Wyniki wyszukiwania - BazTech

1

Characterization of galvanized steel-low alloy steel arc stud welded joint

Abbas S. J., Alali M., Abbas M. H., Abbas W. S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2023

|

Vol. 117, nr 2

79--85

EN

Purpose This paper investigates the possibility of successfully welding a Low Alloy Steel (LAS) stud to Galvanized Steel (GS) plate. Design/methodology/approach Arc Stud Welding (ASW) was performed on joining LAS studs to GS plates. Welding parameters were selected based on weld trails. The first tests of the welded joints were based on visual inspection for welding defects such as lack of fusion and undercut welding defects. The good quality should be free of these defects and have full weld reinforcement. Other weld qualifications included torque strength test, microhardness test, and microstructure examination. Findings The LAS studs have been successfully welded to a galvanized steel plate using the arc stud welding process. Higher welding current with adjusted welding time (800 A, 0.3 s) gave full weld reinforcement, the best joint appearance, and strength. Martensite phase was detected in the weld area and heat affected zone (HAZ), affecting the joint mechanical properties. Hardness property varied across the welded joint, and maximum hardness was recorded at the HAZ at the stud side. Hardness increased with the increasing welding current. At 800 A, welding current hardness was 10% higher than at 400 and 600 A. Torque strength was affected by weld reinforcement, and 800 A gave the best weld reinforcement that produced the highest torque strength. Research limitations/implications The main research limitation is the difficulty of welding LAS studs and GS plates. In conventional welding methods, such as gas metal arc welding, it is hard to get full weld penetration due to the geometry restrictions of the joint, which results in partial weld penetration between the studs and the plates. Furthermore, the issue of zinc evaporation during welding can be reduced by the advantage of the very high welding speed (in milliseconds) of ASW that overcomes the problem of continuous welding that usually results in the formation of harmful porosities and poor weldability. Originality/value In this research, galvanized steel plates were successfully welded to LAS studs using the ASW process. The welding parameters for this dissimilar welding joint were carefully selected. Microstructure changing due to the welding process was investigated. The joint mechanical properties were evaluated.

2

Microstructure and Mechanical Properties of AISI 1106 /AISI 1045 Steels Drawn Arc Stud Welded Joints

Algodi Samer Jasim, Salman Abdulhakeem Amer, Al-helli Ali H.

Advances in Science and Technology. Research Journal

|

2023

|

Vol. 17, no 5

48--55

EN

Arc stud welding process was used to join a fully threaded low carbon steel AISI 1106 stud to medium carbon steel AISI 1045 plate, the effects of welding current 200, 400 A and the welding time 0.1 to 0.6 step 0.1 s on the microstructure and mechanical properties were investigated, additional parameters of adding 0.1, 1 g SiC powder and applying nano carbon layer to the welding area also included. The results demonstrate that the preferred stud welding process parameters for this system was 400 A with 0.4 s welding current and time, respectively, which has a maximum tensile strength of 583 MPa. The joints fabricated with ash and nano carbon coated at preferred welding parameters showed a slight reduction in tensile strength. The fracture of the tensile test specimen consists of three failure modes including of interface fracture between stud and plate surface due to incomplete melting at low processing parameter, pullout fracture which is featured by a hole in the plate surface and fracture at the stud shank instead of the weldment interface or heat affected zone. The microstructure of the stud and plate are characterized by equiaxed grain of ferrite and pearlite with small amount of ferrite, respectively. The fusion zone consists of fine grain of ferrite and perlite. The hardness of the fusion zone was recording 132 HV which it slightly higher than the stud hardness 128 HV and lower than that of plate of 164 HV.

3

Investigation of Microstructures and Mechanical Properties of T92 Martensitic Steel/Super304 Austenitic Steel Weld Joints Made with Three Welding Consumables

Liang Z., Gui Y., Zhao Q.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 3

1249--1256

EN

The microstructures and mechanical properties of T92 martensitic steel/Super304 austenitic steel weld joints with three welding consumables were investigated. Three types of welding materials ERNiCr-3, ERNiCrCoMo-1and T-304H were utilized to obtain dissimilar welds by using gas tungsten arc weld (GTAW). The results show that heat affect zone (HAZ) of T92 steel consists of coarse-grained and fine-grained tempered martensites. The microstructures of joints produced from ERNiCrCoMo-1 consist of equiaxed dendrite and columnar dendrite grains, which are more complicated than that of ERNiCr-3. In the tensile tests, joints constructed from ERNiCrCoMo-1 and T-304H met the ASME standard. The highest fracture energy was observed in specimens with the welding material ERNiCrCoMo-1. Ni content in weld seam of ERNiCrCoMo-1 was highest, which was above 40%. In conclusion, the nickel alloy ERNiCrCoMo-1 was the most suitable welding material for joints produced from T92 martensitic steel/Super304 austenitic steel.

4

A computational fluid dynamics analysis of transport enforced by Marangoni effect during laser welding

Siwek A.

Computer Methods in Materials Science

|

2017

|

Vol. 17, No. 4

186--194

EN

The presence of surface active elements such as sulfur in steel, changes the surface tension on the weld pool surface. The Marangoni effect induced by temperature dependent surface tension gradient, determines the direction of fluid flow in the entire volume of the weld pool. The difference of initial sulfur concentration of the welded parts is an additional factor which complicates the model. During welding an additional body force source term has been added to the momentum equations at the liquid steel surface, depending on sulfur concentration gradient. Mutual mixing of welded steels in the weld pool leads to periodic changes of driving force direction. The model permits the calculation of sulfur concentration in the weld pool and weld size depending on the initial composition, laser power and welding velocity.

PL

Wpływ zawartości siarki na proces spawania opisany został w wielu pracach. Siarka jako jeden z pierwiastków powierzchniowo aktywnych wpływa na napięcie powierzchniowe stali. W większości publikacji dotyczących modelowania procesu spawania, zawartość siarki była taka sama w obydwu spawanych elementach. Artykuł dotyczy przypadku, gdy spawane stalowe elementy różnią się zawartością siarki. Mieszanie się spawanych stali w jeziorku spawalniczym prowadzi do okresowych zmian kierunku działania siły wymuszającej przepływ. Model pozwala na obliczenie rozkładu zawartości siarki w spoinie oraz wielkości spoiny w zależności od danych termofizycznych stali, początkowej zawartości siarki, mocy wiązki lasera i prędkości spawania.

5

Modelling of laser welding for materials with different properties

Siwek A.

Computer Methods in Materials Science

|

2015

|

Vol. 15, No.4

441--446

EN

Joining metals and alloys with different properties gives greater flexibility in design and production as compared to manufacturing with one type of material only. Thanks to this, expensive materials can be applied only at places where their use is indispensable. However, joining different combinations of metals become a challenge, due to the differences in physical and chemical properties. Laser welding, thanks to such advantages as good weldability and high quality of joints with narrow heat affected zone, allows for solving many problems appearing in traditional joining methods. The current paper concerns modelling of laser welding processes for materials with different physical and chemical properties. The model consists of a coupled set of incompressible fluid flow equations, heat equation and convection-diffusion equations for different material species. The formulation takes into account the dependence of material properties on temperature and chemical composition. Discontinuity of density and viscosity, together with the chemical composition of fluid in weld pool influences the velocity and temperature distribution in the weld pool and in consequence determines the shape and properties of a joint.

PL

Artykuł dotyczy modelowania spawania laserowego materiałów o różnych własnościach. Dominującą siłą wymuszającą ruch cieczy w takich układach jest gradient napięcia powierzchniowego oraz siła odrzutu powstała na powierzchni jeziorka spawalniczego. W literaturze można znaleźć wiele artykułów w których wykorzystano różne metody śledzenia powierzchni międzyfazowej, np. Level Set method (LS), Volume of Fluid method (VOF), lub bardziej skomplikowanej Coupled Level Set and Volume of Fluid method (CLSVOF). W wielu publikacjach wykorzystywana jest metoda VOF. Metoda ta jest wydajna, ponieważ nie wymaga iteracyjnego rozwiązywania dodatkowych równań i spełnia zasadę zachowania masy. Niestety metoda ta nie pozwala na wyznaczenie dokładnego położenia powierzchni międzyfazowej. Granica międzyfazowa jest rekonstruowana w każdej iteracji za pomocą pola udziału fazy, dyskretyzowanego na siatce eulerowskiej. Wartość tego pola wskazuje jaka faza znajduje się w danej komórce siatki. Granica międzyfazowa przemieszcza się przez adwekcję pola fazowego. Przyczyną trudności może być wymaganie dużej dokładności wyznaczenia położenia granicy w każdej iteracji rozwiązania. To z kolei powoduje nieciągłość własności takich jak gęstość i lepkość na granicy międzyfazowej, a przez to niestabilność numeryczną rozwiązania. Metoda VOF spełnia warunek zachowania masy. Pochodne pola udziału fazy VOF nie są jednak ciągłe w okolicy granicy międzyfazowej. Dlatego obliczone z funkcji fazy VOF krzywizna granicy i wektor normalny do granicy są niedokładne. Powoduje to tworzenie się w obszarze granicznym pozornych przepływów w wyniku niezrównoważenia siły napięcia powierzchniowego. Artykuł dotyczy wykorzystania powyższych metod do modelowania spawania laserowego materiałów o różnych własnościach fizycznych. Spawanie takich materiałów jest trudne, ze względu na tworzenie się asymetrii w przepływach ciepła i masy oraz zauważalną segregację pierwiastków powierzchniowo aktywnych. Tworząca się mikrostruktura zespawanych elementów przez to także jest asymetryczna względem płaszczyzny spawania. Modelowanie takich przepływów pozwoli na zrozumienie procesów zachodzących w jeziorku spawalniczym.