乳剂熔化工序对印刷胶片性能的影响因素探讨

本文主要论述了乳剂熔化过程中光谱增感、过滤精度和静置时间等因素对印刷胶片性能的影响,归纳出印刷胶片生产的一个优选方案.     

电渣连铸技术的开发

在结合电渣重熔和连铸技术优点的基础上。东北大学钢铁冶金研究所采用双极串联、交换电极及在线切割等技术，在国内首次成功地开发了电渣连铸（ESCC）技术；解决了电渣重熔钢锭直径小于300mm时熔速很慢、冶炼费用很高的难题。通过对重熔方坯质量的低倍、高倍、夹杂物检验等分析表明，该技术生产的方坯表面质量和内部质量良好，具有广泛应用前景和经济价值。     

电渣炉智能控制系统的开发与应用

递减功率熔炼控制被认为是保证电渣炉钢锭质量的有效的控制方法。根据电渣工艺优化的要求，开发了基于递减功率熔炼控制为核心的电渣炉智能控制系统。该系统具备连续有载调压和电极插入位置精确控制的功能。系统在近20台工业电渣炉上得到应用，实际运行结果表明系统可靠性高、运行稳定、人机界面好、易于操作和维修，能达到预期的各项工艺操作控制要求，特别是在保证钢锭结晶质量、降低电耗和加快生产节奏方面效果明显。     

Partial Remelting of Thixotropic Magnesium-Rare Earth Alloy from Near Non- Equilibrium- Liquidus Casting

After the investigation on partial remelting of thixotropic magnesium serial alloys （ZK60） by near non-equilibrium liquidus casting （NNLC）, the primary solid grains of ZK60-2Ca alloy spheroidized notably during partial remelting processing, however, coarsening and polygonization as occurred holding time prolonged. The refining and globularity of the thixotropic alloys are promoted after further alloyed by Y, RE, Nd and/or Ag, and the results vary with those addition. The remelting structure of ZK60-2Ca-1Y alloy is finer than its base alloy. And the effect of RE, especially Ag, on the refinement of microstrueture is notable, but Nd does nothing on it. There is little impact of remelting temperature fluctuation on partial remelted microstrueture as holding time in general. On the contrary, it is more sensitive at longer holding time. The quality thixotropic silver-contained alloy can be achieved by remelted partially at 600℃ for 10 min.     

薄板模具钢脉冲Nd:YAG激光熔凝试样 变形量的测量

在厚度为0.3～0.8 mm的5Cr4Mo3SiMnVAl(012Al)模具钢和Cr12MoV模具钢薄板上，采用脉冲Nd:YAG激光进行了激光熔凝实验，研究了工艺参数(脉冲宽度和脉冲频率)、材质和材料厚度对激光熔凝后试样厚度方向上最大变形量的影响。结果表明，激光熔凝薄板模具钢所引起的变形相当严重，其最大弯曲变形量与材料厚度为同一个数量级；随着脉冲频率的减少或脉冲宽度的增加或材料厚度的减少，试样厚度方向上的最大弯曲变形量增大；Cr12MoV钢试样厚度方向上的最大弯曲变形量比012Al钢的大。激光熔凝工艺参数、材料的热扩散情况和材料的热物性参数的不同是造成上述现象的主要原因。     

Process parameter dependencies of continuous and pulsed laser modes on surface polishing of additive manufactured aluminium AlSi10Mg parts

Laser powder bed fusion is a well-established 3D printing technique for metal alloys, but exhibits a poor surface quality. Laser polishing provides the possibility of a fast contact-free and fully-automatable surface treatment. This paper deals with the experimental investigation of laser polishing of laser powder bed fusion parts made of aluminium AlSi10Mg. Laser polishing is done with a 4 kW solid state disc laser in combination with a multi-axis system and a one dimensional scanner optic. The laser is operated at continuous and pulsed operation mode. The parameter study reveals a high dependency of the achievable roughness on the laser beam intensity, the track and pulse overlap, the energy density and the number of polishing passes and polishing directions. Pulsed laser polishing mode with up to four passes from different directions revealed the lowest surface roughness of 0.14 μm Ra. With respect to the initial average surface roughness of Ra = 8.03 μm a reduction of the surface roughness of greater than 98 % could be achieved. Polishing with continuous laser radiation at one polishing pass resulted in Ra = 0.23 μm at an area rate of 20 cm²/min. Laser polishing using four passes achieved a further improvement up to Ra = 0.14 μm.     

0Cr17Ni4Cu4Nb零件端面黑点原因分析

通过宏观观察、光学显微分析、电镜扫描等分析手段对0Cr17Ni4Cu4Nb零件端面黑点进行分析。结果表明:黑点缺陷的显微组织存在异常,与基体组织存在轻微的过渡层,缺陷周围不存在氧化及脱碳现象,导致零件产生黑点的原因为电渣重熔过程中产生了异金属夹杂。     

Optical investigation of the behavior of the electric arc and the metal transfer during vacuum remelting of a Ti alloy

High-speed camera imaging and optical emission spectroscopy have been used for investigating the structure of the electric arc and the transfer mechanisms of the liquid metal during vacuum arc remelting (VAR) of Ti alloys. The arc exhibited a similar operating regime to that described in the previous literature for the case of Inconel 718 and zirconium alloy electrodes. The arc behaved in a diffuse mode with many separate and rapidly moving cathode spots. Several parameters of the cathode spots, including their current, size and apparent velocity were evaluated. The application of an external axial magnetic field tended to encourage the cathode spots to locate themselves on the base of the electrode. A large density ratio of Ti⁺ ions and Ti atoms in the interelectrode plasma was evaluated, suggesting that the plasma was strongly ionized. The calculated excitation temperature of Ti⁺ ions (1–1.2 eV) was about 1.5–2 times greater than that obtained for Ti atoms. The transfer mechanisms of the drops of liquid metal might be classified into three main modes depending on the gap length: drop falling, drip short and drop erosion induced by the cathode spots. The importance of the influence of the arc on the metal transfer mechanisms was inversely related to the gap length.