3%取向硅钢中MnS沉淀析出动力学的计算

利用第二相相关理论计算分析薄板坯连铸连轧3%取向硅钢中MnS沉淀析出的动力学行为。沉淀析出计算结果显示在薄板坯连铸连轧生产工艺中以铁素体位错线上形核为主导,MnS在铁素体中的析出量最大,其有效沉淀温度范围约为700~900℃,临界形核尺寸约为0.7~1.5 nm;相变完成时MnS颗粒的半径约为30 nm,可以起到抑制剂的作用。终轧温度应在800℃以上。     

酸溶铝含量对取向硅钢常化抑制剂析出的影响

以工业0.27 mm规格高磁感取向硅钢为研究对象,研究了酸溶铝(Als)含量对常化板析出物析出行为的影响.结果表明:常化板中的析岀物主要是AlN与MnS和AlN的复合析出物,随着Als含量的升高,析出物数量增加,但析出物平均尺寸变化不大.常化板中粗大的析出物大多是复合析出物,且多是以MnS为核心,AlN在MnS表面析出,而常化板中细小的析出物多为单一的析出物.常化冷却阶段,由于过饱和的Al和N在珠光体区域附近更多地析出,常化板珠光体区域附近存在较多细小的AlN粒子.     

TSCR工艺生产SPHC板过程硼微合金化对AlN、MnS析出的影响

 结合TSCR工艺生产SPHC钢热轧板过程,对微量B影响AlN、MnS的析出行为进行了试验研究与热力学分析,理论分析与热轧板在线取样的相分析结果能很好地吻合。结果表明高温时B优先于Al与N结合生成粗大的BN粒子(约900 nm),有效降低了热轧过程细小而弥散的AlN析出量,同时BN依附MnS析出而粗化MnS粒子,减弱了细小弥散析出粒子对奥氏体晶界钉扎以及相变后铁素体晶粒长大的抑制作用。     

无铝成分低牌号无取向硅钢析出物研究

采用配备了X射线能谱分析仪的Tecnai F20场发射透射电子显微镜对CSP流程生产的低牌号无Al成分体系硅钢析出物类型、形貌和尺寸进行了对比分析。结果表明：无铝成分（Al的质量分数小于0.01 %）体系的50W1300和50W800的析出物主要为CuXS/MnS,但有铝成分体系中,除含有CuXS/MnS外,还含有大量Ti(CN)、AlN析出物;且采用无铝成分体系的50W1300和50W800中析出物平均尺寸仅为51 nm和90 nm,比有铝成分体系的69 nm和182 nm明显细小。     

Morphology and Precipitation Kinetics of MnS in Low-Carbon Steel During Thin Slab Continuous Casting Process

The morphology of manganese sulfide formed during thin slab continuous casting process in low-carbon steel produced by compact strip production （CSP） technique was investigated. Using transmission electron microscopy analysis, it was seen that a majority of manganese sulfides precipitated at austenite grain boundaries, the morphologies of which were spherical or close to the spherical shape and the size of MnS precipitates ranged from 30 nm to 100 nm. A mathematical model of the manganese sulfide precipitation in this process was developed based on classical nucleation theory. Under the given conditions, the starting and finishing precipitation temperatures of MnS in the continuous casting thin slab of the studied low-carbon steel are 1 189 ℃ and 1 171 ℃, respectively, and the average diameter of MnS precipitates is about 48 nm within this precipitation temperature range. The influences of chemical components and thermo-mechanical processing conditions on the precipitation behavior of MnS in the same process were also discussed.     

SCM420连铸坯热送过程MnS-AlN复合相的析出行为

为了研究SCM420连铸大方坯不同热送条件下铸坯表层MnS-AlN复合相的析出特征及形成机理,利用冷场发射电镜对MnS AlN的三维形貌与分布特征进行了观察,对钢中AlN析出热力学、不同形核机制下的析出动力学特征进行了理论计算,分析了不同形貌MnS-AlN基底MnS的当量直径D与AlN相对析出量指标A的关系,最后得出了...     

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The precipitation behavior of MnS and AlN in low-temperature high magnetic induction grain-oriented silicon steel produced by thin slab casting and rolling process with ??acquired inhibitor method?? during continuous casting and soaking was studied by thermodynamic calculation. The calculated results show that AlN is likely to precipitate in ferrite after solidification. However, MnS can precipitate only in the two phase region of ferrite and austenite. Meanwhile, MnS and AlN in the steel can not be completely dissolved during the soaking stage. In addition, the abnormal growth of primary grain is not obvious after high-temperature nitriding, which indicates the number of inherent inhibitor in the steel is relatively sufficient before nitriding.     

Modelling of Manganese Sulphide Formation during Solidification,Part I: Description of MnS Formation Parameters

Precipitations of second phases in steel grades influence the mechanical properties of the material significantly. Manganese sulphides especially affect the ductility properties at high as well as at low testing temperatures. For a sufficient appreciation of the influence of MnS precipitates on the properties, a proper knowledge about the parameters in regard to the size and distribution of MnS precipitates is necessary. This paper proposes a model to describe the solidification of a medium carbon steel grade, the micro‐segregation of manganese und sulphur and the subsequent precipitation of MnS. Especially for the calculation of the mean radius of globular MnS precipitates after solidification, a new approach is presented regarding the MnS size as a function of the manganese and sulphur content, the cooling rate during solidification and the secondary dendrite arm spacing. The model is validated by means of quench tests in combination with light‐optical and scanning electron microscopic evaluations of the size distribution of MnS precipitates as well as EDX analysis for the composition of the formed sulphide phase.     

TEM Investigations of Fine Niobium Precipitates in HSLA Steel

Commercially produced 0.03 % C, 0.08 % Nb, 0.01 % Ti high strength low alloyed (HSLA) steel in the form of 20 mm thick plates was investigated. The steel was thermomechanically processed and the mechanical properties of the steel were evaluated by tensile testing. Using analytical and high resolution transmission electron microscopy the distribution, morphology, composition, crystal structure and particle size of niobium and titanium carbonitrides were observed and identified in these steels. The distribution of the precipitates was found to be nearly random, with occasional occurrence of precipitation free zones. Complex agglomerates with a cubic TiN seed crystal overgrown by a cubic NbC particle were the most commonly observed precipitates. Further TEM analysis in the accelerated cooled and tempered specimens in 1/4 plate thickness did not reveal any evidence that additional precipitation in the ferrite occurred. Precipitation in ferrite was only detected after subsequent cold deformation and tempering of the same samples. By a combination of EFTEM, STEM, HRTEM in addition to EDX spectroscopy, a large population of strain induced NbC precipitates with fcc crystal structure ranging in size down to 2 nm were identified in the ferrite matrix.     

High temperature SANS experiments on Nb(C,N) and MnS precipitates in HSLA steel

The volume distribution of precipitates in high-strength low-alloy (HSLA) steels has been studied using small-angle neutron scattering (SANS) at high temperatures. Three samples with different niobium concentrations (0.00, 0.05, and 0.10 wt pct) were slowly heated from a temperature of 910 °C to 1200 °C. With increasing temperatures, the scattered intensity strongly decreases as the precipitates gradually dissolve or coarsen. A comparison between the particle distribution of the three different materials suggests that the particles with a radius below 10 nm mainly correspond to Nb(C,N) precipitates and the larger particles to MnS precipitates. Subsequent cooling from 1200 °C to 910 °C only leads to a small increase in the scattered intensity. Quenching from the austenite to the ferrite phase and reheating to the austenite phase, however, produces a large increase in the formation of the small precipitates with a radius below 10 nm.     

Fe-5Mn-2Al-0.15C中锰钢连铸凝固偏析及粒子析出行为

为研究Fe-Mn-Al-C系中锰钢连铸凝固偏析及粒子析出特性,采用光学显微镜观察Fe-5Mn-2Al-0.15C中锰钢的显微组织,并通过Thermo-Calc热力学软件研究了其凝固模式、溶质元素偏析及粒子析出行为。结果表明,该中锰钢铸锭的显微组织主要为板条状马氏体,且含有少量铁素体;其凝固模式为L→L+δ→L+δ+γ→δ+γ→γ;Al元素的平衡分配系数大于1,发生负偏析,偏聚到δ-铁素体枝晶内部;而Mn、Nb、V、S等溶质元素发生正偏析,均偏聚到枝晶间。AlN主要在枝晶内析出,其析出温度为1 448 ℃;MnS、Nb和V的富集物主要在枝晶间析出,且MnS和Nb的富集物均在1 400 ℃以上开始析出,而V的富集物的析出温度为760 ℃。     

Analysis of Microstructure Characteristics and Precipitation Behavior＇of Automobile Beam Steels Produced by Compact Strip Production

The microstructure characteristics and precipitation behavior of automobile beam steels produced by compact strip production (CSP) were investigated by use of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. The result shows that the final microstructure is mainly composed of polygonal ferrite and small amount of pearlite, and the average ferrite grain size is about 3—6 μm. Small amount addition Ti to aluminium-killed steel can help to refine the microstructure and improve the mechanical properties. A large number of fine precipitates have been observed in automobile beam steels. The mean particle size is about 10—30 nm. Remarkable strengthening and grain refinement can be obtained by these nano-particles.     

Analysis on Microstructure Characteristics and Precipitation Behavior of Automobile Beam Steels Produced by Compact Strip Production

 The microstructure characteristics and precipitation behavior of automobile beam steels produced by Compact Strip Production (CSP) were investigated by use of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. The result shows that the final microstructure is mainly of polygonal ferrite and small amount of pearlite, the average ferrite grain size is about 3～6μm. Small amount addition Ti to aluminium-killed steel can help to refine the microstructure and improve the mechanical properties. A large number of fine precipitates have been observed in automobile beam steels. The mean particle size is about 10～30nm. Remarkable strengthening and grain refinement can be obtained by these nano-particles.     

Analysis of Microstructure Characteristics and Precipitation Behavior of Automobile Beam Steels Produced by Compact Strip Production

The microstructure characteristics and precipitation behavior of automobile beam steels produced by compact strip production (CSP) were investigated by use of scanning electron microscopy (SEM),transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. The result shows that the final microstructure is mainly composed of polygonal ferrite and small amount of pearlite,and the average ferrite grain size is about 3-6μm. Small amount addition Ti to aluminium-killed steel can help to refine the microstructure and improve the mechanical properties. A large number of fine precipitates have been observed in automobile beam steels. The mean particle size is about 10-30nm. Remarkable strengthening and grain refinement can be obtained by these nano-particles.     

Effect of sulphur content on precipitates and properties of DH36 structural steel

In the current research, the influences of sulphur content on precipitates and properties were investigated through thermodynamic calculation and microstructural analysis. The results show that the precipitates of DH36 structural steel are mainly (Nb, Ti)C and Ti(C,N), the size of which ranged from 7 to 220?nm. Plenty of nanoscale MnS was observed by transmission electron microscopy using carbon film replicas with 0.002% S. This is because the temperatures of maximum nucleation rate and fastest precipitation of MnS are much less than soaking temperature when S content is 0.002%, which is the main reason for the formation of nanoscale MnS. What is more, the pinning effect of nanoscale MnS can also refine the grain size. Consequently, ultra-low content of sulphur can be used to optimise the properties of DH36 structural steel.     

CSP-低碳钢DC03冷轧板的组织和织构

研究了CSP工艺生产的0.04%C低碳钢DC03 2.9 mm热轧基板、0.9 mm的冷轧板和退火平整板的组织与织构。结果表明,热轧基板组织为铁素体+少量沿晶界分布的珠光体,铁素体基体中有少量40～100 nm MnS粒子,没有观察到AlN;冷轧板组织为含大量位错的带状铁索体-珠光体,{111}织构的择优取向较明显;退火平整板组织为铁素体和游离渗碳体,并观察到10～30 nm的析出相,{111}织构轴密度达5.15,{100}轴密度减为0.61。     

低温加热生产取向硅钢中MnS和Cu_2S的竞相析出

针对薄板坯连铸连轧流程(TSCR)生产具有低温加热(1200℃)抑制剂成分取向硅钢,研究了薄板坯连铸、均热以及热连轧过程中MnS和Cu2S的析出特征,研究结果表明,连铸过程形成的MnS在1180℃下难以完全固溶,并形成尺寸为200~600 nm的粗大MnS粒子,而在此温度下Cu2S可以完全固溶并在热连轧过程中细小弥散析出,平均粒子尺寸约为30 nm,可以作为取向硅钢的有效抑制剂。     

CSP生产无取向电工钢的组织和性能

 研究了采用CSP流程生产的无取向电工钢的金相组织、第二相粒子分布、磁性能。结果表明,采用CSP流程生产的无取向电工钢热轧板成品均为均匀粗大的等轴晶;热轧板中第二相粒子平均尺寸在150 nm左右,且随(Si+Al)含量的增加,第二相粒子的类型发生明显的变化;CSP流程生产的无取向电工钢磁性能得到明显的提高。     

Fe-23Mn-xAl-0.7C低密度钢中非金属夹杂物形成机理

 为了研究Fe-23Mn-xAl-0.7C(x=0.87～6.76)低密度钢中非金属夹杂物形貌特征及形成机理,通过SEM-EDS检测了钢中夹杂物形貌和成分,并借助INCA Feature夹杂物自动分析软件分析了钢中夹杂物尺寸分布、数量密度和面积分数等参数。研究发现,低密度钢中夹杂物尺寸以1～5 μm为主。w([Al])为0.87%时,钢中主要夹杂物为MnS、MnO、Al₂O₃和Al₂O₃-MnS,夹杂物数量较少,但尺寸大于7 μm的夹杂物所占比例较大,平均尺寸为3.45 μm;w([Al])为3.28%时,主要夹杂物为AlN、Al₂O₃、MnS以及AlN-MnS、AlN-Al₂O₃-MnS复合夹杂物,外包裹MnS尺寸较小,小尺寸夹杂物居多,平均尺寸为2.63 μm;w([Al])为6.76%时,钢中夹杂物以AlN或AlN-MnS为主,且AlN夹杂呈聚集状,夹杂物平均尺寸为2.93 μm。此外,通过FactSage 7.3热力学计算讨论了Fe-23Mn-xAl-0.7C低密度钢中夹杂物析出时机及演变过程,为试验结果提供理论解释。     

AlN在Hi-B钢铁素体相中析出的形核机制

通过理论计算的方法,系统分析了AlN在Hi-B钢铁素体中的析出形核机制。结果表明,第二相AlN粒子不同析出形核机制下的临界形核尺寸随着温度的降低而降低,形核机制不同,临界形核尺寸不相同,但均匀形核和晶界形核的临界形核尺寸较为接近,同一温度条件下,位错形核的临界形核尺寸最小。第二相AlN粒子以位错形核、均匀形核、晶界形核3种形核机制形核的最快析出温度分别为1 273、1 193、1 293K。同时,温度在1 293K以下时,取向硅钢中AlN在铁素体中以位错形核为主,温度高于1 293K后,AlN的形核机制以晶界形核为主。