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2022, Vol.32 Num.7
Online: 2022-07-15
Summarization of Technology
Monographic Study
Production Technology
Energy Saving and Environmental Protection
Non ferrous Metallurgy
Metallurgy Talent
Metallurgical Science and Technology Award
Summarization of Technology
1
XIE Qi-mai, MA Qing-shuang, ZHANG Hai-lian, LI Hui-jun, GAO Qiu-zhi
Research status of elements alloying mechanism in alumina-forming austenitic heat-resistant steel
In order to improve the power generation efficiency of thermal power plants and effectively reduce environmental pollutions, it is necessary to increase the operating temperature and operating pressure of the thermal power unit. This puts forward higher requirements for structural steel, not only to possess good corrosion resistance in an environment with water vapor, but also to meet the requirement for mechanical properties at high temperatures. Alumina-forming austenitic (AFA) stainless steel possesses the ability to form a continuous and dense protective Al
2
O
3
scale at high temperature, which has better protective effect than Cr
2
O
3
scale. Multiple Precipitation phases such as MC, Laves, L1
2
-Ni
3
Al, etc. precipitate in the matrix of AFA steel, which can effectively improve the creep resistance. Therefore, AFA steel is expected to be used in thermal power station unit. Effects of alloying elements addition on microstructure evolution and precipitation phases in AFA steel are analyzed, and effects of alloying elements on creep and oxidation resistance are expounded. The future adjustment direction of alloying elements in AFA steel is prospected.
2022 Vol. 32 (7): 1-11 [
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Monographic Study
12
LAN Chen-chen, ZHANG Shu-hui, LIU Ran, LÜ Qing, LI Fu-min
Effect of K
(g)
on high temperature gasification kinetics of coke in N
2
-CO-CO
2
-H
2
O atmosphere
In order to understand the influence of alkali metals in high temperature zone on coke gasification process, the kinetic behaviors of coke gasification in the temperature 1 413-1 773 K were studied by thermogravimetric analysis under atmospheres of N
2
-CO-CO
2
-H
2
O and N
2
-CO-CO
2
-H
2
O-K
(g)
. The results show that K
(g)
has a strong positive catalytic effect on the gasification reaction of coke, which can significantly improve the effective internal diffusion coefficient (
D
e
) and interfacial reaction rate constant (
k
+
), reduce the activation energy of internal diffusion and interfacial reaction, and the influence of K
(g)
on internal diffusion is higher than that on interfacial reaction. With increase of reaction rate, the internal diffusion resistance (
η
i
) and interfacial reaction resistance (
η
C
) increase gradually, whereas K
(g)
tends to decrease
η
i
and
η
C
. Under the N
2
-CO-CO
2
-H
2
O atmosphere at 1 413 K, the controlling factor gradually changes from interfacial reaction to internal diffusion. At 1 473, 1 573, 1 673 and 1 773 K, the controlling factor is always interface reaction. Under the N
2
-CO-CO
2
-H
2
O-K
(g)
atmosphere, the controlling factor is the interface reaction.
2022 Vol. 32 (7): 12-19 [
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20
QI Teng-fei, HUANG Jun, SUN Jun-jie, ZAHNG Yong-jie
DEM simulation of sinter distribution in vertical cooling furnace
In order to study the permeability of sinter in vertical cooling furnace and improve the distribution of cooling gas, the slot model of single bin for vertical cooling furnace in Meigang was established. The charge and discharge process were simulated by discrete element method. Sinter and its porosity distribution in the vertical cooling furnace under steady-state conditions were obtained. The results show that during charging, the segregation distribution of sinter will occur due to the change of landing point. When the sinter flow is stable, there are three flow regions in the furnace cavity, quasi stationary region, mass flow region and convergent flow region. In terms of sinter distribution, the central area of furnace cavity contains more particles of 10-25 mm and 25-40 mm. More particles of 40-80 mm and 80-150 mm are distributed in the middle area. In the middle and upper part of the sidewall area, the mass fraction of 25-40 mm and 40-80 mm particles are higher, while the mass fraction of 80-150 mm particles in the lower part is higher. Such sinter distribution causes large particle segregation in the sidewall area and middle area of the furnace cavity, and small particle segregation in the center area. The porosity is distributed as "U" with larger in sidewall as well as central area, and smaller in middle area. Sinter in the sidewall area has the best air permeability, resulting in the easy escape of cooling gas from the sidewall area. In order to improve the distribution of cooling gas in the furnace, further research could be carried out from reducing the sinter size range and developing a new charge device.
2022 Vol. 32 (7): 20-26 [
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27
GAO Fei, YANG Wen-yuan, PENG Xiao-yan, LI Lin, WANG Ming-lin, ZHANG Yan-xiang
Influence of bottom blowing gas parameters on erosion rate of tuyere bricks
In order to investigate the influence of bottom blowing gas injection parameters (such as pressure, flow rate, nozzle hole diameter, etc.) on the erosion rate of tuyere bricks, the dissolution rate of table salt, borax, sodium carbonate, and the mixture of table salt and sodium carbonate in different proportions in water were compared, and then natural salt bricks were selected to simulate the material of tuyere bricks for erosion water simulation tests. The water was used to simulate the liquid steel, compressed air was injected in the 1∶10 plexiglass model, the injection parameters (pressure, flow, injection time)were changed, and the changes in the size of nozzle holes for tuyerebricks were measure before and after the injection, and then the erosion of tuyere bricks (radial erosion rate, axial erosion rate and erosion angle) was calculated.At last, the relationship between gas injection parameters and erosion rate of tuyere bricks were build. According to size of nozzle hole, parameters of injected gas and the dimensionless number of injection conditions (modified Froude number, Reynolds number and apparent Mach number, etc.), the flow condition of gas injected into molten pool was analyzed, such as equivalent volume and equivalent diameter of bubble in the gas flow, height of air column formed during the blowing process, transition of bubble flow and jet flow, etc. The research results show that the axial erosion and radial erosion velocities of tuyere bricks increase with the increase of bottom blowing air flow rate, and the erosion angle is little affected by the nozzle hole diameter and gas flow rate, which can improve the stirring effect of bottom blowing gas on the molten pool. These results have reference significance for the improvement of combined blowing technology.
2022 Vol. 32 (7): 27-34 [
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35
LIU Miao, LIU Zhong-qiu, WU Ying-dong, LEI Qi-an, LI Bao-kuan
Time-frequency analysis of level fluctuation behavior in argon blowing continuous casting mold
Time-frequency analysis is an effective method to explore the characteristics of fluctuation signals and reveal the internal mechanism of fluctuation phenomena. The time-frequency analysis method was applied to study the level fluctuation in argon blowing continuous casting mold, and it was used to process the level fluctuation data obtained by a water model experiment. The effects of various operating parameters such as argon blowing rate, casting speed, nozzle immersion depth and mold width on the level fluctuation were studied to explore the internal mechanism of level fluctuation. Results show that the frequencies with high amplitude are concentrated in 0-2.5 Hz, and the fundamental frequency with the largest amplitude is near 0.1 Hz. In addition, there are high peaks noticed at 1.5 Hz and 2.5 Hz. Based on the time domain analysis, level fluctuation intensity will be aggravated by increase of argon blowing rate and casting speed or decrease of nozzle immersion depth and mold width. Based on the frequency domain analysis, the casting speed, nozzle immersion depth and mold width strongly correlate with the fundamental frequency of level fluctuations, indicating that they are highly related to the main vibration sources.
2022 Vol. 32 (7): 35-43 [
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44
PEI Xi-shuo, JIA Dan-bin, TIAN Chen, YUAN Lei, YU Jing-kun
Effect of electric current pulse treatment on migration behavior of inclusions during solidification in steel
Electric current pulse (ECP) treatment was applied to steel during solidification process and its effect on the migration behavior of inclusions was investigated by observing and analyzing the morphology, quantity, size and composition of inclusions. The results show that under the influence of ECP treatment, the crystal nucleus falls off at the initial stage of solidification, which results in the formation of crystal rain. During the falling process of the crystal nucleus, the inclusions also migrate downward. With the increase of current density, the number of inclusions in upper and middle regions of ingots and the size of grain decrease. Compared with that without ECP treatment, it reduces the number and the area of inclusion in upper and middle regions of ingots by 46.9% and 35.6%, respectively, when the current density is 56.6 A/cm
2
under the current experimental condition. For the steel with high requirement of inclusion content, applying ECP treatment to control the formation and migration of crystal rain during ingot solidification is an effective technology to remove inclusions in steel and improve ingot quality.
2022 Vol. 32 (7): 44-50 [
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51
ZHANG Jie
Determination of activity interaction parameters between Mn and Al in Fe-Mn-Al-O melts
Due to lack of research on the activity interaction parameters between Mn and Al in high Mn and Al content molten steel and lack of reasonable thermal test methods, a new experimental method that could be used to study the thermodynamic properties of high Mn and Al content molten steel was obtained. The resistance furnace was used, and CaO-Al
2
O
3
slag was covered on the surface of Fe-Mn-Al melt to prevent the oxidation of Al and the volatilization of Mn, and ensure the accuracy of thermodynamic data. The mass ratio of metal to slag was 2.4. The sample placed in an Al
2
O
3
crucible and covered with a graphite crucible was equilibrated for 2 h under the conditions of 1 600 ℃ and Ar-H
2
gas mixture with a flow ratio of 9 to 1. The preliminary experimental results show that with the increase of Mn content, the Al content decreases. From the WIPF, the first and second-order activity interaction parameters,
e
Mn
Al
and
r
Mn
Al
, are determined to be 0.028 8 and -0.000 25, respectively.
2022 Vol. 32 (7): 51-56 [
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57
HUANG Qiao, REN Ying, ZHANG Li-feng
Evolution of MnS-MnTe inclusions during heating of tellurium treated sulfur-containing steel
The evolution of MnS-MnTe inclusions in tellurium treated high sulfur steel during the heating process was studied through laboratory experiments and thermodynamic calculations. The regularity and mechanism of change for MnS-MnTe inclusions were obtained. With the increase of the tellurium content and the Te/S mass ratio in the steel increased, the average diameter of MnS-MnTe inclusions increased while the average aspect ratio decreased. After heating, since MnS and MnTe in the steel matrix after heating fully grew and precipitated, the effect of modification after tellurium treatment on MnS inclusions was more obvious than that before heating. Meanwhile, compared with inclusions in samples before heating, with the increase of the Te/S mass ratio in the steel, the average diameter of inclusions was larger, the number density was lower and the area fraction was higher. With the increase of Te/S mass ratio in the steel, the proportion of dendritic Type II inclusions decreased while more spherical Type I and massive Type III precipitated in MnS-MnTe inclusions. Under the current experimental condition, after Te/S mass ratio reaching 0.33, the initial precipitation temperature of MnS was lower than the solidus temperature of the liquid steel, which was conducive to inhibit the formation of Type II MnS at the grain boundary during the eutectic reaction. When the Te/S mass ratio was higher than 1.35, numerous spherical pure MnTe inclusions precipitated in the steel matrix.
2022 Vol. 32 (7): 57-66 [
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67
FAN Ming-yang, ZHOU Cun-long, DUAN Jing-jing, GONG Jian-xiong, MA Guo-cai
Effect of intra-crystalline micropores on FeO rupture in FeO/Fe based on MD
The micropores in oxide skin directly affects the cracking performance of oxide skin. Molecular dynamics simulation software Lammps was used to simulate the tensile fracture of FeO/Fe polycrystalline model with micropores. The effect of micropore size on tensile fracture of FeO/Fe polycrystalline model with different numbers of micropore was studied. The results show that the tensile strength of FeO model presents a trend of decreasing→increasing→decreasing with the increase of micropore size at the same number of micropores, indicating that micro-pore size in a certain range can improve the tensile strength of material, but the it can reduce the fracture toughness of material at the same time.
CSP
values show that the regions of atomic disorder degree from high to low are as follows of micropore, grain boundary, FeO/Fe interface and inside the FeO polycrystal. The results provide a new idea for the study of fracture mechanism for oxide skin.
2022 Vol. 32 (7): 67-73 [
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74
MA Jian-zhong, HUANG Yi-jun, HUANG You-qiao, WANG Bo, ZHANG Ning, MENG Li
Texture characteristics and high temperature stress relaxation behaviors of Nimonic 80A alloy bolt
The microstructure and texture characteristics of Nimonic 80A superalloy bolt were studied using SEM and EBSD techniques, meanwhile, stress relaxation behaviors at different high temperatures and the corresponding microstructure as well as texture evolution were analyzed. The results showed that no strong texture was obtained in γ phase, and no correspondence was shown between γ grain orientation and grain size. γ′ phase and Cr carbides were the main second phase in the alloy. The γ′ phase was dispersed in the matrix, while Cr carbides precipitated at grain boundaries and showed “chain” distribution along axial direction of the bolt respectively. The distribution characteristics of Cr carbides had no significant correlation with γ grain structure and orientation. Before and after stress relaxation experiments, microstructure, texture as well as the distribution of chromium carbide showed not change apparently, while γ′ phases were shown to coarsen. Under the same load, the experimental temperature influenced the stress relaxation behaviors, the higher temperature contributed to higher stress relaxation ratio, which could be related with easier dislocation slip. The phenomenon was consistent with more grains showing higher GOS(Grain Orientation Spread) values in the sample, while GOS value of individual grain did not show dependence on grain size and crystal orientation.
2022 Vol. 32 (7): 74-79 [
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Production Technology
80
FU Xu-gang, MA Ke, JU Jian-tao, XING Xiang-dong
Analysis on oxidative consolidation mechanism of manganese-containing magnetite pellets
In order to promote the application of manganese-containing magnetite in pellets, the effect of Mn
3
O
4
on the oxidative consolidation mechanism of pellets was systematically analyzed by means of pelletizing tests and detection methods such as X-ray diffraction and scanning electron microscopy. The results show that when the mass fraction of Mn
3
O
4
increases from 0% to 7%, the compressive strength of the pellets decreases from 2 458 N/piece to 1 810 N/piece, and the porosity increases from 22.7% to 26.2%. With the increase of Mn
3
O
4
, a new MnFe
2
O
4
solid solution is formed in the hematite grain boundary and silicate phase. The solid solution expands the cracks in matrix and destroys the continuous crystallization of hematite. The increase of silicate content greatly inhibits the growth of hematite grains, which makes the matrix of manganese-containing pellets change from dense to porous, and its strength of pellets decrease. Therefore, for production enterprises, Mn
3
O
4
has a negative impact on the consolidation and strengthening of pellets, and its appropriate mass fraction should be within 3%.
2022 Vol. 32 (7): 80-86 [
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87
ZHU Hong-xin, YANG Xin-long, WANG Ru-dong, YU Wei, CUI Heng
Analysis of inclusions in cast slab for high-strength engineering machinery steel
In order to understand the source of inclusions in Q550MD cast slab of high-strength engineering machinery steel in a plant, optimize the production process and improve slab quality, the number, size, morphology and composition of inclusions in the cast slab were studied by means of slime extraction, automated SEM-EDS inclusion analysis. The results show that the size of macro inclusions in slime extraction sample is concentrated in 80-140 μm. The shape of inclusion is mostly spherical, and the main component is calcium aluminate. Before forming the final composite inclusions, the macro inclusions in the cast slab come from the ladle, and the mold flux entrapment may occur. The inclusion aggregation is found at 1/4 position in the width direction of cast slab, and the number of inclusions is significantly higher than that at the edge and 1/2 position, which is related to the unreasonable flow field of the mold.
2022 Vol. 32 (7): 87-91 [
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92
CHANG Hai, LEI Shao-wu, QIU Jun-juan, GENG Ming-shan
Simulation analysis of slab
ø
230 mm support roller under periodic heat loading
Slab support roller is an important part of slab caster, the temperatures of the support roller at the bearing position and roller surface directly determine whether the support roller can operate normally. In order to find out the temperature distribution of each part of roller during the rotation, the heat transfer process of roller during the periodic rotation of slab
ø
230 mm support roller was simulated. The results show that the temperature of slab
ø
230 mm support roller reaches a steady state after 1 500 s of continuous casting under the influence of slab radiation, cold water and air heat dissipation. And the temperature of the roller projecting to the middle of semicircle on the air side under the influence of cooling water is about 250 ℃, while the temperature is about 270 ℃ without the influence of cooling water. Under the influence of cooling water, the maximum temperature of the roller projecting to the slab side semicircle is 272.3 ℃, while the temperature is about 290 ℃ without influence of cooling water. By comparing with the measured data, the results show that the calculation model can predict the temperature distribution of roller well and provide theoretical support for the design of continuous casting support roller.
2022 Vol. 32 (7): 92-97 [
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98
WANG Xiao-yong, WANG Hua-peng, JIA Xiao-lin, ZOU Yang, PIAO Xue-feng
Experimental study of roll composite for low-alloy ultra-heavy steel plate
In order to meet the market demand of low-alloy steel plate with large single weight and ultra-heavy specifications, the experimental study of ultra-heavy steel plate produced by composite continuous casting slab was carried out by the rolling composite process. Ultra-heavy steel plates were obtained through rolling from composite slab. The comprehensive test and analysis show that the interface bonding of ultra-heavy steel plate produced by rolling composite process is good, and metallurgical bonding at atomic level is achieved with the sufficient recrystallization of grain at the bonding interface. The
z
-direction tensile properties meet the requirements of Z35, but the local reduction of area is low due to the existence of band-distributed oxides at the bonding interface microregion.
2022 Vol. 32 (7): 98-102 [
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103
YAN Lei, SUN Jian-hua, SUN Yue, YU Yang, LI Shuo, WANG Lin
IF steel trimming quality improvement control technology
For the IF steel that has undergone continuous annealing or hot-dip galvanizing heat treatment, due to the poor quality of trimming, defects such as burrs are prone to occur on the edge of strip during the trimming process, which in turn affects the quality of strip edge. Through the research on the proportion of each area on cut surface of strip after trimming and the influence of trimming process parameters on the proportion of each area on the cut surface after trimming, the process parameters of disc shearing edge were optimized. The working principle of deburring roll and the causes of bright edge defects were studied, and the coating of deburring roll and the roll shape of bottom roll were optimized. After the optimization measures are taken, the trimming quality of the IF steel is improved and the bright edge defects are completely eliminated.
2022 Vol. 32 (7): 103-106 [
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Energy Saving and Environmental Protection
107
MENG Hua-dong, YANG Yong, YAO Tong-lu
Process test of recycling ladle hot casting residual slag in converter and KR
In order to achieve the purpose of energy saving and consumption reduction, the recycling process test of ladle hot casting residual slag was carried out in the converter and KR. The slag forming and metallurgical effects before and after the recycling of ladle hot casting residual slag in the converter and KR were compared and analyzed. The results showed that, without modification of the existing equipment, adding about 30 kg/t ladle hot casting residual slag in each conventional furnace could save 12 kg/t of iron and steel material, 4.31 kg/t of lime, 4.87 kg/t of sinter and 1.83 m
3
/t of oxygen, shortened the smelting time by 3.24 min for per furnace, saved the smelting cost of 39.43 yuan/t steel, reduced the end-point a[O] content, improved the end-point dephosphorization rate, and improved the molten steel quality and smelting efficiency, while reduced the cost of steelmaking. The environmental pollution caused by the discharge of ladle casting residual slag was also reduced, and the economic and social benefits were good. In order to reduce the influence of high sulfur content in ladle casting residual slag on converter metallurgical effect, the ladle hot casting residual slag could be recycled by returning to KR hot metal pretreatment, about 27 kg/t ladle hot casting residual slag was added to each hot metal tank, the amount of desulfurizer such as lime was reduced by 82.2%, the hot metal pretreatment time was shortened by 1 min, the temperature drop was reduced by 4 ℃, the rephosphorization rate was reduced by 2%, and the desulfurization rate was 69.4%, and good results were achieved.
2022 Vol. 32 (7): 107-113 [
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114
LIU Xiao-lin, DU Jian-min, HUANG Yan-jun, LIU Heng, SONG Guang-sen, ZHANG Lei
Removal of fine particles in converter primary flue gas by acoustic wave coupling swirl process
In view of characteristics of high dust concentration and fine particles in primary flue gas for converter in iron and steel plant, a new technology of acoustic wave coupling swirl dust removal was proposed to reduce the fine particle concentration in the primary flue gas of converter. The effects of sound pressure level, sound frequency, residence time and flue gas inlet mode on the reduction rate of particle concentration were studied by single factor test and response surface method. Single factor test results show that effect of acoustic agglomeration on primary flue gas particles is enhanced with the increase of sound pressure level, but there is an optimal agglomeration frequency. Compared with single acoustic agglomeration, acoustic wave coupling cyclone dust removal technology has better agglomeration effect on fine particles. The response surface method optimization test shows that when the sound pressure level is 140 dB, the sound frequency is 1 400 Hz and the residence time is 8 s, the particle concentration reduction rate is the highest, and the particle concentration reduction rate can reach 33% when swirl gas inlet mode is adopted. This study provides a reference for improving the removal efficiency of fine particles in primary flue gas for converter and process development.
2022 Vol. 32 (7): 114-121 [
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Non ferrous Metallurgy
122
LI Jiang-tao
Analysis of grinding flotation depleted recovery ratio of water quench slag from ISA copper smelting
In the process of copper recovery by grinding flotation and depleted of electric smelting slag, copper flotation recovery ratio has obvious difference due to different smelting methods, raw material structure, process operation control and cooling methods of electric smelting slag, so it is necessary to carry targeted study on the actual situation. The ISA copper melting of fast cold water quenching electric furnace slag in grinding flotation and depleted was taken as the research object, the main components, structure, mineral phase and particle morphology of ores and tailings were studied, combining with the production practice, and the directly objective influence of the copper slag minerals property on the copper recovery ratio was ascertained, providing visually scientific guidance for production operation to reduce process mistakes.
2022 Vol. 32 (7): 122-128 [
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Metallurgy Talent
129
2022 Vol. 32 (7): 129-129 [
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2022 Vol. 32 (7): 130-130 [
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Metallurgical Science and Technology Award
131
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