ISO/TR 17671-2-2002 pdf free download.Welding – Recommendations for welding of metallic materials – Part 2: Arc welding of ferritic steels.
This part of ISOITR applies to ferritic steels excluding ferritic stainless steels. This includes steels referenced in groups 1 to 7 of ISOITR 15608:2000. When ordering steel it may be necessary to specify requirements concerning weldability, which can involve specifying additional requirements to those given in the relevant steel standard.
6 Weldability factors
The properties and the quality of welds are particularly influenced by the welding conditions. Thus, the following factors should be taken into consideration:
— joint design;
— hydrogen-induced cracking;
toughness and hardness of the heat affected zone (HAZ); solidification cracking;
lamellar tearing:
corrosion.
The mechanical and technological properties, in particular the hardness and toughness of the heat affected zone in a narrowly delineated area, can be influenced to a greater or lesser degree. compared with the properties of the parent metal and depend on the welding conditions. Experience and tests indicate that, not only the properties of the narrow affected zone of lower strength and better flexibility, but also the load distribution effect of the tougher adjacent zones should be taken into account when assessing the ductility and safety against fracture of welded joints as this could affect the choice of steel.
7 Handling of welding consumables
When special protection or other treatment during storage or immediately prior to use is recommended by the consumables’ manufacturer, these consumables should be treated in accordance with the conditions detailed by the manufacturer.
When drying or baking, consumables should be removed from their original containers. After removal from the oven, the consumables should be protected from exposure to conditions conducive to moisture absorption. In the case of welding consumables that have been specially packaged, eg. using vacuum or other moisture-resistance means, advice from the consumables’ manufacturer should be sought as to further steps required for drying and baking.
8.1 Butt welds
Butt joints between parts of unequal cross-section should be made and subsequently shaped such that a severe stress concentration at the junction is avoided.
Some examples of joint preparations for use with metal-arc welding with covered electrodes and gas-shielded metal-arc welding are given in ISO 9692-1.
Partial penetration butt joints may be permitted dependant on the design specification. Consideration should be given to the choice of weld preparation and welding consumables in order to achieve the specified throat thickness. Under fatigue conditions, partial penetration joints or the use of permanent backing material may be undesirable.
Backing material may consist of another steel part of the structure when this is appropriate. When it is not appropriate to use part of the structure as backing material, the material to be used should be such that detrimental effects on the structure are avoided and should also be agreed in the design specification.
Care should be taken when using copper as a backing material as there is a risk of copper pick-up in the weld metal.
Where temporary or permanent backing material is used, the joint should be arranged in such a way as to ensure that complete fusion of the parts to be joined is readily achieved.
Wherever the fabrication sequence allows, tack welds, attaching permanent backing should be positioned for subsequent incorporation into the weld (see clause 14 of ISO!TR 17671-1:—).
8.2 Fillet welds
Unless otherwise specified, the edges and surfaces to be joined by fillet welding should be in as close contact as possible since any gap may increase the risk of cracking. Unless otherwise specified, the gap should not exceed 3 mm. Consideration should be given to the need to increase the throat of the fillet weld to compensate for a large gap.
Unless otherwise specified, welding should not start/stop near corners, instead, it should be continued around the corners.
9 Welds in holes or slots
Due to the risk of cracking, holes or slots should not be filled with weld metal unless required by the design specification. Holes or slots that are required to be filled with weld metal shall only be filled after the first run has been found to be acceptable (see also BA).ISO/TR 17671-2 pdf download.