热轧管线钢组织及性能预报研究

作者通过将热轧管线钢生产过程中的冶金学行为和最终得到的组织，性能与各种因素之间的关系化，并编制成程序，对其组织和性能的预报进行了研究，结果表明，预报值与实测值基本吻合。     

X80级管线钢的开发研究

根据X80级管线钢技术要求,对湘潭钢铁（集团）有限公司试制X80级管线钢进行成分设计、相变规律和再结晶规律研究,开发出了φ1016×22．0mmX80级热轧钢板。检验结果表明,各项性能指标均满足技术要求。     

X80高钢级管线钢组织与力学性能

在所选用的4种X80高钢级管线钢中,经过夏比冲击试验、拉伸试验和屈强比计算,发现其力学性能与其组织有很好的对应性.研究结果表明,针状铁素体和细小弥散的贝氏体相结合的组织是X80钢的理想组织形貌,该组织可以使得材料的强度达到最高,而屈强比接近于0.85,从而达到强韧性的很好匹配.该组织的强韧性原理类似于短纤维和颗粒增强复合材料.     

X80管线钢焊接接头组织及性能的研究

通过硬度测试及SEM观察,分析X80管线钢焊接接头处硬度和显微组织变化规律.受焊接热循环的影响,热影响区粗晶区组织主要为粗大的粒状贝氏体和板条贝氏体,硬度较高.靠近热影响区的基体,由于M/A岛分解,硬度值减小.外焊焊缝的显微组织主要是晶内形核铁素体、粒状贝氏体和多边形铁素体.靠近外焊焊缝的内焊焊缝组织受二次热循环的影响较大,组织为粒状贝氏体和块状的铁素体.远离外焊焊缝的内焊焊缝组织受二次热循环影响较小,组织和外焊焊缝组织相差不大.内焊组织中析出物的数量远大于外焊焊缝组织,析出强化效果显著,使内焊的硬度大于外焊的硬度.     

高钢级管线钢TEM显微组织分析

对X70到X100钢级管线钢的透射组织进行了微观分析和研究,并对其组织和力学性能的对应关系进行了研究.结果表明,随着钢级的提高,微观组织中针状铁素体增加,MA岛数量增加,位错密度增加.该结果和管线钢的力学性能变化相对应,和其所对应的TMCP工艺相吻合.     

特厚规格高等级管线钢X70热轧钢板的开发实践

采用低C-Mn-Mo-Nb系为基础,添加适量钒、钛、镍、铜和铬等微合金元素的合金设计方法,利用洁净钢冶炼技术和TMCP轧制工艺,研制开发了X70高等级厚规格钢板。对钢板组织和力学性能分析表明:钢板组织为针状铁素体混合组织,晶粒细小均匀,夹杂少,带状组织轻微,析出物均匀弥散,具有高强度和良好的低温韧性。     

马钢CSP生产线X60管线钢的开发

在马钢首条薄板坯连铸连轧生产线上,开发微合金成分的X60管线钢,利用Gleeble-1500热/力模拟机进行模拟,通过形变、再结晶行为的研究,结合现场采用合适的控轧控冷工艺,生产出满足X60性能要求的管线钢。试制钢组织分布均匀、晶粒尺寸细小、无明显带状组织,具备良好力学性能,强度、塑性和冲击韧性均达到标准要求。     

稀土镁复合处理对X70管线钢组织和性能的影响

采用金相观察、硬度测试、力学性能测试等方法,研究了稀土镁处理对X70管线钢组织与性能的影响.结果表明,微量稀土镁可显著减小晶粒尺寸,提高X70管线钢室温和高温的力学性能;但随温度升高稀土镁对材料的高温力学性能影响会逐步减小.     

X100管线钢的组织与性能

利用金相显微分析、扫描电镜、透射电镜和先进的EBSD技术,对X100钢级管线钢的组织进行了分析,并和CVN等力学性能相对应,进行了相关性探讨.研究表明,X100钢级管线钢全部为粒状贝氏体组织,其透射组织分析表明粒状贝氏体含量很高,主要存在于铁素体边界;铁三碳存在于铁素体板条;组织以针状铁素体为主,也存在少量条状铁素体,同时位错密度很高;EBSD研究表明,铁三碳呈均匀弥散分布,残余奥氏体含量较大;有效晶粒细化现象突出,预示该品牌X100管线钢拥有较理想的强韧性特征.     

X70管线钢焊接接头组织及其海水腐蚀规律

对X70管线钢现场实际焊接工艺下的焊接接头,采用显微镜、电化学方法及失重法等方法和手段对母材、焊缝、热影响区进行了显微组织分析和在海水中的极化曲线、腐蚀速率的测试,研究焊接接头在模拟海水环境中的腐蚀性能.研究表明,X70管线钢焊接接头各区域组织不均匀,实验室模拟海水环境下的电化学行为、腐蚀速率存在明显差异;在海水腐蚀过程中腐蚀电位和腐蚀速率会发生变化,热影响区(HAZ)与母材及焊缝形成电偶腐蚀,接头腐蚀以点蚀为主.     

Precipitation behaviors of X70 acicular ferrite pipeline steel

The morphology, structure, and chemical composition of precipitates in the final microstructure of Nb-V-Ti microalloyed X70 acicular ferrite pipeline steel were investigated using transmission electron microscopy （TEM） and energy dispersive X-ray spectroscopy （EDS）. Precipitates observed by TEM can be classified into two groups. The large precipitates are complex compounds that comprise square-shaped TiN precipitate as core with fine Nb-containing precipitate nucleated on pre-existing TiN precipitate as caps on one or more faces at high temperature. In contrast, the fine and spherical Nb carbides and/or carbonitrides precipitate heterogeneously on dislocations and sub-boundaries at low temperature. From the analysis in terms of thermodynamics, EDS and chemical cornposition of the steel, NbC precipitation is considered to be the predominant precipitation behavior in the tested steel under the processing conditions of this research.     

Microstructure homogenization control of Nb-bearing X65 pipeline steel by the CSP process

In order to get the controlled methods of microstructure homogenization and high strengthening-toughening combination by compact strip production (CSP) rolling,the dynamic recrystallization characteristics of each pass were obtained during CSP rolling using a Gleeble-1500 thermal mechanical simulator.Then,the CSP process was simulated by laboratory rolling experiment.Through thermal mechanical simulation experiment and laboratory rolling experiment,a design idea of Nb-bearing pipeline steel by CSP can be ob...     

Microstructure characteristics and mechanical properties of X80 pipeline steels

The relation between microstructure characteristics and mechanical properties of X80 pipeline steels was investigated using optical microscopy,scanning electron microscopy,etc.It is shown that the structure consists of polygonal ferrite(PF),quasi-polygonal ferrite(QPF),acicular ferrite(AF),and granular bainitic ferrite(GF).With increasing volume fraction of M-A islands(below 3%),the yield strength increases.With increasing content of higher angle grain boundaries(HAGBs),the yield strength,elongation,and DWTT properties at-15 ℃ increase,and the volume fraction of M-A islands reaches its highest point in the steel containing the most volume fraction of GF.     

Study on M／A islands in pipeline steel X70

The free structure of M/A islands in pipeline steel X70 has been studied by transmission electron microscope (TEM). It is shown that the M/A islands are about 1-2 μm in size and distribute at the grain boundary of irregular massive ferrite or acicular ferrite in the microstructure of the steel undergoing TMCP (thermo-mechanical controlled processing). The analysis of diffraction contrast shows that the M/A islands consist of retained austenite and some martensite lamellae different in size and orientation. The microtwinning and midrib exist in the lamella of lenticular martensite, which exhibit the typical character of high-carbon martensite. The influences of TMCP parameters on M/A islands have been studied carefully. With the increase of the cooling speed, the amount of M/A islands decrease slightly and the morphology of M/A islands changes to thin dispersive short bars from thick irregular long strips.     

Ti微合金化450-550MPa级耐候钢组织性能研究

设计了屈服强度达450-550MPa级高强耐候钢化学成分,在实验室进行冶炼和热轧试验,测试和观察了试验钢的力学性能和显微组织,分析了Ti含量对Ti微合金化耐候钢性能的影响。结果表明,试验钢的金相组织主要为在多边形铁素体基体上分布少量的珠光体;Ti微合金化耐候钢具有足够的强度和塑性,随着W（Ti）从0．025％增加到0．07％,试验钢的屈服强度从360MPa增加到550MPa;采用传统控轧控冷工艺可生产出屈服强度达450～550MPa级高强耐候钢。     

激光冲击处理对X70管线钢焊接接头力学性能的影响

利用激光冲击波对X70管线钢焊接接头进行了表面强化处理,分析了激光冲击强化处理后焊接接头组织结构,用显微硬度计测试了焊接接头显微硬度,通过X射线应力仪测定了残余应力沿焊接接头表面的分布规律,并对管线钢焊接接头激光冲击强化的微观机理进行了分析。结果表明:激光冲击波可以在焊接接头表面形成塑性变形层,显微硬度明显提高;材料组织均匀性得到了明显改善;消除了焊接接头表面残余拉应力,形成了残余压应力场。     

低铬X70管线钢组织及其抗CO2

为了明确Cr的质量分数高低对埋地用输油输气管线钢性能的影响,设计了4种Cr的质量分数的X70管线钢,研究了不同Cr的质量分数下管线钢组织及其力学性能,并采用高温高压反应釜进行了实验钢的CO₂腐蚀试验.结果表明：钢中加入0.1%~0.8%的Cr后,其组织均由针状铁素体和准多边形铁素体构成,Cr元素均呈现明显的沿晶界分布状态;随着Cr的质量分数的增加,钢板强度随之升高,晶界中Cr分布密度随之增大,Cr（OH）₃在腐蚀产物膜中的富集量增加,促使钢板的平均腐蚀速率降低;同时由于Cr（OH）₃可以有效阻碍阴离子穿透腐蚀产物膜,因而大大减少了Cl-的催化作用导致的点蚀,使得钢板点蚀速率明显降低.     

Influences of microstructure and texture on crack propagation path of X70 acicular ferrite pipeline steel

The aspects of two pipeline steels with different technologies were investigated by using transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD).The microstructure presents a typical acicular ferrite characteristic with free particles of martensite/austenite (M/A) constituent,which distributes in grains and at grain boundaries.The bulk textures of the pipeline steel plate are {112}<110> and <111> fibers,respectively,and the {112} <110> component is the favorable texture benefiting for drop weight tear test.Moreover,low angle boundaries and low coincidence site lattice boundaries are inactive and more resistant to fracture than high energy random boundaries.