GH3625合金中的夹杂物及纯净化研究

发布时间：2018-01-18 12:32

本文关键词：GH3625合金中的夹杂物及纯净化研究　出处：《兰州理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：高温合金通常作为各类发动机和燃气轮机中的关键服役材料,要求其具有优异的冶金质量,尤其要最大限度的控制材料中的微量有害杂质元素(O、N、S)含量以及这些杂质元素形成的非金属夹杂物。因此,本文针对铸态GH3625合金中的夹杂物和纯净化工艺进行了一系列研究:利用JMat Pro软件计算GH3625合金的平衡相图表明,当合金中含有气体杂质元素O、N时,在液相线温度以上会形成以Al为主要元素的氧化物夹杂M2O3(Al2O3),在固液两相区生成以Ti为主要元素的氮化物夹杂MN(Ti N),且非金属夹杂物M2O3、MN的含量分别由O、N含量控制;其中非金属夹杂物及一次碳化物的析出过程为:L+M2O3→L+M2O3+γ→L+M2O3+γ+MN→L+M2O3+γ+MN+MC(Nb C)。讨论双联工艺熔炼GH3625合金各工艺阶段合金锭合金成分、杂质元素含量、铸态组织发现,电渣重熔后合金成分更加均匀,合金锭头尾及横截面合金元素偏差小于±0.1%;S、O含量分别降低至10、7ppm,脱除率分别为58%,59%;二次枝晶间距增大,Nb C由颗粒状变为汉字体状。各阶段铸锭中最主要的偏析元素为Nb,尤其是铸锭心部枝晶间偏聚大量的Nb C、Laves相。非金属夹杂物金相原位观察和电解提取夹杂物分析共同表明,GH3625合金中的夹杂物主要为氮化物(Ti,Nb)N和复合型氧化物Mg O·Al2O3尖晶石,尺寸在2~3μm之间;合金中的氮主要来源于冶炼原材料Cr、Mo;真空感应熔炼时氧化物夹杂主要来源于Mg O炉衬材料,而电渣重熔时氧化物夹杂是由渣系组元进入合金基体而形成。选用高真空感应重熔精炼工艺在GH3625母合金的基础上做进一步净化处理表明,高真空感应重熔时元素挥发烧损和富化均控制在标准成分范围;单纯高真空感应重熔时,合金中的氧通过C-O反应脱除,可脱氧至10ppm,氮分压降低使氮含量脱至70ppm,但在去硫方面无明显作用;高真空加0.5%钙作净化剂重熔时,Ca-O反应以及Ca与Al2O3坩埚内壁反应可实现深度脱氧,通过Ca-S反应使合金中硫含量显著降低,然而氮含量降低程度有限,其含量远高于氮在GH3625合金中的溶解度。采用Al2O3坩埚,选择高真空熔炼工艺及适量钙的加入,可使氧、氮、硫含量分别降低到6、60、9ppm。
[Abstract]:High temperature alloy usually as a key engine and gas turbine in service materials, with its excellent metallurgical quality, especially to trace impurity elements control the material maximum in (O, N, S) and the content of non-metallic inclusions of these impurities formed. Therefore, in this paper, a series of studies for inclusion casting state GH3625 alloy and purification process were: indicates that the equilibrium phase diagram calculation of GH3625 alloy by using JMat Pro software, when the alloy contains gas impurity elements O, N, Al as the main element of the formation of oxide inclusions in M2O3 above the liquidus temperature (Al2O3), produced by Ti as the main element of the nitride the MN inclusion in the solid-liquid zone (Ti N), and M2O3 non metallic inclusions, the content of MN by O, the content of N control; the precipitation process of non metallic inclusions and primary carbides are: L+M2O3, L+M2O3+, L+M2O3 gamma +MN - L+M2O3+ + gamma gamma +MN+MC (Nb C). To discuss the process by double melting GH3625 alloy process stages alloy ingot alloy composition, impurity content, microstructure, ESR after the alloy composition is more uniform and the alloy ingot ends and cross section of alloy element deviation is less than 0.1% S, the content of O were decreased; to 10,7ppm, the removal rate were 58%, 59% and two; the dendrite spacing is increased, Nb C by granular body shape into Chinese characters. The main elements of each stage in the ingot segregation of Nb, especially the heart of ingot interdendritic segregation of Nb C, Laves phase. Non metallic inclusion analysis metallographic in situ observation and electrolytic extraction of inclusions shows that the inclusions in GH3625 alloy mainly nitrides (Ti, Nb) N and Mg O - Al2O3 composite oxide spinel size between 2~3 m alloy; the nitrogen comes mainly from smelting raw materials Cr, Mo; vacuum induction melting of oxide inclusions Mainly from lining material Mg O, and ESR process is composed of oxide inclusion slag component into the alloy matrix formed. Using high vacuum induction remelting refining process based on GH3625 master alloy for further purification showed that high vacuum induction remelting when volatile elements have a fever loss and rich control in standard components simple range; high vacuum induction remelting, alloy oxygen removal by C-O reaction, can be deoxidized to 10ppm, nitrogen partial pressure reduced nitrogen removal to 70ppm, but no significant effect on desulphurization; high vacuum plus 0.5% calcium as a purifying agent of remelting, Ca-O reaction and Ca reaction and Al2O3 crucible wall can be realized deoxidation, through Ca-S reaction to the sulfur content in the alloy is significantly reduced, but the nitrogen content decreased, the content is much higher than that of nitrogen solubility in the GH3625 alloy. Using Al2O3 crucible, high vacuum melting process and the amount of The addition of calcium can reduce the oxygen, nitrogen and sulfur content to 6,60,9ppm., respectively.

【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG132.3

【相似文献】