WANG Qian
,
LU Yongjian
,
HE Shengping
,
WANG Lijuan
,
K C Mills
钢铁研究学报(英文版)
Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.
关键词:
mould flux; sintering property; differential pressure; apparent sintering temperature
JIAO Xiaohong
,
SHAO Liping
,
PENG Yan
钢铁研究学报(英文版)
To further improve the control accuracy for strip dimension of hot strip mills, an adaptive control scheme is investigated for a hot strip finishing mill based on the decentralization and coordination among the controllers of gauge, tension and looper. Consequently, the adaptive controller designed can regulate simultaneously the strip exit thickness, the strip tension and the looper angle to ensure better performance of the strip quality of finishing mills. Moreover, the control scheme is proposed in consideration of the essential nonlinearity and the unavoidable friction phenomena in the mechanical system, so the controller can be efficient in a wider range of working situations. The simulation results of a model obtained from a real hot strip finishing mill show the effectiveness of the proposed control scheme in comparison with the conventional control method.
关键词:
hot strip finishing mills; exist gauge; tension; looper angle; adaptive control
SHAN Xiu-ying
,
LIU Hong-min
,
JIA Chun-yu
,
SUN Jian-liang
钢铁研究学报(英文版)
Using the effective matrix methods of flatness and profile control synthetically, the flatness and profile integration control scheme for tandem cold mills is built in order to increase flatness and profile control precision of tandem cold mills. Corresponding control strategies are adopted for various control objectives of different stands and the coordination control strategies of various stands are given, which makes the on-line flatness control cooperate with on-line profile control and implements the parallel control of different stands. According to the measured flatness and profile data of some 1550 mm tandem cold mills, the control scheme is verified and the result indicates that the scheme has high flatness and profile control precision with steady and reliable control process. A new way and method is supplied for researching shape control of tandem cold mills.
关键词:
flatness
,
profile
,
shape
,
effective matrix
,
tandem cold mill
ZHONG Zhao-zhun
,
WANG Jing-cheng
,
ZHANG Jian-min
,
LI Jia-bo
钢铁研究学报(英文版)
An innovative sliding mode controller for looper and tension control in hot strip finishing mills was developed based on approximately linearized model. Firstly, a fictitious controller of the reduced order subsystem was designed according to desired dynamics, by which, the angle and tension loops were decoupled on the sliding manifold. Then, a sliding mode controller was used to validate finite time convergence of the state vector to the manifold which guaranteed the stability and performances of the overall system. This solution was considered owing to its well-known robustness and simplicity characteristics concerning disturbances and unmodelled dynamics. Simulation results showed the effectiveness of the proposed controller compared with conventional ones.
关键词:
sliding mode control
,
looper control
,
tension control
,
hot strip finishing mill
Materials Letters
Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
M6C precipitation;aging;M7C3 carbide;superalloy
龙期威
,
高桦
金属学报
本文从裂纹顶端位错运动的简化模型估计形成塑性区所消耗的功;从而计算临界裂纹扩展力。由于Ⅰ型加载和Ⅱ型加载的应力状态有所不同,裂纹顶端塑性功耗也会不一样。基于上述思想,考虑了小范围屈服的K_(Ⅰc)和K_(Ⅱc)的关系,得出K(Ⅱc)>K(Ⅰc)的结论,符合实验结果;并就K(Ⅱc)/K(Ⅰc)的比值与材料性能和温度的关系作了讨论。
关键词:
LI Haijun
,
XU Jianzhong
,
WANG Guodong
,
LIU Xianghua
钢铁研究学报(英文版)
Load distribution is a key technology in strip hot rolling process, which influences the coil′s microstructure and performance. Currently, NewtonRaphson algorithm is applied to load distribution of hot tandem mills in many hot rolling plants and has some serious defects such as having a strict restriction on initial iterative calculation value and requiring coefficient matrix of nonlinear equations to be nonsingular. To eliminate these defects and improve the online performance of the process control computer, Newton descendent numeric algorithm is introduced to this field to widen the initial value range and a new model named error conversion algorithm is put forth to deal with special conditions when the coefficient matrix is singular. Furthermore, considering the characteristics of load distribution, a condition of strip thickness distribution abnormality and corresponding solutions are provided which ensure that rolling parameters can be calculated normally. Simulation results show that the improved algorithm has overcome the defects of the NewtonRaphson algorithm and is suitable for online application.
关键词:
load distribution;hot tandem mill;process control computer;NewtonRaphson algorithm
刘勤
,
夏锄
,
刘晓东
金属学报
在170,190,210,230,250℃的温度下,采用3.7×10~2,7.4×10~2和1.1×10~(-1)min(-1)的应变速率(平均)对Zn-5%Al共晶合金的m-C-δ(或m-k-δ)关系曲线(简称m-δ关系曲线)进行了测定.所有的曲线均随应变的δ增加而快速上升.俟达到某一定的应变量(极限应变量δ1)后。开始缓慢下降并保持平稳直至断裂.Zn-5%A1共晶合金的m-δ关系曲线不存在k_(?)=k_I(k_(I 1),k_(I 2),k_(I 3),……)=k_F(或C_0=C_I(C_(I 1),C_(I 2),C_(I 3),……)=C_F=1)的简单情况.可应用m-δ方程式[4,5]对曲线上各点C值(包括所有的C_I和C_F值)进行计算.C值随δ值的增加成近似的直线上升.直线的斜率在极限应变(δ1)处突然减小.
关键词:
Thin Solid Films
The SiO(2)-Al(2)O(3)-ZrO(2)-CaO-ZnO glass-ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass-ceramic coatings and the NiCoCrAlY coatings were about 10 mu m and 20 mu m, respectively. Cyclic oxidation tests were carried out at 1100 degrees C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass-ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 degrees C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass-ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass-ceramic coatings. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Glass-ceramic coating;NiCoCrAlY;Cyclic oxidation;Magnetron sputtering;resistance;microstructure;scales
