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Through Optimum Use and Innovation of Welding and Joining Technologies
Improving Global Quality of Life
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Improving Global Quality of Life
Through Optimum Use and In ov tion f Welding and Joining Technologies
Another “green topic”, pressure equipment for the wide use of hydrogen as a substitute for fossil fuels,
requires a large, international effort. It must be aimed at understanding, characterising and predicting the
performance of welded materials in high pressure hydrogen. An effective testing programme first requires
identifying objectives and a strategy based on true understanding of the phenomenon and potential damage
scenarios. Certainly the residual stresses and microstructural changes caused by welding will make or break
hydrogen as a practical alternative.
There is no shortage of data on hydrogen embrittlement of high strength steels. They will not be used,
however. There is a need for data, appropriate to the specific infrastructural materials (lower strength steels
in many situations) and their welds as encountered in the envisioned applications. There is not yet a cohesive
engineering database applicable to these likely materials to be employed in long term cyclic contact with
hydrogen as part of consumer’s life style in the transportation industry and its supporting infrastructure.
The various manifestations of hydrogen embrittlement have been well known and studied for a century.
Certainly many hundreds of millions of dollars have been spent on programmes on hydrogen embrittlement
research. If new programmes are to make a difference they must be well conceived and lead to more
practical knowledge than is currently available. Some of the significant issues are as follows:
There must be:
A mechanistic appreciation of the fundamentals of the materials-environment interaction at the
materials surface as affected by stress, stress concentrations, time, temperature, strain rate surface
films, gas phase impurities and others.
Comprehension of potential effects of materials fabrication and joining technologies that will be
employed.
Attention to detail so that effective quality assurance programmes may be established for welded
construction.
Correlation of conventional toughness measures with performance in high pressure hydrogen.
An understanding of the role of minor elements on susceptibility to crack growth. Foreign and
domestic materials specifications have different aim ranges.
Adequate quality assurance/control of materials and processes. The requirements must be based
on concepts of where and how hazards may be introduced inadvertently and what and how safety
margins need to be developed and justified. The matrix of concerns needs to include properties
under conditions resulting from accident, fire, hydrogen contamination, and long term ageing of
welded components.
9.5.3
Hot topics
The increasing trend to extremely high pressures and temperatures - allowable pressures up to 10,000 bar
in food processing, powder metallurgy and waste treatment; allowable metal temperatures up to
1,250
°C in the petrochemical industry and down to –273°C in air separation plants.
Unification of codes and procedures for, and better understanding of, residual stress estimates for
fitness for service.
Utilisation of hydrogen as a “green” alternative to fossil fuels will require understanding,
characterisation and prediction of the performance of welded materials in high pressure hydrogen
environments.
Economic considerations with regard to extension of equipment life, and ecological considerations
with regard to leak-tightness and risk reduction.
9
Needs and challenges of major industry sectors for future applications
