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2018 Vol. 53 No. 4
Published: 2018-04-15
1
LIU Liu
Key production-technology for high-quality special steels
The new developing tendency of special steels in the world during the 21st century was briefly introduced with the bearing steel as the typical example. The disparity and problems between domestic and oversea production of bearing steels were analyzed. The developing status and research achievements in steel-making technologies for high-quality special-steels were emphatically introduced， including high-carbon dephosphorization for low oxygen steel in converter， refining process with lower reduction-potential in ladle-furnace， origin and control of large-size inclusions， ultra-low-Ti steel technology and the convex-roll reduction at the solidification end of large-size bloom-casting.
2018 Vol. 53 (4): 1-7 [
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ZHU Li，，SHE Yuan，，ZHAN Wen-long，WU Keng，YUCHI He-peng，LIU Guo-you
Practice for effect of coke high temperature properties on coke burden in blast furnace
In order to get a lower fuel ratio and BF smooth operation after the use of high performance coke， the relationship between the high temperature performance of coke and coke burden was studied. The high temperature performance of coke has an important influence on BF coke burden. Since the medium-capital overhaul of Shouqin No.1 BF， several suitable blast parameters have been chosen according to the blast system and operation profile with high-quality CDQ. Through the strengthen management of raw materials and BF tapping， and reasonable regulation of the upper and lower gas distribution， the operation of high coke burden was achieved under the condition of economic burden. Under the pressure of limiting production， the tuyere area was reduced by 11.38% . Meanwhile， reasonable blast parameters were adopted to lengthen the raceway depth and maintain the stability of the hearth. Moreover， the narrow and strong central gas distribution with a stable edge temperature formed. Production practice shows that under the condition of an average slag ratio up to 433.30 kg/t， the coke burden is improved to 6.01 t·t－1 with the average fuel ratio 499.17 kg/t. It is proved that the fuel consumption could be reduced effectively by the use of high-quality coke.
2018 Vol. 53 (4): 8-14 [
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15
ZHOU Ming-shun，TANG Fu-ping，ZHAO Dong-ming，YANG Xi-peng，WANG Jun-shan，LI Jian-jun
Investigation on MgO-flux and a new bentonite in pellets production
In order to ensure appropriate[w(MgO)]of blast furnace slag， MgO-fluxed pellets are used to replace the MgO in sinter. A new type of pelletizing binder（new bentonite） and MgO flux were tested and their effects on the pelletizing process and metallurgical properties of pellets were investigated. The experimental results show that the drop strength of green pellets increases with addition of one kind of additives， and no cracking occurrs at 350 ℃.With the substitution of the new bentonite for the existing binder， the Fe grade of pellets increases slightly due to its lower[w(SiO2).]The RDI and RSI of MgO-fluxed pellets are also improved slightly. Finally， the softening temperature of the MgO-fluxed pellets increases， which can lower the cohesive zone and improve its movement smoothly and permeability of the blast furnace. Based on mass percent calculation， when[w(MgO)]in the sinter is 1.2%，the[w(MgO)]in pellets should be about 1.90% to keep the overall[w(MgO)]of the feed materials unchanged.
2018 Vol. 53 (4): 15-19 [
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20
LI Feng-guang，QI Cheng-lin，WANG Yu
Influence of FeO on softening-melting properties of primary slag under different slag basicity
The softening-melting properties of primary slag in BF has an great influence on the adherent dross capability of the copper cooling staves， which may affect the smooth operation in BOF and production safety. The composition ranges of the primary slag were confirmed by anatomy result of the blast furnace， and then the influence of varying[w(FeO)]on the softening-melting properties of primary slag made up by prue regents was investigated. The results show that softening-melting properties of primary slag is influenced tremendously by[w(FeO)]regardless of slag basicity. The softening-melting temperature of primary slag decreases when the[w(FeO)]increases. When the slag basicity of primary slag is 1.3， the primary slag has the lowest softening-melting temperature. Either higher or lower slag basicity is harmful to the stability of slag coating.
2018 Vol. 53 (4): 20-26 [
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27
LU Hai-biao，CHENG Chang-gui，LI Yang，YANG Ming-lei，JIN Yan
Distribution of argon bubble and fluctuation behavior ofsteel/slag interface in continuous casting mold
A physical model of the mold with a similarity ratio of 1[∶]0.6 and a mathematical model were built，and the effects of the process parameters on the bubble distribution in mold and the fluctuation at the steel-slag interface were studied by means of the high speed camera and analysis software in water model，and the discrete phase （DPM） model and volume of fluid （VOF） model in mathematical model. The results show that the bubble distribution in the mold calculated by the mathematical model is similar to that measured by the water model simulation. The size of argon bubbles in the mold grows gradually with the increase of argon flow rate，and the distribution of argon bubbles becomes more uniform in the mold. The argon blowing helps to reduce the wave height of the molten steel near the mold narrow face，but it will aggravate the fluctuation near the submerged entry nozzle. With the increase of the casting speed，the size of the argon bubbles in the mold decreases，the distribution in mold becomes more uniform，the wave height near the mold narrow face increases，and the wave height near the submerged entry nozzle decreases observably. The increased port angle and submergence depth of the submerged entry nozzle can help to inhibit the fluctuation of liquid steel near the nozzle and narrow face in mold，and the bubble distribution in the mold becomes relatively uniform，while the size of the argon bubble changes little. When the casting speed is 1.2 m/min，the port angle of submerged entry nozzle is 15°，and the submergence depth of the submerged entry nozzle is 160 mm，the preferable flow rate of argon is 4 L/min. The results can work as the theoretical basis for optimizing the process parameters, preventing the slag entrapment and improving the steel quality.
2018 Vol. 53 (4): 27-36 [
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37
TANG De-chi ，ZHANG Hong-yan ，JI Li-peng， XIAO Bao-liang ，ZHANG Da-wei ，ZENG Zhi
Cleanliness of calcium-treated wheel steel
Calcium treatment to the cleanliness of wheel steel was studied， Wheel steel produced through the process of BOF， LF refining treatment， RH refining treatment， calcium treatment and continuous casting was sampled systematically. The morphology， size and composition of inclusions were analyzed by scanning electron microscopy （SEM） equipped with energy dispersive X-ray spectrometer （EDS）. The results show that the composition of inclusions are Al2O3-CaO with a small amount of MgO and SiO2 before calcium treatment. The size of these inclusions is within 5 μm. After calcium treatment， the inclusions are mainly Al2O3-CaO-CaS， with the morphology of discontinuous clusters in the coil. Some of these inclusions are larger than 10 μm. The number density of inclusions with the size of 1 to 5 μm deceases from 10 to 3.1 /mm2 from RH， tundish to hot rolling. The number density of inclusions ranging from 5 to 10 μm in size is less than 1 /mm2. The number density of inclusions larger than 10 μm is less than 0.2 /mm2. The[w(T[O])]of slab is less than 0.001 0%. The element mapping analysis of inclusions shows that the inclusions in coil are mainly CaS-CaO-Al2O3 and CaO- Al2O3-MgO. The change in the morphology of inclusions in the rolling process is analyzed. The deformed inclusions after the rolling are CaO-Al2O3， while The non-deformable inclusions are CaO-Al2O3 wrapped with CaS.
2018 Vol. 53 (4): 37-41 [
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42
YU Chao，WU Zong-he，GUO Zi-xuan，ZHENG Xue-feng，XIE Hong-biao，XIAO Hong
Microstructure and properties of hot-rolled bonded titanium clade steel plate
In order to study the effect of bonding temperature and reduction ratio on properties of titanium clad steel plate，TA2/Q235B composite plate was prepared by hot-rolled bonding in a vacuum. The microstructural properties of the composite plate were investigated by scanning electron microscopy and energy dispersive spectrometer. The results show that when the bonding temperature was between 850 and 1 050 ℃，the thickness of ferrite region near the carbon steel side of the composite interface increased with the bonding temperature. And the increase of the compound on the composite interface made the shear strength reduced. The large reduction ratio is conducive to improve the bonding strength. When the bonding temperature were 850 and 950 ℃，the reduction ratio was 58%，and the rolling temperature was 1 050 ℃，the reduction ratio was 70%，the shear strength of the bonding surface reached the 0 types titanium clad steel plate standard in national standards.
2018 Vol. 53 (4): 42-47 [
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48
ZHANG Chao，，SU Jie，LIANG Jian-xiong，LIU Zhen-bao，GE Qi-lu
Research development of precipitation behavior of ultra high strength stainless steels
Ultra high strength（UHS） stainless steels have been widely demanded because of high strength，good toughness and excellent corrosion resistant. Precipitation hardening plays an important role in possessing high strength of the steels，but the complex precipitation process and unclear mechanism are the key factors to limit the exploitation of new UHS stainless steels. The classifications，marks，compositions and mechanical properties of UHS stainless steels were introduced. The evolution of precipitations and reinforcement mechanism research of martensitic UHS stainless steels were summarized. The significant directions of development of UHS stainless steels as computational materials science，strengthening theory and resource saving technology were pointed out.
2018 Vol. 53 (4): 48-61 [
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WANG Zhuang-fei，SHI Ming-hao，CHEN Jun，TANG Shuai，WANG Guo-dong
Static recrystallization behaviors in V and Nb-V microalloyed steels
The recrystallization regularities of V and Nb-V microalloyed steels have been studied with the MMS-300 hot simulation tester. The softening ratio curves caused by recrystallization were drawn. The static recrystallization activation energies of tested steels were estimated and the models of static recrystallization dynamic were established. The influence of Nb on the static recrystallization behaviors of V microalloyed steel was investigated with the observation of precipitates in the microstructure. The results show that， The static recrystallization activation energy of Nb-V microalloyed steel is significantly higher than that of V microalloyed steel. Under the conditions of deformed at 800 to 950 ℃ and kept for more than 60 s，the strain-induced precipitation occurs in Nb-V microalloyed steel. The tiny carbonitride is dispersed and distributed on dislocation lines and grain boundary. It leads to platform can be observed on the softening ratio curves of Nb-V microalloyed steel. All above these can indicate that Nb can not only present the occurrence of static recrystallization，but also obstruct the continuance of softening behavior.
2018 Vol. 53 (4): 62-66 [
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67
YANG Yong，ZHANG Xi-dong，YAO Tong-lu，WU Wei，LIU Liu
Experiment on preparation of vanadium nitrogen alloy by carbothermal reduction and nitriding
Vanadium nitride alloy was prepared by using industrial V2O5 powder，graphite electrode powder and binder in 100 kW medium frequency induction furnace. According to the different temperature and time，the temperature system is divided into four stages，that is，1 150-1 250 ℃；1 280-1 300 ℃；1 400 ℃；1 450 ℃. The effects of temperature，carbon allocation，size of raw material and addition of iron oxide on the end composition were investigated. The results show that high temperature is beneficial to the reduction of V2O5. The higher the temperature is，the shorter the experiment time of the target component reaches the target component. When the temperature reached 1 400 ℃，the particle size was smaller than 150 μm（100 mesh），the ratio was V2O5 69.69%，carbon powder 6.97%，binder 6.97%，and iron oxide powder 1.39%. The average content of vanadium in the end point was 77.47%. The end point nitrogen content is related to the initial carbon allocation. When the temperature reached 1 400 ℃ and the reduction of V2O5 was sufficient，the sum of carbon and nitrogen content fluctuated between 20% and 21%. The higher the end-point carbon content is，the lower the end-point nitrogen content is. The particle size is 150 μm（100 mesh），the reduction effect of V2O5 is better. The addition of Fe2O3 can improve the density of the product and increase the content of vanadium and nitrogen in the end point.
2018 Vol. 53 (4): 67-73 [
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LI Heng-kun， SUN Xin-jun， ZHAO Bo-jie， CUI Qiang， ZHANG Xiao-xue
Strain aging of new-type Mn-Ni low temperature steel
In order to promote the industrial application of new-type Mn-Ni low temperature steel better，the strain aging sensibility of New-type Mn-Ni low temperature steel is determined by Charpy impact method. The reverted austenite evolution during strain aging is investigated by optical microscopy，transmission electron microscopy （TEM） and X ray diffraction （XRD）. Research results show that，after 5% strain aging，the strain aging sensitivity of the steel is low and the low temperature toughness of the steel is better，the charpy impact energy at －120 ℃ is still above 100 J. The amount of the reverted austenite in the steel is reduced to 9.8%，as some bulk unstable reverted austenite transforms into martensite under the stress.
2018 Vol. 53 (4): 74-77 [
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LI Cheng-liang，HUANG Yuan-jian，WEN Zhi-hong
Continuous cooling transformation behavior and tempering process of Q620D steel plate
In order to determine the best rolling and heat treatment processes，its phase transition laws in continuous cooling is studied by adopting a thermal simulation test machine，and the effect of different tempering processes on the organization and properties is also compared and analyzed. The results show that when the steel Q620D is made by adopting the process of controlled rolling＋ultra fast cooling＋tempering，the cooling speed is equal or greanter than 20 ℃/s after rolling，the tempering temperature is controlled within 550-600 ℃，then the mating of the strength and ductility is the best. The recovery and disappearance of dislocations，decomposition of M/A island structure，transition of Martensite structure，and separation of microalloying elements such as Nb and V commonly effect the strength after tempering and impact ductility at low temperature.
2018 Vol. 53 (4): 78-82 [
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PANG Ke-liang，WU Ji，LIU Dong-jie，WANG Chao，ZHU Qing-miao
Fuel burning control and pollutant emission characteristics of coke oven
In order to master the flue gas pollutants emission characteristic of Ansteel’s coke oven，increase the combustion efficiency，and save the fuel usage of the fuel，the compositions of waste flue gas from12 large-volume coke ovens in Ansteel were quantitatively determined by MGA5 infrared flue gas analyzer. The results show that average oxygen content at the measured points of the JN type coke oven is generally high （4.63%）. The waste gas takes more heat away， which leads to more coking heat consumption and production cost. According to flow through the way of the coke oven fuel and waste gas， multi-point measurement technology of coke oven waste flue gas is put forward， ensuring that fuel is fully combusted， which also reduces air excess coefficient， minimizes the waste away from the heat， and decreases the emission of nitrogen oxides from the coke oven waste flue gas. In addition， the use of multi-point measurement technology also monitors the wall leakage of the regenerative chamber timely， which is conducive to improving the level of operation and management of coking production.
2018 Vol. 53 (4): 83-88 [
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BI Chuan-guang，TANG Jue，CHU Man-sheng
Mathematical modeling of Mei Steel No. 2 BF with coke oven gas injection
In order to achieve the green and low cost ironmaking，Mei Steel will perform the BF operation with coke oven gas（COG） injection. And for insuring the effective injection，the mathematical modeling research of Mei Steel No. 2 BF with COG injection is researched. Firstly，based on the raw material and fuel conditions of Mei Steel No. 2 BF，the mathematical modeling of the BF operation with COG injection is carried out by multi-fluid blast furnace model. Secondly，the economic benefit after COG injection is also preliminarily analyzed. Compared with the base case of no COG injection，when the COG injection is 50 m3/t（Fe），the concentration of reducing gas in the BF increases and the reduction is accelerated；the production increases to 4 740 t/d（increases 30.12%）；the coke rate decreases to 321.80 kg/t（Fe）（decreases 14.43%）；the carbon emission decreases to 355.93 kg/t（Fe）（decreases 8.61%）. On the base of the coke price of 1 607 RMB/t and the COG price of 0.774 9 RMB/m3（supplied by Mei Steel in Nov 2016），the cost of pig iron reduces 20.14 RMB/t，the saved coke for COG injection is 7.79 ten thousand tons per year，and the total economic benefit is 51.15 million RMB per year. Considering the economic benefit，the coke saving potential，the rich oxygen capacity，and the COG surplus of Mei Steel，it is recommended that the rational COG injection for Mei Steel No. 2 BF is maintained around 50 m3/t（Fe）.
2018 Vol. 53 (4): 89-94 [
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