New Methods, New Opportunities. Recent Advances in Archaeological Science and their Application in Arms and Armour Studies

The jubilee of Professor Andrzej Nadolski and Professor Marian Głosek is an excellent opportunity for discussing some most recent methods of technological analyses in archaeology and their applications in arms and armour studies. New opportunities are offered by Computed Tomography (CT) and by Neutron Imaging (NI). The latter is insensitive to material density; therefore details that are not detectable by X-ray or CT can be seen in NI images. A considerable progress has also been made in the field of radiocarbon dating. Yet another field are analyses of the chemical composition of smelting slag and slag inclusions in ferrous artefacts. Such analyses can be used for identification of smelting processes, as well as for provenance studies. These take a number of variables into consideration (major and trace elements, as well as isotopic ratios). What seems to be especially promising in provenance studies are isotopes of osmium (Os).

Research of the Microstructure of the Deposited Layer during Electric Arc Surfacing with Control Impacts

Electric arc surfacing is widely used for the application of protective and restorative coatings on units and parts of metallurgical production equipment in order to increase their durability in harsh operating conditions and in an aggressive environment. Increasing the efficiency of melting the electrode material is an important task, since it allows one to reduce the required volume of deposited metal and the cost of surfacing. In addition, when surfacing by traditional technology of parts with a complex shape of the working surface, it was found that the deposited layer can contain such defects as single gas and line pores, as well as slag inclusions. The work is devoted to the study of improving the surfacing technology by controlling heat input into the base metal using controlled mechanical actions.

Features of structure and properties formation in welded joints made of A500C and B500C strength classes reinforcing steels

In the manufacture of welded reinforcing mesh, rolled products of various strength classes are used. High requirements for mechanical properties and structural condition are imposed on welded joints. Connections must provide a set of operational properties. This article presents the results of studies of the structure and mechanical properties of welded joints of reinforced rolled products of strength classes A500C and B500C, performed by spot welding. It is established that the weld (core) of A500C strength class steel is characterized by the presence of a layer of cast metal (hardness 180–190 HV) with slag inclusions. In the heat-affected zone, widmanstett ferrite and bainite — like structures with a hardness of 251–268 HV are observed. The temporary breaking resistance of A500C steel joints is 322–350 MPa. It is shown that the welded joint of steel of strength class B500C does not have a clear division into structural zones. Similar bainite structures in the form of batch formations are observed in the seam and the heat-affected zone. The hardness of the metal of the welded joint is in the range from 205 to 241 HV, and the level of temporary resistance is 510–525 MPa. It is established that the probable cause of premature failure of welded joints of A500C steel is the presence of large slag formations in the metal seam (core). This may be due to insufficient cleaning and preparation of the weld site. Particles of scale and other contaminants fall into the molten metal of the core and "freeze" in it, forming slag inclusions. Cavities filled with slag reduce the cross-section of the seam and as a result significantly weaken it. In addition, slag inclusions are additional stress concentrators and act as a source of destruction when an external load is applied. For the manufacturer of reinforcing nets, it is proposed, as a technological recommendation, to use additional tools for cleaning the welding site in the form of metal brushes or abrasive tools with additional surface degreasing.

Distribution on microhardness, chemical composition and structure over a layer of heat-resistant highyardness alloy formed by multilayer plasma surfacing in a nitrogen medium

Microhardness distributions, surface morphology, and elemental composition of a deposited layer of a heat-resistant alloy of the type P2M8U steel formed by plasma surfacing in a protective-alloying nitrogen medium are studied. It was established that the surfacing technology and surfacing material allows to obtain a high-quality deposited alloy without cracks, pores, slag inclusions and defects of macro- and microstructure. It has been established that the deposited material is pearlite grains at the boundaries and grain junctions of which are carbonitrides based on iron, tungsten, chromium, molybdenum, aluminum (Fe6 W6 NC and AlN).

The Sectors Workpieces and Drum Reel’s Die Cubes Electroslag Casting with Exothermic Electrical Conductive Fluxes

It has been established that the developed method of manufacturing workpieces for the sectors of the drums of X20CrMoWV3 steel reel’s and die cubes from X5CrNiMo steel using a solid start and exothermic flux significantly reduces the complexity of their manufacture. The cast reel’s drum sectors workpieces and die cubes, obtained by the electroslag remelting (ESR) method, had a smooth surface without corrugations, sinkers, and slag inclusions. Heat treatment provides the required mechanical properties and the absence of flocs in the cast electroslag metal. An effective way to increase the performance of electroslag processes is using the exothermic flux, which contain scale, ferroalloys, aluminum powder and standard flux (welding flux ISO 14174 – S F AF3, etc.) in quantities sufficient for the exothermic reactions to occur, which ensures the generation of additional heat in the starting period of electroslag processes and contributes to the accelerated induction of the slag bath of the required volume at the “solid” start both monofilar and bifilar schemes of conducting the process instead of the “liquid” start. Electroslag processes using an exothermic alloyed flux on a “hard” start allow to obtain (compared to existing methods of slag bath formation) an increasing in the output of a suitable metal 2...10 %; saving on melting 1 kg of standard flux 1.2...1.4 kW h; reducing of the starting time of the ESR process to 25 %.

Detection of slag inclusions using infrared thermal imagining system

Assuring high quality of welded joins is a vital task in many industrial branches also when joints are made manually. It is the case metal-arc welding with covered electrode. One of main imperfection, that can occur in this process is slag inclusion. In the paper an method for detection of slag inclusion in multipass manual welding is proposed and validated. The key idea of the method is that small temperature disturbances will be noticeable in consecutive cross-section of joint in the cooling pass. Temperature distribution weld face was measured with longwave infrared camera (LWIR). For consecutive cross-section made in IR representation of joint differences in mean temperature was calculated to assess the cooling rate directly after the elements were welded. It can be made because on each thermogram the whole joint is visible, thus position of electrode in time can be easily marked. Results of slag inclusion detection were compared with radiographic images of made joints. In the future additional studies will be performed in order to generalize proposed method to wider group of materials and for more complex welds.

Deciphering the Iron Provenance on a Medieval Building Yard: The Case of Bourges Cathedral

This paper presents the provenance study of the iron reinforcements of Bourges Cathedral (13th c.): the links of a 100 m long iron chain, surrounding the eastern parts of the cathedral at the triforium level and 4.5 to 5 m long tie-rods consolidating the arches of the inner aisle at the same level. The analytical methodology is based on the determination of trace rare earth elements analyses by LA-ICP-MS in the slag inclusions of the artefacts and in the slag found on candidate production sites combined with statistical approaches. This chemical approach is crossed with archaeological and historical studies on the monument itself and on the production sites. Ninety-nine iron samples were analyzed on the bars and chains and 238 iron slags from 3 presumed areas of supply. For the first time, iron circulation and trade around a single building yard over a time of 30 to 40 years is studied with a precision never obtained before with historical sources. It shows that mainly four different metallurgical districts, local and more distant, supplied the building yard, mostly depending on the construction phases and also on the types of iron armatures needed.

Metallurgical Model of Diffusible Hydrogen and Non-Metallic Slag Inclusions in Underwater Wet Welding of High-Strength Steel

High susceptibility to cold cracking induced by diffusible hydrogen and hydrogen embrittlement are major obstacles to greater utilization of underwater wet welding for high-strength steels. The aim of the research was to develop gas–slag systems for flux-cored wires that have high metallurgical activity in removal of hydrogen and hydroxyl groups. Thermodynamic modeling and experimental research confirmed that a decrease in the concentration of diffusible hydrogen can be achieved by reducing the partial pressure of hydrogen and water vapor in the vapor–gas bubble and by increasing the hydroxyl capacity of the slag system in metallurgical reactions leading to hydrogen fluoride formation and ionic dissolution of hydroxyl groups in the basic fluorine-containing slag of a TiO2–CaF2–Na3AlF6 system.

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.