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Influence of the chemical composition of the products of direct reduction of iron ore, used as an additive, on the process of liquid-phase sintering of aluminum-based alloys Materials Technology ”

Influence of the chemical composition of the products of direct reduction of iron ore, used as an additive, on the process of liquid-phase sintering of aluminum-based alloys « Materials technology »

Abstract of a scientific article on materials technologies, the author of the scientific work is Petr Petrovich Tarasov, Boris Yuryevich Pryadeznikov, Petr Petrovich Petrov, Ksenia Valerievna Stepanova, Ivan Petrovich Tarasov.

It has been established that individual particles of crushed iron ore from the Lena ore field have a polymineral composition, initially composed of grains of iron oxides with phenocrysts of grains of mainly silicon, aluminum and potassium oxides. Reduced ore powder, which has undergone additional concentration, is distinguished by a higher dispersion and high iron content, and the absence of potassium oxide. Sintered powder materials based on aluminum with the addition of reduced ore powders have been obtained.

It was found that an increase in the sintering temperature leads to a decrease in the residual porosity of the compacts, and a decrease in the concentration of the additive to 22.8 wt. % of sintered composites. An increase in the sintering temperature and the use of reduced ore powder with additional enrichment as an alloying additive contribute to an increase in the hardness of the samples..

Similar topics of scientific works on materials technologies, the author of the scientific work is Petr Petrovich Tarasov, Boris Yuryevich Pryadeznikov, Petr Petrovich Petrov, Ksenia Valerievna Stepanova, Ivan Petrovich Tarasov.

Influence of Chemical Composition of the Products of Direct Reduction of Iron Ore Used as Additive on the Process of a Liquid-Phase Sintering of Aluminum-Based Alloys.

It is found that individual particles of the crashed iron ore of the Lena ore field have polymineral composition. The particles are composed primarily of iron oxide grains with insets mainly of grains of oxides of silicon, aluminum and potassium. A reduced ore powder held further enrichment differs in higher dispersibility and high iron content and also the absence of potassium oxide. Aluminum-based sintered powder materials with the addition of the recovered ore powders are obtained.

It is found that increasing the sintering temperature leads to a reduction in the residual porosity of the compacts, and reducing additive concentration to 22.8 wt.% Leads to a decrease in the residual porosity of the sintered composites. Increasing the sintering temperature and used as a dopant powder reduced ore with an additional enrichment increases the hardness of the samples.

Text of the scientific work on the topic “Influence of the chemical composition of the products of direct reduction of iron ore, used as an additive, on the process of liquid-phase sintering of aluminum-based alloys”

UDC 621.762.2: 622.7: 669.094.1.

Influence of the chemical composition of direct reduction products.

iron ore used as an additive for the process of liquid-phase sintering of aluminum-based alloys.

P.P. Tarasov ***, B. Yu. Pryadeznikov **, P.P.

Petrov *, K.V. Stepanova *, I.P. Tarasov **

* Institute of Physical and Technical Problems of the North named after V.P. Larionov SB RAS, Yakutsk ** North-Eastern Federal University named after M.K. Ammosova, Yakutsk.

Annotation. It has been established that individual particles of crushed iron ore from the Lena ore field have a polymineral composition, initially composed of grains of iron oxides with phenocrysts of grains of mainly silicon, aluminum and potassium oxides. Reduced ore powder, which has undergone additional concentration, is distinguished by a higher dispersion and high iron content, and the absence of potassium oxide.

Sintered powder materials based on aluminum with the addition of reduced ore powders have been obtained. It was found that an increase in the sintering temperature leads to a decrease in the residual porosity of the compacts, and a decrease in the concentration of the additive to 22.8 wt. % – sintered composites. An increase in the sintering temperature and the use of reduced ore powder with additional enrichment as an alloying additive contribute to an increase in the hardness of the samples..

Key words: liquid phase sintering, aluminothermy, iron ore, direct reduction of ore, sintered material.

Influence of Chemical Composition of the Products of Direct Reduction of Iron Ore Used as Additive on the Process of a Liquid-Phase Sintering.

of Aluminum-Based Alloys.

P.P. Tarasov ***, B.Y. Pryadeznikov **, P.P.

Petrov *, K.V. Stepanova *, I.P. Tarasov **

* Larionov Institute of Physical and Technical Problems of the North SB RAS, Yakutsk ** M.K. Ammosov North-Eastern Federal University, Yakutsk [email protected]

Abstract. It is found that individual particles of the crashed iron ore of the Lena ore field have polymineral composition. The particles are composed primarily of iron oxide grains with insets mainly of grains of oxides of silicon, aluminum and potassium. A reduced ore powder held further enrichment differs in higher dispersion and high iron content and also the absence of potassium oxide. Aluminum-based sintered powder materials with the addition of the recovered ore powders are obtained.

It is found that increasing the sintering temperature leads to a reduction in the residual porosity of the compacts, and reducing additive concentration to 22.8 wt.% Leads to a decrease in the residual porosity of the sintered composites. Increasing the sintering temperature and used as a dopant powder reduced ore with an additional enrichment increases the hardness of the samples.

Key words: liquid-phase sintering, aluminothermy, iron ore, direct reduction of ore, sintered material.

TARASOV Petr Petrovich – candidate of technical sciences, associate professor, senior researcher; PRYADEZNIKOV Boris Yurievich – leading engineer; PETROV PETROV – PhD in Physics and Mathematics, Leading Scientist; STEPANOVA Ksenia Valerievna – research assistant; TARASOV Ivan Petrovich – Master’s student.

The rapid rates of industrial development in the North-Eastern zone of the Russian Federation require the use of new structural and tool materials with special functional characteristics, while from an economic point of view, it is expedient to use local mineral raw materials for their creation, including products of direct reduction of local iron ores. The methods of non-blast-furnace direct reduction of iron applied on an industrial scale are based on the use of hydrocarbons as a source of reducing agent: natural gas [1], coal [2], coal tar [3]. Their disadvantages include the carburization of the reduced metal, the likelihood of metal contamination with harmful impurities (P and P), the multistage process, and the formation of hazardous waste (CO2). The use of hydrogen as a reducing agent makes it possible to obtain products with a low content of harmful impurities while simultaneously increasing the environmental conditions of production.

Of the main innovative technologies for steel production, according to research by German specialists, for the period up to 2050, the most promising is the technology of direct reduction of iron ore with hydrogen [4], experiments are being carried out to enrich iron ores with hydrogen [5].

Currently, the staff of the Institute of Physical and Technical Problems. V.P. Larionov SB RAS and North-Eastern Federal University named after M.K. Ammosov, a joint research work is being carried out on the direct reduction of iron ore of the Lena ore field with hydrogen [6].

The purpose of the work is to develop a technology for the direct reduction of iron ore with hydrogen using the products of processing of ore raw materials as alloying additives in the preparation of sintered alloys based on aluminum by powder metallurgy..

Investigation of the regularities of sintering systems based on aluminum is of great practical importance in connection with the development of powder metallurgy of alloys based on it. It is known that the introduction of solid refractory particles of the second phase into plastic aluminum increases its strength, hardness, heat resistance and wear resistance of sintered powder alloys while reducing the coefficients of friction and thermal expansion [7]. The use of aluminides – intermetallic compounds of aluminum with transition metals, including with iron as a hardening phase – is promising..

a method of creating new functional materials based on aluminum [8].

In this regard, the study of the processes occurring during liquid-phase sintering, their contribution to the volumetric changes of powder bodies with interacting components, is of particular relevance. Investigation of the processes of sintering aluminum with additives of transition metal powders is a scientific problem closely related to the practical task of creating a new generation of composites based on aluminum..

Materials and experimental technique.

In this work, samples from the occurrence of ferromanganese ores in the upper reaches of the river were studied. Mundu-ruchu (left tributary of the Amga river) of the Lena ore field of the Republic of Sakha (Yakutia).

The method of direct reduction of metals with hydrogen, as a technological process, consists in heating the prepared, i.e. ore crushed to a certain size in a reducing gas, in this case, hydrogen. The reduction was carried out at a temperature of 950 ° C for 40 min [9].

When obtaining sintered composites based on aluminum, standard aluminum powder of the ASD-1 grade (TU 48-5-22687) was used. To reveal the influence of the chemical composition of the alloying additive on the process of liquid-phase sintering, iron powder of grade PZhV1 (GOST 9849-86), powders of reduced iron ore of size class -0.063 mm of two types were used: powder of reduced ore and powder of reduced ore that underwent additional enrichment, consisting of in dry regrinding in a vibrating mill with subsequent magnetic separation of the aqueous suspension of the powder and drying at a temperature of 120 ° C to an air-dry state.

The powders were mixed in a “drunken barrel” type mixer for 2 hours. They were preliminarily subjected to drying in a SNVS vacuum dryer according to the following regime: 1.5 hours at 150 ° C under forevacuum conditions. Forming of cylindrical specimens with a diameter and height of 10 mm was carried out in a steel mold, the initial porosity was 20%. Sintering was carried out in a SNVE furnace in a vacuum at a pressure of 0.110-3 Pa and a temperature from 700 to 900 ° C.

The density of the pressed samples was determined geometrically. In case of loss or distortion of the correct geometric shape, the method of hydrostatic weighing was used.

Brinell hardness was evaluated according to GOST 9012-59 on an Omag Affri 206RTD device.

Results and discussion.

X-ray microanalysis of ore material particles was carried out using a Swift ED3000 energy dispersive spectrometer (Oxford Instruments) of a TM3030 scanning electron microscope (Hitachi). Sample preparation consisted of fixing powder particles on a copper substrate using a double-sided conductive carbon self-adhesive film, followed by blowing with compressed air to remove loose particles.

In fig. 1 shows the microstructure of particles of ore material with a size class of -0.063 mm after reduction (Fig. 1, a) and after reduction and additional enrichment (Fig.

1, b) with areas of scanning by a microprobe. After additional enrichment, regrinding of the reduced material leads to a decrease in the particle size, the subsequent magnetic separation of the aqueous suspension of the powder makes it possible to increase the iron content and remove potassium oxide (table), the presence of which was established during phase analysis [6].

Fig. 1. Microstructure of particles of ore material with a size class of -0.063 mm: a – after reduction; b – after recovery and additional enrichment.

The content of elements in the particles of ore material with a size class of -0.063 mm.

Chemical element Content, wt. %

after recovery after recovery and additional enrichment.

The study of the microstructure of the ore material particles in the characteristic rays of the elements allows us to conclude that individual particles have a polymineral composition, initially composed of grains of iron oxides with phenocrysts of grains mainly of silicon, aluminum and potassium oxides (Fig. 2, 3). The formation during reduction of grains containing only iron is evidenced by the presence of areas light in the rays of Fe and dark in the rays of O, Si, Al.

Almost the same distribution of O, Si, Al over the surface of particles (Fig. 2, b-d; Fig. 3, b-d) confirms the presence of hard-to-reduce oxides SiO2 and Al2O3.

Potassium oxide has a more uniform distribution, practically without the formation of large individual inclusions (Fig. 2, e), which makes it possible to reduce its content in the powder during additional enrichment..

According to the results of earlier studies of powder systems aluminum-transition metal (Al-Ni, Al-Ti, Al-Cr), the greatest scientific and practical interest is the area of ​​metal-additive concentrations up to 20 at. % [7]. With this in mind, alloys with an additive content of 22.8 and 26.8 wt. %.

The Al-Fe system under study is characterized by the release of a large amount of heat during the formation of intermetallic compounds. A thermal explosion with the appearance of a liquid phase can cause abrupt changes in the volume of the compact and loss of shape of the briquette. In addition, to eliminate the effect of adsorbed and pore gases on the sintering process, briquette degassing is required..

To prevent loss of shape, it is necessary to control the heating rate and carry out solid-phase annealing at temperatures below the temperature of the appearance of the liquid phase. During solid-phase annealing on the surface of iron particles due to the diffusion of aluminum atoms, about-

Fig. 2. Microstructure of ore material particles after reduction in characteristic rays of elements: a – Fe; b – O; c – d – A1; d – K.

Fig. 3. Microstructure of ore material particles after reduction and additional enrichment in characteristic rays of elements: a – Fe; b – O; c – Si; r – Al.

a refractory intermetallic layer develops. With further sintering, this layer slows down the process of alloy formation and reduces the rate of heat release at the time of the appearance of the liquid phase. With a sufficient amount of refractory additive particles during solid-phase annealing, a solid-phase compact skeleton is formed, which ensures the constancy of the shape of the powder body during liquid-phase sintering..

Based on the foregoing, sintering of samples based on ASD-1 aluminum powder was carried out according to the regime with degassing solid-phase annealing at t = 500 ° C for 30 min, after which the furnace temperature was raised to the sintering temperature tCIl at a rate of 15 ° C / min..

It was found that samples with an alloying addition of iron powder of grade PZhV1 undergo shrinkage over the entire range of sintering temperatures (Fig. 4). Residual porosity of samples with an iron content of 22.8 wt. % (Fig. 4, a) and 26.8 wt. % (Fig. 4, b) is at the level of 10%.

Beginning with a temperature of 700 ° C and above, a distortion of the



shape of the compacts is observed, leading at a sintering temperature of 800 ° C to a complete loss of the geometric shape of the samples. Samples with the addition of reduced ore retain the correct geometric shape in almost all studied ranges of changes in sintering temperature and additive content.

Samples with the addition of reduced ore are characterized by a lower degree of shrinkage during sintering; at sintering temperatures below 750 ° C, an increase in the volume of powder bodies is noted (Fig. 4). There is an effusion-

which testifies to the low wettability of particles of the solid liquid phase [10], and, as a consequence, the difficulty of the process of liquid-phase sintering. An increase in the sintering temperature to 800 ° C leads to a decrease in the residual porosity of the compacts. A decrease in the residual porosity of briquettes during liquid-phase sintering can also be one of the reasons for liquid sweating, since the porous solid skeleton of the sample will shrink and squeeze out the liquid phase from the shrinking pores [11].

The absence of sweating of the liquid phase on the surface of the samples at a sintering temperature of 800 ° C indicates a higher wettability of the solid phase of the liquid, which can be explained by the passage of the alumothermic reaction of additional reduction of surface oxide films on particles of reduced ore at a given temperature..

At the same time, a decrease in the concentration of the additive to 22.8 wt. % leads to a decrease in the residual porosity of the sintered composites. Better sintering ability of briquettes is observed practically in the entire range of sintering temperatures, where powder of reduced ore with additional enrichment was used as an alloying additive..

Residual porosity of sintered alloys is one of the main factors affecting the structure and mechanical properties of powder materials. The results of measuring the hardness of sintered specimens are shown in Fig. 5. Higher residual porosity of sintered alloys with the addition of reduced ore, in comparison with composites with the addition of PZhV1 powder, leads to significantly higher.

formation of the liquid phase on the surface of the samples, low hardness indicators of alloys.

Fig. 4. Dependence of the residual porosity of the sintered alloys on the sintering temperature. Additive content, wt. %: a – 22.8; b – 26.8.

Alloying additive: 1 – iron powder of grade PZhV1; 2 – reduced ore powder; 3 – powder of reduced ore that has undergone additional concentration.

650 700 750 800 650 700 750 800.

Sintering temperature, ° С Sintering temperature, ° С.

Fig. 5. Dependence of the hardness of the sintered alloys on the sintering temperature. Additive content, wt. %: a – 22.8; b -26.8.

Alloying additive: 1 – iron powder of grade PZhV1; 2 – reduced ore powder; 3 – powder of reduced ore that has undergone additional concentration.

An increase in the sintering temperature to 800 ° C improves the wettability of particles of the solid liquid phase in the samples with the addition of reduced and additionally concentrated ore, intensifies the process of liquid-phase sintering and increases the hardness of the sintered alloys, especially when the content of the reduced ore additive is 22.8 wt. % (Fig. 5, a).

It was found that individual particles of ore material have a polymineral composition, initially composed of grains of iron oxides with phenocrysts of grains mainly of silicon, aluminum and potassium oxides. Reduced ore powder that has undergone additional enrichment is distinguished by a higher dispersion and increased iron content, the absence of potassium oxide.

Sintered powder materials based on aluminum with the addition of reduced ore powders have been obtained. It has been established that an increase in the sintering temperature leads to a decrease in the residual porosity of compacts, the elimination of sweating of the liquid phase on the surface of the samples, which indicates better wettability of the solid phase of the liquid phase, which can be explained by the passage of the alumina-thermal reaction of additional reduction of surface oxide films on particles of reduced ore..

At the same time, a decrease in the concentration of the additive to 22.8 wt. % leads to a decrease in the residual porosity of the sintered composites. The best sintering capacity of briquettes is observed practically in the entire range of sintering temperatures, where.

powder of reduced ore with additional enrichment was used as an alloying additive.

Measurement of the hardness of sintered composite alloys based on aluminum with the addition of reduced ore powders indicates that an increase in the sintering temperature and the use of reduced ore powder with additional enrichment as an alloying additive lead to an increase in the hardness of the samples..

When refining the ore beneficiation method, it seems promising to use the method of direct reduction of ore with hydrogen to obtain a concentrate with its subsequent use as a raw material for obtaining high-quality steels and alloys..

The authors are grateful to V.S. Achikasova, the leading engineer of the ISSP SB RAS. for help in performing the experimental part of this study.

This work was partially supported by the Program of Comprehensive Scientific Research in the Republic of Sakha (Yakutia) aimed at the development of productive forces and the social sphere for 2016-2020 of the Academy of Sciences of the Republic of Sakha (Yakutia).

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