硬质合金辊环轧制螺纹钢失效原因的实验研究

本文研究了硬质合金辊环轧制牌号HRB400螺纹钢筋时产生裂纹的原因。通过选用两种不同硬质合金辊环牌号YGR55和YGR60分别轧制规格Φ6 mm、Φ8 mm和Φ12 mm、牌号HRB400螺纹钢筋,并使用两种不同成品前孔型进行了轧制对比实验。结果表明:硬质合金辊环轧制牌号HRB400螺纹钢筋槽内产生裂纹的根本原因是螺纹钢轧制过程中成品前孔设计不当造成成品孔槽内轧制压力过大,在硬质合金辊环单槽轧制量达不到规定吨位情况下提前失效。同时验证了硬质合金高线轧制螺纹钢的首选牌号为YGR55。     

中厚板轧制过程的数值模拟

以L245级管线钢材料的热物性参数(密度、泊松比、杨氏模量、热膨胀系数、热导率和比热)和热模拟压缩实验获得的高温变形时应力—应变曲线等试验数据为基础,在MSC.Marc软件中建立了该钢种材料数据库,并建立了中厚板多道次轧制过程的二维有限元模型。以铸坯厚度为220mm、成品厚度为25.4mm的热轧过程为例,通过对轧件与轧辊接触面间换热系数采用取不同常数值的方法,并依据其生产时所采集的各道次相关工艺参数,对该轧件全道次热轧过程进行了数值模拟,将各道次的轧制力计算值与实测值进行了分析比较,确定了轧件与轧辊间接触面换热系数的最佳值。利用本文模型对厚度为180mm的轧件单道次轧制过程进行了数值模拟,研究了不同变形工艺参数(轧制温度、道次压下率和轧制速度)对变形区等效应变和等效应力的影响。结果表明,在轧机设备能力及生产现场条件允许时,高温粗轧阶段纵轧道次可采用低速大压下率进行轧制成形,使变形较充分地向轧件芯部渗透,从而使钢板获得细小均匀的晶粒组织,有效改善钢板的强韧性能。     

小型H型钢全轧程数值模拟及斜轧孔型轧制力模型研究

本文运用有限元方法对HW100mm×100mm、HW150mm×150mm两种规格小型H型钢全轧程进行了三维热力耦合数值模拟,介绍了小型H型钢轧制的有限元模型和模拟参数设置。针对模拟结果,详细分析了典型道次轧件的金属流动状况、有效塑性应变和温度变化规律,并对数值模拟结果进行了验证。本文还建立了小型H型钢斜轧孔型的轧制力模型,计算了各道次轧制力解析结果,并将轧制力解析结果、数值模拟结果与轧机实际负荷电流趋势进行了对比,规律性吻合较好。     

GH4169异型材单轧槽轧制工艺

采用轧制工艺生产GH4169合金异型材,结合实验条件,基于有限元模拟软件建立了单轧槽少道次轧制过程的三维刚塑性有限元模型。采用异型坯作为坯料,分析了轧制过程中孔型充满度、变形温度、等效应变和等效应力的分布情况。模拟结果表明,采用Φ160 mm×200 mm轧机时,初轧温度为1070℃,断面收缩率为45%,单轧槽两道次轧制成形,孔型充满度良好,等效应变约为0.3~1.4。结合模拟结果,在轧机上进行了热轧实验,轧件厚度满足尺寸要求,宽度比成品小2 mm,没有发生晶粒细化。这主要是由于多火次、多次数轧制,使得加热引起的晶粒长大程度大于小变形量引起的晶粒细化程度,使得晶粒未细化,宽度不够。     

Ti-6Al-4V合金多道次热轧过程有限元模拟与实验

采用热力耦合方法对Ti-6Al-4V合金进行了多道次热轧模拟,研究了不同道次温度和等效塑性应变的分布特点。模拟结果表明,轧制过程表面温度低于心部的温度,随轧制道次的增加,表面温度整体表现为降低过程,中心温度整体表现为先升高后降低过程。中心位置比表面位置的等效塑性应变大,表面位置与中心位置的等效塑性应变均随变形道次的增加而增大。结果表明,随着轧制道次的增加,中心显微组织变形大于表面。中心区域组织易于发生动态球化。     

带钢热连轧过程轧制力三维有限元模拟

在现代计算机控制的带钢生产中,轧制力的设定极其重要.根据宝钢轧制力模型和现场实测数据,结合热连轧过程中带钢三维变形和热力耦合的特点,应用DEFORM-3D软件建立了带钢热连轧前两个道次的有限元模型,模拟了热连轧过程中两个道次的轧制力变化,并与宝钢模型计算值和实测值进行了对比.结果表明,有限元法计算的轧制力与现场实测数据接近,两者误差在5.0%以内,同时有限元法的计算精度高于宝钢轧制力模型,特别是在第一道次,轧制力计算精度高出4.0%,该模拟为现场轧制工艺参数的调整优化提供了重要的参考价值.     

Texture Evolution,Formability and Ridging Resistance of a Sn-bearing Ferritic Stainless Steel Under Different Hot Band Annealing Temperatures

The microstructure, texture evolution and spatial orientation distribution during cold rolling and the subsequent annealing as well as formability and ridging of a Sn-bearing ferritic stainless steel under different hot band annealing temperatures were investigated. The four hot bands with annealing temperatures of 900, 950, 1000 and 1050 °C were all cold-rolled to 80% reductions and then were annealed at the same temperature of 900 °C. The results show that optimizing hot band annealing process is benefi cial to reduce the amount of {001} 110 grains and weaken the texture intensity, and thus, to reduce ridging and improve formability. In the present study, the fi nal sheets with hot band annealing temperature of 900 °C possess small and inhomogeneous grains with a large amount of {001} 110 orientations, which deteriorates the formability and increases the ridging. In comparison, the fi nal sheets with hot band annealing temperature of 950 °C are comprised of uniform and equiaxed 111//ND(ND: normal direction) recrystallized grains with a high texture intensity favorable for the improvement in r value and surface quality. However, when hot band annealing temperature further increases to 1000 and 1050 °C, it shows a sharp decrease in r value and a remarkable increase in ridging as a result of a reduction in γ-fi ber texture intensity and an increase in grain size in the fi nal sheets. Suitable controlling and optimizing hot band annealing process is essential to improve the formability and reduce the ridging.     

Influence of Finish Rolling Temperature on Microstructure and Mechanical Properties of a 19Cr1.5Mo0.5W Ferritic Stainless Steel

A 444-type heat-resistant ferritic stainless steel containing 0.05 wt% Ce(rare earth element) and 2 wt%(Mo+W) was adopted as an experimental material to study the effect of finish rolling temperature on microstructure and texture evolution as well as on mechanical properties and formability.The rolling processes contain hot rolling at two different finish rolling temperatures(860℃ and 770℃) and annealing,cold rolling and subsequent annealing.It was found that the microstructures after hot rolling and annealing could be refined by lowering finish rolling temperature.The resultant microstructures after cold rolling and annealing were hereditarily refined.Lowering finish rolling temperature can weaken α-fiber texture in hotrolled or cold-rolled ferritic stainless steel strip,while γ-fiber texture in the final product was homogeneously strengthened.Additionally,enhanced mechanical property and formability in terms of strength and average plastic strain ratio could be obtained via decreasing finish rolling temperature.     

Microstructural Evolution,Mechanical Properties and Thermal Stability of Gradient Structured Pure Nickel

The microstructural evolution of pure nickel treated by deep rolling(DR) technique with different indent depths was investigated by means of optical microscopy and transmission electron microscopy.The surface roughness, hardness and residual stress distribution along the depth from surface were measured.Moreover, the DR-treated sample was annealed at temperatures from 300 to 700 ℃ for 2 h.The results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR process.With increasing indent depth of the DR, the gradient microhardness on the cross section of sample significantly increases, the maximum compressive residual stress decreases, and the affecting region of residual stress increases.The results of thermal stability depict that the microstructure can be stable as temperature up to 300 ℃, and the abnormal grain growth and annealing twins are observed at 600 ℃.     

采用小异型坯生产大规格H型钢的技术研究

介绍了首钢长钢轧钢厂采用等宽的连铸异型坯(430mm×300mm×85mm×80mm)开发轧制H300mm×300mm×10mm×15mm规格H型钢的过程。为了使成品的翼缘宽度能够达到300mm,在开坯机孔型中增加了较大的凸度,在减小对翼缘压下的同时增加了对腹板的压下,以利于万能轧机轧制时翼缘的宽展。此外,还制定严谨的试轧方案,针对试轧制中出现的问题、缺陷,特别是开坯机孔型中增加了较大的凸度后,轧制时H型钢圆角部位易出现折叠的问题,重新优化了开坯机孔型、万能孔型及轧制工艺,消除了折叠缺陷,产品力学性能满足标准要求。     

全浮动芯棒连轧管机孔型对钢种适应性的模拟研究

应用MSC.SuperForm有限元仿真软件,基于现场生产工艺,模拟了Φ140 mm全浮动芯棒连轧管机Φ195 mm孔型的钢管连轧过程,研究了连轧过程中C22和超级13Cr两种钢的金属流动、轧制力等规律性.结果表明：与C22相比较,超级13Cr更易产生宽展,金属横向流动倾向性更大,所以在高合金管轧制用孔型设计时,需特别注意金属过充倾向;超级13Cr的轧制力较C22增大60％以上,机架、轧辊的弹性变形量更大,在轧辊辊缝预调时,应加大超级13Cr的预压靠量,在孔型设计时,也需考虑其弹性变形量,以补偿高合金钢轧制时大轧制力引起的机架、轧辊的弹性变形量的影响.     

Φ325mm Assel轧管机组工艺技术的集成创新与应用

分析了传统Assel轧管机组在生产时存在的问题,介绍了Φ325 mm Assel轧管机组工艺技术的创新情况,主要体现在轧管工艺路线、芯棒预穿和小循环、轧制方式等方面,并与传统工艺生产产品的质量进行对比。应用结果表明:该创新工艺解决了传统生产工艺中的弊端,可节约生产成本约30%,且产品质量优良。     

高速线材减定径轧制变形特点与热模拟参数研究

为分析高速线材减定径轧制的变形特点,利用有限元模拟方法研究了四道次减定径轧制过程。轧制产品规格为φ12 mm的圆钢,孔型系统为椭圆-圆-椭圆-圆。研究表明,四道次减定径轧制轧件最大累积等效塑性应变达1.890,最大温升达76.7℃,轧件平均变形速度大于429.4 s-1。限于热模拟条件的限制,仅能对减定径轧制轧件的变形程度进行准确模拟。     

非调质钢F40MnV三辊楔横轧的实验研究

针对非调质钢F40MnV空心轴类件楔横轧成形问题,为获得最佳轧制与冷却工艺制度,在三辊楔横轧机上开展了轧制与冷却实验研究。利用正交法制定实验过程工艺参数,并将带有热电偶的试件进行轧制。轧后采用水冷,水冷加空冷,风冷,空冷4种方式进行冷却,得到相应的温度变化曲线。基于实验结果,采用金相分析和性能实验手段研究了温度、断面减缩率和冷却介质对F40MnV钢轧后冷态力学性能的影响。结果表明采用水冷加空冷、断面减缩率35%、轧制温度为950℃时的成形工艺可得到较为优良的力学性能。     

高铌钛铝基合金板材的高温包套轧制

采用高温包套轧制方法在普通轧钢轧机上首次成功的轧制出厚度为2．6mm的高铌钛铝基合金板材。合金在轧制中的总变形量达到70％。板材表面质量良好，显微组织观察表明合金在轧制中发生了再结晶，但是变形后的组织并没有由于再结晶而明显细化。这主要是由于合金在轧制回炉保温和轧后随炉冷却过程中，长时间停留在高温区间，导致了合金晶粒的长大。     

钢管热连轧过程横断面壁厚变化的三维有限元模拟

针对20号钢Φ119.0mm×9.25mm规格全浮动芯棒无缝钢管8机架连轧过程进行了有限元模拟仿真分析,得到了热连轧管各机架出口等效塑性应变以及荒管壁厚变化情况,分析了轧制力和芯棒力的变化特点。研究表明,连轧管减壁量和外直径变化主要集中于开始第1~第6个机架,在第7、第8机架减壁作用很小,最终荒管壁厚均匀,且形状圆整。稳定连轧阶段的轧制力依轧制顺序呈递减趋势,第7、第8机架轧制力很小;同时芯棒力大于各机架轧制力,钢管内壁承受的作用力和塑性应变较大,应对芯棒表面进行合理润滑。模拟得到的壁厚、外径及轧制压力与实测结果吻合较好。     

终轧工艺对AM50镁合金轧板力学性能和织构特征的影响

采用不同的轧辊温度和速率制备AM50镁合金轧板,研究终轧工艺对镁板力学性能和织构特征的影响。研究表明：在轧辊温度为200°C和轧辊速率为5 m/min条件下制备的镁板的强度（极限抗拉强度：295 MPa;屈服强度：224 MPa）和伸长率（22.9%）之间达到较优组合;在热轧过程中,轧板的屈服强度主要取决于轧制温度,而织构强度则对轧辊速率更为敏感;提高轧制温度或轧辊速率均可改善AM50镁合金板材力学性能的各性异性。     

Microstructure and Texture Evolution of Mg-14Gd-0.5Zr Alloy during Rolling and Annealing under Different Temperatures

Mg alloys containing high rare earth (RE) elements are hard to be rolled due to their low ductility and high strength at low temperatures. Therefore, rolling at high temperatures is necessary for these alloys. In this work, a Mg-14Gd-0.5Zr (wt%) alloy was rolled one pass with 40% reduction at high temperatures over 450 °C. The effects of rolling temperature on the microstructure and dynamic recrystallization behavior were analyzed in detail by the electron backscattered diffraction (EBSD) method. The results revealed that the alloy shows good rollability at high temperature due to the activity of non-basal dislocations and twins. However, dynamic recrystallization is difficult to take place because of the easy activation of multi-slip system and thus more accumulated strain energy. However, Gd segregation was observed at the grain boundary and it is inferred that the segregation can partially enhance the dynamic recrystallization ratio. Statically recrystallized grains with large size took place after short-term inter-pass annealing treatment ranging from 450 °C to 500 °C, and formed basal texture. The result suggests that the formation of basal texture during short-term annealing treatment was attributed to the growth of dynamic recrystallized grains caused by weakened Gd segregation.     

宝钢2050粗轧带钢宽展规律仿真研究

采用大型刚塑性有限元软件建立立轧/平轧的三维热应力耦合轧制模型,并将其应用到宝钢2050粗轧机组仿真研究中.选取宝钢轧制带钢的现场实际参数进行模拟计算,得出的粗轧出口宽度值与实测值吻合良好,充分验证了模型的有效性.为了解决宝钢2050粗轧机组宽度难以控制的问题,本文对现场各种轧制工艺的宽展进行了仿真计算,并给出了自然宽展、纯狗骨宽展、综合宽展的分布规律.     

φ10mm带肋钢筋四线切分轧制 技术的开发与应用

介绍了φ10mm热轧带肋钢筋四线切分工艺孔型系统的设计、导卫系统的选择以及轧制过程中调整 操作要点。同时,介绍了山东石横特钢集团轧钢厂φ10mm带肋钢筋四线切分轧制的技术经济指标,经济效益显著。