X70级抗大变形管线钢的组织与性能

通过成分设计、相变规律研究、工业规模试制,分别获得了(PF+B)双相组织及AF组织的管线钢钢板。二者的试验研究结果表明,当弛豫终止温度低于相变开始温度后,组织中将出现多边形铁素体(PF)。弛豫终止后以20℃/s左右的冷速加速冷却时,未转变的奥氏体转变为由粒状铁素体(GF)及贝氏体铁素体(BF)组成的贝氏体B组织。相比于AF组织管线钢,(PF+B)组织管线钢具有较低的屈强比及较高的伸长率。试验获得的(PF+B)组织管线钢的轧板厚度达30.8mm,强度级别达到X70级,拥有较低的屈强比和较高的伸长率,满足海底管线对抗变形性能的要求。     

Microstructure and Mechanical Properties of Nb-Microalloyed X100 High Deformability Pipeline Steel

A low carbon Nb-microalloyed high deformability pipeline steel with X100 grade has been processed by TMCP and followed two-stage cooling process.The microstructure is characterized by ferrite/bainite multiphase.The effective grain size is 1.85μm in average.The volume of ferrite is about 10-15% and the grains sizes are mostly less than 5μm.The bainite consists of granular-bainite and lath-bainite,with M/A islands finely dispersed.The longitudinal tensile yield strength,uniform elongation,yield ratio are 647MPa,7.6% and 0.78,respectively.Ferrite/bainite multiphase have large strain hardenability that resulting high strength and high deformability combination.Precipitation of Nb also improves the strength and uniform deformability by precipitation strengthening and grain refinement.     

铬对抗大变形管线钢组织和性能的影响

研究了铬元素对X80抗大变形管线钢的微观结构和力学性能的影响。采用准静态拉伸试验,对其屈服强度、抗拉强度和伸长率进行测试;采用热膨胀法,在Gleeble-1500热模拟机上测定了两种试验钢的动态CCT曲线。结果表明:铬元素的添加降低了碳的活度,显著抑制了先共析铁素体的形成,提高了贝氏体转变温度,使钢的抗拉强度提高约40 MPa,屈服强度基本不变,但使伸长率由19%降低到15%,-20℃冲击功由92 J降低到52 J。     

Effect of Cooling Start Temperature on Microstructure and Mechanical Properties of X80 High Deformability Pipeline Steel

 The effect of cooling (laminar cooling) start temperature on the phase constitution was analyzed by quantitative metallography. The martensite/austenite (M/A) island distribution was fixed by colour metallography. The strength and uniform elongation of the steels were tested with quasi-static tensile testing machine. The in-coordinate deformation of the soft and hard phases was analyzed using FEM. The results indicate that when the cooling start temperature is 690 ℃, the mechanical properties are the best, meeting the requirements of X80 high deformability pipeline steel.     

X65 M管线钢抗HIC性能分析与生产实践

针对在H2S含量偏高特殊环境下使用的X65M管线钢产品抗氢致裂纹(HIC)进行了分析与研究。通过对化学成分、元素偏析、非金属夹杂物对抗氢致裂纹影响的机理分析,指导冶炼过程硫、磷、氢及氧化夹杂物等关键工艺控制,并通过连铸过程严格的保护浇铸措施,实现了钢水w[S]0.002%,w[P]0.010%,w[H]2.0×10-6,钢中各类夹杂物小于1.0的控制水平。X65M管线钢抗氢致裂纹检测符合产品开发标准要求。     

Ferrite Evolution During Isothermal Process in a High Deformability Pipeline Steel

 In order to ensure the safety of long-distance oil and natural gas transmission pipeline installed in seismic and/or permafrost region, high strength pipeline steel with excellent deformability has been developed. The ferrite and bainite dual phase pipeline steel is a very important kind of high deformability pipeline steel. Polygonal ferrite is a key microstructure in ferrite and bainite dual phase deformability pipeline steel. Ferrite evolution during isothermal process at 700 ℃ after 50% deformation at 800 ℃ was conducted by using a Gleeble-3800 thermal simulator, and microstructure was characterized by using an optical microscope, a scanning electron microscope and a transmission electron microscope. There are two types of ferrite, ferrite with high density dislocation and ferrite with a little dislocation. There is about 7% (volume percent) deformation induced ferrite (DIF) for compression of 50% at 800 ℃ and strain rate of 1 s-1. During the isothermal process at 700 ℃, with the holding time increasing, ferrite volume percent, ferrite grain number and average ferrite grain size increase. As the holding time is prolonged, dislocation recovery occurs in DIF. There are secondary phases in ferrite when the holding time is too long, and secondary phases and dislocation formation in dislocation pinning.     

Stress Oriented Hydrogen Induced Cracking of Linepipe Steel

The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.     

高强度钢42CrMoVNb的氢致延迟断裂行为

采用阴极充氢、SSRT缺口拉伸和氢热分析等试验方法,研究了高强度钢42CrMoVNb在不同温度回火状态下的延迟断裂行为,并与常用的机械制造用钢42CrMo进行了对比。结果表明,随着回火温度的升高,试验钢的耐延迟断裂抗力逐渐提高;在相同回火温度下,由于42CrMoVNb钢的强度水平明显高于42CrMo钢,其耐延迟断裂抗力...     

抗大变形管线钢的研究进展

总结了国内外抗大变形管线钢的研究进展,介绍了抗大变形管线钢的基本组织特征,详述了通过成分设计以及相变规律研究,制定出优化的控轧控冷工艺,在国内工业化试制出X65级(多边形铁素体+贝氏体铁素体)抗大变形管线钢.     

F-B型大变形管线钢的研究进展及发展方向

近年来,国内外在新型埋地管线材料F-B型大变形管线钢的成分设计、钢板生产以及制管工艺等方面有许多研究。在成分上注重Mo、Cr、Nb等元素含量与组合搭配设计,在钢板加速冷却上采取适当的开始冷却温度,在制管工艺上选择合适的焊接热输入、合理调整钢管扩径值、进行后续防腐处理,管线管的性能得到明显改善。继续优化材料自身的大变形性能,改进管道设计与施工技术,完善相关标准,是未来大变形管线钢应用研究的主要发展方向。     

The Effect of Phosphorus Content on the Hydrogen Stress Cracking of High Strength 4130 Steel

A series of four 4130 base steels with various phosphorus concentrations was subjected to cathodic charging to determine the effect of P on hydrogen stress cracking resistance. Static fatigue curves for several different yield strengths were obtained for each alloy. At high yield strengths under applied loads of 60 to 80 pct of the yield, 50 ppm P (bulk concentration) was enough to provide sufficient grain boundary P for an impurity-hydrogen interaction which produced intergranular fracture along prior austenite grain boundaries. Decreasing yield strength and applied stress caused a transition in fracture mode to transgranular while the resistance to hydrogen stress cracking increased with decreasing P. Microhardness measurements of prior austenite grain boundaries were made to establish the role of P. The role of P is not apparently related to its capacity as a strengthening element but more probably as a hydrogen recombination poison. Grain boundary hardness measurements for low temperature tempers (200 °C) appear to be valid while those at 500 °C were not.     

应变速率对管线钢在碱性溶液中应力腐蚀行为的影响

主要研究了不同应变速率对X70管线钢在库尔勒土壤模拟溶液中应力腐蚀行为的影响.采用慢应变速率拉伸实验(SSRT)研究了不同应变速率下X70管线钢在模拟溶液中应力腐蚀开裂行为,并利用扫描电镜分析了不同应变速率下的断面形貌.结果表明,应变速率(特别是局部应变速率)对X70管线钢在库尔勒土壤模拟溶液中应力腐蚀行为有重要影响,应变速率在5×10-7～5×10-6s-1之间有较强的应力腐蚀开裂敏感性,在裂纹扩展不同阶段氢和阳极溶解交互作用相对贡献大小不同.     

Steel Microstructure Effect on Mechanical Properties and Corrosion Behavior of High Strength Low Carbon Steel

Different thermomechanical treatments were applied to a high strength low carbon steel with a novel chemical composition. As a result, three different microstructures were produced with dissimilar mechanical and corrosion properties. Subsequently, a tempering heat treatment was applied to redistribute the phases in the steel. Microstructure A with 56 pct martensite and 32 pct bainite presented high strength but medium ductility; microstructure C with 95 pct ferrite and 3 pct martensite/austenite resulted in low strength and high ductility, and finally microstructure B with 98 pct bainite and 2 pct martensite/austenite resulted in high strength and ductility. Alternatively the corrosion behavior obtained by polarization curves was characterized in 0.1 M H₂SO₄, 3 M H₂SO₄, 3.5 wt pct NaCl, and NS4 solutions resulting in similar magnitudes, while the corrosion behavior acquired by electrochemical impedance spectroscopy had slightly differences in 3 M H₂SO₄.     

高强度管线钢的微观组织与冲击韧性

研究了具有不同微观组织类型的高强度管线钢的夏比冲击韧性.结果表明,针状铁素体型管线钢比多边形铁素体 少量珠光体型管线钢具有更高的冲击韧性.对于针状铁素体型管线钢,可通过减少夹杂物,获得均匀细小的铁素体晶粒、细小弥散的M/A岛和析出物,来获得优异的冲击韧性.     

管线钢拉伸试验过程中显微组织对其屈服行为的影响

研究了X60管线钢的显微组织对其拉伸过程中屈服行为的影响.铁素体 珠光体组织和非多变形铁素体组织分别会产生屈服现象和无屈服现象,这与其晶粒尺寸的大小和晶粒内位错密度的高低有关.     

Effect of Finish Rolling Temperature on Microstructure and Mechanical Properties of High Grade Pipeline Steel

The correlation among finish rolling temperature (FRT),microstructure and mechanical property of the high grade pipeline steel was investigated in this study.The microstructure of the steels with different finish rolling temperatures was observed with scanning electronic microscope (SEM) and transmission electronic microscope (TEM).The martensite/austenite (M/A) islands distribution was fixed by colour metallography,and the mechanical properties of the steels were tested with quasi-static tensile testing machine.The result shows that the fraction of M/A island increased with the finish rolling temperature decreasing,and when the finish rolling temperature is 800℃,the mechanical properties are the best.     

Effect of Microstructure in TRIP Steel on Its Tensile Behavior at High Strain Rate

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Effect of Low-Temperature Environment on Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Simulated Alkaline Soil Solution

Metallurgical and Materials Transactions A - The stress corrosion cracking (SCC) of X80 pipeline steel in simulated alkaline soil solution under different temperatures was investigated by...     

X100管线钢的组织、性能及再结晶规律

分析了X100管线钢动态再结晶规律,并绘制了X100管线钢的奥氏体动态再结晶图。在实验室进行了X100管线钢的试制,结果表明:在实验室试制的X100管线钢,屈服强度达到了800MPa,抗拉强度达到了925MPa,并且冲击性能优良,各项性能指标均超过了API标准要求。用SEM对X100管线钢的金相组织进行观察,发现其典型组织为粒状贝氏体,并有少量的贝氏体铁素体。用TEM对其M-A岛形貌进行观察,发现M-A岛宽度约为300nm。