冷却工艺对Ti微合金化高强钢组织和硬度的影响

通过热模拟实验,研究了冷却工艺参数对Ti微合金化高强钢组织和硬度的影响。结果表明:当终冷温度为700℃时,随着冷却速度的增大,铁素体和珠光体组织得到了显著细化,实验钢硬度增加;随着终冷温度的降低,多边形铁素体晶粒尺寸呈减小趋势,铁素体和珠光体含量逐渐降低,珠光体片层间距逐渐减小,贝氏体含量增加,相变强化和细晶强化共同作用使得实验钢的硬度逐渐增加;钢中存在少量粗大的TiN和Ti_4C_2S_2粒子,冷却速度由5℃/s增大到30℃/s, TiC粒子的析出数量明显增加,平均尺寸由8.1 nm减小到6.7 nm;终冷温度由700℃降到600℃,第二相粒子TiC的析出数量逐渐减少,平均析出粒子尺寸由6.7 nm减小到5.9 nm。研究结果为Ti微合金化高强钢控制冷却工艺的制定奠定了理论基础。     

铌微合金化抗震钢筋形变奥氏体连续冷却转变

 为了研究铌对高强抗震钢筋生产过程中组织转变的影响,通过热模拟试验对比研究了无铌碳素钢筋及铌微合金化钢筋(铌质量分数为0.03%)形变奥氏体在不同冷却速率下的组织和相变规律,获得动态CCT曲线。研究结果表明,添加0.03%铌使试验钢奥氏体连续冷却转变有明显变化。从连续冷却曲线(CCT)可看出,添加铌后,发生先共析铁素体、珠光体相变的冷却速度范围减小,铁素体、珠光体转变温度降低;贝氏体相变的冷却速度区间整体右移。添加铌能细化组织,各冷却速度下含铌钢的硬度均大于无铌钢。利用TEM对不同冷却速度下含铌钢中析出相进行观察,发现Nb(C,N)弥散分布于钢中,随着冷却速度的增加,析出的Nb(C,N)逐渐减少,析出相尺寸呈先减小后增大的规律,2 ℃/s冷却速度冷却得到的析出相尺寸细小且数量较多。     

冷却工艺对Ti微合金化高强钢组织和硬度的影响

摘要：通过热模拟实验,研究了冷却工艺参数对Ti微合金化高强钢组织和硬度的影响。结果表明：当终冷温度为700℃时,随着冷却速度的增大,铁素体和珠光体组织得到了显著细化,实验钢硬度增加;随着终冷温度的降低,多边形铁素体晶粒尺寸呈减小趋势,铁素体和珠光体含量逐渐降低,珠光体片层间距逐渐减小,贝氏体含量增加,相变强化和细晶强化共同作用使得实验钢的硬度逐渐增加;钢中存在少量粗大的TiN和Ti4C2S2粒子,冷却速度由5℃/s增大到30℃/s,TiC粒子的析出数量明显增加,平均尺寸由8.1nm减小到6.7nm;终冷温度由700℃降到600℃,第二相粒子TiC的析出数量逐渐减少,平均析出粒子尺寸由6.7nm减小到5.9nm。研究结果为Ti微合金化高强钢控制冷却工艺的制定奠定了理论基础。     

铌微合金化对高铁车轮钢奥氏体形核和长大的影响

 针对碳质量分数为0.47%中碳高铁车轮钢,研究了铌微合金化对前驱体为铁素体-珠光体的组织发生奥氏体逆相变的影响。结果表明,铁素体-珠光体钢的逆相变是一个由碳原子扩散控制的过程,奥氏体优先在珠光体内的铁素体与渗碳体（α/Fe3C）片层界面处形核,并且沿平行于珠光体片层方向的长大速率比垂直于珠光体片层方向更快。含铌车轮钢细化的珠光体组织可以提高奥氏体的形核率,有利于细化奥氏体晶粒。随着再加热温度的提高,含铌车轮钢的奥氏体混晶温度（960 ℃）比不含铌的钢高80 ℃,因此通过铌微合金化可扩大再加热奥氏体化温度窗口。结合Thermal-Calc热力学计算和透射电镜分析,铌在中碳钢中主要以析出物的形式存在,析出钉扎作用是其细化奥氏体晶粒、推迟混晶现象出现的主要机制。     

Nb对0Cr11铁素体不锈钢组织和性能的影响

 铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域。研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响。研究结果表明：Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC 和 Fe2Nb析出相,其透射电镜观察结果与Thermal calc计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果。     

Nb对OCrll铁素体不锈钢组织和性能的影响

铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域.研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响.研究结果表明:Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC和FezNb析出相,其透射电镜观察结果与Thermal-eale计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果.     

冷轧TRIP590钢带的成分优化

 化学成分和热处理工艺是影响TRIP钢力学性能的关键因素。通过热模拟试验方法研究了不同成分试验钢在临界区退火过程中的微观组织变化规律。结果表明：随着两相区退火温度的升高,铁素体平均晶粒尺寸逐渐减小,铁素体体积分数随着加热温度的升高而降低;残余奥氏体量和其中的C质量分数先随着退火温度的升高而降低,达到一个低谷以后,再随退火温度的升高而升高;在相同的退火温度下,随着Nb的加入,多边形铁素体晶粒尺寸细化,铁素体体积分数逐渐减少;既加Nb又高Si的试验钢钢中残奥数量最多,不加Nb的试验钢中残奥数量最少。TRIP钢试制结果表明,钢带组织类型为典型的TRIP钢组织,多边形铁素体平均晶粒尺寸约8μm,体积分数67%,残余奥氏体体积分数为5.58%,残余奥氏体中C质量分数为1.34%,同时,力学性能也完全满足TRIP590的性能要求。     

终锻温度对Nb-V-Ti复合非调质钢组织及性能的影响

通过金相、扫描、透射电镜研究不同锻造工艺下V-Ti、Nb-V-Ti两种微合金化非调质钢的微观组织结构及力学性能。结果显示:添加Nb能够显著提高非调质钢的奥氏体粗化温度,有效阻止奥氏体晶粒的快速长大,细化非调质钢晶粒,降低珠光体层片间距,使渗碳体呈粒状或球状分布;另外,添加的Nb促进V-Ti非调质钢中细小含铌碳化物的弥散析出,细化基体组织,同时提高非调质钢的强度。因此,Nb-V-Ti复合微合金化非调质钢经过未再结晶区变形后可获得均匀细小的铁素体-珠光体双相组织,且在相对较低的温度进行形变处理能够有效改善Nb-V-Ti微合金非调质钢的强韧性。     

Nb对V、N微合金化压力容器钢珠光体形态及低温韧性影响

为了在保证强度同时提升压力容器钢低温韧性，以铌(Nb)取代部分钒(V),研究Nb的添加对V、N微合金化正火压力容器钢板显微组织和力学性能的影响。结果表明，Nb+V试验钢相比于V试验钢，在强度保持630 MPa的同时可显著提升低温冲击韧性，-20、-40、-60℃冲击吸收功分别提升59、44、29 J。原因主要为Nb的添加促进了细小铁素体转变，其含量的增加使钢的塑韧性增强。此外V和Nb+V钢中碳原子扩散系数在平均转变温度下分别为2.64×10^-13、2.14×10^-13 cm²/s, Nb的添加降低了珠光体生长速度、增加了珠光体转变过程中的过冷度，从而细化了珠光体团簇和片层间距。EBSD分析可知以Nb取代部分V后试验钢有效晶粒尺寸由7.7μm减小至5.8μm,大角度晶界比例由83.1%增加至85.5%。微合金元素Nb的细晶作用及对大角度晶界比例提升的贡献也可以大幅提高钢的低温冲击韧性。     

Nb微合金化对齿轮钢高温渗碳奥氏体晶粒度的影响

摘要：通过Nb微合金化提高渗碳温度是当前发展高端齿轮钢的重要思路。以20Cr钢为基准成分,通过实验室熔炼、锻造以及977~1134℃范围内高温伪渗碳实验,研究了0.02%、0.04%、0.06%、0.08%等不同Nb质量分数下渗碳后的奥氏体晶粒结构。在此基础上,依据热力学计算及析出颗粒熟化模型,对AlN、Nb(C,N)颗粒的钉扎强度进行估算并与晶粒尺寸建立联系,得到了适用于含Al、Nb齿轮钢的奥氏体晶粒度控制预测模型。最后,依据此模型分析了Nb含量对20Cr钢渗碳温度的影响,并基于高温渗碳目标提出了Nb微合金化的成分建议。     

Effect of N content on microstructure and properties of Nb microalloyed HRB400E rebar

The purpose of this study is to better play the role of N in Nb microalloyed rebars, in order to reduce production costs and provide a theoretical basis for the design of rebars. Using metallographic microscope, scanning electron microscope, transmission electron microscope, and mechanical testing machine to carry out microstructure characterization and mechanical performance test of different N content of Nb microalloyed high strength seismic rebars, and explore the effect of N content on the structure and mechanics of Nb microalloyed high strength anti seismic rebars. The results show that the austenite structure during the rolling process decreases with the increase of N content; the final structure is ferrite and pearlite. As the N content increases, the average ferrite grain size and the interlamellar spacing decreases, but the continuity of lamellar pearlite increases. In Nb microalloyed high strength anti seismic rebars, the precipitated phase is Nb(C,N). With the increase of N content, the number of precipitated phase and the second particle volume fraction of precipitation increases, but the particle size decreases accordingly. In terms of mechanical properties, the yield strength gradually increases, and the tensile strength shows a phenomenon of increasing first and then decreasing.     

Effects of micro-alloying and production process on precipitation behaviors and mechanical properties of HRB600

Effects of micro-alloying elements and production process on microstructure,mechanical properties and precipitates of 600 MPa grade rebars were studied by using pilot test,metallographic observation,tensile test,thermodynamic calculation and transmission electron microscopy. The results show that the tested steels are composed of ferrite and pearlite,in which the content range of pearlite is 33%-45%. For vanadium microalloyed steel,interphase precipitation strengthening effect of V can be promoted and the yield strength of tested steels can be increased with increasing V content and decreasing finishing rolling temperature. The temperature of terminated cooling should be more than 700 °C when the water cooling is used. When niobium is added to the steel,more coarse( Nb,V) C,N precipitates are generated at high temperature,so that the solid solubility of precipitated phases of vanadium is reduced and the precipitation strengthening effect of vanadium is weakened.     

轧后冷却工艺对高强度汽车发动机裂解连杆用钢组织和性能的影响

采用金相显微镜、扫描电镜和透射电镜等分析方法,研究了轧后冷却工艺对高强度汽车发动机裂解连杆用微合金非调质中碳钢的组织和性能的影响。结果表明,提高轧后冷却速度有利于钢中珠光体比例的增加,降低铁素体晶粒尺寸和减少珠光体片层间距;钢中的第二相沉淀析出相主要是弥散分布在铁素体基体中的(V,Ti)(C,N)复合相,粒度在30~170 nm,随着轧后冷却速度的增加而减小;而其屈服强度随轧后冷却速度的增加而提高,在高的冷却速度下,其屈服强度达到770 MPa,其中析出相对屈服强度的贡献达到174 MPa。     

Microstructure deformation mechanism of SEM in- situ tension in high- strength anti- seismic rebars

To study the effect of different tissues on the performance of high- strength anti- seismic rebars, the law of its microstructure deformation behavior was obtained. The microstructures of three kinds of 500MPa high- strength anti- seismic rebars with different structural features were analyzed, which is mainly pearlite and ferrite, pearlite, ferrite and a small amount of bainite, as well as pearlite, ferrite and a large amount of bainite, respectively. The in- situ tension tests were used to investigate and study the polyphase microstructure deformation, polyphase microstructure coordination deformation mechanism and fracture mechanism. The results indicate that the ferrite and pearlite are deformed obviously in the test steels mainly with ferrite and pearlite. The ferrite is firstly deformed, however, the reason for unobvious deformation in pearlite may be attributed to the hindered effect caused by hard phase bainite. As the amount of deformation increases, the pearlite breaks finally. In the test steels which mainly composed of ferrite, pearlite and a small amount of bainite, the bainite does not substantially deform at the initial stage, while it impedes the deformation of ferrite and pearlite with only a certain degree of deformation. In the test steels which mainly composed of ferrite, a small amount of pearlite and a large amount of bainite, the initial deformation mainly begins in ferrite deformation, while the pearlite deformation is not obvious because of its low content. With the increase in deformation, the deformation of bainite becomes more and more obvious. When it reaches a certain extent, pearlite begins to deform and finally gets fracture.     

微合金化控冷工艺开发HRB500E高强度抗震钢筋

针对红河钢铁有限公司炼钢、轧钢工艺装备,采用微合金化控轧控冷工艺生产HRB500E高强度抗震钢筋,并利用金相显微镜、拉力试验机对钢筋的力学性能、金相显微组织、夹杂物进行检验。结果表明:钢筋强韧性适中,具有较好的抗震性能和低应变时效性;控制钢中Mn含量小于1.55%,Nb含量小于0.025%,控冷终止温度大于680℃,钢筋心部组织为铁素体+珠光体+5%贝氏体,综合性能较佳。     

冷作硬化非调质钢的连续冷却相变规律

钢的连续冷却相变曲线(CCT)是组织调控的基本依据,为了优化紧固件用冷作硬化非调钢热轧态的组织和力学性能,采用DIL805A相变仪测定了试验钢在0.1～50℃/s不同冷却速率下的热膨胀曲线,结合金相硬度法确定相变类型,并绘制了试验钢的CCT曲线.结果 表明,试验钢马氏体转变点(Ms)为280℃,在不同冷速范围内均有铁素...     

500 MPa级高延性方管用钢的开发及加工硬化行为

 为了开发满足二次加工性能要求的500 MPa级高延性方管用钢,采用OM、SEM和TEM等对500 MPa级高延性方管用钢制管前后的组织与性能进行分析,研究了其强化机制与加工硬化机理。结果表明,两种试验钢的组织均由铁素体和少量珠光体组成,低C-低Mn-Nb、Ti微合金化试验钢铁素体晶粒与珠光体球团尺寸更加细小,第二相析出物尺寸稍大,位错密度相似。两种试验钢制管前力学性能相似,低C-低Mn-Nb、Ti微合金化试验钢屈强比较高;制管后低C-低Mn-Nb、Ti微合金化试验钢加工硬化程度显著,屈服强度、抗拉强度分别增加了45与26 MPa,伸长率降低6.0%,高C-高Mn-Nb微合金化试验钢屈服强度、抗拉强度分别增加了22与10 MPa,伸长率降低4.0%。固溶强化与细晶强化是两种试验钢最主要的强化机制,由晶粒细化引起的强度增量占总强度的52.9%~61.8%,由固溶强化引起的强度增量占总强度的17.2%~25.3%;析出强化与位错强化对强度的贡献较小。制管后低C-低Mn-Nb、Ti微合金化试验钢位错强化增加显著,达到了82 MPa,明显高于高C-高Mn-Nb微合金化试验钢位错强化的贡献(65 MPa);对于制管用途而言,高C-高Mn-Nb微合金化试验钢制管后综合力学性能更加优异。     

Nb-Ti微合金化对热轧0.5~0.7Cr铲斗刀板型钢组织和性能的影响

试验0.5~0.7Cr铲斗刀板型钢（/%:0.22~0.30C,0.25~0.45Si,0.95~1.20Mn,0.006~0.009P,0.008~0.010S,0.5~0.7Cr,0.015~0.065Nb,0~0.040Ti）由50kg真空感应炉熔炼,热轧成16mm厚板,终轧温度850~900℃,空冷。通过光学显微镜、扫描、透射电镜和力学性能测试研究了Nb-Ti含量（0.015Nb,0.035Nb-0.010Ti,0.065Nb-0.040Ti）对热轧态铲斗刀板钢组织和力学性能的影响。结果表明,试验钢组织为F+P,随Nb-Ti含量增加,钢板的晶粒细化,珠光体片层间距降低,（Nb,Ti）C和（Nb,Ti）(C,N)析出物增多,强度增加,0.065Nb-0.040Ti钢板的力学性能为屈服强度632MPa,抗拉强度916MPa,延伸率17.7%,K_AV40 J,HB硬度值234。