共查询到16条相似文献,搜索用时 140 毫秒
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采用数值模拟方法,研究ZTC4合金机匣离心铸造的充型和凝固过程,分析了离心转速、浇注温度和铸型预热温度对熔体充填过程流动场、凝固过程温度场和应力场的影响,并预测了缺陷的分布.结果表明,随离心转速提高,熔体充型速度无明显变化,但柯氏力作用更加明显,铸型中熔体流股变细;熔体过热度低于30℃时,铸件出现明显的浇不足缺陷;铸型预热温度是影响铸件残余应力的主要因素,而离心转速和熔体过热度的影响次之;铸件最后凝固的较厚部位容易出现缩松、缩孔缺陷,且其位置与X射线检测结果较吻合. 相似文献
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电磁驱动熔体流动与枝晶变形断裂模拟 总被引:4,自引:1,他引:4
建立了电磁离心凝固过程熔体动量传递、传热和传质耦合数学模型,模拟计算了熔体在不同感应强度下的流动速度。计算结果表明,熔体在电磁力的作用下产生与铸模转动方向相反的流动,流动速度呈周期性分布,并且在凝固前沿达到最大,随着磁感应强度的增加,熔体流动速度达到的最大值也愈大,使用有限元软件ANSYS,把熔体流动计算结果作为参数,计算了枝品的受力状态,通过计算表明,熔体流过枝晶会在枝晶周围产生很大的速度变化,流体对枝晶的冲刷可使枝晶产生机械折断,电磁搅拌通过增加断裂枝晶数量促进柱状晶-等轴晶转变。 相似文献
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低过热度浇注弱电磁搅拌下半固态Al-30Si合金凝固特性分析 总被引:5,自引:1,他引:4
在凝固理论框架下充分揭示搅拌作用下合金凝固及颗粒形核和生长规律,对深入理解电磁搅拌条件下合金凝固组织形态演化过程具有重要意义.从搅拌对合金熔体运动状态的影响、低过热度浇注、弱电磁搅拌对形核的影响等角度对Al-30Si合金的凝固过程进行了理论分析.分析结果表明,搅拌时液态熔体的切向速度分量占主导地位,轴向和径向分量与切向分量相比很小,可视为零;在低过热度浇注、弱电磁搅拌过程中,低过热度浇注直接导致形核率大幅增加、电磁搅拌间接导致形核率急剧增加. 相似文献
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《金属功能材料》2017,(5)
研究了不同熔体处理方法(普通电磁搅拌、化学细化法和环缝式电磁搅拌)对挤压铸造7075铝合金凝固组织及力学性能的影响规律。研究结果表明,环缝式电磁搅拌熔体处理技术显著减弱了普通电磁搅拌所固有的集肤效应对合金凝固组织的影响,增加了熔体所受的平均剪切速率,同时增加了单位体积熔体的散热面积,促使合金熔体的温度场和成分场更加均匀,有利于熔体"凝固初期晶核"瞬间大量生成,有利于获得细小均匀的凝固组织。对合金熔体同时进行环缝式电磁搅拌和添加Al-Ti-B化学细化剂处理,挤压铸造的7075铝合金显微组织变得更加细小、均匀、圆整,晶粒尺寸缩小为69μm,形状因子达到0.62。同时有效地提高了合金的力学性能。 相似文献
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《特种铸造及有色合金》2015,(1)
研究了螺旋式环缝电磁搅拌熔体处理技术对7075铝合金凝固行为的影响,分析了不同搅拌电流和浇注温度对合金凝固组织的影响。结果表明,螺旋式环缝电磁搅拌熔体处理技术可以使合金熔体在电磁搅拌条件下受到强剪切处理,剪切速率很大,在整个熔体体积内实现熔体的周向、径向和轴向的运动,最终得到整个熔体体积內均匀分布的温度场和成分场。相比于普通铸造,螺旋电磁搅拌条件下,可以实现7075铝合金的强制均匀凝固,合金凝固显微组织分布均匀细小。随着搅拌电流的增大晶粒组织变得更加细小均匀,当搅拌电流增大到30A时,凝固组织变化不大;随着浇注温度的升高晶粒组织变得粗大、枝晶化,但是相比普通铸造,晶粒组织对浇注温度的依赖性减弱。 相似文献
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EFFECT OF ROTATING MAGNETIC FIELD ON MACROSTRUCTURE OF A CENTRIFUGAL CASTING Al-1%Cu ALLOY 总被引:1,自引:0,他引:1
1. IntroductionCelltrifugal casting has been broadly used as it offers many advantages over the conventional casting methods. In a celltrifugal casting process, liquid metal is introduced intoa die that is spinning at a high rotational speed. The metal will take the shape of the dieand be subjected to a force 40 to 50 times of gravityg which then usually makes the castmore dense. The cast is also very clean, since the non-metallic inclusions that are presentin the liquid metal are celitrifuged… 相似文献
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A two-dimensional simulation model for melt flow and solidification in centrifugal precision casting has been developed based
on experimental results on melt flow in a precision casting tree for Ti-6A1-4V alloy castparts. The amount of liquid alloy
is intentionally adjusted to be less than that required for complete filling and is poured under a centrifugal force. The
melt flows into mold cavities keeping contact with the vertical inside walls of the cavity in the anti-rotation side, and
solidifies directionally by accumulating a solidified layer from the far end of the cavity to the gate according to the gradient
of centrifugal force. The model reproduces melt flow observed in casting trials and directional solidification during centrifugal
casting. In addition, it has been confirmed that the centrifugal force imposed on the melt enhances removal of defects caused
by entrapment of gas bubbles or by solidification shrinkage and improves mechanical properties of the castparts.
Formerly Graduate School of Iron and Steel Technology Pohang University of Science and Technology San 31 Hyoja-dong, Namku,
Pohang 790-784, Korea 相似文献
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The as-cast microstructures of high carbon high speed steels (HC-HSS) made by sand casting,centrifugal casting and electromagnetic centrifugal casting, respectively, were studied by using of optical microscopy (OM) and D/max2200pc X-ray diffraction. The results show that the microstructure of as-cast HCHSS is dominated by alloy carbides (W2C, VC, Cr7C3), martensite and austenite. The centrifugal casting and electromagnetic centrifugal casting apparently improve the solidification structure of HC-HSS. With the increase of magnetic intensity (B), the volume fraction of austenite in the HC-HSS solidification structure increases significantly while the eutectic ledeburite decreases. Moreover, the secondary carbides precipitated from the austenite are finer with more homogeneous distribution in the electromagnetic centrifugal castings. It has also been found that the lath of eutectic carbide in ledeburite becomes finer and carbide phase spacing in eutectic ledeburite increases along with the higher magnetic field strength. 相似文献
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为了提高高铬铸铁衬板的力学性能,使用电磁离心铸造浇注,并和常规重力离心铸造的试样进行了对比。结果表明,电磁离心铸造获得的试样组织明显细化,晶粒数量增多,晶粒尺寸细小,力学性能提高。当离心转速为1500r/min,磁感应强度为0.5T时,电磁离心铸造铸态试样的硬度(HRC)为55.3,冲击韧度为6.87J/cm2;热处理后的硬度(HRC)为65.3,冲击韧度达到7.3J/cm2。试样硬度比常规铸造试样提高了约10%,冲击韧度提高了约9%,相对耐磨性提高了约5%。 相似文献
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采用移动磁场铸造薄壁铝合金流动试样,并对移动磁场铸造过程中铝合金熔体内的电磁力各分量的瞬时值及其对铸件表面质量的影响进行了理论分析。结果表明,随着磁感应强度的增加,铸件的表面粗糙度有增加的趋势,这在采用金属上型时表现更明显。由于通人电磁感应器的三相非平衡电流在铝合金熔体内所产生的电磁力是脉动的,其大小呈周期性变化,尤其是垂直于磁场运动方向上的电磁力,其脉动的幅度很大。由此认为,所产生的垂直于磁场运动方向上的脉动电磁力是引起熔体表面震荡起伏和导致铸件凝固后表面粗糙的主要原因。 相似文献