S元素含量对IF钢热轧析出物的影响

在Gleeble-3500热模拟试验机上,利用模拟轧制和卷取方法研究了不同S含量Ti-IF钢热轧成品第二相粒子的析出行为。试验结果表明,Ti-IF钢的析出物类型随着S含量的增加出现明显变化,当S质量分数为140×10^-6时,大尺寸析出物中出现TiS单独析出情况,同时随着钢中S含量的增加,大尺寸析出物(200 nm以上)逐渐增多,主要析出物类型为TiS和Ti₄C₂S₂;而小尺寸析出物(20 nm以下)逐渐减少,主要析出物类型为TiC。结合钢种的热力学分析可知,当S含量增加时,基体内固溶的C原子,首先满足Ti₄C₂S₂形成的需要,其次再以TiC的形式析出,可见S元素对固定间隙C原子有明显作用,由此提出钢种设计时S元素含量按下限设定的理论。     

Microstructural changes of nanocrystalline nickel during cold rolling

The microstructural changes of electrodeposited nanocrystalline Ni with an initial grain size of about ∼30–40 nm during cold rolling up to 76% thickness reduction have been studied using X-ray diffraction and transmission electron microscopy. In response to the cold deformation processing we observed significant changes in the scale and morphology of grains, defect content, as well as of crystallographic texture. Our experimental findings for nanocrystalline Ni are directly compared to the behavior of coarse-grained Ni. The role of the grain scale reduction to the nanometer regime is discussed with respect to the microstructural changes.     

Microstructural evolution during large strain hot rolling of an AM60 Mg alloy

Significant grain refinement can be achieved using a simple processing method such as large strain rolling (LSR) in an AM60 alloy. The stabilization during rolling of a double-peak (slightly off-basal) texture is attributed to increasing non-basal 〈c+a〉 slip activity. There is evidence that grain refinement takes place via continuous dynamic recrystallization (CDRX).     

温滚压对H13钢疲劳寿命的影响研究

温滚压是一种将材料加热到再结晶温度之下某一温度并进行滚压的方法。与普通滚压相比,在某些温度下的温滚压可以更好地提高疲劳寿命。本文针对一种常用的热作模具钢——H13钢开展了温滚压的系列实验研究,在搭建温滚压实验平台的基础上,对未滚压工件和在不同温度下滚压的工件进行了疲劳实验。结果表明,与室温滚压相比,200℃下的温滚压能够进一步提升H13钢的疲劳寿命;而350℃时的温滚压在低周疲劳区域起到了优于室温滚压的延寿效果,但在高周疲劳区域延寿效果减弱,随着循环应力水平降低其疲劳寿命甚至会低于未滚压工件。最后进一步分析了温滚压提升疲劳寿命的机理。     

压下率对铁素体区轧制高强IF钢组织及性能的影响

通过拉伸试验检测力学性能,用金相显微镜观察高强IF钢热轧态及退火态的纤维组织,并用透射电镜观察试验钢中的析出相粒子.在640℃终轧温度下,铁素体区轧制总压下率由60%升高到81%,高强热轧IF钢板的屈服强度为150～180 MPa,抗拉强度为312～321 MPa,屈强比为0.48～0.56,总伸长率为26.4%～31.2%,元值为0.22～0.23,而r值则由1.41降低到1.01,|Δr|则由0.625降低到0.133.结果表明.轧制总压下率对热轧高强IF钢的屈服强度、抗拉强度、总伸长率以及n值影响较小,但是对r值和平面各向异性值△r的影响非常大.铁素体区轧制总压下率的增大使得高强IF钢热轧板中动态再结晶的驱动力增大,发生动态再结晶晶粒的数目增多,从而导致形变织构的减弱和后续退火再结晶驱动力的减小.同时,随着铁素体区轧制总压下率的增大,高强IF钢退火再结晶程度降低以及析出的粒子变细.     

IF钢铁素体区轧制对带钢最终性能的影响

采用铁素体区轧制工艺能够大大提高IF钢冷、热轧带钢的深冲性能。本研究通过工业试验验证了铁素体区轧制工艺的可行性。试制带钢组织、织构及性能检测的结果表明：热轧带钢1/4厚度处和芯部初步形成了γ织构,连续退火冷轧带钢中形成了强烈的γ织构,冷轧带钢的伸长率达到50%以上,r值达到3.15,具有优良的成形性能。     

IF钢炼钢过程洁净度控制生产实践

涟钢通过优化转炉底吹、下渣控制、顶渣改质技术、缩短RH炉处理周期、严格控制RH炉吹氧量、稳定脱碳终点氧含量、提高一次加铝命中率、RH炉破真空到开浇镇静时间大于20 min,确保了夹杂物有充分的上浮时间,使得中间包钢水全氧低于2.5×10-5比例大于90%,IF钢夹杂降等量从2011年1.41%降低到目前0.15%,铝耗从2011年1.86 kg/t降低到目前的1.05 kg/t,钢水洁净度得到进一步改善。     

热轧IF钢溢出类毛刺产生机理及控制研究

IF钢在热轧过程中容易产生边部金属溢出类毛刺,对冷轧生产及成材率有较大影响。介绍了IF钢热轧卷边部金属溢出类毛刺形貌,分析了其产生机理及影响因素,并对板坯加热制度、轧线用水制度、粗轧道次等进行了优化控制,取得了毛刺发生率显著减少的较好效果。     

Analysis of texture and R value variations in asymmetric rolling of IF steel

Asymmetric rolling (ASR) is a potential process to reach better grain refinement than in conventional rolling, thus, can lead to better mechanical properties. It is not known, however, how the introduction of a shear component will change the ideal orientations of the textures, and consequently, the evolution of plastic anisotropy. To understand the effect of the added shear on texture evolution in ASR, a stability analysis is carried out in orientation space and the variations in the position and strength of the ideal orientations are analysed as a function of the shear component. Then, modelling of R values is presented for various cases. On that basis, it is shown that there is an upper limit for the shear component in asymmetric rolling that still retains the 〈1 1 1〉 || ND fibre (ND: direction normal to the sheet) which is good for formability. It is also found that better persistence of the ND fibre can be obtained by cyclically alternating the shear component. The theoretical results are well supported by comparison to experimental evidences.     

IF钢退火过程中再结晶行为的EBSD表征

借助EBSD等技术研究了从冷轧到退火过程中IF钢中铁素体再结晶晶粒的取向演变。研究结果表明,从冷轧到退火过程中,铁素体晶粒取向向着平行于法向的[111]晶粒演变,而平行于法向的[100]晶粒逐渐消失;在冷轧变形过程中,铁素体晶粒的晶体取向决定着发生滑移变形的难易程度,与[100]晶粒相比,[111]晶粒更易于发生滑移变形,并在晶粒内部积累大量的位错,储存了大量的应变能,在随后的退火过程中,应变能较高的[111]晶粒优先形核并长大,优先发生再结晶,而应变能较低的[100]晶粒的再结晶受到阻碍。随着退火温度的升高,γ织构([111]//ND)明显增强,其织构组分(111)[112]尤为明显。     

温轧温度对中碳Cr-Mo钢组织性能的影响

通过SEM、EBSD和拉伸试验研究了温轧温度对中碳Cr-Mo钢组织演变和力学性能的影响。结果表明:较高温轧温度有利于Cr-Mo钢组织的均匀分布,当轧制温度从500 ℃增加到600 ℃时,铁素体晶粒尺寸由0.424 μm增加到0.490 μm,晶粒尺寸差别不断减小,屈服强度由1380 MPa下降至1062 MPa,在550 ℃轧制试验钢的塑性最好,强塑积最高,为5816 MPa·%。     

温轧温度对中碳钢组织与力学性能的影响

采用透射电镜(TEM)、扫描电镜(SEM)、室温拉伸等手段,研究了650~730 ℃温轧温度对0.46%C中碳钢的组织演变及力学性能的影响。结果表明,经90%的轧制变形,试验钢铁素体晶内引入大量位错,渗碳体片层产生应力集中导致层片状渗碳体弯曲、扭折、碎化为颗粒状。随着温轧温度的降低,位错增殖明显,渗碳体球化率增加,分布越来越均匀,抗拉强度和伸长率整体上升。当温轧温度为650 ℃时,渗碳体球化最好,抗拉强度877 MPa,断后伸长率16.0%,综合力学性能最好。拉伸断口结果表明,随着温轧温度的降低,试验钢的断裂机制由韧-脆混合断裂转变为韧性断裂,塑性提高。     

高碳钢棒件温楔横轧成形过程的有限元数值模拟

在有限元软件Deform-3D平台上,基于三维刚塑性大变形热/力耦合有限元理论,对一种高碳钢棒件的温楔横轧成形过程进行了数值模拟。给出了轧制过程中温度、应变及应变速率各场量的分布,并用实际温楔横轧实验进行了验证,模拟结果与实验结果吻合较好。     

板带轧制技术的最新进展

主要介绍了冷、热轧板带生产技术的最新进展。     

综述板带轧制技术的最新进展

主要介绍了冷、热轧板带生产技术的最新进展。     

Effect of roll speed ratio on deformation characteristics of IF steel subjected to differential speed rolling

The paper investigates the effect of the roll speed ratio on the deformation characteristics of interstitial free (IF) steel processed by the differential speed rolling (DSR) technique. An intense plastic strain induced by a single DSR with various roll speed ratios ranging from 1:1 to 1:4 for the lower and upper rolls was successfully imparted to the samples, resulting in the formation of fine elongated ferrite grains as the roll speed ratio increased. Observations of the preferred orientation using electron back-scattered diffraction and transmission electron microscopy revealed that the {110} slip was readily activated as the dominant deformation mode in order to accommodate the intense plastic strain imposed by the DSR. In addition, the microhardness values of the IF steel sample deformed via DSR under a roll speed ratio of 1:4 increased, and this is discussed on basis of the frictional force between the roll and the sample during DSR deformation.     

Microstructural evolution of Au-Sn solder prepared by laminate rolling during annealing process

The microstructural evolution and interfacial reaction of the Au/Sn/Au/Sn/Au/Sn/Au couples were investigated during annealing at 453,523,and 543 K for up to 240 h.The Au/Sn combination formed a rapid diffusion system.Even in rolled Au-Sn solder,three phases,such as AuSn,AuSn2,and AuSn4,were formed.After initial annealing at 453 K,the diffusion layers of AuSn,AuSn2,and AuSn4,which were formed after rolling,expanded gradually and then fully transformed into ζ phase(containing Sn from 10% to 18.5%,mole fraction) and δ(AuSn) phase.As a whole,the microstructure of the couple was stable during annealing at 453 K.The solid-state interfacial reaction was much faster at 523 K than at 453 K.After annealing at 523 K for 6 h,the AuSn,AuSn2,and AuSn4 were fully transformed into the ζ phase and δ phase(AuSn) .In spite of the prolonged annealing time for up to 240 h,no significant change of the interfacial microstructure occurred,and the microstructure of the couple was stable during annealing at 523 K.When annealing at 543 K,however,the interfacial of Au/Sn was transformed into solid-liquid state,and the whole couple formed a eutectic structure rapidly,causing the solder to be brittle.The study results clearly demonstrate that the service temperature of the Au-Sn solder should be lower than 543 K.     

Texture and microstructure development in cold-rolled interstitial free (IF) steel sheet during electric field annealing

The effects of electric field annealing on the development of recrystallization texture and microstructure in a cold-rolled IF steel sheet were studied by means of ODF analysis and optical microscopy. Results showed that the applied external electric field might retard recrystallization, and enhance the γ-fiber recrystallization texture that is beneficial to the deep-drawability.     

The sticking behavior of an ultra purified ferritic stainless steel during hot strip rolling

During hot rolling of ferritic stainless steels (FSSs), sticking can cause severe surface defects both on work rolls and strips especially for ultra purified FSSs with the total amount of carbon and nitrogen being less than 150 ppm. In the present paper, high temperature oxidization behavior of the ultra purified FSSs was characterized. A new experimental method was invented to simulate the sticking behavior of ultra purified 21%Cr FSS, by which specially designed specimens were hot compressed with different processing parameters to simulate hot strip rolling process. The specimens were surface conditioned prior to the simulation test, either by mechanically polishing or by pre-oxidization to form oxide scales with certain thickness. Observation on the cross-section of sticky regions indicated that cracks had been formed by cyclic heating and cooling during hot deformation had been acting as nucleation sites for sticking particles. The results indicated that oxide scale could avoid the direct contact between roll surfaces and rolled materials to help reducing the sticking occurrence. The temperature region for easy sticking occurrence in the ultra purified 21%Cr FSS has been measured to be from 900 to 1100 °C, which is enlarged as compared to other plain FSSs. The tendency for sticking occurrence decreased with increasing strain rate and decreasing the hammer or work roll surface roughness.