Dariusz Fydrych

Underwater Welding - A Review

Underwater Welding - A Review The paper describes principles of underwater welding and recent trends in research works undertaken for enhance welding technology and properties of underwater welds. Department of Materials Technology and Welding at Gdansk University of Technology (GUT) has been involved in underwater welding research for over 25 years. Investigations include technology of underwater welding, and weld properties examinations. All tests have been performed with the use of self designed stands allow to perform welds in shallow depths as well as the depths up to 1000 m. The main investigation directions performed at the Department of Materials Technology and Welding are presented: Weldability of HSLA steel and factors influencing susceptibility to cold cracking of welded joints. The effects of wet welding conditions on diffusible hydrogen amount in the welds. The effects of heat input, underwater welding depths and composition of shielded gases on welds toughness.

Weldability of high strength steels in wet welding conditions

Abstract In this paper are characterized problems of high strength steel weldability in underwater wet welding conditions. Water as a welding environment intensifies action of unfavourable factors which influence susceptibility to cold cracking of welded steel joints. The susceptibility to cold cracking of S355J2G3 steel and S500M steel in wet conditions was experimentally estimated (by using Tekken test). It was concluded that the steels in question are characterized by a high susceptibility to formation of cracks in welds. Usefulness of the proposed Temper Bead Welding technique (TBW) was experimentally verified as a method for improving weldability of the steels in the analyzed conditions.

Effect of shielded-electrode wet welding conditions on diffusion hydrogen content in deposited metal

Wet welding is the most popular method of joining in aquatic environments. During underwater joining, the weldability of steel is limited by the higher cooling rates and hydrogen content in the welded metals. This article presents the results of preliminary tests on the effect of wet welding conditions on diffusion hydrogen amounts. Seven parameters were optimized using a Plackett–Burman design to get the most relevant variables. These parameters were salinity of water, contamination of electrode, electrode polarity, and welding current.

Temper bead welding of S420G2+M steel in water environment

Abstract The article presents the idea of the use of Temper Bead Welding (TBW) technique to improve the weldability of high strength steel at underwater wet welding conditions. Wet welding method with the use of covered electrodes is described. This work shows results of metallographic examinations and hardness measurements of samples of S420G2+M steel with weld beads performed under water. It has been shown that Temper Bead Welding technique may provide a way to reduce the hardness of the welds, thus is a useful method for improving weldability of high strength steel welded in underwater conditions. The optimum overlap of weld beads (pitch) was set of 55÷100%.

Bead-on-plate welding on S235JR steel by underwater local dry chamber process

Abstract The article presents the results of the effect of parameters of underwater local dry chamber welding on the properties of padding welds. The effect of heat input and the type of shielding gas on the structure and hardness of welds was established. the functions for estimating the maximum hardness of the heat affected zone have been also elaborated

Effect of underwater local cavity welding method conditions on diffusible hydrogen content in deposited metal

One of the methods with great potential for applications in underwater repairs is local cavity welding. In local cavity method, cooling conditions and diffusible hydrogen amount in weld metal are nearly the same as those existed during welding in the air. This paper presents the results of literature survey and preliminary tests of the effect of local cavity welding conditions on diffusible hydrogen amount in a deposited metal. A Plackett–Burman design was applied to screen seven parameters: thickness of elastic cover, stick-out of electrode wire, welding current, voltage, travel speed of welding, salinity of water, and flow rate of shielding gas.

The effect of wet underwater welding on cold cracking susceptibility of duplex stainless steel

Abstract The present work was conducted to assess the weldability of duplex stainless steel in underwater conditions. Metal manual arc welding (MMA) with the use of coated electrodes was used in the investigations. Tekken weldability tests were performed underwater at 0.5 m depth and in the air. Nondestructive tests, metallographic examinations of welds, ferrite content assessment in microstructure and hardness test were performed. The good weldability at underwater conditions of duplex stainless with the use of MMA method was confirmed, however difficulties in stable arc burning were revealed.

The Effect of Welding Conditions on Diffusible Hydrogen Content in Deposited Metal

The primary limitation of weldability of high strength low alloy steel is susceptibility to cold cracking. The important reason of the formation of cold cracks, besides forming brittle structure and residual stresses, is the presence of diffusible hydrogen in welded joint. The most effective methods reducing the susceptibility to cold cracking are connected with decreasing the amount of potential hydrogen. This process may be carried out in technological (drying welding filler materials, preheating components) or in a metallurgical way (filler metals with austenitic structure, adding rare-earths elements to filler metals as traps for hydrogen atoms in steel). The possibility to minimize the amount of diffusible hydrogen by changing the welding parameters seems to be particularly interesting. The article presents the results of a literature survey and preliminary tests which set out effects of welding conditions on the amount of diffusible hydrogen in deposited metal. Experiments were conducted by using rutile coated electrodes which generate high contents of diffusible hydrogen in deposited metal. The amount of diffusible hydrogen was determined by a glycerin test. Eleven factors were considered: the electrode angle, the grinding of sample, the preheat temperature, the polarity of welding current, the welding current, the welding – cooling time, the electrode usage, the time of welding, the thickness of specimen, the welding – measurement time and thickness of electrode coating. All factors were optimized using a Plackett-Burman design to get the most relevant variables. The results of the preliminary tests indicate that appropriate choice of welding parameters may considerably reduce diffusible hydrogen in deposited metal. However, the range of parameters is limited by the necessity of providing stability of the welding process and obtaining required properties of the welded joint.

Weldability of S500MC Steel in Underwater Conditions

Abstract 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

Diffusible Hydrogen Control in Flux Cored Arc Welding Process

One of the types of hydrogen degradation of steel welded joints is cold cracking. The direct cause of the formation of cold cracks is simultaneous presence of hydrogen, residual stresses and brittle structure. The way of preventing the occurring of degradation is to eliminate at least one of these factors. Practice has shown that the best solution is to control the amount of hydrogen in deposited metal. In this paper an experimental evaluation of the effect of the welding parameters on the content of diffusible hydrogen in deposited metal obtained from rutile flux cored wire grade H10 was carried out. The state of the art of considered issues was described and results of preliminary investigations were presented. Five factors were considered: the flow rate of shielding gas, the welding current, the arc voltage, the welding speed and the electrode extension. All factors were optimized using a Plackett-Burman design to get the most relevant variables. The level of diffusible hydrogen was determined by a glycerin test. The results of the experiment indicate that appropriate choice of welding parameters may significantly reduce diffusible hydrogen content in deposited metal.