Startseite Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction
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Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction

  • Deqing Zhu , Yanhong Luo EMAIL logo , Jian Pan und Xianlin Zhou
Veröffentlicht/Copyright: 17. April 2015
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High Temperature Materials and Processes
Aus der Zeitschrift High Temperature Materials and Processes Band 35 Heft 2

Abstract

Siderite is one of the significant iron ore resources in China and yet is difficult to upgrade by traditional beneficiation processes. A process of coal-based direct reduction–magnetic separation was successfully developed for the beneficiation of siderite. However, few studies have thoroughly investigated the mechanism of the direct reduction of siderite. In order to reveal the reaction mechanism of coal-based direct reduction of siderite lump, thermodynamics of direct reduction was investigated with coal as the reductant. The thermodynamics results indicate that coal-based direct reduction process of siderite lump at 1,050°C follows the steps as FeCO3→ Fe3O4→ FeO → Fe, which is verified by chemical titration analysis, X-ray diffraction and scanning electron microscope. The microstructure of siderite sample varies with different reduction stages and some 45% porosity induced by thermal decomposition of siderite is conductive to subsequent reduction. The conversion of FeO to Fe is the main reduction rate-controlling step. The reduced product with the metallic iron size over 30 μm can be effectively beneficiated by wet magnetic separation after grinding. The obvious layered structure of reduced product is due to different heat transfer resistance, CO and CO2 concentration.

Keywords: siderite lump; coal-based direct reduction; reduction reaction mechanism; thermal decomposition; thermodynamics

Introduction

Siderite resource is abundant in China with proven reserves of 1.83 billion tons, accounting for 14% of total iron ores. Fortunately, the minable reserves reaches 1.82 billion tons [1]. However, siderite is refractory to be beneficiated and rarely directly used for iron making due to its higher loss on ignition (LOI), low iron grade, decomposition of carbonate and a significant amount of substitution of Mg, Ca, Mn for Fe in the carbonate lattice. Some high-grade siderite directly used for smelting iron and steel is less than 10% of its total reserves [2]. Thus, it is necessary to develop an effective process to utilize siderite. Recently many researches have been focused on magnetizing roasting low-intensity magnetic separation, high-intensity magnetic separation, flotation and joint separation processes, only a few on direct reduction–low-intensity magnetic separation process, but without satisfying results or recommended industrial experimental parameters [3–6]. Yan et al. [6] conducted reduction tests on a lean siderite of −4 mm at 1,200°C with coal as the reductant, but the temperature is not practical for industrial production. Recently, a process of coal-based direct reduction–magnetic separation of siderite lump was developed to provide a feasible way with siderite ores to manufacture burdens for electric arc furnace to make good quality special steel, and iron powder, assaying 91.56% Fe and 94.66% metallization degree, was manufactured at a total iron recovery of 88.46% [7], where direct reduction was conducted in a rotary kiln at pilot scale. There is a big difference with magnetite or hematite pellets in direct reduction behaviors, the system of coal-based direct reduction of siderite is much more complicated because of the thermal decomposition of siderite. Therefore, the reduction mechanism of the process should be further demonstrated.

In terms of siderite, the phase transformation and microstructure of thermal decomposition product are very complex and related to temperature, atmosphere, heating rate, properties of ore itself, etc. The researches on the thermal decomposition mechanism of siderite in oxygen and inert atmosphere are mainly focused on the reaction process [8–12], decomposition product characteristics [10, 13] and decomposition kinetics [14–18]. It is found that under the flow of oxygen, the oxidation is so rapid that the only detectable phase as the end product is hematite, α-Fe2O3, while magnetite and wüstite are observed in vacuum or in an inert atmosphere. However, there are very few researches about the reaction process of siderite in strong reducing atmosphere when using lignite as reductant. In previous research of the authors [19], preliminary study on mechanism process of siderite in coal-based direct reduction process was presented; however, further study of the iron phase transformation and the microstructural evolution is still needed. Yan et al. [20] studied the transformation process of siderite in reduction atmosphere at a series of temperatures, and revealed the final iron phases at different temperatures. In this paper, the iron phase transformation and microstructure change during the reduction process aimed at using rotary kiln process were completely illustrated.

Experimental

Samples

A Chinese domestic siderite lump ore, which was beneficiated by coal-based direct reduction process in small scale [7], was used as the raw material. The chemical compositions (Table 1) indicate the main valuable component for recovery is iron, assaying 35.43% Fe. The major impurities include silica, calcium, magnesium, manganese and alumina. The detrimental element content of phosphorus and sulfur are 0.033% and 0.24%, respectively. The sample possesses high LOI of 28.89%, which affects the firing performance during direct reduction. The mineral compositions of siderite (Table 2) were studied by mineralogical microscope, which indicate the major phase is siderite, and other phases include hematite, calcite, quartz, dolomite, Mn-bearing iron ore and alumina. Studies on occurrence of iron ore (Table 3) show that iron exists mainly in carbonate, assaying 83.12%, followed by 11.32% hematite.

Table 1:

Chemical compositions of siderite lump ore (mass %).

FetotalFeOSiO2Al2O3CaOMgOMnOPSLOI
35.4339.3510.752.664.911.382.360.0330.2428.89
Table 2:

Mineral compositions of siderite lump ore (mass %).

SideriteHematiteCalciteQuartzDolomiteMn-bearing iron oreAlumina
60.266.1211.7812.184.412.752.30
Table 3:

Occurrence of iron in siderite lump ore (mass %).

Iron phasesMagnetiteHematiteIron carbonateIron sulfideFerrosilite
Iron content1.174.0129.450.100.70
Distributions3.3011.3283.120.281.98

Lignite was used as reductant in the test. The industrial analysis of coal indicates fixed carbon of 52.99% and volatility of 30.33%, and sulfur content less than 1% (Table 4). The coal is considered appropriate for being used as reducing agent with low coking index and high soft smelting temperature over 1,180°C.

Table 4:

Proximate analysis of coal sample (mass %).

MadVadAadFCadSt.adCoking index
7.5230.339.1652.990.622
[1]

Methods

The siderite and lignite samples were crushed and screened to the size of 16–25 mm and −5 mm, respectively. One-third of the total coal was firstly placed in the bottom of a Φ65 mm × 150 mm reduction jar made of stainless steel. Then siderite lump (mass fixed at 100 g) and the other two-thirds of the total coal were loaded into the jar, respectively, with the mass ratio of coal to ore at 1.5. Until the temperature of vertical electric furnace (Figure 1) (SK-8-13 type, China) reaches 1,050°C which was recommended in a previous study [7], the jar filled with samples was moved into the furnace and roasted for a given roasting time with thermocouple measuring temperature in the mixture bed.

Figure 1: Vertical electric furnace for direct reduction. 1 – silicon carbide tube; 2 – samples (coal + siderite); 3 – refractory material; 4 – thermocouples; 5 – corundum tube; 6 – control panel.
Figure 1:

Vertical electric furnace for direct reduction. 1 – silicon carbide tube; 2 – samples (coal + siderite); 3 – refractory material; 4 – thermocouples; 5 – corundum tube; 6 – control panel.

After roasting, the products were unloaded and quenched by water. Part of the reduced products were investigated by scanning electron microscope (FEI Quanta-200, the Netherlands) equipped with an energy-dispersive X-ray spectroscopy (EDS) to study the microstructure and mineralogical phase transformation. The rest of the reduced products were pulverized to 100% passing 0.074 mm to facilitate further investigation. Chemical compositions of the reduced product were performed by chemical analysis. X-ray diffractometry (XRD; Rigaku 2500, Japan) with CuKα radiation was performed on the pulverized samples, and the diffractograms recorded over an interval 10–80° of 2θ.

The porosity of roasted siderite lump was calculated by apparent density and true density, both of which were measured by Archimedes method and specific gravity bottle method, respectively. The formulae for working out apparent density and true density are given as Eq. (1) and Eq. (2):

(1)ρc=m1ρ/m3−m2

where ρc is the apparent density of roasted lump (in g/cm3), m1 is the mass of roasted lump in the air (in g), m2 is the mass of roasted lump in water (in g), m3 is the mass of soaked roasted lump eliminating the surface water (in g) and ρ is the density of water (in g/cm3).

(2)ρ0=m′2−m′1ρ/m′4−m′1−m′3−m′2

where ρ0 is the true density of roasted lump (in g/cm3), m1′ is the mass of specific gravity bottle (in g), m2′ is the mass of specific gravity bottle and roasted sample (in g), m3′ is the mass of specific gravity bottle, roasted sample and water (in g) and m4′ is the mass of specific gravity bottle and water (in g).

The expression for porosity of roasted lump is based on Eq. (3)：

(3)ε=(1−ρc/ρ0)×100

where ε is the porosity of roasted lump (in %), ρc is the apparent density of roasted lump (in g/cm3) and ρ0 is the true density of roasted lump (in g/cm3).

Figure 2: Equilibrium partial pressure of carbon monoxide in solid carbon direct reduction of siderite.
Figure 2:

Equilibrium partial pressure of carbon monoxide in solid carbon direct reduction of siderite.

Results and discussion

Thermodynamics of solid carbon direct reduction of siderite

The system of solid carbon direct reduction of siderite is complicated, mainly including the dissociation of siderite, Boudouard reaction and reduction of iron oxides. The relevant thermodynamic formulas calculated by Gibbs energy method are given as below, and the graph of equilibrium partial pressure of carbon monoxide in function of temperature is delineated in Figure 2.

(4)Mechanism IFeCO3 =FeO+CO2ΔGm0=−RTlnpCO2=114,139−171.06T;lnpCO2=−13,728.53/T+20.57
(5)3FeO+CO2=Fe3O4+COΔGm0=−RTln(pCO/pCO2)=−31,500+37.06T;ln(pCO/pCO2)=3788.79/T−4.46
(6)Mechanism II3FeCO3 =Fe3O4+2CO2+COΔGm0=−RTln(pCO22⋅pCO)=310,917−480.17T;ln(pCO22⋅pCO)=−37,396.80/T+57.75
(7)C+CO2 =2COΔGm0=−RTln(pCO2/pCO2)=166,550−171T;!ln(pCO2/pCO2)=−20,032.48/T+20.57
(8)Fe3O4 + CO=3FeO+CO2ΔGm0=−RTln(pCO2/pCO)=31,500−37.06T;ln(pCO2/pCO)=−3788.79/T+4.46
(9)FeO+CO=Fe+CO2ΔGm0=−RTln(pCO2/pCO)=−17,883+21.08T;ln(pCO2/pCO)=2150.95/T−2.54

Under inert atmosphere:

When iron carbonate is heated to the extent that its dissociation pressure reaches the total pressure of system, iron carbonate will start to dissociate sharply at the boiling temperature. Theoretically, in the inert atmosphere, the decomposition proceeds to form wüstite and carbon dioxide (mechanism I); however, some interaction between the two products occurs [Eq. (5)]. Carbon dioxide acts as an electron acceptor [9], thereby the Fe2+ is oxidized to Fe3+. As a result, part of the Fe2+ in wüstite is oxidized to Fe3+, resulting in magnetite as the final predominant solid phase (mechanism II). Also, it must be recalled that wüstite is metastable phase below 570°C and that at least some of the magnetite can result from the FeO redox disproportionation 4FeO = Fe3O4 + Fe. It can be seen from Figure 2 that when the temperature is elevated above 734°C, the equilibrium partial pressure of carbon monoxide produced in Eq. (6) is higher than that of Eq. (8) required, thus the reaction of Eq. (8) occurs. The ratio of FeO content to Fe3O4 content in the equilibrium system goes up with increasing temperature, and the accompanying CO equilibrium pressure required decreases.

Under solid carbon reduction atmosphere:

Based on the above-mentioned analysis, at atmospheric pressure in the absence of oxygen, the predominant product of siderite decomposition is magnetite. In terms of Eq. (6), when the ΔGm0 value is taken as zero, the starting decomposition temperature is obtained, that is, 375°C.

Between 375°C and 622°C, the carbon monoxide dissociated from siderite makes solid carbon precipitate and release carbon dioxide, with the Boudouard reaction taking place in reverse, since the CO equilibrium partial pressure of Boudouard reaction is below that of the decomposition of siderite.

When reduction temperature is above Tb of 622°C, carbon reacts with CO2 [Eq. (7)] and produces higher CO concentrate at higher temperature due to its endothermic character.

During 647°C to 697°C, Fe3O4 is reduced to FeO [Eq. (8)] and the CO concentration is between 42% and 58%. The region of Tc< T< Td is the stable zone of FeO phase.

With temperature rising to 697°C, the elemental iron begins to appear [Eq. (9)] where CO concentration is over 58%. When the temperature reaches 1,050°C, the CO concentration is nearly 100% due to the significant carbon gasification, which means the reduction of FeO to Fe is inclined to occur thermodynamically.

Therefore, the regions of T < 375°C, 375°C < T < 647°C, 647°C < T < 697°C and T > 697°C are the equilibrium stable fields of FeCO3, Fe3O4, FeO and Fe, respectively. Theoretically, the reaction process of siderite in the presence of solid carbon follows the steps as FeCO3→ Fe3O4→ FeO → Fe.

Process mechanism of coal-based direct reduction of siderite

Chemical composition change and phase evolution

The changes of chemical compositions with sample bed (coal + siderite) temperature in function of roasting time are given in Figure 3. Temperature of the mixture bed increases steadily over time and reaches the target reduction temperature of 1,050°C in about 50 min, then maintains at 1,050°C till the termination of reduction.

Figure 3: Heating rate curve and transformation of iron phases in roasted siderite during reduction process (C/Fe = 2.25).
Figure 3:

Heating rate curve and transformation of iron phases in roasted siderite during reduction process (C/Fe = 2.25).

By heating the sample to 400°C in 10 min, the contents of Fetotal and Fe2+ of quenched sample are 33.87% and 32.16%, respectively, which means that siderite has not decomposed yet. When the temperature was elevated from 400°C to 700°C, a quicker augment of total iron content combined with a local obvious diminishment in the ratio value of Fe2+/Fetotal is observed, which indicates that the decomposition of siderite happens, with more magnetite occurring.

When the temperature elevates from 700°C to 900°C in 10 min, the ratio of Fe2+/Fetotal reaches a peak value, which means the reduction of the vast majority of magnetite to wüstite.

The temperature reaches 900°C in 30 min, metallic iron content in reduced sample is about 0.55%, which indicates the very beginning of reduction from FeO to Fe, and that is the third stage of siderite reactions under coal-based system. With the Fe2+ content decreasing, the content of metallic iron enhances rapidly. Meanwhile, it can be revealed that reduction rate of wüstite in the initial stage is faster with metallization degree rising from 3.50% to 80.76% over 60 min, whereas the rate in the late stage is much slower with metallization degree elevating from 80.76% to 89.75% between the 100th minute and the 140th minute, only an increase by 8.99% over 40 min. With the reduction proceeding, compact iron layer forms and the diffusion resistance of CO becomes larger, so reduction rate gradually slows down. Obviously, the conversion of wüstite to metallic iron is the main rate-controlling step in the overall process.

The phase transformation of siderite in coal-based direct reduction was also confirmed by XRD method. The XRD patterns of pulverized samples reduced for different time are presented in Figure 4. Combined with Figure 3, siderite has not decomposed yet in the first 10 min due to the low temperature (<400°C). For the sample reduced for 20 min, magnetite phase is identified which indicates the decomposition of siderite. Based on the analysis of thermodynamics, magnetite is the main product of the reduction below 647°C where wüstite does not appear because of the depression of carbon monoxide, which agrees with the trend of δFe* in Figure 3. With temperature increasing, decomposition reaction accelerates. Half an hour later, there are still remaining siderite detected, and wüstite dominates the sample between 700°C and 900°C. On the other hand, minute quantities of metallic iron begin to occur, assaying 0.55%. This phenomenon verifies the coexistence of decomposition of siderite and reduction of iron oxides in the reaction system. With further reaction proceeding, dissociation of siderite has completely finished and most of the magnetite has been reduced to wüstite by strong reduction atmosphere above 1,000°C. After 40 min, the conversion of wüstite to metallic iron dominates.

Figure 4: XRD diagrams of siderite sample reduced for different time. S – siderite, M – magnetite, W – wüstite, I – iron, Q – quartz.
Figure 4:

XRD diagrams of siderite sample reduced for different time. S – siderite, M – magnetite, W – wüstite, I – iron, Q – quartz.

Microstructural analysis of roasted siderite

In order to investigate the relationship between phase evolution and microstructural change of reduced siderite, the porosity of products during reduction was measured and the scanning electron microscope was applied to study the microstructural evolution.

It can be seen from Figure 5 that with an increase of reduction time, conspicuous change of product porosity has been detected. The structure of raw siderite is compact and the porosity is only 2.33%. With reduction reaction processing, the porosity value elevates remarkably in the first 40 min due to thermal decomposition of siderite and the porous structure mainly forms at this stage. The porosity increases gradually after 40 min due to the removal of oxygen from iron oxide.

Figure 5: Porosity of roasted siderite lump.
Figure 5:

Porosity of roasted siderite lump.

Figure 6 shows the SEM microstructure and EDS analysis of siderite sample reduced for 30 min. It can be seen that some white spots and linear regions occur at the 20th minute, corresponding to intensive decomposing of siderite. Due to different crystal lattice between siderite and decomposition product magnetite, the lattice transformation from trigonal to isometric system leads to strong internal stress, then fissures and pores occur at the brims of newly formed magnetite. The carbon dioxide emitted by decomposition diffuses outward through these fissures and pores. As discussed in thermodynamics, the decomposition of siderite and reduction of iron oxides are influenced by temperature and atmosphere. Owing to the heat transfer, the temperature of the outer layer of the lump is higher than that of the inner layer. Furthermore, the outer layer of sample is exposed to reducing atmosphere, and inner layer temporarily remains the weak oxidation atmosphere because of the release of carbon dioxide. These effects lead to subsequent difference in microstructure. After 30 min, an obvious difference in microstructure is observed between the outer layer and the inner layer of reduced sample. Metallic iron grains appear at the brim of sample and distribute sporadically, the structure of metallic iron region is much looser and the size of pores and fissures is enlarged. Meanwhile, the inner layer structure is compact and the main phase conversion is magnetite to wüstite. Due to the crystal transformation, many fractures and pores appear which facilitate the diffusion of gas to reduction interface.

Figure 6: SEM and EDS of siderite sample reduced for 30 min. A, B – siderite; C – calcite; D – metallic iron; E – magnetite; F – wüstite; Black – pore.
Figure 6:

SEM and EDS of siderite sample reduced for 30 min. A, B – siderite; C – calcite; D – metallic iron; E – magnetite; F – wüstite; Black – pore.

Figure 7 illustrates the growth of metallic iron grains during the reduction process. Between reduction time of 40 min and 100 min, the metallic iron layer extends inward gradually and the elemental iron grains grow further with reduction of wüstite. Meanwhile, the impurities including calcium, manganese and magnesium are eliminated from iron grains to form complex fayalite with wüstite. However, the inner layer of sample still remains the compact structure that is not conductive to the diffusion of reducing gas, so the reduction rate decreases at the later stage of reduction process.

Figure 7: Microstructure of siderite sample reduced for 40–100 min. Bright – metallic iron; Gray – wüstite; Black – pore.
Figure 7:

Microstructure of siderite sample reduced for 40–100 min. Bright – metallic iron; Gray – wüstite; Black – pore.

For the siderite sample reduced for 140 min (Figure 8), wüstite has been reduced to metallic iron completely and metallic iron becomes the major iron phase. Average size of elemental iron grain increases from smaller than 10 μm at the 40th minute to over 30 μm at the 140th minute. There is apparent disparity in iron grain morphology between outer and inner layers. The iron grains in outer layer exhibit as snowflake-like structure with gangue impurities distributing at their brim, while iron grains in inner layer occur as worm-like morphology. Iron grains in inner layer associate tightly with gangue minerals and even wrap them (Figure 9). These different phenomena of growth mode of iron grains caused by the different temperature rate and CO concentration is worthy of further study.

Figure 8: Microstructure of siderite sample reduced for 140 min. Bright – metallic iron; Gray – gangue; Black – pore.
Figure 8:

Microstructure of siderite sample reduced for 140 min. Bright – metallic iron; Gray – gangue; Black – pore.

Figure 9: SEM and EDS of siderite sample reduced for 140 min. Bright – metallic iron; Gray – gangue; Black – pore.
Figure 9:

SEM and EDS of siderite sample reduced for 140 min. Bright – metallic iron; Gray – gangue; Black – pore.

To sum up, a good amount of characterization analysis was conducted in order to elucidate the phase changes thoroughly upon heat treatment. It can be concluded that reactions of siderite are complex under coal-based direct reduction process. Furthermore, the phase changes of siderite in the siderite-coal system are heavily dependent on the parameters with respect to heat transfer, such as size, shape, heating rate, etc. The results presented in this work illustrate the reaction mechanism for the current heating conditions and parameters. Given the magnitude of the subject, a schematic form of results is summarized in Figure 10. Siderite lump is assumed as ideal sphere object and schematic images clearly depict the phase transition pathway of siderite under coal-based direct reduction. Obviously, the alteration process follows the stepwise course as FeCO3→ Fe3O4→ FeO → Fe, and whether decomposition of siderite and reduction of iron oxides could coexist is heavily dependent on the heat transfer parameters.

Figure 10: Schematic diagram of phase transformation process of siderite under coal-based direct reduction.
Figure 10:

Schematic diagram of phase transformation process of siderite under coal-based direct reduction.

Conclusions

  1. Based on thermodynamics analysis, the reduction process of siderite in the presence of solid carbon follows the steps as FeCO3→ Fe3O4→ FeO → Fe, which is consistent with the experimental approaches in this study. The conversion of FeO → Fe is the main reduction rate-controlling step in coal-based direct reduction of siderite lump.

  2. The microstructure of reduced siderite lump sample varies with different reduction phases and around 45% porosity induced by thermal decomposition of siderite is conductive to subsequent reduction. The inner and outer layers of siderite lump during the decomposition and reduction present obviously different characteristics due to resistance of heat transfer and gas diffusion; the reaction rate of outer layer is much higher. At the end of reduction, the iron grains in the outer layer exhibit as snowflake-like morphology and impurities distribute at their brim. Meanwhile, inner layer grains occur as worm-like morphology, and associate closely with gangue minerals which are even wrapped by elemental iron grains.

  3. The refractory siderite is transferred into metal iron by coal-based direct reduction process and the size of metallic iron in the final reduced sample is over 30 μm, which can be easily liberated in grinding and effectively beneficiated by weak magnetic separator.

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Received: 2014-9-28
Accepted: 2015-1-28
Published Online: 2015-4-17
Published in Print: 2016-2-1

©2016 by De Gruyter

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Artikel in diesem Heft

  1. Frontmatter
  3. Numerical Simulation to Study the Effect of Arc Travelling Speed and Welding Sequences on Residual Stresses in Welded Sections of New Ferritic P92 Pipes
  4. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound
  5. Optimization of Microwave Roasting for Dechlorination of CuCl Residue under Oxygen-Enriched Condition
  6. Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints
  7. Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures
  8. Effect of Ultrasonic Treatment on the Solidification Microstructure of GCr15 Bearing Steel
  9. Effects of Ultrasonic Treatment on Microstructure and Properties of Al-Based Composites Reinforced by In Situ Al2O3 Nanoparticles
  10. High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys
  11. Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction
  12. EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction
  13. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings
  14. The Marker Conservation Law in Multiphase Systems
  15. Synthesis and Characterization of Strontium Carbonate Nanostructures via Simple Hydrothermal Method
https://doi.org/10.1515/htmp-2014-0176
Schlagwörter für diesen Artikel
siderite lump; coal-based direct reduction; reduction reaction mechanism; thermal decomposition; thermodynamics
Creative Commons
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Artikel in diesem Heft

  1. Frontmatter
  3. Numerical Simulation to Study the Effect of Arc Travelling Speed and Welding Sequences on Residual Stresses in Welded Sections of New Ferritic P92 Pipes
  4. Microstructural Evolution and Compressive Properties of Two-Phase Nb-Fe Alloys Containing the C14 Laves Phase NbFe2 Intermetallic Compound
  5. Optimization of Microwave Roasting for Dechlorination of CuCl Residue under Oxygen-Enriched Condition
  6. Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints
  7. Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures
  8. Effect of Ultrasonic Treatment on the Solidification Microstructure of GCr15 Bearing Steel
  9. Effects of Ultrasonic Treatment on Microstructure and Properties of Al-Based Composites Reinforced by In Situ Al2O3 Nanoparticles
  10. High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys
  11. Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction
  12. EAF Gas Waste Heat Utilization and Discussion of the Energy Conservation and CO2 Emissions Reduction
  13. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings
  14. The Marker Conservation Law in Multiphase Systems
  15. Synthesis and Characterization of Strontium Carbonate Nanostructures via Simple Hydrothermal Method
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