粗轧板坯侧翻变形的数值模拟

针对板带热轧过程中易产生各种边部缺陷的问题,利用有限元法对粗轧可逆道次轧制过程进行了数值模拟,分析了不同立轧和平轧道次中轧件变形的情况,特别是角部金属由侧面逐渐翻转到轧件上表面的变化过程。结果表明,平轧道次轧件主要产生宽展和侧翻,且其角部金属呈拉应力状态,有可能诱发各种缺陷的产生,而立轧道次处于具有修复缺陷的压应力状态,因此优化立轧压下制度是改善带钢边部缺陷的一个重要方法。通过单元的变形过程可跟踪坯料和轧件位置之间的对应关系,这对分析带钢表面缺陷的成因并消除缺陷具有重要意义。     

立辊形状对边角部金属流动的影响规律

以梅钢热轧机组的粗轧板坯边部出现"黑线"为背景,对不同立辊形状的五道次可逆立-平轧制过程进行了数值模拟.结果表明,孔型立辊轧制可更好地抑制双鼓形的产生;在相同的轧制工艺条件下,孔型立辊轧制的翻平量大于平立辊轧制的翻平量;轧制过程中,低温、高应力应变状态的金属在轧件边部的累积最终可能导致轧件边部沿长度方向产生"黑线"缺陷;立轧具有一定的修复微小缺陷的作用,从而改善和提高了带钢的边部质量.     

热轧卷板边部线状缺陷分析与措施

边部线状缺陷是热轧卷板日检常见的缺陷,利用金相显微镜及跟踪工艺生产过程对卷板表面线状缺陷的形成原因进行分析。研究表明,其主要原因是立辊与钢坯边部直接接触,由于粗轧立辊磨损后,与轧件表面产生摩擦力,在随后的轧制过程中造成表面应力撕裂,形成表面线状缺陷。     

1422粗轧带钢板廓形状变化仿真研究

采用有限元的方法建立带钢立轧/平轧的三维模型,对热轧带钢粗轧过程的板廓的变化规律进行了仿真研究,重点分析了各道次轧制后带钢板廓形状和边角的位置变化,以及材质,立辊辊形,立轧压下量等因素对边角位置的影响.研究结论为现场解决热轧带钢表面的边部黑线缺陷问题提供了技术思路,为工厂最终解决此一表面缺陷提供了帮助.     

椭-圆孔型连轧大圆钢三维热力耦合弹塑性有限元分析

采用MSC．Marc三维大变形热力耦合弹塑性有限元软件和接触分析技术，对Φ230mm大圆钢两机架热连轧过程中轧件三维变形进行了有限元仿真，计算了轧件主要力能参数的分布值和极值，以此对轧辊强度、孔型尺寸及相关的轧制工艺参数进行分析，得出采用道次小变形量和快速轧制工艺，有助于减缓热作模具钢轧后端部表面残余应力升高和温度降低，避免表面裂纹的产生。     

超低碳热轧带钢头部分层原因分析

利用光学显微镜和扫描电镜对超低碳热轧带钢头部分层缺陷进行了检验分析。结果表明,该缺陷产生原因是由于连铸坯喷号剂中含有Cu元素,加热后出现渗铜现象,导致连铸坯头部晶界弱化,在后续的轧制过程中造成轧件头部开裂分层。生产中采取了减小粗轧道次变形量、优化中间坯切头量、降低加热温度等技术措施,避免了该缺陷的产生。     

立辊孔型内倒角半径对轧件变形的影响

采用显式动力学有限元方法,对立辊孔型内倒角半径R为30、50、80、110 mm 4种情况下多道次立-平轧制过程进行了模拟.分析了立辊孔型内倒角半径对轧件切头尾量、轧件稳定段轧件边部变形程度的影响.研究发现:既定条件下,第1道次立-平轧制过程中,随内倒角半径的减小头尾不均匀区域长度减少,第2、3道次立-平轧制过程中,随内倒角半径的增加,头尾不均匀变形区域长度道次增加量减少;对比采用R为30 mm的孔型立辊和R为110 mm的孔型立辊轧后轧件的头尾不均匀长度,前者比后者少5.03%;轧件稳定段轧件变形程度随着孔型立辊内倒角半径的增加而减少.     

钢轨万能精轧过程的三维弹塑性有限元模拟

借助有限元分析软件MSC.Marc,采用三维热-机耦合弹塑性有限元模型,对钢轨万能精轧过程进行模拟分析。以UR-EF-UF三机架连轧过程为研究对象,建立变形过程优化模型。将轧件尺寸模拟结果与实验结果进行比较,两者吻合较好,验证了模型的准确性。对轧件变形过程、轧制接触状态、应力应变分布以及速度变化等模拟结果进行了讨论分析,揭示了万能轧机各道次的加工特点和轧件在连轧变形过程的变形规律。     

成形角对楔横轧21-4N合金钢气门心部质量的影响

基于气门二次楔轧制原理,采用DEFORM-3D有限元软件研究了成形角改变时轧件心部应力和应变的变化规律,分析了成形角对楔横轧21-4N合金钢气门心部质量的影响.结果表明:随着成形角的增大,轧件心部的应力状态和应变状态更为合理,有利于防止心部疏松.相应的轧制实验结果验证了这个结果.      

粗轧机多项式短行程控制模型

 短行程控制是粗轧中间坯调宽过程中改善轧件头尾部形状、降低切损量的有效方法,而目前采用较多的折线式短行程控制模型还有待进一步提高。结合热带钢粗轧机组实际工艺条件,采用刚塑性有限元法建立立辊/水平辊连轧过程热力耦合数值计算模型,对粗轧过程头尾部非稳态变形分布进行深入分析,得出中间坯头尾部立辊/水平辊轧制失宽变化规律。基于数值计算结果提出5次多项式短行程控制策略,并建立相应多项式短行程控制模型。通过对比计算结果表明,新建的多项式短行程控制模型具有更好的头尾形状控制能力,提高了热带钢产品成材率。     

From Slab Corner Cracks to Edge‐Defects in Hot Rolled Strip ‐ Experimental and Numerical Investigations

The systematic investigation of the formation of edge defects on hot strips resulting from slab corner cracks generated in continuous casters, affords the development of model‐based concepts for the identification of such initial slab cracks. This enables the reduction of material losses during trimming of defective edges. Utilizing the commercial finite element package Deform‐3D, systematic massive forming simulations of several consecutive flat and edging passes were performed. The main simulation challenges result from the occurrence of different length scale values in the slab and strip models including edge cracks. The numerical results clearly point out the significant morphological changes of the cracks during rolling and afford valuable indications for a deeper understanding of the underlying process details. The results from metal forming simulations coincide very satisfactorily with the unetched cross‐sectional micrographs obtained from an experimental rolling mill. Systematic variation of geometry data enables the identification of the topology of initial slab corner cracks from edge defects detected after hot rolling.     

中厚板边部折叠模拟实验及机理研究

通过对中厚板边部折叠试样的检测分析,对其产生机理和影响因素进行研究.结果显示,中厚板边部折叠现象是板材横轧宽展过程中侧面材料在轧制中受轧辊作用而翻转到板材表面的结果.折叠缺陷处所观察到的微观组织结构,是轧制前板材表面在高温下形成的氧化铁及脱碳层形成的.建立了轧制有限元数值模型,证实折叠缺陷是在轧制过程中由侧面的折叠翻转所造成的.通过实验室实验,得到铸坯边部质量、轧制制度、宽展道次及轧制压下量对中厚板折叠缺陷的影响.实验结果表明横轧宽展导致折叠缺陷的出现,铸坯边部质量对其没有影响,轧制过程中铸坯侧边的折叠经翻平形成表面折叠缺陷,随着横轧展宽的道次及压下量增加,折叠缺陷距边部距离变大.      

取向硅钢冷轧断带问题研究

对取向硅钢冷轧过程出现的断带缺陷进行了跟踪,明确了从起皮到形成孔洞,再到断带的演变过程,采用扫描电镜对翘皮缺陷进行研究,结果表明：翘皮缺陷中主要元素是Fe、Si、Al,与基体一致,另外还有微量的Ca、Mg、K、Na等元素。冷轧起皮、断带主要是由于热轧边裂缺陷遗传而成。热轧过程部分边部掉肉飞溅至热轧板表面被压入,在冷轧过程由于伸长率与基体不一致而起皮剥落。通过降低铸坯加热温度、缩短高温段在炉时间、优化轧制模型,有效抑制了热轧板边裂的产生,从而解决了冷轧断带问题。     

Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

In this study, cracks formed in the edge side of Bi-S–based free-machining steel billets during hot rolling were analyzed in detail, and their formation mechanisms were clarified in relation with microstructure. Particular emphasis was placed on roles of bands of pearlites or C- and Mn-rich regions and complex iron oxides present in the edge side. Pearlite bands in the cracked region were considerably bent to the surface, while those in the noncracked region were parallel to the surface. This was because the alignment direction of pearlite bands was irregularly deviated up to 45 deg from the normal direction parallel to the surface, while the billet was rolled and rotated at 90 deg in the same direction between rolling passes. On the edge side, where pearlite bands were bent, iron oxides intruded deeply into the interior along pearlite bands, which worked as stress concentration sites during hot rolling and, consequently, main causes of the crack initiation in the rolled billet. On the surface of the wire rod rolled from the cracked billet, a few scabs were found when some protrusions were folded during hot rolling. In order to prevent the cracking in billets and scab formation in wire rods, (1) the increase of rolling passes and the decrease of reduction ratio for homogeneous rolling of billets and (2) the reduction in sulfur content for minimizing the formation and intrusion of complex iron oxides were suggested.     

Evolution of Surface Transversal Crack in Intermediate Slabs during Hot Rolling Deformation

In the continuous casting of steels,surface transversal cracks are often found.These defects may severely influence the final quality of the products.The evolution of transversal V-shaped cracks with different depth on the surface of a continuously cast steel slab during hot rolling was studied.The artificial V-shaped cracks were made on the surface.The rolling process parameters from an industrial rolling mill have been used as a reference.The specimens of rolled workpiece in intermediate slabs were obtained after different rolling passes.The morphology of surface crack and microstructure evolution in the rolling process were investigated by optical microscopy.The results show that the depth of surface transversal crack gradually decreased with the increase of rolling passes.The grain size of ferrite and pearlite on the sample surface also gradually reduced.The microstructures around cracks with the different depth are almost identical,without direct correlation with the initial crack depth.     

TA15钛合金不等厚L型材热轧有限元模拟

利用有限元分析软件Deform-3D建立TA15钛合金不等厚L型材的轧制模型,研究各道次轧件温度场、应变场、金属流动速度的变化规律。模拟结果表明,轧制过程中产生的大量变形热会导致轧件温度升高,且K1~K3道次薄壁侧温度明显高于厚壁侧。在K6和K7道次轧制时,轧件温度过低,需回炉补温。轧件的应变随轧制道次的增加而增加,薄壁侧应变大于厚壁侧。轧件各部位温度及变形量的变化会影响轧件金属流动速度,在K1道次轧制时,厚壁侧与薄壁侧的流动速度差较大,导致轧件产生弯曲变形。采用楔形坯料可有效避免轧件出现变形弯曲。     

热连轧无缝钢管内表面凹坑、孔洞缺陷的形成分析

介绍了热连轧无缝钢管内表面凹坑、孔洞缺陷的基本形式和分布规律。通过轧制差厚铅板实验说明规律性的热连轧无缝钢管内表面凹坑、孔洞缺陷的形成主要是由于轧件不均匀变形所致，并提出避免这两种缺陷出现的基本思路。     

CSP板卷及冷轧镀锌板表面缺陷分析

为研究CSP及其后续产品的表面质量,对马钢CSP、冷轧和镀锌生产线投产以来出现的主要表面缺陷进行分析,研究结果表明:夹杂类缺陷、边裂和氧化铁皮压入是热轧板卷的主要缺陷,这些缺陷将不同程度地遗传到后续产品.产生表面缺陷的主要原因有钢水质量、连铸和轧制工艺、除鳞工艺和后续设备自身状况等,分析认为提高钢水和连铸坯质量是消除热轧板卷和后续产品表面缺陷的关键.     

冷轧板常见表面缺陷特征及成因分析

通过生产实践和检验,分析认为冷轧板常见表面缺陷包括原料缺陷和冷轧缺陷两大类,原料缺陷源于炼钢和热轧。原料缺陷如果控制不当,会遗传到冷轧成品板上,冷轧缺陷宏观易于辨识。提高冷轧板表面质量需要冶炼、连铸、热轧、冷轧各工序协调配合。