铸造模拟技术应用实例

计算机模拟技术的应用,为铸造工艺设计提供了一种新的工具。通过流场、温度场的计算,使用判据功能可以找出铸造缺陷部位,采取相应措施优化工艺,能缩短试制周期、提高产品质量、降低成本。     

Microstructural characterization of Mg–Al–Sr alloys

The microstructural details of fourteen Mg–Al–Sr alloys were investigated in the as-cast form by a combination of scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis and quantitative electron probe microanalysis (EPMA). The heat transfer method coupled with the DSC measurement has been utilized to determine the solidification curves of the alloys. The morphology and the chemical composition of the phases were characterized. The microstructure of the alloys is primarily dominated by (Mg) and (Al₄Sr). In the present investigation, ternary solid solubility of three binary compounds extended into the ternary system has been reported and denoted as: (Al₄Sr), (Mg₁₇Sr₂) and (Mg₃₈Sr₉). The (Al₄Sr) phase is a substitutional solid solution represented by Mg_xAl_4–xSr and has a plate-like structure. The maximum solubility of Al in Mg₁₇Sr₂ was found to be 21.3 at%. It was also observed that Mg₃₈Sr₉ dissolved 12.5 at% Al.     

合金元素对喷射成形超高碳钢组织的影响

对喷射成形超高碳钢的化学成分进行了交叉设计,以确定各元素成分对组织的影响。研究表明:Si并不足以单独阻止喷射成形超高碳钢晶界碳化物的出现,A l对抑制晶界碳化物的生成有很大作用,Cr对晶界碳化物的生成有明显抑制作用,C对超高碳钢晶界碳化物的生成有直接影响。     

Effect of high-pressure rheology of lubricating oils on boundary lubrication

High-pressure rheology of lubricating oil was determined using different experiments, and the phase diagram was drawn. The four-ball wear tests were used to evaluate anti-wear characteristics of oils in boundary lubrication condition. The bridged ring compound oils showed the minimum wear scar in the four-ball wear tests. The diameter of wear scar decreases with increasing the elastohydrodynamic film-forming capability. Next, we considered the molecular packing parameter T_VE−T at the four-ball wear test. The T_VE−T values of bridged ring compound oils were in the range 250-360 and oils were elastic-plastic solid. It is concluded that the solidified oil film under boundary lubrication conditions has the anti-wear action.     

Assessment of the atomic mobilities for ternary Al–Cu–Zn fcc alloys

Abundant experimental diffusion data were evaluated to assess the atomic mobilities for the fcc phase of the Al–Cu, Cu–Zn and Al–Cu–Zn systems. Comprehensive comparisons show that good agreements were obtained between calculated and experimental values not only for the diffusion coefficients, but also for diffusion/solidification processes resulting from interdiffusion, such as the Kirkendall shift and solidification curve.     

金属-气体共晶定向凝固制备藕状多孔金属的研究

金属-气体共晶定向凝固(Gasar)是一种制备规则多孔金属的新工艺.利用自行开发的Gasar装置,成功制备了具有规则气孔分布的藕状多孔金属Mg,并研究了铸型预热温度和气体压力等工艺参数对气孔率、气孔大小和分布的影响.结果表明:提高铸型预热温度可以完全消除无气孔金属壳;随着氢气压力的增大,铸锭的平均直径都在减小;在整个Gasar凝固中约有8%左右的氢气溢出.     

高红外技术在家用电器外壳粉末喷涂中的应用

长沙中意冷柜厂对冷柜外壳粉末喷涂生产线的固化炉进行改造，采用高红外加热固化技术代替了传统的固化工艺，不仅提高了劳动生产率，并且解决了原工艺固化不完全的缺陷。实践证明高红外技术应用于家电外壳的粉末涂装是切实可行且具有优越性的。     

连铸钢水过热度对铸坯凝固的影响

连铸钢水的过热度是影响铸坯内外质量和产量的关键因素之一,因此在生产中控制过热度及其波动十分重要,为此要准确估计出钢后到连铸中间罐的钢水热损失,而根据生产数据和经验构筑的控制过热度的过程模型具有应用价值。     

Research on solidification structure refinement of pure aluminum by electric current pulse with parallel electrodes

The influence of electric current pulse (ECP) with parallel electrodes on the solidification structure of pure aluminum has been investigated. The experimental results indicate that the solidification structure cannot be refined when the ECP is applied before the molten metal starts nucleating. However, significant refinement of the solidification structure can be achieved by applying ECP during the nucleation stage. In addition, under the same cooling conditions, ECP with parallel electrodes has better refinement effect than ECP with up–down electrodes. The refinement mechanism of ECP with parallel electrodes has also been proposed.     

Studies on transport phenomena during solidification of an aluminum alloy in the presence of linear electromagnetic stirring

Numerical and experimental studies on transport phenomena during solidification of an aluminum alloy in the presence of linear electromagnetic stirring are performed. The alloy is electromagnetically stirred to produce semisolid slurry in a cylindrical graphite mould placed in the annulus of a linear electromagnetic stirrer. The mould is cooled at the bottom, such that solidification progresses from the bottom to the top of the cylindrical mould. A numerical model is developed for simulating the transport phenomena associated with the solidification process using a set of single-phase governing equations of mass, momentum, energy, and species conservation. The viscosity variation of the slurry, used in the model, is determined experimentally using a rotary viscometer. The set of governing equations is solved using a pressure-based finite volume technique, along with an enthalpy based phase change algorithm. The numerical study involves prediction of temperature, velocity, species and solid fraction distribution in the mould. Corresponding solidification experiments are performed, with time–temperature history recorded at key locations. The microstructures at various temperature measurement locations in the solidified billet are analyzed. The numerical predictions of temperature variations are in good agreement with experiments, and the predicted flow field evolution correlates well with the microstructures observed at various locations.