共查询到20条相似文献,搜索用时 125 毫秒
1.
建立双源超声铝合金铸造熔池模型,利用fluent软件模拟相同频率与不同频率下相位差对熔池声场的影响。仿真结果显示,相同频率下,相位差显著影响熔池声场的分布,随相位差增大,熔池空化域变小;不同频率下,相位差对熔池声场的分布无影响。通过不同相位差双源超声铸造试验发现,同频率振动下,相位差对双源超声铸造边部及超声辐射区的晶粒细化效果影响很小,心部晶粒细化效果随相位差变大效果变差;不同振动频率作用下,相位差对铸锭细晶效果无影响,心部晶粒细化效果与同频率相位差为90?时接近。同频率相位差0?超声作用下,铸锭心部晶粒尺寸较常规不同频率双源超声作用下心部晶粒尺寸大幅减小。 相似文献
2.
3.
高频拉铸工艺对锡磷青铜铸坯品质的影响 总被引:1,自引:0,他引:1
研究了生产锡磷青铜采用短节距、高频率以及二次反推的牵引制度的高频拉铸工艺.结果表明:高频拉铸工艺可以细化铸锭晶粒、减少成分偏析和枝晶偏析,得到成分均一、组织均匀的优良铸锭,可减少后续加工的缺陷发生率,提高了生产效率. 相似文献
4.
在直径为650 mm的铝合金热顶半连续铸造过程中施加双源超声振动系统, 研究3种超声辐射杆浸入深度对铸锭宏观凝固组织的影响.基于铝合金铸锭凝固组织形貌的检测结果以及ANSYS等有限元软件对铸造过程中声场的仿真结果, 深入探讨了超声辐射杆在不同的施振深度下对铝合金铸锭凝固组织细化机制的影响.结果表明: 随着超声辐射杆施振深度的增加, 铸锭截面组织整体进一步细化, 晶粒形状由发达的枝晶变为等轴枝晶; 由于超声辐射杆端面以及柱面存在几个固定位置处振动波峰, 在铝熔体中不同的超声施振深度下存在不同的超声空化范围, 进而导致凝固组织的细化机制也不同. 相似文献
5.
6.
Haynes282合金是700℃超超临界发电机组高温段转子和气缸等构件的首选材料。Haynes282合金铸件组织控制和锻件析出相调控,是相关产品生产工艺制定的难点。以Haynes282为研究对象,通过金相、SEM、EDS等方法,对Haynes282合金电渣重熔后的铸态组织以及锻造后的析出相特性进行系统表征。结果表明,Haynes282合金的枝晶尺寸对冷速非常敏感;电渣锭心部的二次枝晶臂间距要大于表层的,分别为72μm和56μm。枝晶臂和枝晶间元素Al、Cr、Co的偏析系数接近1,元素Mo和Ti的偏析系数较大,Ti的偏析系数超过了1. 7;铸锭心部的偏析比表层略大。经过1 150℃均匀化8 h的热处理和锻造,基本消除了合金中的元素偏析;锻后在晶界上断续分布的第二相主要为富Mo和Cr的M_(23)C_6。 相似文献
7.
8.
GH586合金是我国为满足航天工业发展而自行研制的一种新型镍基变形高温合金。该合金由于合金化程度高,特别是W、Mo、Ti等元素含量较高,铸锭成分偏析严重,组织不均匀,以致合金变形抗力大,热加工塑性差,锻造成型困难。本文对GH586合金铸锭均匀化处理前后的微区成分、晶间组织、热塑性进行了综合研究和分析,结果表明:该合金铸锭经1200℃高温长时间均匀化处理后显著降低合金元素的枝晶偏析程度,同时随着均匀化时间的延长,晶间碳化物逐渐细化、球化、趋向于均匀弥散分布,从而大幅度提高了合金铸锭的热加工塑性。 相似文献
9.
10.
11.
Wensheng Li Houfa Shen Xiong Zhang Baicheng Liu 《Metallurgical and Materials Transactions B》2014,45(2):464-471
In the current study, two significant phenomena involved in heavy steel ingot casting, i.e., species transport and macrosegregation, were numerically simulated. First, a ladle–tundish–mold species transport model describing the entire multiple pouring process of heavy steel ingots was proposed. Carbon distribution and variation in both the tundish and the mold of a 292-ton steel ingot were predicted. Results indicate high carbon concentration in the bottom of the mold while low concentration carbon at the top of mold after the pouring process. Such concentration distribution helps in reducing both negative segregation in the bottom of the solidified ingot and positive segregation at the top. Second, a two-phase multiscale macrosegregation model was used to simulate the solidification process of industrial steel ingots. This model takes into account heat transfer, fluid flow, solute transport, and equiaxed grain motion on a system scale, as well as grain nucleation and growth on a microscopic scale. The model was first used to analyze a three-dimensional industry-scale steel ingot as a benchmark. Then, it was applied to study macrosegregation formation in a 53-ton steel ingot. Macrosegregation predicted by the numerical model was presented and compared with experimental measurements. Typical macrosegregation patterns in heavy steel ingots are found to be well reproduced with the two-phase model. 相似文献
12.
In casting heavy ingots of high‐chromium high‐carbon cold work steels, macrosegregation develops in the center of the ingot, causing difficulties during subsequent hot working. Heat transfer and solidification of an industrial scale high‐carbon high‐chromium steel ingot was simulated and thereafter a laboratory scale representative ingot was designed to model the solidification of the industrial scale ingot. Titanium in the range of 0.3–1% was added to the high‐chromium high‐carbon (12%Cr–2%C) steel during melting process. Microstructures, macrosegregation and phase formations were studied using optical microscopy, scanning electron microscopy, energy dispersive X‐ray spectrometry, wave dispersive X‐ray spectrometry, optical emission spectroscopy, and X‐ray diffraction. Addition of 0.3% titanium was sufficient to diminish the macrosegregation; however it did not have a significant effect on the grain size. Addition of 0.7 and 1% titanium had a substantial effect on grain size in the longitudinal direction and refined the primary carbides structure. The formation of small TiC carbides that precipitated before solidification of liquid iron acted as nuclei for primary pro‐eutectic austenite grains. 相似文献
13.
A. M. Glenn S. P. Russo P. J. K. Paterson 《Metallurgical and Materials Transactions A》2003,34(7):1513-1523
The effect of titanium and titanium diboride inoculation on the spatial variation of local solidification time for direct
chill (DC) cast ingots of aluminum alloy 5182 (AA5182) was studied. The results have been compared to those of an ingot cast
without grain refining. To accomplish this, the effect of grain refining on a number of ingot characteristics such as grain
size, macrosegregation, spatial variation of dendrite arm spacing, and thermal conductivity was investigated. Furthermore,
the effect of grain refining on the well-known relationship between dendrite arm spacing and local solidification time had
to be established for AA5182. The results indicated that the spatial variation of dendrite arm spacing in the industrial ingots
was independent of grain refining, although the nonrefined ingot produced significantly finer dendrite arm spacings in its
center. This was attributed to the influence of showering crystals in the nonrefined ingot. The relationship between dendrite
arm spacing and local solidification time was also found to be independent of grain refining. 相似文献
14.
针对GCr15SiMn钢锭易出现宏观偏析凝固缺陷的问题,研究了过热度对GCr15SiMn钢锭宏观偏析的影响规律,使用真空感应炉冶炼1 kg的GCr15SiMn钢锭,通过酸侵试验与OPA技术分别测定了钢锭的凝固组织与宏观偏析,并结合ProCAST软件分析了钢液流动的规律。结果表明,高过热度(70 ℃)时,中心下部出现一定程度的负偏析,中心上部形成了较严重的正偏析同时伴随疏松;中过热度(50 ℃)时,疏松范围较小,碳元素分布较均匀;低过热度(20 ℃)与极低过热度(-20 ℃)时,疏松范围扩大,凝固初期是严重负偏析,凝固末期是严重正偏析。过热度影响偏析的机理为,高过热度时,凝固过程热对流较强,溶质上浮,钢锭上部的正偏析严重;当过热度过低时,初期凝固大量形核并保留在钢锭底部,在底部形成严重的负偏析。 相似文献
15.
超声波处理时间对工业纯铝铸锭结晶组织的影响 总被引:1,自引:0,他引:1
研究了超声波处理时间对工业纯铝铸锭结晶组织的影响,即添加除气剂又进行超声波处理的情况。分析了超声波对工业纯铝结晶组织影响的原因。研究结果表明。采用合适的超声波处理时间,可以提高工业纯铝铸锭的细化率。 相似文献
16.
本文从理论上分析了采用锭模吹氩对提高镇静钢质量的作用。锭模吹氩工艺有去气,去夹杂物方面的效果,并可以改善钢锭铸态组织,减少皮下气泡,还探讨了锭模吹氩对钢锭化学成分和宏观偏析的影响。 相似文献
17.
Hervé Combeau Miha Založnik Stéphane Hans Pierre Emmanuel Richy 《Metallurgical and Materials Transactions B》2009,40(3):289-304
Although a significant amount of work has already been devoted to the prediction of macrosegregation in steel ingots, most
models considered the solid phase as fixed. As a result, it was not possible to correctly predict the macrosegregation in
the center of the product. It is generally suspected that the motion of the equiaxed grains is responsible for this macrosegregation.
A multiphase and multiscale model that describes the evolution of the morphology of the equiaxed crystals and their motion
is presented. The model was used to simulate the solidification of a 3.3-ton steel ingot. Computations that take into account
the motion of dendritic and globular grains and computations with a fixed solid phase were performed, and the solidification
and macrosegregation formation due to the grain motion and flow of interdendritic liquid were analyzed. The predicted macrosegregation
patterns are compared to the experimental results. Most important, it is demonstrated that it is essential to consider the
grain morphology, in order to properly model the influence of grain motion on macrosegregation. Further, due to increased
computing power, the presented computations could be performed using finer computational grids than was possible in previous
studies; this made possible the prediction of mesosegregations, notably A segregates.
This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC
2007), which occurred in September 2007 in Nancy, France. 相似文献
18.
R. Tanzer W. Schützenhöfer G. Reiter H.-P. Fauland L. Könözsy A. Ishmurzin M. Wu A. Ludwig 《Metallurgical and Materials Transactions B》2009,40(3):305-311
A mixed columnar-equiaxed solidification model is used to predict the macrosegregation in high grade steel ingots. In this
model, three phases are considered: the melt; the columnar phase, which is assumed to be stationary; and the equiaxed phase,
which is free to move. With this approach, the model is able to simulate the evolution of the primary solid phase distributions
including the columnar-to-equiaxed transition, the melt convection and the grain sedimentation, and their influence on the
macrosegregation. Thermodynamic information of a ternary alloy (Fe-C-Cr) is simplified by the piecewise linearization of the
phase diagram around the suitable compositions in the ferritic and austenitic regions. As a result, macrosegregation of carbon
and chromium has been analyzed. As the first step, the validation of the numerical model was performed on a benchmark ingot
of a laboratory scale. Computed macrosegregation and primary structure were compared with measurements and good agreement
was obtained.
This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC
2007), which occurred in September 2007 in Nancy, France. 相似文献
19.
Thermosolutal convection and macrosegregation formation during the solidification of steel ingots are numerically simulated in three dimensions. The simulation is based on a fully coupled model for mass, momentum, energy, and species conservation equations. The interdendritic flow in the mushy zone is governed by Darcy's law, and the permeability term is discretized using an interpolated liquid fraction method. The numerical results for a benchmark test of macrosegregation in a Pb‐Sn alloy are compared with experimental data taken from the literature. The present model is applied to simulate the solidification of industrial steel ingots. Preliminary predictions are obtained, including the positive segregation in the hot top, and the conically shaped negative segregation zone at the bottom of the ingot. The predicted variation of the segregation ratio in carbon along the vertical centreline of an ingot is compared with measurements, and generally good agreement is observed. Future attention should be paid to the precision of prediction by considering complex solidification issues, such as the sedimentation of free equiaxed grains and the formation of shrinkage cavity. 相似文献
20.
A new quenching technique for studying the formation of macrosegregations in ingots has been developed and used in a study
of the formation ofA-segregations in ingots. The formation of a negative segregation in the bottom part of an ingot and a positive segregation
in the top part have also been studied. It was found that the three types of macrosegregation phenomena could be explained
by the occurrence of interdendritic convection during the solidification process. 相似文献