差压铸造薄壁铝硅合金铸件的位置效应

采用差压铸造工艺,研究垂直缝隙式浇注系统浇注的铝合金硅铸件不同位置的组织和力学性能变化.采用石英砂型、SiC砂型和冷铁,浇口处铸件的晶粒最细小,致密度高、力学性能最好;铸件冷端的组织和性能次之;位于两者之间的铸件的组织和性能最差.分析表明对于具有垂直缝隙式浇注系统,差压铸造凝固压力对金属的凝固作用具有位置效应,浇口处液态金属温度高,凝固时间长,凝固压力对浇口处金属的凝固作用显著;铸件冷端金属凝固时间短,凝固压力对该处金属的凝固作用不显著,铸型的冷却速度对铸件组织和性能的影响起显著作用.浇口处与冷端之间的金属液体的凝固受压力和冷却速度的影响小,铸件的晶粒尺寸最大、密度最小、性能最低.冷却速度提高,铸件的任意位置的组织和性能都相应得到提高.     

超级双相不锈钢5A泵壳铸件裂纹缺陷分析与消除

分析了超级双相不锈钢5A泵壳铸件产生裂纹的原因,结果表明,铸件在铸型里缓慢冷却过程中,组织发生了铁素体的共析转变,铁素体相析出了σ相和二次奥氏体相,σ相是泵壳铸件产生开裂的主要原因,收缩应力和热应力的变化加剧了泵壳铸件开裂的倾向。采用热打箱+热装炉工艺或缓慢冷却＋缓慢升温工艺措施,有效地避免了泵壳铸件的开裂。      

Ti321钛合金轴箱铸件石墨型铸造工艺研究

目的 研究钛合金高铁轴箱铸件采用石墨铸型工艺时,铸件尺寸、成形及内部质量控制技术。方法 通过对高铁轴箱铸件的结构特点进行分析,针对铸件结构复杂、尺寸比较大、铸件成形比较困难、容易变形的特点,开展了铸型结构设计、铸件尺寸控制技术和铸件成形工艺等方面研究。采用多活块组合的石墨铸型,设计底注开放式浇注系统,利用Procast软件对高铁轴箱铸件的浇注方案进行了模拟分析。选用Ti321合金,设定合理的浇注参数,利用真空自耗电极凝壳炉对铸件进行浇注。结果 铸件成形良好,经过热等静压和后精整后的铸件,铸件内外部冶金质量和性能指标,满足客户标准要求,验证了方案的合理性。结论 铸件的计算机模拟对铸件工艺的设计提供了技术支撑,高铁轴箱铸件采用的石墨型浇注工艺比较合理。     

3D打印陶瓷铸型研究与应用进展EI北大核心CSCD

陶瓷铸型是一类应用于熔模精密铸造领域、用于成型铸件内外部结构的复杂部件。随着铸件复杂度的提升,需要更加精细、复杂的铸型来满足铸造需求,然而传统的陶瓷铸型成型手段如注射成型等存在成本高、研发周期长等问题,难以满足复杂精细结构的成型要求。3D打印技术作为一种快速成型手段能够精准成型复杂精细结构,将其应用于铸型生产,不仅能够解决复杂结构的成型问题,同时也能降低生产成本、缩短生产周期。本文主要阐述了3D打印技术在陶瓷铸型生产中的应用,从应用于铸型3D打印陶瓷材料的种类及特性、典型铸型3D打印技术及铸型打印后处理手段三个方面对3D打印技术陶瓷铸型的研究与应用进行介绍,并对该技术未来的发展进行展望,指出3D打印技术能够有效解决复杂陶瓷铸型的成型问题,从而满足复杂空心结构金属件的铸造需求。     

离心加速场中金属凝固过程温度场分布数值分析

采用有限差分法及MathCad软件首次模拟了二维柱坐标系下自硬砂型离心铸造凝固过程,并就转速、浇温、铸型预热温度、铸型类别等工艺参数对铸件温度场分布的影响规律进行了研究。模拟结果表明,由于采用自硬砂型和灰铁盖,铸件的上下表面首先凝固,然后逐渐向金属液中间推进;随转速、铸型蓄热系数的增加,铸型预热温度与浇注温度的降低,金属凝固加快;在其它条件相同的情况下,型温对温度场的影响最大,转速其次,浇温最小。      

SHS-离心法制备陶瓷复合管道热应力的有限元分析

模拟分析了SHS-离心法制备陶瓷复合管道在冷却凝固过程中的温度分布和变化,从而为工艺参数的选择和管道界面结构分析提供了基础.利用ANSYS软件的瞬态热分析功能和热-结构耦合功能,数值上模拟复合管道的残余热应力,分析SHS层厚度对陶瓷复合管道性能的影响.数值分析结果表明,合理调整SHS层的厚度,可使界面残余热应力变小,从而提高陶瓷复合管道的安全可靠性.     

工艺参数对真空吸铸TiAl基合金连杆铸造过程的影响

本文利用底漏式真空吸铸方法制备TiAl合金汽车发动机连杆铸件,并研究了吸铸工艺参数对铸造过程的影响.分别采用了金属型芯金属模具、陶瓷芯金属模具以及陶瓷型壳进行性吸铸实验,研究了不同的吸铸参数对连杆铸件的成形性影响.得到了TiAl合金底漏式真空吸铸的优化工艺参数,初步获得了形状完整的连杆件.     

重力SHS法制备陶瓷衬层的组织与工艺研究

采用预置芯等方法对重力SHS法制备的陶瓷内衬层厚度进行控制,研究预置芯大小、SiO_2添加量等对陶瓷层厚度与组织的影响,考察冷却工艺对陶瓷层组织与性能的影响。研究结果表明,随着预置芯直径增大,陶瓷层厚度先增大后减小;在预置芯直径一定的情况下,随着SiO_2含量的增加,陶瓷层厚度增加。添加适宜的SiO_2有利于获得组织细小而致密的陶瓷层。冷却速度快,凝固组织细化,陶瓷层硬度高;冷却速度慢,熔体分离充分,陶瓷层组织均匀,陶瓷层和钢管结合更加紧密,抗热震性能好。     

TiAl基合金/金属型界面反应规律研究

利用感应凝壳熔炼（ISM）法,在金属型中离心浇铸了Ti-48Al-2Cr-2Nb(at%)合金汽车排气阀,并利用SEM,XRD和EMPA等检测方法对排气阀的表面层结构进行了分析。结果表明,排气阀表面上的铁含量约为0．3wt%,渗铁层厚度为3μm左右。由于金属型与合金熔体之间的反应,以及铸型的强冷却作用,使得排气阀表面上出现了一定厚度的硬化层,其厚度要远大于渗铁层,这对于提高铸件表面的耐磨性和强度是非常重要的。     

铸造Ti-1 5-3合金的凝固行为及组织分析

应用所设计的阶梯铸件的铸型,以及钨铼热电偶和由ADAM系列A／D数据采集及转换模块构成的计算机多通道温度数据采集处理系统,对Ti-15-3合金凝固冷却温度变化进行了实验测试与数据处理,测试了合金的浇注温度,液相线温度和固相线温度,得出合金的凝固温度区间为71℃,对合金阶梯铸件的补缩冒口进行宏观形貌观察表明：Ti－5－3高强钛合金的凝固呈集中补缩的特征,且孔洞内表面光滑,凝固组织观察表明：由于受金属铸型内壁激冷作用和铸件尺寸较小的影响,合金在接近铸型内壁或铸件尺寸较小部位处的铸态晶粒组织较细小,且出现较多黑色第二相的非平衡凝固组织。     

Aktivlöten von keramischen Segmenten für den Einsatz in verschleißkritischen Bereichen von Schmiedegesenken

Active brazing of ceramic inlays for the application in wear critical areas of forging dies The use of reinforcing ceramic segments in forging tools is investigated and has been successfully tested with model of dies recently. With reinforcing ceramic segments, however, the thermal widening of the steel tool is a major problem for forging dies. Further, only rotationally symmetrical ceramic inserts can be used as reinforcements which restricts the shape capabilities in tool design significantly. A considerably greater design flexibility is possible if the ceramic segments are brazed into the die body material. To this end, reactively brazed ceramic‐metal composites are to be developed and tested for feasibility in the forging process.     

Production of surface chilled ductile iron

Surface chilled ductile iron has become a promising material for machine parts exposed the wearing and impact because of good combination of high wear resistance and toughness. In this study, the effect of the chemical composition, mold wall thickness and sample diameter on the chill formation, chill depth, and carbide precipitation in the ductile iron were studied. The casting having four different chemical compositions were carried out to copper molds having various samples diameter (? 10–50 mm) and mold wall thickness (5, 15, 20, 30 and 50 mm). Microstructural and hardness profile evaluation were carried out from surface to center of part in order to define the effects of cooling rate on the chill formation. Experimental results showed that the production of surface chilled ductile iron having various chill depths can be achieved with controlling of the cooling rate. Hardness profile increases with increasing of mold wall thickness (cooling rate). High chromium content increases chill depth and decrease graphite formation. High silicon content promotes graphite formation while it decreases carbide precipitation. Chill formation on the ductile iron can be optimized with controlling mold wall thickness and sample diameter (cooling rate).     

精铸技术在模具制造中的应用

本文叙述了熔模精铸模具、陶瓷型精铸模具、石膏型精铸模具和加压精铸模具的应用情况，由于精铸模具比机加工模具缩短了生产周期．降低了制造成本．故有很好的发展前景。文章还对陶瓷型精铸模具技术提出了六点改进意见。     

Study on the preparation and microstructure of a single-crystal hollow turbine blade

This paper studied the structural design of a ceramic core and a blade, ceramic core localization, shell preparation, casting process, core leaching technology, and the heat treatment process of a single-crystal hollow turbine blade. The results show that the single-crystal structure solidification sequence of the blade platform is consistent with the cooling sequence and the pulling-out direction of the blade. The primary dendrites were obviously enlarged with the increase of the blade thickness owing to the change in the local cooling rate. Besides, the γ′ phase had a high uniform size distribution ranging from 0.40 to 0.60?µm after heat treatment, and the cubic degree was more homogeneous in comparison with the as-cast microstructure, which are favorable for the superalloy structure. Moreover, γ′ phase size gradually increased and its quantity gradually reduced owing to the increase of the wall thickness in the growth direction.     

带阻尼台叶片多向模锻过程场量分布规律研究

为了提高带阻尼台叶片的综合机械性能,采用多向模锻技术来实现带阻尼台叶片的精净成形,通过确定带阻尼台叶片多向模锻分模形式及分模面位置,基于UG建立了带阻尼台叶片多向模锻模具的几何实体模型;在此基础上,采用DEFORM3D建立了该类叶片多向模锻过程的三维有限元模型,确定了模具的加载方式和加载顺序,实现了带阻尼台叶片多向模锻过程有限元模拟,获得了该成形过程中不同加载方式下坯料的速度场、等效应变场和温度场分布规律及载荷-行程曲线,揭示了带阻尼台叶片多向模锻过程中金属充填模具型腔的情况及温度场、应变分布以及载荷随行程的变化规律.该成果可应用于带阻尼台叶片的实际生产过程中,对采用多向模锻工艺来实现带阻尼台叶片的精锻具有指导作用.     

基于滑模控制的低压铸造模具冷却控制系统设计

目的 为了准确控制模具的温度,提高铸件品质和效率.方法 设计基于滑模控制的模具冷却控制系统.首先,以低压铸造模具冷却工艺为基础,分析不同模具温度对铸件品质的影响,明确模具温度控制的重要性.基于浇注温度、冷却水温度以及模具温度,对模具冷却过程进行建模,获取冷却水和模具的热传递函数.然后,采用三向(左、右、底部)冷却方法,...     

石油钻杆接头模锻工艺研究

介绍了石油钻杆接头采用自由锻造的工艺方式存在毛坯余量大、材料利用率低、生产成本较高等缺点.为了提高钻杆接头毛坯精化程度和降低生产成本,提高市场竞争力,需要更高效的加工方式.通过对钻杆接头模锻工艺参数摸索,合理地选择了钢坯感应加热、毛坯加工率、加工设备选择、模具设计、锻后缓冷等工序工艺参数,最终实现了钻杆接头一次模锻成形的工艺.石油钻杆接头模锻后,降低了毛坯的下料质量,减少了机械加工余量,提高了材料利用率,降低了生产成本.     

Thermo-mechanically coupled FE analysis and sensitivity study of simultaneous hot/cold forging process with local inductive heating and cooling

The numerical investigation of the production of a stub shaft is presented, where the highly innovative metal forming technology of the simultaneous hot and cold forging is applied in combination with a hardening process performed directly in the closed forging dies after the forging step similar to press hardening of sheet metal. This complex forging process is completely analysed by means of a finite element simulation including the local inductive heating phase of the workpiece as well as the cooling process of the final stub shaft inside the forging dies. All relevant process parameters and the whole simulation model are documented in detail and the simulation results are discussed and validated by means of experimentally measured data, showing good agreement. Parameter studies for various properties of the model are carried out in order to investigate their influence on the geometry and the temperature field development, whereby a deeper understanding of the entire process is gained. Thus, a finite element benchmark analysis is provided for such a complex thermo-mechanically coupled structuring process.     

快速铸造收缩-扩张形气膜孔空心涡轮叶片

本文将光固化成形技术和凝胶注模成形技术集成在一起,间接自由成形了带有收缩-扩张形气膜孔空心涡轮叶片整体式陶瓷铸型.通过建立收缩-扩张形气膜孔型芯干燥收缩受阻模型,推导了临界干燥收缩率计算公式,实验研究了凝胶注模成型坯体冻干特性.结果表明:冻干收缩率随着失水程度增加而增大,在失去约50%水分之后,干燥收缩停止;预冻温度越...