KR100475042B1 - 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, process for preparing the same, and alloying agent comprising the same - Google Patents

Abstract

The present invention relates to a mass further containing iron and at least one of a group 5 or 6 element 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. Therefore, the mass in a metal melt melts rapidly.

Description

Mass additives containing iron and at least one of Group 5 or 6 elements of the periodic table for alloying additives, preparation method thereof and alloying additives comprising same {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, PROCESS FOR PREPARING THE SAME, AND ALLOYING AGENT COMPRISING THE SAME}

The present invention relates to a mass further containing at least one of iron and a group 5 or 6 element of the periodic table, its use and production method, and in particular, molybdenum and tungsten may be considered as additional containing elements.

The mass in DE-A-196 22 097 is formed of iron / molybdenum containing 60 to 80% by weight of molybdenum and is described for use as an alloying additive in iron and molybdenum containing metal melts.

Molybdenum is used, for example, as an alloying element for producing high strength structural steel and alloy cast iron containing molybdenum, as well as in molybdenum containing steel, corrosion resistant steel, acid resistant steel, heat resistant steel and nickel base alloys.

When manufacturing molybdenum-containing alloys, steels and cast iron, most of the molybdenum needed to contribute to the alloying is molybdenum-containing revert scrap or briquetted molybdenum trioxide (MoO ₃ ) for economic reasons. It is added to the melt in the form.

Since molybdenum can be added in an oxidative form because iron acts as a reducing agent in molten steel, MoO ₃ transforms into metal molybdenum. However, these molybdenum addition methods are different in operation. Steel is vaporized MoO ₃ is very easy in a liquid phase at a temperature / evaporation, or placed on the slag, MoO ₃ is insufficiently immersing it may cause a great loss during manufacturing and salpyeoya carefully MoO ₃ that the depth penetration in the melt.

During the so-called secondary metallurgical post-treatment, the molybdenum amount is precisely measured against so-called ferromolybdeum for the smelting finish of the steel, the reduction of pollutant gas components (oxygen, nitrogen), the accurate setting of the desired casting temperature and the final analysis of the steel. Setting is effective.

Ferro Molybdenum 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, metal thermodynamic manufacturing by the thermite process is complicated. The use of expensive reducing agents such as aluminum or ferrosilicon is required. The process can only be automated to a limited extent. This result becomes ferro-molybdenum expensive compared with molybdenum trioxide (MoO ₃ ).

The disadvantage of ferromolybdenum prepared according to the thermite process is when alloying a relatively high mass density (e.g. about 8.8 g / cm ^{3 for} standard FeMo70), for example a steel melt (density of about 7.5 g / cm ³ ). In other words, the components sink to the bottom of the melting vessel, forming a hard-to-melt precipitate that only emanates from subsequent melting. Melting, such as ferromolybdenum masses, in a liquid steel bath is more difficult because the melting point of the material is high, approximately 1950 ° C., in the case of conventional commercial FeMo 70 qualities. Since the temperature in the bath is considerably lower than this level, current FeMo component melting can only be affected by the diffusion process, which requires a long time.

Melting of ferromolybdenum prepared according to the thermite process is basically performed according to the following mechanism. Alloy masses 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 liquid iron. The outer layer of solidified steel is formed on the mass, which is due to the quenching effect of the immersion cooled FeMo mass. The outer layer gradually melts again as the heat transitions from the melt to the alloy mass. However, if the melting point of the alloy mass is higher than the temperature of the liquid steel bath, the alloy mass can be melted only by diffusion of iron from the steel bath into the boundary layer of the melt and the alloy mass and the reduction of the melting point associated therewith.

According to DE-A-196 22 097 described above, the mass is produced from iron / molybdenum by briquetting, and the iron / molybdenum mixture is obtained by reducing the molybdenum-trioxide / iron oxide mixture as a fine particle with a hydrogen containing gas. . Briquetting is achieved by adding a binder such as water glass to enhance particle binding. Masses are formed here with a bulk density of greater than 3.5 g / cm ³ .

On the other hand, the disadvantage of this process is the use of a binder that injects impurity elements such as silicon, sulfur and hydrogen into the steel, and on the other hand molybdenum is slag due to the low mass density and component resistance useful for this process. Is lost.

U.S. Patent 5,954,857 describes briquette production consisting of molybdenum oxide mixed with NaOH as a binder. When such briquettes are injected into the liquid iron melt, the molybdenum oxide is reduced to the metal molybdenum by the liquid iron, where iron oxide is formed. A disadvantage of this process is that there is a risk of molybdenum oxides being lost by the iron losses that are absorbed in the slag on the surface of the liquid iron and that occur upon reduction of the molybdenum oxides.

U. S. Patent 4,400, 207, for example, describes a method for producing a metal alloy as 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 briquetted. When such briquettes are introduced into the steel melt, the contained ferrosilicon acts as a reducing agent for molybdenum oxide which passes through the steel melt in the form of a metal.

This drawback is only possible if silicon oxide is formed as a reaction product which must be placed in the slag and further measures are taken in the steelmaking process used today.

1 is a view showing the pore size distribution of the FeMo mass produced in the process according to the present invention.

Figure 2 is an exemplary view showing a comparison of the melting rate of FeMo and standard FeMo of the present invention.

3 is a view showing a comparison of the melting rate of FeMo mass and standard FeMo of the present invention.

4 is a view showing a comparison of the melting rate of the ferro molybdenum produced according to the thermite process and the thermite process of the mass of the present invention.

FIG. 5 shows a further embodiment comparing the melt rates of FeMo masses and standard FeMo of the present invention. FIG.

FIG. 6 shows a further embodiment comparing the melt rates of FeMo masses and standard FeMo of the present invention. FIG.

The present invention provides a mass further containing at least one of Group 5 or Group 6 elements in iron and the periodic table for handling the melt at low cost, and aims to have improved meltability in the metal melt. In particular, the mass should not be immersed in the bottom of the metal melt and should be sufficiently resistant in terms of storage and transport. In addition, the quality of the metal melt must not be damaged by, for example, impurity elements in the mass that acts as a binder, and must prevent the loss of molybdenum and iron.

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

The mass according to the invention has pores and on the other hand due to the mass density the infiltrating slag can be covered on the metal melt, allowing the mass to penetrate into the metal melt. On the other hand, the vacancy of the mass of the present invention fills the vacancy of the mass with the metal melt by capillary action, causing the expansion of the interface between the metal melt and the mass and rapidly melting the region filled with the metal melt. Melting here means melting of the mass in the metal melt and a uniform distribution of the mass component.

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

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

Even if the density of the mass is lower than that of the liquid steel, the mass is immersed in the melt because of the kinetic energy of the component that should cover the corresponding drop height before entering the bath.

After melting of the outer region, the liquid steel penetrates into the cavity of the mass. Accordingly, the large interface between the produced mass and the melt is rapidly heated to diffuse iron into the boundary layer, thereby eventually melting the mass. In addition, the gas contained in the mass of the mass is rapidly heated and expands into the metal melt. The turbulence formed on the surface of the mass thus rapidly reduces the concentration gradient present on the alloying additive between the interface and the melt and increases the diffusion rate depending on the concentration gradient according to the Pick's law.

It is possible to save time and cost due to the high melt rate in the production 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, and preferably contains 60 to 80% by weight. It is preferable that the mass density of such a mass is 4.2-6.3 g / cm <^3> , and it is especially preferable that it is 4.5-5.7 g / cm <^3> .

According to another preferred embodiment, the mass contains 60 to 90% by weight of tungsten, preferably 70 to 85% by weight as additional elements. It is preferable that the mass density of such a mass is 4.7-8.4g / cm <^3> , and it is especially preferable that it is 5.8-7.4g / cm <^3> .

The invention also relates to the use of lumps in the manufacture of molybdenum-alloyed metal melts and / or tungsten-alloyed metal melts, particularly in the production of ferroalloy metal melts.

The invention also relates to a process for producing the mass, wherein the mass further containing at least one of iron oxide and at least one of the Group 5 or Group 6 elements of the periodic table is reduced to the respective metal.

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

US Pat. 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 in a hydrogen containing atmosphere. The shaft is used as a reducing flocculating medium, moving in the opposite flow by the product and reducing gas. This process produces pellets of low density and low frictional resistance.

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

Sintering is good at the temperature of 1000-1400 degreeC in air | atmosphere or preferably inert gas atmosphere for 15 to 60 minutes. At the sintering temperature of the present invention, iron mainly contained in the mass acts as a binder for particles contained in the sintering active phase and the mass. It is thus possible to prevent the mass from becoming too dense during the sintering process, thus eliminating the negative effect on the melting of the mass in the metal melt.

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

First Example

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

The compacted components are sintered at different times in an experimental sintering furnace under nitrogen atmosphere at 1170 ° C. After cooling the components out of the sintering furnace, the samples are separated from the components to measure porosity.

Table 1 below shows the porosity of FeMo masses as a function of sintering time and mass density with sintering. The porosity was measured here as a Hg pore measuring instrument. For comparison, the density and porosity of a conventional FeMo mass are shown as a comparative example.

TABLE 1

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

The graph of Sample 1 shows the pore size distribution of FeMo masses 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 FeMo masses. And the graph of Sample 3 shows the pore size distribution of the mass according to Sample 3. By simply selecting different sintering parameters (temperature and time period) from this, it is possible to vary the number of pores and the pore size distribution within a wide range.

The mass produced according to the method of the invention and the components of Sample 1 of Table 1 is melted in a steel melt in experimental electro-arc. (See the second embodiment)

2 shows a comparison of the melt rate of FeMo (prepared by a silicothermal process) with the FeMo of the present invention by way of example. When molten high speed steel (S-6-5-2, 1.3343) having a molybdenum content of 5% is obtained, a curve is obtained. The composition of the steel produced in the experiment is shown in Table 2 below.

TABLE 2

Data Details of Experimental Electric Arc Furnace

Power data: 3 phase, 200kw maximum power

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

Electrode: graphite diameter 100mm, automatic adjustment

Furnace Refractories: Magnesite Supply with Casting Nose with Effective Volume of approximately 1001

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

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

An important advantage of the mass according to the invention is that the mass melts faster in the steel melt compared to the standard FeMo, which allows the user to save time and money.

2nd Example

In large scale application experiments, the degradation behavior of the mass of the present invention is compared with that of conventional commercial ferromolybdenum prepared according to the thermite process.

The mass produced according to the method of the present invention and corresponding to the component of Sample 1 of Table 1 is melted in a steel melt of molten steel ladle having a loading amount of about 190 tons, and the melting rate of ferromolybdenum prepared according to the thermite process Compare with speed. Table 4 shows the composition of the steels produced.

TABLE 4

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

A total of six experiments were carried out, in which two of these charges had a particle size of 5 to 50 mm and the other four contained charges according to the invention in a typical commercial ferromolybdenum. Alloying additives are added through the slide from the bunker system. Samples are taken out with an automated subbalance system at intervals of about 20 seconds.

The experimental parameters are summarized in Table 5.

TABLE 5

In Fig. 3, the mass of the present invention melts much faster, yielding a large amount of molybdenum. As indicated by the curves associated with standard FeMo, less than 80% of the molybdenum added melts into the melt even after the melt has been treated for about 10 minutes. In practice this means that the melt must be heated once again in a pan to obtain commercial molybdenum yields, but requires expensive processing.

The third Example

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 having a charge of about 90 tons, and the melting rate is ferromolybdenum prepared according to the thermite process. Is compared with the melt rate.

Table 6 shows the chemical compositions of the steels produced.

TABLE 6

Four charges of steel with a melt weight of about 90 tons are produced. In the ladle washing station, FeMo prepared according to the thermite process is added to two kinds of charges and the mass of the present invention is added to two kinds of charges. The amount added can be seen in Table 7. After addition, samples are extracted from the melt at regular time intervals so that the increase in the molybdenum amount can be tested.

TABLE 7

Samples from slag samples and cold rolled strips are also made from steel and given during the experiment, so that the influence on the purity of the produced steel caused by using the mass of the present invention can be studied.

Figure 4 shows a comparison of the melting rate of the ferromolybdenum prepared according to the thermite process vs. the thermite process of the mass of the present invention. It can also be seen in sample 3 that the mass of the present invention melts faster in the steel compared to standard FeMo.

In the purity test of the produced product, little change occurs due to the use of the mass of the present invention for producing molybdenum alloy steel.

With reference to exemplary applications of steel melts, FIGS. 5 and 6 show additional embodiments of the melt rate of FeMo masses of the present invention over standard FeMo.

Claims (13)

As a manufacturing method of the mass which further contains iron and at least 1 element of the group 5 or 6 elements of a periodic table, An oxide containing at least one of iron oxide and at least one element of group 5 or 6 of the periodic table is reduced to the respective metal using hydrogen, Compacting and briquetting the reduced metal without adding a binder, By sintering the formed mass at 1000 ~ 1400 ℃, so that the mass has a porosity of 20 to 65% by volume Method of producing a mass characterized in that. A sintered mass which further contains at least one of iron and a group 5 or 6 element of the periodic table, obtained by the method according to claim 1, The mass is sintered mass, characterized in that having a porosity of 20 to 65% by volume. In claim 2, The mass is a sintered mass of 45 to 85% by weight of the molybdenum element as an additional element. In claim 3, The lump density of the mass is sintered mass, characterized in that 4.2 ~ 6.3g / cm ³ . In claim 2, The mass is sintered mass, characterized in that it contains 60 to 90% by weight of tungsten element as an additional element. An alloying additive for producing an alloy melt selected from molybdenum alloy melt and tungsten alloy melt, comprising the sintered mass of claim 2. In claim 5, The sintered mass of the mass of the mass is 4.7 ~ 8.4g / cm ³ . The method of claim 1, The mass is a method of producing a mass, characterized in that the porosity is 30 ~ 45% by volume. The method of claim 2, The mass is a sintered mass, characterized in that the porosity is 30 ~ 45% by volume. The method of claim 3, The mass is a sintered mass, characterized in that containing 60 to 80% by weight of the molybdenum element. The method of claim 4, wherein The mass density of the mass is 4.5 ~ 5.7 g / cm ³ Sintered mass, characterized in that. The method of claim 5, The mass is a sintered mass, characterized in that containing 70 to 85% by weight of tungsten element. The method of claim 7, wherein The mass density of the mass is 5.8-7.4 g / cm ^{3 The} sintered mass is characterized in that.