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 different locations on the cracking surface indicates that the longitudinal surface cracks are initially formed in the mold and are enlarged in the secondary cooling zone. Based on the hot ductility measurement of two typical container used steels, it is known that the steels are in severe embrittlement state in the temperature range of 825-775℃. By means of increasing Cr/Ni plating thickness on the upper part of the mold, reducing mold heat flux, adopting new secondary cooling pattern, etc., the occurrence of the surface longitudinal cracks on the steel CC (continuous casting) slabs has been significantly reduced.     

影响亚包晶钢铸坯表面纵裂纹的因素研究

采用金相、扫描电镜、连续测温等方法对亚包晶钢铸坯表面纵裂纹产生原因进行了系统研究,研究结果表明:当钢水过热度35℃和15℃浇铸时,铸坯表面纵裂纹发生率明显提高;随着拉速的增加铸坯纵裂纹发生率呈上升趋势;在同一拉速条件下,铸坯内弧比外弧更易于生成凹陷和裂纹;结晶器铜板热流密度不均是铸坯纵裂纹产生的主要原因,并在二冷区进一步扩展。     

SS400钢板表面纵裂纹分析及实验研究

针对SS40钢板在生产过程中产生的表面纵向裂纹现象进行研究与分析.结果表明,钢板表面纵向裂纹大部分分布在钢板宽度方向的2个1/4区域内,裂纹的长度一般在0.5~2 m,宽度均小于1 mm,深度为0.1~0.2mm.进一步分析后认为,该种表面缺陷产生于连铸结晶器内,在随后二冷区的强冷和加热炉的加热过程中,裂纹得到了进一步的扩展.     

EH36钢连铸坯角部横裂热模拟试验研究

针对某钢厂EH36钢300 mm厚连铸板坯的角部横裂问题,应用Gleeble—3800热模拟试验机研究了EH36钢的缺口试样在结晶器与二冷矫直区分别产生裂纹的差异.研究表明,结晶器产生的裂纹特征与二冷矫直区产生的裂纹特征在氧化程度上有着显著差异,据此可以判定EH36钢300 mm厚连铸板坯的角部横裂产生位置,为调整工艺参数提供参考.     

预应力混凝土桥底板纵向裂缝控制

为了减少预应力混凝土桥梁纵向裂缝的危害,研究和对比了中国规范（JTG D62 2004）、欧洲规范（ENV1994 2：1997）、英国规范（BS 5400 4：1990）和美国规范（AASHTO LRFD Bridge Design Specifications SI Units Third Edition 2004）中的相关条款,提出通过控制名义拉应力来控制预应力混凝土桥底板纵向裂缝的方案.某全比例模型试验被用于验证分析,其结果很好地验证了方法的可行性.研究结果表明,对于采用全预应力标准设计的桥梁结构,应采用控制名义拉应力的方法避免其纵向裂缝的产生,如无法布置横向预应力,则应积极采取构造措施来限制裂缝的宽度,使其最大宽度不超过0.10mm.     

钢筋混凝土锈胀效应的模拟实验研究

通过油压模拟钢筋锈胀力实验,得到了当混凝土表面产生顺筋裂缝时所对应的油压值.由于采用的实验模型与实际钢筋非均匀锈胀效应具有一定的相似性,因此所得到的油压值能够近似地反映出实际的钢筋锈胀力.在混凝土表面所产生的顺筋裂缝证明了锈胀裂缝最终是在混凝土保护层的正上方.     

Solidification and crystallization properties of CaO-SiO2-Na2O based mold fluxes

Crystallization properties play an important role in keeping a smooth running of continuous casting process and high sur-face quality of cast strands. To reduce fluorine pollution in slag, a new type of CaO-SiO2-Na2O (CSN) based mold flux was studied. The solidification and crystallization properties, including crystallization temperature, crystallization ratio and solidification minera-graphy, were measured, which were compared with the CaO-SiO2-CaF2 (GF) mold flux. The results show that the crystallization performance is equal to the high fluoride mold powder and CSN can be used for peritectic steel grades sensitive to longitudinal cracking in continuous casting.     

Research on mold flux for hypo-peritectic steel at high casting speed

Mold fluxes having adaptable properties were developed in the laboratory to solve quality defects, such as depressions and longitudinal cracks when casting hypo-peritectic steel at high casting speed. Firstly, the effect of components on the high basicity mold flux properties was first studied using the orthogonal method. In the scope of the studied content, Li2O has the largest effect on the melting temperature, and the least effect on the viscosity; CaF2 has the largest effect on the viscosity, and the least effect on the melting temperature; Na2O and CaO/SiO2 have no obvious influence on the melting temperature and viscosity. Secondly, two powders (Z1 and Z6) have reasonable viscosity-temperature curves, higher solidification temperatures, and porous structure after solidification, but the crystal property of Z6 is worse than that of Z1, and thus Z1 is more suitable for continuous casting hypo-peritectic steel at high casting speed. Thirdly, a higher basicity of powder, a less free enthalpy of crystal compound, and a lower baffle energy are good for a higher tendentiousness of crystal.     

薄板坯和常规板坯生产冷轧产品的质量比较

作为生产冷轧产品的原料,薄板坯热卷与常规板坯热卷相比,薄板坯热卷在纵裂纹缺陷、屈服强度和屈强比等方面控制更加困难.论述薄板坯热卷原料纵裂纹缺陷和机械性能对生产冷轧产品的衍生影响,比较同一罩式退火条件下,分别以薄板坯连铸连轧工艺和常规板坯工艺生产的IF钢热卷作为原料冷轧IF钢的性能,两者屈服强度相差30MPa左右.     

倾斜煤层开采相似材料模拟实验

为了研究倾斜煤层开采引起的地表移动与变形规律,探讨了相似材料模拟实验的观测方法与原理,通过对观测数据的分析与处理,求得观测线沉降曲线与水平位移曲线,运用Excel的函数计算得出变形曲线,最终在6号点和7号点之间纵向方面出现近水平裂缝,在横向方面产生显著的高角度裂缝,所得结果为煤矿的安全生产提供了科学依据。     

预应力雁形板屋盖纵向开裂和挠度分析

采用有限元法对雁形板屋盖结构的空间受力特性进行了分析计算，并着重考虑了温度变化对板截面应力的影响。计算结果表明，温度上升在肋梁附近的翼板下部将产生超过混凝土抗拉强度的拉应力，导致雁形板沿纵向开裂，形成贯通板全长的纵向裂缝。同时，建立了裂缝形成后的计算模型进行板的挠度分析计算，计算结果和实际变形相一致。     

二灰碎石基层产生纵向贯通性裂缝的原因分析

津涞公路二灰碎石基层K3 000~K37 504段建成一年左右出现了长距离纵向贯通性裂缝,这些裂缝不是出现在新旧路接缝处,也不是由于路基不均匀沉降而引起的,已有的国内外文献都不能够解释产生这些裂缝的原因.通过对道路纵向贯通性裂缝的试验研究和理论分析,找出了产生纵向裂缝的主要原因,提出了切实可行的防止措施,为今后的道路工程设计、施工提供了重要的参考依据.     

Quality control for bloom casting of YQ450NQR1 steel

To reduce surface depression of a bloom,the primary cooling intensity was decreased,and the water distribution of mold wide and narrow faces was optimized.The length of secondary cooling zones and the specific water flow were increased,and the water flow distribution among the secondary cooling zones was adjusted to eliminate central defects,such as center looseness,central segregation,and center line cracks.The operation showed that the proportion of surface depression decreased from 37.22% to 2.87%,whereas the proportion of center looseness for < 1.0 increased from 79.71% to 90.70%,the proportion of central segregation for <0.5 increased from 1.45% to 44.19%,and the proportion of center line cracks that are flee increased from 39.13% to 62.79%.The quali-fied blooms are delivered to produce 310 Z-beam,whose yield strength is greater than 450 MPa.     

瞬变电磁对含水层的超前探测效果分析

在隧道开挖过程中,掌子面前方多存在充水、充泥断层或裂隙等地质病害体形成的含水夹层.基于等效导电平面法基础上的视纵向电导二次微分成像方法,利用“H”型地电模型理论得到含水夹层的视纵向电导微分成像响应特征和识别方法,提出视电阻率和视纵向电导相结合进行含水夹层的探测方法,以此来指导瞬变电磁法在隧道内的超前地质预报工作,提高了瞬变电磁探测的精度及准确度.     

Macroscopic and microscopic fracture features of concrete used in coal mine under chlorine salt erosion

The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.     

无粘结预应力混凝土连续板边中两跨受火试验

为了搞清火灾情况下无粘结预应力混凝土连续板的受力、变形、裂缝分布形式以及破坏机构等与常温下有什么不同,为对其进行抗火设计奠定基础.对3块12.6m×1.5m三跨连续板在边中两跨受火下的火灾行为进行试验研究,试验过程中采用ISO834标准升温曲线,并施加2.0kN/m2的使用荷载.试件主要考虑负弯矩筋长度的变化和预应力度.用位移传感器测量板的变形,用压力传感器测试支反力及预应力的变化情况.试验结果表明:裂缝形式主要有板顶斜裂缝、横向贯通裂缝以及沿预应力筋的纵向裂缝,未受火跨在试验过程中未发现任何肉眼可以观察到的现象.试验发现负弯矩筋长度决定了横向贯通裂缝出现的位置.预应力先增长后减少,最后预应力筋多被拉断.火灾情况下,无粘结预应力混凝土连续板的变形和内力重分布远比常温情况剧烈,裂缝分布形式以及破坏机构明显不同于常温,预应力损失严重.     

DBQ3000型塔机主臂杆纵向闭合裂纹强度的研究

用SQCE理论,对DBQ3000型塔机主臂杆母材非接头和接头部位存在的纵向闭合裂纹进行了分析计算,圆满地解决了先天性表面纵向闭合裂纹对塔机主臂杆强度和寿命的影响问题。对含裂纹构件的安全评定做了新的尝试。     

J积分在非均质焊接接头裂纹问题中的应用研究

本文用弹塑性有限元方法，对焊缝区纵向裂纹和横向裂纹做了大量Ｊ积分计算，研究了焊缝区中非均质组合结构裂纹的Ｊ积分的守恒性，分析了焊缝区硬夹层宽度大小对整个组合体Ｊ积分数值的影响，为建立焊缝区中裂纹的Ｊ积分失效评定曲线，提供了可靠的依据。     

CFRP加固钢筋混凝土整体式板桥的受力性能研究

为研究粘贴碳纤维布对在役钢筋混凝土桥梁受力性能的改善效果以及对已有裂缝的抑制能力,结合某具有较大纵向裂缝变截面连续整体现浇混凝土板桥的损伤特点,介绍了碳纤维布加固该类桥梁的设计要点．分别进行了加固前后的对比性荷载试验,试验结果表明,粘贴碳纤维布可明显抑制整体式板桥已有纵向裂缝的扩展,降低受拉区混凝土应变水平,改善荷载横向分布规律,提高上部结构整体受力能力．     

中碳钢薄板坯连铸结晶器保护渣固态渣膜结构的研究

通过光学显微镜分析、扫描电镜分析及X射线衍射分析,研究了连铸结晶器保护渣固态渣膜的结构、矿相组成、结晶度等,从而了解了固态渣膜控制传热的机理,为降低中碳钢连铸坯表面纵裂纹的发生率提供了理论基础.