终轧和终冷温度对X65/X70中厚板管线钢屈强比的影响

通过对不同终轧、终冷温度条件下X65/X70中厚板管线钢的板屈强比值和微观组织的变化研究发现,当终轧温度低于Ar3温度时,钢板进入两相区轧制,钢板组织呈带状分布,钢板屈服强度的提高幅度大于抗拉强度的提高,屈强比呈上升趋势.水冷中钢板头部温度过冷对屈强比控制也非常不利.通过对X65/X70管线钢进行控轧控冷工艺优化,屈强比值得到显著降低,大幅提高了管线钢板合格率和成材率.     

终冷温度对高强度管线钢屈强比的影响

通过控制终冷温度得到不同微观组织的管线钢,研究了显微组织对管线钢屈强比的影响,结果表明,板条状贝氏体型管线钢比针状铁素体型管线钢具有更低的屈强比,板条贝氏体型管线钢中细小弥散的析出对降低屈强比是有利的.     

CSP酸洗钢SAPH370的冷却工艺优化

 屈强比偏高是CSP产品的共性问题。为降低CSP酸洗钢SAPH370的屈强比,采用正交化试验设计,研究了两段冷却工艺参数终轧温度、空冷起始温度和卷取温度对屈强比的影响。对试验结果进行统计,并利用光学显微镜分析了不同工艺条件下SAPH370钢的相组成和晶粒尺寸。研究结果表明,空冷起始温度和卷取温度对屈强比的影响显著。空冷起始温度由740℃提高到760℃,可降低屈强比0.017;卷取温度由500℃提高到560℃,可降低屈强比0.015;而终轧温度对屈强比的影响不太明显,终轧温度由860℃提高到880℃,屈强比仅降低0.005。采用两段冷却工艺,通过调整空冷起始温度和卷取温度可有效降低酸洗钢SAPH370的屈强比。     

控制冷却工艺对X70管线钢屈强比的影响

本文研究了影响X70管线钢屈强比的几个因素，结合实际生产经验，介绍了冷却工艺参数如开冷温度、终冷温度、冷却速度以及冷却方式对屈强比的影响。     

17.5 mm厚度X70管线钢屈强比偏高的原因分析

通过对成分、工艺、组织和检验方式等屈强比主要影响因素的分析,对马钢生产的厚度17．5mm的X70管线钢屈强比偏高的原因进行了探讨,并结合实际生产情况进行了工艺调整,最终降低了该管线钢的屈强比,对生产高级厚规格的管线钢热轧卷板屈强比控制具有较高的参考价值。     

TMCP工艺对高性能桥梁钢Q370qE-HPS组织性能的影响研究

为了研究TMCP工艺对Q370q E-HPS高性能桥梁钢组织和性能的影响,达到替代正火工艺的目的,对终轧温度、开冷温度、返红温度及冷却速率等TMCP关键工艺参数与组织、力学性能的关系进行分析。结果表明:采用两阶段控轧控冷工艺生产Q370q E-HPS钢时,随终轧温度升高、开冷温度降低、返红温度升高及冷却速度降低,铁素体晶粒尺寸增大,珠光体含量增加,屈强比降低。通过工艺参数优化,可获得合适尺寸和体积分数的铁素体和珠光体,实现Q370q E-HPS钢良好的强韧性匹配和较低的屈强比。     

控轧控冷工艺对X70管线钢组织与性能的影响

对21 mm X70管线钢的控轧控冷工艺进行了试验分析,表明合理控制精轧温度、终轧温度和终冷温度可以得到组织细化和性能良好的针状铁素体管线钢板.     

高性能管线钢控制轧制与控制冷却

从加热温度、轧制变形量、终轧温度三方面论述了高性能管线钢在生产过程中的控制轧制工艺,分析了开冷温度、终冷温度、冷却速度等方面在控制冷却中对高性能管线钢最终组织结构和性能的影响,以及微合金化元素Nb、Ti、V在控轧控冷中的作用,为高性能管线钢的生产工艺参数制定提供理论基础。     

60 mm厚低屈强比高强钢板Q500qE组织与性能研究

通过JMatpro软件、扫描电镜、力学性能测试,对Q500qE 60 mm厚度500 MPa级低屈强比高强钢板进行了连续冷却转变(CCT)曲线、钢板显微组织与力学性能、焊接接头力学性能分析。结果表明,通过控轧控冷工艺：终轧温度800～840℃,入水温度660～680℃和终冷温度400～450℃,该钢组织为铁素体+贝氏体+马氏体/奥氏体岛,两相交界处和贝氏体内部存在大量大角度晶界。钢板1/4和1/2厚度位置屈服强度≥500 MPa,抗拉强度≥640 MPa,屈强比≤0.80,-40℃低温冲击功≥200 J,焊接热影响区-40℃低温冲击功≥100 J。     

低屈强比油罐钢生产工艺优化

低屈强比钢板要求双相组织,生产控制难度大。通过发挥预矫直机的大压下量预矫作用,优化Mulpic水冷参数,改善了钢板板形及性能;优化回火温度及时间,控制组织内软硬相比例,确保了钢板各项性能及屈强比。济钢采用在线淬火+离线回火的工艺生产的油罐钢屈强比在0.90以下,一次性能合格率90%以上。     

控轧控冷工艺对X80管线钢强度影响的统计分析

重点分析了X80管线钢在控轧控冷过程中工艺对于屈服强度、抗拉强度的影响。通过大生产试验和数据回归,进一步分析出影响X80管线钢强度的主要因素,其中影响屈服强度主要因素为终轧温度、终冷温度,与其呈负相关;而冷却速率和Mo含量与其呈正相关。同时,影响抗拉强度的主要因素为终轧温度和终冷温度,与其呈负相关;而冷却速率、Mo含量和碳当量则与其呈正相关。最后得出了各个影响因素对强度影响的经验公式。     

Effects of Cooling Conditions on Microstructure, Tensile Properties, and Charpy Impact Toughness of Low-Carbon High-Strength Bainitic Steels

In this study, four low-carbon high-strength bainitic steel specimens were fabricated by varying finish cooling temperatures and cooling rates, and their tensile and Charpy impact properties were investigated. All the bainitic steel specimens consisted of acicular ferrite, granular bainite, bainitic ferrite, and martensite-austenite constituents. The specimens fabricated with higher finish cooling temperature had a lower volume fraction of martensite-austenite constituent than the specimens fabricated with lower finish cooling temperature. The fast-cooled specimens had twice the volume fraction of bainitic ferrite and consequently higher yield and tensile strengths than the slow-cooled specimens. The energy transition temperature tended to increase with increasing effective grain size or with increasing volume fraction of granular bainite. The fast-cooled specimen fabricated with high finish cooling temperature and fast cooling rate showed the lowest energy transition temperature among the four specimens because of the lowest content of coarse granular bainite. These findings indicated that Charpy impact properties as well as strength could be improved by suppressing the formation of granular bainite, despite the presence of some hard microstructural constituents such as bainitic ferrite and martensite-austenite.     

冷却工艺对抗大变形管线钢X70HD热涂敷性能的影响

抗大变形管线钢加热并保温一段时间后,钢管力学性能将发生变化,通常会有屈服强度、屈强比升高,均匀延伸率降低,应力—应变曲线形状改变等,这些性能变化将降低钢管抵抗变形的能力。利用扫描镜等设备研究了冷却工艺对21mmX70HD抗大变形管线钢组织、性能和应变时效硬化的影响。结果表明,随着开始冷却温度的降低,先共析铁素体含量逐渐增加,贝氏体组织含量逐渐降低,贝氏体的组织相态由粒状贝氏体逐渐向板条贝氏体转变。当开始冷却温度在700℃时,试验钢板具有最佳的综合力学性能。试验钢板制成1016mm钢管后,钢管在200℃时效保温5min下,纵向屈服强度Rt0.5为497MPa,抗拉强度Rm为695MPa,伸长率为41%,屈强比Rt0.5/Rm为0.72,Rt1.5/Rt0.5为1.24、Rt2.0/Rt1.0为1.09,均匀变形伸长率达到9.0%。     

精轧工艺对30 mm厚X65管线钢板组织和性能的影响

Nb-Ti微合金化X65管线钢(/%:0.07C、1.60Mn、0.35Mo)的生产工艺流程为130 t顶底复吹转炉-钢包吹氩-LF-RH-250 mm×1500 mm板坯连铸-连轧至30 mm板-控冷工艺。研究了第Ⅱ阶段开轧(890～940℃)轧后冷却温度(780～850℃)和冷却速度(8～20℃/s)对X65钢厚板拉伸、落锤性能和组织的影响。结果表明,Ⅱ阶段开轧温度为940℃,轧后冷却速度为20℃/s可以使X65钢厚板得到以针状铁素体和粒状贝氏体为主的组织,钢板抗拉强度665～695 MPa,屈服强度495～520 MPa,落锤纤维组织率约为92%,满足标准要求。     

终轧温度对低合金铌钛贝氏体钢组织和性能的影响

 采用光学显微镜、透射电子显微镜（TEM）、EDS能谱分析仪和拉伸冲击试验机,研究了终轧温度对TMCP(thermo-mechanical controlled processing)低合金铌钛贝氏体钢组织和性能的影响。结果表明：随着终轧温度的降低,强度和韧性先升高后降低。终轧温度为815 ℃时,由于冷却前温度已降低到奥氏体-铁素体两相区,在晶界形成大量先共析铁素体,造成了强度和韧性的下降。终轧温度为870 ℃时,得到细小的板条贝氏体＋少量的马氏体组织,在贝氏体板条上有30～50 nm的Nb、Ti析出相弥散分布,获得了最优异的性能,其屈服强度为805 MPa,抗拉强度为1 005 MPa,－20 ℃冲击功的平均值为197 J。     

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.     

Effects of Rolling Processes on Bainite and Mechanical Properties of Ultra-High Strength Pipeline Steel

Ultra-high strength pipeline steels were rolled by thermal mechanical controlling process (TMCP),and effects of the volume fraction,the size and microstructure morphologies of three different bainite (AF,GB and LB) on mechanical properties were investigated by optical microscope.The results showed that,X120 ultra-high strength pipeline steel was rolled through the reasonable thermal mechanical controlling process (TMCP),and the yield strength and the low temperature charpy impact energy (-30℃) were higher than 840MPa and above 230J,respectively,meanwhile,the ratios of tensile strength to yield strength were lower below 0.82.As for X100 pipeline,of which the mechanical property were higher than that by X100 pipeline steel of ISO standard,yield strength of the steel was 715 MPa,ultimate tensile strength 963 MPa,impact energy 282J,and yield ratio 0.74.     

屈服强度460MPa级耐候钢及其焊接性能

通过连续冷却相转变行为的研究,利用试验轧机成功试制了24mm厚,屈服强度460MPa级耐候钢板,并分析了钢板微观组织、力学性能、腐蚀性能以及焊接性能。连续相转变行为和钢板试制结果表明:精轧温度不大于850℃,厚度压下率不小于0.6,冷速为4~15℃/s和终冷温度不大于465℃可得到以针状铁素体(3~10μm)和多边形铁素体(5~15μm)为主的钢板,其屈服强度不小于480MPa,抗拉强度不小于635MPa,伸长率不小于23%,-40℃冲击功不小于209J。对试制钢板进行了热输入量为72kJ/cm的双丝埋弧焊接试验,无焊前预热和焊后热处理,得到了无缺陷焊接接头,焊接热影响区-40℃冲击功不小于100J;粗晶区的高韧性与其晶内铁素体为主以及少量晶界铁素体和上贝氏体的微观组织有关。72h周浸试验结果表明:试制钢种的耐大气腐蚀能力比普碳钢Q345B提高了46%。     

X60管线钢板的控轧工艺研究

针对X60管线用钢板的强度、屈强比、低温冲击韧性等性能的严格要求,采用优化坯料成分、提高钢的纯净度等措施来进行保证;对高强度要求,采用微合金化和不同的控制轧制方式,以细晶强化和沉淀强化机理,找出了适合济钢中板厂的控制轧制工艺,保证了X60钢板的苛刻性能要求,为今后高等级专用板开发提供了良好的借鉴。