Slag Inclusions Research Articles

Failure Investigation of a Defective Weldment of an Oil Product Transmission Pipeline

An API 5L X52 oil product transmission pipeline experienced a sudden failure at a portion which had been buried in the bed of a river crossing after 33 years of service. Results showed that mechanical properties of the weldment had been reduced due to weld defects. The defects had been formed during construction welding and installation of the pipeline in the bed of the river crossing. No failure had occurred until this portion of the buried pipeline came out of its place in the bed of the river crossing. Under this condition, defective weldment (due to hydrogen stepwise cracking, incomplete fusion, porosity formation, and entrapped slag inclusion) was not capable of enduring stress imposed by the strong river stream and consequently failed. Metallographic and SEM studies as well as stress analysis were used for pipeline fracture investigation.

Investigating the Provenance of Iron Artifacts of the Royal Iron Factory of São João de Ipanema by Hierarchical Cluster Analysis of EDS Microanalyses of Slag Inclusions

Microstructural characterization techniques, including EDX (Energy Dispersive X-ray Analysis) microanalyses, were used to investigate the slag inclusions in the microstructure of ferrous artifacts of the Royal Iron Factory of Sao Joao de Ipanema (first steel plant of Brazil, XIX century), the D. Pedro II Bridge (located in Bahia, assembled in XIX century and produced in Scotland) and the archaeological sites of Sao Miguel de Missoes (Rio Grande do Sul, Brazil, production site of iron artifacts, the XVIII century) and Afonso Sardinha (Sao Paulo, Brazil production site of iron artifacts, XVI century). The microanalyses results of the main microconstituents of the microstructure of the slag inclusions were investigated by hierarchical cluster analysis and the dendrogram with the microanalyses results of the wustite phase (using as critical variables the contents of MnO, MgO, Al2O3, V2O5 and TiO2) allowed the identification of four clusters, which successfully represented the samples of the four investigated sites (Ipanema, Sardinha, Missoes and Bahia). Finally, the comparatively low volumetric fraction of slag inclusions in the samples of Ipanema (~1%) suggested the existence of technological expertise at the ironmaking processing in the Royal Iron Factory of Sao Joao de Ipanema.

RETRACTED PAPER: Evaluation of Parameters Effect on Microstructure and Mechanical Properties in TIG Welding of A105 to A106 Steels

Paper has been retracted. Welding parameters such as current intensity, voltage, number of passes can affect the mechanical properties of the weld. In this paper the effect of these parameters on structure and mechanical properties of welded A105 and A106 steels has been evaluated. According to the mechanical and microstructure test results, increasing in welding pass number causes reduction in grain size and increasing in average hardness of HAZ. Also inter-pass slag inclusion defect occurred in high number of passes.

Optimization of the Cascade Feed Forward Back Propagation network for defect classification in ultrasonic images

Ultrasonic Time of Flight Diffraction (TOFD) is now a well established NDE technique finding wide applications in the industry for inspection during manufacture, pre-service and also inservice. While conventionally interpretations of UT images are done by the inspector, a need has always been felt for automated evaluation and interpretation especially when large inspection volumes are involved. Apart from enhancing the speed of inspection, automated evaluation and interpretation provides better reliability of inspection. A number of approaches based on signal analysis coupled with artificial neural networks (ANN) are being tried internationally and limited success has also been obtained. This paper focuses on the development of a semi automatic toolbox for reliable and fast flaw classification in TOFD images using ANN. TOFD images are first acquired and statistical parameters such as mean, standard deviation, energy, skewness and kurtosis are calculated for the region of interest in the images. The classification of the flawed region like Crack, Lack of Fusion, Lack of Penetration, Porosity and Slag Inclusion was materialized using different ANN approaches which made use of these statistical parameters as their input. The process of optimization of a network involves comparison of classification accuracy and the sensitivity of the selected networks. The Cascade Feed Forward Back Propagation (CFBP) network with log sigmoidal activation function proved to be the optimized network model for the data set considered in this study.

Study on laser cladding remanufacturing process with FeCrNiCu alloy powder for thin-wall impeller blade

The centrifugal compressor impeller is widely used in petroleum, chemicals, and other fields and is liable to failure in complicated working environment. Laser cladding as an advanced technology was used to remanufacture the failure impeller. And, remanufacture quality and service safety should be considered. In this paper, simulation and experiments were applied to study the remanufacturing process of failure thin-wall impeller blade. Firstly, a sequentially uncoupled 3D thermo-mechanical finite element (FE) model was developed to calculate temperature distribution and conduct mechanical analysis. Secondly, the impeller blade of repair region quality was studied based on microstructure analysis, microhardness, and tensile property tests. Finally, dynamic-balancing experiment, over-speed test, and dye penetration inspection were used to assess the security of remanufactured impeller. Numerical simulation showed that high temperature (about 1521 °C) and high residual stress (about 300 MPa) were distributed surrounding heat-affected zone (HAZ). And, experiments showed that the deformation of remanufactured impeller was 1.5 mm without no pores, cracks, slag inclusion, and other defects occurred in the remanufactured region.

Iron Supply for the Building of Metz Cathedral: New Methodological Development for Provenance Studies and Historical Considerations

This paper develops new reflections regarding the provenance of iron artefacts, by defining the trade networks that might have supplied the building yard of the Metz city belfry at the end of the 15th century. Regional field surveys were carried out in Lorraine in order to constitute a chemical repository, including ironmaking zones considered as the most probable metal providers. The chemical characterization—both major and trace elements—of slag inclusions entrapped in the metallic matrix of iron reinforcements was performed in order to compare their chemical signature to the reference set. A statistical approach based on the combined use of descriptive multivariate analyses was developed to infer the origin of the metal supplied to the building yard. As the multiplicity of potential metal providers was assessed from former studies, the results obtained underline the place taken by local workshops in the supply strategy developed by the builders. This study thus provides crucial information supporting a discussion about the scale and the organization of such networks at the end of the Middle Ages

Анализ производительности и надёжности методов неразрушающего контроля сварных швов в строительстве

Introduction. The aim of this study is to evaluate the productivity and reliability of non-destructive testing techniques for the inspection of structural welds employed in the Hong Kong construction industry.
 Method. Manual ultrasonic pulse echo method and semi-automatic ultrasonic techniques using phased array (PAUT) as well as radiographic testing were employed. Five classes of defects were analyzed: lack of penetration, lack of fusion, crack, porosity and slag inclusion. The tests were carried out on the specimen made from structural plate, on which artefacts were inserted on the weld metal. The results were being studied to compare the defect detection reliability by both ultrasonic techniques. The flaw detection productivity using phased array is also compared with conventional ultrasonic testing at a determined rate.
 Results. The reliability of PAUT was 100% compared to 96.7% with manual ultrasonic testing, however with the inclusion of defect sizing and tolerance the reliability of manual UT is dropped to 57.4%, which implies there is a chance of 42.6% of improper sizing). PAUT exhibits the reliability of 87.5%. The research will be continued with the aim of determining the most appropriate and reliable NDT methods in each case.

In-situ observation of the behaviour of non-metallic inclusions at different interfaces in the system steel-slag-refractory

The system steel-slag-refractory and reactions of non-metallic inclusions at its interfaces are decisive in numerous metallurgical processes. In order to obtain the desired steel cleanness level, a detailed understanding of the occurring interactions is needed. This study focuses on the in-situ observation of different reactions of non-metallic inclusions in steel and slag. For this purpose a Confocal Scanning Laser Microscope attached to a high temperature furnace is applied which enables the visualization of metallurgical phenomena at steelmaking temperatures up to 1700 °C. Two different examples are discussed: First, the agglomeration of different inclusion types in a Ca-treated steel is described and corresponding attraction forces are calculated. Secondly, the dissolution of Al2O3 and MgOAl2O3 in two slags of the system CaO-Al2O3-MgO-SiO2 is examined, including the evaluation of the governing dissolution mechanism. Finally, an outlook on further experimental possibilities is given.

Experimental smelting of iron ores from Elba Island (Tuscany, Italy): Results and implications for the reconstruction of ancient metallurgical processes and iron provenance

Iron deposits from Elba Island (Tuscan Archipelago) were extensively exploited since the 1st millennium BC: both raw iron ore and smelted blooms were extensively traded through the Mediterranean region. Within the frame of the multidisciplinary research Project “AITHALE” (from the Greek name for Elba Island), we have performed a series of archaeometallurgical experiments primarily to investigate the traceability of Elban iron ores during the various steps of the chaîne opératoire of bloomery iron production. Results of experiments performed both in the field (reconstruction of a bloomery furnace) and in the laboratory (smelting experiments carried out in a gas mixing furnace) are discussed in the text. Slags produced by smelting of W-Sn-rich iron (hematite) ores, like those from Elba island, show the presence of these elements in phases of their own, either relic (scheelite, ferberite, cassiterite) and/or newly formed (iron-tin alloys). Iron bloom obtained from this kind of iron ore could also bear evidence of the peculiar geochemistry of smelted ore, with tungsten preferentially associated with slag inclusions and tin eventually enriched in the metallic phase.

Slag Compounds Formed from the Nodularization Treatment Until Pouring the Molds to Produce Spheroidal Graphite Cast Iron Parts

The present work is included as part of research undertaken about the effect of raw materials and some processing variables on the origin and the composition of those slag compounds formed during the manufacturing of spheroidal graphite cast iron parts. The composition and phases present in a number of slag samples obtained from Mg-treated melts have been investigated and discussed. Both slag samples which are floating in the melts surface and those adhered to the refractory lining of the pouring device have been analyzed. Finally, two different morphologies of slag inclusions found on cast iron parts have been studied and then compared to the results obtained from the previous slag samples characterization. It has been observed that composition of slag varies along the different steps of the production process as a function of the oxidizing level of the gas which is in contact with the melts and also of the remaining time in the ladle. Regarding crystallinity of slag, it has been found that it strongly depends on its composition and formation rate. All the information obtained from the study of slag formed before pouring process has been then used for estimating the origin of the slag inclusions commonly found in manufactured cast parts.

Investment Casting Defect Prediction using Neural Network and Multivariate Regression along with Principal Component Analysis

Investment cast parts can contain different types of internal defects like ceramic inclusion, flash, misrun, shrinkage, and slag inclusion. Their occurrence can be prevented by prediction from a given composition and process parameter set. In this work, we explore the application of artificial neural network (ANN) and multivariate regression (MVR) to predict a wider range of investment casting defects based on real-time industrial data. The data of 24 parameters related to process, chemical composition, and defects was collected from about 500 heats in an industrial investment casting foundry. This was reduced to ten principal components using principal component analysis (PCA). Different six ANN training models were used to train a portion of the data and used for prediction. The MVR was also employed on the same data for prediction, and its results were compared with ANN models. The best results were obtained by ANN with Levenberg and Marquardt algorithm. [Received 16 August 2016; Accepted 25 October 2016]

Investment casting defect prediction using neural network and multivariate regression along with principal component analysis

Investment cast parts can contain different types of internal defects like ceramic inclusion, flash, misrun, shrinkage, and slag inclusion. Their occurrence can be prevented by prediction from a given composition and process parameter set. In this work, we explore the application of artificial neural network (ANN) and multivariate regression (MVR) to predict a wider range of investment casting defects based on real-time industrial data. The data of 24 parameters related to process, chemical composition, and defects was collected from about 500 heats in an industrial investment casting foundry. This was reduced to ten principal components using principal component analysis (PCA). Different six ANN training models were used to train a portion of the data and used for prediction. The MVR was also employed on the same data for prediction, and its results were compared with ANN models. The best results were obtained by ANN with Levenberg and Marquardt algorithm. [Received 16 August 2016; Accepted 25 October 2016]

The Sources of Surface Defects in Castings Produced in Automated Process Lines

Abstract This study summarises the research efforts undertaken in iron foundry plants in which the process are mostly automated and mechanised. The research program was limited in scope, focusing on causes of surface defects in castings products that are attributable to the bentonite-containing sand and the mould system. One of the potential roots of surface defects is heterogeneity of sand grains, containing lumped ball-shaped grains and irregular pellets with a layered-structure. The moisture contents of those lumped grains is different than the moisture level required in the process, besides these grains may contain various elements and metallic compounds which, when cast into moulds, may react with molten metals in an uncontrolled manner. As a result, surface defects are produced, such as surface blowholes, burst penetration, sand holes, slag inclusions, pinhole porosity. This study investigated the efficiency of key sand preparation and moulding machines and installations integrated into the casting process line. The efficiency of machines and installations is defined in terms of quality parameters of sand mix and moulds, which are associated with the emergence of surface defects on castings.

Stress calculation in roasted iron-ore pellets on cooling

A method is proposed for calculating the stress in roasted zonal fluxed pellets. The method is based on the appearance of a stress state at the boundary zones with different solidification temperatures of the slag inclusions on cooling. The stress state is calculated for Kachkanar pellets with different positions of the hematite and magnetite zones. It is shown that, on cooling annealed zonal pellets in air, tensile normal stress appears in the radial direction at the boundary of the magnetite core and the hematite shell. The presence of a three-zone structure in the pellets (magnetite core + hematite shell + surface magnetite film) facilitates the redistribution of normal stress over the cross section. Increasing the thickness of the surface magnetite film reduces the tensile stress in the radial direction at the boundary of the core and the shell. As a result, the pellet strength is increased. On cooling roasted pellets with a hematite core and a magnetic shell in a neutral atmosphere, tensile normal stress appears in the tangential direction, tending to reduce the pellet strength.

The Dor 2002/2 Shipwreck, Israel: Characterization of Surviving Ironwork

The Dor 2002/2 shipwreck provides evidence of a 15-m-long vessel built to a high standard, and adds essential information to our knowledge of the construction of small vessels that plied the Eastern Mediterranean during the late Ottoman period. During the underwater excavations of the shipwreck, two metal objects were retrieved: a wooden heart (rigging element) with an iron ring-bolt, and a broken iron chain link with a piece of metal cable. This study aims to understand the manufacturing processes of the objects, and to propose their possible dating. The artifacts were studied by archaeometallurgical testing methods, including, HH-XRF, metallographic stereo, light and SEM–EDS microscopy, and microhardness tests. The results revealed that the ring-bolt was made of ferrite phase with preferred oriented slag inclusions microstructure, as typical for indirect smelted wrought-iron. The chain link was made of gray cast-iron. The suggested date of the shipwreck was 1800; however, based on the archaeometallurgical test results, it is suggested that the two iron artifacts were manufactured between the years 1839 and 1856. This research demonstrates the important contribution of the study of metal finds to the dating of shipwrecks.

Production of Permeable Fibrous Materials Composed of Silicon Nitride

A technology which involves spraying a silicon-based thixotropic thermoplastic slip with a paraffin-based binder onto a rotating substrate-target is used to obtain a material that based on reaction-sintered silicon nitride and has a porous, permeable, fibrous framework-like structure. The fibers are distributed evenly over the surface of the substrate and are deposited on it in varying directions at low rates allow heat to be removed from the product. This results in the formation of fibrous framework-like structures that retain their original porosity as they subsequently undergo heating and a certain amount of contraction in the height direction. They can be used as porous partitions for the delivery and combustion of natural fuels in power plants and as filters for removing slag inclusions and oxide films from melts.

Crack spacing threshold of double cracks propagation for large-module rack

Large-module rack of the Three Gorges shiplift is manufactured by casting and machining, which is unable to avoid slag inclusions and surface cracks. To ensure its safety in the future service, studying on crack propagation rule and the residual life estimation method of large-module rack is of great significance. The possible crack distribution forms of the rack in the Three Gorges shiplift were studied. By applying moving load on the model in FRANC3D and ANSYS, quantitative analyses of interference effects on double cracks in both collinear and offset conditions were conducted. The variation rule of the stress intensity factor (SIF) influence factor, RK, of double collinear cracks changing with crack spacing ratio, RS, was researched. The horizontal and vertical crack spacing threshold of double cracks within the design life of the shiplift were obtained, which are 24 and 4 times as large as half of initial crack length, c0, respectively. The crack growth rates along the length and depth directions in the process of coalescence on double collinear cracks were also studied.

Experimental analysis of dissimilar metal weld joint: Ferritic to austenitic stainless steel

The dissimilar metal weld (DMW) joint between SA508Gr.3Cl.1 ferritic steel and SS304LN using Inconel 82/182 consumables was required in the nuclear power plants. The joint integrity assessment of these welds requires mechanical and metallurgical properties evaluation in weldment regions. The joint was subjected to 100% radiography test and bend test and transverse tensile test. Welding and testing were carried out as per the requirements of ASME Sec-IX and acceptance criteria as per ASME Sec-III. The transverse tensile test results indicated the failure from the weld metal although it satisfies the minimum strength requirement of the ASME requirements; therefore, the DMW joint was analyzed in detail. Straight bead deposition technique, fine slag inclusion, less reliable radiograph technique, plastic instability stress, yield strength ratio and metallurgical deteriorations have been contributed to failure of the DMW joint from the weld region. In the present work, the factors contributing to the fracture from weld metal have been discussed and analyzed.

STUDY OF “CAKE” DEFECT IN CONTINUOUSLY CAST AUSTENITIC STAINLESS STEEL 18CR-10NI-1TI. REPORT 1

The structure of “cake” defect is a porous metal matrix with numerous inclusions: slag inclusions, coarse clusters of titanium nitrides and carbonitrides and complex composition oxides. Contamination of metal by deoxidation products, oxidation of the metal stream during casting increases the probability of formation of refractory phase in the form of a cluster of titanium nitride particles and the emergence of “cakes”.

INVESTIGATION OF SLAG FORMATION IN TUNDISH OF CONTINUOUS CASTER

The investigation of slag formation in tundish of continuous caster for casting melting low-carbon and low-alloy steel weighing 360 tons is exe- cuted. It is found that the casting series of 5 – 10 melts there is a significant increase in weight and the chemical composition of the slag. A key role in this process is the flow of the slag inclusions, pop out of bottled steel. For casting low carbon steel weight surfaced inclusions is about 30 % by weight of the final slag, and the casting alloy steel – about 50 %. A much smaller role in the chemical composition of the slag is dissolved refractory lining: 4 – 5 % by weight of the final slag for chamotte brick lining and 14 – 15 % for magnesia lining. The changes in the chemical composition of the slag raises its melting temperature at 80 – 140 °C.