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2014 Vol. 49 No. 12
Published: 2014-12-15
1
KANG Yong-lin， ZHU Guo-ming
Development Trend of China’s Automobile Industry and the Opportunities and Challenges of Steels for Automobiles
Firstly, the current situation and development trend of China’s automobile industry were analyzed and predicted, the auto production is likely to reach around 36 million in 2020. With the rapid development of auto, automotive steels are also facing challenges such as safety, environment, resource, energy, cost, and so on. The rapid growth of auto and huge market in China bring great opportunities for the development of automotive steel, while the metallurgical industry is also facing fierce competition from the non-steel material and challenges of users. The development potential of automotive steels and the response options that may be taken by steel industries are discussed. The recent development of alloy content in high strength automotive steels, the fine control and application technology of microstructure and properties in new high strength steel, the fine microstructure of ultra-high strength dual phase steel and quenching-partitioning steel, the control of nanoparticle precipitation in cold rolled high strength steel, the process and microstructure and properties of hot stamped steel, the forming technology and application of advanced high strength steel were also analyzed. Finally, the strengthening and improvement of early vendor involvement (EVI) service system of automotive steel suppliers were introduced.
2014 Vol. 49 (12): 1-7 [
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ZHANG Dai-lin， WANG Wei， WANG Kun， HUANG Da-zhong，LI Wei-feng， ZHENG Ming-dong
Coking Property Difference Between Canada Coals and Some Domestic Coking Coals
It was benefit for domestic coking enterprise to make good use of Canada coals and optimizing coal blending, by studied the difference of caking property between Canada coals and main domestic coking coals. To explore the reason of differences of caking property of these coals, the conventional coal quality and petrography analysis of these coals was studied and test Canada coals replace domestic high quality coking coals by 40 kg poilt coke oven test. The result showed that: compared with the domestic coking coals, ash content and metamorphism degree of Canada coals was lower, and it has good singleness; Canada coals has lower Giseeler fluidity lgMF and AoYa dilatation [b] value, there was less homogeneous vitrinite in it, and it had more crack and pore in vitrinite maceral, which make lower fluidity and expansion pressure in melting stage of coking process; Canada coals can replace domestic high-quality coking coals for coking, and can stabilize the coke quality.
2014 Vol. 49 (12): 8-12 [
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13
JIAO Ke-xin, , ZHANG Jian-liang, , ZUO Hai-bin, , SHEN Meng ,TIE Jin-yan , LI Feng-guang,
Thermal Trial Analysis on Unsteady Heat Transfer for Blast Furnace Cooling Stave
BF campaign is of great significance for efficient, sustainable development of iron and steel enterprises. Smooth operation and the service life of the cooling stave is one of the fundamental factors affecting the life of a blast furnace, and therefore subject to focus on the stave efficient longevity research. Through design and construction of hot test furnace for cooling stave, unsteady state heat transfer of blast furnace cooling stave was studied under condition of with or without slag crust and changing rules of thermocouple temperature under different furnace temperatures were also analyzed. Changing rules of thermocouple temperature at heating stage, steady stage and cooling stage were obtained by regression method. Average heat flux intensity without slag crust was calculated and through regression method convective heat transfer coefficient was obtained. It was concluded that the changing rate of thermocouple temperature which embedded in the cooling stave under condition of with slag crust is significantly lower than without slag crust. The damage of cooling stave is mainly due to thermal stress produced by repeatedly change of temperature and frequently production and separation of slag crust, which shows the actions that are being executed and the results that are extending the cooling stave service lives.
2014 Vol. 49 (12): 13-17 [
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18
LI Yang-long， CHENG Shu-sen， WANG Ying-sheng
Mechanism and Preventive Measures of Upturned Blast Furnace Bottom Sealing Plate
The phenomena of the upturned bottom sealing plate were found from several blast furnaces (BFs) field surveys. The bottom sealing plates of some Blast Furnaces were even upturned 100-140 mm height, which led to bottom transformed into pot shape, the gas leaked from bottom and the bottom cooling effects weakened. It’s harmful for the longevity and efficient productivity of BF. The temperature field and thermal stress field mathematical model of hearth bottom was established and the effects of abnormal expansion, normal thermal expansion of lining bricks, thickness of bottom sealing plate, expansion joint and refractory cushion mortar on upturned height of bottom sealing plate were analyzed. Because of the abnormal expansion of lining bricks, big upward pressure at the tuyere combined bricks can be generated and the bottom sealing plate would be upturned finally. However, the normal thermal expansion of lining bricks could not result in the large upturned height of bottom sealing plate. The accumulation and enrichment of harmful elements such as alkalis, zinc and plumbum might lead to abnormal expansion of bricks and the upturning of bottom sealing plate. It can mitigate the transformation of bottom sealing plate with increasing thickness of bottom sealing plate. The appropriate expansion joint and good refractory cushion mortar can absorb the thermal expansion, but it can’t solve the large abnormal expansion. In order to restrain and reduce the phenomena of upturned bottom sealing plate, the enough expansion gap should be needed at the tuyere combined bricks and the front of tuyere-cooler casing should not be deep into the lining bricks. And also the charging amount of harmful elements should be controlled strictly and the discharging ability of harmful elements needs to be improved.
2014 Vol. 49 (12): 18-23 [
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24
LI Fu-min, YI Feng-yong, BAI Rui-guo, SUN Kai, Lü Qing
Influence of Sintering Parameters on Binding Phase Strength of Mixed Iron Ore
The binding phase strength of mixed iron ore with high limonite ratio was determined by micro-sintering apparatus at different sintering temperature, basicity and MgO content. The results reveal that, binding phase strength of mixed iron ore increased at first and then decreased as sintering temperature, basicity and MgO content increased. It reached the highest value when the sintering temperature was 1 280 ℃, alkalinity was 1.6 and mass percent of MgO was 2.0%. Limonite ratio should be reduced appropriately in production, so that the mixed iron ore has adequate binding phase strength.
2014 Vol. 49 (12): 24-27 [
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KANG Lei， CHE Yu-man， WANG Bao-hai， GUO Tian-yong， SHANG De-li， Lü Chun-feng
Damage Reason Analysis of BF Copper Stave
It was generally acknowledged that the area of lower shaft, belly and bosh of blast furnace was a weak link of the whole structure. With the application of copper stave, this problem has been solved. Meanwhile, the BF life has been prolonged significantly. However, because of the slag skull being removed from copper stave hot surface, phenomena of naked on copper stave hot surface happened occasionally which resulted in copper stave being damaged extensively and had serious influence on production. The damage condition was described. By means of metallography, SEM and EDS, chemical analysis, a sampling study has been made on damage copper cooling stave of blast furnace. The results show that, the damage of copper stave is caused by hydrogen embrittlement which is due to higher oxygen content of copper stave scoured by high temperature gas current. Also, several suggestions on preventing the damage of copper stave has proposed.
2014 Vol. 49 (12): 28-32 [
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33
MA Chao, CHAO Wei, LI Dong-tao, LIU Yang, XU Meng, XU Rong-guang
Relationship Between Carbon Dissolution and Microstructure of Coke in Shouqin
Because of low cost and high performance index, the stamping coke had been gradually popularized and applicated. However, after using the stamping coke in the blast furnace of Shouqin, it appears several problems such as pressure instability and instable BF performance. In order to make out the actual properties of this batch of coke, the reactivity test, TG-DTA test and optical texture analysis were conducted. The results indicated some relations between optical texture content and quality of cokes. The mosaic texture in the optical texture of coke had an effect on controlling the development of cracks and relieving thermal expansion. The content of mosaic texture in the stamping coke was lower, so it was more prone to generating the cracks in the condition of high temperature and impact. From the weight loss curves of six kinds of coke powder, it can be found that the gasification reaction rate of the stamping coke with high ΣISO increased faster in the process of the temperature from 1 000 ℃ to 1 300 ℃. In that case, it is possible to cause more serious particle degradation, resulting in the instable BF performance.
2014 Vol. 49 (12): 33-37 [
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JING Yu-an, ZANG Xiao-ming, SHANG Qiu-yue, QIN Yi, LI Fu-qiang, LIU Ying-ming
Surface Morphology Evolution of Steel Strip During Cold Rolling After Hydrogen Reduction
A five-pass cold rolling experiment of steel strip after hydrogen reduction was performed on a 4-high mill. The surface morphologies of samples were observed by SEM and the surface roughness curves were measured by using a TR200 roughness meter before and after rolling deformation. The evolution rules of the sample surface morphology under different roll surface roughness and lubrication conditions were emphatically analyzed and discussed. The results showed that most of defects on the sample surface were roll-flattened after five-pass cold rolling, and the remains turned into micro pits leaving on the sample surface. The surface smoothness increased with the increase of rolling passes. The cracks were easier to be roll-flattened and the residual defects were less and shallow on the sample surface but the roller marks were relatively more under the condition of dry friction than under the condition of oil lubrication.
2014 Vol. 49 (12): 38-43 [
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YANG Jing-ming, HU Zi-yu, CHE Hai-jun, SUN Hao, ZHAO Xin-qiu
Load Distribution Optimization on Tandem Cold Rolling Mill Based on Improved Differential Evolution Algorithm
To reasonably make schedules of the load distribution of tandem cold rolling mill, slip factor, power margin and minimum energy consumption were selected as the optimization functions. The improved differential evolution algorithm was used to search the Pareto front, which reduces redundant iterations and decreases computation time. Different load distribution strategies based on different objectives were generated from the Pareto front to satisfy the requirements under different operating conditions. The simulation shows the proposed algorithm covers the front fast and evenly and generates different load distribution strategies based on different objectives. Compared with the original schedule, the proposed method reduces the probability of slippage and the rolling power.
2014 Vol. 49 (12): 44-49 [
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BAO Ren-ren, ZHANG Jie, LI Hong-bo, GONG Gui-liang, JIA Sheng-hui, LIU Hai-jun
Calculation Method of Flatness Index in Cold Rolling
Most of the tandem cold rolling mills are equipped with one or two flatness measurement device used for real-time control and flatness assessment of the strips. Distribution of transducers is different and uneven. Flatness index is an important parameter to characterize cold-rolled strips, which is provided by the automatic flatness control system and usually presented by IU (I-Unit). In order to express the flatness of strips exactly, the calculation method of an actual flatness control system provided by SIEMENS was analyzed, and the effect of uneven distribution of the transducers was considered. On this basis, linear interpolation was introduced to build an even and transverse elongation distribution model, and the formal flatness index calculation method was modified. Verified by actual flatness data, the new method was independent of the distribution of transducers, which improves the comparability of flatness of strip produced by different cold rolling mills.
2014 Vol. 49 (12): 50-53 [
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HU Xian-lei， ZENG Qing-liang， DING Jing-guo
End Heavy-Reduction Method for Plate Rolling Process
To enhance reduction in pass is of significance to improve performances of thick plates. By analyzing the change of torsion in each rolling pass, it is known that the peak torsion at biting-in phase of front end is the critical factor which limits the reduction in pass. Based on the change rules of rolling torque at steady phase of the whole rolling process, end heavy-reduction method was put forward, which means that the reduction in pass can be properly increased at the plate end for forward rolling pass to form wedge or ladder shape, then the reduction in pass of full-length can be increased at the subsequent inverse rolling pass because the front end of plate is thinner. The amplifying range of reduction in pass was determined by the relationship of rolling torsion to reduction in pass. The method can effectively increase the core deformability of thick plate without reforming the rolling equipments, so it is suitable for application in plate mill.
2014 Vol. 49 (12): 54-58 [
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JIANG Lu， SUN Xin-jun， LI Zhao-dong， YONG Qi-long
Effects of Tempering Temperature on Morphology of Metastable Austenite and Mechanical Properties of Mn-Ni Steel
Effects of tempering temperature on morphology of metastable austenite and mechanical properties of Mn-Ni steel were investigated by X-ray Diffraction (XRD), Electron Back Scattering Diffraction (EBSD) and Transmission Electron Microscope（TEM）. The results show that the volume fraction of metastable austenite at room temperature increased with the increase of tempering temperature. When tempering temperature was 600 and 625 ℃, metastable austenite mainly precipitated in the shape of thin film along the lath boundaries of tempered martensite, paralleling to the surrounding martensitic laths. This thin film metastable austenite had a dense distribution, with the thickness ranging from 60 to 100 nm, and had a good stability; when the tempering temperature was 650 ℃, thin film metastable austenite decreased dramatically and large block metastable austenite precipitated unevenly on the intersections of grain boundaries of tempered martensite. Analysis indicates that block metastable austenite is beneficial to the ductility of test steel, but it goes against to improving low temperature toughness; while thin film metastable austenite can improve low temperature toughness significantly.
2014 Vol. 49 (12): 59-64 [
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YUE Er-bin， LI Na
Effect of Rare Earth Cerium on the Magnetic Properties of 2.9%Si Non-Oriented Electrical Steels
In order to obtain high grade non-oriented electrical steel with excellent magnetic properties, the effect of Ce on the formation of inclusions, microstructure, texture and magnetic properties of 2.9%Si non-oriented electrical steel was investigated in depth and systematically. The results show that the proper content of Ce (0.005 5%) could make the inclusions in steel aggregated and coarsened. Therefore, the recrystallized grain size increased together with {100} and {110} texture component, and {111} texture component decreased. Under this condition, the magnetic properties reached an optimal value. However, when an excessive amount of Ce (0.019%) was added, all the effects would become opposite.
2014 Vol. 49 (12): 65-70 [
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HU Xian-jun， ZHAO Yu-fei， WANG Lei， MA Han， FANG Feng
Effect of Vanadium on the Microstructure and Properties of High Carbon Steel Wires
Vanadium has obvious effects on the microstructure, mechanical properties and thermo-stability of high carbon steel wire. In high carbon steel, vanadium mostly exists in cementites to reinforce them. The addition of vanadium is beneficial to the refinement of pearlite lamella spacing, and can increase the thermo-stability of cementites, so as to restrain cementite dissolution during steel wire drawing. However, fragmentation occurs to cementites with rich vanadium under a larger drawing strain, and steel wire spheroidization would aggravate during galvanizing, which, compared to non-V-alloyed steel wire, leads to the obvious decline of torsional property no matter V-alloyed steel wire is galvanized or not.
2014 Vol. 49 (12): 71-75 [
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CHANG Zhi-yuan,, HUO Xiao-xin, QIU Chun-lin, LAN Liang-yun,GONG Run-yan, XU Chun-shen
Microstructure and Properties of CO2 Arc Weld Joints for Ultralow-Carbon Microalloyed X100 Pipeline Steel
CO2 arc welding technique was employed to weld X100 pipeline steel. The influence of welding procedure on the microstructure and properties of welding joints was analyzed. With the weld heat input increasing, the yield strength and tensile strength of welded joints decreased and the impact absorption energy of the weld and heat affected zone increased at first then decreased. However, the microstructure of all welds was mainly made up of acicular ferrite. The main microstructure in CGHAZ was bainitic ferrite which could bring excellent strength and toughness when the heat input was 1.17 kJ/mm. As the weld heat input was increased to 1.91 kJ/mm, Granular bainite and bainitic ferrite were formed, the strength and toughness decreased. Considering all these factors, 1.17 kJ/mm was recommended as the optimal heat input in the CO2 arc welding process of X100 pipeline steel.
2014 Vol. 49 (12): 76-79 [
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CHEN Jun,
Experimental on Making Slag Modifiers by Converter Dedusting Resources
in order to realize the cyclic utilization of converter dedusting resources, precipitator dust, converter slug, waste magnesite brick, carborundum and adhesives were mixed according to a certain proportion to make modifier to change the final slag of converter, and industrial test was carried out to verify the modifing effect of the new modifier. Industrial test shows that by using the new modifier, TFe content of the slag reduced by 1.31%, while MgO content increased by 0.71%; compared with the original modifier, slag rising time and splashing time were shortened by 0.11min and 0.12min respectively. The new modifier obtained a better slag splashing effect. The successful development of the new modifier not only made the secondary resource cyclic utilization but also improved the metallurgical effect and reduced cost of production。
2014 Vol. 49 (12): 80-84 [
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LI Sheng-cun
Research and Practice in Side Trimming Technology of IF Steel
Aiming at the low percent of pass of side trimming of IF steel after pickling and cold rolling, the essential factors that caused the defects of side trimming and the precautionary measures were investigated and the operational principle of side trimmer was researched. The measures such as limiting the side clearance and the overlapping deviation of the side trimmer before it works, increasing the hardness of the side trimmer, reasonable matchup of the side clearance and the overlapping, and keeping the stable and high speed of side trimming were taken. All the above measures increased the percent of pass of side trimming greatly, which laid the foundation of producing the rolled steel within width allowance and also ensured the smooth operation of rolling mill and stable production.
2014 Vol. 49 (12): 85-89 [
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