多组分铜基金属粉末选区激光烧结致密化机理

研究了选区激光烧结专用多组分铜基金属粉末(组分包括纯Cu,预合金CuSn,CuP)的烧结性能.结果表明,通过合理控制激光工艺参数(特别是激光功率和扫描速率),能顺利实现粉末烧结成形,且无明显的"球化"效应和翘曲变形.扫描电镜和X射线衍射分析证实,此组粉末体系的激光烧结是基于液相烧结机制,其中熔点较低的CuSn充当粘结金属,熔点较高的Cu充当结构金属;而添加元素P则起稀释剂的作用,能避免Cu颗粒表面氧化.研究了粉末体系中粘结金属含量对粉末烧结致密化和烧结件微观组织的影响.结果表明,在一定范围内粘结金属含量的提高有利于改善烧结致密度;但若粘结金属过量,则会因"球化"效应而降低致密度.     

基于快速成形技术的机匣盖的快速铸造

在基于快速成形技术的机匣盖快速铸造工艺中,通过用UG软件构建零件的CAD三维模型,采用选择性激光烧结法烧制精铸蜡模.利用该工艺铸造的机匣盖铸件外表面及内腔的尺寸精度和表面质量,能够满足燃气轮机的使用要求.快速成形技术提高了精铸业制造复杂零件的能力,使复杂模型的直接制造成为可能.快速成形技术与现有的铸造工艺相结合,为铸件的研制节省了时间和成本,为后续产品中精密铸件的顺利完成打下了良好的基础.     

Rapid precision casting for complex thin-walled aluminum alloy parts

1 .IntroCtion Seleetive Laser Sintering(SLS)15 an imPortant field ofRaPid PrototyPing(RP),due to its caPability ofProeessinga very wide range ofmaterialsinadireetway.AtPresent,most of sintering materials are nonmetallie,     

磷元素对铜基金属粉末选区激光烧结作用机理

对不同CuP含量的多组分铜基金属粉末(Cu-CuSn-CuP)进行了选区激光烧结实验。利用X射线衍射和扫描电镜研究了添加元素P对烧结致密度及显微组织的影响。研究表明:P元素能在烧结过程中充当脱氧剂而与Cu反应生成CuPO3;但当P过量时,则会因熔体过热倾向明显而加剧氧化;适量增加P元素能改善烧结件层间结合性;而P元素过量则会因生成过多磷渣而降低润湿性及致密度;P元素亦能充当稀释剂而降低熔体粘度及表面张力,从而改善烧结致密度及组织均匀性;但若P元素过量时,则会因熔体粘度过低而导致球化现象。实验结果证实,该组铜基金属粉末体系中CuP的最佳含量为15%。     

Effects of laser energy density on forming accuracy and tensile strength of selective laser sintering resin coated sands

Baozhu sand particles with size between 75 μm and 150 μm were coated by resin with the ratio of 1.5 wt.% of sands. Laser sintering experiments were carried out to investigate the effects of laser energy density（E = P/v）, with different laser power（P） and scanning velocity（v）, on the dimensional accuracy and tensile strength of sintered parts. The experimental results indicate that with the constant scanning velocity, the tensile strength of sintered samples increases with an increase in laser energy density; while the dimensional accuracy apparently decreases when the laser energy density is larger than 0.032 J·mm^-2. When the laser energy density is 0.024 J·mm^-2, the tensile strength shows no obvious change; but when the laser energy density is larger than 0.024 J·mm^-2, the sample strength is featured by the initial increase and subsequent decrease with simultaneous increase of both laser power and scanning velocity. In this study, the optimal energy density range for laser sintering is 0.024-0.032 J·mm^-2. Moreover, samples with the best tensile strength and dimensional accuracy can be obtained when P = 30-40 W and v = 1.5-2.0 m·s^-1. Using the optimized laser energy density, laser power and scanning speed, a complex coated sand mould with clear contour and excellent forming accuracy has been successfully fabricated.     

选区激光烧结环境控制技术

文章根据选区激光烧结快速成型的需求,为减少由于被烧结材料温度变化梯度太大而对成型精度的影响,提出了一种基于远红外加热技术的对料缸内待烧结粉末进行预热的控制技术方案,以降低料缸内待烧结粉末与成型缸内烧结成型表面的温差.结合实例,针对方案之加热装置结构设计、加热功率确定、反射罩设计、控制系统、试验结果分析等进行了阐述.工艺试验表明,通过此方案可有效提高被烧结材料的表面温度,减少其温度变化梯度,降低了烧结过程中的翘曲变形,提高了成型精度.     

复杂薄壁金属零件的快速制造技术

本研究以真空差压铸造技术为基础,结合选择性激光烧结（SLS）快速原型技术和陶瓷壳型精密铸造技术,开发了一种从计算机三维模型到金属零件的快速制造工艺－快速精确铸造工艺,可以实现复杂薄壁铝合金零件的快速成形。本文着重描述了由SLS塑料原型快速制取陶瓷型壳和真空差压精确铸造技术的工艺特点,解决了新产品开发中金属零件快速制造的关键问题,为快速成形技术在铸造中的应用开辟了一个新领域。     

基于选区激光烧结的铜“鼎”艺术品制备工艺研究

以设计制造铜“鼎”艺术品为例,通过构思、创作设计了铜鼎的CAD三维模型;并采用选区激光烧结(SLS)技术,直接烧结出了PS原模;通过渗蜡处理后,得到了强度高和尺寸稳定性好的聚苯乙烯(PS)熔模;并针对含有PS、蜡等有机成分和碳酸钙、石墨等无机填料的蜡模的难熔失问题,提出了合适的PS熔模熔失和型壳焙烧的工艺方案。通过实验表明,焙烧后的型壳内光滑、干净,且强度、致密性均较高;通过浇铸铜合金,成功地制备出了造型复杂、制作精美、尺寸精度高、表面光洁的铜“鼎”艺术品,实现了金属艺术品无模快速制造。     

Additive manufacturing of alumina parts by indirect selective laser sintering and post processing

Innovative powder preparation and post-processing techniques can be employed to obtain high density ceramic parts by means of indirect selective laser sintering. Thermally induced phase separation (TIPS) was used to produce polymer and polymer–ceramic composite particles. The effect of polymer concentration, cooling rate, stirring and alumina particles on polymer and polymer–ceramic composite particles was investigated. Homogeneous spherical alumina–polypropylene (PP) composite powder was synthesized by TIPS for selective laser sintering (SLS). Green Al₂O₃–PP component parts with a density of 34% could be produced by conventional SLS of the polymer under optimized laser power, scan speed, scan spacing and powder preheating temperature. Various post-processing techniques like pressure infiltration (PI), warm isostatic pressing (WIPing) or a combination of both were applied to increase the green density of the Al₂O₃–PP SLM parts. Infiltrating the open porosity green SLS parts with a 30 vol% alumina-powder based ethanol suspension allowed to increase the sintered density, i.e. after polymer debinding and pressureless sintering in air at 1600 °C, from 38 to 64% of the theoretical density (TD). WIPing of the SLS and SLS/infiltrated green parts at 135 °C and 64 MPa allowed raising the green density up to 93 and 83% TD and a sintered density up to 89 and 88% TD, respectively.     

Investigating on casting mold (or core) making with coated sand by the selected laser sintering

1 .Introduction Based on the parameters and cross-section's information from a CAD model, the selected laser sintering (SLS) uses a laser beam to sinter selectively powdered solid materials (plastic, wax, ceramic, metal, etc.), and the solidified material is built up layer by layer to formthepart needed} As there are still some problems in material and technology, it is difficulty to sinter or produce directly     

Selective laser sintering of single-phase powder Cr-V tool steel

Presented is positive experience from selective laser sintering (SLS) of cylindrical steel specimens (3.0% C, 3.0% Cr, 1.0% Si, 12.0% V, Fe balance) 30 mm long and 5 mm in diameter by rapid prototyping. It was demonstrated that monolithic steel material could be successfully fabricated by this technology. Differential thermal analysis (DTA), scanning electron microscopy (SEM), and x-ray diffractometry (XRD) were used to study the microstructure, phase, and chemical composition of the source material and obtained specimens. Low-melting cementite-based eutectic was found to provide the liquid phase sintering of powder tool steel. The porosity of the green sintered specimens did not exceed 5%. The mean hardness value of sintered specimens was 825 HV.     

粉末烧结激光快速成形数字化制模技术及应用

快速成形技术是将三维CAD模型直接转化成为铸造用模的新技术。介绍了粉末烧结激光快速成形数字化制模的原理，探讨了在产品开发设计、精密铸造用蜡模、精密铸造用砂型、直接烧结金属零件和模具等方面的应用。与传统制模方法相比，具有速度快、精度高、价格便宜等优点。     

选择性激光烧结宝珠覆膜砂的固化特性研究

采用自制宝珠覆膜砂,应用选择性激光烧结(SLS)法成形出系列“8”字试样,然后在不同填充方式和温度下对SLS试样进行加热烘烤.测试试样的拉伸强度和1000℃下的发气量,并利用电子显微镜观察断口形貌.最后得到了覆膜砂烧结件最优的后处理工艺,即填充玻璃微珠,烘烤温度200℃.得到的材料抗拉强度最大为6.28 MPa,发气量最小为18.43 ml/g,能很好满足浇铸要求.     

激光快速成型用覆膜砂工艺参数研究

对铸造覆膜砂的激光快速成型进行了试验研究。系统研究了澈光功率、扫描速度、预热温度、铺粉厚度等工艺参数对成型试样质量的影响。结果表明：获得铸造用激光快速成型砂型试样的最佳工艺参数为；激光功率21W，扫描速度900mm/s，预热温度70℃，铺粉厚度0．2mm。     

选择性激光烧结翘曲变形模拟

建立了烧结过程的温度场、弹性应力应变场的有限元计算模型,开发了C++模拟软件,模拟了选择性激光烧结(SLS)过程的温度、残余热应力的演化,以及最终的翘曲变形.提出的改进移动热源加载算法提高了计算速度.研究结果表明:激光烧结过程中温度场不均匀,导致了热应力的产生,进而使制件变形,制件的上下部分收缩不一致,从而向上翘曲.随...     

覆膜砂选择性激光烧结过程的建模研究

建立选择性激光烧结粉末的快速成型工艺过程的数值计算模型,并用于估算热固结宽度和深度.在该计算模型中,综合考虑了材料的热物性参数随温度变化的情况和激光光强分布不均匀的因素,采用Ansys有限元分析软件模拟计算激光点加热过程覆膜砂的热影响区大小,结果与实验吻合较好.     

影响激光快速成形制芯工艺精度的关键

分析了烧结过程中的工艺参数、预固化及成形后固化处理等关键工序对快速成形工艺制芯精度的影响.并根据某缸盖#5砂芯尺寸大小、厚薄和形状的复杂程度,以及材料的特性,选择合适的激光功率和扫描速度、预热温度、分层方向、分层厚度、扫描间距和扫描方向等工艺参数,最终使试制的砂芯在允许的尺寸偏差内,实现了成套砂型装配,并浇注出合格的铸件.     

Application of transparent casting moulds prepared by additive manufacturing technology in hydraulic simulation

Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process. However, it only performs on test pieces with relatively simple structures due to the limitation of the preparation method. In this study, the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin. The pouring test was carried out under different centrifugal conditions, and the filling process of the gating system, support bars and other positions in the vertical direction was recorded and analyzed. The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly. The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases, which means the filling process is carried out from outside to inside at high rotational speed. The velocity of the fluid entering the runner increases with the increase of rotational speed, but the filling speeds is less affected by the centrifugal speed at other positions. The liquid flow is continuous and stable during the forward filling process, without splashing or interruption of liquid droplets.

     

Ni-CuSn混合粉末选区激光烧结试验

通过对双组分Ni-CuSn混合粉末进行激光烧结试验,表明此组粉末体系成形机制是粉末半熔化状态下的液相烧结机制。详细讨论了激光工艺参数对成形机制及烧结质量的影响,结果表明,将激光功率和扫描速率控制在适宜的范围内,才可实现预期的成形机制,并获得较好的烧结质量。对烧结件显微组织分析表明,组分M和CuSn间存在较为明显的熔点差、及两者之间较高的固溶度,是保证液相烧结机制、获得较高烧结致密度的前提。     

复杂内腔结构金属零件的快速制造

介绍了一种通过激光烧结砂芯快速制造具有复杂内腔构造金属零件的方法,通过案例归纳了该种方法的技术特点和应用范围。