Toughness requirements for steel structural components with surface flaws

Fracture mechanic safety analyses consist of a comparison between material toughness and toughness requirement of the Investigated structure. For the selection of suitable materials the requirements must be known. The fracture mechanics toughness requirements for a structural component depend on several parameters. Load case, geometry of the component and of a postulated or detected flaw, strength of the steel and the chosen safety criterion are decisive for the toughness requirements. Performing three-dimensional elastic plastic finite element analyses the toughness requirements for plates of high strength structural steels with surface flaws have been determined as a function of the above mentioned parameters.     

Converter smelting of steel with preliminary scrap heating to reduce hot-metal consumption

The consumption of hot metal in slag preparation and slag-coating application in the converter may be reduced by scrap heating. The thermal equivalents of the coke additions and coke consumption in smelting to ensure the required metal temperature at tipping are determined. The basic principles for converter technology with preliminary scrap heating are developed, and experimental data are obtained regarding the efficiency with which the carbon-bearing fuel (coke) is used, so as to improve the thermal balance of the converter process and the final characteristics of steel production.     

Cell activation by the micropatterned surface with settling particles

Surface topography plays an important role in cell orientation and morphogenesis. In this study, we prepared a micropatterned surface with settling particles to obtain more detailed information about the cell recognition against the microstructured surface. Core-shell type particles having a poly-(N-isopropylacrylamide) (polyNIPAM) shell were prepared by seeded polymerization. Particles were settled on a polystyrene (PSt) flat dish by the spinner to prepare a micropatterned surface with settling particles. It could be seen that the polyNIPAM shell shrunk above and swelled below the LCST. For comparison, a thermosensitive flat surface was prepared by the graft polymerization of NIPAM. No morphologic change of cells contacting the both surfaces was observed with either an optical or a scanning electron microscope. Moreover, particles could move or roll on these surfaces when shaking the dishes. The weak interaction between neutrophil-like cells and the micropatterned surface with settling particles or the polyNIPAM-grafted surface was estimated by measurement of active oxygen released by cells. A little release could be observed at both 25 and 35 degrees C. The amount of released active oxygen at 35 degrees C was slightly larger than at 25 degrees C. When the temperature was suddenly changed, the dynamic changes of particle shape and size resulted in the excess release of active oxygen from cells contacting the micropatterned surface with settling particles. Meanwhile no stimulation could be observed in the polyNIPAM-grafted surface even if the temperature is suddenly changed. These results indicate that the micropatterned surface with settling particles can induce the dynamic stimulus at a patterned input mode.     

Multi-class classification method for steel surface defects with feature noise

Defect classification is the key task of a steel surface defect detection system.The current defect classification algorithms have not taken the feature noise i...     

激光陶瓷合金化

通过陶瓷合金化涂料的研制,在激光淬火的工艺条件下获得激光陶瓷合金化层.经过陶瓷合金化的钢铁材料,其耐磨性能比激光淬火高约一倍.陶瓷合金化涂料具有与目前广泛使用的激光淬火吸光涂料同样的粘结性能,吸光性能和施涂工艺性能.激光陶瓷合金化是纳米技术、氮化硅应用技术、稀土应用技术、不同质材料之间的偶联技术,激光加工技术和涂料粘结...     

表面自纳米化钢铁材料的研究进展

综述了国内外表面自纳米化钢铁材料的研究进展。介绍了表面自纳米化钢铁材料的不同制备方法,并对比分析了国内外4种主要方法的优缺点和工业应用的可行性。从组织特征、力学性能、耐蚀性及扩散性方面总结分析了表面自纳米化钢铁材料的实验室研究成果。最后对钢铁材料表面自纳米化技术的产业化推广前景进行了展望。     

Effect of surface roughness on the surface lubrication performance of galvanized steel sheets with a self-lubricated coating

Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating.The effects of surface roughness on the surface lubrication performance of the steel sheets were examined using a friction coefficient tester.Results revealed large dynamic friction coefficients for the galvanized steel sheets,which increased remarkably with surface roughness.Once the self-lubricated coating was applied,significant drops in the dynamic friction coefficients were measured.After the first stage of the friction test,the coefficients were almost unchanged,which reflected a weak dependence on the surface roughness of the self-lubricated steel sheets.However,the dynamic friction coefficients gradually increased as the test progressed,where these increase clearly correlated with the surface roughness of the self-lubricated steel sheets.     

差热法测定钢样表面氧与体内氧的方法研究

本文利用美国LECO公司生产的TC-436氧氮仪,研究了光谱纯Fe2O3,Al2O3和在大量脱氧铁存在下Al2O3的氧释放曲线,得到了它们的分解功率、分解电流和分解计算温度.成功地分离了钢样的表面氧和体内氧,并对钢样不同表面氧的组成做了初步研究.     

热轧集装箱用钢表面缺陷分析

在热轧集装箱用钢的钢卷表面发现有细条状和近似圆点状的2种缺陷.通过对这2种缺陷进行EPMA、SEM和EDS等分析,并结合现场的轧制工艺情况,对这2种缺陷形成原因进行综合分析.分析结果表明:这2种缺陷都是在轧制过程中形成,由于集装箱用钢含Si量较高,造成除鳞难以去除,轧制油的油污与氧化铁皮压入形成了一种近似圆点的复合缺陷.     

8407模具钢表面渗铝的研究

为了防止模具表面产生热疲劳裂纹,通过冷喷涂在8407钢试样表面形成了一层铝涂层,再进行扩散处理,在试样表面形成了渗层.通过理论分析确定低温渗铝的上艺参数,并与渗铝实验进行检验,重点研究了扩散温度和扩散时间对渗层质量的影响.结果表明,8407钢经过冷喷涂铝后再进行扩散处理能够实现低温渗铝.在550℃下扩散4 h左右形成的渗层质量比较理想.     

Improvement of surface quality on peritectic steel slabs

Peritectic steel grades are very sensitive to microcracking along austenitic grain boundaries in continuous casting. Irsid and Aktiengesellschaft der Dillinger Hüttenwerke (DH) have combined laboratory studies and industrial trials to improve surface quality on these sensitive grades. Laboratory studies at Irsid confirmed the hypothesis that a very thin layer of ferrite along austenitic grain boundaries is detrimental for cracking and indicate that the risk of cracking decreases as soon as ferrite ratio is above 10 %. Dilatometric investigations demonstrate that there is a strong shift between thermodynamic equilibrium and beginning of γ→α phase transformation under casting conditions. Furthermore, at the slab surface, there is no cyclic transformation γ→α→γ induced by thermal cycling in front of spray nozzles and supporting rolls. DH performed trials with various cooling strategies on its new vertical caster No. 5. No cracks appear with intensive cooling whereas microcracks are present with soft cooling. These results are in agreement with laboratory studies. Intensive cooling is the standard condition at DH. With this process, microcracking is avoided for all slab formats.     

Complement activation by bacterial surface glycolipids: a study with planar bilayer membranes

Parameters affecting the characteristics of the drug loaded crosslinked sodium alginate matrix films and the release of metoclopramide hydrochloride and cisapride from these matrices were studied. It was shown that the release rate is influenced by the crosslinking technique of the matrix film, crosslinker type and concentration, drug physico-chemical properties especially solubility and the molecular weight, acidity of the release medium, concentration and the loaded quantity of the drug in the matrix. The crosslinking process of the matrix film was shown to be an interfacial phenomenon and the nature of crosslinking depends on the crosslinker type and concentration. This work also showed that crosslinked alginate in a matrix form has limitation in practical use due to the effect of acidic medium on the crosslinking of the matrix film and hence, the rate of drug release.     

粗糙度对热镀锌自润滑钢板表面摩擦特性的影响

在表面粗糙度分别0.82、1.23、1.68和2.07μm的四种热镀锌钢板上涂覆自润滑涂层制得热镀锌自润滑钢板,采用表面性能分析仪研究了热镀锌钢板表面粗糙度对热镀锌自润滑钢板表面摩擦特性的影响。结果显示,无涂层时钢板表面动摩擦因数较大,均在0.35以上,且随其表面粗糙度的增加迅速增加。当涂覆自润滑涂层后,自润滑钢板表面动摩擦因数均显著降低至0.15以下并在摩擦测试初期几乎保持不变,表明自润滑钢板表面粗糙度在摩擦测试初期对其表面动摩擦因数无影响。但在摩擦测试后期,自润滑钢板表面动摩擦因数逐渐增大,且增大幅度随着表面粗糙度的增加而增加。     

Fatigue behavior of carburized steel with internal oxides and nonmartensitic microstructure near the surface

The characteristic fatigue behavior of carburized and quenched steel with internal oxides and non-martensitic microstructure near the surface was presented through rotating bending fatigue test. The S-N diagram revealed two knees and the specimens continued to fail over 10⁷ stress cycles. The fatigue limit could not be obtained even at 10⁸ stress cycles. The test results were compared to those for the specimens without surface structure anomalies to show the effect of structure anomalies on the fatigue behavior of carburized steel.     

Laser-beam surface transformation hardening of hypoeutectoid Ck-60 steel

A carbon dioxide laser with a power of 1.5 KW was employed for surface hardening of a hypoeutectoid Ck-60 steel. The microstructures and hardness profiles were determined as a function of power density and laser beam travel speed. The microstructure in the laser-beam hardened zone depended on power density and consisted of plate martensite (for high power density) or autotempered martensite (for low power density). In the transition zone of the laser-beam treated specimens, martensite and ferrite were observed. Case depth and maximum hardness were found to depend on power density and travel speed. A simple one-dimensional heat flow model has been used for the selection of process parameters and for the prediction of case depth. Calculated and experimentally determined case depths are in good agreement for medium values of power density.