Volume-averaged modeling of multiphase solidification with equiaxed crystal sedimentation in a steel ingot

Macrosegregation is a critical factor that limits the mechanical properties of materials.The impact of equiaxed crystal sedimentation on macrosegregation has been extensively studied,as it plays a significant role in determining the distribution of alloying elements and impurities within a material.To improve macrosegregation in steel connecting shafts,a multiphase solidification model that couples melt flow,heat transfer,microstructure evolution,and solute transport was established based on the volume-averaged Eulerian-Eulerian approach.In this model,the effects of liquid phase,equiaxed crystals,columnar dendrites,and columnar-to-equiaxed transition(CET)during solidification and evolution of microstructure can be considered simultaneously.The sedimentation of equiaxed crystals contributes to negative macrosegregation,where regions between columnar dendrites and equiaxed crystals undergo significant A-type positive macrosegregation due to the CET.Additionally,noticeable positive macrosegregation occurs in the area of final solidification in the ingot.The improvement in macrosegregation is beneficial for enhancing the mechanical properties of connecting shafts.To mitigate the thermal convection of molten steel resulting from excessive superheating,reducing the superheating during casting without employing external fields or altering the design of the ingot mold is indeed an effective approach to control macrosegregation.

Mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding

This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum,and the tensile specimens fractured at the matrix after exceeding 1 Pa.Non-equilibrium grain boundaries were formed at the hot-rolled interface,and a large amount of Mg_(2)Si particles were linearly precipitated along the interfacial grain boundaries(IGBs).During subsequent heat treatment,Mg_(2)Si particles dissolved back into the matrix,and Al_(2)O_(3) film remaining at the interface eventually evolved into MgO.In addition,the local IGBs underwent staged elimination during HRB,which facilitated the interface healing due to the fusion of grains at the interface.This process was achieved by the dissociation,emission,and annihilation of dislocations on the IGBs.

Characterization of W80Cu20 alloy sheet prepared by hot-rolling

Multi-pass hot-rolling technique was used to fabricate W80Cu20 alloy,and its properties were characterized in this paper.Results show that the W-Cu alloy sheets with a thickness of 0.5 mm and a relative density of99.87%can be successfully made using this new technique at 800℃.In hot-rolling process,Cu phases are closely surrounded by W particles under the rolling stress to form a network microstructure,thus making significant increase in electrical and thermal conductivity up to53.00%and 24.44%,respectively.Transverse and longitudinal hardness of the W–Cu sheets significantly increase due to the enhanced densification and deformation strength.Similar to that of the raw materials,three fracture types were observed in the hot-rolled materials,i.e.,ductile fracture of Cu binding phases,trans-granular fracture of W phases,and W–W interfacial fracture.

Numerical simulation on microstructural evolution during multipass hot-rolling of aluminum alloys

Numerical simulation on microstructural evolution during multipass hot rolling of aluminum alloys was performed by using DEFORM TM software and incorporating Zener Hollomon parameter Z . The distributions of equivalent stress, equivalent strain, equivalent strain rate and temperature, as well as the distribution of recrystallization fraction through the thickness of deformed specimen during multipass hot rolling of 5182 aluminum alloy, were all calculated. The results agree well with the metallographic examination of the deformed specimen on Gleeble 1500. [

Scheduling problem for hot-rolling seamless steel tube production

Taking the seamless tube plant of Baoshan Iron & Steel Complex in China as the background,we analyze the characters of hot rolling seamless steel tube:multi varieties,low volume,complicated production process,flexible production routes.Then integrated scheduling problem for hot rolling seamless steel tube production is studied,which covers two key points;order-grouping problem and solution method for flowshop/jobshop scheduling problem.On the basis of these two problems,integrated scheduling decision system is developed.The design idea,function flow sheet,data processing method,and functional module of visualized human-computer interactive scheduling system implemented in seamless steel tube plant of Shanghai Baoshan Iron & Steel Complex are described into detail.Compared with manual system,the performance of system shows the applicability and superiority in several criteria.

Optimization technology of scheduling for hot-rolling mill

To establish the rolling plan of cold-rolling flattening set is very complicated,it is restrained by several constraints of rolling schedule.Operator's subjective and other human factors also affect the rationality of plan arrangement seriously.Its result causes many abuses such as overusing transition strip,high-frequent roller switching,no-fully utilization of rollers,low arrangement rate of the plan.Therefore,we have initially developed a practical optimization model of rolling plan and schedule,which could be established and optimized by computer automatically,and a dynamic alignment module which have friendly UI according to the experience of operators.They have greatly enhanced the system usability.This system takes full advantage of relationship between the roller roughness and the rolling weight,reasonably arranges rolling based on different roughness demand,effectively enhances the use factor of roller and the smooth quality of steel string coil. A practical and effective scheduling optimization algorithm and rolling scheduling optimization applications system was developed based on the study of mixed hot rolling scheduling optimization model of carbon steel,stainless steel,stainless steel and carbon steel cross-rolling.The online application indicates that the model and algorithm is designed reasonable,practical and effective.This model system can significantly improve the scheduling efficiency and quality and it's also very positive in reducing heating energy consumption,enhancing the volume of units rolling plan,and optimizing the production of hot-rolled unit organization and planning and scheduling.

Deep learning for predictive mechanical properties of hot-rolled strip in complex manufacturing systems

Higher requirements for the accuracy of relevant models are put throughout the transformation and upgrade of the iron and steel sector to intelligent production.It has been difficult to meet the needs of the field with the usual prediction model of mechanical properties of hotrolled strip.Insufficient data and difficult parameter adjustment limit deep learning models based on multi-layer networks in practical applications;besides,the limited discrete process parameters used make it impossible to effectively depict the actual strip processing process.In order to solve these problems,this research proposed a new sampling approach for mechanical characteristics input data of hot-rolled strip based on the multi-grained cascade forest(gcForest)framework.According to the characteristics of complex process flow and abnormal sensitivity of process path and parameters to product quality in the hot-rolled strip production,a three-dimensional continuous time series process data sampling method based on time-temperature-deformation was designed.The basic information of strip steel(chemical composition and typical process parameters)is fused with the local process information collected by multi-grained scanning,so that the next link’s input has both local and global features.Furthermore,in the multi-grained scanning structure,a sub sampling scheme with a variable window was designed,so that input data with different dimensions can get output characteristics of the same dimension after passing through the multi-grained scanning structure,allowing the cascade forest structure to be trained normally.Finally,actual production data of three steel grades was used to conduct the experimental evaluation.The results revealed that the gcForest-based mechanical property prediction model outperforms the competition in terms of comprehensive performance,ease of parameter adjustment,and ability to sustain high prediction accuracy with fewer samples.

钛合金铸锭冒口损失率差异性成因分析及对策研究

VAR熔炼的钛合金铸锭,熔炼末期需要采用补缩工艺制度,降低铸锭冒口损失率,提高成材率。在实际生产过程中,钛合金铸锭冒口损失率受各种因素影响,每个铸锭之间存在较大差异,且波动范围大,损失严重。为了分析钛合金铸锭冒口损失率差异性的影响因素,应用Minitab统计软件,采用多因子方差分析方法进行研究,找出了熔炼工班次、补缩时间班次、探伤操作者、补缩期操作稳定性、补缩过程是否频繁短路等显著影响因子,排除了不显著的因子交互作用,并针对各显著因子,制定了相应的改进对策,有效降低了钛合金铸锭冒口损失率以及铸锭间的差异性,提高了成品率。

C70600白铜空心锭立式连铸工艺参数对凝固过程的影响

为了获得Ф260×Ф80 C70600白铜空心锭立式连铸合理的工艺参数,通过数值模拟定量分析了各种工艺参数对温度场和应力场的影响。结果表明:浇铸温度每提高20℃,液穴深度增加10 mm;拉坯速度每提高10 mm/min,液穴深度增加20 mm;液穴深度随着石墨芯管冷却强度的增大而减小。基于正交试验和方差分析发现,F_(A)>F_(0.01)(3,3),F_(B)>F_(D)>F_(0.1)(3,3),F_(C)<F_(0.1)(3,3),因此,拉坯速度对液穴深度的影响最显著,一冷强度对其影响不显著。根据模拟结果提出了合理工艺参数为:一冷强度24 m^(3)/h、拉坯速度80 mm/min、浇铸温度1280℃、芯管采用空冷。在此基础上成功试制出了合格的C70600白铜空心锭成品。

消胀止痛锭治疗混合痔术后肛门坠胀疼痛的临床疗效观察

目的:观察消胀止痛锭治疗混合痔术后肛门坠胀疼痛的临床疗效。方法:选取2021年1月到2022年8月住院患者。将符合纳入标准的120例混合痔术后患者进行随机分组,分为治疗组和对照组,两组患者各60例。治疗组给予消胀止痛锭直肠给药,对照组给予复方角菜酸脂酸直肠给药。比较两组患者术后肛门坠胀、水肿、疼痛、抑郁、焦虑评分,住院时间、手术创面愈合时间、肛门直肠测压、盆底表面肌电图等指标。结果:治疗组术后3、5、7天的肛门水肿、坠胀、疼痛、抑郁、焦虑评分均较对照组明显缓解(P<0.01),治疗组的住院时间较对照组减少(P<0.05),治疗组的伤口愈合时间较对照组明显缩短(P<0.01),治疗组患者术前与术后盆底肌电图和肛门直肠压力未发生明显变化(P>0.05),其中对照组在术后的初始感觉、最大耐受以及排便感觉阈值较术前增高(P<0.01),肛管长度增加(P<0.05),力排时直肠收缩压明显降低(P<0.01)。表面肌电图测量中,治疗组患者术后7天与术前相比较差异无统计学意义(P>0.05),对照组术后7天盆底肌力较术前比较则有明显的降低(P<0.01)。结论:消胀止痛锭直肠给药对混合痔术后肛门坠胀疼痛有明显疗效,能缓解混合痔术后患者焦虑紧张的情绪,缩短了住院时间,促进了术后创面的愈合,未见明显不良反应,操作简便,值得临床推广应用。

银铜侧向复合材料界面结合机理分析

本文采用“包覆锭坯+扩散烧结+冷轧复合”联合工艺制备了银铜侧向复合带材,利用金相显微镜(OM)、扫描电镜(SEM)和能谱仪(EDS)观察分析银铜复合界面结构和元素分布,并分析其银铜复合界面的结合机理。结果表明,银铜复合界面形成过程为:1)银铜接触界面处凹凸不平的表面在轧制力的作用下相互咬合,形成机械结合界面;2)接触面在轧制力的作用下,银铜表面氧化膜破裂,新鲜表面质点间在轧制变形热的作用下产生原子结合;3)在扩散烧结过程中,银铜界面处的原子在高温作用下被激活,银铜原子相互扩散,在界面处发生银铜共晶反应形成液相金属层,随着烧结时间的延长,其共晶反应液相层厚度逐渐增加,随后冷凝结晶,使银铜实现侧向冶金结合。4)在后续中间退火过程中,共晶层与两侧的铜、银基体相互扩散,铜、银原子向更深的方向逐渐扩散,在靠近共晶层铜侧和银侧逐步形成固溶体层,使银与铜的结合强度进一步提高。银铜侧向复合界面结合机理包含机械咬合结合、接触共晶反应自钎焊结合和原子扩散结合3种,复合界面结合强度较好,剪切强度达220 MPa。

余热利用技术在铝锭加热炉上的应用

文章介绍了一种新型余热利用技术,对其特点和使用进行了阐述,并指出余热回收技术可以有更广阔的应用方向。

钢液钙处理过程有效钙硫比对303 t超大钢锭中硫化物形貌的影响

通过工业实验研究了钙处理对303 t的16Mn重型管板铸锭中硫化物形貌的控制.未钙处理的锻件缺陷主要分布在轴向上靠近顶部、径向上在距中心1/2以内位置,缺陷主要为大尺寸Ⅱ类MnS夹杂物.采用Micro-CT检测了铸锭顶部中心位置MnS夹杂物三维分布,夹杂物为长条状和片状,数密度为0.77 mm^(-3),最大直径为1370μm.在真空脱气后对钢液进行钙处理,钙处理不仅将钢液中原生Al_(2)O_(3)夹杂物改性为液态钙铝酸盐,并且钙会在钢液凝固和冷却过程中优于锰先与硫结合生成CaS.通过FactSage热力学计算得到,钙处理将MnS夹杂物的析出温度由1244.7℃降低至1227.9℃,同时减少了MnS夹杂物析出量.钙在改性硫化物之前先改性了钢中氧化物,因此提出了有效钙硫比Ca/Seff.用来表征钙处理对硫化物形貌的影响,Ca/Seff.的含义为改性硫化物的有效钙和钢中硫的原子浓度比,可以直接根据钢液的总氧T.O含量、总硫T.S含量和总钙T.Ca含量计算得到,此公式适用于硫质量分数小于30×10^(-6)的低硫钢.随着钢中Ca/Seff.增加,铸锭顶部硫化物长宽比逐渐减小.钙处理后钢中有效钙硫比Ca/Seff.应大于0.8,铸锭顶部硫化物平均长宽比小于1.2,CaS和MnS复合硫化物以钙铝酸盐夹杂物为核心析出,硫化物为球形且尺寸显著减小,此时钙处理改性铸锭中硫化物效果较好.

高成材率钢锭缺陷控制技术及其研究进展

钢锭凝固过程中将不可避免地产生各类缺陷,严重制约了钢锭成材率,直接影响后续加工工艺和最终产品质量。抑制缺陷形成、探索创新并有效改进模铸工艺对提高钢锭成材率具有重要意义。通过探讨和分析关于提高钢锭成材率的研究现状和最新进展,包括锭型设计、工艺参数优化、先进铸造技术等,展望了多相流动控制、微观结构调控和冷却速率精准管理等未来模铸与凝固技术研究发展方向,为实现高成材率钢锭的稳定生产提供了合理化建议。

特殊钢模铸生产中钢锭模组合优化研究

针对特殊钢的生产特点,提出求解特殊钢模铸生产过程中的钢锭模组合优化问题的方法,该方法将钢锭模组合优化问题抽象为背包问题,并使用动态规划算法和递归回溯算法进行求解,能快速计算具有最优锻造比的钢锭模组合方案,还能计算所有满足要求的钢锭模组合,同时考虑了出钢量与电炉生产能力是否匹配的问题。通过对生产实例进行试验,验证了该方法的有效性,能够在一定程度上满足特殊钢企业的实际应用需求,对实际生产具有一定的指导意义。

铝及铝合金铸锭标识

首次发布的GB/T 42916-2023《铝及铝合金产品标识》,规定了铝及铝合金产品标识的标识分类、一般要求、铸锭标识、板材标识、带材标识、箔材标识、管材标识、棒材标识、型材标识、线材标识和锻件标识。文章依据GB/T 42916,介绍了铸锭标识的一般要求、铸锭标识信息、铸锭刻痕标识、喷码标识、标签标识、信息化标识以及航空航天用铝合金铸锭标识,供贯彻新标准时参考。

采棉机摘锭控形控性分析

对采棉机摘锭的工作过程进行分析,通过数学建模确定采棉和脱棉过程中摘锭钩齿几何参数对籽棉所受摘锭摩擦力的影响;在籽棉缠绕阶段,对摘锭与籽棉间弹塑性摩擦受力进行分析,建立摘锭锥面截面圆曲率半径与籽棉受摘锭摩擦力的数学关系;将摘锭简化成悬臂梁,建立力学模型确定强度最低锥面截面直径与摘锭锥面几何参数的数学关系;采用ANSYS对3种常见基材摘锭进行有限元分析,进一步确定不同材料对摘锭强度的影响,验证锥面曲率半径对籽棉采摘摩擦力的影响。研究结果为国产摘锭进一步控形控性多目标优化设计奠定理论基础。

三元PbBi_(2)S_(4)凝固生长与热电性能研究

三元PbBi_(2)S_(4)是一种具有本征低晶格热导率的潜力热电材料,但低的电传输性能制约了其热电性能。本工作利用Bridgman法制备了高质量的三元PbBi_(2)S_(4)晶体铸锭,由于减少晶界密度,降低晶界对载流子传输阻碍,电传输性能大幅度提升。通过优化生长条件获得不同质量的三元PbBi_(2)S_(4)晶体铸锭,最优加权载流子迁移率从多晶中15 cm^(2)/(V·s)提升到56 cm^(2)/(V·s),使三元PbBi_(2)S_(4)晶体铸锭的最大电导率和功率因子分别达到1049 S/cm和4.6μW/(cm·K^(2)),相比多晶PbBi_(2)S_(4)样品分别提高了850%和~64%。最终,PbBi_(2)S_(4)晶体铸锭的最大ZT值在773 K温度下达到0.61。结果表明,通过凝固生长高质量晶体铸锭能显著优化三元PbBi_(2)S_(4)化合物全温区热电性能。

150 MW级新兴生物质发电机组用Cr-Ni-Mo-V钢转轴锻件制造工艺研究

对于150 MW级Cr-Ni-Mo-V钢发电机转轴锻件的制造工艺要点进行阐述,通过采用下注单真空钢锭制造技术路线,对其主要热加工工序制造工艺进行研究以及产品试制,经过各项理化检验,转轴锻件的化学成分、力学性能等指标满足技术要求。

铁路轴箱轴承用8620钢3 t钢锭轧制产品研发

针对中国铁路客车和货车轴箱轴承用钢主要使用电渣钢的现状,采用铁水+废钢→70 t电弧炉→LF→RH→3 t钢锭→均热坑→1350+750/650轧机轧制的流程生产规格ϕ60~ϕ120 mm 8620钢(质量分数/%:0.18~0.22 C,0.15~0.30 Si,0.75~0.95 Mn,0.45~0.65 Cr,0.45~0.70 Ni,0.15~0.25 Mo,≤0.020 P,≤0.015 S,0.020~0.050 Al)。通过控制出钢留钢留渣、炉后造渣和合金化,真空处理时间≥25 min,氩气弱搅拌,控制钢水过热度,全过程Ar气保护,模铸自动浇注,轧制后控制冷却等工艺措施,生产的产品宏观夹杂物检测含量≤10 mm/dm3,晶粒度8~8.5级,密度达到7.854 g/cm^(3),钢材各项指标满足标准要求。