高牌号无取向硅钢全尺寸夹杂物表征

Characterization of Full-size Inclusions in High Grade Non-oriented Silicon Steel

采用大样电解、扫描电镜(SEM)、透射电镜(TEM)检测分析3.0%Si−0.85%Al−0.27%Mn高牌号无取向硅钢铸坯和成品板中全尺寸夹杂物的形貌、数量,并基于夹杂物种类分析主要夹杂物的来源。结果表明:铸坯中大型夹杂物的含量为2.18 mg/10 kg,引起无取向硅钢成品板表面线状缺陷的大型夹杂物来源于保护渣、顶渣及耐材的复合夹杂物;成品板中尺寸为0.50~5.00μm的显微夹杂物主要为Al_(2)O_(3),mCaO•nAl_(2)O_(3),mAl_(2)O_(3)•nSiO_(2),mMgO•nAl_(2)O_(3),AlN和硫化物等夹杂物,形貌分布多样化;0.10~1.00μm微细夹杂物的平均尺寸为0.30μm,分布密度为4.95×10^(4)个/mm^(2),尺寸主要分布在0.10~0.30μm范围;小于500 nm的析出相主要为球形或近球形的MnS和Cu_(2)S、矩形的AlN和TiN及部分形貌较为复杂的细小氧化物,尺寸主要分布在50~200 nm范围;50~100 nm析出相的分布密度为5.23×10^(5)个/mm^(2)。钢液温降和二次氧化过程生成的细小氧化物、后序热处理中析出的Cu_(2)S和均热过程未析出的AlN,TiN,MnS均以微细夹杂物析出,钉扎晶界,严重影响晶粒的生长,恶化无取向硅钢磁性能。

The morphology and quantity of full-size inclusions in 3.0%Si−0.85%Al−0.27%Mn high grade nonoriented silicon steel billet and finished plate were detected and analyzed with bulk electrolysis,scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The sources of main inclusions were analyzed based on the types of inclusions.The results show that the content of large inclusions in the casting billet is 2.18 mg/10 kg,and the large inclusions causing linear defects on the surface of non-oriented silicon steel finished plates come from composite inclusions of protective slag,top slag and refractory materials.The micro inclusions of 0.50–5.00μm in the finished plate mainly include composite inclusions such as Al_(2)O_(3),mCaO•nAl_(2)O_(3),mAl_(2)O_(3)•nSiO_(2),mMgO•nAl_(2)O_(3),AlN,and sulfides,with diverse morphology distribution.The average size of fine inclusions of 0.1–1.0μm is 0.295μm,with a distribution density of 4.95×10^(4) particles/mm^(2),and with size mainly distributed in the range of 0.10–0.30μm.The precipitates smaller than 500 nm are mainly spherical or nearly spherical MnS and Cu_(2)S,rectangular AlN and TiN,and some small oxides with complex morphologies,with size mainly distributed at 50–200 nm.The density of precipitates with size of 50-100 nm is 5.23×10^(5) particles/mm^(2).The fine oxides generated during the temperature drop and secondary oxidation processes of molten steel,Cu_(2)S precipitated during subsequent heat treatment,and AlN,TiN,and MnS not precipitated during the homogenization process all precipitate as fine inclusions,which will pin grain boundaries and seriously affect grain growth,thereby deteriorating the magnetic properties of non-oriented silicon steel.