热镀锌铁合金双相钢漏镀缺陷机理分析及改进措施

针对某冷轧厂生产的双相钢边部存在漏镀缺陷的问题,对漏镀部位的缺陷形貌和成分进行了分析,结合高强双相钢选择性氧化原理对现场的相关影响参数逐个进行剖析、识别,确定出各个参数的控制范围,随后通过试验设计得出了关键控制参数的最佳组合,并针对性制定了控制措施。结果表明：锌铁合金双相钢的漏镀缺陷是由于炉内气氛控制不好,锰、铬等合金元素扩散到表面出现选择性外氧化导致的;在保证性能的前提下,在Ac₁线以上适当降低退火温度,有利于内氧化的形成;炉鼻子气氛控制要加强对加湿器的管理,一旦加湿过大就会引起炉鼻子处露点过高,导致冷区氧含量过高,造成已还原的金属出现二次氧化;通过采取热区温度770～790℃,加热区露点-10～15℃,炉鼻子氧体积分数小于0.001 0%,锌铁合金双相钢的漏镀缺陷率由改善前的8%大幅下降到1.42%,且缺陷主要集中在带钢头部位置,优化效果明显。     

冷轧DP780冲压脱锌原因分析

热镀锌双相钢因具有一系列优异性能而得以在汽车车身轻量化和提高零部件安全性的生产中广泛应用。热镀锌高强度双相钢的可镀性问题是生产高质量表面镀层钢板的关键问题之一,而提高可镀性的基本方式是减少表面氧化物生成,从而抑制合金元素表面富集。文章针对冷轧镀锌DP780高强钢冲压脱锌质量问题进行成分和电镜对比分析,研究发现脱锌卷抑制层不均匀连续,局部存在合金元素富集氧化。分析表明其根本原因在于退火炉中露点控制不佳导致局部合金元素富集氧化,影响抑制层的均匀连续性。通过合理控制露点,抑制层均匀性得到改善,冲压脱锌问题得到解决。     

合金化热镀锌C-Mn高强钢漏镀缺陷原因分析及其对策

针对合金化热镀锌C-Mn高强钢漏镀缺陷问题,利用扫描电镜(SEM)、能谱(EDS)分析了漏镀缺陷原因,阐述了缺陷形成的机理。结果表明:退火炉加热区的氧分压过低,引起Mn、Si等合金元素在基体表面的外氧化显著,降低了钢基体的浸润性;带钢入锌锅温度较高,加快了镀层的合金化反应进程,加剧了Fe-Zn之间的相互扩散,且由于氧化物覆盖不均匀,氧化物密度高的地方容易产生漏镀点。在实际生产中,通过降低退火炉加热区的氢气含量和带钢的入锅温度、提高锌锅自由Al含量等措施,C-Mn高强钢的合金化镀层表面漏镀缺陷得到了有效改善,质量合格率由原来的75%左右提高到了91%以上。     

590 MPa级低合金高强度热镀锌钢板表面亮点缺陷分析

采用SEM、EDS分析了590 MPa级低合金高强度热镀锌钢板表面亮点缺陷的形貌及成分。结果表明,低合金高强钢中合金元素选择性氧化析出的颗粒物尺寸较小时,可以被Zn液中Al完全还原。对比正常位置,析出物颗粒位置没有形成完整致密的Fe₂Al₅Zn_x抑制层,在后续热镀锌过程中,该位置Zn-Fe反应扩散快,镀层生长厚。光整时,该位置形成的压缩片状结构相互连结,宏观表征为表面亮点缺陷。通过降低炉内露点可以抑制低合金高强钢表面合金元素外氧化,进而防止镀层表面亮点缺陷产生。     

退火气氛露点对3种成分体系双相钢选择性氧化的影响

以C-Mn-Si、C-Mn-A1-Cr和C-Mn-Cr-Si 3种成分体系的双相钢为研究对象,采用连续退火模拟试验研究了退火气氛露点对钢板表面合金元素选择性氧化的影响.使用辉光放电发射光谱分析了退火试样表面元素深度分布,使用扫描电镜观察了试样表面外氧化及截面内氧化形貌.结果 表明,露点对3种成分体系的双相钢合金元素选择性氧化的影响趋势一致,即露点升高后,合金元素外氧化均减少,内氧化增加.Si、Al、Cr 3种合金元素对C、Mn含量基本相同的双相钢表面的选择性氧化有不同的影响.露点-40℃退火时,含Si的C-Mn双相钢中的Mn和Si元素会同时在次表层形成少量内氧化;含Al的C-Mn双相钢仅在次表层形成Al的内氧化,从而形成了更严重的Mn元素外氧化.但当露点达到0℃及以上时,含Al的C-Mn双相钢Mn元素外氧化更少,Cr元素和Mn元素的内外氧化趋势较相似.     

先进高强钢板可镀性及内氧化模型研究进展

先进高强钢中含有大量的Si、Mn等合金元素,这些元素在退火时会扩散到钢板表面并氧化,所产生的表面氧化物降低了锌液对钢板的浸润性,影响了镀锌产品的质量。本文介绍了先进高强钢板可镀性及内氧化数学模型研究的进展,通过改变基体的化学成分、退火气氛的露点和H2 N2比例,将影响钢板可镀性的合金元素氧化控制为内氧化,改善了钢板的可镀性。     

热镀锌DP钢表面析出缺陷的分析与研究

双相钢，又称DP钢，因其成分中含有Si、Mn等亲氧的金属元素，导致在生产中容易与氧发生反应，致使产品表面形貌变差。本文从原理上简述了本钢某镀锌机组生产双相钢时，表面产生析出缺陷的原因，并从原理出发进行试验，并将试验结果应用于生产中，取得了较好的效果。     

热镀锌板钝化膜黑斑缺陷分析及控制

通过使用金相显微镜和扫描电子显微镜对镀锌钢板出现的钝化膜表面黑斑缺陷进行微观分析,认为黑斑形成的原因主要为镀锌板生产过程中拉矫机挤干辊未能将带钢表面的水分挤干并完全烘干,在后续钝化处理时带钢局部残留的水分造成钝化膜被水稀释而产生漏涂点,在钢卷运输和仓储过程中,带钢表面的钝化膜漏涂点部位氧化而产生黑斑缺陷。通过严格控制挤干辊运行状况、提高热风烘干温度至110 ℃后,未再出现类似钝化膜黑斑缺陷。     

热镀锌双相钢表面色差问题的分析

高强度级别热镀锌双相钢产品中合金元素添加较高,在退火过程中表面质量难以控制,经常遇到各种表面质量缺陷。文章针对热镀锌过程中出现的边部色差缺陷进行了分析。通过电镜分析认为色差缺陷是由于表面的粗糙度不同,光滑的表面对光产生镜面反射,肉眼看上去发亮,粗糙的表面对光产生漫反射,肉眼看上去发暗,表面发暗部位的表面粗糙度值较高、抑制层形成不良,造成锌层不均。通过相同的镀锌工艺可以发现,材料在色差缺陷位置存在明显带状组织,这是因为原材料存在热轧遗传,可以采用较大的冷却速度和较低的卷取温度来控制热轧组织的整体均匀性、消除热轧过程的不利影响。     

不同退火工艺对含Mn钢的浸润性影响

传统镀锌工艺已经相对成熟,但高强度的热镀锌产品仍存在很多问题。为适应汽车轻量化所需的高强镀锌基板,由于合金元素含量的增加,会对后续热镀锌产生不良影响。文章针对不同退火工艺对含Mn钢的可镀性影响进行了研究。采用自主开发的实验室模拟镀锌设备分析了Mn含量、退火时间、退火温度工艺参数对钢基表面氧化物的影响。实验表明,在热镀锌退火过程中,钢基中Mn元素会在钢基表面富集形成氧化物,同时随着退火温度的增高、退火时间的延长,表面氧化物数量明显增加。     

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.