控轧控冷对含Nb-Ti微合金汽车用钢组织的影响

采用热模拟实验技术研究控轧控冷工艺对0．09C、1．13Mn、0．03Nb、0．02Ti微合金汽车用钢组织的影响。结果表明，在再结晶区和未再结晶区的累计变形可以得到更细的组织，950℃以下终轧并快速冷却有利于形成针状铁素体组织。变形诱发Nb的碳—氮化物析出，有利于奥氏体晶粒及相变后显微组织细化。     

低碳微合金管线钢的连续冷却相变及组织研究

通过Gleeble 3800热模拟试验机测定了该低碳微合金管线钢的静态（无热变形）和动态连续冷却相变曲线,并通过光学显微镜和电子显微镜对连续冷却后的组织进行了详细观察和分析。发现随着冷却速度的提高,在连续冷却转变组织中依次出现多边形铁素体（PF）、珠光体（P）、针状铁素体（AF）、粒状贝氏体（GB）和下贝氏体（LB）。在未再结晶区的热变形使C曲线发生左移,扩大了试样的针状铁素体区,并使得相变后的组织得到细化。     

低碳微合金管线钢的连续冷却相变及组织研究

通过Gleeble 3800热模拟试验机测定了该低碳微合金管线钢的静态（无热变形）和动态连续冷却相变曲线,并通过光学显微镜和电子显微镜对连续冷却后的组织进行了详细观察和分析。发现随着冷却速度的提高,在连续冷却转变组织中依次出现多边形铁素体（PF）、珠光体（P）、针状铁素体（AF）、粒状贝氏体（GB）和下贝氏体（LB）。在未再结晶区的热变形使C曲线发生左移,扩大了试样的针状铁素体区,并使得相变后的组织得到细化。     

热形变淬火对L485QS酸性管线用钢09MnNb淬硬性的影响

对L485QS酸性管线用钢09MnNb进行不同工艺的热形变淬火试验,测试淬硬性并观察相应的组织。结果表明,试验钢在850～1 100℃进行0.2～0.8变形水淬后可获得三种类型的组织,变形温度是影响组织转变类型的主导因素,当温度≤900℃时,主要获得针状铁素体,当温度为950～1 000℃时,主要获得细条状贝氏体,当温度≥1050℃时,主要获得粗大的板条状贝氏体。增大变形量在未再结晶和部分再结晶区分别促进针状铁素体转变和细条状贝氏体转变,在完全再结晶区使板条状贝氏体组织粗细不一致。采用09MnNb钢在950～1 000℃进行ε≥0.4的热变形淬火时,可获得以细条状贝氏体为主的淬火组织,以及较高且稳定的淬硬性,并有利于后续回火性能的调控。     

Mn-Nb-Mo系X70级管线用钢板的相变

通过Gleeble-1500热模拟试验机，用热膨胀法测定了成分(％)为0．07C，1．52Mn，0．064Nb，0．21Mo，0．015Ti，0．054V的X70管线用钢板分别在850℃和800℃，道次压下量25％，变形速率5s^-1，变形后冷却速率为1．0℃／s至100℃／s时的奥氏体至铁素体的转变温度Ar3，并测定变形温度为800℃时连续冷却转变(CCT)曲线。试验结果表明，当5℃／s冷却时轧制温度由800℃提高至850℃时，Ar3由653℃降至635℃；在低的冷却速度下，转变产物为多边形铁素体和针状铁素体，当冷却速度为25℃／s时，转变产物主要为细的针状铁素体。     

非调质塑料模具钢热加工的模拟研究

采用Gleeble 3800热模拟试验机研究了非调质塑料模具钢(SWFT钢)的热变形工艺,试验结果表明,SWFT钢分别在1000、1050、1100和1150 ℃单道次变形50%后以0.083 ℃/s的速度冷却时,随热变形温度的升高,先共析铁素体组织减少直至消失,但晶粒较粗大.多道次热变形后在相同冷却速度时确保先共析铁素体组织不出现,同时细化因单道次变形温度较高出现的粗大晶粒,为SWFT钢应用于一定截面尺寸的非调质塑料模具钢模块提供了制订锻造工艺的依据.     

Ti-IF钢多道次变形静态再结晶研究

在热模拟实验机上进行了Ti—IF钢多道次铁素体区变形实验，采用后插法确定了静态再结晶分数。在实验的基础上建立了超低碳Ti—IF钢多道次铁素体变形时静态再结晶动力学模型。研究结果表明，建立的超低碳Ti—IF钢多道次铁素体变形静态再结晶动力学模型与实验结果吻合。     

X70管线钢控轧控冷工艺与组织性能的关系

X70管线钢中针状铁素体的比例随热变形后的冷却速度增加而提高,冷却速度为15 ℃/s时达到最大,冷却速度再增加,该比例变化不大。冷却速度较低时(2 ℃/s)和热变形后的终冷温度较高时(650 ℃)组织中出现珠光体。随着终冷温度的降低,试验钢的组织细化,在500~550 ℃终冷时组织较为理想。铁素体晶内弥散分布有尺寸为20 nm左右的析出相,析出相在位错处择优成核并与基体保持共格或半共格关系。     

加速冷却对控轧管线钢组织和性能的影响

采用两种管线钢材料,通过再结晶区和未再结晶区的五道次变形将试样厚度从60mm轧为8mm。热轧后的试样进行水幕冷却,然后分别放置于500℃和400℃的加热炉中随炉冷却以模拟卷取。结果表明,对于两种管线钢材料通过适当的冷却工艺都可以得到以针状铁素为主的组织。     

热变形参数对0.05C-0.13Nb钢相变组织影响

利用Thermecomastor-Z热模拟试验机,研究了含铌0.13%微合金低碳钢奥氏体未再结晶区(超过50%、发生再结晶)变形、并以0.1～50℃/s的冷却速度连续冷却过程的相变。研究了热变形参数对相变组织的影响。结果表明,在未再结晶区变形,在连续冷却条件下,冷却速度≥5℃/s时,90%以上组织为粒状贝氏体;在相同变形温度情况下,随着变形量的增加,先共析铁素体的量增加,贝氏体的量随之减少。     

Effect of hot deformation and Nb precipitation on continuous cooling transformation of a high-Nb steel

In this work, the effects of hot deformation on continuous cooling transformation of a high-Nb steel were investigated on a Gleeble 3500 thermal simulator. The amounts of dissolved Nb were determined by inductively coupled plasma-atomic emission spectrometry. Furthermore, the effects of hot deformation and Nb precipitation on phase transformation were discussed. Results showed that high-Nb steel is suitable for acicular ferrite pipeline steels because the acicular ferrite microstructure can be obtained in a wide cooling rate range. Hot deformation strongly accelerates the polygonal ferrite transformation and increases the critical cooling rate to obtain a full acicular ferrite microstructure. Moreover, hot deformation markedly refines the final microstructure and improves the mechanical properties of acicular ferrite obtained at a high cooling rate. However, hot deformation can also promote Nb precipitation during holding and even cooling at low rates after hot deformation. Nb precipitation dramatically promotes the polygonal ferrite, weakens the effect of Nb in solution on phase transformation and strengthening, and decreases the microhardness.     

CSP连轧过程中低碳钢的组织变化规律

对珠钢CSP生产现场同一低碳钢轧件的铸坯及不同道次变形后室温组织的研究表明：铸坯组织由细晶区（急冷层）和树枝晶区组成，随轧制道次增加，变形后轧件的室温组织细化，沿铁素体晶界分布的珠光体变得均匀，弥散，连轧前铸坯表面和心部的组织差异随着轧制道次增加逐渐减小，珠钢成品板组织细化的原因可以归结为大压下连轧工艺，钢中大量弥散析出的氧化物，硫化物和终轧后的层流冷却。     

Microstructure and Transformation Characteristics of Acicular Ferrite in High Niobium-Bearing Microalloyed Steel

 The transformation behavior and microstructural characteristics of a low carbon high Nb-bearing microalloyed pipeline steel have been investigated by deformation dilatometry and microstructure observation. The continuous cooling transformation curves (CCT) of the tested steel was constructed. High Nb content and deformation enhancing the formation of acicular ferrite; the microstructures are range from PF, QF to AF with increasing cooling rates from 0.5 to 50℃/s and dominated by acicular ferrite in a broadened cooling rate higher than 5℃/s. The chaotic microstructure consists of non-equiaxed ferrite and interwoven ferrite laths distributed high density dislocations and sununits. The results of isothermal holding show that acicular ferrite microstructure is formed in region of 550-600℃. With the holding time or temperature increased, some low misorientations boundaries change to high misotrentationn as dislocations moving and grain boundaries coarsening.     

Microstructure Evolution During Hot Deformation of a Micro-Alloyed Steel

In the present investigation, hot deformation by uniaxial compression of a microalloyed steel has been carried out, using a deformation dilatometer, after homogenization at 1200 °C for 20 min up to strains of 0.4, 0.8 and 1.2 at different temperatures of 900, 1000 and 1100 °C, at a constant strain rate of 2 s^?1 followed by water quenching. In all the deformation conditions, initiation of dynamic recrystallization (DRX) is observed, however, stress peaks are not observed in the specimens deformed at 900 and 1000 °C. The specimens deformed at 900 °C showed a combination of acicular ferrite (AF) and bainite (B) microstructure. There is an increase in the acicular ferrite fraction with increase in strain at all these deformation temperatures. At high deformation temperature of 1100 °C, coarsening of DRXed grains is observed. This is attributed to the common limitations involved in fast quenching of the DRXed microstructure, which leads to increase in grain size by metadynamic recrystallization (MDRX). The strain free prior austenite grains promote the formation of large fraction of both bainite and martensite in the transformed microstructures during cooling. The length and width of bainitic ferrite laths also increases with increase in deformation temperature from 900 to 1100 °C and decrease in deformation strain.     

Evolution of acicular ferritic microstructure in a titanium bearing HSLA steel

An attempt has been made to design and develop acicular ferritic steels by adopting three-stage controlled rolling, with titanium alone as microadditive. Process parameters such as finish rolling temperature (FRT), amount of deformation during the last pass and also the cooling rate after finishing have been altered to obtain different microstructural effects. Optical as well as transmission electron microscopy studies indicated that acicular ferritic microstructure can be engendered by applying a minimum deformation of 25 % at the finishing pass followed by water quenching. Decreasing the FRT from 850 °C, for water quenched steels deformed 33 %, resulted in the refinement of polygonal ferrite, whereas the reverse is the case with the aspect ratio of acicular ferrite. The volume fraction of acicular ferrite progressively increases as the FRT is lowered. Evaluation of tensile properties suggested that yield strength as high as ~ 600 MPa with an elongation of ~ 25 %, could be obtained by finishing at a lower temperature of 750 °C. An impact transition temperature (ITT) of -53 °C indicated that the steel possesses adequate toughness properties. As weldability is one of the criteria for structural applications, this aspect too has been investigated.     

冷却条件对42CrMo钢的组织和性能的影响

研究了冷却条件对42CrMo钢的组织和性能的影响。研究表明：随着冷却速度的增加，42CrMo钢组织变化依次是多边形铁素体组织、针状铁素体组织、上贝氏体和板条马氏体的混合组织。其中，针状铁素体使钢的组织细化、韧性提高。热温度过高，冷却速度快会形成网状铁素体组织，在高温区冷却速度慢会形成块状铁素体组织。这两种组织使钢的力学机械性能降低。     

Effect of Cooling Rate on the Room Temperature Microstructure Following the Intercritical Deformation of Steel S460

The effect of final hot rolling in the intercritical (α+γ) region on microstructure and properties is very specific to the individual processing conditions and the chemical composition of a steel.S460 is a plate steel processed in this way.To reproduce at the laboratory scale,a multi-stage simulation was developed which included a high temperature austenite deformation and an isothermal hold.The effect of the applied cooling rate following intercritical deformation was investigated.At 1K/s (typical industrial cooling) the microstructure was similar to the reference sample,but included an intragranular ferrite fraction.This was due to differences in processing history,and considered to be linked to a larger prior austenite grain size.At an accelerated cooling rate (15K/s),acicular ferrite formed on shear bands within the strained austenite phase.EBSD scans have been completed to provide further information about the microstructures,with band contrast able to identify the pearlite phase at the slowest cooling rate.This is a starting point from which to focus on the ferrite morphologies.