Xiao Ming Zhang

Finite element simulation of cold rolling of thin strip

Abstract In this work, the authors use a full 3D rigid plastic finite element method (FEM) to simulate the thin strip rolling taking into account the modelling of friction variation in the roll bite. A comparison of the computed results with measured values was conducted. The characteristics of the distribution of the velocity along the width of strip at the exit of the roll bite and the spread of strip for the different crown factors are presented in this paper. The modelling of the shape, profile and flatness for cold rolling of thin strip with friction variation is also discussed.

Numerical modelling of the thermal deformation of CVC roll in hot strip rolling

Abstract An accurate prediction for the thermal crown of the continuously variable crown (CVC) work roll is a key to improve the accuracy of the computer on-line control model. In this paper, the authors have developed a finite difference model to simulate the thermal deformation of the CVC work rolls in hot strip rolling. The effects of the heat generation produced by the strip deformation and friction, heat conduction and convection on the thermal crown are introduced in the simulation. A comparison of the calculating roll temperature and measured values shows that they are in good agreement. Result shows that a model of calculating the thermal crown of the CVC rolls can be obtained based on the finite difference method. The modelling of the thermal crown of CVC rolls in hot strip rolling can improve the accuracy of on-line control model.

A novel nano-TiO2 additive oil-in-water lubricant for hot steel rolling

To obtain a low cost, environmentally friendly and effective lubricant, a novel nanoTiO2 additive oil-in-water (O/W) lubricant for hot steel rolling has been developed. Based on the contact angle, tribological and hot rolling tests, the performance of the nanoTiO2 additive O/W lubricants was evaluated and discussed. The results show that the strongest adhesion force between the nanoTiO2 additive O/W lubricant and the work roll is obtained after addition of 4% nanoTiO2 additive in the 1% O/W lubricant. The nanoTiO2 nanoparticles can reduce coefficient of friction (COF) and rolling force, and enhance the surface quality of the hot-rolled product. The lubrication mechanism of nanoTiO2 additive O/W-based lubricant has been proposed.

The Study on Fuzzy Control of Automotive Clutch

Due to the complexity of the car running condition, the differences of the subjective intention of the driver, and Continuously Variable Transmission control system itself existed nonlinear, time delay, interference, variable parameter factors, the traditional control arithmetic based on scale model is hard to meet the clutch control requirements. This article through to design the drive mechanism of the dry friction clutch on a new, without hydraulic pump, pure electronic control car continuously variable transmission, and analyze its mechanical properties and control target, the clutch control model was established, according to the fuzzy control theory, driving experience and developers’ technical experience, the corresponding fuzzy language rules were formed, and intelligent control of the clutch on the single-chip control system was realized. At present, the pure electronic control continuously variable transmission has been tested on the experimental bench and car operation, and has passed the inspection by the national vehicle quality supervision and inspection center (Chongqing) and the identification by China Machinery Industry Federation .

Structure and Precipitation of Strip As-Cast and Hot-Rolled by TSCR on Oriented Silicon Steel

The simulation studies were carried out on the oriented silicon steel produced by thin slab casting and rolling (TSCR) and twin-roll strip casting in the laboratory. The precipitation of inhibiter, formation of microstructure and texture were investigated before cold rolling. The inhomogeneous microstructure and texture gradient were observed in the 7-pass hot-rolled strip（2mm）for TSCR process, and texture gradient was not changed after normalizing, and the twin-roll strip casting directly supplied a strip with approx 2mm of thickness being same as that of hot-rolled strip by TSCR. The microstructure of twin-rolling casting strip was almost composed of all equiaxed grains which similar to the normalizing microstructure in TSCR process, but the random texture was obtained by twin-rolling strip casting. The dispersed and clustered precipitates were presented in hot-rolled strip when the ingots were soaked at 1200°C and 1150°C respectively for the TSCR process. And disperse and acicular precipitates were observed by TEM for air-cooling cast strips for process twin-rolling casting.

Study on Casting Roll during Twin-Roll Casting of Thin Strip

In twin-roll thin strip casting, the temperature of casting roll affects the roll thermal stress, and influences the thermal deformation, the generation of roll surface cracks, the strip shape and the service life of casting roll. In this paper, the features of the casting roll materials have been analysed, the effects of the clad materials and thickness on temperature field of the casting roll have been simulated and discussed. The developed temperature model of casting roll is helpful in optimising processing parameters and the design of casting roll during twin-roll thin strip casting.

Study of Force and Fracture of Impacted Diamond Grits

In this paper, toughness index of diamond was measured by Toughness Index Measurement Apparatus. Forces on diamond grits at different impact condition were analyzed theoretically. Post-impact diamond grits were divided into three ty p s by screening: un-broken, micro-fractured and completely fractured diamond, which correspond to fai lure modes: no significant wear, micro-fractured and macro-fractured in diamond tools. Thus the cor r lation between the fracture types of impacted diamond and its failure modes in diamond tool was established. The effects of impact parameters on the fracture types were also studied. The results show that fracture types of diamond grits are related to the steel balls mass and impact frequency. With the increase of steel ball mass or impact frequency, the ratio of un-broken diamond decreases and tha t of micro-fractured diamond increases gradually. Introduction Diamond abrasive is widely applied in advanced machining fields. To get the optimum machining quality and property of tool, the researches including wear mechanism of diamond grits and bond, the grinding temperature and grinding force have been carried out broadly [1 -4]. This provides important theoretic and practical foundation for selecting optimum diamond type and improving the tool’s efficiency and lifetime. In most of stone and construction applications, the diamond strength is an im portant parameter to evaluate its quality. Since diamond grits and their production are usual ly bjected to impact and abrasive wear during practical grinding process, the quality control device used for monitoring production has to simulate both forms of wear [5]. Toughness Index Measure ment Apparatus used to determine grits impact strength can meet the above requirement. H owever, in order to assess the application and properties of diamond, it is still worth deeply investig atin the relationship between the fracture types of impacted diamond grits and tools’ properties. T h present work is to analyze and discuss the force and fracture types of impacted diamond grits. Experimental and Results Fig.1 Schematic diagram of the toughness index measurement apparatus Fig.1 showed the schematic diagram of the Toughness Index Measurement Apparatus, whose vibration frequency can be adjusted accurately. Diamond grits together wit steel balls were placed into the sealed steel chamber, then the vibration frequency was set up a nd the steel chamber began to Diamond grits Steel ball Key Engineering Materials Online: 2003-09-15 ISSN: 1662-9795, Vol. 250, pp 68-72 doi:10.4028/www.scientific.net/KEM.250.68

Effect of Secondary Cooling on Non-Oriented Electrical Steel Strips Produced by Twin-Roll Casting Process

Effect of secondary cooling on non-oriented electrical steel strips was investigated. The 2.0 mm thick cast strips contain two compositions were produced by twin-roll casting process, cooled in the air or cooled by spraying water. The microstructure was observed by optical microscopy, and EBSD was used to characterize the texture of the cast strips. The results showed that air-cooling cast strips have uniform and equiaxed grains with average size of 250 μm. The microstructure of the water-spraying cast strips compose of most equiaxed grains and a small number of abnormal big grains. At the same time, the secondary cooling rate mildly affects the cast texture strength but has no influence on the texture type.

Casted Strip Character of Twin-Roll Casted High Strength Non-Oriented Electrical Steel

A twin-roll casting process was used to produce high strength non-oriented electrical steel casted strips. The typical character in chemical composition is the adding of Ni and Cr.The main role of Ni and Cr is solution strengthening. MEM, SEM, and TEM were used to observe microstructure, texture, and precipitate characteristics of a casted strip. The casted strip character under different secondary cooling process was compared. The results show that water-cooled as-cast strip is composed of the equiaxed grains, air-cooled as-cast strip is characterized by a mixture of the quiaxed and columnar grains. The texture of water-cooled as-cast strip is weaker and diffuser than air-cooled as-cast strip. Precipitates mostly are AlN and MnS, which mostly precipitate in the grain. The precipitates of Ni and Cr is not observed. The size distinction of MnS between two secondary cooling process is not remarkable. The size of AlN in water-cooled process is smaller than in air-cooled process.

Study on Surface Roughness Muring Metal Manufacturing Process

In the paper, a crystal plasticity finite element method (CPFEM) model was developed based on ABAQUS to analyse the surface roughness transfer during metal manufacturing. The simulation result shows a good agreement with the experimental result in the flattening of surface asperity, and the surface roughness decreases significantly with an increase of reduction with considering friction effect. Lubrication can delay surface asperity flattening. The effect of surface roughness on produced metal defect (crack) was also studied, and the surface roughness affects the crack initiation significantly in cold strip rolling. In addition, the surface roughness variation along the metal plate width contributes to stress distribution and then inhibition of crack nucleation.