50mm厚高强度低合金钢Q550D的成分优化

 为了解决50mm厚高强度低合金钢Q550D的低温冲击值不稳定的问题,对其合金成分进行了调整试验研究,结果表明,新成分50mm厚Q550D成品钢板强度稳定,伸长率较好,1/4厚度处的-20℃低温纵向冲击值都稳定在239~324J之间,试验批次一次性性能合格率达到100%,成品组织得到了明显改善,吨钢成本也有很大的降低,说明高强度低合金钢中的析出强化元素和固溶强化元素应视钢水冶炼情况及轧制工艺进行适当添加。同时对本钢种低温冲击不稳定争论较大的淬透性问题进行了端淬试验研究,结果表明,原成分钢的淬透性比新成分钢的淬透性要好,说明原成分钢板低温冲击值不稳定并不是钢的淬透性不好,而是成分设计不合理。     

提高低合金高强度钢强韧性的措施

本文通过对提高低合金高强度钢强韧性措施的探讨，结合舞钢的具体生产情况，提出了提高低合金高强度钢强韧性的工艺方法。     

低合金高强度钢的发展与对策

文章分析了我国低合金钢的发展，结合近年来济钢在品种钢开发生产方面的成绩与经验，指出济钢今后应加强配套设施建设，强化质量保证措施，把低合金钢科研成果尽快转化为生产力加快济钢微合金化低合高强度钢的开发。     

硼、碳含量对高硼铁基合金组织和性能的影响

高硼铁基合金是一种新型耐磨材料.硼、碳分别是决定硼化物和基体的重要元素,其含量对组织和性能起决定作用.采用正交实验法研究了硼的质量分数为1.5%～2.5%、碳的质量分数为0.2%～0.5%时高硼铁基合金组织的变化及其对硬度和冲击韧度的影响,为此类材料的研究提供了基础.     

低合金高强度钢开发与研究的新进展

介绍了低合金高强度钢开发与研究的新进展，并对当前国内低合金高强度钢生产存在的总理２进行了分析，同时对低合金高强度钢的市场需求进行了预测。     

控轧控冷工艺对低合金高强钢Q460力学性能的影响

通过改变终轧温度及轧后冷却速度,研究了终轧温度及轧后冷却速度对力学性能的影响。研究结果表明：采用轧后加速冷却的方法,可以显著细化Q460的铁素体晶粒,从而提高其强韧性能。当冷速从2℃/s提高到3.86℃/s时,铁素体晶粒直径从11.5μm细化到8.33μm。当冷速达到2.96℃/s以上时,Rel≥475MPa,Rm≥600MPa,屈强比为70%-80%。     

Influence of Ti on Weld Microstructure and Mechanical Properties in Large Heat Input Welding of High Strength Low Alloy Steels

The influence of Ti on weld microstructure and mechanical properties in large heat input welding of high strength low alloy steels is investigated.The results indicate that a moderate amount of Ti is still effective for grain refinement even under larger heat input and a large amount of acicular ferrite(AF)is formed in the weld metal when Ti content is within 0.028%-0.038%.With increasing Ti content,proeutectoid ferrite in the weld metal decreases,whereas bainite and M-A constituent increase.The type of inclusion in the welds varies from Mn-Si-Al-O to TiMn-Al-O and finally to Ti-Al-O as Ti content increases from 0up to 0.064%.As for adding 0.028%-0.038% Ti,high weld toughness could be attained since most inclusions less than 2μm which contain Ti2O3 provide the effective nuclei for acicular ferrite formation.However,the toughness of the weld metals severely reduces when Ti content is over the optimum range of 0.028%-0.038%.     

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.     

Effects of Processing Variables on Microstructure and Yield Ratio of High Strength Constructional Steels

The process of “controlled rolling+relaxation+ultra fast cooling (UFC)”for high strength constructional steel with low yield ratio was presented.Microstructure and corresponding relationship with low yield ratio were in-vestigated.The results showed that the constructional steels with multiphase microstructure of bainitic ferrite,mar-tensite-austenite (M-A)and lath bainite were obtained through the creative process.The grain size decreased with the decrease in finish rolling temperature,which enhanced the strength by the grain refinement strengthening.The proper relaxation treatment promoted the bainitic ferrite lath width and the formation of blocky M-A constituent.In addition,both the tensile and yield strength increased with the decrease in finish rolling temperature and UFC final temperature,but the yield strength increased more significantly than tensile strength,which caused the increase in yield ratio.By using the process of “controlled rolling+relaxation+ultra fast cooling”,the excellent comprehensive mechanical properties of 780 MPa grade constructional steels of 12-40 mm in thickness were achieved.     

近年来低合金高强度钢的进展

 从洁净钢生产、薄板坯连铸连轧无头轧制、薄带铸轧以及以快速冷却为核心的TMCP工艺等几个方面介绍了HSLA钢生产工艺技术的最新发展,并系统介绍了汽车用钢、船舶及海洋工程用钢、管线钢、建筑结构钢、核电用钢、压力容器用钢、工程机械用钢及集装箱用钢等行业所用的HSLA钢品种开发方面新进展。认为未来HSLA钢将向高强、高性能和低成本方向发展,对HSLA钢的发展有指导作用。     

Isochronal Phase Transformations of Low‐Carbon High Strength Low Alloy Steel upon Continuous Cooling

Aimed to acquire optimum comprehensive properties for the oil and gas pipeline steels, thermal treatment should be controlled to achieve ideal microstructures. Effects of cooling rates on transformation kinetics and microstructures of the low‐carbon high strength low alloy (HSLA) steel were investigated to obtain an optimized thermal treatment technology. Dilatometric measurements, light microscopy, scanning electron microscopy, and transmission electron microscopy were employed in present work. The transformed microstructures contained polygonal ferrite + pearlite, acicular ferrite (AF), and bainitic ferrite (BF) due to the cooling rates increasing from 5 to 3000°C min^?1, in present investigated HSLA steel. The result shows that, the increase of cooling rate accelerates AF transformation and refines the steel's matrix. The morphology of martensite/austenite structures transformed from islands in AF to films in BF with the increase of cooling rate.     

Effect of Solid Solution Treatment on Microstructure of Fe-Ni Based High Strength Low Thermal Expansion Alloy

The influence of solid solution treatments on the dissolution of carbides precipitates,the grain size,and the hardness of high strength low expansion alloy were investigated through XRD analysis,microstructure observations,and theoretical computation.It was seen that most primary Mo2C type carbide band dissolved in a temperature range of 1 100-1 150 ℃.When the temperature was over 1 200 ℃,the grain size increased remarkably,which led to the reduction of hardness.     

硼对低焊接裂纹敏感性高强钢组织性能的影响

 分析了在控轧、控轧加回火、调质等不同工艺条件下,硼对低焊接裂纹敏感性钢显微组织和力学性能的影响。结果表明,硼抑制先共析铁素体形成,提高淬透性,在控轧工艺下含硼钢形成粗大的贝氏体和马氏体组织,并保留了原始奥氏体晶界;调质工艺得到回火索氏体组织,但含硼钢的大角度晶界比例与无硼钢相比较低。硼在强度上的作用显著,上述3种工艺下含硼钢的抗拉强度分别比无硼钢高300, 214, 101MPa,屈服强度分别高320,259,144MPa,但伸长率和冲击韧性均有所降低。无硼钢在调质工艺下、含硼钢在控轧加回火工艺下具有较好的强韧性匹配。     

粒状贝氏体对超低碳含铜时效钢粗晶热影响区冲击韧性的影响

研究了粒状贝氏体对超低碳含铜时效钢粗晶热影响区(CGHAZ)冲击韧性的影响。结果表明,粒状贝氏体中M-A岛的含量和尺寸对超低碳含铜时效钢CGHAZ的冲击韧性有显著影响。当M-A岛的数量少、尺寸小(其体积分数小于3％,尺寸小于1μm)时,粒状贝氏体对CGHAZ的冲击韧性影响不大;当M-A岛的数量多、尺寸大(其体积分数大于3％,尺寸大于1μm)时,CGHAZ的冲击韧性显著下降。通过降低钢中的碳及碳化物形成元素的含量可减少CGHAZ中粒状贝氏体的数量,从而提高钢的CGHAZ的冲击韧性。     

热处理对高硼低碳铸钢显微组织和性能的影响

在含碳量小于0.2%的低碳铸钢中加入1.0%B,获得了高强度高硼耐磨铸钢,并研究了淬火温度对高硼铸钢显微组织和性能的影响.结果显示,在900～1 050℃内淬火,均可获得单一的马氏体组织,淬火温度的变化对硬度影响不明显.随着淬火温度提高,硼化物由连续网状分布变成断网状分布,导致冲击韧性提高;淬火温度超过1 000 ℃后,冲击韧性变化不明显.另外,在900～1 050 ℃内淬火,高硼铸钢均具有优良的耐磨性.     

正火冷速对10MnNiCr船体钢M-A岛和韧性的影响

采用Gleeble试验机模拟了10MnNiCr钢正火处理的连续冷却过程,观察了不同冷速下的显微组织,绘制了CCT曲线,测试了显微硬度和冲击功。结果表明:当该钢以0.167~15℃/s的速度冷却时,形成了M-A岛状组织;随着冷速提高,M-A岛附近的基体组织从粗大的多边形铁素体变为细化的贝氏体铁素体,岛的尺寸减小,与基体之间的硬度差值减小,冲击韧性改善。     

TMCP工艺对微合金高强度钢组织性能的影响

  在实验室条件下,对一种微合金高强度钢进行热膨胀试验和热轧试验,测定了该试验钢的连续冷却转变动力学(CCT)曲线,并研究了不同温度转变的组织和第二相的体积分数、尺寸对其力学性能的影响。试验结果表明：变形温度的降低,贝氏体转变开始温度与转变结束温度均升高,硬度值也出现不同程度的提高;变形温度的降低,使得不同冷却速度下组织细化程度存在明显差异。利用合理控轧控冷工艺,使得屈服强度均达到690MPa以上,-30℃冲击功均达到230J以上。其中,第二相粒子在整个基体内呈细小弥散分布,起到有效的强化作用并改善钢的冲击韧性。     

Development of Dual Phase and Multiphase High Strength Steels by Using a New Cooling Technology: The Howaq‐Twice Process

In order to develop low alloy dual and multiphase high strength steels, CRM and Arcelor implemented the Howaq‐twice process in a continuous annealing line. This new equipment combines a slow primary cooling with a fast secondary cooling. Various cooling strategies were investigated in regard to microstructure and mechanical properties of low alloyed steels. Depending on the cooling rate and the quenching temperature, the microstructure varied between fully martensitic, ferritic‐martensitic, and ferritic‐martensitic‐bainitic. The associated tensile strengths reached from 720 to 1100 MPa.     

Effect of Martensite Morphology on Impact Toughness of Ultra-High Strength 25CrMo48V Steel Seamless Tube Quenched at Different Temperatures

A 25CrMo48V steel for ultra-deep oil/gas well casings was quenched at 900-1 200 ℃ and tempered at 650 ℃. The lath martensitic structures were characterized by optical microscope (OM), field emission scanning electron microscopy (FESEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM), and the transverse impact energy at 0 ℃ was measured from the as-quenched and tempered specimens. The results show that with the quenching temperature decreased, the prior austenite grain, martensitic packet and block are refined, while the lath width seems to remain unchanged. The enhancement of impact toughness with the decreasing quenching temperature can be attributed to refinement of the martensitic structure with high-angle boundaries, and the block is the minimum structure unit controlling impact toughness. The transverse impact energy [ECVN (0 ℃) ≥100 J] required for seamless casings with ultra-high strength (Rp0.2≥932 MPa) has been finally achieved with the experimental steel quenched at 900-1 000 ℃ and tempered at 650 ℃.