Fachzeitschrift_OeGS_03_04_2019

Abstracts aus „Welding in the World“ No. 1/2019
mit freundlicher Genehmigung des IIW
Thermo-metallurgically coupled numerical simulation
and validation of multi-layer gas metal arc welding of
high strength pearlitic rails
• L. Weingrill, M. B. Nasiri, N. Enzinger
A 3D transient thermo-metallurgical finite element simulation
of a narrow gap multi-layer gas metal arc welding of
the first ten layers of a 60E1 profile and R350HT steel rail
was implemented in SYSWELD® to study the evolution of
the temperature field, phase fractions, and the hardness in
the heat-affected zone. For validation, T (t) curves and metallography
samples from corresponding instrumented welding
experiments were used. Good agreement was reached
for what concerns the results of the simulated temperature
field and phase transformations. An inhomogeneous evolution
of the temperature field throughout the welded layers
as a result of the rail’s geometry and welding sequence
could be depicted. Based on the simulation results, preheating
is believed necessary in order to fully avoid the formation
of undesirable Bainite fractions. The hardness simulation
showed good results in sidewise locations with regard
to the rail cross section and closer to the line of fusion.
However, results were less accurate in the middle of the rail
cross section and the more the comparison points approached
the so called soft zone at the outer border of the heat
affected zone and the base material.
Formation of multi-axial welding stresses due to material
behaviour during fabrication of high-strength steel
components
• D. Schroepfer, A. Kromm, T. Kannengiesser
Today, an expanding application of high-strength steels in
modern welded constructions can be observed. The economical
use of these steel grades largely depends on the
strength and reliability of the weldments. Therefore, the
special microstructure and mechanical properties of these
grades have to be taken into account by keener working
ranges regarding the welding parameters. However, performance
and safety of welded components are strongly affected
by the stresses occurring during and after welding fabrication
locally in the weld seam and globally in the whole
component, especially if the shrinkage and distortion due to
welding are restrained. Some extensive studies describe the
optimization of the welding stresses and the metallurgical
effects regarding an adapted welding heat control. Lower
working temperatures revealed to be particularly effective
to reduce the local and global welding-induced residual
stresses of the complete weld significantly. However, decreased
interpass temperatures cause concurrently higher
stresses during welding fabrication. This work shows strategies
to reduce these in-process stresses. With help of multiaxial
welding stress analyses in component-related weld
tests, using a special 2-MN-testing facility, differences in
stress build-up are described in detail for root welds, filler
layers and subsequent cooling to ambient temperature.
Effect of friction spot welding parameters on the joint
formation and mechanical properties of Al to Cu
• M. Cardillo, J. Shen, N.de Alcântara, C. Afonso,
J. dos Santos
Friction spot welding is an appealing technique for joining
dissimilar materials, such as aluminum and copper that
have significant differences in physical and mechanical properties.
To optimize the welding process, a full-factorial
design was employed. It is found that in addition to the
plunge depth, the interaction between the rotational speed
and the plunge depth significantly influences the lap-shear
strength of the Al/Cu dissimilar joints. Further investigations
on macro- and microstructures show that increasing
the plunge depth could deform the Cu sheet into a concave
shape to form a mechanical interlocking, and thus increase
the joint lap-shear strength; increasing the tool rotational
speed, however, may compromise this effect because of
the formed tunnel defects on the interface due to high
thermal exposure.
Transient liquid phase bonding of Inconel 617 superalloy:
effect of filler metal type and bonding time
• A. Farzadi, H. Esmaeili, S. E. Mirsalehi
Transient liquid phase (TLP) bonding has enormous potential
to repair cracks in the gas turbine hot section parts that
are made of Ni-based alloys. The experiments were carried
out by BNi-1 and BNi-2 filler metals in a vacuum furnace at
the bonding times of 45 and 300 min. The shear strength,
microhardness, microstructure, and homogeneity of chemical
composition during TLP bonding of Inconel 617 superalloy,
which is the base metal, were evaluated. The shear
strength of about 620 MPa was obtained using the BNi-1 filler
metal. Hence, the BNi-1 filler metal and the bonding
time of 300 min are recommended for repair of hot section
components of a gas turbine. The gap size is an important
parameter on the diffusion especially at the lower bonding
times but the preliminary difference in the chemical composition
may play an important role at the longer bonding
times. The results show that the type of filler metal is an
important parameter in this process.
66 SCHWEISS- und PRÜFTECHNIK 03-04/2019