共查询到19条相似文献,搜索用时 343 毫秒
1.
连铸机结晶器向下运动的速度超过拉坯速度时,铸坯对结晶器产生相对的向上滑动,此滑动称为负滑动(或负滑脱)。负滑动将使坯壳受压,有利于被拉断坯壳的愈合。 正弦振动的结晶器,速度变化平稳,可采用高频振动,有利于脱模,同时结构简单,因此近年来在连铸机上得到广泛的应用。正弦式振动比其他型式振动的负滑动时间要短,如果参数选择不当,可能不出现负滑动。负滑动的性能取决于结晶器振动频率和振幅,以及拉坯速度的大小。本文就正弦振动的结晶器,对这些参数的内在规律进行理论性探讨。 相似文献
2.
结晶器非正弦振动在有效避免黏结性漏钢的同时,可以获得较短的负滑动时间,有助于提高铸坯表面质量。非正弦振动的加速度比正弦振动大,容易产生冲击,降低结晶器运动的平稳性。针对此问题,构造了一种新型非正弦振动波形函数,其加速度可以根据实际情况给定,以保证良好的波形动力学特性。此波形函数可以在恒定的加速度下,通过增加波形偏斜率来减小负滑动时间,在增强非正弦振动特征的同时,不影响结晶器振动平稳性;另外,在恒定的波形偏斜率下,可以通过减小振动加速度来减小负滑动时间,在增强振动平稳性的同时,提高铸坯表面质量。通过对振动工艺参数的分析,给出了各工艺参数的计算方法,绘制了多工艺参数等值曲线,为拉速-频率同步控制模型的确定提供了参考。 相似文献
3.
4.
5.
结晶器非正弦谐振技术的开发与应用 总被引:1,自引:0,他引:1
研究了非正弦振动发生装置。构造了非正弦振动的波形函数,开发了非正弦振动发生装置和结晶器谐振技术,给出了最佳谐振弹簧力的计算方法。针对首钢大板坯连铸机,优化了非正弦振动的工艺参数,减小了负滑动时间和最大相对速度差,增加了负滑动率、正滑动时间和负滑动量。此技术应用于首钢板坯连铸机,且对采用非正弦振动和正弦振动的两流铸坯进行对比分析。结果表明,此非正弦振动技术在减少粘结性拉漏、减少表面裂纹及减轻表面振痕、提高铸坯表面质量等方面均取得了明显效果。 相似文献
6.
7.
8.
连铸结晶器瞬态摩擦阻力的实验研究 总被引:1,自引:0,他引:1
应用连铸结晶器凝固综合模拟装置,研究了结晶器瞬态摩擦阻力随结晶器振动的变化规律。结果显示在结晶器上部,连铸坯与结晶器之间以粘性摩擦为主,摩擦阻力的变化规律与结晶器振动的速度波形一致。应用结晶器非正弦振动,在保证负滑动期间对初始凝壳的压缩作用的同时,可以大幅度降低正滑动期间的结晶器摩擦阻力。这对防止高速连铸初始坯壳的拉裂、提高拉坯速度有重要意义。 相似文献
9.
10.
《冶金自动化》2016,(6)
伺服电动机驱动的连铸结晶器非正弦振动控制系统采用伺服电动机及相应的驱动控制器代替原工业现场的普通交流电动机,进而通过偏心轴连杆机构驱动连铸结晶器实现非正弦振动。由于伺服电动机按单方向、变角速度规律连续转动,因而具有节能降耗的优点。该控制系统采用S7-400 PLC+FM458高速高性能控制模块作为控制核心,以实现连铸结晶器非正弦振动波形的准确输出和跟踪。结晶器实时跟踪曲线和酸洗试验结果的比较表明,所设计的连铸结晶器振动控制系统运行平稳,铸坯表面质量得到显著改善。该控制系统适用于普通交流电动机通过偏心轴连杆机构实现的正弦振动到非正弦振动的技术改造,且保留了正弦振动的功能。 相似文献
11.
12.
《钢铁研究学报(英文版)》2016,(9):900-909
A mathematical model to show the dynamic response of the mold oscillator was suggested.The model con-sidered a frictional interaction between the mold oscillator and slab as several connected nodes.The governing equa-tion considered the slab as a multi-degree-of-freedom (DoF)system,and included a hysteresis model to describe elastic-plastic behavior of the slab;the mold oscillator was given two DoF by utilizing pressure and displacement ex-periment data.Simulations indicate that the mold and slab execute various vibrations,and that mold oscillation marks are caused by a stick-and-slip phenomenon during intervals,in which the slab contacting the mold moves downward compared to the other slab (negative strip time).The slab shows the formation of mold oscillation marks to previous formation criterion equally when the mold velocity is faster than the casting speed about downward.The oscillation mark will grow up over 2 Hz exciting frequency with constant 4 mm stroke in simulations.Finally,the negative strip time was compared to the frictional force,hysteresis variable,and plastic force to investigate forma-tion mechanism of the oscillation marks. 相似文献
13.
14.
15.
16.
《Canadian Metallurgical Quarterly》1999,38(5):295-300
Consistent and uniform lubrication in the mold during casting is an issue especially with high speed casting. However, criteria of mold oscillation related to lubrication, has not been clarified for critical conditions such as thin slab casting. This paper discusses the mechanism of powder penetration into the meniscus, in terms of negative strip area ratio and positive strip time, including the case of non-sinusoidal oscillation which is effective for better mold lubrication. In this context, a lubrication index is proposed as a new criteria which can be used to estimate mold powder consumption rate. 相似文献
17.
18.
Dong Zhou Wanlin Wang Haihui Zhang Fanjun Ma Ken Chen Lejun Zhou 《Metallurgical and Materials Transactions B》2014,45(3):1048-1056
The initial shell solidification of liquid steel in the mold has significant influence on both surface and internal quality of the final slab, and it is mainly determined by the high transient high temperature thermodynamics occurring in the mold. This study investigated the effects of casting parameters like casting temperature, mold oscillation frequency, and stroke on the initial solidification of a Sn-Pb alloy through the use of a mold simulator to allow the clear understanding of the inter-relationship between irregular shell solidification, heat transfer, negative strip time (NST), and casting conditions. Results suggested that the shell surface oscillation marks (OMs) are strongly depending upon the fluctuations of meniscus responding temperatures and heat flux. An abrupt sudden fluctuation of high frequency temperature and heat flux at the meniscus during the NST would deteriorate the shell surface and leads to deep OMs. The fluctuations of responding temperature and heat flux are determined by the NST, meniscus solidification, and oil infiltration, which in turn are influenced by casting conditions, like casting temperature, oscillation frequency, stroke, etc. 相似文献