Microstructure and properties of LZQT600-3 HCCDIBs for plunger pump cylinder

It is important to improve the comprehensive performance of the ductile iron bars(DIBs)for the cylinder block of the extra high pressure hydraulic plunger pump and accelerate the industrial application.In this work,the LZQT600-3 DIBs with the diameter of 145 mm were prepared by the horizontal continuous casting(HCC)process,that is,LZQT600-3 HCCDIBs.The microstructure and room temperature tensile properties of different sections[left-edge(surface layer),left-1/2R(left half of the radius),and the center of the HCCDIBs]were studied.The results show that the spheroidization of LZQT600-3 HCCDIBs matrix from the left-edge,left-1/2R to the center is at nodulizing grade II and above.As the cooling rate gradually decreases from surface to the center of the HCCIBs,the number of spheroidized graphite is gradually reduced,the size is gradually increased,the shape factor is decreased,and the pearlite content and lamellate spacing are increased.Along the horizontal direction of the section,the hardness of the material is distributed symmetrically around the center of the HCCDIBs.In the vertical direction,the hardness distribution in the center of the HCCDIBs is asymmetrical due to the gravity during the solidification process.Therefore,the microstructure in the lower part of the section solidifies relatively quickly.The left-edge has the best tensile mechanical properties,and the ultimate tensile strength,yield tensile strength and elongation are 597.3 MPa,418.5 MPa and 9.6%,respectively.The tensile fracture belongs to the ductile-brittle hybrid fracture.The comprehensive performances of LZQT600-3 HCCDIBs meet the actual application requirements of ultra-high pressure hydraulic plunger pump cylinder.

Irregular initial solidification by mold thermal monitoring in the continuous casting of steels:A review

Occasional irregular initial solidification phenomena,including stickers,deep oscillation marks,depressions,and surface cracks of strand shells in continuous casting molds,are important limitations for developing the high-efficiency continuous casting of steels.The application of mold thermal monitoring(MTM) systems,which use thermocouples to detect and respond to temperature variations in molds,has become an effective method to address irregular initial solidification phenomena.Such systems are widely applied in numerous steel companies for sticker breakout prediction.However,monitoring the surface defects of strands remains immature.Hence,indepth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems.This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems.Furthermore,the influences of mold slag behavior on monitoring these phenomena are analyzed.Finally,the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed,and future research directions are proposed.

Liquid-solid interface control of BFe10-1-1 cupronickel alloy tubes during HCCM horizontal continuous casting and its effect on the microstructure and properties

Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube （φ50 mm × 5 mm）. HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250℃ melting and holding temperature, 1200-1250℃ mold heating temperature, 50-80 mm/min mean drawing speed, and 500-700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure （{hkl}〈621〉, {hkl}〈221〉） due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%-47.2% and 210-221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.

Effects of calculation approaches for thermal conductivity on the simulation accuracy of billet continuous casting

An unsteady, two-dimensional, explicitly solved fmite difference heat transfer model of a billet caster was presented to clarify the influence of the thermal conductivity of steel on model accuracy. Different approaches were utilized for calculating the thermal conductivity of solid, mushy and liquid steels. Model results predicted by these approaches were compared, and the advantages of advocated approaches were discussed. It is found that the approach for calculating the thermal conductivity of solid steel notably influences model predictions. Convection effects of liquid steel should be considered properly while calculating the thermal conductivity of mushy steel. Different values of the effective thermal conductivity of liquid steel adopted could partly be explained by the fact that different models adopted dissimilar ap- proaches for calculating the thermal conductivity of solid and mushy steels.

Forming Conditions and Neural Network Control of Continuously Directional Microstructurein Directional Solidification Continuous Casting Process

Directional solidification continuous casting (DSCC) process is a new manufacturing technology for metallic materials which combines advantages of both directional solidification technology and continuous casting technology. Unlimited long shaped metal with directionally solidifying microstructure can be produced by this process. It is experimentally shown that controlling condition of stable and continuous growth of single crystal structure means the precise control of the location of the S/L interface, which is affected and determined by seven process parameters. Moreover, these parameters are also interacted each other, so the disturbance of any parameters may cause the failure of controlling of S/L interface. In this paper, on the basis of analyzing the forming conditions of continuously directional microstructures in DSCC process, the control model of DSCC procedure by neural network control (NNC) method was proposed and discussed. Combining with the experiments, we first used the computer to simulate the effects of the solidification parameters on destination control variable (S/L interface) and the interactions among these parameters during DSCC procedure. Secondly many training samples necessary for neural network calculation can be obtained through the simulation. Moreover, these samples are inputted into neural network software (NNs) and trained, then the control model can be built up.

Formation and control of the surface defect in hypo-peritectic steel during continuous casting:A review

Hypo-peritectic steels are widely used in various industrial fields because of their high strength,high toughness,high processability,high weldability,and low material cost.However,surface defects are liable to occur during continuous casting,which includes depression,longitudinal cracks,deep oscillation marks,and severe level fluctuation with slag entrapment.The high-efficiency production of hypo-peritectic steels by continuous casting is still a great challenge due to the limited understanding of the mechanism of peritectic solidification.This work reviews the definition and classification of hypo-peritectic steels and introduces the formation tendency of common surface defects related to peritectic solidification.New achievements in the mechanism of peritectic reaction and transformation have been listed.Finally,countermeasures to avoiding surface defects of hypo-peritectic steels duiring continuous casting are summarized.Enlightening certain points in the continuous casting of hypo-peritectic steels and the development of new techniques to overcome the present problems will be a great aid to researchers.

关于MCCR产线MTS磁尺故障原因分析与维护探析

主要介绍MCCR产线投产以来MTS磁尺跳变故障情况,并从原理上分析讨论磁尺发生跳变故障的原因,结合实际情况摸索相应的维护方法,有针对性地对磁尺采取一系列有效可行的维护措施,最终降低了MCCR产线磁尺跳变故障,确保了产线安全稳定运行。

Analysis of inhomogeneity of solidified microstructure of continuous casting copper tubular billet based on factor analysis

The horizontal continuous casting process,the initial step in TP2 copper tubular processing,directly determines the microstructure and properties of copper tubular.However,the process parameters of the continuous casting characterize time variation,multiple disturbances and strong coupling.As a consequence,their influence on a casting billet is difficult to be determined.Due to the above issues,the common factor and special factor analysis of the factor analysis model were used in this study,and the casting experiment and billet metallographic experiment were carried out to diagnose and analyze the reason of the microstructure inhomogeneity.The multiple process parameters were studied and classified using common factor analysis,2 the cast billets with abnormal microstructures were identified by GT^(2) statistics,and the most important factors affecting the microstructural homogeneity were found by special factor analysis.The calculated and experimental results show that the principal parameters influencing the inhomogeneity of solidified microstructure are the primary inlet water pressure and the primary outlet water temperature.According to the consequence of the above investigation,the inhomogeneity of the copper billet microstructure can be effectively improved when the process parameters are controlled and adjusted.

Analysis of Corrosion Behavior of ZrO_(2)-C Slag-line Materials in Continuous Casting

In view of the service failure and low continuous casting production efficiency due to the corrosion of refractories at the slag-line in submerged entry nozzles,a submerged entry nozzle for low-carbon aluminum killed steel continuous casting in one steel plant was sampled and taken as the research object to analyze the causes and the mechanism of refractory corrosion at the slag-line.The results show that the core issue of the corrosion and necking of the slag-line materials is that the slag-line material are eroded,dissolved,and reacted by the mold flux gradually.Therefore,it is important to suppress or avoid the contact and reaction between the mold flux and slag-line materials.

鞍钢8m弧半径小方坯连铸机提速实践

针对8 m弧半径小方坯铸机拉速低不能满足生产要求的问题,分析了影响铸机提速的主要原因,采取了增加结晶器长度,更新结晶器供水泵,更新二冷水嘴,增大二冷管径以及优化系统温度等措施,铸机拉速由2.8 m/min提高到3.5 m/min,铸坯质量合格率达到99.95%,实现了小方坯铸机高速稳定生产。

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。

流程生产风险防控的功能安全完整性

为提升流程生产安全管理水平,降低事故发生概率,提出了生产过程中风险防控的功能安全完整性分析方法,并结合钢铁连铸场景进行验证。首先评估流程生产中主要事故类型的危险程度和确定其可接受频率标准;运用保护层分析法计算作业现场高危险性事故发生的真实概率,通过与可接受频率比较,判断是否需要新增防护措施;运用蒙特卡洛-马尔可夫模型验证新增防护措施的功能安全完整性等级。以大冶特钢炼钢转炉厂连铸作业区为例,结果表明:研究区内存在熔融物爆炸、火灾和中毒窒息3类高危险性事故隐患,且熔融物爆炸事故的人员伤亡后果为不可接受,需新增功能安全完整性等级为2级的防护措施;设计了防爆炸保护系统,其失效概率为4.37×10-3,满足功能安全完整性等级要求。

中间包等离子体加热技术研究进展及应用

在钢铁行业面临转型升级的新常态形势下,借助智能装备驱动钢铁产业向绿色高端化发展,有望实现钢铁生产组织的最优化。连铸中间包实现恒温、低过热度浇铸可有效改善钢材质量,为此发展中间包加热技术十分必要。针对近年来日益受到重视的中间包等离子体加热技术的相关热点问题,系统阐述了其加热原理和设备特点,介绍了等离子体加热技术国内外设备、冶金功能研发以及应用进展状况,重点分析了等离子体加热技术对中间包内钢液流场、温度场、夹杂物去除、钢液化学成分的影响,以及实际应用冶金效果。基于对等离子体加热技术研究和应用的深入认知,探讨了国内自主研发新型中空石墨电极加热过程发现的新问题,以及进一步提高其冶金效果的途径。分析表明,国内自主研发的中空石墨电极等离子体加热装置,更好的适配了国内钢铁行业变革需求,是解决浇铸钢水过热度不稳定、钢水洁净度水平低和钢水组织成分不均匀问题的有效途径,补齐精准定位“一键加热”中间包的智能化短板。

超大规格风电用连铸圆坯的氢含量控制

针对直径大于等于800 mm的超大规格风电用连铸圆坯因氢含量高出现探伤不合缺陷的问题,通过检测原辅料水分、利用Hydris定氢仪探究全工序钢水氢含量的变化规律。结果表明,铸坯氢含量的主要来源是原辅料水分、炉气气氛潮湿、耐火材料不完全分解。为降低铸坯氢含量,提出了工艺改进措施:转炉吹炼8 min后应不加或加入水分含量较低的原辅料;LF精炼工序投入较少的原辅料;入VD工序前小渣量控制,破空后低速喂线,控制喂线数量及种类在较小范围;小火烘烤连铸中间包60 min,定期清理中间包透气孔。工艺优化后,VD到站钢水w(H)≤3.6×10^(-6),VD离站钢水w(H)≤0.77×10^(-6),连铸中间包首炉钢水w(H)≤2.0×10^(-6),第2炉w(H)≤1.6×10^(-6),连浇炉次w(H)≤1.1×10^(-6),成功降低了超大规格风电用连铸圆坯的氢含量,保证了成品锻件的质量。

409L不锈钢连铸坯表层夹杂物试验研究

为研究409L不锈钢连铸坯表层夹杂物形貌、分布及类别,取样后逐次研磨1 mm后进行夹杂物检测,并将检测结果进行对比分析。发现夹杂物分布呈随机性分布特征、尺寸主要集中在2~5μm,在空间分布上呈现随着深度的增加夹杂物数量呈现递减、中间位置夹杂物数量较两端少、内弧侧数量略高于外弧侧的特征,连铸坯表层夹杂物主要为12CaO-7Al_(2)O_(3)及一定比例的氧化物及少量其他类别夹杂物。

Ag含量对低合金化Cu-Ag合金拉拔线材组织和性能的影响

采用热型水平连铸技术制备Ag含量分别为0.6%、1.0%、2.0%和4.0%的Cu-Ag合金杆坯,并将d 16.0 mm杆坯拉拔加工成d 1.0 mm的线材,利用透射电镜分析其微细组织,并测试导电和力学性能。结果表明:拉拔线材由平行于拉拔方向的纤维晶组成,Cu-0.6Ag合金线纤维晶平均宽度约为340 nm;随着Ag含量增加,纤维晶尺寸减小,Cu-4.0Ag合金线纤维晶平均宽度为115 nm。纤维晶存在显著的〈111〉取向,纤维晶晶界主要为由位错塞积形成的小角度晶界,晶内存在大量位错,并发现少量的孪晶。随着Ag含量增加,Ag元素分布由局部富集转变为Ag相析出。Cu-0.6Ag和Cu-4.0Ag合金线材导电率随Ag含量的增大而减小,分别为91.2%IACS和79.5%IACS。Cu-0.6Ag和Cu-4.0Ag合金线材抗拉强度随Ag含量的增加而增大,分别为402.6 MPa和702.9 MPa。抗拉强度提高的主要原因是细晶强化和Ag相沉淀强化作用。

Fe-3%Si合金薄带连铸板热处理过程层状异构组织演变的相场模拟研究

本研究基于Fe-3%Si合金铸轧板材组织特征,构建了不同类型柱状晶/等轴晶层状异构组织相场模型,实现了界面曲率为驱动力的情况下层状异构组织的高温粗化过程模拟,量化分析了层状异构特征对铸轧组织演化过程的影响规律。研究表明,由于晶粒长径比对晶粒尖端曲率的影响,当初始状态下柱状晶长径比较高时,在界面曲率的驱动下最终会形成等轴化的多晶组织;反之则等轴化程度减小。明确了不同类型异构组织演化特征,相同退火时间下组织的等轴化程度受其层状异构特征的影响,这一现象的本质是等轴晶通过自身演化引起柱状晶两端曲率变化,诱发柱状晶间的相互“吞噬”并发生等轴化,柱状晶则在部分结构的组织中生长至带钢表面后停止生长,最终保持柱状特征。本研究进一步加深了对铸态薄带中初始凝固组织在后续热处理时演化过程的认识,对硅钢制备工艺优化具有重要的理论指导意义和实际应用价值。

连铸切割的在线优化

连铸是将钢水变成钢坯的生产过程,在连铸停浇时,会产生尾坯,尾坯的切割也是连铸切割的组成部分。在满足用户的目标值的前提下,我们尽量让切割损失最小。在合理假设的前提下对连铸切割的合理优化,综合运用EXCEL、MATLAB等多种工具,根据数学中的优化及整数规划知识建立优化模型,从而求出最优解。

基于无监督学习的连铸铸坯缺陷检测方法

铸坯在连铸过程中受温度分布不均、流动速度不稳等多种因素的影响,容易出现各种表面和内部缺陷,如疏松、偏析、缩孔、裂纹、气泡、夹杂等。这些缺陷不仅影响产品的外观和性能,还可能对工程结构的安全性产生潜在威胁。针对这一问题,提出了一种基于无监督学习的连铸铸坯缺陷检测方法,该方法利用图像频域处理技术和深度学习算法学习连铸铸坯正常样本的图像特征,通过图像重建方式自动检测铸坯图像中的缺陷。首先,通过频率解耦模块对铸坯图像进行图像频率分离,得到铸坯的低频图像与高频图像。然后,采用带有自监督预测卷积注意模块的生成器网络集合,分别重建低频图像和高频图像。最后,通过判别器网络对铸坯的原始图像与重建图像进行判定,以确定铸坯图像中是否包含缺陷。实验结果表明,该方法能够有效检测连铸铸坯的缺陷,具有较高的准确性和可靠性,可为提高连铸产品质量和生产效率提供有力支持。

铝脱氧钢中Al_(2)O_(3)夹杂物与Al_(2)O_(3)-C质水口耐材的粘附机理研究

铝脱氧钢连铸过程中的水口堵塞一直是困扰生产的难题,弄清水口堵塞的形成机理对解决该问题非常重要。研究首先在实验室制备了含有单一、量多的Al_(2)O_(3)夹杂物的钢液,然后与Al_(2)O_(3)-C质耐材棒反应不同时间,研究了钢中Al_(2)O_(3)夹杂物与耐材棒的粘附行为,在此基础上探讨了铝脱氧钢连铸过程水口堵塞的形成机理。研究发现,耐材棒与钢液反应一段时间后,在耐材棒表面由内向外逐渐形成两层Al_(2)O_(3),第1层致密平滑,厚度较薄;第2层松散粗糙,厚度较厚。水口堵塞的形成机理为,耐材插入钢液一段时间内,因温度升高,耐材表面区域的SiO_(2)、Al_(2)O_(3)与C反应生成的SiO、Al_(2)O气体向钢液扩散,在耐材表面分别与钢液中的[Al]、耐材中的SiO_(2)反应生成Al_(2)O_(3);耐材棒表面的SiO_(2)也会与钢液中的[Al]反应生成Al_(2)O_(3);三者共同作用形成第1层致密的Al_(2)O_(3)。第1层Al_(2)O_(3)层形成后,钢液中的Al_(2)O_(3)夹杂物易于在其上面附着,形成第2层松散的Al_(2)O_(3)。随着时间的延长,Al_(2)O_(3)层变厚,水口堵塞逐渐形成。第1层Al_(2)O_(3)形成机理以化学反应为主,增长缓慢;第2层以钢中夹杂物粘附为主,增长较快。