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1
Content available remote Temperature impact on delayed fracture of creep-resistant steels welds
Skulskyi V., Nimko M.
Journal of Achievements in Materials and Manufacturing Engineering
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2018
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Vol. 88, nr 1
5--11
EN
Purpose: Phenomenon of delayed fracture (or cold cracks formation) of hardenable steels weldments had been widely investigated. But temperature dependence of cracking susceptibility remained discussable, because there was no strict vision of temperature border for the cracking risk appearance, when joints are cooling after welding completion. The proposed paper aimed at assessment of dangerous temperature range at which delayed fracture, mainly for the steels with martensite formation, becomes most probable. Design/methodology/approach: The “Implant” test, conducted under isothermal conditions at the temperatures selected within the range from 160 to 20°C on cooling of the completed test weld joint, was used. Basing on the obtained thermokinetic characteristics of the cracking, the activation energy E of the fracture process was calculated. Comparing of the found E values with the close values of E for the known processes developing in steels, the explanation of the revealed cracking behaviour at different temperatures was proposed. Findings: Delayed cracking of the martensitic weld joints has started to manifest at the temperatures lower than 140°C. Dependence of the cracking period from the temperature is described by C-type curve with the minimum cracking duration within 80-100°C. Using the approach of the activation energy assessment for different temperature ranges (140 to 100°C and 80 to 20°C), the effect of the diffusible hydrogen and a martensite decay on the cracking thermokinetics was considered. Research limitations/implications: Additional investigations of the fine microstructure after different stages of the low-temperature martensite decay could be necessary for deepening understanding of a role of this process in the low-temperature heterogeneity formation and cracking susceptibility. Practical implications: Results widen data on weldability of actual for industry steels and give a ground for consideration of the technological approaches for their welding. Originality/value: Temperature border of the cold cracking risk is specified for the weldments of some commercial steels.
2
Content available remote Ocena skłonności do pęknięć zimnych złączy spawanych stali w próbie implantacyjnej
Pańcikiewicz K., Zielińska-Lipiec A., Tuz L., Rakoczy Ł.
Przegląd Spawalnictwa
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2016
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R. 88, nr 4
63--65
PL
W artykule przedstawiono próbę implantacyjną oceny skłonności do pęknięć zimnych złączy spawanych. Przedstawiono również wyniki próby dla stali 7CrMoVTiB10-10 oraz badania w zakresie oceny charakteru przełomu.
EN
The paper presents the implant test method as useful for susceptibility to cold cracking evaluation of welded joints. Moreover, there are presented results of implant test for 7CrMoTiVB10-10 steel and fractures analyses with the use of light microscopy and scanning electron microscopy.
3
Content available Analysis of the Causes of Cracks in a Thick-Walled Bush Made of Die-Cast Aluminum Bronze
Pisarek B. P., Kołakowski D., Pacyniak T.
Archives of Foundry Engineering
|
2016
|
Vol. 16, iss. 4
119--124
EN
For the die casting conditions of aluminium bronzes assumed based on the literature data, a thick-walled bush was cast, made of complex aluminium bronze (Cu-Al-Fe-Ni-Cr). After the cast was removed from the mould, cracks were observed inside it. In order to identify the stage in the technological production process at which, potentially, the formation of stresses damaging the continuity of the microstructure created in the cast was possible (hot cracking and/or cold cracking), a computer simulation was performed. The article presents the results of the computer simulation of the process of casting the material into the gravity die as well as solidifying and cooling of the cast in the shape of a thick-walled bush. The simulation was performed with the use of the MAGMA5 program and by application of the CuAl10Ni5,5Fe4,5 alloy from the MAGMA5 program database. The results were compared with the location of the defects identified in the actual cast. As a result of the simulation of the die-casting process of this bush, potential regions were identified where significant principal stresses accumulate, which can cause local hot and cold cracking. Until now, no research has been made of die-cast aluminium bronzes with a Cr addition. Correlating the results of the computer simulation validated by the analysis of the actual cast made it possible to clearly determine the critical regions in the cast exposed to cracking and point to the causes of its occurrence. Proposals of changes in the bush die casting process were elaborated, in order to avoid hot tearing and cold cracking. The article discusses the results of preliminary tests being a prologue to the optimization of the die-casting process parameters of complex aluminium bronze thick-walled bushs.
4
Content available remote Osobliwości przekształceń strukturalnych w strefie wpływu ciepła złączy spawanych MAG stali wysokowytrzymałej WELDOX 1300
Grigorenko G. M., Kostin W.A., Poznjakow W. D., Żdanow S.L., Żukow W.W.
Przegląd Spawalnictwa
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2015
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R. 87, nr 6
42--46
PL
W artykule przedstawiono wyniki badań właściwości struktury w metalu strefy wpływu ciepła stali konstrukcyjnej wysokowytrzymałej typu WELDOX 1300 wykonane metodą MAG. Opracowano wykresy CTPC-s, ustalono i opisano przyczyny obniżenia właściwości mechanicznych połączeń spawanych stali WELDOX 1300.
EN
The article studied the features of the formation of structure in the HAZ metal high-strength structural steel WELDOX 1300, made by MAG welding, built thermokinetic diagram decomposition of austenite (CCT diagram) and installed reason for the decline of the mechanical properties of welded joints in steel WELDOX 1300.
5
Content available remote Skłonność do tworzenia pęknięć zimnych złączy ze stali S420G2+M spawanej pod wodą metodą mokrą
Fydrych D., Rogalski G., Tomków J., Łabanowski J.
Przegląd Spawalnictwa
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2013
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R. 85, nr 10
65--71
PL
Przeniesienie procesu spawania do środowiska wodnego skutkuje przede wszystkim zwiększeniem prędkości stygnięcia złącza oraz wzrostem zawartości wodoru dyfundującego w stopiwie. Środowisko wodne powoduje istotne pogorszenie spawalności stali jednak zastosowanie odpowiedniej technologii spawania pozwala na uzyskanie złączy o właściwościach zbliżonych do wykonywanych na powietrzu. W pracy oceniono przydatność drobnoziarnistej stali po walcowaniu cieplno-mechanicznym na konstrukcje hydrotechniczne wymagające spawania podwodnego. Na podstawie wyników technologicznych prób spawalności stwierdzono, że złącza wykonane z niskowęglowej stali S420G2+M spawane w warunkach mokrych charakteryzują się częściową skłonnością do tworzenia pęknięć zimnych.
EN
The transfer of the welding process into the water environment results primarily in increasing the cooling rate of the weld and growth of diffusible hydrogen content in the deposited metal. The water environment causes significant deterioration of weldability of steel, however, an appropriate welding technology allows for obtaining joints with properties similar to those made in the air. The current study assessed the usefulness of finegrained steel after thermo-mechanical rolling used for hydro- technical structures requiring the underwater welding. Results of weldability technological tests shown that joints of low carbon S420G2+M steel welded under wet conditions are partly sensitive to cold cracking.
6
Skłonność do pęknięć zimnych stali bainitycznej stosowanej w podwyższonych temperaturach
Ziewiec A., Parzych S., Tasak E.
Hutnik, Wiadomości Hutnicze
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2011
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Vol. 78, nr 12
978--981
PL
W artykule przedstawiono wyniki badań skłonności do pękania zimnego stali bainitycznej T24. Wyznaczono naprężenia krytyczne dla strefy wpływu ciepła stali T24 (7CrMoVTiB10-10), które powoduje powstanie pęknięć zimnych. Wartość naprężenia wywołującego pękanie zimne wynosi 485 MPa i jest niższa od granicy plastyczności materiału spoiny.
EN
The paper presents the results of the cold crack sensitivity of the bainitic steel T24. The critical stresses for cold cracks in 7CrMo- VTiB10-10 steel within the heat affected zone were estimated. The value of the critical stresses is 485MPa i.e. lower than the yield stress for the metal in welded joint.
7
Content available remote Microstructural parameter controlling weld metal cold cracking
Seo J. S., Kim H. J., Ryoo H. S.
Journal of Achievements in Materials and Manufacturing Engineering
|
2008
|
Vol. 27, nr 2
199-202
EN
Purpose: Facing with the practical limitation in lowering diffusible hydrogen content, the possible modification of weld microstructure would alleviate the flux cored arc (FACW) weld deposits from the risk of weld metal cold cracking. Therefore, it was aimed to identify and evaluate the effect of weld microstructure on cold cracking susceptibility of FCAW weld metals, and then to give a basic guideline for designing new welding consumables from the microstructural point of view. Design/methodology/approach: In order to figure out the parameter(s) that can quantify the microstructural susceptibility of multi-pass weld deposit, two sets of FCAW deposits having tensile strength of about 600MPa were prepared by controlling the Ni content to allow a sufficient variation in weld microstructure but with little change in weld metal strength. Cold crack susceptibility of those two chemistries was evaluated by' multi-pass weld metal cracking test' at various levels of diffusible hydrogen content. Findings: All of the cold cracks developed were Chevron-type cracks and the occurrence of such cracks was depending on the proportion of grain boundary ferrite as well as the diffusible hydrogen content. In fact, at the same level of diffusible hydrogen, 1.5%Ni wire showed better resistance to cold cracking than the 0%Ni even though that was higher in strength and carbon equivalent. This result could be explained by the difference in grain boundary ferrite content between those two welds based on the microstructural characteristics of Chevron cracking that preferentially propagates along grain boundary ferrite. Research limitations/implications: Detrimental effect of grain boundary ferrite against cold cracking has been addressed for Chevron-type cracks that is commonly developed in the ferritic weld metals having 600MPa strength level so that present result may not be valid for higher strength welds over 700MPa which shows vertical-type cracks. Practical implications: In addition to hydrogen control approach, microstructural modification in a way to reduce the proportion of grain boundary ferrite can be pursued for developing welding consumables with improved resistance to cold cracking. Originality/value: Proportion of grain boundary ferrite was proposed as a parameter that can quantify the microstructural susceptibility of multi-pass weld deposit. This fact can be used for users and manufacturers in selecting and designing welding consumables with better resistance to cold cracking.
8
Content available remote Prace badawcze realizowane w Katedrze Technologii Materiałów Maszynowych i Spawalnictwa Politechniki Gdańskiej
Walczak W.
Przegląd Spawalnictwa
|
2006
|
R. 78, nr 8
3-9
9
Content available remote Technologia spawania w aktualnych normach technicznych (cz.1)
Sędek P.
Konstrukcje Stalowe
|
2006
|
nr 5
40-40
10
Content available remote Pękanie opóźnione w aspekcie mechaniki pękania
Kozak T.
Biuletyn Instytutu Spawalnictwa w Gliwicach
|
2005
|
R. 49, nr 6
58-62
PL
Przedstawiono wyniki badań eksperymentalnych skłonności do pękania zimnego złączy spawanych ręcznie elektrodami otulonymi na okrętowej stali o podwyższonej wytrzymałości gatunku AH36. Badania prowadzono dla złączy o zawartości wodoru dyfundującego w zakresie 0-15,5ml/100gFe. Naprężenia krytyczne z próby implant przeliczono na wartości współczynnika intensywności naprężeń i porównano je z wartościami określonymi doświadczalnie na próbkach cylindrycznych oraz z wartościami określonymi teoretycznie. Uzyskane wyniki stwarzają możliwość przewidywania zachowania się rzeczywistych złączy z punktu widzenia skłonności do pękania zimnego.
EN
It has been presented the results of experiments on susceptibility of covered electrodes manually arc welded joints in higher-strength ship steel of the grade AH36 to cold cracking. The experiments were carried out for the joints in which the diffusible hydrogen content was in the range of 0-15,5 ml/100 g Fe. The critical stresses from the implant test were recalculated to the values of stress intensity factor and compared with the values determined experimentally on cylindrical samples as well as with those determined theoretically. The results obtained in experiments create the possibility to forecast the behaviour of real joints from the view-point of cold crack sensitivity.
11
Wpływ mikrostruktury stali niskostopowych o wysokiej wytrzymałości na ich spawalność
Ćwiek J., Łabanowski J.
Inżynieria Materiałowa
|
2003
|
R. XXIV, nr 6
709-711
PL
Mikrostruktura stali niskostopowych o wysokiej wytrzymałości wpływa na skłonność do pęknięć zimnych ponieważ ma wpływ na hartowność i twardość maksymalną strefy wpływu ciepła (SWC). Dwa gatunki stali o wysokiej wytrzymałości 18G2AV i 14HNMBCu, w różnych stanach obróbki cieplnej, zostały poddane symulowanym cyklom cieplnym spawania. Maksymalna twardość SWC zależna jest od rodzaju mikrostruktury przed cyklem cieplnym spawania. Najwyższą twardość w SWC obserwowano dla stanu ulepszonego cieplnie w porównaniu ze stanem wyżarzonym zupełnie i przegrzewająco.
EN
Microstructure of steel before welding has influence on the steel's susceptibility to cold cracking because it influences hardenability and maximum hardness of heat affected zone (HAZ). Two high-strength low-alloy (HSLA) steel grades 18G2AV and 14HNMBCu, in various heat treatment conditions, were subjected to simulated welding thermal cycles. It has revealed that maximum HAZ hardness is influenced by microstructure presented before thermal cycle was applied. The higher HAZ hardness was observed for quenched and tempered condition, comparing to full annealed and overheated conditions.
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