Wyniki wyszukiwania - BazTech

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Investigation of process stability and weld quality of underwater wet flux-cored arc welding of low-alloy high-strength steel with oxy-rutile wire

Li Hongliang, Liu Shixiong, Ma Qiang, Wang Pengfei, Liu Duo, Zhu Qiang

Polish Maritime Research

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2021

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nr 3

100--109

EN

The paper described the experimental findings of underwater wet welding of E40 steel using self-shielded flux-cored wire with a TiO2 -FeO-MnO slag system. The arc stability, weld quality and corrosion resistance with different heat inputs were studied. The results showed that the wet welding process of the designed wire displayed good operability in the range of investigated parameters. The microstructure and mechanical properties of the weld metal depended on the heat input. Due to the high fraction of acicular ferrite in the weld metal, the mechanical properties of the weld metal under low heat input had better tensile strength and impact toughness. Fracture morphologies at low heat input had uniform and small dimples, which exhibited a ductile characteristic. The diffusible hydrogen content in the deposited metal obtained at a heat input of 26 kJ/cm significantly reduced to 14.6 ml/100g due to the combined effects of Fe2 O3 addition and the slow solidification rate of molten metal. The microstructure also had a significant effect on the corrosion resistance of the weld metal. The weld metal with high proportions of acicular ferrite at low heat input exhibited the lowest corrosion rate, while the base metal possessed a reduced corrosion resistance. These results were helpful to promote the application of low alloy high strength steel in the marine fields.

2

Bead-on-Plate Underwater Wet Welding on S700MC Steel

Tomków Jacek, Świerczyńska Aleksandra, Landowski Michał, Wolski Adrian, Rogalski Grzegorz

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 3

288-296

EN

The participation of high strength steels in marine and offshore structures is increasing, which makes it necessary to develop recommendations for underwater repair welding works. The article presents the results of bead-on-plate welded specimens made of S700MC high strength steel in underwater wet welding conditions by covered electrodes. Three specimens with heat input values in the range 0.91-1.05 kJ/mm were made. The specimens were subjected to visual, metallographic, macro- and microscopic tests as well as hardness measurements using the Vickers method. It was found that the higher heat input leads to formation of mixed bainite-martensite microstructure in the heat-affected zone (HAZ). Lower heat input value results in presence of martensite in HAZ. It was shown that in the scope of the performed tests, the maximum hardness of HAZ did not exceed the critical value for the material group, and the increase in heat input caused the decrease of hardness by about 25 HV10.

3

Cold Cracking Susceptibility of Joints made of Ferritic-‑Austenitic Duplex Steel 2205 during Underwater Wet Welding

Prokop K., Rogalski G.

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2016

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Vol. 60, No. 2

35--42

EN

The underwater welding of ferritic-austenitic duplex steels is arousing growing interest inspired by the urgent need for developing welding technologies used for repairing underwater pipelines transporting oil. The tests involved underwater welding using covered electrodes (process 111). The research also involved Tekken technological tests performed under water at a depth of 0.5 m and in air as well as macro and microscopic metallographic tests, ferrite content measurements and hardness measurements of joints. The test results obtained revealed that the underwater welding of duplex steels could lead to cold crack formation. In the case considered above, cold crack susceptibility was attributed to arc burning instability.

PL

Spawanie pod wodą stali ferrytyczno-austenitycznych typu dupleks budzi coraz szersze zainteresowanie. Wynika to z pilnej potrzeby opracowania spawalniczych technologii naprawczych rurociągów do transportu ropy naftowej eksploatowanych pod wodą. Do badań wykorzystano metodę mokrą przy zastosowaniu spawania elektrodami otulonymi (proces 111). Wykonano technologiczne próby Tekken pod wodą na głębokości 0,5 m oraz na powietrzu. Przeprowadzono badania metalograficzne makroskopowe i mikroskopowe, pomiary zawartości ferrytu oraz pomiary twardości złączy. Uzyskane wyniki badań wykazały, że spawanie stali dupleks pod wodą może prowadzić do formowania się pęknięć zimnych. W rozpatrywanym przypadku związane jest to z niestabilnością jarzenia się łuku.

4

Weldability of S500MC steel in underwater conditions

Fydrych D., Łabanowski J., Rogalski G., Haras J., Tomków J., Świerczyńska A., Jakóbczak P., Kostro Ł.

Advances in Materials Science

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2014

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Vol. 14, nr 2(40)

37--45

EN

Wet welding with the use of covered electrodes is one of the methods of underwater welding. This method is the oldest, the most economic and the most versatile. The main difficulties during underwater wet welding are: high cooling rates of the joint, the presence of hydrogen in the arc area and formation of hard martensitic structure in the weld. These phenomena are often accompanied by porosity of welds and large number of spatters, which are more advanced with the increase of water depth. In this paper result of non-destructive tests, hardness tests and metallographic observations of S500MC steel joints performed underwater are presented. The weldability of 500MC steel at water environment was determined.