潜流铸造方法及应用研究

发布时间：2018-01-16 00:16

本文关键词：潜流铸造方法及应用研究　出处：《大连理工大学》2017年博士论文　论文类型：学位论文

【摘要】：潜流铸造是一种新型铸造方法,它是一种动浇口、无浇道、数字化铸造新技术。在浇注充型过程中,浇口潜入到铸型内液面以下一定距离,并随着平稳上升的液面同步向上运动。在铸型中无需设计复杂的浇注系统,潜流铸造的浇注系统非常简单,仅需一根浇注管即可进行浇注充型,无需复杂的浇注系统,大大降低了铸造工艺设计、铸型制造及装配的难度,可用于浇注增材制造技术制备的覆膜砂铸型,以生产复杂形状的铸件。它基于CAD实体造型、分层切片技术、流体贝努利方程等,通过迭代计算快速获得液面上升的位移-时间曲线(充型过程的控制曲线)。然后,根据计算所得的过程控制曲线,浇口在计算机/变频器控制下进行提升运动,直至完成整个充型过程,充型过程可精确控制。为了对潜流铸造方法进行深入系统的研究,设计开发了一套可移动的潜流铸造装备,装备的设计开发主要包括装备结构、浇注系统、计算软件及控制系统等多个方面,原创性较高。该装备可以进行水模拟PIV检测、高温金属液(如铸铝、球墨铸铁等)浇注等试验,基本满足了在实验室进行基础研究以及铸造车间进行铸件浇注试验的需要,为进行后续的研究和应用提供了可靠的保障。基于PIV水模型试验、数值模拟仿真及铸件浇注试验等方法,研究了潜流铸造的充型状态和流场分布的特征。在潜流铸造充型过程中,浇注管内充满液体,将空气隔绝于外,可有效减少气孔等铸造缺陷。铸型内已浇注的液体可以分成三个基本区域:(a)平稳液面:铸型内液面平稳缓慢上升,液面保持完整未被水流冲击破坏,可以有效减少在液面形成氧化物薄膜并将其卷入已浇注液体的几率;(b)出流区:在导流阀的作用下,流体侧向出流,流速从浇口到铸型逐步降低,对铸型冲击变小,可有效减少冲砂等铸造缺陷的形成几率;(c)平稳区:除了侧向出流区以外,其余区域液体流速很小,液体基本保持平稳状态,并且由于浇口距液面距离较小,当低密度夹杂经导流阀侧向流出后,容易上浮到液面上,随着液面平稳缓慢上升。铝合金是常用铸造金属材料,ZL102和ZL203分别是窄、宽凝固区间的铸铝合金,铸造性能差别很大。充型方法的不同对合金的充型能力和冒口的补缩效果影响明显,顶注充型时,铸型内流场紊乱,铸件的充型效果波动很大。底注充型时,随着液面的上升,液面附近金属液的温度场逐渐降低,铸件的充型能力随之减弱。潜流铸造在充型时,铸型内液面平稳缓慢上升,浇口出流区域即液面附近区域温度较高,随着充型的持续进行,逐步形成"上热下冷"的温度梯度。与顶部浇注相比,潜流铸造的充型状态更加平稳,充型能力更加稳定,补缩效果也更为理想;与底部浇注相比,潜流铸造的充型能力不随液面的上升而减小,补缩能力也更强,无论对于ZL102还是ZL203,潜流铸造均可以有效改善铸件的充型能力和冒口的补缩效果,铸件的力学性能也更好。为了研究球墨铸铁的凝固特征,将高品质球墨铸铁以不同的温度注入到覆膜砂铸型中,铸造试验结果表明:冒口设计及工艺控制非常复杂,不合理的设计或工艺控制会诱发缩孔缩沉等缺陷;若铁水的浇注温度降低到一定值,凝固过程中利用石墨的膨胀即可进行有效补缩,而无需采用冒口对铸件进行补缩。基于潜流铸造技术,采用温度较低的球墨铸铁铁水,对增材制造法制备的复杂形状覆膜砂铸型进行快速浇注充型,有效的利用了石墨膨胀对凝固收缩的补缩作用,避免铸件产生缩孔缩松缩沉等缺陷,最终获得外观良好、尺寸精确、内部致密、金相组织及力学性能良好的铸件,实现了复杂形状球墨铸铁件的无冒口铸造。
[Abstract]:Flow casting is a new casting method, it is a gate, no runner, the new technology of digital casting. In the mould filling process, the gate into the mold surface below a certain distance, and with the level of a steady increase in synchronous upward movement in the mold. Without the gating system design was complex. Flow casting pouring system is very simple, only a pouring pipe can be carried out without casting mould filling, complex system, greatly reduces the casting process design, mold manufacturing and assembly difficulty, can be used for coated sand mold casting additive manufacturing preparation technology, to produce complex shape castings. It is based on CAD solid modeling, slicing technique, fluid Bernoulli equation, through iterative calculation rapidly and obtain the displacement time curve (the rise of the liquid level control curve of the filling process). Then, according to the process control curve calculated, pouring In the computer / converter under the control of the ascension movement, until the completion of the whole filling process, filling process can be controlled accurately. In order to study the flow casting method in-depth system, designed and developed a set of subsurface removable casting equipment, the design and development of equipment including equipment structure, gating system, multi aspects the calculation software and control system. The original high equipment can detect the simulation of water PIV, high temperature liquid metal (such as aluminum, ductile iron casting) test, to meet the basic needs of basic research and foundry casting was carried out in the laboratory test, to provide a reliable guarantee for the subsequent research and application PIV water. Based on the model test, numerical simulation and experimental research methods such as casting, casting filling subsurface flow state and flow distribution characteristics. Flow casting filling in submarine In the process of pouring pipe filled with liquid, the air is isolated, which can effectively reduce the casting defects such as pore. The mold has been pouring liquid can be divided into three basic areas: (a): smooth surface mold surface smooth slow rise level to maintain the integrity of water impact is not broken, can effectively reduce the formation of oxides the film on the surface of the liquid and the liquid pouring has been involved in probability; (b) flow area: in the diverter valve under the action of lateral fluid flow, flow rate decreased gradually from the gate into the mold, the mold small impact, can effectively reduce the sand casting formation probability made defects; (c) stable region in addition, lateral flow outside the zone, the remaining area of liquid flow rate is small, the liquid remained steady state, and the gate from the surface when the distance is small, low density inclusion through the guide valve lateralflow, easy to float to the surface, with the surface smooth aluminum alloy increased slowly. Gold is commonly used in casting metal materials, ZL102 and ZL203 are narrow, wide range of cast aluminum alloy solidification, casting properties vary greatly. Effects of feeding effect of filling method on different alloy filling ability and riser obviously, top injection filling, mold filling flow disorder, the effect of casting large fluctuations at the end of the filling. Note, as the liquid level rises, the temperature field near the surface of molten metal is gradually reduced, the filling ability of castings decreased. Subsurface flow during filling of casting, casting the liquid level in the steady rise slowly, the gate flow region near the surface region of high temperature, with the filling continued, gradually the formation of "temperature gradient hot cold. Compared with the top pouring, filling flow casting filling capacity is more stable, more stable, feeding effect is more ideal; compared with the bottom pouring, filling ability of casting with liquid flow. L decreases, the feeding ability is stronger, whether for ZL102 or ZL203, feeding effect of subsurface casting can improve the mold filling ability and riser, the mechanical properties of castings are better. In order to study the solidification characteristics of nodular cast iron, the high quality ductile iron with different temperature into coated sand the mold, casting test results show that the riser design and process control is very complicated, can cause shrinkage defects such as sink design or process control is not reasonable; if the casting temperature is reduced to a certain value, effective feeding by graphite expansion to the solidification process, without the use of casting riser feeding. Subsurface flow casting technology based on the low temperature ductile iron casting, rapid filling of complex shape of the coated sand mold additive manufacturing preparation, effective use of expanded graphite on solidification shrinkage The shrinkage effect can avoid shrinkage defects such as shrinkage porosity, shrinkage and settlement, and finally obtain castings with good appearance, precise size, dense inner surface, good metallurgical structure and good mechanical properties, and achieve the riser free casting of complex shape nodular iron castings.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG24

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