钛脱氧钢中针状铁素体的形成

通过实验研究了钢中加钛脱氧后针状铁素体的形成及夹杂物的变化。对实验钢的化学成分、组织变化、析出相成分、钢中氧含量及夹杂物尺寸进行了分析。实验证明,在钢中加钛处理后,钢中产生了大量的以钛氧化物或钛铝等复合氧化物为核心的针状铁素体,钢的组织明显细化,随着钛加入后孕育时间的延长,钢中夹杂物的尺寸变小,孕育时间存在最佳值。     

含钇E36船板钢夹杂物改性

为了研究钇对E36船板钢中夹杂物成分和形貌的影响,对钇处理后E36船板钢中典型夹杂物进行热力学计算,并通过扫描电镜及能谱仪对钇处理前后E36船板钢中夹杂物进行检测分析,观察典型夹杂物形态和尺寸。结果表明,未添加稀土钇的E36船板钢主要为长条状MnS夹杂物;添加稀土钇后,钢中夹杂物主要为球状或类球状的含钇复合夹杂物。当钢中钇质量分数为0.007 8%时,夹杂物主要为球状或类球状的Y₂O₂S夹杂物和Y₂O₃夹杂物;当钢中钇质量分数增加至0.037 7%时,夹杂物改性为球状或类球状Y₂O₂S夹杂物、YS夹杂物和Y₂O₃夹杂物。     

稀土处理C-Mn钢显微组织和夹杂物演化

对稀土处理C-Mn钢的夹杂物和显微组织进行分析,统计稀土处理C-Mn钢中针状铁素体形核核心尺寸,并将稀土处理钢在不同温度下淬火,研究稀土夹杂物生成和长大过程.实验结果表明:C-Mn钢加入少量稀土后钢中夹杂物从MnS＋硅铝酸盐夹杂转变为La₂O₂S＋LaAlO₃＋MnS＋硅铝酸盐夹杂,尺寸得到细化,显微组织也从马氏体＋贝氏体组织变成侧板条铁素体、针状铁素体和块状铁素体组织;稀土处理C-Mn钢中针状铁素体有效形核核心的尺寸集中在1~4μm,主要是在钢液中形成,冷却和凝固过程形成的数量较少;稀土夹杂物在钢液温度和冷却及凝固过程容易碰撞黏合长大,上浮从钢液中去除,MnS能在稀土夹杂物颗粒间析出.      

奥氏体化温度对Ti–Zr处理钢中针状铁素体转变的影响

Ti、Zr的复合氧化物可以有效诱导针状铁素体形核,从而细化晶粒。为了研究Ti–Zr处理钢中针状铁素体转变机理,使用25 kg真空感应炉中熔炼试验所需钢种,向低合金钢中添加了质量分数为0.038%钛和0.008%锆。利用高温激光共聚焦显微镜原位观察了奥氏体化温度对针状铁素体转变行为的变化,使用扫描电镜观察了Ti–Zr处理钢种的夹杂物成分和针状铁素体在夹杂物表面形核,使用光学显微镜观察不同奥氏体化温度下的微观组织变化差异。结果表明,随着奥氏体化温度从1250 ℃增加至1400 ℃,奥氏体晶粒尺寸从125.6 μm 增加至279.8 μm,针状铁素体开始转变温度和侧板条铁素体开始转变温度先增加,在1350 ℃条件下达到最大值,后又降低,针状铁素体的体积分数由39.6%增加至83.6%;Ti–Zr处理钢中核心为Zr–Ti–O,外部为Al–Ti–Zr–O的氧化物为核心表面析出MnS的复合氧化物主要集中在1.5～3 μm,可以有效促进针状铁素体形核,贫Mn区和夹杂物与铁素体之间的良好晶格关系为该型夹杂物能够促进针状铁素体形核机理。奥氏体晶粒尺寸的增加导致多边形铁素形核位点的减少和针状铁素体的形核空间的增加,钛锆复合处理形成大量的有效诱发针状铁素体形核的夹杂物,这共同导致了针状铁素体体积分数增加。      

钛、锆脱氧对钢中夹杂物及组织的影响

通过采用锰铁、硅铁合金预脱氧,钛、锆单独或复合终脱氧的脱氧制度,研究了某低碳钢种脱氧后,钢中夹杂物的形貌、成分、尺寸分布情况。结果表明:采用Zr、Ti脱氧可以获得尺寸较小且数量较多的夹杂物粒子,加Ti后试样中的夹杂物主要为TixOy,Al2O3,MnS的复合夹杂;加Zr试样,钢中夹杂物主要为ZrxOy,SiO2,Al2O3,MnS系复合夹杂;复合添加Ti、Zr的试样,其夹杂物主要为ZrxOy,TixOy,SiO2,Al2O3,MnS复合夹杂物。Zr,Ti复合氧化物粒子能促进晶内针状铁素体形成。     

钛稀土复合处理对C--Mn钢粗晶热影响区组织及韧性的影响

利用Gleeble-1500D热模拟机进行焊接热影响区热循环模拟实验,研究了在焊接热输入为65 kJ·cm-1时稀土单独处理和钛稀土复合处理对C-Mn钢粗晶热影响区组织及冲击韧性的影响,并利用扫描电镜观察和分析了实验钢中的夹杂物和冲击断口形貌,利用光镜观察了热循环模拟后实验钢中的微观组织.实验结果表明:稀土单独处理和钛稀土复合处理的试样微观组织分别主要是晶界铁素体+块状铁素体+针状铁素体和晶界铁素体+晶内针状铁素体.经稀土单独处理的试样中夹杂物为La₂O₂S+锰铝硅酸盐+MnS复合夹杂;钛稀土复合处理的试样中的夹杂主要是La₂O₂S+TiO_x+锰铝硅酸盐+MnS复合夹杂.钛稀土复合处理钢中的复合夹杂更细小,有利于形成细小的晶内针状铁素体.钛稀土复合处理极大地改善了实验钢的焊接热影响区低温冲击韧性,比稀土单独处理对试样的冲击性能提升效果更好.      

钛脱氧钢中超细夹杂物内部结构和物相组成研究

在真空感应炉中采用了真空碳脱氧再加钛终脱氧的脱氧工艺冶炼出了与高级别管线钢成分接近的试样钢,对钛脱氧钢中超细夹杂物的外部形貌、尺寸、内部结构和物相组成等进行了研究。在扫描电镜下通过对金相试样和电解提取的夹杂物的研究表明,钢中夹杂物是Ti-O-Mn-S形成的尺寸为1~3μm的球形复合夹杂物。通过离子减薄后观察了夹杂物的内部结构,中心是Ti-O化合物,外围是Mn-S化合物;通过电子背散射衍射(EBSD)对夹杂物物相组成的分析表明,该复合夹杂物是有利于针状铁素体(IGF)形核的Ti2O3和在凝固过程中以Ti2O3为核心形核的MnS。     

钢中不同氧含量对含S钢的MnS夹杂物影响

采用ASPEX自动扫描电镜,分析对比不同氧含量对钢中MnS类夹杂物的组成和形貌的影响。对比结果表明:当钢中氧含量处于高水平时,MnS夹杂物在整个含MnS类夹杂物中所占比例为70.89%,含MnS类夹杂物的尺寸指数为1.98;当钢中氧含量处于低水平时,MnS夹杂物在整个含MnS类夹杂物中所占比例为93.84%,含MnS类夹杂物的尺寸指数为4.5,夹杂物的外观由椭圆型转变为细长型。     

20MnSi中夹杂物对针状铁素体形成的影响

 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MnS夹杂,其次为MnO·SiO2和MnS·SiO2夹杂,并且3类夹杂物的尺寸主要在小于3 μm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。     

3次钛脱氧钢中非金属夹杂物及组织研究

通过热力学计算及3次Fe2O3增氧和钛脱氧的试验,研究了钢中夹杂物的形态、尺寸及分布规律和钢的组织形貌特征。试验结果表明:3次增氧和脱氧工艺条件下,控制钢中氧质量分数大于0.001%时,钢中的氧与钛可反应生成含钛氧化物,热力学分析证明此条件下生成的钛氧化物为Ti2O3。钛脱氧后钢中氧质量分数在0.002%左右,试样中颗粒直径小于2μm的钛氧化物数量显著增加,在2μm和3μm之间的钛氧化物数量基本不变,这些夹杂物可诱发针状铁素体析出,从而细化组织。     

Al-Ti�����Էǵ��ʸ���MnS������Ϊ����֯��Ӱ��

The morphology, composition and sizes of MnS containing inclusions in a non-quenched and tempered steel containing 0. 35% of carbon deoxidized with different contents of aluminium and titanium were investigated. The generation of acicular ferrite in austenite grain for the samples with different carbon content was observed on line with a cooling speed of 2??/s after 10min heating at 1350?? by a confocal laser high temperature scanning microscope. The results show that aluminum content in the steel more than 0. 04% is not beneficial to the formation of fine, disperse and spherical MnS. Adding 0. 02% Ti to steel could form the complex inclusions of MgO-Al2O3-TiOx-SiO2-MnS which is fine, dispersed and spherical when the aluminum content in the steel is low. The complex inclusions of MgO-Al2O3-TiOx-SiO2-MnS are beneficial to the generation of acicular ferrite in the non-quenched and tempered steel. Carbon content effects the generation of acicular ferrite in Ti-deoxidized non-quenched and tempered steel, after C-addition, the ration of acicular ferrite would decrease in Ti-deoxidized steel.     

An Integrated Study on the Evolution of Inclusions in EH36 Shipbuilding Steel with Mg Addition: From Casting to Welding

Inclusion evolution behaviors, in terms of composition, size, and number density, and associated influence on the microstructures of the as-cast slabs, rolled plates, and simulated welded samples of plain EH36 and EH36-Mg shipbuilding steels have been systematically investigated. The results indicate that the inclusions in the as-cast plain EH36 are almost Al-Ca-S-O-(Mn) complex oxides with sizes ranging from 1.0 to 2.0 μm. After Mg addition, a large amount of individually fine MnS precipitates and Mg-containing Ti-Al-Mg-O-(Mn-S) complex inclusions are generated, which significantly refine the microstructure and are conducive to the nucleation of acicular ferrite in the rolled and welded sample. Moreover, after rolling and welding thermal simulation, the number of individual MnS decreases gradually due to its precipitation on the surface of Ti-Al-Mg-O oxides.     

EH40级船体钢中焊接热影响区组织特征

近年来,中国船舶与海洋工程制造业迅猛发展,高强度、高韧性、易焊接性、耐蚀性已成为造船及海洋工程用钢的发展方向.焊接是船体制造的关键环节,采用大线能量焊接来提高造船效率已成为造船企业的首选.但是,焊接线能量的提高导致钢板焊接热影响区晶粒严重粗化、局部软化和脆化,其低温冲击韧性变差,严重威胁船 体钢的安全使用.氧化物冶金是...     

Addition of Dispersoid Titanium Oxide Inclusions in Steel and Their Influence on Grain Refinement

In this article, the addition of dispersoid titanium oxide inclusions into liquid steel, the effect of additions on the inclusions found in the steel and on grain refinement, and acicular ferrite formation were studied. Different TiO₂-containing materials and addition procedures into liquid steel were tested in experimental heats to obtain inclusions that promote grain refinement and acicular ferrite formation in C-Mn-Cr steel. Different additives with metallic Ti and TiO₂ were added into the steel melt just before casting or into the mold during casting to create Ti-containing inclusions. The aluminum content in steel was lowered by an addition of iron oxide. The samples taken from steel melts and ingots were studied with a scanning electron microscope to find inclusions and to analyze them. Thermodynamic calculations showed that the Al content should be low (<50 ppm) to obtain Ti oxide dominating inclusions, whereas Al₂O₃ were formed at higher Al contents. When TiO₂ was added late before casting, the oxide inclusions were Ti oxides and were mixed with Ti, Al, and Mn oxides. Small inclusions around 1 μm were detected in the samples with TiO _x or TiN as the main component. It could be concluded that the additions resulted in a clearly higher number and in a smaller size of TiO _x inclusions than just by adding metallic Ti. Selected samples were brought for subsequent hot rolling and heat-treatment experiments to find out the grain-refining effect and the eventual formation of acicular ferrite. Grain refinement was observed clearly, but the presence of acicular ferrite could not be confirmed definitely.     

Effect of Aluminum and Titanium Treatment on Non-Metallic Inclusions and Microstructures of CGHAZ in HSLA Steel

The Effect of A1 and Ti treatment on non-metallic inclusions and microstructures of coarse-grain HAZ in HSLA stee1 was investigated in this paper based on experiments and thermodynamic calculations.The results showed that the inclusions in A1 treated steel were mainly aluminum oxides and titanium nitrides which could not promote the formation of acicular ferrite microstructures.Microstructure of coarse-grain HAZ in A1 treated steels consists of heavy grain boundary ferrite and ferrite side plate.The inclusions in Ti treated steel were A1,Ti,Mg,Ca composite oxides with size in the range of 0.5-3μm and titanium nitrides with size less than 0.3μm.Ti composite oxide could promote the formation of acicular ferrite and microstructures of coarse-grain HAZ in Ti treated steel consists of grain boundary ferrite,small amounts of ferrite side plate and large amounts of intragranular acicular ferrite.The size of grain boundaries ferrite was increased and the amount of ferrite side plate was decreased with the increase of soaking time at the peak temperature.The amount of grain boundary ferrite and the size of acicular ferrite were also increased with the increase of cooling rate during ferrite phase formation.     

聚焦离子束扫描电镜三维重构夹杂物的形态和分布

以MnS易切削钢和EH36电渣焊焊缝区样品为研究对象,首先利用聚焦离子束扫描电镜的自动系列切片和成像(Auto Slice & View)功能对夹杂物进行逐层切片并成像,然后利用Amira软件根据夹杂物的衬度进行三维重构,从而得到钢铁材料中单一夹杂物及复合夹杂物的形态和分布。其中,复合夹杂物的物相确定还结合了电子探针的元素面分析和电子背散射衍射的物相分析功能。结果表明,MnS易切削钢中的夹杂物呈现条形体、纺锤形体和椭球形体共存的分布状态,而EH36电渣焊焊缝区的复合夹杂物主要由晶态Mn₂TiO₄相和富集Al、Ca、Mg、Si、Mn、O元素的非晶相组成,且两种相伴生存在。夹杂物的三维重构图清晰显示了夹杂物的形态和分布特征,对于研究夹杂物对钢材性能的影响提供了重要依据。     

Quantifying MnS Inclusion Evolution Behaviors During 1473 K Heating in EH36 Shipbuilding Steel with Zr Addition

Metallurgical and Materials Transactions B - The evolution behaviors of MnS inclusions during 1473 K heating have been systematically investigated for EH36 shipbuilding steel with Zr addition. It...