Slag Inclusions Research Articles

Ремонт наплавкой при дефектах металла трубы и сварных соединений

Cladding repair is the one of the most simple and least expensive repair technologies. It refers to both permanent and temporary repair methods. It reduces work costs and time of repair works while retaining the quality required by the statutory requirements. With the help of cladding repair, a significant number of defects of corrosion-mechanical origin can be eliminated. The problem of improving this technology is of utmost importance. The purpose of the present research is to develop the technology for effective and safe cladding repair of such defects as corrosion damages of pipe metal and such welded connection defects as incomplete groove filling, undercut, pores, strikes, slag inclusion. The following problems were solved to reach this goal: research of thermal cycles in the course of cladding, research of cladding modes, development of multipass repair technology, determination of allowable defect parameters, and detection of methods for optimal quality control of repaired areas. The specialists performed testing of full-scale pipe samples and circular joint of pipes, imitating the surface defects after cladding repair. The test results did not reveal the damage of metal and welded connection areas. Cladding repair allows recovering bearing capacity of pipeline to design level. This technology can be used in the works on shutdown pipelines and on pipelines under operation.

Typology of the medieval axes from the north of Western Siberia

The paper presents the results of the research on the Middle Ages iron axes found in different years in the north of Western Siberia and the Urals, excluding pole-axe (berdysh Rus.) that appear in large numbers in the study area with the growing of the Russian population. The relevance of such study has matured, since there are enough sources that need to be generalized and critically compiled. Taking into account the morphological features of the archaeological evidence, the authors propose to classify all currently known axes by 2 groups and 13 types. The first group including 3 types of minting axes were made exclusively for combat use. The second group includes 10 types of axes, classified as universal, which served both for the military and for economic purposes. The text with the description of the sites contains also table with the data on the basic parameters of axes (item length, blade width) and the time of their use (existence). For the first time, a new type of battle axe (type 13), accidentally found in the Khanty-Mansi Autonomous Okrug — Ugra, is published. We present analogues of this subject among the products of Russian blacksmiths of the 13th–14th centuries and explain the position on the dating and on origin of the axe. The paper discusses the evolution of certain types of objects, describes plots concerning the origin of certain items (imports from Volga Bulgaria, Russian lands, etc.) and the special attitude of the local population to this type of weapon, which could be stored for centuries in the holy places of the Ob Ugrians. The authors come to the conclusion that imported axes of the second group were used as a standard for Siberian blacksmiths. But local products, characterized by primitive technology (a multilayer package), low quality welding of iron strips and an abundance of slag inclusions, can be finally identified only after metallographic microstructural analysis. This research should be prolonged, because annual archaeological investigations replenish the source base, and, with no doubt, the typology of axes proposed in the article will be supplemented and adjusted.

Influence of plunge depth during friction stir welding of aluminum pipes

This study focuses on the application of friction stir welding (FSW) process for joining of pipes. It addresses key issues associated with fusion welding techniques, such as lack of fusion, over penetration, slag inclusions, root crack, undercut root gap, and thermal distortion. The influence of process parameters on the physical properties during FSW of aluminum pipes has been studied, which allows selecting an optimum combination of parameters for achieving superior welds. Physical responses such as variation in axial force, torque, temperature, and power have been analyzed. Tensile test of the joints fabricated shows a maximum of ∼90% joint strength efficiency with respect to the base material. The peak temperature or heat input is found to be increasing during FSW, which creates a larger grain size in the stir zone of the joints, resulting in the higher hardness of the joints.

Modification of tundish design to improve quality of slabs, casted at CCM No. 4 of EVRAZ NTMK

A technology of continuous casting of steel has a large effect on its contamination. In particular, proper organization of metal flows in tundish and mold is very important. After completion a series of casting through a tundish and drop of metal level in it, it possible, that the slag flows from the surface layers of the tundish to capture the metal. An analysis of results of ultrasonic control of finished strip showed, that the basic number of the revealed defects was obtained during strip rolling out of the last slabs of the last heat in a series for a tundish. Metallographic studies determined, that the defects were located in the slab axis zone and filled by macro-inclusions of complex composition. To determine the actual distribution of metal flows, a water simulation of them was accomplished for the existing design of the EVRAZ NTMK tundish. It was determined, that at the drop of metal level in a tundish, a capture of slag from the metal reservoir and its transfer into the main bath of the tundish takes place due to whirligig flows. Following the weight metal consumption, the zone of slag inclusions distribution enlarges. Besides, denudation of the metal mirror in the metal reservoir takes place, resulted in metal secondary oxidation. Based on the results of the simulation, it was proposed to modify the design of the “turbostop”, which is installed in the metal reservoir of the tundish. Besides, it was proposed to remove the dividers installation in the tundish. It was noted, that the proposed steps enable to ensure a minimal level of rejections.

Effect of high layer thickness on surface quality and defect behavior of Ti-6Al-4V fabricated by selective laser melting

High layer thickness has been used to improve the building efficiency in Selective Laser Melting (SLM), but its application is limited due to the poor component accuracy and performance. In order to eliminate the process instability and improve forming precision at high layer thicknesses, the effects of 100 μm and 200 μm layer thickness on surface quality, density, microstructure, defect behavior and tensile properties of Ti-6Al-4V fabricated by SLM were investigated in this work. It was found that high layer thickness seriously deteriorated surface roughness rather than density and tensile properties during SLM process. Specifically, all of the generated samples had relatively coarse surfaces (Sa > 45 µm), especially for the 200-µm layer thickness samples (Sa > 95 µm), which could be smoothed over (Sa = 13 µm) by the surface re-melting process. Moreover, when the layer thickness was 100 µm, the optimal ultimate tensile strength, yield strength and elongation were 1200 MPa, 1100 MPa and 10.2%, respectively; which were consistent with those at the thin layer thicknesses used in previous researches because of the similar density and microstructure. In comparison, samples fabricated at 200 µm layer thickness exhibited lower values of 1130 MPa, 1040 MPa and 7.57%, respectively; this was due to the existence of defects, such as pores, incomplete fusion defects and slag inclusions, and the formation of different microstructures, i.e., martensite and widmanstatten.

The provenance of early Iron Age ferrous remains from southeastern Arabia

Recent excavations at Saruq al-Hadid, Dubai, have recovered more than 200 kg of ferrous remains from early Iron Age contexts dated to c. 1250-800 BCE, transforming our understanding of the scale of early iron use in southeastern Arabia. Many of these ferrous artefacts show typological parallels with contemporary objects from Luristan in western Iran, and the possibility of their long-distance import from this well-known iron producing and using region has long been recognized. The present study uses material from Saruq al-Hadid and the contemporary site of Muweilah to explore the provenance of the earliest iron from southeastern Arabia, by (i) summarizing the evidence for the iron resources and technology in the region and adjacent areas; and (ii) compositionally analysing iron ores, iron slags and slag inclusions in artefacts from Saruq al-Hadid and Muweilah, alongside Iron Age ferrous artefacts from Iran, using OM, SEM-EDS, XRF, ICP-MS and LA-ICP-MS. Multivariate statistical analyses are used to explore these geochemical data, alongside a large dataset of ores and artefacts derived from existing geochemical and archaeological publications. The study identifies slag samples from Muweilah as originating from iron smithing activities, providing the first evidence for iron working of any kind in southeastern Arabia. Differences in the geochemical compositions of the material from Saruq al-Hadid and Muweilah and iron ores from the U.A.E. and Oman – particularly the distribution of rare earth elements – suggest that Iron Age ferrous artefacts from southeastern Arabia were not smelted from locally-available iron ores. Rather, the study demonstrates geochemical similarities between southeastern Arabian iron objects, contemporary objects from Luristan, and ores of the Sanandaj-Sirjan metallogenic belt of Iran, suggesting that iron may have been imported, at least partially as complete objects, from this region. Multiple source deposits are indicated, however, and the possible contribution of iron from other regions of ancient Western Asia and neighbouring regions remains to be further explored. The research provides critical new information regarding the long-distance exchange contacts of southeastern Arabia society during the floruit of the early Iron Age, in the late second and early first millennia BCE.

Detection of slag inclusions in MMA joints with passive thermography techniques

1. Alfaro SCA, Vargas JAR, De Carvalho GC, De Souza GG. Characterization of "humping" in the GTA welding process using infrared images. J Mater Process Technol. 2015; 223: 216-224, https://doi.org/10.1016/j.jmat.... CrossRef Google Scholar

Fracture failure analysis of coal mill shaft

During the operation of No.2 boiler in a power plant, the fracture of a coal mill shaft occurred. The fracture causes of the coal mill shaft were found by macroscopic inspection, metallographic inspection, chemical composition analysis, fracture morphology analysis and mechanical property inspection. The experimental results showed that: 1. The external surface of the coal mill shaft had been welded, and the poor welding process resulted in a large number of welding defects such as cracks, slag inclusions and lack of fusion in the overlaying layer; 2. The improper hot working process of the coal mill shaft resulted in the abnormal metallographic structure of the shaft, and the existence of serious reticulated ferrite and brittle widmanstatten structure resulted in the low strength of the shaft. 3.Because of the existence of the cyclic torsion and bending stress of large load, the initial crack source occurred at the welding position of the hardfacing layer, and then extended in the form of fatigue, eventually causing the coal mill shaft to break. Three factors led the high cycle and low stress fatigue fracture of the coal mill shaft.

Effects of Ultrasonic Bending Vibration Introduced by an L-Shaped Ultrasonic Rod on the Microstructure and Properties of a 1060 Aluminum Alloy Strip Formed by Twin-Roll Casting.

In order to achieve the industrial application of ultrasonic energy in the continuous casting and rolling production of aluminum alloy, a new type of L-shaped ultrasonic rod was used to introduce an ultrasonic bending vibration into the aluminum melt in the launder during the horizontal twin-roll continuous casting and rolling process of a 1060 aluminum alloy. The effects of the ultrasonic bending vibration on the microstructure and properties of the 1060 aluminum alloy cast rolling strip and its subsequent cold rolling strip were studied experimentally, and the effect of the ultrasonic-assisted refining with different amounts of Al-Ti-B refiner was explored. The results show that under the same addition amount of Al-Ti-B refiner, the ultrasonic bending vibration can refine the grains of the cast rolling strip, make the distribution of precipitates more uniform, reduce the slag inclusion defects, and improve the mechanical properties to a certain extent. The microstructure and properties of the ultrasonic cast rolling strip with 0.18 wt% Al-Ti-B refiner or 0.12 wt% Al-Ti-B refiner are better than those of the conventional cast rolling strip, but the microstructure and properties of the ultrasonic cast rolling strip with 0.09 wt% Al-Ti-B refiner are slightly worse than those of the conventional cast rolling strip. Moreover, after cold rolling, the effect of the ultrasonic bending vibration on the improvement of the microstructure and properties of the aluminum alloy strip is inherited. A comprehensive analysis shows that the use of ultrasonic energy in this paper cannot completely replace the effect of the Al-Ti-B refiner, but it can reduce the addition amount of the Al-Ti-B refiner by 1/3.

Research on the Rupture of Certain CNG-II Gas Cylinders during the Leak-Before-Break Test

We are studying the Leak-before-break (LBB) test, which is an important test for the safety performance verification of CNG-II bottles, and it is a necessary link for new product identification. We ruptured during the LBB test of a CNG-II gas cylinder. Through the chemical composition analysis, metallographic observation, mechanical performance test, scanning electron microscope and other tests of the failed gas cylinder, we found that the cylinder failure was due to the curved part. There are oxide slag inclusions. Under the fatigue test under the action of alternating load, slag inclusions are used as the fatigue source, which accelerates the crack growth and eventually causes the cylinder to fail.

An Armour from a finery?\u2014a late medieval couter from Ogrodzieniec Castle in the Krak\xf3w-Cz\u0119stochowa Jura

The paper deals with a couter of a late fourteenth to early fifteenth century date which was found in Ogrodzieniec Castle, Zawiercie District, Poland (now in the collection of the Upper Silesian Museum in Bytom, MG 7755). The find survived in a vestigial condition, but it was still possible to propose some typological analogies to it. Metallographic examinations demonstrated that the artefact had been manufactured from almost carbon-free iron with a high content of phosphorus. An analysis of slag inclusions in the find suggests that the couter may have been made from refined blast furnace iron. It may thus be an early example of the application of indirect process iron in the manufacture of plate armour.

Waste Assessment in an Indian Casting Industry: A step towards Lean Manufacturing

In today’s era of globalization, it is essential to ensure that Indian manufacturing industries like casting and metal-working industries which work on stringent conditions of varying customer demands and constant adhering to excellent quality standards are able to flourish in the fiercely competitive environment while keeping the production as economical as possible. Hence, the need arises for continuous improvement in the manufacturing phase of the product by assessing, minimizing, and eliminating wastes of any kind. This study adopts and implements a waste assessment model in a casting industry with the purpose of assessment of wastes and hence, proceed towards a leaner manufacturing set-up. Initially, the quantification of direct relationships between the seven types of wastes was done by forming a waste relationship matrix (WRM). Next, a waste assessment questionnaire (WAQ) consisting of 68 questions, was introduced for the allocation of wastes in the industry. The results of WRM and WAQ were integrated to obtain the ranks of the seven types of wastes in the industry, and it was found that waste of defects was the highest-ranked waste followed by wastes of inventory and overproduction. Process Activity Mapping (PAM) received the highest score (482.79) in the analysis done by Value Stream Analysis Tool (VALSAT), thus, it was chosen as the preferred tool in the current situation. The results of Failure Mode and Effect Analysis (FMEA) of various defects of casting indicated sand inclusions (432) and slag inclusions (336) as the defects having the highest Risk Priority Numbers (RPN).

Structure and properties of welded joints of reinforcing bars of A500C strength class

The article presents the reasons of strength reduction of welded joints of reinforcing bars of A500C strength class. The joints were made of reinforcing steel with a diameter of 12 mm, with one of the joints made of thermomechanical hardened steel (sample 1 ), and the other – of hot-rolled steel without further processing (sample 2 ). It was established that the structure of welded joint 1 is characterized by the presence of products of tempering of martensite – martensite-bainite structure with hardness of 327 – 339 HV. Characteristic needle and packet formations are observed. The weld metal (core) has a structure identical to the structure of heat-affected zone on the overheating area. The structure of welded joint 2 is represented by more expressed zoning. The boundary is traced between the weld metal (core) and the heat-affected zone. In plane of the section, the cast core is observed as a thin light layer of 30 – 40 microns thickness and with hardness of 180 – 190 HV; it consists of ferrite, not fully subjected to post-welding heat treatment. Also slag inclusions present in all volume of the welded joint metal. In the heat affected zone, in the area of overheating the widmanstatten bainitic structure is also observed. Metal hardness of the heat-affected zone is at the level of 250 – 265 HV. The most likely reasons for the reduced strength of welded joints are increased fragility of the weld metal and the zone of thermal influence, due to the high hardness, more than 300 HV, as well as the presence of slag inclusions in the weld metal of the joint (core), which act as stress concentrators and under external loads are a source of destruction.

Ancient armour provenance by LA-ICP-MS analysis of microscopic slag inclusions

Improvement of an LA-ICP-MS methodology tailored to quantify trace elements in small slag inclusions and application to armour for provenance study.

Technological aspects for formation of defects during welding of main pipelines

During the construction of main pipelines, welding is the main source of the formation of defects, therefore, to minimize them, monitoring and documentation of welding are performed. Analysis of the characteristic defects of the welds showed the dominance of internal formation defects in the form of pores, slag inclusions and lack of fusion. It is established that the main reason for the formation of such defects is craters on the surface of previous passes, which are formed during arc breaks or underestimated range of electrode transverse vibrations. To increase the effi ciency of monitoring for the arc welding processes with fi xing the current and the arc voltage, it is proposed to develop special intelligent module that estimates the parameters of electrode transverse vibrations, change in the energy parameters of the arc, and based on these data predicts the probability and place of formation of defects in the welded joint.

Virtual study of conditions for occurrence of non-metallic inclusions under consumable-electrode multiple-pass welding of pipe-lines

The causal factors for the occurrence of non-metallic inclusions in the form of slags, complex oxides and sulfi des under multi-pass arc welding analyzed. It is assumed that lack of fusion in interlayers and slag inclusions are formed on the surface of the beads of previous passes if slag residues in craters exist arising from short interruptions of arc burning, or lack of fusion at bevelled edges. The virtual study is carried out using physical and mathematical model, the features of which are fi xing the level of the melt at the solidifi ed front of the weldpool and introducing into it description of non-metallic inclusions fi lling cavities in the surface crater or lack of fusion at the side face of the groove. The results of numerical simulation of the remelting process of slag residues in different welding modes and with different sizes of slag inclusion are presented. It is shown that, with signifi cant depth of craters or lack of fusion, comparable with the thickness of the deposited layer, it is diffi cult to create conditions for their rise to the surface of the weldpool even at the maximum permissible arc current.

Mechanical properties of waste copper slag filled surface activated jute fiber reinforced composite

In this work, the fabrication of the jute fibre reinforced composites are made with the help of the compression moulding technique using the optimum pressure (17 Mpa) along with various fiber dosage (i.e. 0%, 40%, 50%). The optimized condition is obtained for the 40% fiber loading composites in the mechanical properties, then fiber activation is followed by using the NaOH and Ca(OH)2. The treated fibers composites by adding the copper slag in the range of 0%, 5%, 10%, 15% for the optimized 40% fiber dosage are produced using the unsaturated polyester as matrix. The ejected the specimen is cut as per ASTM to find the mechanical properties such as tensile, flexural and impact. Result revealed that the Ca(OH)2 treated composite shows better tensile, and impact strength for the 10% copper slag filled composite material and yields higher for 15% for copper slag filled composites in the case flexural strength. Nearly 25% and 22% increase in tensile strength and impact strength was observed for the Ca(OH)2 treated composite with 10% copper slag inclusion. The 15% copper slag inclusion composite yielded the higher flexural strength. The SEM mechanism revealed the higher mechanical strength for the Ca(OH)2 treated composite than other composites produced with activated fiber.

Effect of Flow Field on Surface Slag Entrainment and Inclusion Adsorption in a Continuous Casting Mold

A water model of slab mold was established to analyze the flow field behaviors. Particle image velocimetry measurement, fluctuation sensors, and industrial experiments were adopted to analyze the slag entrainment and inclusion adsorption. The risk of surface slag entrainment was discussed from the perspectives of flow patterns, surface fluctuation, and velocity. The ability of mold slag to adsorb inclusions was discussed by electrolysis on slab samples. The results reflected that the flow field determined the fluctuated amplitude, surface pattern and flow velocity of the mold surface, playing an important role in the slag entrainment and inclusion adsorption. Uneven surface fluctuations and downward vertical velocity lead to high slag entrapping risk. High surface horizontal velocity in mold leads to a higher inclusion concentration gradient at the slag‐steel interface, which leads to a stronger ability of mold slag to adsorb inclusions.

Steelmaking in India - new evidence from microscopic and archaeometallurgical analysis from middle Ganga plain, Balirajgarh.

The present study deliberates on the archaeometallurgical examination of 2300 years old excavated iron nail from India's middle Ganga plain of Balirajgarh. The nail was subjected to multianalytical investigations in order to determine the raw materials used, manufacturing technology and preservation state. The combined analytical techniques optical microscopy, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX), Vickers hardness and X-ray diffractometry shed light towards the characterisation and use of the iron artefact. Special attention was paid for qualitative and quantitative analysis of slag inclusions, metal matrix and corrosion products. The presence of heterogeneous microstructure and inclusion of impurities suggests that nail has been produced through the direct process and work hardened. The noncorroded nail is made of hypereutectoid steel and used for building purpose. The study is important to understand the role of technology in the evolution of cultural changes in India that also provides archaeometric data on the method used in the forging work.

Microstructure and mechanical property of SiC whisker coating modified C/C composite/Ti2AlNb alloy dissimilar joints prepared by transient liquid phase diffusion bonding

SiC whisker coating was prepared on the surface of C/C composite successfully by CVD, and transient liquid phase (TLP) diffusion bonding was employed to realize the joining of SiC whisker coating modified C/C composite and Ti2AlNb alloy using Ti–Ni–Nb foils as interlayer. The microstructure, shear strength and fracture behavior were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD) and universal testing machine. The results show that SiC has good compatibility with C/C composite, and gradient interface formed between SiC-modified C/C composite and Ti2AlNb alloy. When the bonding experiment was carried out under bonding temperature of 1040 °C and holding time of 30min with 5 MPa pressure in vacuum, the joints formed well and no obvious defects can be observed. The typical microstructure of joints is C/C composite/SiC + TiC/Ti–Ni compounds + Ti–Ni–Nb solid solutions/residual Nb/diffusion reaction layer/Ti2AlNb alloy. With the increasing of bonding temperature, the thickness of joining area increased due to sufficient element diffusion. However, when bonding temperature is elevated to 1060 °C, some defects such as cracks and slag inclusions exist in the interface layer between interlayer and Ti2AlNb. The joints with maximum average shear strength of 32.06 MPa are bonded at 1040 °C for 30min. C, SiC and TiC can be found on the fracture surface of joints bonded at 1040 °C which indicated that fracture occurred at the interface layer adjacent SiC layer.