Comparative Study On Non-sinusoidal Oscillation Mode Performance Of Continuous Casting Mold

Non-sinusoidal oscillation is the most advanced continuous casting mold oscillation mode at present.In this paper,the non-sinusoidal oscillation mode of continuous casting mold is taken as the research object,and the new type of oscillation mode of keeping constant for a period of time waveform is studied.The optimum range of basic parameters and the method of establishing synchronization control model of waveform are put forward.The mechanical model of continuous variable cross-section cantilever beam is established for initial solidified shell at meniscus to analyze the effect of basic parameters of keeping constant for a period of time waveform on initial crack of initial solidified shell,and the optimization direction of basic parameters for reducing initial crack by wave is put forward.The keeping constant for a period of time waveform and other two non-sinusoidal waveforms are analyzed and compared.The main conclusions are as follows:(1)Based on the analysis of the influence of basic parameters of keeping constant for a period of time waveform on oscillation effect,a synchronous control model of the waveform is proposed,which sets equal-velocity stage factor according to the working condition.With the increase of casting speed,the amplitude decreases linearly,the amplitude increases linearly,and the waveform modification rate is controlled in stages,first decreases and then increases.Then by continuous casting low carbon steel([C]=0.04%)of the process conditions were validated,which showed that the synchronous control model could better control the keeping constant for a period of time waveform to meet the production needs.(2)Through the mechanical model of the cantilever beam of the initial solidified shell at meniscus,the stress state of the initial solidified shell under keeping constant for a period of time waveform is analyzed.It is found that the force on the initial solidified shell is obvious.When the stable casting speed vc=1.8 m/min,the downward oscillation speed is 6.4 m/min,the maximum bending tensile stress can reach 93.0 kPa,and the upward oscillation speed is 1.804 m/min,the maximum bending tensile stress can reach 109.8 kPa.The high temperature shell with critical fracture strength of 109.8 kPa is easy to be broken through under bending stress and crack defects occur.Therefore,the external initial crack of the initial solidified shell is not easy to be induced,and the initial crack can be reduced and the surface quality of slab can be improved by properly reducing the oscillation frequency and amplitude,increasing the waveform modification rate and the equal-velocity stage factor.(3)Compared with eight-segment waveform,five-segment waveform and four-segment waveform have good dynamic characteristics.The range of their basic parameters is larger.Increasing frequency,amplitude and waveform modification rate can not cause the maximum acceleration of waveform to be larger,while the dynamic characteristics of eight-segment waveform are relatively poor,the range of basic parameters is smaller,and increasing frequency,amplitude and waveform modification rate can cause the maximum acceleration of waveform to be larger,which will affect the stability operation of equipment and cause equipment damage.(4)The possibility of initial internal crack induced by eight-segment waveform is the least and easier to control the generation of initial crack,and the possibility of initial internal cracks induced by five-segment waveform and four-segment waveform is similar.In addition,three kinds of waveform can be by reducing the frequency and amplitude,and increase the waveform deviation to reduce the possibility of induced by the initial crack defects.(5)Under the same conditions,the initial solidified billet shell is subjected to the minimum tensile stress and maximum compressive stress caused by liquid friction at the time of eightsegment waveform.Therefore,it has a relatively strong ability to control the generation and healing of cracks and improve the surface quality of the billet.Five-segment waveform and foursegment waveform have similar ability to control crack generation,and the five-segment waveform has stronger ability to heal crack than four-segment waveform.(6)At low frequency,small amplitude and waveform modification rate,the oscillation mark depth control ability of five-segment waveform and four-segment waveform is similar and weaker than that of Eight-segment waveform.At high frequency,large amplitude and waveform modification rate,the control ability of oscillation mark depth of five-segment waveform and four-segment waveform differs little from each other,and is stronger than that of Eight-segment waveform.