“Quartus scale” of hot-rolled strip steels and its formation mechanism

The types and growth of various oxide scales formed during the different phases of the production of hotrolled strip steel products are reviewed. Similarities and differences between the ＂tertiary scale＂ on the surface of carbon steels at high temperatures and the oxide scale on pure iron are compared. The micro-structural features of the ＂final oxide scale＂ on the surface of strip steels at room temperature as well as the relationship between these features and the position of the steel coil （plate） and the subsequent processes of recoiling, temper rolling and trimming, etc. are summarized. The actual oxide scales retained on the commercial hot-rolled strip steels at room temperature have been proposed to define as ＂ quartus scale＂ for the first time. The micro-structural development and phase transformation of the initial ＂tertiary scale＂ during and after cooling and coiling are described. The reasons for the ＂tertiary scale＂ on carbon steels differing from the oxide scale formed on pure iron, and the major influencing factors in the formation of various types of ＂quartus scales＂ are analyzed from both thermodynamic and dynamic viewpoints. The development mechanism of ＂ quartus scales＂ is discussed and the potential effects of the ＂ quartus scale＂ state （thickness, constitution, structure and defects）, on the rusting and pickling properties of commercial hot-rolled strip steel, as well as on the mechanical properties of oxide scales are analyzed.

Effect of Direct Quenching and Partitioning Treatment on Mechanical Properties of a Hot Rolled Strip Steel

Three different online heat treatment processes were designed to study the effects on the mechanical properties of a 0.19C-1.6Si-1.6Mn（wt%） hot rolled strip steel.The microstructures were characterized by means of SEM,TEM,EPMA,and XRD.The mechanical properties were estimated by tensile tests.Results showed that a satisfying combination of strength and ductility could be obtained through the ferrite relaxation and direct quenching and partitioning process.Analysis was also focused on this process.The microstructure contained proeutectoid ferrite grains,martensite packets and blocky or interlath retained austenite,and also contained carbide-free bainite in the case of relatively high quench temperatures.The retained austenite fraction was increased through proeutectoid ferrite and partial bainite transformation,while the tensile strength was also consequently decreased.The most of retained austenite transformed to ferrite under deformation and the elongation was obviously improved.

Influence of oxide scales on the corrosion behaviors of B510L hot-rolled steel strips

The influence of oxide scales on the corrosion behaviors of B510 L hot-rolled steel strips was investigated in this study. Focused ion beams and scanning electron microscopy were used to observe the morphologies of oxide scales on the surface and cross sections of the hot-rolled steel. Raman spectroscopy and X-ray diffraction were used for the phase analysis of the oxide scales and corrosion products. The corrosion potential and impedance were measured by anodic polarization and electrochemical impedance spectroscopy. According to the results, oxide scales on the hot-rolled strips mainly comprise iron and iron oxides. The correlation between mass gain and test time follows a power exponential rule in the damp-heat test. The corrosion products are found to be mainly composed of γ-Fe OOH, Fe3O4, ？-Fe OOH, and γ-Fe2O3. The contents of the corrosion products are different on the surfaces of the steels with and without oxide scales. The steel with oxide scales is found to show a higher corrosion resistance and lower corrosion rate.

Computer Simulating Calculation on the Microstructure Evolutions during Hot Strip Rolling of C-Mn Steels

The program to predict the microstructure evolutions during hot strip rolling of C-M n steels has been developed in this paper, BV using this program, the microstructure changes with the processing parameters were analysed in detail. showing not only a good agreement of prediction with the measured values, but also entirely possibility to optimize hot strip rolling precess by computer simulation

Effect of hot rolling on the microstructure and impact absorbed energy of the strip steel by CSP

The microstructures and impact absorbed energies at various temperatures were investigated for steel strips hot rolled to thickness reductions of 95.5%, 96.0%, 96.5%, 97.0%, and 97.5%. Results indicate that grain refinement can be realized with an increase in hot rolling reduction. Besides, finer precipitates can be achieved with an increase in hot rolling reduction from 95.5%to 97.0%. The impact absorbed energy decreases with a decrease in testing temperature for steel strips hot rolled to 95.5%, 96.0%, and 96.5%reductions in thickness. However, in the case of steel strips hot rolled to 97.0%and 97.5%reductions in thickness, the impact absorbed energy remained almost constant with a decrease in testing temperature.

Development and future prospect of hot strip rolling technology at Baosteel

Since the 2050 mm hot strip mill was put into operation in 1989, Baosteel has made great achievements in increasing productivity, developing new process technologies and steel products and improving product quality. In the past 18 years from 1989 to 2007 ,Baosteel has constructed five hot strip mills with a total annual capacity of 19.8 Mt. Indices for technology standards, product categories and steel grades, product quality, both technically and economically, take the lead domestically or reached the world class level. As there are many hot strip mills that expected to be put into operation by the end of 2010 ,the overall annual capacity will exceed 30 Mt ,and the product will cover grain oriented （GO） Si steels and alloyed steels.

Mill scale structure and damp heat corrosion performance of four 510L hot-rolled strips

In this study, the matrix structure, state and composition of the mill scales of four typical domestically made 510L hot-rolled strips were observed and analyzed by means of optical microscopy （OM） ,scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The corrosion behavior of the steels with and without mill scales were investigated by means of hot-humid corrosion tests under the condition of relative humidity （ RH ） of 95% at 50℃ and 70℃, respectively. The results show that the matrix structures, state, composition and thickness of mill scales vary in the strips. The rusting starting time of the specimens with scales is generally a bit longer than that of the specimens without scales, but their corrosion mass-gain is higher. For these two kinds of specimens ,their corrosion rate increases significantly with the increase of temperature. The rusting behavior of the 510L strips produced by various plants is different due to the variations of hot-rolling processes and designed chemical compositions. Various relevant aspects should be taken into account in the evaluation of the corrosion behavior of hot-rolled strips.

On-line control of surface quality for an axially moving steel strip partially immersed in fluid under tension

An on-line control method of surface quality for continuous hot-dip galvanized steel strip after cooling is presented, which combines analytical dynamics theory of a thin plate with the finite element method. The inherent characteristics of the non-immersed and partially immersed strip in liquid zinc were calculated on the basis of theoretical analysis and numerical simulation, respectively. Multi-parameter fitting of the deviation between results using different methods was performed. To optimize the strip excitation frequency away from the resonance region, on-line vibration control of the strip near the air knife under full product conditions was achieved by changing the field production parameters based on the field test results. The results indicate that although the axial velocity has little effect on the inherent characteristics of the strip compared with other manufacturing parameters such as the steel specifications and tension, it induces external excitations,including moving the aerodynamic load and bearing vibration. To some degree, the vibration near the air knife can be reduced by strengthening the support stiffness of the contact rolls. A total on-line control program of surface quality for continuous hot-dip galvanized pure Zn and galvannealed steel sheet in the cooling section is proposed.

热轧宽带钢极薄板轧制失稳原因分析与控制

基于鞍钢股份有限公司热轧带钢厂2150ASP生产线轧制情况,对热轧宽带钢极薄板轧制失稳导致的顺折事故进行了分析。结果表明,临近年修末期,精轧机组的设备精度下降,厚度精度下降,F6机架的自动厚度控制液压缸动作幅度大且响应快,导致了顺折事故的发生。通过优化精轧自动厚度控制响应速度、动作限幅以及功能选用,有效解决了轧制失稳导致的顺折问题,顺折事故发生率由0.046%降低至0.011%。

汽车用热浸镀铝硅带钢技术研究进展

汽车用热浸镀铝硅带钢技术是一种先进的金属防腐涂层技术,广泛应用于汽车制造领域。基于热浸镀铝硅带钢的制备工艺和性能特点,全面分析热浸镀铝硅带钢在汽车制造领域的应用、市场前景及竞争格局,并对热浸镀铝硅带钢的未来发展进行了展望,旨在为相关领域的科研人员和企业提供参考和借鉴,推动汽车用热浸镀铝硅带钢技术的进一步发展和应用。

Ti微合金化400 MPa级光伏支架用钢的开发

详细介绍了山西建龙1500生产线试制400 MPa级光伏支架用热轧钢带的成分设计、工艺路线以及产品质量情况。生产实践表明,按照设计的成分和工艺生产的光伏支架用热轧带钢的组织为铁素体+少量珠光体,拉伸性能和冷弯性能优异,能够满足用户的使用要求。

汽车车轮用高扩孔率热轧复相钢带的研制

设计了一种微合金化的汽车车轮用高扩孔率热轧复相钢,并对其进行了工业试制。采用金相检验、力学性能测试等方法研究了高扩孔率热轧复相钢的显微组织及力学性能。结果表明:试制产品的显微组织主要由贝氏体、铁素体构成,还分布有少量的马氏体、残余奥氏体以及弥散析出的第二相粒子,产品的屈服强度、抗拉强度、断后伸长率分别超过了520,610MPa和24%,屈强比为0.85~0.87,扩孔率达到83%以上,沿板宽方向的扩孔率在10%以内波动;增加Si元素含量能明显改善扩孔性能,同时会影响产品的表面质量,将Si元素的质量分数控制在0.20%左右较为合适;试制产品具有优异的局部成形性、良好的抗疲劳性和焊接性能,在疲劳试验承载力为1700 N·m的条件下,车轮弯曲疲劳寿命达到60万次以上。

基于时域卷积网络的精轧出口厚度预测

以精轧过程为研究对象,引入时域卷积网络算法,构建了基于时域卷积网络的精轧出口厚度预测模型。利用时域卷积网络模型提取精轧过程时序数据的特征信息,通过优化模型结构和参数,提升精轧出口厚度预测性能。实际钢种数据集仿真实验结果表明,相较于传统方法,本文所提出的时域卷积网络算法在均方根误差、平均绝对百分比误差及决定系数等评价指标方面存在较大优势,可为现场工程师提供重要的决策信息。

轧制温度对SPHC热轧带钢氧化铁皮的影响

针对现场SPHC热轧带钢表面的麻点/坑缺陷,研究了干燥空气中SPHC热轧带钢在实际粗轧至精轧温度范围(830~1080℃)内的氧化行为,利用显微镜对氧化铁皮表面的起泡现象、氧化铁皮横截面的厚度与结构进行分析,预测了氧化铁皮厚度随氧化温度变化的规律.结果表明:当氧化温度为830~1080℃时,SPHC热轧带钢的氧化过程遵循抛物线规律,氧化铁皮厚度随氧化温度的升高而增加;当氧化温度830~930℃时,Fe_(3)O_(4) 层占比随氧化温度的升高而增加,板坯受氧化铁皮影响较小;当氧化温度为930~1030℃时,Fe_(3)O_(4) 层占比大于FeO层占比,氧化铁皮出现起泡现象;当氧化温度为1011℃时,氧化铁皮的增厚速率达到最大,此时氧化铁皮的变形性也最差,带钢极易产生麻点缺陷;适当增加粗轧后的除鳞水量、降低精轧开轧温度,以及关注初始道次轧辊表面质量,可有效避免SPHC热轧带钢表面的麻点/坑缺陷.

基于改进斑点鬣狗算法的热轧带钢负荷分配智能优化

针对热连轧过程中由于负荷分配不均匀导致板形控制效果不佳的问题,以传统的轧制机理为基础建立负荷分配均匀、板形良好的目标函数,分别采用斑点鬣狗算法和改进斑点鬣狗算法进行单目标和双目标的负荷分配的优化求解。结果表明,改进斑点鬣狗算法将末机架的相对凸度差从0.000 834 5降低到0.000 014 83和-0.000 026 34,且在允许的范围内,上游机架负荷分配合理,充分发挥了轧机的轧制能力。

高品质太阳能支架用热轧钢带的开发生产

针对太阳能支架轻量化、高强化的实际要求,联合某冷轧企业,采用低碳、低硅、微钛的成分体系设计,通过控轧控冷工艺成功开发出355 MPa强度级别,同时满足易涂镀、高延伸使用要求的太阳能支架专用热轧钢带。该钢带组织为珠光体+铁素体,晶粒细小均匀,具备高强韧性的同时,兼顾较好的延展性及表面质量,满足客户冷轧退火后性能要求,以及镀锌铝镁不漏镀、无漏点的高表面质量要求。

热轧卷取机带钢头部堆钢现象分析

带钢卷取时,会因电气设施发生故障、自动控制不够完善、异物卡阻等问题造成设备停机,导致带钢头部出现堆钢现象。针对此,结合自动化控制长期实践经验,对带钢头部堆钢原因进行了分析研究,并制定相应的处理和预防措施,以减少带钢头部堆钢事故的发生。

VCR法采空区爆破成井技术的研究与应用

呼伦贝尔山金铅锌矿采用充填法治理历史采空区,由于采空区充填井采用普通法掘进效率低、作业条件及安全性差,采用采空区充填井安全高效施工技术成为关键。根据利文斯顿爆破漏斗理论,通过前期进行的大量试验爆破,确定最佳爆破参数,结合现场条件研究提出VCR法爆破快速成井技术方案。实践结果表明,VCR法在爆破采空区充填井上取得了良好的应用效果,成功开掘了直径2.0 m、深度17.4 m的充填井。重点对爆破参数、装药结构、堵孔方式以及施工过程中存在的问题进行分析总结,为同类矿山提供一定的参考和借鉴。

原料钢坯氧化铁皮控制研究

热轧带钢和原料坯氧化铁皮的厚度对于提高钢产品表面质量、降低生产成本具有重要意义,但原料坯进入加热炉后,氧化铁皮逐渐脱落、堆积,会严重影响加热炉正常运行,若处理不当,还会造成产品表面缺陷。针对此问题,重点分析了原料钢坯氧化铁皮在生产中对加热炉的主要影响,并针对性地制定了优化钢产品化学成分、调整生产工艺参数、制作氧化铁皮清除装置等工艺优化措施,减少了热轧带钢中氧化铁皮的轧入。

ESP热轧钢带在药芯焊丝生产中的应用

为响应降本提质的生产要求,对比热轧钢带与冷轧钢带在药芯焊丝的生产效率、表面质量、填充率稳定性、焊丝力学性能等方面,并针对热轧钢带在生产时需要注意的几个重要工艺问题以及成品焊丝的能用性等问题进行了探究。发现通过降低热轧钢带塑性,增加其拉拔韧性,采用钢带延伸率为36%~40%,能够使ESP热轧钢带稳定地用于药芯焊丝E71T-1的生产。