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Rapid preparation of ceramic moulds for medium-sized superalloy castings with magnesia-phosphate-bonded bauxite-mullite investments

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China Foundry 2010年第4期7卷 337-341页

作者： Li Tingzhong luo jirong Wu Shusen State Key Lab of Materials Processing and Die ＆ Mould Technology Huazhong University of Science and Technology Wuhan 430074China

Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI), a series of experiments were conducted, including modifciation of the workable time of slurry by liquid(mL)/powder(g)(L/P) ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP) as strengthening agent, and adjustment of bauxite (g)/mullite(g)(B/M) ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.

关键词： medium-sized ceramic moulds magnesia-phosphate-bonded bauxite-mullite investments superalloy castings initial setting time compressive strength

Study on direct-chain diacid modified phenolic resin for Al-alloy casting

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China Foundry 2005年第1期2卷 28-33页

作者： Yundong JI jirong luo Moyin LI School of Materials Huangzhong University of Science and Technology Wuhan 430074 Hubei P. R. China Wuhan Life Chemistry and Industry Co. Wuhan 430011 Hubei P. R. China

Resin coated sand (RCS) with phenolic resin matrix can hardly be collapsed when it is used in Al-alloy casting. Adding collapsing agent and reducing the concentration of resin are solutions adopted by workers, but these methods tend to reduce the initial strength of RCS. Synthesis of modified phenolic resin with direct-chain diacid DAn (/JS=6, where n means carbon amount) was studied here. The effects of the addition of modifying agent on molecular weight, gel time and softening point were investigated. Optimal addition of DAn (10% phenol) was obtained by testing the initial and retained flexural strengths of the modified resin. FT-IR spectra showed that carbonyl shifts to higher wave number. With the use of TG, SEM and strength loss curves, the relation between initial and retained strengths was analysed. Tests on the heated deformation curve, before and after resin modification, show that PF-DA10 has the characteristic of higher initial and retained strengths together.

关键词： direct-chain diacid PF resin modify Al-alloy casting RCS

Effects of processing parameters on microstructure of semi-solid magnesium alloy

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China Foundry 2004年第1期1卷 45-48页

作者： Shusen WU Dongnan LI Youwu MAO Zehui XIAO jirong luo State Key Lab of Mold & Die Technology Hua zhong University of Science and Technology Wuhan 430074 HubeiP.R .China

In this paper, the effects of pouring temperature of magnesium melt, preheating temperature of the barrel of the screw mixer, and shear rate on the solidified microstructures of semi-solid slurry were investigated by a mechanical stirring semi-solid process. The appropriate processing parameters of slurry preparation were obtained, and the mold filling ability of semi-solid slurry for thin-walled casting was examined. Results indicate that the solid volume fraction of non-dendritic microstructure increases with a decrease in pouring temperature of magnesium melt and the barrel preheating temperature of the screw mixer. Also the grain size of primary α-phase is reduced. Furthermore, the solid volume fraction of semi-solid nondendritic structure decreases with an increase of shear rate. The fine and round granular microstructure with 30～50 μm in size of semi-solid AZ91D magnesium alloy was presented. Finally, a 1.0 mm thin-walled casting with a clear contour and good soundness was successfully made by semi-solid rheo-diecasting.

关键词： semi-solid metal magnesium alloy rheocasting slurry microstructure

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消失模铸造铝液充型速度研究

特种铸造及有色合金 2000年第1期20卷 26-28页

作者：吴国华罗吉荣华中理工大学

研究了各工艺因素对消失模铸造铝液在型腔中平均流速的影响。结果表明，保温涂料及一定的涂层厚度有利于提高铝液的充型速度。浇注温度越高、直浇道空心面积率越大，铝液充型速度越快。模样厚度越大，铝液充型速度越慢。一定的直浇道长... 详细信息

研究了各工艺因素对消失模铸造铝液在型腔中平均流速的影响。结果表明，保温涂料及一定的涂层厚度有利于提高铝液的充型速度。浇注温度越高、直浇道空心面积率越大，铝液充型速度越快。模样厚度越大，铝液充型速度越慢。一定的直浇道长度及直浇道面积有利于提高铝液的充型速度。施加负压会使铝液的充型速度大大提高。

关键词：铝合金消失模铸造充型速度

高真空压铸技术及高强韧压铸铝合金开发和应用的现状及前景

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特种铸造及有色合金 2007年第12期27卷 939-942页

作者：万里潘欢罗吉荣华中科技大学材料成形与模具技术国家重点实验室

高真空压铸的特点在于模具型腔中的真空度达到91～96kPa,铸件中每100g的含气量低至1～3mL,可通过热处理提高其强度和韧度。而高强韧压铸铝合金多为Al-Si-Mg系合金,其原因在于Mg的固溶强化作用可提高合金的力学性能。近几年来国外特别是... 详细信息

高真空压铸的特点在于模具型腔中的真空度达到91～96kPa,铸件中每100g的含气量低至1～3mL,可通过热处理提高其强度和韧度。而高强韧压铸铝合金多为Al-Si-Mg系合金,其原因在于Mg的固溶强化作用可提高合金的力学性能。近几年来国外特别是日本在开发高真空压铸技术和压铸铝合金方面取得了成果并在轿车上获得应用。目前开发的高真空压铸方法主要有Vacural法和MFT法,其中MFT法是一种适合于压铸企业开发并具有良好应用前景的高真空压铸技术。

关键词：高真空压铸压铸铝合金强度韧度轻量化

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面向21世纪的特种铸造技术

特种铸造及有色合金 1999年第S1期19卷 135-137页

作者：罗吉荣华中理工大学

２１世纪铸造技术创新的显著特点体现于新材料与先进的造型、浇注技术的有机结合，铸件产品结构趋向于近净形、多功能化和集成化，同时要求能源消耗最少，环境负荷最小。

关键词：特种铸造技术创新压铸、快速制造

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铁基颗粒复合材料的组织与抗冲蚀性能

特种铸造及有色合金 1998年第6期18卷 8-10页

作者：许大庆罗吉荣黄乃瑜华中理工大学

采用实型负压铸造法制备出铁基颗粒复合材料，分析了复合层的微观组织，研究了其显微硬度分布，测定了复合层的抗冲蚀性能。研究结果表明，铁基颗粒复合材料具有较高的硬度、良好的抗冲蚀性能，明显改善了基体材料的性能。

关键词：铁基复合材料微观组织抗冲蚀磨损性能

第九届国际铸造博览会(GIFA’99)综述——特种铸造部分

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特种铸造及有色合金 1999年第5期19卷 48-52页

作者：黄乃瑜 罗吉荣华中理工大学

介绍了第九届国际铸造博览会总的特点，以及在特种铸造方面展示的新技术、新成果，包括压力铸造、消失模铸造、熔模铸造、金属型铸造及低压铸造、艺术铸造、快速造型技术在铸造领域中的应用。

关键词：铸造博览会特种铸造

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轻合金覆膜砂专用酚醛树脂的开发研究

特种铸造及有色合金 2005年第2期25卷 118-120页

作者：冀运东罗吉荣肖泽辉李末银华中科技大学武汉力发化工有限责任公司

采用具有不饱和脂肪直链的EPA改性剂参与合成酚醛树脂 ,用不饱和脂肪直链段部分取代亚甲基键 ,使酚醛树脂具有高强度和较低温度分解的特性。研究了EPA的加入量对树脂性质和覆膜砂力学性能的影响 ,10 %是最佳值。热失重试验和高温变形曲... 详细信息

采用具有不饱和脂肪直链的EPA改性剂参与合成酚醛树脂 ,用不饱和脂肪直链段部分取代亚甲基键 ,使酚醛树脂具有高强度和较低温度分解的特性。研究了EPA的加入量对树脂性质和覆膜砂力学性能的影响 ,10 %是最佳值。热失重试验和高温变形曲线试验结果证明 ,使用该树脂混制的覆膜砂 ,具有强度高、溃散性好等特点。实践证明 :使用该种覆膜砂浇注铸件后 ,工人的清砂劳动量下降。

关键词：覆膜砂酚醛树脂 EPA改性溃散性