Weldability prediction of high strength steel S960QL after weld thermal cycle simulation

This paper presents weld thermal cycle simulation of high strength steel S960QL, and describes influence of cooling time t_8/5 on hardness and impact toughness of weld thermal cycle simulated specimens. Furthermore, it presents analysis of characteristic fractions done by electron scanning microscope which can contribute to determination of welding parameters for S960QL steel

Dependence of hardness and impact energy on cooling time Δt8/5and temperature for S960QL

The paper deals with research into dependence of hardness and impact energy of thermal cycle simulated specimens of fine-grained structural steel S960QL on cooling time from 800 to 500 °C and on tested temperature. Results were obtained by measuring hardness of HV 10 and by experimental testing of Charpy notched tubes on instrumented Charpy hammer. Total impact energy, initiation energy and fracture propagation energy needed for occurrence of fracture is also elaborated. Key words

Resistivity during cycle loading of fine grain heat affected zone (HAZ) of 17CrNiMo7 steel prepared into laboratory furnace

Structural components which are loaded in cyclic load mostly fail due to fatigue. The fatigue strength of metals as well as weld joint regions in metals depends on mechanical properties especially hardness, the size of defect and the size of grains. Resistivity of the fine grain HAZ prepared against fatigue crack initiation will be explained in this article. Samples of material with martensitic fine grain microstructure were prepared by laboratory furnace by proper thermal treatment. Mechanical properties of fine grain heat affected zone and its microstructure were investigated. Special attention was given to behavior of fine grain during the cycle loading under stress concentration. Stress concentration was similar to the one in real welds. The S-N curve and the fatigue limit were determined. The Paris curve and the threshold for crack propagating were also determined

Impact energy analysis of quenched and tempered fine grain structural steel specimens after weld thermal cycle simulation

The paper presents impact energy results of thermal cycle simulated specimens of quenched and tempered fine grain structural steel S960QL. These results are obtained by examining notched Charpy specimens. Upon performed metallographic analysis and measured hardness, total impact energy is separated into ductile and brittle components

Impact energy analysis of quenched and tempered fine grain structural steel specimens after weld thermal cycle simulation

The paper presents impact energy results of thermal cycle simulated specimens of quenched and tempered fine grain structural steel S960QL. These results are obtained by examining notched Charpy specimens. Upon performed metallographic analysis and measured hardness, total impact energy is separated into ductile and brittle components

Weldability of microalloyed high strength steels TStE 420 and S960QL

The paper presents research of weldability of microalloyed high strength steels TStE 420 and S960QL after weld thermal cycle simulation. Beside mechanical properties hardness and impact strength, the microstructures of characteristic weld thermal cycled structures for both steels are given. The results will contribure to determination of weakest points in Heat Affected Zone of both steels

Ponašanje grubozrne zone utjecaja topline zavara tijekom cikličkog opterećenja

This paper presents results of a study on martensitic coarse grain heat affected zone that can appear in welded joints. Mechanical properties of martensitic coarse grain heat affected zone and its microstructure were investigated. Special attention was given to its behaviour during the cycle loading under stress concentration. Stress concentration was similar to the one in real welds. The S-N curve and the fatigue limit were determined. The Paris curve and the threshold for crack propagating were also determined.U radu se istražuje martenzitna grubozrnata zona utjecaja topline koja se može pojaviti pri zavarivanju. Istražena su mehanička svojstva i mikrostruktura ove zone. Posebna je pažnja posvećena njenom ponašanju tijekom cikličkog opterećenja kada je prisutna koncentracija naprezanja. Koncentracija naprezanja je slična onoj kod realnog zavarivanja. Određena je S-N krivulja i granica umaranja. Također je određena i Parisova krivulja i prag propagacije pukotine

Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material

Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material is presented in this paper. The research is done on a hot strip mill working roll where High Chromium Steel is used for roll’s shell material. To obtain corresponding parameters, a rectangular single edge notched bend specimens – SENB, according to standard BS 7448, were used. The fatigue crack growth analysis was done on a resonant testing machine with use of special crack gauges, while for fracture mechanics parameters the electro–mechanical testing machine was used

Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material

Fatigue crack growth and fracture mechanics analysis of a working roll surface layer material is presented in this paper. The research is done on a hot strip mill working roll where High Chromium Steel is used for roll’s shell material. To obtain corresponding parameters, a rectangular single edge notched bend specimens – SENB, according to standard BS 7448, were used. The fatigue crack growth analysis was done on a resonant testing machine with use of special crack gauges, while for fracture mechanics parameters the electro–mechanical testing machine was used

Nastanak zamorne pukotine iz mikrostrukturno malih vickersovih otisaka

The resistivity of a coarse grain steel against fatigue crack initiation in presence of micro-defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as artificial micro-defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.Proučavana je otpornost grubozrnatog dijela zone utjecaja topline na nastanak zamorne pukotine u prisustvu mikro greški. Uzorci materijala s martenzitnom grubozrnatom mikrostrukturom pripremljeni su odgovarajućom toplinskom obradom. Kao umjetne mikro greške upotrijebljene su mikrostrukturno mali Vickers otisci. Tlačna zaostala naprezanja pojave se zbog nepovratnosti plastične deformacije. Moment kad se napravi otisak omogućava pripremu uzoraka s i bez efekata zaostalih naprezanja. Kritičkna razina naprezanja za nastanak pukotine zavisi od stvarne veličine otiska. Na lokaciju nastanka pukotine utječe i prisutnost te vrsta zaostalih naprezanja