薄壁调节片熔模铸造缺陷的控制

某航空发动机用调节片采用熔模精密铸造方法生产。调节片轮廓尺寸200 mm×170 mm,铸件平均厚度1.0 mm。调节片在铸造过程中极易产生铸造裂纹和疏松缺陷,冶金质量控制难度极大。针对以上问题并结合计算机模拟结果,对铸件浇注系统、型壳的焙烧温度、铸件的浇注温度进行改进,最终有效控制了铸造缺陷,提高了产品合格率。     

龙门式加工中心立柱部件铸造工艺研究

以EGC2040龙门式加工中心立柱为研究对象,对其铸造工艺进行研究,通过Any Casting软件对铸件充型、凝固过程进行了数值模拟,对缩孔缩松缺陷进行预测,根据模拟与预测结果对原工艺进行优化,并使用三因素三水平正交实验确定最佳工艺参数。研究表明:采用阶梯式、多内浇道浇注方案,在浇注温度1 320℃、浇注速度80 mm/s、冷铁厚度70 mm条件下加工铸件,铸件品质良好,无明显缩孔缩松缺陷,符合生产要求。     

5MD缸体铸造工艺优化

某工厂生产的5MD缸体体积小,适合一箱多型浇注,最初设计浇注工艺时采用底注式浇注系统,铸件出现冷隔、裂纹等缺陷。为了解决铸件出现的上述缺陷,首先对原工艺方案进行了模拟,对浇注系统进行分析之后改进工艺,在新工艺方案数值模拟结果中未发现铸件有缺陷。采用新工艺试制铸件,对铸件进行检测,也未发现有缺陷,因此,采用新工艺方案批量生产铸件,解决了5MD缸体存在的冷隔和裂纹缺陷,获得力学性能满足技术要求的优良铸件。     

支撑锭模用精整盘的铸造工艺

介绍了用于支撑锭模的精整盘的铸造工艺、造型方法、铁液熔炼工艺和成分控制、浇注工艺以及热处理工艺。铸件材料牌号为HT150,质量为3 000 kg,主要尺寸为2 000 mm×1 200 mm×150 mm,属于较大型厚壁类铸件。采用水玻璃和硅砂配制型砂,铸件全部放在下型,倾斜浇注,浇注系统设在铸件最低处,在铸件最高处设置压边冒口。首件试制的浇注温度偏高,结果在内浇道附近有严重粘砂缺陷。将浇注温度降低后,对生产的铸件进行检查,结果显示:铸件表面光洁度、形状尺寸和力学性能均符合技术要求,无任何铸造缺陷。     

浇注系统对高温合金薄壁熔模铸件质量的影响

K424合金调节片为某型号航空发动机矢量喷口部位的核心部件,属于典型的大尺寸薄壁结构件,采用熔模铸造工艺整体铸造成形。在调节片生产过程中,冶金质量难以控制,裂纹、缩松问题一直是影响铸件成品率的主要原因。经试验分析,确定了裂纹、缩松缺陷形成原因及影响因素。通过优化浇注系统、控制型壳预热温度和浇注温度,显著降低了铸件裂纹、缩松缺陷废品率,获得了冶金质量优良的调节片铸件,提高了工艺成品率。     

大型热风炉炉箅子的消失模铸造技术

一种用消失模生产高质量要求炉箅子的铸造技术,该技术通过优化模具设计,研制消失模铸造方案,采用四块白模对接技术,设计白模拼接工装、最佳刷涂料厚度及涂刷次数、最佳浇注系统及浇注温度范围,获得了尺寸准确、表面光洁的致密铸件。     

高温合金薄壁铸件浇注系统设计

某高温合金调节片采用熔模精密铸造方法生产。该调节片尺寸为330mm×240mm,壁厚为0.8mm,并有多处纵横交错的加强筋,铸造成形难度较大,在铸造过程中铸件易产生欠铸、冷隔、疏松、裂纹等缺陷,其合格率较低。重点叙述了通过改进、优化铸件浇注系统的设计,有效消除了铸件的冷隔、欠铸缺陷,铸件的合格率大幅度提升,工艺出品率提高到原来的2倍左右。     

新型Fe-W合金应力框铸造应力模拟及变形分析

利用铸造模拟软件Pro CAST对新型Fe-W合金应力框件在3种不同浇注温度、浇注速度和砂型预热温度下进行了铸造应力场模拟,得到铸件的应力分布情况,并对模拟结果进行了分析。分析了铸件位移最大节点处的位移随浇注温度、砂型预热温度和浇注速度的变化。设计L_9(3~4)正交试验对铸件残余应力、位移和砂型预热温度、浇注速度、浇注温度的关系进行了探讨,并分别采用单因素分析法和极差分析法对模拟结果进行了分析,结果表明:砂型预热温度对残余应力和变形影响较大,砂型预热温度越高,铸件残余应力越小,变形越小;浇注温度对残余应力影响次之,对变形的影响最小,浇注温度越高残余应力越大,变形越大;浇注速度对残余应力影响最小,对变形的影响次之,浇注速度越大,残余应力越小,变形越小;浇注速度为0.6 m/s,浇注温度为1 560℃、砂型预热温度为600℃时,铸件产生的残余应力较小,浇注速度为0.7 m/s,浇注温度为1 560℃、砂型预热温度为600℃时铸件产生的位移、变形较小,可指导实际生产。     

高温合金某薄壁铸件铸造缺陷工艺控制

K424合金扩张调节片是某型号冲压发动机尾喷管核心部件,属于典型的大尺寸薄壁结构件。该调节片采用熔模铸造工艺整体铸造成形,在生产过程中,铸件易产生疏松、裂纹及底板膨胀变形等缺陷,冶金质量控制难度很大。通过优化铸件浇注系统和造型工艺,有效消除了调节片的裂纹、疏松和膨胀变形等缺陷,铸件的合格率大幅度提升。     

铝青铜平衡环的金属型铸造

金属型铸造生产多级水泵铝青铜平衡环,与砂型铸造法相比,可节省有色金属材料5％,提高抗拉强度15％～20％。工艺特点为采用环形冒口凸台、上雨淋式浇注系统;金属型预热温度200～250℃;浇注温度1150℃。     

胫骨生物陶瓷复合材料的微结构增韧机理

扫描电镜观察显示胫骨是一种由羟基磷灰石和胶原蛋白组成的自然生物陶瓷复合材料.羟基磷灰石具有层状的微结构并且平行于骨的表面排列.观察也显示这些羟基磷灰石层又是由许多羟基磷灰石片所组成,这些羟基磷灰石片具有长而薄的形状,也以平行的方式整齐排列.基于在胫骨中观察到的羟基磷灰石片的微结构特征,通过微结构模型分析及实验,研究了羟基磷灰石片平行排列微结构的最大拔出能.结果表明,羟基磷灰石片长而薄的形状以及平行排列方式增加了其最大拔出能,进而提高了骨的断裂韧性.     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.     

试论洋务派教师聘任的思想

洋务派在洋务学堂的办学活动中,为了解决西学专业学科的教学困难,采用了聘请外籍教师的应急措施.他们以真才实学,合同制管理作为主导思想,并认为这种解决师资的途径只是权宜之计,并非久远.从客观上看,洋务派的教师聘任思想有深刻的历史影响.