(1.華南理工大學(xué)機(jī)械與汽車工程學(xué)院，廣州510640；
2.汕頭華興冶金設(shè)備股份有限公司，汕頭515063；
3.汕頭華興(饒平)銅業(yè)有限公司，饒平 515726)
摘 要: 本文采用立式連續(xù)鑄造制備直徑160mm的Cu-15Ni-8Sn合金鑄錠，并基于分形維數(shù)對(duì)Cu-15Ni-8Sn合金中組織非均勻性進(jìn)行了探究。結(jié)果表明：Cu-15Ni-8Sn合金的微觀組織由樹枝晶組織和偏析組織構(gòu)成，樹枝晶組織分形維數(shù)可以作為衡量微觀組織非均勻性的重要指標(biāo)。澆鑄溫度為1280℃時(shí)，隨著樹枝晶組織分形維數(shù)的增加(1.77~1.82)，偏析率從32%降低至12.5%。與此同時(shí)，大偏析點(diǎn)逐漸向小偏析點(diǎn)轉(zhuǎn)變，Ⅰ類偏析點(diǎn)面積占比從60%下降至10%，Ⅱ類偏析點(diǎn)面積占比從35%上升到80%；相對(duì)于二次枝晶間距，分形維數(shù)彌補(bǔ)了二次枝晶間距在描述Cu-15Ni-8Sn合金樹枝晶組織形貌特征上的局限性。此外，樹枝晶組織的分形維數(shù)與偏析組織的分形維數(shù)在一定程度上呈正相關(guān)關(guān)系。選擇較低的澆鑄溫度有利于得到偏析率較低、組織分布更加均勻的鑄錠。
關(guān)鍵字: Cu-15Ni-8Sn合金鑄錠；分形維數(shù)；偏析特征；立式連續(xù)鑄造
（1.School of Mechanical and Automotive Engineering, South China University of Technology,Guangzhou 510640, China;
2.Shantou Huaxing Metallurgical Equipment Co., Ltd.,Shantou 515063,China;
3. Shantou Huaxing (Raoping) Copper Co., Ltd., Raoping 515726, China）
Abstract:In this work, Cu-15Ni-8Sn alloy ingot with diameter of 160mm was prepared by vertical continuous casting. Based on fractal dimension, thestructureinhomogeneity in Cu-15Ni-8Sn alloy was investigated. The results show that microstructure of Cu-15Ni-8Sn alloy consists of dendrite structure and segregation structure, andthe fractal dimension of dendrite structure can be used as an important index to measure the microstructureinhomogeneity. Under the pouring temperature of 1280℃, with the increase of fractal dimension of dendrite structure, the segregation rate decreases from 32% to 12.5%. At the same time, the area proportion of segregation point Ⅰdecreases from 60% to 10%, and that of segregation point Ⅱincreases from 35% to 80%, which indicates that large segregation points gradually changeto small segregation points. Moreover, compared with the secondary dendrite spacing, the fractal dimension compensates forthe limitation of secondary dendrite spacing in describing the dendrite morphology of Cu-15Ni-8Sn alloy.Additionally, the fractal dimension of dendrite structure and the fractal dimension of segregation structure are positively correlated. Under the pouring temperature of 1280℃, the fractal dimension of segregation structure increases from 1.15 to 1.45 with the increase of fractal dimension of dendrite structure.The lower pouring temperature is beneficial to obtain the ingot with lower segregation rate and more uniform microstructure distribution.
Key words: Cu-15Ni-8Sn alloy ingot; fractal dimension; segregation characteristic; vertical continuous casting
