Community Research and Development Information Service - CORDIS

FP5

ELIXIR Report Summary

Project ID: G1RD-CT-2000-00326
Funded under: FP5-GROWTH
Country: France

Application of hydrogen diffusion rules

The aim of the work done is to determine the hydrogen behaviour of CrMo(V) steel during welding. The introduction of hydrogen during welding is something dangerous that must be taken into consideration for prescription of post-weld heat treatments. Different cases of heat treatments have been tested (measurement of H2 content before and after HT, measurement of H2 diffusion kinetics in every zones of the joints...), to generate safer Industrial Heat Treatments procedures.

Hydrogen diffusion measurements have been made on 10CrMo9.11 and 13CrMoV9.11 parent materials, simulated martensitic and bainitic HAZ and weld metals and diffusion laws defined for each material. The high trapping of hydrogen behaviour of the 13CrMoV9.11 was noted compared to the 10CrMo9.11 material.

The numerical hydrogen diffusion model within Sysweld was capable of simulating the hydrogen diffusion from the degassing test specimens.

The Sysweld numerical model successfully simulated the HAZ and microstructure of the simulated welds.

Hydrogen content measurements made on 150mm thick weldments in 10CrMo9.11 and 13CrMoV9.11 after DHT and ISR showed that DHT alone was sufficient to remove all the diffusible hydrogen in standard 10CrMo9.11. In the case of the vanadium enhanced 13CrMoV9.11, DHT alone is not sufficient to remove all the remaining hydrogen and ISR is required to remove the remaining hydrogen. The poor performance of the 13CrMoV9.11 is due to its greater ability to trap hydrogen. These measurements give end-users and manufacturers of pressure vessels a very practical feel for the efficiency of the DHT and IST treatments in these grades of steel.

The Sysweld numerical simulation of the 150mm thick section weldments and the Industrial Case Studies confirmed the relative findings of the hydrogen measurements on the 150mm thick weldments, i.e. DHT is sufficient for 10CrMo9.11 but that DHT and ISR is required for 13CrMoV9.11.

It has been shown the Sysweld numerical models can be used to predict hydrogen content in weld zones and show the relative differences between geometries, weld procedures, materials and heat treated condition but does tend to give a conservative overestimate of the hydrogen content.

Two improvements to the laws currently governing hydrogen diffusion within Sysweld are recommended:
- Hydrogen diffusion should be modelled using a second degree experimental law. This corresponds to a second degree polynominal law in log-log plot. This would provide improved predictions in the medium temperature range (200-300°C) where the existing linear laws do not fit well.

- Additional accounts needs to be taken of the effects of trapped hydrogen.

Related information

Reported by

Industeel Creusot
56, Rue Clémenceau BP 19
71201 Le Creusot
France
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