7075铝合金Ф482 mm铸锭热顶铸造工艺试验研究

为满足市场对大规格高强度铝合金材料的需求,对7075铝合金Ф482 mm圆铸锭的热顶铸造工艺进行试验研究。从原料选用、成分调整、熔炼温度控制、导炉、铸造工艺参数等多个环节进行控制,制得表面光滑的铸锭。对铸锭取样进行化学成分分析和低、高倍组织检查,结果表明热顶铸造制得的铸锭表面质量、内部组织、化学成分偏析情况比传统铸造方法均有改善,更能满足用户的要求。     

低频电磁热顶铸造7050铝合金铸锭的表面质量和组织

在传统热顶铸造基础上,开发了一种新的热顶铸造结晶器,并在铸造过程中施加低频电磁场;得出了稳定铸造φ500mm 7050高强铝合金铸锭的工艺条件,当电磁场频率为15 Hz、磁场强度为10000 A/m时,铸造出了表面光滑的铸锭.采用偏光显微镜(Leica DMI)观察试样,分析试样的微观组织.试验结果表明:铸造过程中施加低频电磁场能提高铸锭的表面质量,细化铸锭的内部组织,抑制铸锭内部裂纹的产生.总结了低频电磁铸造改善表面质量和细化组织的原因以及低频电磁场对液穴形状的影响.     

绝热模铸造法试验总结

采用直接水冷半连续铸造法(D.C法)生产铝合金铸锭已有半个世纪了.这种方法和铁模铸造相比优点甚多,但是半连续铸锭的表面易于产生偏析瘤、拉痕和冷隔等缺陷,在继续加工以前不得不进行车皮,其车屑量竟达6-7%.这是不可忽视的损耗.文献对上述缺陷形成的机理进行过研究,指出:这些缺陷的产生与熔体金属同模壁的接触有关,若采用控制铸模的热传导或无接触铸造法,会使这些缺陷减小或完全消除.在研究产生缺陷机理的同时设计、试验和使用了多种铸造法,如热顶铸造、绝热模和电磁铸造等.     

半连续铸造铝合金表面缺陷的形成机理及影响因素

介绍了半连续铸造铝合金锭坯冷隔、皮下偏析层、表面偏析瘤、拉痕等表面缺陷的特点和形成机制。分析了在半连续铸造铝合金锭坯过程中结晶器结构、铸造工艺参数对这些表面缺陷的影响及作用机理。在此基础上总结了提高铸锭表面品质的技术发展和工艺优化方向。     

2A12铝合金Φ110mm铸锭热顶铸造工艺研究

为了提高2A12铝合金的Φ110 mm铸锭质量,采用热顶铸造进行试验研究。结果表明,2A12铝合金的熔炼温度控制在700℃~750℃,铸造温度在700℃~720℃,铸造速度在140 mm/min~160 mm/min,在铸造过程中采取有效的在线净化装置进行除气,并对铸锭进行480℃~495℃10 h的均匀化退火,能生产出组织和性能满足用户要求的铸锭。     

热顶铸造结晶器设计对铸锭质量的影响

介绍采用热顶铸造法生产铝合金圆铸锭的优点、对热顶铸造结晶器的要求及它的结构组成。为了生产出各种规格的优质铝合金铸锭,在多年试验和生产实践的基础上,总结出针对不同直径圆铸锭所用热顶铸造结晶器的合理设计参数——结晶器高度、热顶帽高度、结晶器内衬高度、石墨环高度、进水孔和出水孔尺寸及出水角度等。     

2A14铝合金大铸锭半连续铸造过程数值模拟

基于ProCAST模拟软件建立了?630mm的2A14铝合金半连续铸锭的有限元模型,根据ProCAST热力学数据库确定了2A14铝合金热物性参数及力学性能参数,定义了半连续铸造过程的边界条件,采用移动边界法对半连续铸造凝固过程进行了模拟。仿真结果表明,铸锭内外冷却速率差过大而导致的较大收缩应力差是产生热裂纹的主要原因,适当降低铸造速度和浇注温度并增加冷却强度将使液穴变浅,糊状区变深,减少铸锭内外收缩应力差,从而降低热裂纹产生倾向。     

5056铝合金圆锭表层偏析对挤压管材的影响

以热顶半连续铸造生产的5056铝合金圆锭为例,根据工业上铝合金管材实际生产工艺流程,使用金相分析、直读光谱分析及电子扫描分析,研究了铸锭表面偏析层对均匀化热处理、挤压加工及阳极氧化的影响。结果表明,铸锭的表层化学成分及相组成与心部的有较大差异;在对其进行520℃7 h均匀化退火后,铸锭心部均匀化效果较好,但是铸锭表层发生轻微的过烧;挤压生产过程中偏析层会卷入挤压制品表面,经过阳极氧化会产生氧化色差。     

热顶模直接水冷连续铸造有色金属合金圆锭的热传导条件及冷隔形成机理(1)

表面缺陷的存在及其严重性,例如直接水冷连继铸造产品中出现的冷隔,在很大程度上取决于模子热传导条件。在水平连续铸造直径20毫米的铅、锡、锌合金棒时,研究了热顶连续铸造模的热传导条件对冷隔形成机理的影响。冷隔的形成有两个阶段:界面控制凝固与随后的扩散控制凝固。用热顶模铸造时,有效热传导常数非常大,相当于直接水冷铸造。采用了一种稳态数值凝固法进行试验,结果发展了冷隔形成的临界铸造速度概念。如果实际铸造速度大于这个临界速度,就不能产生冷隔。换句话说,如果提高模子温度,降低模子的有效热传导常数,或实际上显著提高液体金属温度,就能使临界铸造速度降低,冷隔也可以消除。     

小直径空心铸锭同水平热顶多模铸造的研究

同水平热顶多模铸造,是新近发展起来的铝合金半连续铸造新工艺,在国外已经广泛应用于小直径实心圆铸锭的生产。这种工艺所生产的铸锭,不仅表面光滑和内部组织良好,而且工艺塑性很高,有利于提高熔铸和挤压生产的经济效益。本文探索了用同水平热顶多模铸     

板坯高拉速的研究与实践

连铸机的高拉速生产是大幅度提高连铸生产效率的最有效措施之一。为了解决连铸中间包寿命低与连铸机拉速慢而导致炉机不匹配的问题,从中间包寿命提高与拉坯速度调控两方面入手,通过优化设备结构与提高连铸机效率两种手段对生产工艺进行优化。结果表明,整体工艺优化后可以大幅提高炉机匹配能力,加快钢水消耗,并提高了连铸机的生产效率,为高效连铸打下了坚实基础。     

Effects of casting speed on microstructure and segregation of electromagnetically stirred Aluminum alloy in continuous casting process

Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry.In this study a hypo-eutectic Al alloy was fabricated by means of an electromagnetic stirrer in continuous casting process and the microstructural change during solidification due to a fluid flow by electromagnetic stirring was examined.Due to the forced fluid flow during solidification a dendritic phase of primary α phase of Al alloy was turned into a globular phase, which can make the Al alloy get a thixotropic behavior in the semi-solid region.In order to establish the quantitative relationship between microstructure and the process parameters, the morphology shape, a silicon distribution and a size of primary α phase were observed according to casting speed in continuous casting machine.The primary α phase was turned into the degenerate dendrites approaching a spherical configuration with increasing casting speed.The fine-grained and equiaxed microstructure appeared at higher casting speed.A segregation behavior of Si element was declined with increasing casting speed and a very uniform distribution of Si element was observed on the billet at a casting speed of 600 mm·min-1.A thickness of the solidifying shell of the billet was shortened with increasing the casting speed.     

Effect of electromagnetic casting process on microstructure and properties of AZ31 magnesium alloy

ABSTRACT

In this paper, AZ31 magnesium alloy is cast by applying the semi-continuous casting process with a low-frequency electromagnetic field. By studying the influence of electromagnetic field frequency, excitation current intensity and casting velocity on the microstructure and mechanical properties, the optimum process under oil-slip electromagnetic casting conditions was determined to improve the degree of grain refinement, yield strength, elongation and tensile strength of AZ31 alloy. An improved microstructure refining effect and higher hardness can be obtained with a current intensity af 60 A. The microstructures and mechanical properties obtained for different casting velocities of V = 200 mm/min and V = 230 mm/min at processing parameters of f = 30 Hz and I = 120 A were compared. Our results suggest that a higher casting speed does not lead to grain refinement or improved mechanical properties. Frequency     

Twin-roll strip casting of magnesium alloys in China

The development status of twin-roll strip casting for magnesium alloys in China was summarized as well as the new progress when several kinds of twin-roll strip casting technologies were developed and used.Horizontal twin-roll casting (HTRC) of magnesium alloys has attracted much attention and has been industrialized in China.Vertical twin roll casting(VTRC) of the magnesium alloys can reach a speed of higher than 30 m/min and its research and development are just beginning and exhibit exciting potential...     

应用PMO提高连铸坯生产拉速及成分均匀性

为了实现电炉厂提产增效的目标,研究了脉冲磁致振荡(PMO)在提高铸坯生产拉速中的应用潜能。结果表明,优化PMO处理参数可以适应生产拉速提高的要求,并改善铸坯的中心偏析和宏观偏析。当连铸拉速提至1.05 m/min,PMO脉冲频率为1.16K_f Hz,峰值电压为1.00K_iV处理参数(K_f和K_i分别为仪器的放电频率和电压峰值)时, 铸坯横断面碳偏析指数可控制在1±0.05内;当连铸拉速提至1.15 m/min,PMO脉冲频率为1.28K_fHz,峰值电压为1.00K_iV处理参数时,铸坯横断面碳偏析指数可控制在1±0.07内。试验证明,在高拉速条件下通过保证单位时间内对钢液施加的脉冲能量可以使连铸坯质量得到有效改善。     

拉速对板坯倒角结晶器钢液流动的影响

为研究凝固坯壳影响时拉速变化对板坯倒角结晶器内流场和温度场的影响,通过数值模拟和物理模拟研究相结合的方法,建立了板坯倒角结晶器流动、传热及凝固三维数学模型和相似比为1∶1的断面尺寸为1 490 mm×230 mm的板坯倒角结晶器物理模型。数值模拟和物理模拟流场形态及液面相同位置流速结果进行的对比分析表明了数模和水模试验结果趋势的一致性;拉速变化对倒角结晶器内流场及温度场的数值影响明显,但对整体形态影响不大;拉速增大到1.7 m/min时液面流速过快、波动剧烈,极易出现卷渣;拉速增大会强化钢液流股对窄面凝固坯壳的冲击,导致坯壳重熔减薄;在本试验研究范围内以1.5 m/min拉速进行生产能够取得较好的综合效果。     

Numerical simulation on direct chilled continuous casting process for preparing clad slab of aluminium alloys

The numerical simulation is used to investigate the influence of processing parameters on direct chilled continuous casting process for preparing clad slab of Al–1Mn and Al–10Si alloys. In order to get a clear bonding interface avoiding unexpected mixing, a special dividing plate is set between molten clad materials. The effects of cooling intensity and cooled part height of dividing plate, casting speed and pouring temperature on the temperature field, liquid fraction, and solidification shell of clad slab have been studied in detail. A practical experiment has been done based on the simulation studies. It was found that a clad slab with excellent metallurgical bonding can be obtained when the cooling water flow of dividing plate is 250 L h^?1, the cooled part height of dividing plate is 20 mm, the casting speed is 80 mm min^?1 and the pouring temperatures of Al–1Mn and Al–10Si alloys are 710 and 670°C respectively.     

Effect of casting speed on surface quality of horizontal direct chill casting 7075 aluminum alloy ingot

7075 aluminum alloy ingot with the diameter of 100 mm has been produced by hor-izontal direct chill casting in different casting speed. The effect of the casting speed on the ingot surface and subsurface layer was studied by surface observation and subsurface structure analysis. It was found that increasing the casting speed results in the adding of segregation knots in the ingot surface. The thickness of the dendrite microstructure layer in the subsurface reduces with increasing the casting speed. And the ...     

马钢低碳钢板坯高拉速连铸技术的应用

为了进一步解决连铸高拉速条件下的板坯质量问题,马钢有针对性地开展了低碳钢板坯高拉速连铸技术研发工作。通过采用高效连铸防粘结技术、高效强冷结晶器控制技术、低黏度保护渣优化控制技术、水口堵塞控制技术、动态二冷凝固控制技术等技术措施,解决了高拉速条件下出现的坯壳凝固不均匀、结晶器卷渣、铸坯质量等技术难题;稳定提升1 200 mm宽断面(厚度230 mm)低碳钢铸坯拉速至1.8 m/min;拉速由1.6提至1.8 m/min之后,炉均可减少浇铸时间2.5 min,连铸平均连浇炉数达到6炉以上。技术改进后,有效缩短了浇铸周期,提高了生产效率。     

ANSYS软件在连铸过程中的应用

连铸冶金过程非常复杂且伴随着高温,运用人眼法、物理试验法等传统的研究方法难以观测,数值模拟技术恰能弥补这一不足。有限元软件ANSYS以准确、安全、可靠等优点被广泛应用到连铸上。主要介绍了ANSYS在连铸中的研究现状,详细讨论了ANSYS在连铸钢包、中间包、结晶器、二冷区、空冷区中的应用。最后,为了使ANSYS与连铸更好地结合,指出了ANSYS在连铸中的发展趋势。