DIKUL - logo
(UM)
  • Effect of soft root weld layer on fracture toughness of under-matched weld joints on Q+T steel
    Rak, Inoslav ...
    Welding of quenched and tempered (Q+T) high strength low alloyed steels can cause weld strength undermatching to satisfy the toughness requirements for the weld deposit. The cost of preheating of ... these steels can be saved if we can prove that the use of soft electrodes for root passes does not endanger the overall quality of the joint. There is a need to conduct systemstic work to determine the fracture behaviour of undermatched HSLA steel welds. By welding of 40 mm thick Q+T structual steel (grade HT 80), overmatched condition had appeared in the root area of the X groove weld despite of welding consumable which would give the entire weld undermatched properties. This is the effect of weld metal alloying by elements from the base material.So, the weld crack is not protected agains cold cracking, especially in the root region, therefore a high preheating should be used to reduce the possibility of this phenomenon. In this work soft (lower strength) filler metal was used for the first two and four weld passes of the X-joint. In this case the root area was also alloyed by elements from the base material and the obtained mis-matching factor was higher than expected. So, one homogeneous and two non-homogeneous weld joints were considered. The mechanical properties of weld joints were measured by round tensile bars taken from different parts of the weld. The undermatching factor of weld joint with two and four soft root passes was around 0.80-0.90 in the soft root layer. It was expected that uneven strength distribution along the fatigue crack tip line would affect fracture initiation behaviour of all three different welded joints. CTOD fracture toughness was measured on SENB 2BxB (a/W=0.5) specimens at the temperature of -10oC for WM and HAZ. CTOD values were clearly influenced by softer material in the root layer. The metallographic post-test sectioning has revealed the initiation points (LBZs) mainly at the lowest weld metal strength.
    Vir: Proceedings of the 15th International Conference on Offshore Mechanics and Arctic Engineering. Vol. III, Materials engineering (Str. 393-402)
    Vrsta gradiva - prispevek na konferenci
    Leto - 1996
    Jezik - angleški
    COBISS.SI-ID - 3361046

Vnos na polico