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2018 Vol. 53 No. 5
Published: 2018-05-15
1
WANG Jing-zhong，LI Ke-yuan，LIU A-jiao，DU Zhong-ze
Research status of 40CrNiMo steel at home and abroad
The research status of 40CrNiMo at home and abroad was reviewed in detail from five aspects of conventional heat treatment andproperties，deformation heat treatment，surface heat treatment，precipitation and alloying optimization，and other aspects. The research and application of new technology（surface chemical heat treatment，surface laser quenching，chrome plating shot peening，alloy optimization and precipitation phase）on the production of 40CrNiMo steel and the research of heat treatment（subcritical quenching，cryogenic treatment） on its performance mining were mainly reviewed. In addition，the influence of turning parameters on fatigue strength and surface roughness of 40CrNiMo steel and its fracture characteristics under stress corrosion condition were briefly summarized. The short comings of current research of 40CrNiMo steel and its potential future directions were pointed out.
2018 Vol. 53 (5): 1-10 [
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ZHOU Ming-shun，WANG Yi-dong，ZHAO Dong-ming，WANG Jun-shan，LI Jian-jun，JIN Zeng-wu
Effects of adding high-sulfur magnetite concentrate on pelletizing parameters and performance
Wanli was characterized by high contents of sulfur， magnesium and a low content of silicon. The concentrate had a particle size distribution suitable for the pelletizing process. Apart from magnetite， the concentrate contained pyrrhotite and MgCO3 which accounted for its high S and Mg contents. Most Fe（1-x）S and MgCO3 particles were found to be liberated and presented between the coarse magnetite particles. The effect of adding Wanli concentrate on the balling and roasting performance of Jinhe concentrate was examined. Increasing preheating and roasting temperature was found to have considerably improved the roasting performance of pellets from blends containing high proportions of Wanli concentrate. The pellets containing 70% Wanli concentrate achieved a compression strength of 2 200 N and[w(FeO)]smaller than 1%， which are generally required for pellet production. Metallurgical tests were also carried out on the pellets from the plant basket trials， and the reduction swelling index （RSI） was lower than 12%. In addition， the low-temperature reduction disintegration index （RDI） and reducibility index （RI） were improved.
2018 Vol. 53 (5): 11-17 [
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18
JIANG Da-jun
Experiment on influence of sintering properties with a medium titanium magnetite concentrate
As technical and economic indexes were worse with high titanium concentrate sintering，when a medium titanium concentrate of iron content 55%，TiO2 9%，－0.074 mm size fraction more than 80% matched into high titanium concentrate of TiO2 more than 12.5% sintering by suitable proportion what could strengthen granulation，lower melting point，increase amount of liquid phase and improve the sinter performance indexes so that the most prominent value was saving high price rich ore consumption and reducing sinter cost. The system experiment research was achieved in aboratory and sintering machine as chemical composition，mineral composition and particle size distribution of this medium titanium concentrate is more different comparing with high titanium concentrate. With medium titanium concentrate replacing part of high titanium concentrate sintering，experiment results in laboratory showed that mix partical size was improved，sintering speed accelerated，increasing yield effect was obvious，the rate of increasing output reached 5.35% by each increasing 10% medium titanium concentrate so that can make up the defects of low utilization coefficient of high titanium concentrate sintering.On the other hand，sinter mineral composition was improved，content of calcium ferrite increased and was higher than the reference period，perovskite showed a trend of decreasing，silicate content also increased，metallurgical properties had no change. With 25% medium titanium concentrate insteading of high titanium concentrate，the industrial test results showed that utilization coefficient rose 0.023 t/（m2·h），drum index increased 0.16%，solid fuel consumption decreased，so the sintering overall effect was superior than high titanium concentrate sintering.
2018 Vol. 53 (5): 18-24 [
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25
DENG Yong，ZHANG Jian-liang，JIAO Ke-xin,
Effects of temperature and composition of molten iron on dissolution behavior of carbon brick
In order to explore the dissolution behavior of carbon brick in molten iron，molten iron with different element contents was disposed based on actual molten iron composition in hearth. Carbon bricks made of cylindrical specimens were immersed into molten iron to carry out the experiments with rotating finger stick method. The results show that the dissolution reaction is the main reaction of carbon brick erosion，SEM found the hole diameter of carbon brick increase at the interface after the experiment. The quantitative relationship between temperature，element content and erosion was obtained through the experimental results，the characteristic parameters were selected to compare the influence degree of element content on the erosion. The kinetics model of carbon dissolution reaction was established，the effect of element content on the reaction rate constant was analyzed，the activation energy was calculated to be 46.38 kJ/mol.
2018 Vol. 53 (5): 25-31 [
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32
ZHANG Xue-liang，YANG Shu-feng，LI Jing-she，ZHAI Jun
Effect of heat treatment on oxide inclusion in Si-killed 304 stainless steel
To clarify the effect of heat treatment on the characteristics of inclusions in solid steel， the Si-killed 304 stainless steel was heat-treated at 1 250 ℃ in a resistance furnace. The morphology， size and composition of the oxide inclusions in the samples before and after heat treatment were analyzed by scanning electron microscopy. The experimental results show that the inclusions are mainly spherical single-phase CaO-SiO2-Al2O3-MnO-（Cr2O3） before heat treatment. Mean while，a small amount of MnS is also observed at the edges of some oxide inclusions. After heat treatment at 1 250 ℃ for 1 h， angular MnO-Al2O3-Cr2O3 phase precipitates on the surface of partial oxide inclusions with dimensions less than 4 μm. With the heat-treatment time increasing to 2.5 h， the oxide inclusion size of MnO-Al2O3-Cr2O3 phase observed increases. Meanwhile， the MnO-Al2O3-Cr2O3 phase gradually grows into the center of the oxide inclusions. In addition， for the oxide inclusions existed still as single-phase CaO-SiO2-Al2O3-MnO-（Cr2O3） after heat treatment， the contents of CaO and MnO components in the oxide inclusions are reduced and increased， respectively. However， there is no obvious change in the contents of the Cr2O3，SiO2 and Al2O3 components in the oxide inclusions.
2018 Vol. 53 (5): 32-38 [
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39
YE Fei，LIU Cheng-song，NI Hong-wei，FANG Qing，SONG Xiao
Influence of FeO on compound oxides in Si-Mn deoxidized steel during heat treatment at 1 273 K
In order to investigate the mechanism of interfacial reaction between Si-Mn deoxidized steel and oxides of MnO-SiO2-Al2O3-CaO-MgO-FeO， diffusion couples of the steel and oxides made by confocal scanning laser microscope were used to determine the reaction laws during heat treatment at 1 273 K for 10 h， in which the influence of FeO on the interfacial reaction was mainly studied. The results indicate that FeO would decompose into Fe and [O] in the interfacial reaction process of Si-Mn deoxidized steel and oxides of MnO-SiO2-Al2O3-CaO-MgO-FeO during heat-treatment. As a result，pure Fe particles form in the oxides near the interface between steel and oxides and the excessive [O] diffuses to steel matrix close to the interface， reacting with Si and Mn to generate tremendous amounts of MnO-SiO2-type particles.
2018 Vol. 53 (5): 39-44 [
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45
SUN Bo，ZHANG Liang-ming，WU Yao-guang，XIE Yang-guo，LIU Qian-zhi，WAN Dong
Silicon mass percent control of SPHC steel in thin slab continuous casting
In order to solve the problem of silicon increase in the refinement process of low carbon and low silicon Al-killed steel， the production of SPHC steel in the CSP process of Ma’anshan Iron and Steel Company was combined in the current study，and the influence of the slag quantity in tapping，the hot steel and slag recovery，the content of Al in molten steel，the composition of refining slag and the time of refining treatment on the increase of silicon content in the molten steel was analyzed.Through controlling the slag quantity in tapping less than 3.0 kg/t，reducing the amount of hot steel and slag recovery appropriately and reducing the content of Al in steel，adjusting the composition of refining slag appropriately，improving the basicity of slag and reducing the time of LF refining process can reduce the silicon increase in molten steel during the refining process，which is beneficial to keep the Si content of molten steel in low level to meet the subsequent processing demand.
2018 Vol. 53 (5): 45-51 [
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52
YANG Guang-hui，ZHANG Gao-shang，ZHANG Jie，LI Hong-bo，LU Jian-yong
SMS-EDC edge control characteristics of 2 180 mm super-wide 6-high CVC cold rolling mill
In order to improve the comprehensive shape control capability of a 2 180 mm super-wide tandem cold rolling mill， especially the edge drop control capability， the mechanical model was established for the flexible zone of SMS-EDC work roll， and the end structure and main parameters of the flexible zone of work roll were analyzed and calculated. The three-dimensional finite element model of roll system was built by the finite element software ANSYS15.0. Aiming at the SMS-EDC work roll， the influence coefficients of the central crown and edge drop were analyzed under different work roll’s parameters such as length and internal diameter of flexible area and under different shape control means such as bending force and shifting. Finally， the calculation formulas of roll shifting and bending force of work roll were given in the edge feedback control after deduction. The study can provide a theoretical foundation for the application of edge drop control means on 2 180 mm tandem cold rolling mill.
2018 Vol. 53 (5): 52-61 [
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62
GUO Jin，SHI Jia-xin，CHEN Yu-lai
Effect of delay time before rapid cooling on transformation of micro-alloyed steel
Hardening and softening at high temperature can improve the microstructure and properties of the materials by enhancing the transformation nucleation of the steel. However，it is inevitable to soften between finishing deformation and ultra-fast cooling. The influence of delay time on ferrite and M/A（martensite/anstenite） phase in micro-alloyed low carbon steel（0.055C-1.47Mn-0.17Mo-0.054Nb-0.012Ti）was investigated through the Gleeble thermal simulation experiment，and the delay time is the time from the finishing deformation at 830 ℃ to ultra-fast cooling at the ratio of 80 ℃/s. The phase transformation ratio of M/A phase and the grain size were analyzed and measured by the scanning electron microscope and image analysis respectively. The results showed that in the time range of 2-7 s，the ferrite grain size increased firstly and then decreased with the increase of the delay time before the ultra-fast cooling. The maximum grain size was obtained at the delay time of 5 s while the minimum was 7 s. The volume ratio of M/A phase also showed a trend of decreasing first and then increasing with the delay time prolonging，the shape of M/A phase changed from point to block. Moreover the minimum M/A phase ratio was obtained at 5 s. Considering the influence of delay time on the ferrite and M/A grain size and the ratio of M/A phase，shortening the delay time was favorable to improve the toughness and strength of micro-alloy steel.
2018 Vol. 53 (5): 62-67 [
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68
SUN Xiao-lin，，WANG Fei，，MAO Ming-tao，，CHEN Xi-chun，，DU Guang-wei，GUO Han-jie
Formation and affecting factors of V-rich primary carbides in H13 steel
Primary carbides have an important influence on toughness of H13 steel. Optical microscope，SEM-EDS and EMPA were used to analyze composition，indicating that the carbides was rich of vanadium，as well as size distribution and morphology of carbides. Segregation model and thermodynamics are applied to investigate the formation of different [VCx]carbides. And show the effects of carbides activity variation on formation stage during solidification. It is found that primary carbides can not be formed above liquidus，and vanadium and carbon aggregation mainly influences the carbides precipitation in interdendritic area. VC0.88 carbides can be formed in the mushy zone firstly and easily，then eutectic reaction may be occured for V2C precipitation. Solute segregation has an effect on primary carbides size besides critical precipitation solid fraction and dendritic size. The carbides can be controlled by adjusting initial vanadium and carbon content in steel together with cooling condition during solidification. The precipitation of primary carbides can be inhibited when[w([V]0)≤0.6%、][w([C]0)≤0.37%]in H13 steel，which is important for developing medium alloyed hot work die steel without primary carbides.
2018 Vol. 53 (5): 68-75 [
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76
CHE Xiao-jian，，YANG Mao-sheng，TANG Hai-yan，LI Jian-xin， PANG Xue-dong，SUN Yong
Inclusion control and fatigue performance in high performance GCr15 bearing steel
The smelting process of GCr15 bearing steel has a significant effect on the fatigue properties. Distribution of oxygen，nitrogen，sulfur and nonmetallic inclusions in steel as well as influence rule of fatigue performance were made on smelting process of LF＋VD，electroslag remelting （ESR） and induction melting/consumable in vacuum （VIM＋VAR） to produce GCr15 Bearing steel. The results show that oxygen and nitrogen mass percent of VIM＋VAR smelting process is respectively 0.000 5% and 0.001 6%，The total number of inclusions is only 1.54 per mm2；Oxygen and nitrogen mass percent of ESR smelting process is respectively 0.001 8% and 0.011 0%. The total number of inclusions is 17.78 per mm2. Inclusion is no larger than the 13 μm；Sulfur mass percent of LF＋VD smelting process is 0.002 6%. The mass ratio of sulfur to oxygen in the steel is 3.7.The total number of inclusions is 20.73 per mm2. The ratio of CaS and complex inclusion of CaS and oxide in steel is higher. Rotational bending fatigue test results show that the safety fatigue limits of LF＋VD，ESR and VIM＋VAR are respectively 980，1 164 and 1 158 MPa. The type of inclusions that cause fatigue damage is related to the preparation process. Inclusion type of LF＋VD are CaS，CaS（Oxide） and CaO·Al2O3. Inclusion type of ESR are Al2O3 and CaO·Al2O3. Inclusion type of VIM＋VAR are TiN，MgO·Al2O3 and CaS（Oxide）. According to the real stress factors and fatigue life，the degree of damage to the inclusions in steel from large to small are TiN，CaO·Al2O3，MgO·Al2O3，Al2O3，CaS（Oxide） and CaS. The difference of the type and size of the fatigue source leads to the difference in the safety fatigue limit of the GCr15 bearing steel.
2018 Vol. 53 (5): 76-85 [
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XU Song-qian，ZHAO Hai-ping
Influence of solution treatment on precipitate bearing Nb in S30432 austenitic heat resistant steel
In order to obtain theory basis for heat-treatment of finished tubes， the effects of solution heat-treatment on precipitate behavior of MX phase containing Nb in S30432 austenitic heat-resistant steel were studied. The two chemical compositions of S30432 steel tubes have different heat-treatments，respectively. The microstructure was observed by optical microscope，and MX-type precipitates bearing Nb were analyzed by chemical phase analysis method. The effects of heat treatment，solution temperature and holding time on precipitation behavior were investigated. Based on the results，the effect of solution heat treatment on the Nb bearing precipitates was summarized in S30432 steel.
2018 Vol. 53 (5): 86-90 [
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HE Huan-yu，，SONG Ze-yu，，HOU Wei-wei，
Effect of alkali chloride on sediment of zinc-bearing flus gas from rotary hearth furnace
Zinc-bearing metallurgical dust with alkali chloride in different proportions was studied through reductive and deposition experiment to analyze the effect of alkali chloride and its content on the deposition of the zinc-containing flus gas in rotary hearth furnace. The result shows that when the adding ratio of alkali chlorides is 0.5， 1.0 and 1.5 times to the content of the raw material，the sediments concentrate at the enrichment region located at the range of 600-700 ℃， the ratio of the deposition and total mass increases from 30.49% to 53.33% and the deposition percentage of Zinc and alkali chloride which comes from the raw material assembled in this range increases from 20.75% to 30.72%. The alkali chloride precipitated from the flue gas at the melting point promotes the precipitation of zinc-contained solid particles as the core of crystallization. The alkali chloride in the sediment reduces the critical energy of ZnO particle boundary， engender the augment of fusion between the ZnO particles， and the composite alkali chloride-zinc oxide also increases. Sediment structure is thicker and more compact， and the layered structure of different precipitates is more obvious.
2018 Vol. 53 (5): 91-95 [
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96
SHI Xin-yue，HAN Wei-gang，LI Xiu-ping，ZHANG Chun-xia，CHANG Jin-bao
Application of queuing theory in rhythm of billet of CC-rolling section
CC-Rolling section as one of the components of the interface model，have an important influence on steel production process. With the hot charging technology in-depth application，the matching between the process devices is by the quantity，production capacity，etc. to the production rhythm. The billet rhythm of heating furnace decided to roll the rolling rhythm，thus affecting the rhythm of the entire section. The paper analysis the time interval of CC-Rolling section of the second steel rolling mill in Tangshan Iron and Steel Group，guided by queuing theory，optimize the time interval that the billet enters the furnace of first bar，put forward reasonable time value，and analyzes the reason why the second bars cannot apply queuing theory which provides a theoretical support for the management.
2018 Vol. 53 (5): 96-01 [
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