Analysis of the HAZ fracture resistance of HSLA steel weldments

Ispitivane su karakteristike otpornosti ka lomu u ZUT zavarenog spoja mikrolegiranog čelika povećane čvrstoće koji se koristi za izradu posuda pod pritiskom. S obzirom na namenu zavareni spoj treba da ima veliku otpornost ka pojavi i rastu prslina. Analiza je obuhvatila udarnu žilavost uzoraka simuliranih mikrostruktura koje su tipične za ZUT, žilavost loma nestandardnih uzoraka sa simuliranim mikrostrukturama i konačno standardne zavarene SENB uzorke. Analiza je pokazala da tip prsline (erozimatna i zamorna) na početak stabilnog rasta prsline ima veći uticaj kod duktilnijih mikrostruktura, a manji ili skoro nikakav kod krtijih. Takođe, komparativna analiza simuliranih uzoraka i zavarenih uzoraka pokazala je uticaj odnosa i veličine mikrostrukturnih regiona u ZUT-u na rast prsline t.j. uticaj mismeča na otpornost ka lomu.The HAZ fracture behavior of the weldments of HSLA steel for pressure vessels has been investigated. Having in mind the purpose of such structure, the welded joint should poses sufficient resistance towards crack occurrence as well its propagation. The analysis encompassed impact toughness testing of Charpy specimens and fracture toughness determination of SENB specimens of base metal and simulated microstructures of HAZ, and finally fracture toughness testing of welded specimens with crack located in the very narrow HAZ regions. The analysis revealed the effect of the crack tip (electro eroded or fatigued) on the onset of the stabile crack growth for the different microstructures. The comparative analysis between the testings showed the influence of the mismatch towards the fracture behavior of real welded joint in respect of simulated microstructures

Integrity assessment of spherical storage tank

Analiziran je integritet sfernih rezervoara za amonijak (zapremine 1000 m3, prečnika 12400 mm, debljina zida 30 mm), zato što su otkrivene prsline na liniji stapanja, dužine do 300 mm, različite dubine. Direktnim merenjem J integrala određene su J-R krive za dva položaja vrha prsline (finozrni i grubozrni ZUT). Ove krive su upoređene sa silama rasta prsline, dobijenim analitički, da bi se procenila kritična vrednost pritiska.Integrity of spherical storage tanks for ammonia (volume 1000 m3, diameter 12400 mm, wall thickness 30 mm) has been analysed because cracks have been found along fusion line, of length up to 300 mm and variable depth. By J integral direct measurement J-R curves have been obtained for two positions of crack (fine grain and coarse grain HAZ). These curves are plotted against crack driving forces, analytically obtained, for the estimation of critical pressure

Integrity assessment of spherical storage tank

Analiziran je integritet sfernih rezervoara za amonijak (zapremine 1000 m3, prečnika 12400 mm, debljina zida 30 mm), zato što su otkrivene prsline na liniji stapanja, dužine do 300 mm, različite dubine. Direktnim merenjem J integrala određene su J-R krive za dva položaja vrha prsline (finozrni i grubozrni ZUT). Ove krive su upoređene sa silama rasta prsline, dobijenim analitički, da bi se procenila kritična vrednost pritiska.Integrity of spherical storage tanks for ammonia (volume 1000 m3, diameter 12400 mm, wall thickness 30 mm) has been analysed because cracks have been found along fusion line, of length up to 300 mm and variable depth. By J integral direct measurement J-R curves have been obtained for two positions of crack (fine grain and coarse grain HAZ). These curves are plotted against crack driving forces, analytically obtained, for the estimation of critical pressure

Limit load solution for mismatched welded plate and pressure vessel with a surface crack

Na ponašanje strukture pri lomu, koja ima prslinu na sredini vara, utiču mehaničke osobine sastavnih delova zavarenog spoja (metal šava, osnovni materijal, zona uticaja toplote) i njihova geometrija. Zbog toga su razvijeni postupci procene oštećenja koji treba da uzmu u obzir sve te uticajne parametre. Jedna od ključnih stvari u ovom postupku je da se dobiju rešenja graničnih opterećenja nesrodne strukture. Ova rešenja su dobijena korišćenjem 3D-rešenja metodom konačnih elemenata za različite konfiguracije kao što su: zategnuta ploča sa površinskom prslinom ili posuda pod pritiskom sa spoljnom osnom površinskom prslinom izložena unutrašnjem pritisku, poˇsto su ova granična opterećenja dobijena materijalnim eksponentom za slučaj bez ojačanja.Fracture behavior of a structure having a crack in the middle of a weld is influenced by the mechanical properties of the welded joint constituents (weld metal, base metal, heat-affected-zone) and their geometry. Therefore, defect assessment procedures have been developed in order to take into account all those affecting parameters. One of the key point for all those defect assessment procedures is to have limit load solutions of the mismatch structure. Such limit load solutions have been obtained by using 3D finite element solutions for different configurations such as plate with surface crack in tension or pressure vessel with axial external surface crack exposed to internal pressure, since those limit load have been obtained for non-hardening material exponent

Residual strength assessment of cracked welded spherical storage tank

Dva sferna rezervoara za amonijak (zapremine 1000 m3) su ispitana 1998. i 1999. tehnikama bez razaranja (NDT) u skladu sa Propisima za periodičnu kontrolu. Ovi rezervoari su izrađeni 1979. od čelika StE 460 prema DIN, mikrolegiranog Cr-Ni-Ti, debljine 30 mm. Uočen je veliki broj poprečnih prslina u metalu šava i uzdužnih prslina u zoni-uticaja-toplote (ZUT) i po liniji stapanja unutrašnjih zavarenih spojeva. Da bi se procenila zaostala čvrstoća oba rezervoara, ploče 500 x 500 mm, su isečene radi hemijskog, metalurškog i mehaničkog ispitivanja. Ova ispitivanja su obuhvatala detaljno određivanje žilavosti standardnih Šarpi epruveta na instrumentiranom klatnu i ispitivanja mehanike loma na standardnim SEN(B) epruvetama za ocenu žilavosti loma. Na osnovu rezultata Šarpi ispitivanja i ispitivanja mehanike loma ocenjena je preostala čvrstoća sfernih rezervoara sa prslinama.Two spherical storage tanks for ammonia (volume 1000 m3) have been tested in 1998 and 1999 by Non-Destructive Techniques (NDT) in accordance with the Periodic Inspection Regulations. These storage tanks have been constructed in 1979 of St.E460 steel according DIN, Cr-Ni-Ti microalloyed, 30 mm thick. The large number of transverse cracks in weld metal and longitudinal cracks in heat-affected-zone (HAZ) and along fusion line of inner welded joints have been detected. In order to assess the residual strength, of both storage tanks, plates 500 x 500 mm were cut for chemical, metallurgical and mechanical testing. These testing included detailed toughness testing of standard Charpy specimens on instrumented pendulum, and fracture mechanics testing on standard SEN(B) specimens for fracture toughness evaluation. Based on results of Charpy and fracture mechanics testing residual strength of cracked storage tanks has been assessed

Residual strength assessment of cracked welded spherical storage tank

Dva sferna rezervoara za amonijak (zapremine 1000 m3) su ispitana 1998. i 1999. tehnikama bez razaranja (NDT) u skladu sa Propisima za periodičnu kontrolu. Ovi rezervoari su izrađeni 1979. od čelika StE 460 prema DIN, mikrolegiranog Cr-Ni-Ti, debljine 30 mm. Uočen je veliki broj poprečnih prslina u metalu šava i uzdužnih prslina u zoni-uticaja-toplote (ZUT) i po liniji stapanja unutrašnjih zavarenih spojeva. Da bi se procenila zaostala čvrstoća oba rezervoara, ploče 500 x 500 mm, su isečene radi hemijskog, metalurškog i mehaničkog ispitivanja. Ova ispitivanja su obuhvatala detaljno određivanje žilavosti standardnih Šarpi epruveta na instrumentiranom klatnu i ispitivanja mehanike loma na standardnim SEN(B) epruvetama za ocenu žilavosti loma. Na osnovu rezultata Šarpi ispitivanja i ispitivanja mehanike loma ocenjena je preostala čvrstoća sfernih rezervoara sa prslinama.Two spherical storage tanks for ammonia (volume 1000 m3) have been tested in 1998 and 1999 by Non-Destructive Techniques (NDT) in accordance with the Periodic Inspection Regulations. These storage tanks have been constructed in 1979 of St.E460 steel according DIN, Cr-Ni-Ti microalloyed, 30 mm thick. The large number of transverse cracks in weld metal and longitudinal cracks in heat-affected-zone (HAZ) and along fusion line of inner welded joints have been detected. In order to assess the residual strength, of both storage tanks, plates 500 x 500 mm were cut for chemical, metallurgical and mechanical testing. These testing included detailed toughness testing of standard Charpy specimens on instrumented pendulum, and fracture mechanics testing on standard SEN(B) specimens for fracture toughness evaluation. Based on results of Charpy and fracture mechanics testing residual strength of cracked storage tanks has been assessed

Limit load solution for mismatched welded plate and pressure vessel with a surface crack

Na ponašanje strukture pri lomu, koja ima prslinu na sredini vara, utiču mehaničke osobine sastavnih delova zavarenog spoja (metal šava, osnovni materijal, zona uticaja toplote) i njihova geometrija. Zbog toga su razvijeni postupci procene oštećenja koji treba da uzmu u obzir sve te uticajne parametre. Jedna od ključnih stvari u ovom postupku je da se dobiju rešenja graničnih opterećenja nesrodne strukture. Ova rešenja su dobijena korišćenjem 3D-rešenja metodom konačnih elemenata za različite konfiguracije kao što su: zategnuta ploča sa površinskom prslinom ili posuda pod pritiskom sa spoljnom osnom površinskom prslinom izložena unutrašnjem pritisku, poˇsto su ova granična opterećenja dobijena materijalnim eksponentom za slučaj bez ojačanja.Fracture behavior of a structure having a crack in the middle of a weld is influenced by the mechanical properties of the welded joint constituents (weld metal, base metal, heat-affected-zone) and their geometry. Therefore, defect assessment procedures have been developed in order to take into account all those affecting parameters. One of the key point for all those defect assessment procedures is to have limit load solutions of the mismatch structure. Such limit load solutions have been obtained by using 3D finite element solutions for different configurations such as plate with surface crack in tension or pressure vessel with axial external surface crack exposed to internal pressure, since those limit load have been obtained for non-hardening material exponent

Crack type effect on fracture toughness of HAZ microalloyed steels

Izvršeno je eksperimentalno ispitivanje lomne žilavosti malih nesimuliranih i simuliranih SENB epruveta mehanike loma sa erozimatnom i zamornom prslinom. Uspostavljena je neophodna korelacija za korekciju rezultata ispitivanja realnog zavarenog spoja sa erozimatnom prslinom u ZUT [1]. Osnovni materijal je mikrolegirani finozrni čelik povišene čvrstoće, kvaliteta T StE 420 prema DIN 17102, sa titanom kao legirajućim elementom. Uzorci osnovnog materijala i uzorci sa simuliranim mikrostrukturama ZUT i to: jednoprolazni sa termičkim ciklusom od 1350°C, i dvoprolazni sa drugim ciklusom od 780 i 960°C, ispitani su na +20°C.Fracture toughness test of SENB specimens with eroded and fatigue precracked cracks has been performed. Correlation factor between fatigue precracked and eroded crack is introduced for correction of the results of test performed on real welded joint with eroded crack in the HAZ [1]. Four materials are investigated, base metal, is highstrength microalloyed fine-grained steel, class T StE 420, with titanium as basic alloy element, as well as three simulated HAZ's microstructures: single cyclic at 1350°C, and double cyclic at 780 and 960°C, tested on +20°C

Crack type effect on fracture toughness of HAZ microalloyed steels

Izvršeno je eksperimentalno ispitivanje lomne žilavosti malih nesimuliranih i simuliranih SENB epruveta mehanike loma sa erozimatnom i zamornom prslinom. Uspostavljena je neophodna korelacija za korekciju rezultata ispitivanja realnog zavarenog spoja sa erozimatnom prslinom u ZUT [1]. Osnovni materijal je mikrolegirani finozrni čelik povišene čvrstoće, kvaliteta T StE 420 prema DIN 17102, sa titanom kao legirajućim elementom. Uzorci osnovnog materijala i uzorci sa simuliranim mikrostrukturama ZUT i to: jednoprolazni sa termičkim ciklusom od 1350°C, i dvoprolazni sa drugim ciklusom od 780 i 960°C, ispitani su na +20°C.Fracture toughness test of SENB specimens with eroded and fatigue precracked cracks has been performed. Correlation factor between fatigue precracked and eroded crack is introduced for correction of the results of test performed on real welded joint with eroded crack in the HAZ [1]. Four materials are investigated, base metal, is highstrength microalloyed fine-grained steel, class T StE 420, with titanium as basic alloy element, as well as three simulated HAZ's microstructures: single cyclic at 1350°C, and double cyclic at 780 and 960°C, tested on +20°C

Welding thermal cycles influence on microalloied steel HAZ toughness

Izvršeno je instrumentirano ispitivanje udarne žilavosti standardnih Šarpijevih epruveta, pri čemu je ukupna energija loma razdvojena na komponente za inicijaciju i rast prsline. Materijal je finozrni čelik povišene čvrstoće, klase T StE 420 (DIN 17102), mikrolegiran sa titanom, od kojeg su izraðene dve sferene posude pod pritiskom, zavarene E postupkom. Uzorci od osnovnog materijala ispitivani su na -40, -20 i +20 °C, a uzorci simuliranih mikrostruktura ZUT na -20 i +20 °C. Simulacija zavarivanja je bila sa termičkim ciklusom: za jednociklusni od 1350 °C, za dvociklusne od 600, 700, 780, 880, 960, 1100 i 1350 ° C.Impact test on instrumented Charpy pendulum has been performed and dividing of tehe total fracture energy into it 's two components, for initiation and propagation of the crack, has been determined. The base metal is highstrength microalloyed fine-grained steel, class T StE 420 (DIN 17102), with titanium as basic alloy element, of which two welded spherical pressure vessels are produced. Specimens of base metal are investigated on -40, -20 i +20°C, as well as specimens with simulated HAZ 's microstructure on -20 i +20°C. Welding simulations are the following: single cyclic on 1350°C, and double cyclic on 600, 700, 780, 880, 960, 1100 i 1350°C