热轧钢板表面氧化铁皮缺陷观察及分析

用体视显微镜、金相显微镜、扫描电镜和能谱分析仪对热轧钢板表面常见的氧化铁皮缺陷进行观察,分析各种缺陷产生的原因。结果表明,麻点与凹坑都是由于硬质的氧化铁皮压入造成的。翘皮缺陷是由于残留的高温氧化铁皮压入表面,在后期轧制过程不能轧合而形成的。红色氧化铁皮缺陷主要发生于含Si高的特定钢种中,该缺陷主要是由于除鳞裂纹中断和生成剥离性差的Fe2SiO4造成的。纺锤状氧化铁皮缺陷是典型的一次氧化铁皮压入造成的,线条状氧化铁皮缺陷是二次或三次氧化铁皮压入造成的。     

SPHC冷轧基板常见表面缺陷及其原因

研究了冷轧基板SPHC钢常见表面缺陷及其形成原因。结果表明,冷轧基板常见表面缺陷有擦伤、翘皮、麻点和氧化铁皮压入等。擦伤缺陷是由于热轧板卷冷至常温后内圈松卷,在吊取、运输及开卷过程中发生层间错动形成的。连铸坯内部有气泡夹渣或其表面有缺陷,经轧制后沿轧制方向分布形成翘皮。麻点是在卷取过程中形成的,缺陷处晶粒在形变作用下发生了再结晶。氧化铁皮压入与除鳞设备及机间除尘系统的工作状态有关。     

高强度船板表面花斑缺陷的形成机制及改进措施

基于金相分析和气泡试验,分析了高强度船板表面花斑缺陷的形貌特征和微观组织,研究了化学成分、轧制工艺对花斑缺陷的影响。结果表明：花斑缺陷的形成原因主要是二次氧化铁皮在轧制过程中被压入钢板基体,导致钢板表面形成厚度差异较大的氧化铁皮,钢板抛丸后形成凹凸不平的斑状缺陷。通过降低钢中硅含量、优化高压水除鳞方式、低成本改进高压水除鳞系统,有效控制了高强度船板表面花斑缺陷。     

钢板表面翘皮缺陷常见原因分析

选取存在典型翘皮缺陷的钢板,利用SEM、EDS和金相显微镜对钢板表面翘皮缺陷的形成原因进行了分析。结果表明:呈条状分布的夹杂物、保护渣的卷入,氧化铁皮压入是引起钢板表面出现翘皮缺陷的主要原因。但是形成机理有所不同,夹杂物和保护渣作为裂纹源在轧制力的作用下逐步演化成的翘皮缺陷,而氧化铁皮的压入是由于残留的高温氧化铁皮在轧制力的作用下进入钢板次表层,使钢板不能被轧合而形成的。     

热轧超低碳钢典型表面缺陷成因分析

在某热轧厂生产的超低碳钢经常出现细条状和细沙状两种缺陷。通过对两种典型缺陷进行EPMA、SEM与EDS等分析,并结合现场的轧制工艺情况,对这两种缺陷的形成原因进行综合分析。分析结果表明,在两种缺陷附近未发现氧化圆点,缺陷都是在轧制过程中形成。细条状缺陷是由于Mn元素在氧化铁皮内富集,使氧化铁皮与基体的界面处凸凹不平,对氧化铁片产生"钉扎"作用;氧化铁皮的剥离性恶化造成除鳞时难除尽,残余的一次氧化铁皮在后续轧制过程中压入而形成。细沙状缺陷是由于F1~F3工作辊辊面氧化膜剥落,使辊面凹凸不平,在后续机架轧制过程中碾入带钢表面,造成三次氧化铁皮压入。并针对两种缺陷的成因提出了相应的防治措施。     

在线淬火中厚板表面氧化铁皮的控制与改善

钢板表面的氧化铁皮不仅影响产品外观质量,在轧制和矫直过程中还会导致氧化皮压入缺陷。采用控制轧制和直接淬火（DQ）工艺,研究了不同的淬火温度与终冷温度对低合金高强钢板表面氧化铁皮的影响,分析了钢板表面氧化铁皮结构及其脆化的原因。试验表明,通过增加除鳞道次并不能有效改善氧化铁皮,精轧轧制温度与轧后加速冷却过程对氧化铁皮结构具有显著影响,高冷速条件下通过降低精轧轧制温度与淬火温度,能够得到以FeO为主要成分的氧化铁皮,其具有良好的塑性并且分布均匀,避免了淬火后强力热矫直时氧化铁皮破碎并压入基体的问题,钢板抛丸后表面光洁。     

连退板表面白线缺陷成因和控制措施

针对首钢连退板表面白线缺陷问题,能谱分析发现白线缺陷内为海绵铁颗粒,且截面观察发现缺陷存在一定的压入深度,得出该缺陷是热轧卷表面的氧化铁皮压入所致。通过应用在线表检系统对问题卷表面进行反查,发现白线缺陷的热轧卷表面主要有3种类型氧化铁皮缺陷形貌,即条带状铁皮缺陷、西瓜皮状铁皮形貌、热轧机架共振造成轧辊氧化膜脱落形成的麻点形貌。针对此情况,对热轧工艺、轧辊氧化膜控制方法及热轧除鳞系统提出了优化措施,降低了连退板白线缺陷的产生。     

高NiCr轧辊轧制酸洗板表面质量提升探讨

本钢热轧产品氧化铁皮压入缺陷主要为辊系的氧化膜压入,酸洗后无法清除(图1).本钢热轧现场的工况是轧制过程F1～F4机架普通高Cr铁材质轧辊表面氧化膜脱落导致铁皮压入,理想状态下热轧酸洗板轧制主要依赖于高速钢轧辊,但是高速钢轧辊采购成本高,供应量不足,制约了酸洗板的轧制.另外高速钢轧辊对裂纹敏感,一旦产生裂纹,处理时间长...     

热轧酸洗板表面黑斑缺陷成因及机理研究

针对国内某钢厂生产的热轧酸洗板表面出现黑斑缺陷而严重影响后续酸洗质量的问题,对黑斑缺陷的形成原因及机理进行了研究。采用场发射扫描电镜和电子探针、X射线衍射仪、维式硬度计对黑斑缺陷的微观形貌、元素分布和相成分进行了分析,并对不同轧制工艺下残留氧化铁皮压入规律进行了研究。结果表明：黑斑缺陷部位与无缺陷部位氧化铁皮都为两层结构,但黑斑缺陷部位氧化铁皮更厚,并在交界处出现了“C”形厚度渐变趋势;黑斑内氧化层处Si元素以Fe₂SiO₄形式富集,Fe₂SiO₄对氧化铁皮产生钉扎作用导致除鳞困难,形成氧化铁皮压入缺陷,外侧更厚的Fe₃O₄层致使压入缺陷表面呈现黑色;在模拟残留氧化铁皮压入的实验中,残留氧化铁皮在粗轧和精轧温度下压入基体都会导致热轧板表面出现黑斑,随着压下率的增大,黑斑与基体结合会更紧密;黑斑缺陷表面微观形貌表现为氧化铁皮压入形式,并且表面硬度与残留氧化铁皮压入形成的黑斑表面硬度接近,都远大于基体硬度。出现黑斑缺陷的根本原因是Fe₂S...     

DC03冷轧基料表面氧化铁皮针孔缺陷的形成机理及控制

针对某企业在生产DC03冷轧板过程中,其热轧带钢酸洗后表面出现氧化铁皮针孔缺陷的问题,结合现场开展了理论和实验研究工作。首先对现场实物进行取样分析,认为在精轧过程中氧化铁皮被压入到带钢表面是造成氧化铁皮针孔缺陷形成的主要原因。为了进一步探究这一缺陷的形成机制,在实验室对DC03钢进行了温度为830～1 080℃的氧化动力学实验和氧化铁皮高温变形实验。结果表明：该钢的氧化激活能较低,在精轧温度范围内容易产生较厚的氧化铁皮,而且随着温度的升高,氧化铁皮中FeO所占比例提高,氧化铁皮的塑性改善。当精轧温度较低时,氧化铁皮破碎严重,氧化铁皮很容易被压入到基体中,形成氧化铁皮针孔缺陷,而随着轧制温度的升高,氧化铁皮的塑性逐步改善,当达到一定温度时,氧化铁皮能很好地随基体变形,使氧化铁皮保持相对较好的完整性。基于上述研究结果,针对现场实际,提出了适当提高轧制速度和严格控制终轧温度等改进措施,氧化铁皮的厚度及塑性得到有效控制,彻底消除了DC03冷轧基料氧化铁皮针孔缺陷。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.