铁—碳—铜粉末净成形工艺的数值模拟研究

发布时间：2018-11-11 08:55

【摘要】：随着粉末冶金行业的迅速发展,实现复杂形状、高密度、高性能的粉末冶金产品十分迫切。将数值模拟技术应用于粉体成形中,可有效预测产品质量,降低生产周期和成本。压坯密度大小及均匀性是影响粉末冶金产品质量的主要因素,故本文采用数值模拟对铁碳铜粉末的压制规律进行了以下研究:1.针对Fe-2%Cu-0.8%C成分粉末建立材料参数模型,并结合椭球屈服准则和修正的库伦摩擦模型,建立了 Fe-2%Cu-0.8%C粉末压制的有限元模型。通过实验与模拟的对比验证所建立的有限元模型的可靠性。在此基础上,对压制方式、压制速度、摩擦系数、是否保压等工艺参数正交优化,得到最佳工艺参数。2.对简单圆柱体的压制成形过程分析,探索压制方式、摩擦状况、高径比等工艺因素对坯块密度的分布情况的影响。由定性和定量分析,得到压坯密度极差△ρ与高径比AR的线性关系,并提出双向压制提高密度均匀性的效果是有限的、与高径比有关。本文还研究了弹性回复现象,得到脱模后的节点密度下降量δ与高径比AR呈线性关系。此外,对非同步双向压制的密度分布规律研究得到其密度均匀性取决于先、后动作的模冲压下量。采取先动作模冲的压下量接近所需的总压下量,之后另一模冲轻微反向压制到最终尺寸的方法,可大大提高密度均匀性。3.对"凸"字形台阶零件进行三维压制模拟,通过不同的模冲形式、模冲动作方案比较,得到保证台阶件压制时各区域均匀致密化、减小裂纹倾向的工艺原则。4.对带台阶机械盘的粉末锻造工艺优化,从金属流动规律、锻件成形性、密度均匀性、锻件损伤及模冲载荷五个方面比较了不同的锻造方案,提出适合带台阶零件粉末锻造的改进工艺。此外,对预成形坯初始密度、锻造温度、模具温度、摩擦系数对粉末锻造的影响进行详细分析,优化粉末锻造工艺参数。
[Abstract]:With the rapid development of powder metallurgy industry, it is urgent to realize complex shape, high density and high performance powder metallurgy products. The application of numerical simulation in powder forming can effectively predict product quality and reduce production cycle and cost. The compaction density and homogeneity are the main factors that affect the quality of powder metallurgy products, so the compaction law of iron, carbon and copper powder is studied by numerical simulation in this paper: 1. The material parameter model of Fe-2%Cu-0.8%C powder is established, and the finite element model of Fe-2%Cu-0.8%C powder compaction is established by combining the ellipsoid yield criterion and the modified Coulomb friction model. The reliability of the established finite element model is verified by comparison of experiment and simulation. On the basis of this, the optimum process parameters, such as pressing mode, pressing speed, friction coefficient and keeping pressure, are optimized by orthogonal method. 2. 2. This paper analyzes the forming process of simple cylinder, and explores the influence of pressing mode, friction condition, height to diameter ratio on the distribution of block density. By qualitative and quantitative analysis, the linear relationship between density difference 蟻 and height / diameter ratio (AR) is obtained, and it is pointed out that the effect of bi-directional compaction to improve density uniformity is limited, which is related to the ratio of height to diameter. The elastic recovery phenomenon is also studied, and the linear relationship between the node density drop 未 and the aspect ratio (AR) is obtained. In addition, the density distribution of non-synchronous bi-directional compaction is studied. It is found that the density uniformity depends on the die impact reduction of the first and the second action. The density uniformity can be greatly improved by adopting the method that the reduction of the first action die impulse is close to the required total reduction amount, and then the other die impulse slightly reverse compacts to the final size. The three-dimensional compaction simulation of "convex" zigzag step parts is carried out. Through the comparison of different die impact forms and die impact action schemes, the technological principles are obtained to ensure the uniform densification of every region and to reduce the crack tendency during step pressing. 4. Different forging schemes are compared from five aspects: metal flow rule, forging formability, density uniformity, forging damage and die impact load. An improved technology for powder forging of parts with step is put forward. In addition, the effects of initial density, forging temperature, die temperature and friction coefficient on powder forging were analyzed in detail to optimize the technological parameters of powder forging.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TF123

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