Eva Schmidová

Mechanism of degradation of stabilized corrosion‐resistant steel during the welding cycle

Purpose – The purpose of this paper is to clarify the destabilisation mechanism that occurs with two types of ferritic corrosion‐resistant steel during the welding cycle.Design/methodology/approach – A series of experimental weld joints was made to verify the actual response of non‐stabilised corrosion‐resistant steel, and of the same steel that had been stabilised by added titanium. The character and extent of the ensuing structural changes were analysed. The essential characteristics of degradation in the heat‐affected zone are evaluated using optical and scanning electron microscopy; individual phases are identified by means of EDX microanalysis. The underlying mechanism for the loss of stability is induced experimentally in several stages; depending on the thermal doping level and interaction with the environment during the welding process, phases of various types are precipitated. These phases subsequently are studied in connection with the original microstructural characteristics of the steel and th...

Mechanical Properties of Steel P92 Welded Joints Obtained By TIG Technology

Mechanical properties of P92 steel welded joints obtained using the TIG (141) technology have been studied upon post-welding heat treatment (PWHT). The microhardness, tensile strength, and impact toughness of metal in the weld and heat-affected zone are determined. The PWHT is shown to be obligatory.

The weldability of the steel with high manganese

Jedan od najvažnijih dijelova koji se danas koriste na željeznici su dijelovi na cestovnim prijelazima preko pruge i uglavnom dinamicka komponenta izložena djelovanju. Mangalloy, također poznat kao celik s manganom ili Hadfield celik, je celik s legurama koje u prosjeku sadrže 13 % mangana i jedinstven je po tome sto povezuje visoku žilavost i duktilnost s velikom sposobnoscu radnog otvrdnjivanja. Otpornost na trosenje prije kontaktnog trosenja ovisi o intenzitetu otvrdnjavanja povrsine i postupku otvrdnjavanja tijekom rada [1, 2, 3,]. Buduci da se zbog otpornosti abraziji povecava postotak ugljika iznad 1,4 % i vise, može se pojaviti problem postizanja homogene austenitne strukture koja bi bila bez zrnaca karbida [4].

The Possibilities of Evaluating the Yield Strength in the Heat Affected Zones of a Weld through Indentation

The research focuses on elastic-plastic behaviour of welded joints of materials which are commonly used in both constructional practice and the automotive industry. The examined welded joints are oriented to a common constructional S355 and a modern high-strength steel DOMEX 700MC.The main tool for the assessment of the elastic-plastic response was the methodology based on the instrumented penetration testing with the use of a cylindrical indenter. The indentation tool was applied into narrow zones of welded boundaries. These zones represent critical areas of welded constructions because of a changing structure and different mechanical properties than the basic material possesses. The indentation data were recalculated to the mechanical properties in shear with the help of Hencky ́s hypotheses about material behaviour. The correctness of the used methodology was verified by a tensile test. The aim of the work is to determine optimal methods for defining a yield strength and to find a hardening trend in the zones. The comparison of these steels revealed different changes due to the welding process. A substantial decrease of the yield strength of Domex700MC was observed, as a contrary to a stable, or partially increased, yield strength of the S355 steel. Structural analyses revealed a different material response of the evaluated steels, according to a different hardness in the heat affected zone.

Rolling-Contact Hardening Evaluated by Indentation

The operational degradation of surface layers due to a rolling contact process was simulated for Hadfield steel by a special testing rig. A specific limited state based on cumulative depletion of plasticity was achieved.Precise evaluation of the surface layers mechanical parameters is necessary for a service life prediction. Very low depth of localized dislocation hardening process doesn ́t allow the standard mechanical testing. The comparative instrumented indentation tests using Vickers and cylindrical indenter were used for evaluation of defined stage of surface degradation process. The intensity and reach of deformation hardening are partially limiting for particular methodology. The yield stress of surface layers was estimated according to an analytical model of uniaxial vs. indentation plastic flow ratio.

Influence of the welding process on martensitic high strength steel

The subject of the study is martensitic 22MnB5 steels, which are used in the automotive industry. The main purpose of the performed analyses is a study of strength differences in heat affected zones of the spot welding. For the needs of the strength decrease assessment, the critical layer of the heat affected area was experimentally simulated. The aim of the work is to determine the most suitable methodology for evaluating the local changes of the elastic-plastic material response. The aim of this work is to determine the optimal methods for the determination of the yield strength and to find a firming trend in these zones.

Testing of pigmented coatings on thermal sensitised stainless steel

Purpose – The purpose of this paper is to verify the capability of pigmented coatings to mitigate the effects of thermal sensitisation of 430 stainless steel.Design/methodology/approach – Experimental weld joints of non‐stabilised ferritic corrosion resistant steel type AISI 430 were prepared. Protective coatings in several variants were applied to a number of weldments, subsequently subject to corrosion tests in SO2 and NaCl. The anticorrosive efficiency of the coatings was evaluated by means of normative visual assessment and metallographic analysis of the mechanism and depth of corrosion damage.Findings – Anticorrosive efficiency of the tested coatings was experimentally established under conditions where differences were identified in structural changes caused by welding, or resulting from mechanical damage to the coating. Differences in the progress of corrosion damage caused by phase changes in the heat‐affected zone were established.Practical implications – Tests of anticorrosive efficiency of coat...