Time filter

Source Type

Luo Z.,Northeastern University China | Liu H.,Northeastern University China | Wang F.,Northeastern University China | Xu L.,Fushun Special Steel Co Ltd
International Journal of Modelling, Identification and Control | Year: 2010

The current development of human-simulated intelligent control (HSIC) is introduced and the basic concepts, ideology and features are summarised. Then, examples are taken for the prototype algorithm of HSIC; the static characteristics, dynamic characteristics and stability of HSIC are analysed. The basic design steps of HSIC are further cleared. Finally, the application of HSIC in the trajectory tracking control for robot system is studied. In fact, HSIC is for choosing the appropriate control strategy according to the sign of the characteristic variables of the control system. The experimental results show that the HSIC method improves the control precision greatly. Copyright © 2010 Inderscience Enterprises Ltd.

Wang M.,Kunming University of Science and Technology | Wang M.,Control Iron and Steel Research Institute, China | Ma D.,Control Iron and Steel Research Institute, China | Liu Z.,Fushun Special Steel Co Ltd | And 3 more authors.
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2014

Mandrel is an important tool for thermal deformation of the seamless steel tube rolling unit. It requires high heat resistance and toughness due to its application in the harsh environment. H13 steel is commonly used as mandrel materials with excellent comprehensive performance. It is reported that addition of carbide-forming elements, such as Nb, Ti, or Zr, especially the Nb element, can break the dendritic microstructure and refine the cast structure of H13 steel. In addition, Nb can act as a strong carbide-forming element to favor the formation of MC carbide. This stable carbide has low solubility and does not dissolve in austenite even at high temperature, and hence fines austenite grain by pinning effect of carbide on grain boundary. As the stable NbC has stronger ability to improve the fatigue resistance and abrasion resistance than Mo6C and VC, the mandrel steel can be produced by the method of Nb addition. It has been reported that the addition of Nb in H13 can successfully increase heat resistance. Nb element dissolves into the matrix after quenching and tempering, and precipitates in the form of NbC after heat preservation for a long time, and eventually improves the resistance of material to temper softening. However, it has not been widely applied in the production because the primary carbides of NbC can seriously deterio- rate toughness of steel. The purpose of the work is to analyze the effect of addition of 0.06%Nb (mass fraction) on segregation, primary carbides and toughness of large size H13 mandrel steel. The different segregation, primary carbides, structure between large size H13 and H13-Nb mandrel were investigated by employing methods of OM, SEM, EDS and EBSD, and the mechanical properties including the hardness and impact toughness were measured at room temperature. The results show that addition of 0.06%Nb aggravates segregation compared with H13. Nb increases the precipitation temperature of MC-primary carbides, and changes the type of MC-primary carbides from mainly VC to mainly (Nb, V)C which easily induces gravitational segregation of H13-Nb. The severe segregation leads to unfavorable structure of the large and nonhomogeneous effective grain size (EGS) of annealed H13-Nb, and the primary carbides do not decrease or change significantly after quenching and tempering. In the impact test, the zone of the chain-shaped carbides gathering is prone to cracking and generates horizontal stripes, resulting in low toughness. © Copyright.

Li Z.-X.,Northeastern University China | Li C.-S.,Northeastern University China | Zhang J.,Northeastern University China | Li B.-Z.,Northeastern University China | Pang X.-D.,Fushun Special Steel Co Ltd
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2016

The effect of final rolling temperature and cooling process on the microstructure of 1.0C-1.5Cr bearing steel was studied, and the relationship between the microstructure parameters and subsequent spheroidization annealing was analyzed. The results indicate that the increase of water-cooling rate after hot rolling and the decrease of final cooling temperature are beneficial to reducing both the pearlite interlamellar spacing and pearlite colony size. Prior austenite grain size can be reduced by decreasing the final rolling temperature and increasing the water-cooling rate. When the final rolling temperature was controlled around 1103 K (830 °C), the subsequent cooling rate was set to 10 K/s and final cooling temperature was 953 K (680 °C), the precipitation of grain boundary cementite was suppressed effectively and lots of rod-like cementite particles were observed in the microstructure. Interrupted quenching was employed to study the dissolution behavior of cementite during the austenitizing at 1073 K (800 °C). The decrease of both pearlite interlamellar spacing and pearlite colony size could facilitate the initial dissolution and fragmentation of cementite lamellae, which could shorten the spheroidization time. The fragmentation of grain boundary cementite tends to form large-size undissolved cementite particles. With the increase of austenitizing time from 20 to 300 minutes, mean diameter of undissolved cementite particles increases, indicating the cementite particle coarsening and cementite dissolution occuring simultaneously. Mean diameter of cementite particles in the final spheroidized microstructure is proportional to the mean diameter of undissolved cementite particles formed during partial austenitizing. © 2016 The Minerals, Metals & Materials Society and ASM International

Zhang H.,Harbin Institute of Technology | Zhang K.,Harbin Institute of Technology | Zhou H.,Harbin Institute of Technology | Lu Z.,Harbin Institute of Technology | And 2 more authors.
Materials and Design | Year: 2015

The hot deformation behavior of a nickel-based superalloy was investigated by means of isothermal compression tests in the strain rate range of 0.001-10 s-1 at 1110°C. Transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) technique were used to study the effect of strain rate on the microstructure evolution of the alloy during hot deformation. The results revealed that the dynamic recrystallization (DRX) process was stimulated at high strain rates (ε˙≥5s-1) due to the high dislocation density and adiabatic temperature rise. Meanwhile, high nucleation of DRX and low grain growth led to the fine DRX grains. In the strain rate rage of 0.001-1 s-1, the volume fraction of DRX grains increased with the decreasing strain rate, and the grain growth gradually governed the DRX process. Moreover, the strain rate has an important effect on DDRX and CDRX during hot deformation. On the other hand, particular attention was also paid to the evolution of twin boundaries during hot deformation. It was found that there was a lower fraction of σ3 boundaries at the intermediate strain rate of 1s-1, while the fractions of σ3 boundaries were much higher at both the lower strain rates (ε˙≤0.1 s-1) and higher strain rates (ε≥5 s-1). © 2015 Elsevier Ltd.

Zhang H.,Harbin Institute of Technology | Zhang K.,Harbin Institute of Technology | Jiang S.,Harbin Institute of Technology | Zhou H.,Harbin Institute of Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2015

The hot deformation behavior of a γ′-hardened nickel-based superalloy was investigated by means of isothermal compression tests in the temperature range of 1010-1210 °C with a strain rate of 0.1 s-1. The electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM) were employed to investigate the effect of deformation temperature and strain on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). Microstructure observations revealed that the size and volume fraction of DRX grains increased with the increasing temperature. A power exponent relationship was obtained between the stable DRX grain size and the peak stress. Additionally, it was found that the effect of CDRX characterized by progressive subgrain rotation became weaker with the increasing deformation temperature, and DDRX was the operating nucleation mechanism of DRX at higher deformation temperature. On the other hand, the effect of DDRX became stronger with the increasing strain, and CDRX can only be considered as an assistant nucleation mechanism of DRX at the later stage of deformation for the alloy deformed at 1160 °C. Nucleation of DRX can also be activated by the twinning formation. Hence, particular attention was also paid to the evolution of twin boundaries during hot deformation. © 2014 Elsevier B.V.

Discover hidden collaborations