钢铁
Home
|
About Journal
|
Editorial Board
|
Instruction for Authors
|
Subscriptions
|
Advertisement
|
Contacts Us
|
Chinese
Office Online
Author Center
Peer Review
Editor Work
Office Work
Editor-in-chief
Journal Online
Forthcoming Articles
Current Issue
Archive
Read Articles
Download Articles
Email Alert
Quick Search
Advanced Search
2022 Vol. 57 No. 4
Published: 2022-04-15
Technical Reviews
Raw Material and Ironmaking
Steelmaking
Metal Forming
Materials
Environmental Protection and Energy
Technical Reviews
1
MA Guo-jun, LIU Meng-ke, ZHANG Xiang, ZHENG Ding-li, YAO Wang-long
Research progress on melting behavior of steel scrap in iron-carbon bath
It has become the goal of the world steel industry to gradually reduce the proportion of iron ore and increase the proportion of steel scrap so as to attain the steel recycling in the process of ferrous metallurgy. The melting behavior of steel scrap is the key factor that controls the temperature trajectory and scrap ratio of BOF, as well as the energy consumption and productivity of EAF. Simultaneously, the melting behavior of steel scrap in hot metal ladle may also affect the operation of hot metal pretreatment process. It is of great significance to study the melting behavior of steel scrap to improve the utilization rate of steel scrap in converter, electric arc furnace, hot metal ladle, and ensure the stability of ferrous metallurgical process. The previous researches are summarized in order to provide theoretical guidance and experimental basis for improving the utilization rate of steel scrap in actual smelting process. The research progress on the melting behavior of steel scrap in iron-carbon bath is reviewed, including the melting mechanism of steel scrap and the effects of bath temperature, bath carbon content, preheating temperature, size of steel scrap and gas stirring on the melting behavior of steel scrap. It involves the application of numerical calculation and simulation, thermal simulation and cold model investigation. The melting behavior of steel scrap mainly includes the formation and remelting of solidified layer, and the carburizing and melting of parent steel scrap. With the increase of bath temperature and bath carbon content, the decrease of steel scrap size, the melting rate of steel scrap increases gradually. The preheating temperature has little effect on the melting rate in the later stage. Improving the gas stirring conditions can increase the melting rate of steel scrap and shortens the mixing time of bath. Meanwhile, as the bath temperature and bath carbon content increasing, the specific surface area of steel scrap and the bath stirring intensity are both increased, the heat and mass transfer process between bath and steel scrap is enhanced, the heat transfer coefficient between melt and steel scrap and the mass transfer coefficient of carbon are increased.
2022 Vol. 57 (4): 1-11 [
Abstract
] (
288
) [
HTML
1KB] [
PDF
4142KB] (
528
)
Raw Material and Ironmaking
12
SHE Yuan, ZHAN Wen-long, ZOU Chong, HAN Peng, WU Keng
Kinetics of coke gasification reaction process by improved segmentation attempt method
As the main fuel of blast furnace ironmaking, coke plays a vital role in the normal operation of blast furnace and efficient smelting. With the development trend of large-scale intelligence of modern blast furnace and the continuous consumption of resources, the raw materials used to smelt high-quality metallurgical coke are gradually reduced. Low-quality metallurgical coke has attracted more and more attention of metallurgical workers. After determining the basic physical and chemical properties of coke in blast furnaces, the kinetics of different quality coke and CO
2
gasification reaction processes under different heating rates were studied using the segmentation attempt method. The control mechanism of coke gasification reaction process was studied, which could be divided into two stages, the chemical reaction rate control in the early stage and the diffusion mass transfer rate control in the later stage. A two-stage speed control model was used to fit the gasification reaction process data, and then an unreacted shrinking core model for the chemical reaction rate control in the early stage and a shrinking core model for the diffusion mass transfer rate control in the later stage were established respectively. The conversion points, chemical reaction rate constant and mass transfer coefficient of the two control rates in reaction process were determined. Considering that the chemical reaction rate was nearly three orders of magnitude higher than the diffusion control rate, according to the irreversible thermodynamic phenomenological equation, the interference effect of chemical reaction process on the internal diffusion rate control process in the later stage of gasification reaction process was studied, and the valence coefficient in the phenomenological equation was determined. The latter diffusion speed control equation was modified, segmentation attempt method which was suitable for metallurgical reaction engineering to study reaction process kinetics was improved and its accuracy was further increased.
2022 Vol. 57 (4): 12-24 [
Abstract
] (
236
) [
HTML
1KB] [
PDF
3225KB] (
341
)
25
HU Xin-guang, SHEN Feng-man, ZHENG Hai-yan, GUO Yong-chun, JIANG Xin, GAO Qiang-jian
Effect of temperature on Al
2
O
3
activity in CaO-SiO
2
-Al
2
O
3
-MgO blast furnace slag system
As one of the main components in slag, Al
2
O
3
has a particularly prominent impact on the metallurgical properties of slag. For blast furnace ironmaking, the increase of Al
2
O
3
in blast furnace slag will have an adverse impact on ironmaking and desulfurization. However, with the continuous development of China's iron and steel industry, the use of relatively low-cost high Al
2
O
3
imported iron ore is increasing, which makes the content of Al
2
O
3
in blast furnace slag significantly increase compared with the past. The mass percent of Al
2
O
3
in blast furnace slag often exceeds 15%, and even higher can reach more than 20%. At present, there are few reports on the thermodynamic properties of Al
2
O
3
components in high Al
2
O
3
blast furnace slag system (for example, the measurement of Al
2
O
3
activity by reference slag method) and their influence on the metallurgical properties of metallurgical slag, and temperature is one of the important thermodynamic factors affecting the metallurgical properties of metallurgical slag. Therefore, to explore the effect of temperature on the Al
2
O
3
activity in metallurgical slag not only has important academic research significance, but also provides a solid theoretical basis for field practice. Thus, the activity of Al
2
O
3
in CaO-SiO
2
-Al
2
O
3
-MgO blast furnace slag system at 1 773-1 873 K is measured by reference slag method, and the structure of slag is detected by Raman spectrum. The effect of temperature on Al
2
O
3
activity of CaO-SiO
2
-Al
2
O
3
-MgO blast furnace slag system was investigated. The results show that with the increase of temperature, the chemical potential of Al
2
O
3
in slag decreases, and the reaction between slag and Cu molten metal moves to the right to reach a new equilibrium. Therefore, the activity of Al
2
O
3
decreases gradually with the increase of temperature. With the increase of temperature, Al
2
O
3
in the slag reacts with alkaline metal oxides, increasing the formation of complexes such as calcium aluminate (CaO·Al
2
O
3
and CaO·2Al
2
O
3
) and magnesium aluminate (MgO·Al
2
O
3
). At this time, the structure of the slag gradually depolymerizes due to the increase of O
2-
, and the free Al
2
O
3
in the slag decreases, which cause the Al
2
O
3
activity decrease gradually.
2022 Vol. 57 (4): 25-33 [
Abstract
] (
157
) [
HTML
1KB] [
PDF
3635KB] (
588
)
34
WANG Yong-bin, PENG Jun, LUO Guo-ping, ZHANG Fang, AN Sheng-li
Effect of MgO, fluorine and alkali metals on mineral phase of pellets
Baiyun Obo ore pellets have abnormal reduction expansion due to the presence of more alkali metals and fluorine. The addition of MgO can effectively inhibit its reduction expansion and MgO is bound to affect the mineral phase composition of pellets. At present, more attention is paid no the influence of a single factor in magnesium oxide, fluorine and alkali metals on the phase of pellets, but the cooperated influence of the three factors on the phase of pellets is still lack of in-depth study. The effects of (K
2
O+Na
2
O), CaF
2
and MgO on the mineral phase composition of the hematite pellets were studied by orthogonal test, and their distribution in the hematite pellets was studied by mineral phase microscope, SEM-EDS, XRD and FactSage software. The results show that MgO has a significant effect on iron-containing minerals and pores of pellets, but has little effect on slag phase. The addition of magnesium oxide reduces the initial decomposition temperature of Fe
2
O
3
, and promotes the decomposition of hematite into magnetite. During the roasting process, Mg
2+
diffuses into the magnetite lattice to form magnesium-containing magnetite and stabilizes the structure of magnetite, so that most of the magnesium oxide enters the iron phase of the pellets. With the increase of MgO, the content of magnesium-containing magnetite increases rapidly, which leads to the increase of magnetite content in the pellets and improves the stability of the pellets. The formed magnetite is mostly located at the edge of original hematite matrix and is connected with the hematite. When the content of MgO increased from 1% to 5%, the magnetite content increased by 6.6%, the hematite content decreased by 15.4%, and the proportion of pores increased by 9.5%. The addition of (K
2
O+Na
2
O) all entered into the slag phase, which had a great influence on the slag phase of pellets. When the addition content of (K
2
O+Na
2
O) exceeded 0.2%, the dissolution amount of Fe
2
O
3
in the slag increased rapidly, which made the amount of liquid phase in the pellet increased. In the subsequent cooling process, the solidification of liquid phase led to the volume shrinkage of pellet, resulting in a decrease in the porosity of pellet. When the content of (K
2
O+Na
2
O) increased from 0.1% to 0.4%, the content of slag phase increased by 2.6% and the porosity decreased by 5.9%. The slag phase was mostly distributed among iron oxides without fixed shape. All of CaF
2
entered into the slag phase and had little effect on the mineral phase of pellets.
2022 Vol. 57 (4): 34-42 [
Abstract
] (
141
) [
HTML
1KB] [
PDF
5242KB] (
429
)
43
YANG Tao, LONG Hong-ming, DING Cheng-yi, LI Yong, CAO Fa-wei, HU Ming-yi
Effect of
w
(Al
2
O
3
)/
w
(SiO
2
) on sintered ore mineralization characteristics and metallurgical properties
Al
2
O
3
and SiO
2
are important components of composite calcium ferrite, and an appropriate ratio of alumina to silica is an important condition for obtaining good sintering ore-forming characteristics and metallurgical properties. Based on the on-site sintering raw material structure of a steel plant, the FactSage theory was used to calculate the change law of equilibrium phase composition and liquid phase composition for the sintering system. As the ratio of alumina to silica decreased from 0.41 to 0.34, the high-quality phases such as liquid phase and iron oxide in the sinter increased, the content of inferior phases such as spinel decreased, and the liquid phase precipitates and SFCA gradually increased. The experiment revealed the influence of different ratio for alumina to silica on the quality, phase composition, microstructure and metallurgical properties of sinters. The results showed that as the ratio of alumina to silica decreased from 0.41 to 0.34, the drum strength, yield and utilization factor of sinters improved significantly, from 58.27%, 60.24%, 1.585 t/(m
2
·h) to 61.73%, 71.87%, and 2.185 t/(m
2
·h), respectively. The mineral phase analysis shows that as the ratio of alumina to silica decreases, the content of calcium ferrite increases and gradually develops into acicular shape, while the content of hematite, magnetite and pores decreases, and the optimal phase composition is reached when the ratio of alumina to silica is 0.34. This result corroborates the change rule of sintered ore quality index. When the ratio of alumina to silica is 0.34, the metallurgical performance of sinter is improved compared with the benchmark sinter. The reduction degree and reduction degradation property index
RDI
>3.15 mm are increased from 73.11% and 72% to 77.47% and 80% respectively, the softening temperature range and the droplet temperature range are narrowed, the total characteristic value
S
of the droplet performance also has a downward trend, and the soft melting property of sinter is improved significantly. According to the theoretical calculation and test results, the optimization of ore blending is of great significance for improving the quality of sintered minerals and optimizing sintering process.
2022 Vol. 57 (4): 43-51 [
Abstract
] (
512
) [
HTML
1KB] [
PDF
3328KB] (
568
)
Steelmaking
52
WANG Ye-guang, LIU Cheng-jun, QIU Ji-yu
Effect of Al content on non-metallic inclusions in heat-resistant steel containing rare earth element
As a common alloying element in high-quality steel, rare earth is widely used to improve the properties of steel. However, due to the strong affinity between rare earth and impurity elements such as oxygen and sulfur in steel, the formation of inclusions with high melting point and large size after rare earth addition are seriously harmful to casting process and product quality. In order to investigate the effect of different Al contents on the type and size distribution of non-metallic inclusions in heat resistant steel containing rare earth, high temperature experiments were designed and carried out according to calculation by optimized thermodynamic model. The results of calculation show that increase of Al content can inhibit the precipitation of Ce
2
O
3
inclusions, but promote the precipitation of CeAlO
3
and Ce
2
O
2
S inclusions in steel. The changes of Ce, Al, O and S in molten steel were calculated, and thereby obtaining the critical thermodynamic conditions of inclusion transformation. When
w
([Al]) was 0.025%-0.065%, and the
w
([Al])/
w
([Ce]) value was 270, Ce
2
O
3
transformed into CeAlO
3
. Ce
2
O
3
converted to Ce
2
O
2
S with Al content ranging from 0.065% to 0.17% and
w
([S])/
w
([O]) value up to 10. The experiment results show that inclusions variation trend is Ce
2
O
3
→Ce
2
O
3
+CeAlO
3
→CeAlO
3
+Ce
2
O
2
S with the increase of mass percent of Al from 0 to 0.3% under a certain Ce amount in different test steels, and the average particle size of inclusions reduces from 4.69 μm to 2.73 μm accordingly. Based on the statistical results of relationship between inclusion type and size distribution, it is found that the formation of Ce
2
O
2
S with small size is one of the main cause for decrease of inclusions size. Therefore, increase of Al contents in rare earth heat-resistant steel appropriately can effectively refine the size of inclusions in steel by modifying the inclusion types, which is expected to improve the nozzle clogging problem and the product quality.
2022 Vol. 57 (4): 52-57 [
Abstract
] (
167
) [
HTML
1KB] [
PDF
2819KB] (
458
)
58
LI Bo, YANG Ling-zhi, SONG Jing-ling, GUO Yu-feng, LI Zhi-hui
Application on one-key alloy feeding optimization system for steelmaking process of 90 t EAF
EAF steelmaking process is the important process on steel industry transformation path, as the standard of special steel components increasing, the higher requirement of composition control for EAF steelmaking in iron and steel enterprises has put forward, and alloy feeding EAF steelmaking process is one of the important means for regulating composition. Because of alloy type and quality needed in different steel grades during smelting are different and the price of alloy is not average, therefore, alloy cost is always been an important part of the production cost of EAF steelmaking. At present, the alloy feeding operation process of 90 t EAF steelmaking process in Hengyang Hualing Steel Tube Co., Ltd., relies on the experienced technical staff, and does not fully consider the difference of alloy element yield for different steels. The fluctuation of price and composition of alloy raw materials in different batches results in less control of narrow composition, more frequency of alloy feeding and high alloy cost. In order to solve this problem,based on the dynamic database of alloy element yield rate and the two-stage simplex algorithm, the influencing factors of alloy feeding process were analyzed in the article. Using SQL database, Visual Studio 2013 development platform and OPC interface technology, the alloy feeding optimization system with one-key operation was developed. The calculation results of the system were transmitted to PLC to realize the one-key alloy feeding operation. The system operation results show that the alloy element yield rates of different steels are optimized. The alloy allocation ratio in the ladle after EAF tapping increased from about 73.88% to 85.11%, compared with the whole steelmaking process. The system calculation cost of alloy feeding in ladle after EAF tapping reduced 6.32%-8.07% and the system calculation cost of alloy feeding in LF reduced 1.04%-22.59%. The total cost of EAF steelmaking process decreased by 1.53%-10.02%.
2022 Vol. 57 (4): 58-67 [
Abstract
] (
179
) [
HTML
1KB] [
PDF
3808KB] (
382
)
68
ZHOU Qiu-yue, ZHU Tan-hua, ZHANG Li-feng, CHEN Wei, YUAN Tian-xiang, LIU Zhen-tong
Large eddy simulation on quantitative influence of unsteady casting on mold slag entrainment
A three-dimensional numerical model coupled with the large eddy simulation (LES) turbulence model and VOF multiphase model, was established based on an actual slab continuous casting mold to investigate the influence of clogging degree and misalignment distribution of submerged entry nozzle (SEN) on the transient multiphase flow field and slag entrainment. The quantitative prediction of number, size, and spatial distribution of the entrained slag droplet in the mold under different conditions were successfully realized using a user defined function,and the distribution of the probability of the slag entrainment at the meniscus was proposed. The results indicate that under the misalignment distribution of the SEN rotating 5° clockwise, the liquid steel jet hit the wide surface more, resulting in a slight decrease in the liquid level distribution near the narrow surface of the meniscus, and the liquid level fluctuation also decreases from the ±(6-7) mm to within ±5 mm compared with the normal conditions. The SEN clogging had a significant effect on the liquid level fluctuation. The liquid level fluctuation was increased to about ±11 mm when the SEN was completely clogging on the left side-without clogging on the right side, and the liquid level fluctuation was increased to ±15 mm when the SEN was 2/3 clogging on the left side-1/3 clogging on the right side. With the normal conditions, the net slag entrainment rate was 0.0130 kg/s and the slag entrainment was mainly occurred around the meniscus and where the stream collides. The net slag entrainment rate was slightly decreased to 0.009 3 kg/s and the probability of slag entrapment near the wide surface was increased under the SEN misalignment condition. The net slag entrainment rate was increased to 0.045 5 kg/s and 0.067 kg/s respectively when the SEN was completely clogging on the left side-without clogging on the right side and 2/3 clogging on the left side-1/3 clogging on the right side. The slag entrainment rate was mainly caused by the shearing effect of the excessive flow velocity of molten steel on the meniscus. The slag entrainment was mainly located within the range of the SEN to 1/4 the width of the mold. The vortex caused by the asymmetric flow was increased after the SEN was clogged, and the slag entrainment also increased accordingly.
2022 Vol. 57 (4): 68-78 [
Abstract
] (
319
) [
HTML
1KB] [
PDF
8564KB] (
480
)
Metal Forming
79
ZHANG Jian-lei, ZHANG Jie, QIN Song, LU Jia-dong, YUE Chong-xiang
Research and application of backup roll profile optimization for hot rolled thin strip temper rolling mill
The roll length of a hot rolled thin strip temper rolling mill is 1 800 mm and the strip length is 1 320 mm. The difference between the two is too large, which results in the too large length of harmful contact area between work roll and backup roll. Under the action of roll bending, the peak stress is concentrated at the strip edge. With the extension of rolling kilometers, the edge wear of work roll intensifies, which is not conducive to the later shape control and shorten the life of roll. In view of work roll uneven wear problem for hot rolled thin strip temper rolling mill, the backup roll profile curve was designed. Through the chamfer design at both sides of the backup roll, the length of harmful contact area between the work roll and the backup roll was reduced. With the help of numerical simulation, a three-dimensional elastic-plastic finite element model of temper rolling mill was established to simulate the roll usage under different temper rolling processes and roll profile parameters. It was compared and analyzed from four evaluation indexes, shape control efficiency, crown adjustment region, lateral stiffness of bearing roll gap and contact stress of work roll. The simulation results show that three roll profile improves the stress distribution uniformity of the work roll, helps to improve the service cycle of the roll. The length of harmful contact area between rollers is significantly reduced. The regulation efficiency of bending roll force is increased from 0.048 μm/kN to 0.130 μm/kN. Considering the risk of the strip running deviation, if the chamfer insertion of the backup roll is too large, the chamfer of the backup roll is easy to jump into the strip steel, resulting in edge tension or even belt breakage. Therefore, the V + 25 roll profile with the smallest chamfer insertion amount was selected and applied to the site commissioning. The field data show that flatness control ability of the temper rolling mill is significantly increased, and the roll tonnage per unit rolling cycle is significantly increased. The average life of work roll is increased from 1 500 t to 1 800 t, and the product qualification rate is increased from 95% to more than 98%.
2022 Vol. 57 (4): 79-87 [
Abstract
] (
213
) [
HTML
1KB] [
PDF
4419KB] (
441
)
Materials
88
SU Xue, WANG Hou-xin, ZHU Min, ZHANG Qi, TIAN Jun-yu, XU Guang
In-situ observation for effect of niobium on pearlite transformation in high-carbon steels
In order to investigate the effect of niobium (Nb) on pearlite transformation, the dynamic nucleation and growth process of pearlite in high-carbon steels with and without Nb during continuous cooling was observed by in situ observation under laser scanning confocal microscope (LSCM). The results show that Nb addition increases the nucleation density of pearlite, which increases the number of nucleation sites. Besides, the addition of Nb significantly decreases the growth rate of pearlite due to the hindrance in growth of pearlite in high-carbon steels. However, the hindering effect does not further increase when mass percent of Nb exceeds 0.014%. It is known from above results that Nb addition promotes the nucleation but significantly hinders the growth of pearlite in high-carbon steels. Hence, two kinds of high carbon steel without and with mass percent of Nb of 0.027% were selected to perform thermal expansion experiments on Gleeble-3500 thermal simulation test machine in order to study the effect of Nb on pearlite phase transformation more accurately. The thermal expansion experiment shows that addition of Nb increases the degree of undercooling, leading to the reduction of pearlite transformation temperature range, but significantly hinders the diffusion of carbon in austenite, so the pearlite growth rate is decreased. Additionally, Nb reduces pearlite phase transition rate and delays pearlite transformation because it slows down the pearlite transformation kinetics under the continuous cooling condition, indicating that the inhibition effect of Nb on growth is stronger than its promotion effect on nucleation of pearlite. Therefore, the addition of Nb postpones pearlite phase transition in high carbon steel. Moreover, the addition of Nb increases the degree of undercooling, refines pearlite lamellas and improves the hardness of high-carbon steels, but when mass percent of Nb exceeds 0.014%, there is no further refinement effect.
2022 Vol. 57 (4): 88-96 [
Abstract
] (
196
) [
HTML
1KB] [
PDF
4860KB] (
444
)
97
ZOU Ying, LIU Hua-sai, HAN Yun, QIU Mu-sheng, YANG Feng
Microstructure evolution and mechanical properties of medium manganese steel based on annealing path
In order to guide the industrial trial production of medium manganese steel better, the microstructure evolution and alloy element distribution behavior of low carbon medium manganese steel under different annealing paths were studied by scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM) and tensile testing machine. Moreover, its effect on mechanical properties was evaluated. The results show that the microstructure of hot rolled medium manganese steel is mainly composed of ferrite, lath martensite, granular bainite and retained austenite. After cold rolling, the ferrite and martensite grains were broken, and the retained austenite and M/A island were transformed into martensite under strain induced transformation. The microstructure of medium manganese steel under two different annealing paths both consisted of ferrite, retained austenite and a small amount of secondary martensite. The microstructure of one-step annealing process was polygonal and that of two-step annealing process was lath-like. In one-step annealing process, the area fraction, average equivalent grain diameter and Mn content of retained austenite were 25.6%, 0.32 μm and 6.36%, respectively, and that of two-step annealing process were 27.8%, 0.38 μm and 5.37%, respectively. The increase of grain size and decrease of Mn enrichment degree leaded to lower mechanical stability of retained austenite in two-step annealing process. The yield strength of medium manganese steel under two annealing processes was almost the same, but the yield type was obviously different. There was a yield platform with about 4% elongation on the stress-strain curve of one-step annealing process, while the two-step annealing process improved the work hardening and tensile strength at the initial stage of deformation, which eliminated the yield platform. However, in comparison to the one-step annealing process, the ductility loss of medium manganese steel was obvious under the two-step annealing process, and the uniform elongation and total elongation decreased by 4.6 and 6 percentage points, respectively.
2022 Vol. 57 (4): 97-104 [
Abstract
] (
149
) [
HTML
1KB] [
PDF
4058KB] (
512
)
105
HAO Shuo, LI Zhi-guo, ZHANG Xin, SHE Jun-feng, LIU Zhi-lei, CHEN lei
Influence of pre-strain on tensile deformation behavior of TRIP-assisted duplex stainless steel
Pre-deformation, as a key pretreatment process for serving, is usually used to improve the mechanical properties of metal components. In order to clarify the effect of pre-strain on the mechanical behavior and transformation behavior, a series of quasi-static tensile tests were carried out on INSTRON 8801 to investigate the tensile deformation behavior of a TRIP-assisted duplex stainless steel(DSS) and its dependence on pre-strain. The micro-mechanism was discussed by means of TEM analysis, EBSD analysis and in-situ magnetic measurement. The results showed that a typical “three-stage” hardening characteristic of TRIP-assisted DSS was reflected due to the occurrence of strain-induced martensite transformation (SIMT) of γ→ε→α' during tensile deformation, therefore enhanced work hardening ability and mechanical properties were obtained. The introduction of pre-deformation (unloading) did not change the nucleation and growth mechanism of α' martensite, but influenced the work hardening behavior and the mechanical properties of test steel by changing the martensite transformation kinetics in the subsequent deformation process. With the increase of pre-strain level, the (subsequent) yield stress increased and the elongation
A
decreased gradually. However, different changing trends were revealed in ultimate tensile strength and total elongation
A
t
(
A
t
=
ε
E
pre
+
A
) with increasing pre-strain level, which was closely related to the difference of martensitic transformation kinetics (i.e. transformation degree and transformation rate) under different deformation conditions.
2022 Vol. 57 (4): 105-113 [
Abstract
] (
159
) [
HTML
1KB] [
PDF
4389KB] (
349
)
114
HU Yong, WANG Li-hua, LIN Hong-ze, OUYANG Ming-hui, CHU Cheng, HU Yong-qi
Segregation and homogenization treatment of 5%Si high silicon austenitic stainless steel
High-silicon austenitic stainless steel has excellent high-temperature corrosion resistance properties and low cost due to the addition of high content silicon,and it has potential application value in the acid industry. However, the addition of high content Si will promote the redistribution of solute during solidification process, which will cause significant element segregation,and ultimately lead to the formation of dendritic structure and numerous harmful phases in the alloy. Homogenizing the ingot structure can effectively eliminate dendrites and element segregation,promote precipitation phase re-dissolution and dendrite ablation,thereby improving the thermoplasticity of material,and effectively coping with the problems of thermal deformation and cracking. Therefore,the work studied the microstructure and element distribution of 5%Si high-silicon austenitic stainless steel ingots prepared under laboratory conditions through metallographic microscope (OM), scanning electron microscope/energy spectrum analysis (SEM/EDS), Electronic probe (EPMA), JMatPro software calculation and other methods. Finally,a reasonable homogenization treatment process for 5%Si high-silicon austenitic stainless steel was confirmed using the calculation of residual segregation index and diffusion kinetics,combined with homogenization treatment experiments. The results show that Mo is the most serious segregation element during the solidification of 5%Si high-silicon austenitic stainless steel,the homogenization kinetic equation calculated by residual segregation index model can be used to guide the homogenization treatment process of this alloy. After homogenizing at 1 150 ℃×12 h,the dendrites in 5%Si high-silicon austenitic stainless steel ingot are ablated and element segregation is eliminated,the precipitated phase and ferrite are re-dissolved into the matrix,the alloy is transformed into full austenite structure and thermoplasticity is improved. When the temperature is increased to 1 250 ℃,the alloy is overheated and grain boundaries begin to melt.
2022 Vol. 57 (4): 114-122 [
Abstract
] (
140
) [
HTML
1KB] [
PDF
3847KB] (
396
)
123
ZHANG Wei, PAN Yue, LIU Hua-sai, LI Chun-guang, CHEN Hong-sheng
Effect of strain rate on properties of dual phase steel with high formability
The microstructure of dual phase steel with high formability increases retained austenite compared with traditional dual phase steel, which shows a certain TRIP effect and better formability, so it is widely used for safety structural parts of vehicle body with complex shape. In order to study the effect of strain rate on the mechanical characteristics and microstructure changes of dual phase steel with high formability HC440/780DHD+Z, the strain rate properties of 7 different strain rates of 0.001, 0.1, 1, 10, 100, 200 and 500 s
-1
were tested universal testing machine and hydraulic servo high-speed tensile testing equipment to obtain the variation laws of strength, elongation and plastic product. The fracture morphology of the sample under different strain rates was observed and analyzed, and the variation law of dimple morphology and size affected by strain rate was obtained. The content of retained austenite at the fracture of samples with different strain rates was measured quantitatively, and the relationship between retained austenite and strain rate was obtained. Based on the above analysis, the effects of strain rate on material properties and microstructure were analyzed. The results show that, HC440/780DHD+Z has a certain strain rate sensitivity. The strength, elongation after fracture and strong plastic product of the material show positive strain rate sensitivity, which increases with the increase of strain rate. With the increase of strain rate, the dimple size of the material increases obviously, and the energy absorption ability of the material also increases gradually. Due to the transformation of retained austenite, plastic strengthening occurs in the deformation area, which promotes the deformation of other areas, and then increases the deformation uniformity in the process of plastic deformation, so that the material has better elongation. Therefore, with the increase of strain rate, the transformation amount of retained austenite increases, and the material shows better ductility.
2022 Vol. 57 (4): 123-129 [
Abstract
] (
138
) [
HTML
1KB] [
PDF
3669KB] (
433
)
Environmental Protection and Energy
130
SHE Xue-feng, LIU Song-hao, WANG Yan-jiang, WANG Jian-fang, WANG Jing-song, XUE Qing-guo
Effect of thermal modification on desulfurization capacity of column activated carbon
Five kinds of modified activated carbons (AC-1 to AC-5) were obtained by thermal modification of columnar activated carbons at different temperatures under the protection of N
2
. The activated carbons (AC) before and after modification were placed in the condition containing SO
2
and in the presence of water vapor and oxygen respectively for desulfurization experiment. The physical properties of activated carbon surface before and after modification were characterized by gas adsorption apparatus and scanning electron microscope. The experimental results show that when the modification temperature is 700-900 ℃, the desulfurization ability of the modified activated carbon increases with the increase of the modification temperature, when the modification temperature is 900 ℃, the desulfurization ability of the activated carbon is the strongest, when the modification temperature is 1 100 ℃, the desulfurization ability of the activated carbon decreases obviously. Gas adsorption apparatus of the proceeds of the BET the results of the analysis, and scanning electron microscopy the results show that activated carbon part was blocked in the process of heating channel is opened, increase its adsorption surface area, to improve the initial activated carbon desulfurization rate is good, but too high temperature will destroy the original structure of aperture, activated carbon in AC-4 and AC-5 samples of the desulfurization ability becomes poor. In addition, temperature-programmed desorption technology (TPD) was used to analyze the pH content of activated carbon samples from AC to AC-4. The results showed that there was a good proportional linear relationship between the ph content of strong alkali center on the surface of activated carbon and its desulfurization ability. By comparing the samples AC-2 and AC-3, it can be found that under the condition of little difference in the physical properties of activated carbon, the improvement of its desulfurization ability mainly benefits from the change of surface chemical properties, especially the enhancement of alkalinity. At the same time, through the Boehm titration and combined with Fourier transform infrared spectrometer (FTIR) of activated carbon samples AC and AC-3 the surface acidic functional groups of change were analyzed, and found that the thermal modified activated carbon surface carboxyl, lactone and decrease in the number of hydroxyl groups, shows that heat treatment can make the surface acidic functional groups of activated carbon decomposition, is helpful to promote its desulfurization ability.
2022 Vol. 57 (4): 130-137 [
Abstract
] (
134
) [
HTML
1KB] [
PDF
2097KB] (
735
)
138
CHAI Xi-cui, YUE Qiang, ZHANG Yu-jie, WANG Qi
Numerical simulation analysis of reduction domain in hydrogen metallurgy shaft furnace
Iron and steel industry is important basic industry for China's national economic development. Under the background of "carbon peak and carbon neutralization", low-carbon production has become a new competitiveness of iron and steel industry. The increasing environmental awareness calls for the development of innovative technologies. Hydrogen metallurgy is recognized as the cleanest and the most environment friendly metallurgical technology in the world, and clean and renewable energy are used in the iron-making process. The use of H
2
can reduce the greenhouse gas emissions caused by the iron-making process and reduce the emissions brought by carbon reductants from the source. Numerical simulation of hydrogen metallurgy shaft furnace is an important method to study the internal characteristics of iron and steel metallurgical process, which can provide an effective strategy for smooth operation. The purpose is to set reasonable furnace type parameters and reduction conditions of hydrogen direct reduction reactor. According to the rule of countercurrent reduction shaft furnace and the principle of safe, reliable, stable running, high efficiency and energy saving, this paper gave full play to the advantages of H
2
reduction, using existing shaft furnace design and production experience, carried out numerical simulation analysis on the reduction domain of hydrogen metallurgy shaft furnace with the help of Ansys, and which focused on the technological advantages of pure hydrogen in high temperature reduction conditions. The results show that the contants of gaseous reactants decreases while the contants of gaseous products increases when the reduction reaction goes along the hydrogen reduction shaft furnace. At the same time, the reduction reaction is mainly concentrated in the middle and lower part of the reduction domain, that is, 0.5-2.0 m height. Reasonable setting of reduction conditions and parameters of reduction domain can significantly improve the reduction degree of the whole process, slow down the consumption of raw materials, and achieve optimal efficiency, so as to provide reasonable suggestions for the long-term transition to all-hydrogen shaft furnace combined with the trend of low-cost renewable energy, support hydrogen metallurgy industrialize application as soon as possible, and provide theoretical support for hydrogen metallurgy industrial design.
2022 Vol. 57 (4): 138-147 [
Abstract
] (
392
) [
HTML
1KB] [
PDF
2940KB] (
624
)
148
SUN Man-li, ZHANG Min, WANG Jian, HAN Wen-tao, CHEN Fan
Discussion on process route for full-dry fine desulfurization of blast furnace gas
Regarding the characteristics of sulfide in blast furnace gas, big gas output and numerous scattered downstream users, the present situation of gas fine desulfurization were studied. By controlling from source, the fine desulfurization technology route of “pretreatment +catalytic hydrolysis + dry desulphurization” was proposed. According to the actual working conditions, the pretreatment and hydrolysis system could be placed before or after the top gas pressure recovery turbine unit. The route was adopting full-dry processing unit, which could ensure the calorific value, reduce the pressure of end of pipe control and achieve ultra-low emissions. The pretreating section could effectively avoid the influence of acidic gases such as hydrogen chloride on the back-end process. Taking the form of setting the process route after the top gas pressure recovery turbine for example, the integrated experimental system was set up to study the influence of various factors on system efficiency, including setting of pretreatment system, temperature, water content, oxygen content, etc. The experimental results showed that the pretreatment system could effectively remove acidic gases, such as hydrogen chloride, prolong the service life of hydrolytic agent and avoid corrosion of back-end pipes and equipment. Setting fine desulfurization system after TRT, there existed a better temperature range 70-90 ℃, and an optimal reaction temperature 80 ℃, resulting in a stable total sulfur removal rate over 95%, when reaction temperature varied from 40-120 ℃. The experimental results also indicated that the hydrolysis efficiency could achieve higher than 96%, when the volume ratio of H
2
O/COS was 6. It was not conductive to the hydrolysis when the ratio was too high or too low. When the molar ratio of O
2
/H
2
S was greater than 3, the desulfurization and regeneration could take place simultaneously, and no extra operation was required. The experiments prove that the route of “pretreatment +catalytic hydrolysis + dry desulphurization” which can meet the requirements of different working conditions and effectively reduce the sulfur content is a simple and efficient new process for fine desulfurization of blast furnace gas.
2022 Vol. 57 (4): 148-157 [
Abstract
] (
199
) [
HTML
1KB] [
PDF
2889KB] (
437
)
钢铁
News
·
·
·
·
·
More
Author Center
Instruction for Authors
Template
Copyright Agreement
Links
·
Links
More
Copyright © IRON AND STEEL
Supported by: Beijing Magtech
