Effect of RE Oxide on Cracking Resistance of Hardfacing Metal

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缓慢拉伸法在确认低倍白点中的应用

针对盘件低倍检验试样表面上发现的白点裂纹,低倍断口与力学性能检验结果正常。通过缓慢拉伸法及其断口的宏观、微观分析,确认低倍裂纹为白点裂纹。     

冷镦钢表面开裂的影响因素研究

影响冷镦钢质量的主要因素之一是顶锻开裂。结合3年来的生产实践,把顶锻开裂的形式归纳成两部分,即内部塑性型开裂和表面裂纹源型开裂。同时,介绍了裂纹的表现形式,对其产生机理和断裂力学理论进行了分析研究,提出了生产中的针对措施。     

Innovative ANN Technique for Predicting Failure/Cracking Load of Masonry Wall Panel under Lateral Load

This paper introduces an artificial intelligent technique for predicting the failure/cracking loads of laterally loaded masonry wall panels based on their corresponding failure/cracking patterns derived from the laboratory experiments. First, a lattice is made on a wall panel based on the dimension of the wall panel. Then, the numerical values, 0 or 1, are assigned to the cells in the lattice in order to describe the failure/cracking pattern. Thus, a numerical matrix is formed to show the failure/cracking pattern of the wall panel. Since the matrices for the wall panels with various sizes have different dimensions, the gray level cooccurrence matrix is innovatively used to transfer these matrices into the matrices whose dimensions are the same. Next, the numerical modes of failure/cracking patterns of experimental wall panels and the corresponding normalized failure/cracking loads can be used as the input and output of the artificial neural network (ANN) training data, respectively. Finally, three types of ANN models for predicting the failure/cracking load of the unseen wall panel are achieved by repeatedly training and adjusting so as to optimize its parameters. In a wide significance, this study opens a novel way to establish the relationship between the failure/cracking pattern and the failure/cracking load of the wall panel.     

Stress corrosion cracking of α-brass in waters with and without additions

Slow strain rate stress corrosion tests on a 0.032 pct As brass in SO₂ solutions of increasing dilution eventually resulted in tests being carried out in various waters which were also found to promote cracking. A 0.002 pet As brass was also found to be susceptible to cracking in deionized water, but in brackish water or an acidified sulfate solution this brass did not display the stress corrosion cracking observed in these more aggressive solutions by the higher As brass. The addition of arsenite to distilled water or arsenate to deionized water in sufficient amounts effectively inhibited the cracking observed at controlled potentials or open circuit in these waters without the As additions. The results are interpreted as indicative of dezincification being involved in these various environments that promoted cracking, but the extent of the dezincification plays an important role in determining whether or not cracking occurs, those additions leading to rapid and massive dezincification involving redeposition of dissolved Cu not being conducive to cracking.     

倒角连铸坯角部纵向裂纹形成机制及控制

 倒角结晶器是控制板坯角部横向裂纹的有效方法之一,但角部纵向裂纹是倒角连铸坯易发的缺陷,这成为了倒角结晶器大规模应用的最大障碍。通过研究倒角结晶器生产工艺参数、设备精度以及喷嘴堵塞等因素对倒角连铸坯角部纵向裂纹的影响,确定了角部纵向裂纹发生的机制。研究表明,倒角结晶器窄面锥度不合理、0段和1段连接偏差以及喷嘴堵塞等是角部纵向裂纹产生的主要原因。通过采取有效措施,可以将倒角连铸坯角部纵向裂纹发生率降低到0.6%以下,使得倒角结晶器实现大规模的工业应用。     

R6.5／12—1200板坯纵裂原因分祈

针对R6．5／12—1200板坯连铸中出现的纵裂缺陷,采取降低和控制纵裂发生的措施。通过采取措施,使板坯纵裂大幅度降低。     

轻型面包车车身开裂原因分析

以18台轻型面包车车身开裂为事实依据，通过对车身钢板的成分、组织、工艺进行分析检验，结果表明氢脆和应力腐蚀是造成车身开裂的原因。对车身产生应力腐蚀的条件进行了分析，提出了预防车身开裂的措施和工艺改进方法。     

Stress-corrosion resistance of high-strength Al-Zn-Mg-Cu alloys with and without silver additions

The separate and combined effects of adding silver, substituting other elements for chromium, increasing zinc, or varying the copper content on the tensile properties and resistance to stress-corrosion cracking of 7075-type alloys were investigated. Adding silver produced no increase in strength and marginal increases in the resistance to stress-corrosion cracking. Substituting either zirconium or manganese for chromium increased strength and decreased the resistance to stress-corrosion cracking after a given precipitation heat treatment; at equal strength levels, the resistances to stress-corrosion cracking of the chromium-free alloys below 3 in. (76 mm) thickness were comparable to those of 7075. Increasing zinc increased the resistance to stress-corrosion cracking but increased quench sensitivity. Decreasing copper decreased the resistance to stress-corrosion cracking in the atmosphere. Increasing copper in chromium-free alloys provided the best combination of strength and resistance to stress-corrosion cracking. Longer atmospheric exposures are needed to firmly establish the stress-corrosion resistance. Formerly Assistant Director, Alcoa Research Laboratories, is now retired.     

褐铁矿含碳球团的爆裂特性研究

根据褐铁矿含碳球团转底炉还原熔分生产粒铁的技术思想,对褐铁矿含碳球团的爆裂特性进行了实验研究.实验结果表明,褐铁矿含碳球团的爆裂与结晶水的解离有关,结晶水解离速度较快,在950℃下90s内球团中的结晶水基本上全部解离,褐铁矿含碳球团的爆裂温度约为900℃,与不含煤粉的褐铁矿球团相比约高100℃,含碳球团有利于减弱爆裂,因此,褐铁矿含碳球团的入炉温度要低于900℃.在爆裂温度以下,褐铁矿含碳球团的预热温度越低,预热时间越短,到1 300℃急速加热时,球团爆裂越严重.因此,在本实验条件下,球团最佳入炉温度约为850℃.     

Cavity microstructure and kinetics during gas tungsten arc welding of helium-containing stainless steel

Helium was implanted in type 316 stainless steel, through tritium decay, to levels of 0. 18, 2. 5, 27, 105, and 256 atomic parts per million (appm). Bead-on-sheet welds were then made using the gas tungsten arc (GTA) process. Intergranular cracking occurred in the heat-affected zones (HAZs) of specimens with helium concentrations equal to or greater than 2.5 appm. No such cracking was observed in helium-free control specimens or in specimens containing the lowest helium concentration. In addition to the HAZ cracking, brittle, centerline cracking occurred in the fusion zone of specimens containing 105 and 256 appm helium. Transmission and scanning electron microscopy results indicated that both the HAZ cracking and centerline cracking in the fusion zone resulted from the stress-induced growth and coalescence of cavities initiated at helium bubbles on interfaces. For the HAZ case, the cavity growth rate is modeled and shown to predict the experimentally measured 1-second time lag between peak weld temperature and the onset of cracking.     

Investigation of Hot Cracking Behavior in Transverse Mechanically Arc Oscillated Autogenous AA2014 T6 TIG Welds

Hot cracking studies on autogenous AA2014 T6 TIG welds were carried out. Significant cracking was observed during linear and circular welding test (CWT) on 4-mm-thick plates. Weld metal grain structure and amount of liquid distribution during the terminal stages of solidification were the key cause for hot cracking in aluminum welds. Square-wave AC TIG welding with transverse mechanical arc oscillation (TMAO) was employed to study the cracking behavior during linear and CWT. TMAO welds with amplitude?=?0.9?mm and frequency?=?0.5?Hz showed significant reduction in cracking tendency. The increase in cracking resistance in the arc-oscillated weld was attributed to grain refinement and improved weld bead morphology, which improved the weld metal ductility and uniformity, respectively, of residual tensile stresses that developed during welding. The obtained results were comparable to those of reported favorable results of electromagnetic arc oscillation.     

连铸板坯纵裂原因浅析

根据宝钢连铸大生产实绩，调查了影响板坯纵裂的因素，分析了连铸板坯发生纵裂的原因，通过采取一定的措施，使连铸坯裂指数有一定的改善。     

废塑料与煤粉热解特性的研究

分别将4种废塑料和煤粉置于非氧化性气氛中研究其热解特性。研究结果表明,在氮气中废塑料的裂解过程主要分为三个阶段:缓慢裂解—急速裂解—缓慢裂解至结束,煤粉的裂解过程比较平缓;最大裂解速度对应的温度,废塑料平均超过400℃,煤粉为900℃;终了裂解量,不同品种废塑料为85%～100%,而煤粉仅22%,两者差异极大;废塑料的完全裂解表观活化能是煤粉的6～10倍。     

Investigations Using Smooth and Notched Specimens into Validity of Caustic Cracking Susceptibility Diagram

Susceptibility to caustic cracking at different temperatures and caustic concentrations, as predicated by the caustic cracking susceptibility diagram, has been examined by stress corrosion cracking tests using smooth specimens (by slow strain rate testing) and notched specimens (by cylindrical notch tensile testing). Intergranular fracture, as established by scanning electron microscopy, was taken as the confirmatory evidence of caustic cracking. The results generated using notched specimens largely have been consistent with the prediction of the susceptibility diagram.     

Stress Oriented Hydrogen Induced Cracking of Linepipe Steel

The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.     

Field Investigations of Cracking on Concrete Pavements

This paper presents the results of several investigations to identify the underlying causes of longitudinal cracking problems in Portland cement concrete (PCC) pavement. Longitudinal cracking is not intended and detrimental to the long-term performance of PCC pavement. Longitudinal cracking problems in five projects were thoroughly investigated and the findings indicate that longitudinal cracking was caused by: (1) late or shallow saw cutting of longitudinal joints; (2) inadequate base support under the concrete slab; and (3) the use of high coefficient of thermal expansion (CTE) aggregates. When the longitudinal cracks were caused by late or shallow saw cutting of longitudinal joints, cracks developed at a very early stage. However, when there was adequate base support, the longitudinal cracks remained relatively tight even after decades of truck trafficking. Another cause of longitudinal cracking was inadequate base support, and cracking due to this mechanism normally progressed to rather wide cracks. Some cracks were as wide as 57?mm. Evaluations of base support by dynamic cone penetrometer in areas where longitudinal cracks were observed indicate quite weak subbase in both full-depth repaired areas and surrounding areas. This implies that the current requirements for the subbase preparation for the full-depth repair are not adequate. Another cause of longitudinal cracking was due to the use of high CTE aggregate in concrete. Large volume changes in concrete when coarse aggregate with high CTE is used could cause excessive stresses in concrete and result in longitudinal cracking. To prevent longitudinal cracking, attention should be exercised to the selection of concrete materials (concrete with low CTE) and the quality of the construction (timely and sufficient saw cutting and proper selection and compaction of subbase material).     

冷轧镀锌板冲压分层开裂原因分析

针对近几年汽车厂反映的冷轧镀锌板冲压后分层开裂的问题,为了研究该缺陷产生原因,选取4块典型的冲压分层开裂试样,使用扫描电镜和能谱仪对缺陷的微观特征进行了分析。结果表明,引起冷轧镀锌板冲压分层开裂的主要原因为保护渣卷入、皮下夹杂物、异物压入、擦划伤4种情况。4种缺陷的产生原因各不相同,但造成开裂的机理基本类似,对每一类缺陷的形成原因和开裂机理进行了分析与讨论,并提出了改善措施,为缺陷的原因排查、工序分离和质量改进提供了方向。     

Hot cracking susceptibility research in BTW1 austenitic high-manganese wear-resistant steel

Baosteel's first BTW1 austenitic high-manganese wear-resistant steel exhibits strong deformation-induced hardening characteristics.Compared with common low-alloy martensitic wear-resistant steels in the market,it has improved impact wear resistance,hard abrasive wear,erosion wear performance,and impact toughness.The metallurgical properties of such austenitic wear-resistant steel lead to the risk of failure because of hot cracking defects in the welded structure.In wear-resistant applications,evaluating hot cracking susceptibility is necessary to avoid the effect of welding defects.In this study,the Varestraint test is used to quantitatively analyze and evaluate the hot cracking susceptibility of BTW1 austenitic high-manganese wear-resistant steel.The test results show that by controlling the content of impurity elements and grain refinement,BTW1 austenitic high-manganese wear-resistant steel effectively reduces hot cracking tendency and has a low incidence of hot cracking under small strain conditions.The developed matching welding process can effectively avoid the influence of hot cracking susceptibility.     

New Composition Based Technique for Solidification Cracking Resistance Evaluation

Predicting the occurrence of solidification cracking during the solidification of metallic alloys by numerical simulation is a crucial move for avoiding such defects. Several models are widely available, however, the application of such are impacted due to the specific and not accessible parameters required. A simple, composition-based approach to rank solidification cracking susceptibility is presented. The procedure links computational thermodynamic and computational fluid dynamics (CFD) to provide an evaluation tool for solidification cracking. The method is related to the liquid filling phenomena in dendritic arms during solidification, which plays a critical role in solidification cracking phenomena. The dendritic profiles were constructed using the fraction of solid calculated by commercial thermodynamic software packages. The calculated results were compared with experimental solidification cracking data and showed satisfactory accuracy. The method capability to rank the solidification cracking propensity of similar alloys based on composition provides an important new operative tool to aid alloy development in welding and additive manufacturing related areas.