Rusting behavior and preventative measures of hot-rolled steel plates for automobile applications

As one of the important categories of hot-rolled products, hot-rolled steel plates for automobile applications generally undergo uniform corrosion or localized corrosion according to different environments of manufacturing, transportation and/or storage of the plates. General corrosion often takes place on the surface of a plate in the exterior part of a package, and only reduces the thickness of the plate and slightly increases the roughness of the surface; however, localized corrosion on the surface of a plate inside the package is likely to result in the formation of pit-like defects on the substrate of the plate, which cannot be removed thoroughly by normal acid pickling or sand blasting, and affects the application of the plate. This research report analyzes the phenomena and characteristics of the rusting behavior of hot- rolled steel plates for automobile applications, and the influencing factors are summaried. The corresponding preventative measures are proposed.

Microstructure and properties of Ti-bearing hot-rolled high-strength steel plates for two-sided enameling

The composition and production technology of the type of hot-rolled steel plate used in two-sided enameling were briefly described. The microstructure and mechanical properties before and after enameling were contrastively investigated,and the precipitates in the samples were analyzed using transmission electron microscope and energy dispersive spectrometer. The results show the ferrite grain size of the steel plate after high-temperature enamel firing to be fine,with a large number of TiC and Ti;C;S;precipitates dispersed throughout the ferrite matrix. After two rounds of enamel firing at a temperature range of 800-890 ℃,its yield strength can still reach342 MPa. The results of a hydrogen permeation test show that the hydrogen storage properties of the steel plate are much better than those of ordinary structural carbon steel. A better bubble structure in the enamel layer can be obtained by this steel plate,with no fish-scale defects on the enameled steel-plate surface.

Internal oxidation of hot-rolled ultra-high strength steel and its effect on the surface quality of cold-rolled sheets

In this study,the scale and internal oxidation of hot-rolled ultra-high strength steel sheets were characterized.It was found that both the formation of the scale and the internal oxidation of Si and Mn depended on the coiling temperature and position of the steel sample on the strip coil.At a relatively high coiling temperature,a large amount of internal oxidation was observed on the samples cut from the middle of the coil.The depth of the internal oxidation zone exceeded 10 μm and a thin iron layer covering the scale was observed in some cases.Pickling and cold-rolling experiments were conducted on selected samples.Scale pickling was found to be greatly delayed by the formation of an iron layer,which frequently resulted in under-pickled defects.In addition,pickling of the entire internal oxidation zone was difficult,except at the grain boundaries,where the degree of internal Si and Mn oxidation was enriched.The surface of the cold-rolled steel sheet was ruined by the remaining oxidation zone in the subsurface of the pickled steel.The internal oxidation of hot-rolled ultra-high strength steel must be precisely controlled to improve the subsequent surface quality of cold-rolled steel.

Study on process of roll bonding stainless and carbon steel under non-vacuum condition

The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the base materials, the microstructure of nickel cladding is observed by scanning electron microscopy （SEM） at high, and room temperature, and the results show that the nickel cladding on base material can be protected from oxidation in the high temperature. Non-vacuum roll bonding tests of nickel plating on base materials are done by the roll bonding equipment, and the roll bonding plates of stainless/carbon steel are obtained. The microstructure and the elements distribution of non-vacuum roll bonding interface are analyzed by optical microscope （OM） and SEM. The results reflect that the nickel plating layer and the base materials bond well.

Interfacial microstructure and mechanical properties of stainless steel clad plate prepared by vacuum hot rolling

A stainless steel clad plate composed of stainless steel and carbon steel was prepared by vacuum hot rolling process, and its microstructure, especially the bonding interface, was evaluated using an optical microscope, a scanning electron micro- scope and a transmission electron microscope （TEM）. The corresponding mechanical properties were also assessed by means of hardness and shear tests. The results showed a bonding interface formed between stainless steel and carbon steel, which was relatively straight in macroscope but serrated in microscope. Decarburization layer and carbon-enriched layer were distinguished at the side of carbon steel and stainless steel near the interface, respectively, which should be related to diffusion of carbon and alloying elements. The carbon-enriched layer could also be identified as a recombination region, whose microstructure was mainly recognized as martensite by TEM. Consequently, the hardness was the highest at this region. Furthermore, the result of shear test at the bonding interface showed that the shear strength was 395 MPa and the fracture mode was dominated as ductile fracture, indicating the bonding interface with good quality.

Numerical Simulation of Multi-pass Rolling Force and Temperature Field of Plate Steel During Hot Rolling

Rolling force and temperature field are important parameters in the hot rolling process of plate steel.Most researchers use ANSYS/LS-DYNA and MSC.Marc to simulate the hot rolling process,however,software DEFORM-3D is not used widely in this field.Therefore,in this study,the commercially available finite element analysis software DEFORM-3D is used to simulate the distribution of rolling force,stress-effective,strain-effective and temperature field during the hot rolling process of plate steel with the size of 0.220 m×2.070 m×1.904 m.Both the simulated rolling force and temperature of the multi-pass are compared with the measured results.It is shown that the simulated values by the finite element method are approximate to the measured values in the hot rolling of plate steel.So the simulation can provide an important reference and optimization to make rolling process and parameters in steel factory.

建筑结构钢板热轧轧机DBN-PSO振动预报及应用

利用实时监测数据(Real-Time Monitoring Data,RMD)参数分析轧机振动状态,综合运用深度置信网络(Deep Belief Networks,DBN)与粒子群(Particle Swarm Optimization,PSO)算法构建轧机振动仿真模型,实现RMD参数的深度挖掘,并达到轧机振动的预报效果。通过融合处理能够获得非常接近实际振动过程的预测数据,具备优异预测能力。结合现场测试的初始数据预测误差在3.5%范围内,跟轧机振动情况相符。当轧制速率变慢后,振动加速度出现了降低结果;入口张力对轧机的振动加速度具有反向作用;轧机振动加速度相对出口张力表现为正相关特点;以不同宽度的轧件进行测试发现轧机振动加速度保持基本恒定的状态。该研究对提高热轧轧机运行稳定性,对保证建筑结构钢板成形精度具有很好的指导意义,可以拓宽到其它的成形设备优化领域。

热轧钢板边部横纹缺陷分析

采用光学显微镜、扫描电镜对热轧钢板边部横纹缺陷进行分析,并将缺陷处酸洗前后与正常处平面、截面的位置形貌进行对比,利用能谱分析仪对缺陷处元素进行分析。结果表明:横纹缺陷处主要由氧化铁皮部分碎裂、剥落形成,其多数存在于氧化铁皮表层,氧化铁皮未全部剥落,氧化铁皮层与基体连接处还保留未碎裂的一部分,缺陷区域氧化铁皮结构主要为大量氧化亚铁和少量先共析四氧化三铁结构,属于易破碎氧化铁皮相。

取向硅钢热轧板中纤维织构及Goss织构的形成和演变

在热轧过程中,取向硅钢热轧板形成了不均匀的微观组织和织构梯度,其中热轧板表层和次表层中的Goss织构对取向硅钢的磁性能有重要影响。因此,热轧板微观组织和织构沿厚度方向的形成和演变,特别是Goss织构的形成,仍然是一个值得讨论的课题。为了研究热轧板组织和织构的形成及其演变,使用光学显微镜和扫描电镜(SEM-EBSD)观察了热轧板不同厚度层(表层、次表层和中心层)组织,研究了热轧板组织形貌沿厚度方向的演变,并使用XRD测量了热轧板各厚度层(从表层s=1到中心层s=0)的宏观织构。结果表明,在高剪切力的作用下,热轧板表层s=1形成了大量等轴晶粒(晶粒长宽比为1.0~1.5)和具有一定随机性的织构。表层以下,随着剪切力从表层向中心层逐渐减小,等轴晶粒(晶粒长宽比为1.0~1.5)占比逐渐降低,再结晶晶粒的晶粒长宽比沿着厚度方向逐渐增大,再结晶晶粒形状倾向于沿轧向延伸和呈不规则状。最后,在中心层s=0中,一些大尺寸再结晶晶粒的晶粒长宽比可以达到3.0~6.5。在压缩力和沿厚度方向逐渐减小的剪切力的共同作用下,热轧板次表层s=0.5~0.9形成由众多特定取向组成的纤维织构,而中心层s=0~0.4形成典型的α纤维织构,纤维织构中的一些典型的特定位向包括{100}〈011〉、{112}〈111〉、{110}〈112〉、{213}〈364〉、{441}〈104〉和{110}〈100〉Goss。热轧板次表层s=0.5~0.9中的纤维织构沿厚度方向逐渐演变,并且在次表层s=0.5中有稳定的Goss织构形成。然而,次表层s=0.5中形成的高强度的Goss织构,而次表层中形成的Goss织构只是纤维织构的一小部分。

基于深度学习的钢板表面缺陷识别方法及系统开发

在热轧钢板的生产过程中,由于工况的多样性,钢板表面难免会形成不同类型的缺陷。针对传统方法对钢板表面缺陷的识别准确率和效率较低的问题,提出了一种结合残差网络和迁移学习的钢板表面缺陷识别方法。首先,构建基于迁移学习的神经网络框架,同时采用全局平均池化和Dropout等优化策略增加网络的泛化能力,提高分类精度。其次,预处理钢板表面缺陷数据集,并通过钢板表面缺陷识别实验对模型性能进行检验。实验结果表明,基于迁移学习的网络模型在测试集上的识别准确率可以达到98.33%。最后,设计并开发了钢板表面缺陷识别系统,采用Power Designer软件构建系统的物理数据模型,并完成系统架构的设计,将训练好的神经网络模型应用到系统中,有效提高了钢板缺陷分类识别的智能化和信息化水平。

Comparison of microstructure and mechanical properties of titanium/ steel composite plates by two manufacturing processes

Two types of titanium/steel composite plates with the same thickness were manufactured by parallel explosive welding and double vertical explosive welding and rolling, respectively. The comparative analysis of microstructure showed that the interface of double vertical explosive welding plate （B plate） tended to be straight while the interface of parallel explosive welding plate （A plate） was wavy bonding. Defects near the interface of B plate were extruded, and the thickness of the diffusion layer of B plate was thicker under the effects of preheating temperature and press-working. Comparative tests of mechanical properties indicated that the tensile shear strength of B plate was lower while its micro-hardness was higher. Specimens of these two types of plates were neither separated nor cracked after bending up to 180° in the three-point bending test. From the microstructural observation of tensile fracture characteristics, A plate had strong toughness fracture while B plate had mainly ductile fracture with cleavage fracture as the supplement. Macroscopically, the tensile strength of the latter was 7.9% less than that of the former. However, both satisfied the Chinese standard of tensile strength.

热轧酸洗板边部麻面缺陷的形成原因及控制策略研究

针对首钢某1580 mm热轧生产线生产酸洗板时出现边部麻面后,影响了后续酸洗质量的问题,对边部麻面缺陷的形成原因及机理进行了研究。根据缺陷的形态、位置,对比卷取机设备的控制时序,确定了导致边部麻面缺陷的设备,并对上下表面的边部麻面缺陷的不同点进行了研究。结果表明下夹送辊辊面状况对边部麻面缺陷几乎没有影响,上表面边部麻面缺陷产生的主要原因是上夹送辊边部锈蚀严重,出现麻坑而导致的。而下表面麻面缺陷产生的主要原因是压紧辊下的机架辊边部锈蚀严重,出现麻坑而导致。为此,提出了相关的改进措施,以有效控制边部麻面缺陷,改善酸洗板边部质量。

Hot roll bonding between commercially pure titanium and high-strength low-alloy steel using Fe interlayer

Hot roll bonding was carried out between commercially pure titanium TA2 and high-strength low-alloy steel Q390 using no interlayer and Fe interlayer at temperatures of 850,900,950 and 1000℃with a total reduction ratio of 86.7%.Interfacial microstructure and bonding property of clad plates were investigated by electron microscopy and shear test.The results showed that with the increase in heating temperature,the shear strength of titanium clad steel plates decreases obviously.Compared with that of titanium clad steel plates with no interlayer,inserting Fe interlayer between titanium and steel can improve the shear strength at 850 and 900℃but deteriorate the shear strength at 950 and 1000℃.The reason for this consequence was that Fe interlayer prevented the reaction diffusion of C in titanium to form a thinner TiC layer at 850 and 900℃,while Fe interlayer promoted the reaction diffusion of Fe in titanium to generate thicker Fe2Ti and FeTi intermetallic compound layers at 950 and 1000℃.

Effect of hot rolling and cooling process on microstructure and properties of 2205/Q235 clad plate

The 2205/Q235 clad plate was fabricated by vacuum hot rolling with symmetrical assembling pattern of Q235/2205/2205/ Q235.The flow stress behavior and processing map of 2205 duplex stainless steel (DSS)were investigated by hot compressive tests on a Gleeble-3800 simulator.Then,thermal-mechanical coupled nonlinear finite element models of vacuum hot rolling and subsequent cooling process were established.From the simulation results,the influence of rolling reduction and rolling speed on hot deformation state of 2205 DSS in the assembled slab was disclosed and the optimal rolling parameters were presented.Meanwhile,the cooling rate of 2205 DSS under different cooling conditions and thicknesses of the clad plate was obtained.According to the numerical simulation results,pilot experiments were successfully carried out on a laboratory scale.The material universal testing machine,optical microscope,scanning electron microscope and energy-dispersive spectrometer were used to evaluate the mechanical properties and microstructure of bonding interface and 2205 DSS matrix for different rolling reduction and cooling processes.The results showed that with symmetrical assembling pattern,the approximate thermodynamic conditions can be established for 2205 DSS to avoid cracks in hot rolling process.When the rolling reduction increased from 10 to 40%,the shear strength of the bonding interface is increased from 120 to 530 MPa,and the uniform two-phase microstructure of 2205 DSS and satisfactory' mechanical properties can be obtained with cooling rate higher than 10℃/s between 1050 and 500℃ after rolling.

Descaling Behavior of 430 Hot-rolled Stainless Steel in HCl-based Solution

Descaling of hot-rolled stainless steel is generally implemented through pickling process in HNO_3-HF mixed acids,which induces severe environmental concerns of nitrogen oxide（NOx）gases and nitrites.According to the electrochemical measurement,the mass loss test and the appearance analysis,a new pickling process which employed HCl-based solution was proposed and evaluated to provide theoretical basis for the development of environment-friendly and highly effective pickling process.Under the experimental condition,the HCl-based solution can compete with ordinary HNO_3-HF mixed acids in terms of pickling efficiency,surface integrity and the removal of Crdepleted layer.The descaling process of 430hot-rolled stainless steel in the HCl-based solution consisted of three steps.The descaling solution penetrated the oxide scales into the underlying metal,dissolving the Cr-depleted layer and part of substrates.The oxide scales peeled off from the stainless steel and a polished and smooth surface was exposed.The descaled stainless steel was dissolved uniformly in the HCl-based solution;therefore,the pickling duration was vital for desired surface integrity.Under the static condition,the appropriate descaling time of 430 hotrolled stainless steel in HCl-based solution was 400 s.

盐酸基酸洗参数对SPHC热轧带钢的影响

采用光学显微镜、扫描电镜和能谱仪等分析手段,分析了SPHC热轧带钢氧化铁皮厚度和结构。此外,通过实验研究了酸洗参数以及抑制剂对SPHC热轧带钢表面质量的影响及其酸洗机理。结果表明:酸洗温度和再生酸浓度越高,越容易快速去除氧化铁皮,同时也更容易导致过酸洗现象。在80℃,207.89 g/L的再生酸溶液中加入0.5%的酸洗抑制剂,其酸洗腐蚀速率从5.00%下降至0.12%,缓释率高达97.51%,显著降低了试样的铁损,提高了带钢的表面质量。

SUS441不锈钢/Al金属间化合物微叠层复合板的界面结构与力学性能

采用“表面预处理—交替层叠—热轧复合—热处理”的工艺流程制备了SUS441不锈钢/Al金属间化合物微叠层复合板。利用光学显微镜、X射线衍射仪、扫描电子显微镜等检测与表征方法研究了热处理温度对复合板界面形貌、微观组织、物相组成、维氏硬度、拉伸性能的影响。结果表明:复合板界面结合良好;热处理后,固–液反应界面氧化严重,易导致界面分层而开裂;固–固、固–半固、固–液热处理后,金属间化合物层由均匀层和两相层组成,均匀层的物相组成为Fe_(2)A_(15),两相层的物相组成为Fe_(4)Al_(13)和Al_(13)Cr_(2),且两相层具有韧性特征,固–半固反应所得到的复合板的综合力学性能最佳。

酸洗汽车结构钢表面色差成因探究及工艺优化

针对酸洗汽车结构钢SAPH370表面出现的下表面条带状色差缺陷,通过光学显微镜、扫描电镜分析缺陷热轧基板氧化铁皮结构及酸洗后微观形貌可知,带钢表面粗糙度差异是造成表面色差的直接原因。结合热轧辊表面状态可知,下表面条带状色差缺陷产生的主要原因是精轧工作辊下辊比上辊辊面氧化膜剥落更严重,辊面状态的差异遗传至热轧基板,最终造成酸洗后表面粗糙度差异。通过优化轧制温度、轧辊换辊周期及轧制润滑工艺等,可以有效消除色差缺陷。

基于退火热处理的热轧钢板性能分析

为优化热轧钢板的晶粒结构,提升热轧钢板力学性能,采用退火热处理方法对热轧钢板进行性能分析试验。通过了解退火热处理的试验机理,确定热轧钢板试样成分并进行热试验处理,从冷却速度、温度、时间等方面对试样性能进行分析。结果表明:随着热轧钢板冷却速度及保温温度的升高,试样的屈服强度、抗拉强度也逐步升高,而低温冲击吸收能量及奥氏体晶粒度降低,铁素体组织略微粗化;880℃、900℃保温20 min后空冷的热处理工艺对提升热轧钢板性能有益,该工艺对热轧钢板工业生产有指导意义。

热轧板厚度对高牌号无取向硅钢磁性能的影响

基于高牌号无取向硅钢现场生产实验,将相同炉次的连铸板坯热轧至不同厚度(2.1,2.3,2.6 mm)的板卷,经常化均热工艺调控,获得晶粒较为均匀的常化板组织,再经85.7%~88.5%压下率冷轧,得到相同厚度(0.3 mm)的冷轧板,最终采用相同的退火工艺得到退火板;结合组织、织构和磁性能的相关检测分析,研究热轧板增厚对高牌号无取向硅钢产品磁性能的影响。结果表明:随高牌号无取向硅钢热轧板厚度的增加(在2.1~2.6 mm范围,即冷轧压下率降低),退火板组织中{111}晶粒占比提高,γ纤维织构强度逐渐增强,织构发生恶化;随热轧板厚度的增加,磁性能中铁损P_(1.0/400)线性增加,磁感强度B_(50)线性降低。热轧板厚度由2.1 mm增至2.3 mm时,P_(1.0/400)平均恶化0.20 W/kg,P_(1.5/50)平均恶化0.04 W/kg,B_(50)平均恶化0.005 T;热轧板厚度由2.3 mm增至2.6 mm时,P_(1.0/400)平均恶化0.24 W/kg,P_(1.5/50)平均恶化0.04 W/kg,B_(50)平均恶化0.009 T。