镁合金化对低碳钢组织及力学性能的影响

发布时间：2018-03-18 02:15

本文选题：低碳钢　切入点：氧化物冶金　出处：《安徽工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：论文以低碳钢为研究对象,研究了不同镁含量(0%、0.0016%、0.0021%、0.0033%和0.0064%)对低碳钢夹杂物特征(形貌、类别、成分、尺寸和分布)、显微组织、力学性能的影响,分析了低碳钢中夹杂物诱导IAF形核的机制。研究结果表明:(1)镁合金化可使低碳钢中夹杂物改性。镁合金化后低碳钢中单独的氧化铝夹杂和硫化锰夹杂均改性为圆形或近似圆形的尖晶石类复合夹杂物(主要为氧化镁-氧化铝-二氧化硅-硫化锰类复合夹杂物);镁含量为0.0064%时,夹杂物为氧化镁-二氧化硅-氧化锰类复合夹杂。(2)镁合金化可有效细化低碳钢中夹杂物,并使之分布更加弥散。钢中镁含量增加,夹杂物尺寸减小,单位体积夹杂物数量增多,分布更加均匀;钢中镁含量为0.0064%时,夹杂物平均尺寸在1.12μm左右,单位体积夹杂物粒子数量达到了16.18×105个·mm-3,在钢液中分布更加弥散。(3)镁合金化可有效细化低碳钢的凝固组织,随着钢中镁含量的增加,其组织更为细密,镁合金化低碳钢产生的镁铝复合夹杂物,可诱导IAF形核,钢中镁含量增加,IAF所占体积增大。钢中镁含量达到0.0064%时,由于固溶镁对组织的影响超过了夹杂物对组织的影响,显微组织表现为大量的GB组织,未发现有IAF组织。(4)Al-O-Mg系复合夹杂物诱导IAF形核的机制符合最小错配度机制。在(100)Mg O·Al2O3|(100)αFe方向上镁铝尖晶石类复合夹杂物与α相之间具有较低的错配度(错配度值为1.0%),可以作为IAF的有效核心诱导其形核。(5)镁合金化可以显著提高低碳钢的强度和塑性。相比镁含量为0%、0.0016%、0.0021%和0.0064%的低碳钢,镁含量为0.0033%的低碳钢屈服强度、抗拉强度最高,其中抗拉强度为576.26 Mpa,屈服强度为437.17 Mpa。(6)五组镁含量下,镁含量为0.0064%的低碳钢塑性最好。经定性和定量分析拉伸断口形貌,判断不同镁含量下低碳钢的拉伸断口均为韧性断裂。随着镁含量降低,拉伸断口处韧窝平均直径降低,韧窝平均密度增多,镁含量为0.0064%的低碳钢中,断口处韧窝平均直径约3.38μm,韧窝平均密度0.315个/μm2。
[Abstract]:In this paper, the effects of different magnesium contents on inclusions (morphology, category, composition, size and distribution, microstructure and mechanical properties) of low carbon steel were studied. The mechanism of IAF nucleation induced by inclusions in low carbon steel is analyzed. The results show that the inclusion in low carbon steel can be modified by the addition of 1: 1) magnesium alloy. The aluminum oxide inclusions and manganese sulphide inclusions in low carbon steels are modified into circles after magnesium alloy melting. Spinel compound inclusions (mainly magnesia, alumina, silica, manganese sulphide); when magnesium content is 0.0064, The inclusion is MgO-SiO2 / MNO _ 2) magnesium alloy can refine the inclusions in low carbon steel effectively, and make them distribute more widely. The content of magnesium in the steel increases, the size of inclusions decreases, and the amount of inclusions per unit volume increases. When the content of magnesium in steel is 0.0064, the average size of inclusions is about 1.12 渭 m, and the number of inclusion particles per unit volume reaches 16.18 脳 105 路m ~ (-3). With the increase of magnesium content in steel, the microstructure becomes finer. The magnesia-aluminum compound inclusion produced by magnesium alloy low carbon steel can induce the nucleation of IAF, and the increase of magnesium content in steel increases the volume of IAF, and when the content of magnesium in the steel reaches 0.0064, As the effect of solid magnesium on the microstructure is greater than that of inclusions on the microstructure, the microstructure is characterized by a large amount of GB structure. It was not found that the mechanism of nucleation of IAF induced by the compound inclusions of IAF microstructures. Al-O-Mg system coincides with the minimum mismatch mechanism. In the direction of 伪 Fe, there is a lower mismatch between magnesia-alumina spinel compound inclusions and 伪 phase (the mismatch value is 1.0g), and the mismatch can be obtained. The strength and ductility of low carbon steel can be significantly improved by inducing nucleation of IAF with effective core. Compared with 0% mg content, 0.0016% mg content and 0.0064%% low carbon steel, mg content can increase the strength and plasticity of low carbon steel. The yield strength of low carbon steel with magnesium content of 0.0033% is the highest, and the tensile strength is 576.26 Mpa. and the yield strength is 437.17 Mpa.Ni6). The plasticity of low carbon steel with magnesium content of 0.0064% is the best, and the tensile fracture morphology is analyzed qualitatively and quantitatively. The tensile fracture of low carbon steel with different magnesium content is ductile fracture. With the decrease of magnesium content, the average dimple diameter and average density of dimple at the tensile fracture surface decrease, and the average density of dimple increases in low carbon steel with magnesium content of 0.0064%. The average diameters of dimples are about 3.38 渭 m and the average density of dimples is 0.315 / 渭 m ~ 2.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

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