In this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of high-strength low-alloy S460N steel to cold cracking. During experiments diffusible hydrogen content in deposited metal determination by mercury method, metallographic macro- and microscopic testing and hardness measurements were performed. Investigations showed that waterproof coatings laid on covered electrodes can improve the quality of wet welded joints, by decreasing the Vickers HV10 hardness in heat-affected zone and decreasing the diffusible hydrogen content in deposited metal, which minimalize possibility of cold cracking.

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Effect of electrode waterproof coating on quality of underwater wet welded joints

Extreme atmospheric conditions in the marine and offshore industry are harmful to engineering materials, especially to welded joints, and may cause degradation of their properties. This article presents the results of research on the plasticity of bead-on-plate welds made using two types of seamless, copper plated flux-cored wires. Before welding, spools with wire were stored for 1 month in two distinct locations with different geographical and industrial conditions in Poland, and then subjected to visual examination. Bead-on-plate welds were subjected to a static tensile test and on this basis plasticity indexes showing the effect of storage on plasticity were determined. The fractures after tensile tests and the surfaces of the wires were examined on an electron scanning microscope. Additionally, diffusible hydrogen content in deposited metal measurements for each condition were carried out. The highest degradation level was found for wire stored in an agricultural building in north-eastern Poland—there was an almost fourfold decrease in the plasticity index value and the highest diffusible hydrogen content. For the same wire and the same location, the largest difference was also observed in fracture morphology after the tensile test—ductile fracture was obtained for wire at delivery condition while an almost full cleavage fracture was found after relatively short (1 month) storage of wire.

Plasticity of Bead-on-Plate Welds Made with the Use of Stored Flux-Cored Wires for Offshore Applications.

Fusion welding of ultra-high strength structural steels – A review

Hydrogen can have an extreme degradation effects in steels, particularly concerning the mechanical properties. These effects can lead to hydrogen assisted cracking in micro-alloyed high strength steels during fabrication and/or operation in industrial applications. The Carrier Gas Hot Extraction method, which functionally combines a mass spectrometer with a Thermal Desorption Analysis process, was used for the detection of ultra-low diffusible hydrogen concentrations in the material specimens. The work shows the interaction between hydrogen and lattice defects in different micro-alloyed materials and HAZ. These steels were prepared in a quenched and tempered condition and in a thermo-mechanically rolled condition. The trapping characteristics of two steel grades, S690QL and S700MC, were studied with respect to the activation energy dependent on carbon content and micro-alloying elements such as Ti, Nb, Mo, Cr and V. The two steel grades exhibited several types of traps: carbide formations, dislocations and/or grain boundaries were common, which can influence activation energy and hydrogen solubility. The type and dimension of inclusions or particles also affected the hydrogen trapping behavior. A decrease of carbon and specific alloying elements in MC steels led to a change in the activation energy binding the trapped hydrogen. This thermo-mechanically hot
rolled steel revealed an increased interaction between hydrogen
and precipitations. The higher carbon content in the
quenched and tempered steel led to a higher interaction
between hydrogen and iron carbide, specifically in the
martensitic phase. Furthermore,the trapping behavior in HAZ showed a significant increase in activation energy, especially in the coarse grained microstructure.

Thermal desorption analysis of hydrogen trapping in micro-alloyed high strength steels

In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS.

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Advanced High-Strength Steels for Automotive Applications: Arc and Laser Welding Process, Properties, and Challenges

Hydrogen-assisted cracking of GMA welded 960 MPa grade high-strength steels

The invention relates to a method for producing conventionally hot-rolled strip products, wherein a steel alloy is melted, the melted steel alloy is cast into slabs and the slabs are hot-rolled to a desired degree of deformation of a desired strip thickness after heating to above Ac3, the alloy is rolled above the recrystallization temperature, the strip is cooled to room temperature after the rolling and, for the purpose of hardening, is briefly heated to greater than Ac3 and cooled again, characterized in that the heating occurs with a temperature rise of more than 5 K/s, preferably more than 10 K/s, particularly preferably more than 50 K/s, in particular more than 100 K/s, and is stopped at a desired target temperature of 05 to 60 s and then cooling occurs

Method for producing conventionally hot-rolled strip products

Die Erfindung betrifft ein Verfahren zum Herstellen von konventionell warmgewalztenWarmbanderzeugnissen, wobei einen Stahllegierung erschmolzen wird, wobei oberhalb der Rekristallisierungstemperatur der Legierung gewalzt wird, wobei die erschmolzene Stahllegierung in Brammen gegossen wird und die Brammen nach einer Aufheizung oberhalb Ac 3 bis zu einem gewunschten Umformgrad einer gewunschten Banddicke warmgewalzt werden, wobei das Band nach dem Walzen abgekuhlt wird und zum Zwecke des Hartens bzw. Hartens und Anlassens kurzzeitig aufgeheizt und wieder abgekuhlt wird, dadurch gekennzeichnet, dass das Aufheizen mit einer Temperatursteigerung von mehr als 100 K/s stattfindet und bei einer gewunschte Zieltemperatur von 0,5 bis 60 s gehalten wird und dann eine Abkuhlung erfolgt.

Helmut Spindler

Papers

Hydrogen-assisted cracking of GMA welded 960 MPa grade high-strength steels

Method for producing conventionally hot-rolled strip products

Verfahren zur Herstellung von konventionell warmgewalzten Warmbanderzeugnissen