WANG Biao
,
JI Zhenping
,
LIU Wenhong
,
MA Jiaocheng
,
XIE Zhi
钢铁研究学报(英文版)
By means of Gleeble1500 dynamic thermomechanical simulator, the continuous casting process for HRB335C steel was simulated using solidifying method and hot ductility and strength of the steel were determined. The test results indicate that there are three temperature regions of brittleness for HRB335C billet in the temperature range from 700 ℃ to solidification point; the first temperature region of brittleness is 1 300 ℃ to solidification point of the billet, the second temperature region of brittleness is 1 200-1 000 ℃, and the third temperature region of brittleness is 700-850 ℃; the steel is plastic at 850-1 000 ℃. The cracking sensitivity was studied in the different temperature zones of the brittleness for steel HRB335C and the target surface temperature curve for the secondary cooling is determined. With optimized process, the mathematical model of the steady temperature field with twodimensional heat transfer for 150 mm×150 mm HRB335C steel billet was established to optimize the secondary cooling process. The conic relation of water distribution between secondary cooling water flux and casting speed is regressed. Keeping the surface temperature of billet before the straightening point above 1 000 ℃, the results of billet test indicate that there is free central shrinkage cavity. The billet defect is decreased greatly, and the quality of billet is obviously improved.
关键词:
continuous casting billet;brittle temperature zone;tensile strength;secondary cooling;simulation
LIU Wenhong
,
XIE Zhi
钢铁研究学报(英文版)
To improve billet quality and the trackability and stability of secondary cooling water during continuous casting, the superheat is introduced into the water distribution for secondary cooling to design the relevant control system, based on the water distribution model, superheat, surface temperature and fuzzy self-adaptive PID. A spray cooling system is thus set up for simulation test in laboratory to test the step signal from the conventional, integral separated and fuzzy self-adaptive PID controllers and the simulation casting. The simulation test results show that the fuzzy self-adaptive PID controller’s performance is better than the other two controllers, which provides a foundation for further study and application.
关键词:
fuzzy self-adaptive PID;continuous casting;secondary cooling;superheat
ZU Ling-yu
,
MENG Hong-ji
,
XIE Zhi
钢铁研究学报(英文版)
A compensation model has been proposed to reduce errors caused by the immersion depth of the sensor and the time lag of continuous temperature measurement for molten steel in tundish, which is based on the limited data fitting method and data fusion technology. According to the heat transfer analysis of sensor, the thermal model has been bulit to determine the temperature variation function.The parameters of the compensation model are recognized by generic algorithm, which combines the determine function, the molten steel mass in the ladle and pouring time. The processing of error compensation is divided into three stages: tracking, holding and compensation. When the processing is stable, the measured temperature error is small, and the measured temperature is regarded as accurate value and tracked. For the end of pouring stage of the ladle, the temperature error is caused by the immersion depth of the sensor, and the measured temperature before sharp decreasing is considered as real temperature and held. For the temperature increasing stage after ladle changed, the measured temperature is compensated online.The application results show that the error between the compensation temperatures and the actual ones have been decreased to ±2 ℃, and the time lag could be shortened from 3-5 min to 40 s by applying this model.
关键词:
compensation temperature
,
time lag
,
genetic algorithm
,
error
ZHAO Shu-mao
,
MEI Guo-hui
,
XIE Zhi
钢铁研究学报(英文版)
MgO-C continuous temperature-measuring sensors for liquid steel were made of fused magnesia with different critical particle sizes from 05 to 20 mm, thus the effects what magnesia′s particle size affect sensors′ properties and lifetime were studied. The result shows that the MgO-C continuous temperature-measuring sensor has good aggression resistance to basic tundish powders and meets the requirement for response time of temperature measuring practice in tundish. The sensor′s service life, which is affected by multi-properties of material and operating environment, reached its maximum when the critical particle size of magnesia was 10 mm. The average lifetime of sensors was 43 or 40 h when served for casting SPHC or Q195 steel.
关键词:
MgO
,
carbon
,
microstructure
,
sensors
,
lifetime
,
particle size
刘建国
,
安振涛
,
张倩
,
杜仕国
,
姚凯
,
王金
材料导报
doi:10.11896/j.issn.1005-023X.2017.04.030
为评估氧化剂硝酸羟胺的热稳定性,使用标准液体铝皿于3 K/min、4 K/min、5 K/min加热速率下进行热分析.借助非等温DSC曲线的参数值,应用Kissinger法和Ozawa法求得热分解反应的表观活化能和指前因子,根据Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式以及Zhao-Hu-Gao公式,计算硝酸羟胺的自加速分解温度和热爆炸临界温度,并对热分解机理函数进行了研究.设计了7条热分解反应路径,采用密度泛函理论B3LYP/6-311++G(d,p)方法对硝酸羟胺的热分解进行了动力学和热力学计算.计算结果表明,硝酸羟胺热分解的自加速分解温度TsADT=370.05 K,热爆炸临界温度Te0=388.68K,Tbp0=397.54 K,热分解最可几机理函数的微分形式为f(a) =17×(1-α)18/17.硝酸羟胺热分解各路径中,动力学优先支持路径Path 6、Path 5、Path 4和Path 1生成NO和NO2,其次是Path 2、Path 7和Path 3生成N2和N2O.温度在373 K以下时,Path 1'反应无法自发进行,硝酸羟胺无法进行自发的热分解.从热力学的角度来看,硝酸羟胺在370.05K以下储存是安全的.
关键词:
硝酸羟胺
,
热分析
,
热稳定性
,
热分解机理
,
密度泛函理论
