Preface 免费阅读 下载全文
Physical modeling and numerical simulation of electromagnetic stirring in a slab continuous casting mold 免费阅读 下载全文 Through physical modeling and numerical simulation,the flow field in a slab continuous casting mold with electromagnetic stirring is measured under different casting parameters and stirring currents. To qualitatively evaluate the flow field in the mold,two indexes,i. e.,mold flux entrapment and velocity uniformity,are proposed.Based on these two indexes,some optimized stirring parameters under different casting conditions can be determined.
Numerical simulation of fluid flows in a slab continuous casting mold under electromagnetic stirring 免费阅读 下载全文 This study established a three-dimensional mathematical model to determine the fluid flowin a slab continuous casting mold under an electromagnetic stirring force. The flowstructure and distribution were studied with respect to different continuous casting parameters and stirring current. Based on the calculation results,the mold flux entrapment index in free surface and velocity uniformity index were used to evaluate the flowfield in the mold. The theoretical basis for the optimization of the flow field structure was provided. The study also suggested an optimization method for electromagnetic stirring parameters.
Effect of electromagnetic stirring on flow field in mold under submerged entry nozzle clogging 免费阅读 下载全文 A physical model with mercury as analog was developed to investigate the influences of electromagnetic stirring( EMS) on flow field in slab continuous casting when the submerged entry nozzle( SEN) was clogged with different clogging rates( 0,10%,25%,and 50%). The flow field in mold under different EMS currents( 0,40 A,and 60 A) was measured by an ultrasonic Doppler velocimeter. The results proved that the flow field in the mold was a typical double roll structure under non-clogging SEN. As the SEN clogging rate increased,the flow field structure was transformed from a double roll to asymmetry flow. When the clogging rate reached 50%,the up circulation disappeared on the clogged side. The zone under the meniscus near the narrow face was a non-flowing area. EMS could correct bias flowcaused by SEN clogging and improve the symmetry of the flow field during SEN clogging.
Progress on research of induction heating in Baosteel 免费阅读 下载全文 Owing to the development of newproducts and higher requirement of product properties,the current existing induction heating technology of Baosteel can no longer satisfy the newrequirements of the product line.Control of the induction heating temperature to an appropriate value is a key consideration in induction heating technology. To obtain acculturated temperatures,investigations were focused on the parameters of an induction heating system,including those of induction heating equipment and heating processes. In these investigations,computer simulation was used to model the induction heating process,followed by physical experimentation to verify and improve the simulation model; finally,optimized induction heating parameters were suggested. The use of computer simulations dramatically decreased physical experimental times,and the computed heating parameters were used to guide the physical experimentation and design of the product line; this increased the efficiency of subsequent investigations. This study focuses on the development of induction heating technology in Baosteel,which includes the overall induction heating technology used in manufacturing backup rollers and in the thermomechanical control process.
Mathematical modeling of induction heating of discard substitution block for billet hot extrusion process 免费阅读 下载全文 A magnetic and temperature field-coupled mathematical model is proposed to calculate the induction heating process of a discard substitution block for billet hot extrusion process. The mathematical model is validated by comparing simulation results with temperature measurements recorded during physical modeling. Based on systematical analysis of calculation results,a quantitative sawtooth induction power curve was proposed to realize the aim of achieving the best distributed temperature field in the block within the shortest induction time.
Variation microstructure and properties of X80 pipeline steel in the rapid induction tempering process 免费阅读 下载全文 A self-developed electromagnetic induction-heating device was used to investigate the variation in the microstructure and properties of X80 pipeline steel in the rapid induction tempering process at different process parameters. The effects of the tempering condition on toughness,microstructure,size and distribution of precipitates of X80 pipeline steel were observed using a metallographic microscopy and scanning electron microscopy.Compared with the samples prepared via traditional tempering techniques,results showthat the samples prepared via rapid induction tempering had improved performances. When the heating temperature is 590 ℃,at a holding time of90 s,it was found that acicular ferrite was refined,carbonite precipitation was small,and precipitates were evenly distributed in the matrix. The low-temperature impact energy,also known as the impact absorption energy,at- 40 ℃ was found to be 430. 5 J for the rapid induction tempering samples and 323. 2 J for the traditionally tempered sample. The low-temperature impact energy at- 60 ℃ was found to be 351. 3 J for the rapid induction tempered sample and 312. 1 J for the tradition tempering sample.
Delayed fracture of tensile strength 980 MPa grade steels for automotive applications 免费阅读 下载全文 Three different types of tensile strength( TS) 980 MPa grade advanced high-strength steels used in automotive applications,namely,980 MS( martensite steel),980DP( dual phase) and 980QP( quenching and partitioning) steels were examined. The delayed fracture resistance of the steels was evaluated using a U-bend test,slowstrain rate test( SSRT) and a constant load tensile test. The results indicated that all the steels could pass the300h HCl solution immersion test and none of the U-bend specimens was fractured in the test. However,the steels exhibited different susceptibilities to delayed fracture under SSRT and the constant load tensile tests. 980 DP exhibited the highest resistance to delayed fracture among all the samples,while 980 MS was found to be the most susceptible to delayed fracture.
Self-cleaning performance of a serf-cleaning pre-coated steel sheet in an industrial environment 免费阅读 下载全文 A type of self-cleaning pre-coated steel sheet with excellent self-cleaning performance was developed using hydrophilic surface treatment technology. To understand the self-cleaning properties of this pre-coated steel sheet in an industrial environment,the Jiangjin natural environmental test station was chosen as the outdoor exposure test to be conducted,and the self-cleaning performance of the steel sheet was studied by measuring the water contact angle,stain resistance factor,color difference,and gloss of the steel sheet during the outdoor exposure test. The water contact angle of the self-cleaning steel sheet quickly decreased from 84° to 29° during the outdoor exposure test,and the steel sheet showed excellent hydrophilic properties,which were beneficial to the spread of rain drops and detrimental to the accumulation of the surface pollutants. After an outdoor exposure of12 months,the self-cleaning steel sheet had a higher stain resistance and cleaner surface than the comparison sample sheet,demonstrating its excellent self-cleaning properties. M oreover,the color difference and gloss rate of the self-cleaning steel sheet were similar to those of the pre-coated steel sheet without hydrophilic surface treatment. Therefore,the hydrophilic surface treatment technology used in this study did not affect the anti-aging property of the self-cleaning steel sheet.