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Steel heavy plates, grade S355, micro‐alloyed with Vanadium‐V and/or Niobium‐Nb plus Titanium‐Ti in thicknesses from 5 to 60 mm, 200.000‐350.000 t/y, are produced according to EN 10025 at STOMANA S.A., a company of the SIDENOR Group in Pernik Bulgaria, and are exported to the European Market. These plates fulfil high quality standards as they are used for constructions and engineering applications (e.g. high‐building constructions, bridges, shipping applications, cranes, etc.). Often intermediate and/or final products (slabs and plates, respectively) suffer from surface and/or internal defects, which deteriorate the final product's quality. The purpose of this paper is to look at the challenging task of eliminating the external and especially the internal defects.

ELKEME performs root‐cause analysis and proposes improvement actions. For these purposes light optical metallography (LOM) and scanning electron microscopy (SEM) with EDS were applied. For the analysis a NIKON SMZ 1500 stereoscope (up to 100x), a NIKON epiphot 300 inverted metallographic microscope (up to 1000x) and a Philips XL‐40 SEM were used.

Most surface defects are attributed to copper (having its origin mainly from scrap or from mould's wear due to bad lubrication), or casting powder entrapping, cracks at deep oscillation mark points or transverse cracking, with the majority occurring during continuous casting. High‐copper amounts in the steel cause hot shortness issues. Hot tears in the surface of “as‐cast” material lead to flakes and tears in the plates after hot rolling. The torn surfaces are heavily oxidized and decarburized if oxidizing‐conditions exist in the reheating‐furnace. Internal defects are related with large‐concentrated MnS stringers and entrapped in the steel desoxidation products. Additionally, based on carbon amount of the cast steel, macro‐segregation can lead to crack initiation and propagation along the centreline.

This work refers to industrial research widely applied and focused. Sampling and root cause analysis is never easy in an industrial environment. The most difficult part is to identify the critical process conditions that reflect to negative quality issues in the final product.

Internal defects, especially centreline segregation and inclusion clustering, are important imperfections that deteriorate material properties and jeopardize the products’ structural integrity. The paper discusses possible root‐causes in relation to the overall production processes, concluding in improvement actions for in‐plant operation given the equipment limitations of the very specific production site.

Identification of the critical process conditions that enhance Cu diffusion in ferrite grain boundaries and promote precipitation of Cu-rich particles in the proximity of steel semi-finished products surface is crucial for every steel maker as it leads to the creation of hot shortness cracks in final products deteriorating surface condition. The purpose of this paper is to reveal the possible effect of Cu segregation in the metal/oxide interface, its role in surface crack initiation and, finally, to propose actions to prevent from hot shortness issues throughout the production chain of steel products.

The here presented study was based on S355 steel plate production starting from re-melting of scrap in an EAF, followed by metallurgical treatment in a Ladle Furnace, continuous casting, re-heating (RH) and thermo-mechanical rolling in a reversing mill. For the purposes of this study, more than ten heats, 100 t of steel each, were analyzed. Here presented are depicted steels in the high and low end of the permitted Cu-wt-% spectrum, 0.4 wt-% Cu (0.15 wt-% C, 1.1 wt-% Mn, VTi micro-alloyed steel) and 0.25 wt-% Cu (0.09 wt-% C, 1.2 wt-% Mn, NbTi micro alloyed steel), respectively.

Although Cu levels of 0.25-0.40 wt-% are well below the Cu solubility in austenite and ferrite (8 percent wt-% and 3 wt-% Cu, respectively) and within specifications, precipitation of Cu-rich particles is observed in industrial semi-finished and/or final products. Cu-rich precipitates and Cu segregation along grain boundaries near the steel surface lead to hot shortness cracks in industrial products.

Hot shortness surface defects related to Cu presence in steel having significantly lower Cu amounts than its maximum solubility in austenite and ferrite does not make sense in first place. Correctly, Cu is expected to remain in solid solution. Identification of Cu-rich particles is explained on the basis of the development of double diffusion actions: interstitial diffusion of carbon (decarburization) and substitution diffusion of copper. Root cause analysis and reliable countermeasures will save financial and material resources during steel production.

Automobile scrap re-melting results in noticeable Cu amounts in EAF produced steel. Presence of Cu-rich particles in grain boundaries near the surface of intermediate or final products deteriorates surface quality through relevant surface defects. Identification of Cu-rich particles is explained on the basis of the development of double diffusion actions: interstitial diffusion of carbon and substitution diffusion of copper. Pre condition for metallic Cu precipitation in ferrite is the Cu amount to be above 3 wt-%, which is ten times higher than the usual permitted Cu amount in such steel grades. This pre-condition is met through austenite oxidation during RH.

To determine if the interim use of liquid waste as a fuel in a catalytic steam reformer unit had any deleterious effect on the long‐term life of the reformer tubes.

Standard metallographic techniques were used to prepare representative samples obtained from various sections of the reformer tubes for metallurgical evaluation. Microstructural characterization was carried out in a scanning electron microscope equipped with an energy dispersive X‐ray spectrometer. Imaging and elemental analysis was used for the identification of the alloy material, corrosion products and other microstructural features.

Hydrogen was produced in a catalytic steam reformer by cracking methane using natural gas as a fuel. Corrosion of reformer tubes occurred when natural gas fuel was replaced with a liquid waste. Use of liquid fuel waste accelerated the rate of oxidation at the outer tube surface. However, foreign species from the fuel were not transported into the tube material. The heat‐resistant steel casting used for this application was susceptible to precipitation of Si‐stabilized Ni‐Nb Laves phase, thus reducing rupture life of the component. Voids at grain boundaries indicative of creep damage were observed.

Although, the interim use of liquid waste fuel appeared not to have damaged the tubes, it was concluded that the expected service life of the tubes may not be realized because of the susceptibility of the material to precipitation of Laves phase. An Fe‐base superalloy UNS N08810 or UNS N08811 was recommended as a replacement material for this application.

This paper provides an account of a failure analysis study. It identifies incorrect materials selection for a particular application and suggests better alternative along with its justification. The information is deemed useful for plant designers and engineers working in the related industry.

The purpose of this study is to investigate the microstructural evolution of high-strength 2024 Al alloy prepared by the laser powder bed fusion (L-PBF) additive manufacturing (AM) route. The high-strength wrought Al alloy has typically been unsuitable for AM due to its particular solidification characteristics such as hot cracking, porosity and columnar grain growth.

In this research work, samples were fabricated using L-PBF under various laser energy densities by varying laser power and scan speed. The microstructural features that developed during the solidification are correlated with operating laser parameters. In addition, finite element modelling (FEM) was performed to understand the experimentally observed results.

Microstructure evolution and defect formation have been assessed, quantified and correlated with operating laser parameters. Thermal behaviour of samples was predicted using FEM to support experimental observations. An optimised combination of intermediate laser power and scan speed produced the least defects. Higher energy density increased hot tearing along the columnar grain boundaries, while lower energy density promoted void formation. From the quantitative results, it is evident that with increasing energy density, both the top surface and side wall roughness initially reduced till a minimum and then increased. Hardness and compressive strength were found to decrease with increasing power density due to stress relaxation from hot tearing.

This research work examined how L-PBF processing conditions influence the microstructure, defects, surface roughness and mechanical properties. The results indicates that complete elimination of solidification cracks can be only achieved by combining process optimisation and possible grain refining strategies.

During steel plate and long-product production, numerous imperfections and defects appear that deteriorate product quality and consequently reduce revenue. The purpose of this paper is to provide a practical overview of typical defects (surface and internal) that occur and their root causes.

The data presented here derive from the quality department and from more than 50 technical reports of ELKEME S.A. on the last decade’s production of steel making companies STOMANA S.A. and SIDENOR S.A., with emphasis on the defects occurred in some of the products of the Bulgarian plant. Stereoscopic observations of surface defects, light optical metallography, and scanning electron microscopy with EDS represent the most used techniques to characterize defected macro-/micro-areas and microstructures.

In general, the most commonly encountered defects from semi-finished (billets, blooms, and slabs) and final (round bar and plate) steel products are as follows: network cracks, porosity, gas holes, shrinkage, shell, slivers, casting powder entrapment, ladle slag entrapment, other non-metallic inclusions, low hot ductility, centerline segregation cracking, macro- and micro-segregation, and mechanical defects (scratches, transverse cracks, and seams).

External and internal quality improvement can reduce the production cost (Euro/ton).

Improvement of the quality of industrial plates and long products increases the safety of the further-produced constructions and systems such as bridges, cranes, heavy equipment, automobile parts, etc.

Root cause analysis and categorization of the most commonly encountered defects can pave the way to production process improvements that directly affect final product quality and the overall per ton production cost. The benefits of this work obviously affect all steel producers/processers, and also society through the safety increase achieved by the quality improvement in the steel products used in constructions and automobile parts.

THE specialities of my Company are the manufacture and application of those aluminium alloys which gain their high strength by suitable forms of heat treatment. Our main business has been to satisfy the demand of the designer of aircraft and aero‐engines who is influenced by two major considerations—reliability and weight.

PROBABLY one of the most remarkable features of our generation has been the ability of the metallurgist to produce alloys meeting the current needs of industry in providing the requisite mechanical characteristics, capabilities of being manipulated or fashioned by established methods, and in particular instances, specific properties of resistance to erosion, corrosion, wear, impact and fatigue. Perhaps this adaptability is best exemplified in the case of light alloys, whereby scientific alloying of aluminium or magnesium bases with other elements, combined with specific thermal treatments, have imparted increased strength, durability, and, under limited conditions, resistance to corrosion, to a whole range of alloys without any appreciable sacrifice of the great advantage in initial lightness of these two base metals. In view of this, these metals, which are conveniently designated “light alloys,” have become exceedingly popular, particularly since the majority of them are eminently suitable for fabrication in the form of diecastings, which permit the reproducibility of exact forms in large quantity production. The mechanical features of light alloys, together with their capacity to be machined, or otherwise finished to shape and dimensions, are fairly widely known, but their ability and relative merits to resist various conditions of corrosive influence are not so clearly elucidated. The readers of this journal arc naturally concerned primarily with finishes of protective value rather than with those of decorative importance. In general engineering considerable confusion exists as to the behaviour of aluminium and its alloys under deleterious influences, and this tends to retard their general adoption, even though their individual mechanical properties may make them highly desirable. In some cases most unnecessarily elaborate finishes are applied for ultra precautionary purposes, while in others a complete ban is exercised rather than incur any risk. In the aircraft industry, on the other hand, the demand for minimum weight consistent with requisite strength has provided the impetus for their adoption, which in turn has led to the development of appropriate finishing methods. Even in this sphere a comparative survey of finishing methods and their efficiency covering a range of popular alloys should prove to be of interest.

This article, Part I of which appeared in last month's CORROSION TECHNOLOGY, is intended to provide a comparison of the corrosion‐and heat‐resistant steels specified in Great Britain and the U.S.A. for use in the Petroleum Industry. The article is a condensed version of the paper presented at the 1957 International Petroleum Equipment Conference.

A variety of lead‐free solders are now commercially available. Of those suitable for mass soldering perhaps the ones closest to a direct, drop‐in, replacement for tin‐lead are the tin‐zinc‐bismuth alloys. For most tin‐based solders it is the tin which is the active element and dominates the all‐important interfacial reactions. As a result they have many properties in common. The addition of zinc, however, radically alters this picture. Zinc oxidation products are formed at the surfaces. Zinc intermetallic compounds are also formed in preference to tin‐compounds at the substrate interfaces. The nature and implications of these changes are outlined for the common basis materials.

MAGNESIUM, because of its low density, has obvious possibilities as an aircraft structural material. The useful magnesium alloys have densities in the range 1·76 to 1·83, compared with the aluminium alloys range of about 2·5 to 2·8. The melting point of magnesium is 650 deg. C., almost identical with that of aluminium (660 deg. C.), so that generally the alloys of each of these base elements have applications in much the same temperature band.