The high-strength low-alloy S460ML and S460N steels were chosen for underwater wet welding of dissimilar T-joints using covered electrodes For improving the quality of joints, the temper bead welding (TBW) method was used The application of TBW in pad welding conditions has been investigated earlier but the possibility of usage of this technique in welded joints was not analyzed The main aim of the study was to check the influence of TBW on the hardness and structures of the heat-affected zone (HAZ) of dissimilar T-joints made in the underwater conditions The experiments conducted showed that the technique used can reduce the susceptibility to cold cracking by decreasing the hardness in HAZ, which is a result of changes in its structure The TBW technique reduced the hardness in the HAZ of the S460N steel by 40–50 HV10 and in S460ML by 80–100 HV10 It was also found that the changes in S460ML and S460N were much different, and therefore, the investigated technique can provide better results in the steel characterized by lower carbon equivalent CeIIW

/pdf/dissimilar-underwater-wet-welding-of-hsla-steels-4uiljn4kxz.pdf

Dissimilar underwater wet welding of HSLA steels

In this paper the influence of in situ local heat treatment performed by additional stitches on the weldability of high-strength low-alloy (HSLA) S355J2C+N steel was tested. The investigated steel is characterized by high susceptibility to cold cracking. It is necessary to find a method to improve the quality of welded joints. The local heat treatment was applied as an effect of bead-on plate welding made on the face of a Tekken test joint. The specimens were made by the use of covered electrodes in the water environment. For testing weldability, Tekken test specimens were made. Then, the different number of the pad welds with different overlapping were laid on the face of the tested welds. Non-destructive (NDT) visual and penetrant tests were undertaken. During the NDT, imperfections like shape mistakes and spatters were found. Then, metallographic macro- and microscopic testing were performed. The macroscopic observations proved that water environment can generate imperfections like cracking and pores. However, for specimens with additional stitches the number of imperfections decreased. Microscopic tests proved that the proposed technique affected the structure of the heat-affected zone (HAZ). The specimens without the application of additional stitches are characterized by brittle bainitic and martensitic structure. Specimens, in which the additional stitches were applied, contain tempered martensite, fine ferrite and fine pearlite in their HAZ. It was also observed that the number of cracks decreased for in situ local heat-treatment specimens. The final step was Vickers HV10 hardness measurement. These measurements confirmed previous results. The heat from additional stitches affected the steel by significantly decreasing the hardness by 80–100 HV10. The results of experiments showed that the heat from pad welds provided microstructural changes in heat-affected zones and a decrease in the susceptibility to cold cracking, which results in improvement in the weldability of HSLA steel in wet welding conditions.

/pdf/underwater-in-situ-local-heat-treatment-by-additional-4my8i9kwl9.pdf

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

The paper describes the microstructure of welded joints produced by the plasma+MAG (Metal Active Gas) method of S700MC high yield strength steel (700 MPa). Welded joints of thermomechanical steel have been made with different values of heat input. The results of metallographic research of welded joints, microstructure of the weld and heat affected zone, hardness distribution and impact toughness are presented. The heat affected zone consists of two sub-zones with different grain size and lowered hardness. The tensile test show that strength of welded joints was slightly reduced and the bending test revealed no crack formation in the weld. The impact toughness of measured welded samples with V-notch in HAZ (heat affected zone) reached high values that are higher comparing to samples with notch placed in the weld area. The investigation results show that the use of plasma concentrated heat source together with MAG welding arc does not significantly change the structure and deteriorate properties of welded S700MC thermomechanically treated high strength steel. The hybrid plasma+MAG welding method has a potential to become a beneficial alternative to other welding processes due to its high efficiency, reduced amount of weld metal content or limited requirements for a preparation of edges of welded joints.

/pdf/weldability-of-s700mc-steel-welded-with-the-hybrid-plasma-3sp5tt82pi.pdf

Weldability of S700MC steel welded with the hybrid plasma + MAG method

The article presents the results of research on the influence of temperature and time changes of the annealing process on the values and distribution of stresses in the simulated heat-affected zone of S700MC steel welded joints. For this purpose, tests were carried out on a thermal cycle simulator, as well as heating the prepared samples in accordance with the recorded welding thermal cycles, and then annealing at temperatures from 200 to 550 °C. The stresses values in the tested samples before and after the annealing process were measured by using X-ray diffraction (XRD). The performed tests were verified with the results of numerical analyses using the finite element method (FEM) performed in the VisualWeld (SYSWELD) environment as, on the one hand, the verification of the obtained results, and, on the other hand, the source of data for the development of a methodology for conducting analyses of heat treatment processes of S700MC steel welded structures. Also presented are three examples of numerical analyses for Gas Metal Arc (GMAW), laser and hybrid welding and then the annealing process of the obtained joints at selected temperatures. The main purpose of the work was to broaden the knowledge on the influence of annealing parameters on the values and distribution of stresses in welded joints, but also to signal the possibility of using modern software in engineering practice.

Experiments and Numerical Simulations of the Annealing Temperature Influence on the Residual Stresses Level in S700MC Steel Welded Elements

The paper presents the effects of waterproof coatings use to cover electrodes on the weldability of high-strength, low-alloy (HSLA) steel in water. With the aim of improving the weldability of S460N HSLA steel in water, modifications of welding filler material were chosen. The surfaces of electrodes were covered by different hydrophobic substances. The aim of the controlled thermal severity (CTS) test was to check the influence of these substances on the HSLA steel weldability in the wet welding conditions. The visual test, metallographic tests, and hardness Vickers HV10 measurements were performed during investigations. The results proved that hydrophobic coatings can reduce the hardness of welded joints in the heat-affected zone by 40–50 HV10. Additionally, the number of cold cracks can be significantly reduced by application of waterproof coatings on the filler material. The obtained results showed that electrode hydrophobic coatings can be used to improve the weldability of HSLA steel in underwater conditions.

https://www.mdpi.com/1996-1944/14/6/1364/pdf

Weldability of Underwater Wet-Welded HSLA Steel: Effects of Electrode Hydrophobic Coatings.

/pdf/wybrane-wlasciwosci-zlaczy-spawanych-stali-s700-mc-36zkgxzdk9.pdf

Wybrane właściwości złączy spawanych stali S700 MC wykonanych metodą hybrydową plazma+MAG

The paper describes the selected properties of RAMOR 500 anti-ballistic (martensitic structure in the initial state) high yield strength steel (1450 MPa) welded joints produced by the hybrid PTA-MAG (Plasma Transferred Arc - Metal Active Gas) method. The welded elements were metal sheets 6.7 mm thick in a rectangular shape with dimensions of 200 mm x 350 mm. The tested butt weld joints have been made with process parameters selected according to criterion of lowest level of material weakening in the heat-affected zone (HAZ). The results of metallographic research of welds heat affected zone and base material, hardness distribution and XRD patterns of specific areas have been presented. Depth-sensing indentation (DSI) is used in this work to determine the distribution of mechanical properties affected by annealing/tempering by thermal cycle of hybrid PTA-MAG welding process. The investigation results show that the use of hybrid PTA-MAG heat source for welding of martensitic structure steel makes it possible to use high strength steel filler material (yield strength 890 MPa) without of cold cracks high risk. The hybrid plasma based welding method has a potential to become a beneficial alternative to other welding processes for ballistic protection steel due to its high efficiency, reduced amount of weld metal content or limited requirements for a preparation of edges of welded joints. The weakest area of welded joints is part of HAZ located close to the base material which has been secondarily tempered by heat of welding thermal cycle. The heat input about 0,57 kJ/mm required to achieve full penetration butt welded joints with no defects and with wide enough capillary channel to cover the welding gap during welding process. Hardness decrease in that area is about 25% in relation of base material. The width of the softened zone was approx. 4.5 mm. 

Selected Properties of RAMOR 500 Steel Welded Joints by Hybrid PTA-MAG

W artykule opisano zrobotyzowane stanowisko hybrydowe Plazma+MAG. Przedstawiono wstepne wyniki badan zlączy spawanych stali obrabianej termomechanicznie o wysokiej granicy plastyczności S700 MC o grubości 10 mm z materialem dodatkowym. Przeprowadzono badania nieniszczące zlączy świadczące o poziomie jakośc zlącza B wg ISO 12932. Wykonano badania metalograficzne, opisano mikrostrukture zlączy oraz scharakteryzowano twardośc w charakterystycznych obszarach zlączy. Zmierzono twardośc w strefie wplywu ciepla zlączy wykonanych z rozną energią liniową spawania.  Robotic hybrid Plasma+MAG welding of S700 MC steel  Abstract The article presents the robotic hybrid Plasma+MAG welding system. The Single pass butt weld 10 mm thickness joints of steel S700 MC with filler material has been welded. Preliminary results of joints properties has been presented. Mettalographic studies were describe microstructure of the welded joints and its hardness in specific areas. It was measured hardness in the heat af- fected zone of the joints obtained of different heat input welding.

/pdf/zrobotyzowane-spawanie-hybrydowe-plazma-mag-stali-s700-mc-pgkuy93tlf.pdf

Zrobotyzowane spawanie hybrydowe Plazma+MAG stali S700 MC

W artykule scharakteryzowano innowacyjną metode spawania hybrydowego bedącą ekonomiczną alternatywą dla spawania hybrydowego Laser-MAG. W glownej cześci artykulu zaprezentowano wstepne wyniki badan metalograficznych spoin czolowych wykonywanych metodą wysokowydajnego spawania hybrydowego Plazma-MAG. Spawano stal niestopową S235JR. Omowiono budowe wykonanych nowatorską techniką zlączy spawanych oraz przeprowadzono badania metalograficzne zlączy, analizując budowe mikrostruktury oraz rozklady twardości w charakterystycznych obszarach spoiny. Przedstawiono korzyści techniczne i ekonomiczne wynikające z zastosowania opisanego rozwiązania. Abstract This paper describes an innovative method for hybrid welding being economical alternative to Laser-MAG hybrid welding. In the main part of the article the preliminary results of metallographic testing of the welds (low alloy steel) have been presented. Metallographic studies of the joints were carried out, discussed the microstructure and hardness distributions in characteristic areas of the weld.

/pdf/badania-metalograficzne-spoin-wykonanych-hybrydowa-metoda-2s0lytscbr.pdf

Jacek Szulc

Papers

Weldability of S700MC steel welded with the hybrid plasma + MAG method

Wybrane właściwości złączy spawanych stali S700 MC wykonanych metodą hybrydową plazma+MAG

Selected Properties of RAMOR 500 Steel Welded Joints by Hybrid PTA-MAG

Zrobotyzowane spawanie hybrydowe Plazma+MAG stali S700 MC

Badania metalograficzne spoin wykonanych hybrydową metodą PTA-MAG; Metallographic examination of welded joints produced by PTA-MAG hybrid process