saves time and money.

Second Embodiment

In a large-scale application experiment, the decomposition behavior of the bulk of the present invention is compared with the decomposition behavior of conventional commercial ferromolybdenum produced according to the thermite process.

The masses produced in accordance with the process of the present invention and corresponding to the components of sample 1 of Table 1 are melted in the molten steel of molten steel rafts with a loading of about 190 tonnes and the melt rate is measured by melting of ferromolybdenum produced according to the thermite process Compare with speed. Table 4 shows the composition of the steel produced.

[Table 4]

During the test, the steel bath prevents reoxidation by calcium aluminate slag and improves the homogenization, and the melt is washed with Ar by flame lance introduced into the melt from the top.

All six types of experiments are carried out, in the case of commercial commercial ferromolybdenum, two of these charges have a particle size of 5 to 50 mm and the remaining four contain the charge according to the invention. Alloying additives are added from the bunker system through the slides. Take samples out to an automated subbalance system at intervals of about 20 seconds.

The experimental parameters are summarized in Table 5.

[Table 5]

In Figure 3, the bulk material of the present invention melts much faster and produces a large amount of molybdenum. As shown in the curve associated with standard FeMo, even after processing the melt for about 10 minutes, less than 80% of the added molybdenum is melted into the melt. This actually means that the melt must be heated again in the pan to obtain commercial molybdenum yield, but it requires expensive processing.

Third Embodiment

The mass produced according to the method of the present invention and the material corresponding to Sample 1 of Table 1 are melted in a steel melt in a steel ladle with a charge of about 90 tons and the melt rate is determined by ferromolybdenum ≪ / RTI >

Table 6 shows the chemical composition of the steel produced.

[Table 6]

Four kinds of charges of steel having a weight of about 90 tons are produced. In a lath flushing station, FeMo, prepared according to the thermite process, is added to two charges and the inventive mass is added to two charges. The amount added can be seen in Table 7. After the addition, a sample is extracted from the melt at regular time intervals to test for an increase in molybdenum content.

[Table 7]

Samples from slag samples and cold rolled strips are also prepared from the steel and given during the experiment, so that the effect on the purity of the produced steel caused by the use of the inventive mass can be studied.

Figure 4 compares the melting rates of ferromolybdenum produced according to the thermite process of the massive mass of the present invention versus the thermite process. Also in Sample 3, the mass of the present invention can be seen to be rapidly melted in the steel compared to standard FeMo.

In the purity test of the produced product, little change occurs by the use of the inventive mass for producing molybdenum alloy steels.

Referring to the exemplary application of the steel melt, Figs. 5 and 6 show a further embodiment of the melt rate of FeMo agglomerates of the present invention for standard FeMo.

Claims (7)

Iron and at least one element of Group 5 or Group 6 elements of the periodic table, Characterized in that the mass has a porosity of 20 to 65% by volume, in particular 30 to 45% by volume. The method of claim 1, Wherein the massive material contains 45 to 85% by weight, preferably 60 to 80% by weight, of the molybdenum element. 3. The method of claim 2, Wherein the lump density of the mass is 4.2 to 6.3 g / cm ³ , preferably 4.5 to 5.7 g / cm ³ . The method of claim 1, Wherein the massive material contains 60 to 90 wt%, preferably 70 to 85 wt% of tungsten element. 5. The method of claim 4, Wherein the mass density of the mass is 4.7 to 8.4 g / cm ³ , preferably 5.8 to 7.4 g / cm ³ . Use of a mass according to any one of claims 1 to 5 as an additive for producing an alloy melt, in particular a molybdenum alloy melt and / or a tungsten alloy melt. A process for producing a mass according to any one of claims 1 to 5, wherein an oxide containing at least one element selected from Group 5 or Group 6 elements of iron oxide and periodic table is reduced to a respective metal, Characterized in that the reduced metal is compacted without the addition of a binder, and in particular the compact product formed by briquetting is sintered.