A common failure is internal cracks resulting from too great a weld penetration in relation to width. To avoid centerline cracking, it is necessary to keep the ratio of the weld width to weld depth between 1 to 1 and 1. 4 to 1. This ratio can be held by setting welding speed and current to avoid excessive depth and by designing the joint to give a favorable ratio. Researchers have identified several prerequisites for hydrogen cracking. Besides hydrogen in diffusible form, cracking requires stress and a crack-sensitive microstructure. Temperatures must be below 400 F (205 C). Usually, failure takes place at about 50 to 100 F (10 to 40 C), cold cracking; and it may show up hours later, hence the term delayed cracking. Hydrogen most often gets into the weld by way of moisture in the arc atmosphere. Or it may come from moisture on the steel, perhaps entrapped in rust. The moisture might come in on the electrode covering or in a flux. It might be present because of improper handling or storage in a damp atmosphere. Lamellar tearing is associated with high welding stresses generated in the through-thickness direction of steel plate. The variables in tearing are the through-thickness properties of the plate, the strain induced by welding, and restraint as determined by thickness of the steel or by joint design. In addition to a stress or strain at right angles to the surface of the plate, an arraoy of second-phase particles such as sulfide inclusions parallel to the plate surfaces must be present; and properties of the base-metal matrix between the particles must promote joining of the voids. The basic design rationale in reducing lamellar tearing is to arrange the connection so that the maximum strain occurs in some other direction than through the thickness of the plate.

  • Corporate Authors:

    IPC Science and Technology Press Limited

    IPC House, 32 High Street
    Guildford, Surrey  England 
  • Authors:
    • Dermott, R G
  • Publication Date: 1961-10

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Filing Info

  • Accession Number: 00152701
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Sep 20 1977 12:00AM