【摘要】：隨著粉末冶金行業(yè)的迅速發(fā)展,實(shí)現(xiàn)復(fù)雜形狀、高密度、高性能的粉末冶金產(chǎn)品十分迫切。將數(shù)值模擬技術(shù)應(yīng)用于粉體成形中,可有效預(yù)測產(chǎn)品質(zhì)量,降低生產(chǎn)周期和成本。壓坯密度大小及均勻性是影響粉末冶金產(chǎn)品質(zhì)量的主要因素,故本文采用數(shù)值模擬對(duì)鐵碳銅粉末的壓制規(guī)律進(jìn)行了以下研究:1.針對(duì)Fe-2%Cu-0.8%C成分粉末建立材料參數(shù)模型,并結(jié)合橢球屈服準(zhǔn)則和修正的庫倫摩擦模型,建立了 Fe-2%Cu-0.8%C粉末壓制的有限元模型。通過實(shí)驗(yàn)與模擬的對(duì)比驗(yàn)證所建立的有限元模型的可靠性。在此基礎(chǔ)上,對(duì)壓制方式、壓制速度、摩擦系數(shù)、是否保壓等工藝參數(shù)正交優(yōu)化,得到最佳工藝參數(shù)。2.對(duì)簡單圓柱體的壓制成形過程分析,探索壓制方式、摩擦狀況、高徑比等工藝因素對(duì)坯塊密度的分布情況的影響。由定性和定量分析,得到壓坯密度極差△ρ與高徑比AR的線性關(guān)系,并提出雙向壓制提高密度均勻性的效果是有限的、與高徑比有關(guān)。本文還研究了彈性回復(fù)現(xiàn)象,得到脫模后的節(jié)點(diǎn)密度下降量δ與高徑比AR呈線性關(guān)系。此外,對(duì)非同步雙向壓制的密度分布規(guī)律研究得到其密度均勻性取決于先、后動(dòng)作的模沖壓下量。采取先動(dòng)作模沖的壓下量接近所需的總壓下量,之后另一模沖輕微反向壓制到最終尺寸的方法,可大大提高密度均勻性。3.對(duì)"凸"字形臺(tái)階零件進(jìn)行三維壓制模擬,通過不同的模沖形式、模沖動(dòng)作方案比較,得到保證臺(tái)階件壓制時(shí)各區(qū)域均勻致密化、減小裂紋傾向的工藝原則。4.對(duì)帶臺(tái)階機(jī)械盤的粉末鍛造工藝優(yōu)化,從金屬流動(dòng)規(guī)律、鍛件成形性、密度均勻性、鍛件損傷及模沖載荷五個(gè)方面比較了不同的鍛造方案,提出適合帶臺(tái)階零件粉末鍛造的改進(jìn)工藝。此外,對(duì)預(yù)成形坯初始密度、鍛造溫度、模具溫度、摩擦系數(shù)對(duì)粉末鍛造的影響進(jìn)行詳細(xì)分析,優(yōu)化粉末鍛造工藝參數(shù)。
[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.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TF123

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