热轧带肋钢筋钒钛微合金化生产试验

在１０ｔ电炉和１５ｔ转炉上进行钒微合金化冶炼及轧制钒钛钢筋的试验。按英标ＢＳ４４４９组织了大指一生产。按ＧＢ１４９９－９１ ＲＬ４００原Ⅲ级２０ＭｎＳｉＶ，２０ＭｎＳｉ进行了小批量试制；ＲＬ５４０原Ⅲ级２０ＭｎＳｉＶ，２０ＭｎＳｉ进行了小批量试制；ＲＬ５４０原Ⅳ级４０Ｓｉ２ＭｎＶ进行了多年的工业性试验生产；通过本文对比分析，以求达到国际ＧＢ１４９９－９８ ３个级别ＨＲＢ３３５、４００，５００的各项     

铌微合金化热轧带肋钢筋表面裂纹研究

通过采用金相显微镜、扫描电镜及能谱分析等手段,对铌微合金化热轧带肋钢筋的连铸方坯质量及钢筋表面裂纹进行了分析研究.结果表明,连铸方坯上的中心疏松、中间裂纹和中心裂纹颇为严重,分析认为这些缺陷是浇注温度、冷却强度和拉坯速度等因素综合影响的结果.钢筋表面裂纹为纵向裂纹,主要是由表层及亚表层的夹杂物而并非连铸方坯内部裂纹所引起的,讨论了夹杂物对钢筋纵向裂纹扩展和分叉的影响,裂纹扩展时遇到难以变形的大颗粒夹杂易发生分叉.提出了优化冶炼和改进连铸工艺等相关措施并取得了良好的效果.     

钒微合金Φ25mm热轧左旋带肋钢筋的研制与生产

通过对热轧左旋带肋钢筋（HRBL600）的质量特性分析,制定了热轧左旋带肋钢筋的化学成分,孔型设计方案和生产工艺。生产实践证明：该产品开发获得成功,产品质量达到标准要求。     

铌微合金化HRB400E热轧带肋钢筋生产实践

介绍了柳钢铌微合金化生产HRB400E热轧带肋钢筋的生产工艺,通过低淬透性成分设计、合理的加热温度及开轧温度、轧后有限冷却,柳钢成功控制了Nb微合金化钢筋的无屈服现象,确保金相组织为F+P,避免表层环状组织,并获得了稳定的力学性能.     

钒氮微合金化HRB500E热轧带肋钢筋开发

HRB500E热轧带肋钢筋开发难点在于既要满足高强度,又要满足强屈比≥1.25抗震要求。国内部分钢厂采用VN16合金化工艺生产HRB500E,钢筋强屈比难以达到1.25,针对上述问题采用"VN16+FeV80"钒氮合金化工艺,将钒控制在0.07%～0.11%,氮控制在0.011%～0.015%,通过既发挥钒的析出强化作用又不至于钒过量析出导致强屈比显著下降技术手段,开发并批量稳定生产出强屈比富余量充足的?12～?32 mm规格HRB500E热轧带肋钢筋,解决了单独采用VN16合金化生产HRB500E钢筋强屈比不合格难题。     

钒、氮微合金化钢筋的强化机制

研究了钒、氮微合金化钢筋的强化机理。研究结果表明 ,对 0 .11% V - 85× 10 - 6 N的低氮钢 (钒钢 ) ,约 35 .5 %的钒以 V (C,N)形式析出 ,5 6 .4%的钒固溶在基体中。而在 0 .12 % V- 180× 10 - 6 N的高氮钢中 (钒 -氮钢 ) ,V (C,N)析出量成倍增加 ,约 70 %的钒以 V (C,N)形式析出 ,只有 2 0 %的钒固溶于基体。增氮后 ,V (C,N)析出相的平均尺寸由 10 7nm减小至 73.7nm ,且 1～ 10 nm细小质点的质量比由 2 1.1%提高到 32 .2 %。钢中增氮还细化铁素体晶粒尺寸     

钒微合金Φ25 mm热轧左旋带肋钢筋的研制与生产

通过对热轧左旋带肋钢筋(HRBL600)的质量特性分析,制定了热轧左旋带肋钢筋的化学成分,孔型设计方案和生产工艺.生产实践证明该产品开发获得成功,产品质量达到标准要求.     

钒氮微合金化工艺开发HRB400热轧带肋钢筋的生产实践

章总结了公司90吨转炉采用钒氮微合金化工艺开发HRB400钢的生产实践。结果表明，采用本工艺生产HRB400热轧带肋钢筋，力学性能稳定可靠，吨钢可降低生产成本75元，具有良好的经济效益。     

钒微合金化HRB400热轧带肋钢筋加热制度探讨

通过探讨钒在HRB400热轧带肋钢筋中的强化作用机理,对影响其弥散析出的加热制度进行了分析,在此基础上,改进了加热和冷却工艺,杜绝了强度不合格的现象,稳定并提高了产品质量。     

Study of Bake Hardenability and Strengthening Mechanism of Hot Rolled Low Carbon Steel

The controlled rolling and controlled cooling,bake hardening experiments have been carried out for the test steel,mechanical property test of the sample and microstructure analysis have been made by tensile testing machine,optical microscope,TEM and X-ray diffractometer.The results show that fine and uniform microstructures can achieve much higher BH and BHT values;With the increase of pre-strain there is a trend of increase first and then decrease in the BH and BHT values;bake hardening mechanism mainly consists of Cottrell atmosphere strengthening,second phase strengthening,dislocation strengthening.     

Strengthening Mechanism of a New 700 MPa Hot Rolled High Strength Steel

The microstructural evolution in a 700 MPa hot rolled high strength steel was analyzed in terms of strengthening mechanisms.The results show that the hot rolled sheet steel has yield strength of 710 MPa with good elongation and toughness.The strength of the developed 700 MPa hot rolled high strength steel is derived from the cumulative contribution of fine grain size,dislocation hardening and precipitation hardening.The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength,and the amount of precipitation hardening is two or four times higher than that of conventional microalloyed hot rolled sheet steels reported in the past.Good toughness is due to refinement of ferrite grain size.     

Development of TiMicroalloyed 600 MPa Hot Rolled High Strength Steel

 A high strength steel with tensile strength on the order of 710MPa had been development successfully with only addition of titanium alloy element based on a low carbon steel. The results show the hot deformation accelerates ferrite and pearlite transformation and retards bainite transformation under continuous cooling condition. The microstructure of this steel is mainly composed of fine-grained ferrite and carbides distributed along the ferrite grain boundaries. The yield and tensile strengths of steels are about 620～650MPa and 720～740MPa, respectively, and the values of strain hardening exponent (n) and plastic strain ratio (r) are 0.12 and 0.80, respectively, thus providing well-matched strength with toughness. In short, the fine-grained ferrite and TiC nano-precipitates play an effective role in strengthening the steel.     

Fatigue Performance of Microalloyed High-strength Rebar and Analysis of Fracture Mechanism

Fatigue performance of hot-rolled ribbed-steel bar with the yield strength of 500MPa(HRB500)was studied with bend-rotating fatigue test at a stress ratio of R=-1.It is determined by staircase method that its fatigue strength for 10~7 cycles is 451 MPa,which is higher than that of common carbon structural steel.This should be attributed to the fine-grain strengthening resulting from the high content of alloy element V and Thermo-Mechanical Control Process(TMCP).The S-N curve function is also obtained by nonlinear regression with three parameters power function.The fatigue fractures of the specimen were further analyzed with Scanning Electron Microscopy(SEM)and Energy Disperse Spectroscopy(EDS)to study the fracture mechanism.Taking into account microstructure,hardness and cleanliness of the material,it implies that the fatigue fractures of HRB500 rebar all arise from surface substrates in which many brittle inclusions are contained,and that the fatigue crack propagation is principally based on the mechanism of quasi-cleavage fracture,because of the intracrystalline hard spots leading to stress concentration and thus to the cracks.Moreover,the transient breaking area exhibits microvoid coalescence of ductile fracture due to the existing abundant inclusions.     

Ti在热轧钢板中沉淀强化行为的试验研究

研究了低C-低Mn—Ti钢中Ti的沉淀相在加热过程中的变化规律。在传统的加热温度区间内,Ti在奥氏体中的最大固溶度约为0．14％,而TiN、Ti2S回溶量很小。在580℃卷取时,Ti的析出相尺度在5nm以下,有很好的强化作用,Ti的析出相尺度及形态变化,对强化作用有较大影响。     

Hot Ductility Evolution Mechanism of Titanium-Bearing Microalloyed Steels

Titanium-bearing (Ti-bearing) microalloyed steels have high strength and toughness by grain refinement effect of carbonitride precipitates. However, they can induce surface cracks of continuous casting slab when the Ti alloyed content is high. A microalloyed steel with Ti content (0.10–0.15 wt%) is carried out by thermalmechanical simulator over 600–1350 °C to analyze hot ductility evolution mechanism. Fracture surface morphology, phase transition, and behavior of precipitates of the tensile samples are investigated by experimental detection and thermodynamic calculation. The ductility–temperature curves show that the third brittle temperature range is 600–890 °C, which is mainly attributed to the thin proeutectoid ferrite film and precipitated titanium carbonitride particles, widening the embrittlement temperature ranges through of steel. In addition, the tensile samples at 890–1350 °C have good hot ductility, indicating the dynamic recrystallization of deformed austenite can trigger grain boundaries migration away from cracks and avoid the side effect of the Ti (C,N) particles on hot ductility. The first brittle temperature range of 1350 °C-melting point is mainly ascribed to the partial melting of the grain boundaries with element segregation of sulfur and phosphorus, and microporosity loose among dendrites.     

400MPa级热轧碳素结构钢筋盘条的生产实践

张钢采用控轧控冷技术生产400MPa级热轧碳素结构钢筋盘条,控制轧制采用二阶段变形制度;轧制中间阶段的控制冷却采用设定精轧入口温度和减定径入口温度,轧后一次控制冷却采用设定吐丝温度,二次控制冷却采用开启前6台风机,开口度为85%,三次冷却采用空冷。产品组织为铁素体+珠光体,晶粒细小均匀,屈服强度448.6MPa,抗拉强度650.8MPa,伸长率29.5%,完全满足标准要求。     

600MPa级钒氮微合金化热轧高性能钢筋的研制

介绍了济钢钒氮微合金化HRB600钢筋的生产实践.通过转炉冶炼、炉外精炼和全连续轧机进行了工业试制,应用光谱分析仪、显微镜、拉伸试验机、多功能焊机等设备对试制钢筋的成分、组织、性能,特别是钢筋的时效性、焊接工艺性能、疲劳性能进行了分析.结果证明,采用钒氮微合金化工艺试制的产品的屈服强度达到670 MPa、抗拉强度达到800 MPa,断后伸长率达到19％以上,钢筋具有在500万次高周疲劳应力下未发生断裂的疲劳性能,时效试验表明产品性能稳定,并且适用于多种焊接和机械连接方式,满足行业标准的要求,其生产工艺具有一定的经济优势.     

汽车结构用Nb-Ti复合微合金化热轧钢板的研制

介绍了鞍钢采用1780机组生产的Nb-Ti复合微合金化QSTE系列汽车结构用热轧带钢的生产工艺与组织性能.QSTE系列汽车结构用钢板具有良好的强韧性配合,优良的成形性能及高的尺寸精度,可以满足汽车实际生产工艺的要求.