非规则管坯喷射沉积成形工艺优化及试验验证

提出了基于往复式喷射成形工艺制备大璧厚非规则管坯的近终形成形工艺及其工艺参数优化方法,以实现坯件从CAD设计到喷射成形的快速制备过程。该工艺方法包括三个阶段:非规则管坯的三维CAD设计、分层处理和单层沉积厚度计算;基于沉积厚度与往复速度和质量流率的对应关系,计算满足各层沉积厚度所对应的控制参数;利用控制系统和执行机构对控制参数进行实时控制和调节,采用往复式多层喷射成形工艺制备满足设计轮廓的管坯。通过试验进行了验证,喷射成形制备的管坯形状和轮廓与CAD设计模型较好地一致,表明了该工艺方法的可行和正确性。     

喷射成形Cu-15Ni-8Sn合金的显微组织和性能研究

采用喷射成形技术制备了Cu-15Ni-8Sn(%,质量分数)合金坯锭,利用光学显微镜和扫描电子显微镜观察分析了合金坯锭的微观组织和成分分布;利用拉伸实验测量了坯锭试样的力学性能。结果表明,喷射成形工艺制备的Cu-15Ni-8Sn合金沉积坯底部和中部位置的微观组织存在较大差异,底部微观组织由多相组成,其余部位基本为单相α固溶体;合金中的大量孔洞降低了喷射成形Cu-15Ni-8Sn合金的致密度和力学性能。     

喷射成形高钒高速钢环坯制备技术研究

采用喷射成形技术制备高钒高速钢环坯,阐述了喷射成形制备过程方法及工艺参数,制备得到的沉积坯收得率为83.5%。对比观察沉积坯不同位置组织及碳化物形貌,发现:组织均匀细小,碳化物颗粒细小、形状较为规则、分布均匀,合金元素无宏观偏析;孔隙及缺陷主要位于沉积坯与基体的结合界面附近,产生于喷射沉积未完全稳定的试验初期。对热处理后的沉积坯试样进行硬度测试,喷射成形高钒钢淬火硬度为63HRC,高于粉末冶金高钒钢;经过3次回火,硬度逐渐下降,未出现二次硬化现象。     

喷射成形过共晶AlSi合金锭坯的渐变组织研究

喷射成形是通过控制凝固条件,使金属熔体经过雾化分散、飞行快速冷却、半固态凝固及形成锭坯后进一步冷却等阶段,得到特殊的喷射成形锭坯组织的成形过程.沉积锭坯组织是上述四个阶段金属熔体凝固的综合结果.由于散热条件的不同,沉积锭坯组织形态随沉积位置而变化.本文分析了喷射成形锭坯组织的变化情况和形成原因.     

制备复相结构陶瓷坯件的自反应喷射成形工艺研究

以Ti粉、B4C粉和蔗糖(C的前驱体)为原料,采用自反应喷射成形技术在石墨模具内制备了Ti(C,N)-TiB2复相结构陶瓷坯件,研究了自反应喷射成形技术中几个关键工艺参数如气粉质量流率比(G/C值)、喷射距离和喷射团聚粉预热温度对制备该复相陶瓷坯件的影响。研究表明,对喷射沉积坯件孔隙度影响由主到次的参数依次为G/C值、喷射距离和预热温度。正交试验结果得出,利用Ti-B4C-蔗糖体系制备Ti(C,N)-TiB2复相陶瓷坯件的最佳工艺条件是:G/C值为11、喷射距离为220mm,复合粉预热温度为210℃。所制备复相陶瓷坯件组织结构均匀、致密,主要由TiC0.3N0.7、TiB2与TiO2相及少量孔隙组成;其中TiC0.3N0.7和TiB2为主相,TiO2为副产物相;坯件孔隙度为2.9%,维氏硬度、抗弯强度和断裂韧度分别为17.3GPa、387MPa和6.0MPa.m1/2。     

喷射成形工艺的理论研究进展

喷射成形是人为地控制凝固条件,经过金属熔体的分散、飞行快速冷却、半固态凝固及锭坯进一步冷却等阶段,得到特殊的锭坯组织的成形过程。沉积锭坯组织是上述四个阶段金属熔体凝固的综合结果。近终形成形是喷射成形技术的另一特点,喷嘴形式、喷嘴数量、沉积器的形状与运动方式影响和决定沉积锭坯的外形。材料的凝固与成形受众多因素影响,很多工艺参数的作用规律尚不明确,因此喷射成形过程的模拟研究十分必要。笔者介绍了目前喷射成形工艺中所涉及的理论问题与相关模型。     

喷射成形2060高速钢的组织与性能

利用雾化沉积炉制备喷射成形2060高速钢沉积坯,经过锻造后再进行盐浴淬火和回火处理,研究喷射成形2060高速钢及其热处理后的组织与力学性能。结果表明:喷射成形2060高速钢沉积坯的表面较光洁,无明显的宏观偏析,晶粒较细小,晶粒尺寸约为20μm,沉积坯的相对密度在99.5%以上;沉积坯中主要存在M6C和MC两种碳化物相,均匀弥散分布在晶界与晶内以及基体中,氧含量只有1.6×10-7左右。2060高速钢的抗弯强度随淬火温度升高而逐渐降低,淬火温度应低于1 210℃。在1 170~1 190℃下淬火时可获得抗弯强度≥3 000MPa、硬度≥70 HRC的良好综合力学性能。     

基于凸轮驱动喷嘴分阶段变速扫描的锭坯喷射均匀沉积研究

喷射成形技术可以制备出高性能、高质量的工业锭坯,对工业的发展具有重要影响。雾化喷嘴系统是喷射成形装置的核心,喷嘴扫描运动方式对锭坯的均匀沉积有着重要的作用。本文以锭坯均匀沉积为目标,提出了基于凸轮驱动的参数可调的喷嘴扫描方式,建立了喷嘴分阶段变速扫描过程,确定了凸轮形状,对锭坯沉积轨迹进行了仿真并做了分析。最后用喷射成形实验对喷嘴分阶段变速扫描进行了验证,表明了其正确性。     

喷射成形沉积坯与过喷粉末的比较分析

喷射成形是近年来发展极其迅速的一种崭新的金属和合金成形技术.使用金相显微镜,扫描电镜对GCr15钢喷射成形试样和过喷粉末的微观组织和晶粒度进行了比较分析.结果表明:喷射成形过喷粉末为枝晶组织,而喷射成形沉积坯由于雾化气体的雾化破碎作用,组织为细小等轴晶;过喷粉末的尺寸主要集中在35～80μm之间;而沉积坯上的晶粒度主要集中在80～120 μm之间.     

喷射成形高温合金组织演变过程试验研究北大核心CSCD

采用Gleeble 3500热模拟机等试验方法研究了喷射成形高温合金GH4169沉积坯内部树枝晶组织向等轴晶组织的演变过程,并对雾化沉积过程中高温合金等轴晶组织的形成机理进行了分析。研究认为,高温合金熔体再辉时产生的热量与飞行熔滴撞击到沉积坯时动能转化产生的热量,造成了喷射成形雾化熔滴中的枝晶重熔,加上熔滴沉积撞击时产生的大量枝晶碎片,在沉积坯半液态层中生成了大量结晶核,是喷射成形高温合金等轴晶组织形成的重要原因。     

Metal Spray Forming Process Examined Using Mathematical Model

The metal spray forming process was examined using the mathematical model simulation by Baosteel＇s test and developed facilities.The mathematical model comprised of the probability and statistical analysis of the droplet mass behavior and predicted the shape and temperature distribution of the billet during the spray forming process.     

喷雾阀嘴多步成形有限元分析

喷雾阀嘴是喷雾罐的关键部件,其成形过程复杂、难度较大。采用三维光学扫描仪检测喷雾阀嘴各步成形件的三维尺寸,推导模具方案进行逆向建模。同时采用有限元技术分析喷雾阀嘴成形过程特点,探索材料性能对其成形质量的影响。结果表明,模型实现了精确分析喷雾阀嘴复杂的多步成形过程,可分析喷雾阀嘴任一时刻、任一位置的成形状态和成形质量状况。同时得出,MR T3-BA材料或比其屈服强度更高的材料容易出现成形质量问题。     

Experimental and mathematical modeling of metal spray forming process

The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel’s test and development facilities.The mathematical model comprised of four sections,including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior,and forecast of the shape and temperature distribution of the billet during the spray forming process.     

Modelling of droplet dynamic and thermal histories during spray forming—II. Effect of process parameters

A computer model has been developed to describe the in-flight dynamic and thermal histories of gas atomised droplets as a function of distance during spray forming. The model has been used to investigate the effects of the dynamic and thermal behaviour of individual gas atomised droplets and the cooling and solidification behaviour of the overall spray. The most influential parameters for a given alloy system, in order of importance, are: (i) droplet diameter and, therefore, the droplet size distribution within the spray; (ii) initial axial gas velocity at the point of atomisation and the subsequent gas velocity decay profile; (iii) melt mass flow rate; (iv) melt superheat at the point of atomisation; and (v) alloy composition. Experimental measurements of gas velocities and droplet size distributions during spray forming allow the spray solid fraction at deposition to be calculated and used in a subsequent computer model of billet heat flow to predict the billet top surface temperatures and solid fractions.     

Formulation of rod-forming models and their application in spray forming

In rod spray forming, the preform changes its shape continually from that of a disc to a rod (transient-state rod growth) and then maintains its top surface profile once it has settled down (steady-state rod growth). The rod growth mechanism during spray forming was analyzed using rod-forming models. At a sufficiently high substrate rotation velocity, the calculated results based on the three-dimensional time-dependent model (3-D TDM) and the two-dimensional time-dependent model (2-D TDM) were observed to be identical. The calculated results of the rod’s top shape, obtained by the TDMs, were almost identical to those obtained by the two-dimensional time-independent model (2-D TIM), which means that there exists steady-state rod growth. The effects of spray-forming parameters, such as initial eccentric distance, substrate withdrawal velocity, and spray angle, on the shape-evolution behavior were analyzed in terms of the vertex growth velocity ( ). The optimum spray-forming condition to minimize transient-state rod growth was also presented. Experimental verification was made to confirm the proposed forming models.     

喷射成形过程中圆锭坯外形生长的数值模拟

通过多次试验后得出雾化喷嘴的雾化特性公式,在此基础上建立了一种模拟喷射成形过程中圆锭坯外形生长的数学模型.该数学模型考虑了喷射成形过程中各种工艺参数,如喷嘴的雾化参数、偏心距离、沉积盘的旋转速度和下拉速度等参数的影响.经过模拟计算,得到了锭坯生长的三维外形尺寸,与实际喷射成形制备的锭坯外形对比,二者吻合很好;采用该模型分析了不同时间下锭坯的轮廓形状、偏心距离以及下拉速度变化后的锭坯轮廓形状.综合分析得出,此数学模型可以预测在不同工艺参数下喷射成形锭坯的外形生长过程.     

A three-dimensional model of the spray forming method

A three-dimensional model has been formulated to calculate the shape of the general preform, using vector calculus. The shape of a rod, tube, plate, or irregular preform can be calculated at given spray forming conditions. The shape of a spray-formed rod was analyzed at various spray forming conditions using the three-dimensional model. The effects of spray forming parameters, such as spray distribution parameters, angular velocity of rotation, withdrawal velocity, spray angle, and eccentric distance on rod shape, were analyzed. The most important parameters affecting the shape of rods are the spray distribution parameters and the withdrawal velocity. The dynamic evolution of rod shape with a stepwise variation of the withdrawal velocity during spray forming was investigated. The effect of a stepwise change of the withdrawal velocity was the same as that of the scanning atomizer. The calculated surface profiles were compared with those of spray-formed 7075 aluminum alloy rods prepared on a pilot scale. The calculated results for the surface profiles were in agreement with those of the spray-formed rods.     

非稳定流动对喷射成型制备圆锭成型性的影响

利用计算机数值模拟技术与实验相结合的方法,着重研究了喷射成型过程中、中间包坩埚中金属熔体液高度对雾化锥的雾密度函 影响,以及对喷射成型制备圆锭的成型性的影响。     

喷射成形与传统熔炼高速钢M2的组织与力学性能研究

通过喷射成形和传统熔炼（中频冶炼+电渣重熔）两种工艺生产了高速钢M2（W6Mo5Cr4V2）试样，利用金相显微镜和M-200磨损试验机对同规格同位置的两种试样的退火组织、非金属夹杂物、淬回火硬度、显微组织和力学性能进行了研究。结果表明，喷射成形M2试样的碳化物分布均匀、尺寸细小，传统熔炼M2试样碳化物呈条带状分布；在相同热处理制度和位置下，喷射成形M2试样的回火硬度与传统熔炼M2试样相当；喷射成形M2试样的耐磨性要比传统M2试样提高约41%；喷射成形M2试样中尺寸大于2μm的MC类碳化物数量明显多于传统M2试样，使得在同等硬度下喷射成形M2试样的耐磨性能要优于传统M2试样。由此可知，喷射成形M2试样的组织及力学性能均优于传统熔炼M2试样，喷射成形技术具有工艺先进性。