Page 30 - SSAB Welding Handbook Edition 2

©2009-2019 by SSAB Group of companies (SSAB). All rights reserved. Only digital PDF file. No distribution. No printing allowed!
No part of this handbook may be reproduced in any form or by any means without permission in writing from SSAB.
4.0 Hydrogen cracks Welding handbook

in the section: Preheat levels for the Strenx
and Hardox grades in this chapter
©SSAB
- Store opened packages of consumables
according to the directions from the
manufacturer.
Welding consumables with higher strength
4 Avoid excessive levels of residual stresses in the
Welding consumables with lower strength
joint. Recommended measures in this respect are to:
- Use consumables with the appropriate yield
Fig. 4.12: A multi pass joint welded with consumables of different
strengths. strengths according to the recommendations
from SSAB.
- Do not use a welding procedure that produces
4.15 Critical size and acceptance unnecessarily high residual stresses in the joint.
levels of hydrogen cracks Suitable measures are:
4 To keep the gap size in the joint to a
Hydrogen cracks can be accepted to a certain extent maximum of 3mm.
in some structures. In these cases, the critical crack 4 To perform start and stop welding sequences
size and acceptance levels can be calculated at least 50 mm-100 mm away from corners,
according to standard regulations. In other structures, if possible.
hydrogen cracks are not allowed to be present. When 4 That the minimum length of a tack weld in
the international standard EN ISO 5817 is followed, the joint shall generally be 50 mm each. The
hydrogen cracks in a structure are not accepted in any exception is for plate thicknesses up to 8mm
weld class. The normal recommendation from SSAB where shorter tack lenghts than that may be
is to remove all hydrogen cracks since assessment of applied.
potential hydrogen cracks is not evaluated for most 4 That it is particularly beneficial to weld with
welded structures. consumables of different strengths in order
to avoid hydrogen cracks in multi-pass joints
in the Strenx grades. Tack welds and the
4.16 Summary of measures to first passes are welded with low strength
minimize the risk for hydrogen consumables and high strength consumables
cracks in joints are then used for the remainder of the passes.

In this chapter, the different issues regarding the
nature of hydrogen cracks and how to minimize their
risk are discussed.

A compilation of these measures is found below:
4 Keep the hydrogen level in the joint sufficiently
low. Recommended measures in this respect are to:
- Use consumables with low diffusible hydrogen
contents of up to 5 ml H /100g of weld metal.
2
- Keep the joint clean from contaminations like
water, grease and oil.
- Follow the preheat recommendations described

30 This handbook contains general suggestions and information without any expressed or implied warranty of any kind. SSAB hereby expressly disclaims
all liability of any kind, including any damages, in connection with the use of the information and for their suitability for individual applications.
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.