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通过热模拟试验对20MnSi连续冷却过程中的相变规律进行了测定,通过电石、硅钙线脱氧及热处理得到了含有晶内针状铁素体试样,利用显微硬度仪对针状铁素体聚集区进行了显微硬度的测定,利用光学显微镜对晶内针状铁素体进行了形貌观察,利用扫描电镜和能谱仪对诱导针状铁素体生成的夹杂物的性质进行了分析。结果表明,20MnSi中可以形成晶内针状铁素体的冷却速度范围为5~20℃/s;能够诱发针状铁素体组织形核的夹杂物主要为Mn S夹杂,其次为MnO·SiO_2和MnS·SiO_2夹杂,并且3类夹杂物的尺寸主要在小于3μm的区间内;MnS夹杂促进针状铁素体形核是由应力-应变能和惰性界面能等原因共同造成的;高温加热和等温保温有利于使贫锰区减弱或消失,不利于针状铁素体的形成;高熔点夹杂物有利于诱导针状铁素体的形核,复合夹杂物和镶嵌存在的夹杂物可以为针状铁素体的形核提供多个合适的形核区,有利于促进多个针状铁素体的同时形核、长大。
The phase transition law of 20MnSi during continuous cooling was determined by thermal simulation. The intragranular acicular ferrite samples were obtained by the deoxidation and heat treatment of calcium carbide and calcium silicate wire. The microstructure of acicular ferrite Body agglomeration area were measured for microhardness, the use of optical microscopy intragranular acicular ferrite morphological observation, the use of scanning electron microscopy and energy spectroscopy to induce acicular ferrite generated inclusions properties analysis. The results show that the cooling rate of intragranular acicular ferrite in 20MnSi ranges from 5 ℃ to 20 ℃ / s. The inclusions that induce acicular ferrite microstructure are mainly MnS inclusions, followed by MnO · SiO_2 And MnS · SiO 2 inclusions, and the sizes of the three types of inclusions are mainly in the range of less than 3 μm; the inclusions of MnS promote acicular ferrite nucleation caused by the stress-strain energy and the inert interface energy; high temperature heating and isothermal Insulation is conducive to reducing or disappearing manganese depleted area, is not conducive to the formation of acicular ferrite; high melting point inclusions conducive to inducing acicular ferrite nucleation, inclusions and inclusions inlaid composite inclusions may be acicular Ferrite nucleation provides a number of suitable nucleation sites that facilitate the simultaneous nucleation and growth of multiple acicular ferrites.