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Effect of weld penetration depth on hydrogen-assisted cracking of high-strength structural steels
(2019)
The need for steels with highest mechanical properties is a result of the increasing demands for energy and resource efficiency. In this context, high-strength structural (HSS) steels are used in machine, steel and crane construction with yield strength up to 960 MPa. However, welding of HSS steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of (1) microstructure, (2) local stress/strain and (3) local hydrogen concentration. In addition to the three main factors, the used weld-arc process is also important for the performance of the welded joint, especially when using modern arc variants. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of HSS grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been used increasingly for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared to the conventional process. Economic benefits of using this arc type are: a reduced number of necessary weld beads and a lower weld seam volume, which result in decreased total welding time and costs. Nonetheless, investigations on a high-strength S960QL showed significantly higher hydrogen concentrations in the weld metal at a reduced seam opening angle with Mod. SA. This indicates an increased susceptibility of the welded component to HAC. Hence, existing recommendations on HAC-avoidance cannot be transferred directly to the Mod. SA-process. In the present study, the susceptibility to HAC of the HSS steel S960QL with same type of filler material was investigated. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. For assessment of the HAC susceptibility, the externally loaded implant test was used. Both conducted test series with Conv. A and Mod. SA showed similar crack critical stress of about 280 MPa. Below this value, no delayed fracture appeared. The welds with Mod. SA showed higher hydrogen concentrations. The fracture occurred in the heat-affected zone (HAZ) or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared to tests carried out with Conv. A.
Metallic organic frameworks are the materials stirring great interest by their large variety of structure types and chemical composition as well as low density and very high surface area, which are desirable properties for gas storage such as for hydrogen, methane or carbon dioxide. Using different so called secondary building units offer an opportunity to form tunable structures with channels of various geometry and allow in this way to study the absorption of the molecular hydrogen, methane or carbon dioxid in the systematic way.
The subject of permeation of hoses according to ISO 3821 for
hydrogen was discussed for a long time in ISO/TC 44/SC 8. The reason
is a considerable leakage of hydrogen diffused into the hose material
over the end face of the hose. Because of this unsolved, safety-related
problem of hoses sold on the market, measurements should be carried
out in order to be able to better assess the problem. BAM has declared
its attendance to provide a required fast solution to this issue.
A conclusion on the WIPANO research project "Safety of Prestressing Steel" was presented in the final committee meeting at the end of the project. The project's exciting findings and recommendations for a new method were discussed with the audience of national and international stakeholders of the prestressing steel industry and representatives of inspection bodies and standardization.
This talk reports the findings of the WIPANO "Knowledge and Technology Transfer via Patents and Standards" research project "Safety of Prestressing Steels," founded by the German Ministry of Economic Affairs and Climate Action (BMWK). A new test method for assessing the susceptibility of prestressing steels to hydrogen-induced stress corrosion cracking (SCC) is presented, which serves the demands of a lower scattering compared with the present standard. Moreover, the ability to differentiate between high susceptible and low susceptible prestressed wires is possible, modifying the method by hydrogen charging and surface preparation.
Hydrogen plasma treatment of iron ores or iron oxide containing wastes can be an efficient option to produce green iron e.g. for steel production. This way iron oxide is reduced to metallic iron in the liquid form by the highly reactive species that are formed in a hydrogen plasma. Hydrogen plasma can be used at the same time to remove undesired gangue elements. The presentation shows the experimental setup, shows first results of iron ore reduction by hydrogen plasma and gives an outlook for industrial application of the technology.
The polymer chemical structure of the polyimide has a major influence on the tribological behaviour. The addition of graphite in PI2 has a beneficial effect in hydrogen on the friction and wear. The low friction of graphite is associated with a lubricant film in hydrogen. The influence of hydrogen on graphite is more effective than humidity. CNTs have a similar effect to that of graphite in PEEK composites. TiO2 particles improve significantly the wear rate both in vacuum and hydrogen environment. In LH2 friction and wear decrease for unfilled polymers. Friction of graphite filled composites increases slightly and wear rate is stable.
This lecture deals with the sliding behaviour of polymer materials in hydrogen environment. After a short introduction of the hydrogen activities at BAM, the tribological performances of polymer materials in gaseous hydrogen are presented and compared with air and vacuum environment. The second part focusses on the influence of the counterface materials in hydrogen. Finally, the last section is dedicated to experiments liquid hydrogen.
The focus of this study is to evaluate of hydrogen on the friction and wear behavior of a wide range of polymer materials. Thereby, the tribological performance of filled and unfilled polymers from different suppliers were compared at room temperature in air and hydrogen gas (H2) as well as in liquid hydrogen at -253°C (LH2).
This presentation deals with the influence of the counterface materials on the sliding behaviour of some polymer materials in hydrogen. Polyimide (PI), polyetheretherketone (PEEK) and Polytetrafluoroethylene (PTFE) materials were investigated against hardened 52100 martensitic bearing steel and 304 austenitic stainless steel with similar roughness (Ra = 0.2 μm). Results indicate that the friction and wear of PI and PEEK materials depend on the counterface material. This effect wasn’t observed for PTFE composites.
While the tribological performance of polyimide is better against 52100 in hydrogen, improved sliding behaviour of PEEK materials is observed with 304 counterface, particularly at higher sliding speed. Surface analyses of the transfer film reveal that the influence of the counterface is primarily related to the chemical nature of the steel for PI and to the thermal conductivity of the disc for PEEK materials.
The tribological behaviour of polyetheretherketone (PEEK) and polyimide (PI) composites was investigated in air, vacuum and hydrogen environments. Polymers were filled with graphite, submicron particles or carbon nano-tubes. Experiments reveal that hydrogen environment has a major influence on both polymer structure and fillers during sliding. The sliding behaviour of these polymer composites is much improved in hydrogen compared to air. In particular, graphite and nano-particles have a remarkable effect on friction and wear, respectively.
The tribological characteristics of pure and graphite filled polymers were investigated in gaseous hydrogen at ambient temperatures and in LH2 at -253°C. It could be shown that the tribological properties of PI and PEEK materials is related to the formation of a transfer film. The influence of both hydrogen and cryogenic temperatures will be discussed in the presentation.
The development of hydrogen technologies is a key strategy to reduce greenhouse gas emission worldwide. Power-to-Gas is a challenging solution, in which hydrogen and methane can be used in mobility, industry, heat supply and electriity generation applications. This presentation deals with the tribological behaviour of polymer materials in hydrogen and methane, both in gas and in liquid form.
Introduction of H2Safety@BAM
(2021)
This contribution for the Open Forum of the 8th HSN Symposium introduces the SensRef activities of the Competence Centre H2Safety@BAM.
This tutorial provides an overview of the utilization of sensor systems in hydrogen technologies. It discusses the necessary criteria and characteristics of sensor systems, and also demonstrates practical applications of these technologies in terms of safety and process control. Emphasis is placed on various types of sensors such as gas sensors, pressure sensors, temperature sensors, and gas flow sensors. These systems find application in monitoring and regulating operational parameters, detecting potentially dangerous situations, and activating alarm systems.
The success of this energy transition and the efficient utilization of green hydrogen as a pristine energy carrier hinge upon the cultivation of hydrogen readiness, swift market expansion, and the establishment of crucial value chains within national and European contexts. Paramount to these objectives are reliable quality and safety standards, essential for ensuring supply safety, environmental compatibility, and instilling confidence in these technologies.
In the realm of safety management systems, gas sensors emerge as vital components for detecting hydrogen. This presentation delves into the imperative role of hydrogen systems, emphasizing their capability to monitor and control operations, issue warnings, signal hazardous conditions, and sound alarms. It explores the intricate landscape of functional safety considerations and addresses the challenges associated with measurement uncertainty in sensor testing.
A diverse array of sensors catering to hydrogen, pressure, temperature, and flow are available, each contributing significantly to the safety and efficiency of hydrogen technologies. Applications are envisaged to adhere meticulously to quality infrastructural regulations, codes, and standards, ensuring seamless integration and operation within the broader hydrogen ecosystem.
This discussion underscores the ubiquitous presence of sensor systems across various fields within hydrogen technologies, illustrating their multifaceted contributions to safety, reliability, and overall success in realizing the transformative potential of green hydrogen.
The success of this energy transition and the efficient utilization of green hydrogen as a pristine energy carrier hinge upon the cultivation of hydrogen readiness, swift market expansion, and the establishment of crucial value chains within national and European contexts. Paramount to these objectives are reliable quality and safety standards, essential for ensuring supply safety, environmental compatibility, and instilling confidence in these technologies.
In the realm of safety management systems, gas sensors emerge as vital components for detecting hydrogen. This presentation delves into the imperative role of hydrogen systems, emphasizing their capability to monitor and control operations, issue warnings, signal hazardous conditions, and sound alarms. It explores the intricate landscape of functional safety considerations and addresses the challenges associated with measurement uncertainty in sensor testing.
A diverse array of sensors catering to hydrogen, pressure, temperature, and flow are available, each contributing significantly to the safety and efficiency of hydrogen technologies. Applications are envisaged to adhere meticulously to quality infrastructural regulations, codes, and standards, ensuring seamless integration and operation within the broader hydrogen ecosystem.
This discussion underscores the ubiquitous presence of sensor systems across various fields within hydrogen technologies, illustrating their multifaceted contributions to safety, reliability, and overall success in realizing the transformative potential of green hydrogen.
The use of duplex stainless steels (DSS) in energy related applications is well known. Nowadays, DSS steels become more favorable than austenitic steels due to the outstanding mechanical properties, the good corrosion resistance and the lower nickel content. However, the use of the duplex grade in acidic environments such as seawater often leads to severe degradation of the structural integrity of the steel by hydrogen-induced/assisted cracking (HAC) phenomena, which can eventually result in premature failure. Hydrogen assisted degradation and cracking of steels are active fields of research even though this topic is intensively studied for more than a century. A bottleneck is the analytical validation of the theoretical models proposed ion the literature at the sub-micron scale.
Industrial and the research communities see a need for an accurate analytical method by which it is possible to image the distribution of hydrogen in the microstructure of a steels or and other alloys. Among the very few available methods hydrogen imaging methods, Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) has the principal capability for mapping of hydrogen in a steel’s microstructure. The combination of ToF-SIMS with multivariate data analysis (MVA), electron microscopy (SEM) and electron-backscattered diffraction (EBSD) is a powerful approach for providing chemical and structural information. The use of data fusion techniques has been shown recently to enhance the better understanding of the hydrogen induced degradation processes in in a DSS steel.
The objective of this work is to find a method that describes the degree of damage from an impact experiment. This experiment was performed on Composite Pressure Vessels (CPV) in order to find the correlation of impact damage to the residual burst pressure. Computed Tomography (CT) approach was used to capture the before and after impact condition of the CPVs. The Wasserstein function was used to calculate how much the after impact image has differed from the original one. In the end, a good correlation was obtained to the residual burst pressure. The smaller the Wasserstein distance is, the higher the residual burst pressure would be and vice versa.