Longitudinal surface cracks on continuous casting slabs of P and Cu containing container steel

The fact that the amount of the mold flux components differs at differentlocations on the cracking surface indicates that the longitudinal surface cracks are initiallyformed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductilitymeasurement of two typical container used steels, it is known that the steels are in severeembrittlement state in the temperature range of 825-775 deg C. By means of increasing Cr/Ni platingthickness on the upper part of the mold, reducing mold heat flux, adopting new secondary coolingpattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuouscasting) slabs has been significantly reduced.

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.

Corrosion of two kinds of cast steels containing chromium in hot concentrated alkaline

A typical hot concentrated alkaline corrosion environment exists in alumina metallurgical industry, so that steel materials with outstanding alkaline corrosion resistance are strongly demanded for its processing equipment. In this paper, the corrosion resistance of two kinds of martensitic cast steels containing chromium in static 303g/L NaOH alkaline solution at 85℃ was studied through polarization and potential-time curves, corrosion weight loss and corrosion morphology analysis. Experimental results showed that protection effect by passive film of cast steel containing Cr was temporary. The low carbon steel without Cr content also exhibited chemical passivity in the same solution. The corrosion mode of the tested Cr-containing cast steel was composed of active dissolving corrosion and caustic embrittlement cracking. Dissolving corrosion was the primary mechanism for the induced weight loss, while severe caustic embrittlement cracking was secondary. With the increase of chromium content in the cast steel, the tendency of the caustic embrittlement cracking decreased, while the active dissolving corrosion increased.

箱式钢结构集成模块建筑设计实践

雄安市民服务中心企业办公区采用箱式钢结构集成模块建筑体系进行建造,箱式钢结构集成模块具有建筑生产周期短、建造质量高、产品绿色环保等优点,技术成熟度较高,是一种比较彻底的工业化、标准化建造技术。本文从建筑结构布置、结构体系等方面对箱式钢结构集成模块建筑的结构设计进行了阐述,同时根据模块建筑的受力特点建立了简化模型,提出了结构计算过程中的计算假定,并采用两种不同的计算软件进行对比计算分析。本工程对模块建筑的连接节点进行了优化改型,根据改型节点进行了单调加载试验,研究连接节点的传力机理、节点刚度、抗剪、弯极限承载力和破坏模式,提供了必要的试验数据,为节点的理论计算模型与设计方法的提出奠定了一定的基础。

Operational efficiencies and costs of an arm roll forwarder: A case study at Nasu in Tochigi Prefecture, Japan

We investigated a developed arm roll forwarder at Nasu in Tochigi Prefecture, Japan. An arm roll forwarder can only load a steel container that has been fully loaded with logs beforehand, and can later unload such a container. Such a forwarder can shorten the loading and untoading times and improve operational efficiency. We examined two operation systems with an arm roll forwarder and a forwarder. In the first system the loading was done with a grapple-loader. In the second system the loading was done with a processor. The loading times of an arm roll forwarder were significantly tess than those of a forwarder. Because the optimal cycle times （excluding the waiting times for an arm roll for- warder） were significantly reduced, the costs of using an arm roll for- warder are lower, although the loading capacity was small and the hourly operation cost was high. The maximum operational efficiencies varied depending on forwarding distances. The second operation system with an arm roll forwarder exhibited the best operational efficiency within a 1,580-m forwarding distance, and beyond that distance it exhibited the highest operational efficiency when a forwarder was used. Similarly, the cost of operation of the system with an arm roll forwarder was the lowest within a 1,130-m forwarding distance, and beyond that distance the cost was the lowest when using the forwarder. Therefore, the arm roll for- warder is effective within a certain forwarding distance.

装配式打包箱式结构抗侧刚度及承载力分析

打包箱式结构是钢框架和轻质墙板组成的结构体系,利用打包箱进行模块化设计,具有可包装运输、组装灵活的优点。以三层驿站项目为例,利用多种计算软件,分别对单个打包箱和多个打包箱组合的抗侧刚度、极限承载力进行分析,并对三层一组、三层两组和实际工程的三层五箱体组合进行分析。分析结果表明:三层一组极限承载力及侧向位移均不满足规范要求,在进行打包箱模块化设计时应避免该组合。实际工程通过打包箱体的合理组合,可以提高结构的抗侧刚度和极限承载力,可以满足规范要求。多层打包箱体的模块化设计将打包箱组合模块化,可充分发挥打包箱结构灵活多变的特点,不仅形态多变,又满足结构受力、稳定性等要求。

钢制托盘箱在集装化运输中的应用

传统的货物运输模式在物流运输中存在少、慢、差、费等问题,不适应现代物流机械化高效作业的要求。钢制托盘箱这种新型集装化物流器具的推广应用解决了上述问题,其不同形式的上部结构可满足不同应用领域的物流储运需求,与不同的运载工具配合使用,载盘效率高,可实现最优的集装化运输。

Effect of Tempering Temperature on Microstructure and Mechanical Properties of Steel Containing Ni of 9%

Mechanical properties of quenching,intercritical quenching and tempering （QLT） treated steel containing Ni of 9% were evaluated from specimens subject to various tempering temperatures. The detailed microstructures of steel containing Ni of 9% at different tempering temperatures were observed by optical microscope （OM） and transmission electron microscope （TEM）. The volume fraction of austenite was estimated by XRD. The results show that high strength and cryogenic toughness of steel containing Ni of 9% are obtained when the tempering temperature are between 540 and 580 ℃. The microstructure keeps the dual phase lamellar structure after the intercritical quenching and there is cementite created in the Ni-rich constituents when tempering temperature is 540 ℃. When tempering temperatures are between 560 and 580 ℃,the reversed austenites （γ′） grow up and the dual phase lamellar structure is not clear. The γ′ becomes instable at 600 ℃. When tempered at temperature ranging from 500 to 520 ℃,the increase of dislocation density in the lamellar matrix makes both tensile strength and yield strength decrease. When tempered at 540 ℃ and higher temperature,the yield strength decreases continuously because the C and alloying elements in the matrix are absorbed by the cementite and the γ′,so the yield ratio is decreased by the γ′. There are two toughness mechanisms at different tempering temperatures. One is that the precipitation of cementite absorbs the carbon in the steel which plays a major role in improving cryogenic toughness at lower temperature. Another is that the γ′ and the purified matrix become major role at higher tempering temperature. When the tempering temperature is 600 ℃,the stability of γ′ is decreased quickly,even the transformation takes place at room temperature,which results in a sharp decrease of Charpy-V impact energy at 77 K. The tempering temperature range is enlarged by the special distribution of cementite and the lamellar structure.

Bainite Transformation of Low-carbon and Boron-containing Steel under Continuous Cooling

The effects of deformation temperature and strain on bainite transformation of low carbon steel and boron- containing steel were investigated under continuous cooling conditions by means of dilatometric measurement and mi- crostructure observation. The results show that with decreasing the deformation temperature from 1000 to 800 ℃ and increasing strains, bainite start temperature for boron-containing low carbon steel increases, whereas it decreases for low carbon steel under the same condition. The bainite microstructures are easily obtained for boron-containing steel deformed at different temperatures and different strains compared with plain low carbon steel. With increasing the continuous cooling rate, the bainite start temperature under deformed condition is about 20 ℃ higher than that under undeformed condition for boron-containing steel, but it changes slightly when the cooling rate is 20 ℃/s or more.

Effects of Temperature and Alloying Elements on γ Phase Fraction of Grain-oriented Silicon Steel

The effects of temperature and alloying elements on γ phase fraction of grain-oriented silicon steel,which contained 2.97-3.42mass% Si and 0.028-0.058mass% C,were studied by microstructure observation and statistics.Furthermore,the quantitative relationships of temperature as well as C,Si,and Mn contents to γ phase fraction were obtained by numerical fitting.The experimental results show that γ phase fraction firstly increases with increasing temperature,reaches a maximum and then decreases in the temperature range of 900-1 250 ℃.The temperature corresponding to the maximum γ phase fraction is about 1 150-1 200℃.Meanwhile,the γ phase fractions in steels at the same temperature have some differences because of different contents of various alloying elements.The verification results show that the values of γ phase fractions to C,Si,and Mn contents at the specific temperatures,which were obtained by multiple linear regression method,agree well with the measured values.In addition,the values of γ phase fractions to C,Si,and Mn contents in the temperature range of 900-1 250℃,which were obtained by binomial regression method,agree with the measured values when the contents of Mn and soluble Al are not more than 0.320mass% and 0.034mass%,respectively.The obtained equations can carry out the approximate prediction of γ phase fractions of grain-oriented silicon steels during the hot rolling process.

Combination Effect of Si and P on Tertiary Scale Characteristic of Hot Rolled Strip

For high strength interstitial free （IF） steel containing P element, the salt and pepper （SP） defects exist on the strip surface and could not be eliminated effectively by optimizing the hot rolling process, such as temperature and cooling water. The combination effect of Si and P on the characteristic of tertiary scale has been studied comprehensively by scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）, and the concept is proposed firstly that Si and P are of combination effect which can be utilized to eliminate the SP defect. The results show that the SP defects were induced by the rolled-in scale during finish rolling. P can be enriched at the interface between substrate and tertiary scale, which is easy to decrease the adhesion of tertiary scale. However, Si enrichment at the interface between substrate and tertiary scale can increase the adhesion. The SP defects can be eliminated completely, which is attributed to the accompanying enrichment of Si and P.