Microstructure and corrosion resistance of 304 stainless steel electroslag strip cladding

The 304 stainless steel strips were deposited one layer on carbon steel base metal by electroslag strip cladding （ESC） and submerged arc cladding （SAC）, respectively. The solidification microstrueture of ESC metal was analyzed by the optical microscopy, scanning electron microscope and energy dispersive spectroscopy. The corrosion resistance studies of strip cladding metals were carried out in 10% oxalic acid electrolytic etching test. The results showed that the cladding metal obtained by ESC presented low content of C, high content of Cr and enough alloying element of Ni in the chemical composition. The transition zone of ESC with small width was almost parallel with the base metal, leading to a lower dilution. There are three types of solidification modes （ A→AF→FA ） occurred in the ESC metal due to the decrease of cooling rate and degree of dilution from the transition zone to the top of ESC metal. As a result, the microstructure of ESC metal exhibited mainly austenite with a small amount of ferrite, contributing to achievement of better corrosion resistance.

Microstructure analysis of AISI 304 stainless steel produced by twin-roll thin strip casting process

The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope （TEM）, and X-ray diffraction （XRD）. The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vo1% at the center and 6.77vo1% at the surface of the casting thin strip, in vermicular and hand shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of MnO.Al2O3, 2FeO.SiO2, and 2MnO.SiO2. Many defects including dislocations and stacking faults have also formed during the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.

Microstructure of AISI 304 stainless steel strips produced by a twin-roll caster

By optical inspection of macro-etched metallography and electron back-scattered diffraction （EBSD） mapping, this paper analyzed the microstructure of austenitic stainless steel strips produced with an equal-diameter twin-roll strip caster. The results indicate that the microstructure of the strips includes two columnar zones with highly compact dendrites and one equiaxed zone. The characteristics, such as grain size and growing direction of columnar grains and equiaxed grains, were investigated. An additional transitional area with many finer grains between the columnar zone and the equiaxed zone was found. As shown in EBSD analysis, small angle boundaries exist both in the columnar zone and the equiaxed zone, although they are especially more in the transitional area. Additionally, some 〈111〉 twin boundaries were found in the microstructure of the strips.

Research on directly cold-rolled AISI 304 stainless steel strip with the twin-roll strip casting process

In order to improve the surface quality and properties of AISI 304 stainless steel strip produced with the twinroll strip casting process,the strip was directly cold-rolled. The results show that cold rolling clearly improves the surface roughness,microstructure and properties. Residual δ ferrite is greatly decreased, anisotropy becomes less obvious and corrosion resistance is greatly improved. These results demonstrate the feasibility of directly cold-rolled AISI 304 stainless steel strip.

06Cr13不锈钢带酸洗色差成因及控制措施

针对06Cr13酸洗过程中发现的表面色差缺陷进行形貌比对和工艺追溯,发现该缺陷产生的原因是钢带表面氧化皮厚度不均和酸浓度、温度控制不合理。为改善酸洗色差缺陷,通过优化铸坯加热与除磷工艺、强化破鳞与抛丸工艺、细化酸洗工艺与生产组织、加强设备管理与控制,06Cr13酸洗板色差缺陷得到有效控制。

直升机复合材料拉扭条扭转性能分析

拉扭条作为直升机旋翼桨毂的主要承力结构,承受桨叶旋转产生的离心力并通过自身的大变形实现桨叶的变距,其所承载的离心力和扭角变形随直升机飞行状态的变化而变化。针对复合材料拉扭条组件,基于ABAQUS建立仿真模型并求解应变和角度变形云图;设计静力试验台架进行验证试验来验证仿真模型,并进一步分析离心力、扭角对其扭转性能的影响。结果表明:复合材料拉扭条的扭转刚度随扭角的增大而减小,随离心力的增大而增大,且离心力对复合材料拉扭条的扭转刚度影响更大。

3D stress simulation and parameter design during twin-roll casting of 304 stainless steel based on the Anand model

This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520℃, respectively.

EUROSTRIP~不锈钢和带钢连铸技术

EU ROSTRIP○R技术在带钢连铸生产领域稳居领先地位。介绍了 EU ROSTRIP○R联合开发计划及相关欧洲网络。以所达到的产品质量结果为重点 ,描述了碳钢和不锈钢中间试验厂和预工业试验厂以及研究开发工作的经验。

Inclusion and its deformation behavior in 304 stainless steel

Non-metallic inclusion is the main reason for the presence of surface defects in cold-rolled steel strip. In this study, the composition, morphology, and size of the non-metallic inclusion in hot-rolled 304 stainless steel strips are analyzed. Cold-rolled 304 stainless steel strips with different cold-rolling reduction have been prepared, and the morphology and size of inclusion in these cold-rolled strips are also analyzed. Furthermore, the deformation behavior of a non-metallic inclusion during the cold-rolling process is studied. The results show that CaO-SiO2- MgO-Al2 O3, a kind of brittle compound oxide,is the main type of inclusion in hot-rolled 304 stainless steel strips. During the cold-rolling process, ductile deformation of this type of inclusion is not obvious, where large inclusions are crushed, and the average size of inclusions in cold-rolled strips decreased while the cold-rolling reduction increased.

Researches on the problems in the production of low nickel austenitic stainless steel

Problems encountered in the production of low nickel austenitic stainless steel have been studied. These problems primarily include the changes to the microstructure of the slab during the heating process, the formation and removal of deformation - induced martensite during cold rolling, and the effects of the annealing process on the surface oxide structure. A reasonable manufacturing process has been proposed on the basis of the research results and high-quality cold-rolled strips of low nickel austenitic stainless steel have been produced.

SUS304极薄带拉伸过程中的褶皱试验

针对不锈钢极薄带在弹塑性拉伸过程中出现的褶皱现象,对数字图像相关技术采集的厚度为0.02 mm的SUS304极薄带拉伸试验数据进行了分析,探讨了褶皱形成机理。结果表明,SUS304极薄带产生纵向褶皱主要是由横向应变超过10.104%时,两侧产生的内部横向压应力促使试样向中间挤压运动导致的。其表面不断有新褶皱产生,原有褶皱不断向两端扩展变化,皱曲程度加深,表面褶皱数量不断增多,纵向褶皱纹理越加明显,且纵向褶皱波长远大于波峰到波谷的垂直距离;SUS304极薄带拉伸断裂形式为从边部撕裂并逐渐向内扩展。

超声振动辅助SUS304薄带塑性变形的Johnson-Cook本构模型

通过超声能场辅助SUS304薄带拉伸试验发现,薄带塑性变形过程中的流动应力明显下降,体现了超声的软化效应。硬化指数和硬化系数随着超声能量的增加呈指数增加,且伸长率也发生了明显的下降,说明超声能场的加入对材料产生了硬化作用。相较于常规拉伸,施加超声能场后薄带的应变速率也发生了明显的提升,说明超声提高了薄带的应变速率敏感性。基于Johnson-Cook本构模型,建立了超声能场作用下SUS304薄带塑性变形的本构模型,用于定量分析超声能场振幅对SUS304薄带塑性变形的影响。

脉冲电流对T2纯铜/304不锈钢复合薄带变形性能与组织的影响

为了研究脉冲电流大小和频率与T2纯铜/304不锈钢复合薄带的强度和延展性等力学性能之间的关系,通过冷轧结合450和970℃两种温度的退火工艺制备了软硬两种状态的复合薄带,并分别对其进行了脉冲电流辅助单向拉伸试验。通过微观组织与断口形貌观察分析了复合薄带变形机制与脉冲电流的作用机理。结果表明,脉冲电流会引起复合薄带的软化,同时导致伸长率降低。当频率不变时,随着电流的增大,纯铜/不锈钢复合薄带的软化与伸长率降低的现象愈加显著;但电流一定时,改变频率对软化效果影响并不明显。脉冲电流对复合薄带性能的影响源于其对钢侧变形协调机制的调控,通过抑制奥氏体的孪生与相变过程降低了复合薄带整体变形抗力。拥有奥氏体再结晶组织的软态复合薄带表现出的软化现象比拥有轧制变形组织的硬态复合薄带更加显著。

430铁素体不锈钢冷轧带钢表面黑带缺陷分析

采用扫描电子显微镜(SEM)及能谱分析(EDS)等方法对冷轧带钢表面黑带缺陷和连铸板坯表层碳化物的形貌、尺寸及分布进行了分析研究。结果表明:430不锈钢带钢表面黑带缺陷部位较正常区域有更高的碳含量,且出现贫铬元素,为明显的晶间腐蚀缺陷。分别使用A型和B型保护渣的430不锈钢铸坯边部和中部表层均存在颗粒状碳化物,碳化物区域深度不同,呈不连续的分布。因此,由于结晶器液面波动或保护渣熔速过慢导致熔渣层补充不足,富碳层与钢液和铸坯表面接触,造成铸坯表面覆碳,在后续轧制过程形成黑带缺陷。

不锈钢冷轧带钢质量智能管控的探索与实践

为快速提升不锈钢冷轧带钢质量水平,探索了一种智能的不锈钢冷轧带钢质量管控方法,并通过信息化系统予以实践。系统建设内容包括:采集不锈钢冷轧带钢全工序质量数据,构建质量数据中台;根据不锈钢冷轧钢带各工序质量管控特点建立单工序、多工序质量监控及判定模型;搭建质量多因素数据追溯和分析模型。结果表明:不锈钢冷轧带钢质量智能管控系统不仅能够对全流程过程质量进行自动判定、封锁和SPC监控,同时可进行质量追溯与分析;与传统质量管理相比,智能质量管控系统具有自动、精准、高效等优势。

CAP1400型非能动余热排出热交换器支撑组件的关键制造工艺

非能动余热排出热交换器的换热管束通过不锈钢支撑框架以及管束支撑组件精确固定,但是不锈钢材质线膨胀系数高、导热率低,焊后易产生收缩变形造成管束支撑组件位置偏移,影响换热管在框架内侧的精确安装。CAP1400型核电机组是我国在现有AP1000型压水堆核电技术基础上改进研发的新型压水堆核电机组,由于新机组总体尺寸规格有所增大,焊接收缩和变形趋势更明显,更难以满足关键设备的焊接与定位精度要求。为此对新机组中换热管束支撑框架的结构和制造工艺进行详细研究,改进和优化了H型钢的焊接制造工艺和坡口加工工艺,有效降低H型钢组装时的误差。针对焊接变形问题,提出反变形支撑及水冷却方法,防止支撑框架中各部分型钢变形;提出管束支撑组件精准定位方法,实现了管束支撑组件在框架内的精准定位安装。实践证明,用上述改进与优化的工艺和提出的方法能够大大提高支撑框架的制造精度,达到换热管在支撑框架内的顺利引入以及与管板管孔精准对接的效果。

不锈钢带极埋弧堆焊防剥离工艺优化研究

对不锈钢带极埋弧堆焊层进行热模拟试验,研究高温停留时间对堆焊层过渡区硬化层厚度的影响,用剪切试验检测不同硬化层厚度条件下的界面结合强度,用焊接数值模拟分析堆焊层数对界面残余应力的影响。研究结果表明:随着高温停留时间增加,堆焊层过渡区硬化层厚度增大,堆焊层与母材的结合强度降低。随着堆焊层数的增加,界面残余应力增大,堆焊层数达到6层残余应力为380 MPa。较小的热输入、较低的预热温度和层间温度、较少的堆焊层数,可以减小不锈钢带极埋弧堆焊过渡区硬化层厚度,提高堆焊层与母材结合强度,降低堆焊层界面残余应力,防止堆焊层剥离。

酸性水汽提塔顶安全阀入口管线腐蚀原因分析及对策

针对国内某石化公司煤制氢部酸性水汽提塔顶管线腐蚀的问题,本研究以酸性水汽提塔顶安全阀入口管线腐蚀穿孔泄漏为例,通过对酸性水汽提塔顶安全阀入口管线腐蚀原因调查,通过宏观与低倍分析、材质分析、金相检验、电镜分析等多项理化检验分析,认为造成安全阀入口管线减薄穿孔的主要因素是由铵盐垢下腐蚀及管线内酸性水/气的冲蚀和空蚀相互作用造成的。根据结论,采用多项措施解决腐蚀问题,从而有效减小腐蚀,提高酸性水汽提塔顶管线的使用寿命,保证装置的长周期安全生产。

不锈钢冷轧带钢脱脂工艺的应用

介绍不锈钢冷轧带钢表面油污的种类及性质,分析脱脂工艺机理。以某不锈钢冷轧带钢脱脂工艺流程为例,分析影响脱脂清洗效果的因素,指出加强脱脂效果的方法。

一种冷连轧机抽断带预警系统的开发

随着自动化控制水平的提高,连续式轧制被广泛地引入不锈钢轧制生产。连续轧制具有生产效率高、连续性强的特点,与前后工序衔接紧密,因此抽断带类事故对于连续式轧制影响严重。通过对抽带原因分析,从原料、装备、操作三个方面找到了避免抽断带的关键因素。经过现场观察,发现带钢跑偏量可以表征抽带可能性,通过对带钢跑偏量的实时监控,实现了对带钢跑偏的预测。同时,通过控制轧制速度,来避免抽断带事故。课题组将控制思路固化到L1级控制系统后,抽断带事故得到了有效控制。