Abstract: Joining by forming of magnesium alloys is restricted by the limited forming capability of
magnesium at room temperature. For this reason heating of the parts to temperatures of 220 °C or
more is required to form joints without cracks. State-of-the-art joining by forming methods (such as
clinching or self-pierce riveting) are usually working with a contoured die as a counter tool.
Researches on these joining methods have shown that a minimum heating time of 3 to 6 seconds is
needed to achieve joints of acceptable quality. In this paper two new clinching methods “dieless
clinching” and “dieless rivet-clinching” shall be introduced. Both methods work with a flat anvil as
a counter tool, thus offering important advantages for the application in joining of Mg/Mg, Al/Mg
or Fe/Mg joints. In joining by forming with a flat counter tool the proportion of crack inducing
tensile stresses in the bottom part during the joining process is very low. Moreover the heat transfer
between the heated anvil and the parts is comparatively fast. That makes it possible to decrease the
heating time in joining by forming with a flat counter tool to only one second or less. The dieless
clinching process was simulated using the Finite Elements Method (FEM) to analyze the influence
of geometrical parameters of the punch and the process parameter clamping force. Furthermore the
limitations of the new dieless joining method were investigated.
Abstract: Braze Pressure Welding (BPW) with high frequency induction heating is a newly developed
pressure welding technique using interlayer metals for welding the general steel pipes for pipe arrangement in
buildings. BPW enables to make joints by solid-state welding in air using a flux sheet which is also developed
for this technique. In this method, the interlayer metal is expected to play the primary role in making high
performance joints. At a joining temperature, the melted interlayer removes contaminations from the joining
surfaces of the base metals. Then the liquid filler is discharged from the joining interface by the joining
pressure, and forms fillets at the gaps around the joint. In this stage, the joining pressure is relatively small, so
the welding deformation can be restrained to a minimum. The fillets have the effects both on relaxing the stress
concentration at the joint and on increasing the joining area, which contribute to the strengthening of the joint.
Thus, the high quality pipe joining without the dispersion in joint properties due to welder’s skill can be
performed. In this report, the concept and merits of BPW are explained, and the results of the investigation on
the cleaning effect of the interlayer metal and the effects of fillet formation on strengthening the joint are
discussed. The practical application of BPW in Japan is also introduced.
Abstract: Resistance spot welds (RSW) have been widely used in the sheet metal joining process due
to high productivity, low cost and convenience. The application of aluminum alloys in automobile
manufacturing has resulted in the reduction of weight in vehicle, fuel economy and improvement of
drivability and driving performance. Therefore, the resistance spot weld (RSW) process has attracted
attention to fabrication of aluminum structures. However, applications of Al RSW are limited due to
the unreliable durability of the weld-bonded joints. This study presents an experimental investigation
on the use of a post-weld cold working process to improve the fatigue strength of Al RSW. The
post-weld cold working process includes a pair of uniquely shaped indenters that are pressed or driven
into the structure in order to induce the compressive residual stresses around the RSW. The
mechanical properties of the post-weld cold worked Al RSW were investigated, including the
experimental results of fatigue. The effect of the post-weld cold working process parameters on the
fatigue strength of the Al RSW was also investigated. Comparisons of the mechanical properties and
qualitative results between the as-welded RSW specimens and the post-weld cold worked RSW
specimens of each post-cold working parameter have been carried out. Also, discussions on the
experimental results using the finite element method (FEM) for the post-weld cold working
parameters are performed.
Abstract: The characteristics of Nd:YAG laser welded 600MPa grade TRIP(transformation induced
plasticity) and DP(dual phase) steels with respect to hardness, microstructures, mechanical
properties and formability was investigated. A shielding gas was not used, and bead-on-plate
welding was performed using various welding speeds at a power of 3.5kW.
In the case of TRIP steel, the hardness was the highest at the fusion zone(FZ) and HAZ near the FZ
and decreased as the base metal was approached. The maximum hardness increased with increasing
welding speed to 3.6m/min and then remained. The microstructures of FZ and HAZ near the FZ
consisted of ferrite and bainite for all welding speeds.
In the case of DP steel, the maximum hardness was obtained at the HAZ near the FZ. It increased
rapidly to 2.1m/min and then showed nearly the same value. The difference between the maximum
hardness of HAZ and that of FZ increased with decreasing welding speed. The microstructure of FZ
was composed of acicular ferrite but the HAZ near the FZ contained bainite and ferrite at a low
Both steels had similar tensile properties and formabilities. In a perpendicular tensile test to the
weld line, all specimens were fractured at the base metal, and the strengths were somewhat higher
than those of raw metals. In a parallel tensile test, the strengths of the joints were higher than those
of raw materials but the elongations were lower. Formability was determined to be approximately
80% as compared with raw material at the optimum conditions.
Differences in hardness near the welded zone was dependant on the relative contents of ferrite.
Abstract: In Gas shielded Metal Arc Welding process, the molten drop at the electrode wire tip is
detached and transferred into the weld pool by various driving forces, which have been discussed
mainly focusing on gravity force, electro-magnetic force, surface tension force and plasma drag
force. In this paper the oscillation phenomena of metal drop and their numerical model are
described. The numerical model developed is an axial symmetrical 2D model which enables to
calculate and visualize time-change of the drop shape and the flow in the drop using VOF-CSF
method. The validity of the model is verified through the comparison between calculations and
experiments using waterdrop. It is shown that the natural frequency of the pendant drop decreases
with increase of the drop size. And the numerical simulation predicts that it is possible to detach
the molten drop from the electrode wire by exciting the forced oscillation around the natural
frequency with pulsed current.
Abstract: Super duplex stainless steels were welded using new flash butt welding technology of
temperature controlling system. The super duplex stainless steel (329J4L) and conventional duplex
stainless steel (329J3L) were used. The samples were mounted in the dies using a Gleeble thermal
simulator and flash but welding was made. The specimens were heated up to 1373K for 10sec,
20sec and 30sec. Flash butt welding has consisting of a two stage processes of a flash action and a
contact resistance. First stage was a flash welding process and second stage was a solid state
bonding process. The cross sectional microstructure of the weld bond region showed two types of a
deposited fine particles region and a solid state bonding region. The grain growth was hardly
observed in the weld region and the heat-affected zone. For further increasing joining efficiency of
solid state bonding at the second stage, the welding time at 1373K was increased from 5 sec to
180sec. The bonding area increased with increasing welding time at 1373K and successfully welded
for conventional duplex stainless steel.
Abstract: There is an ongoing drive to reduce the operating costs of aero-engines and this may be
achieved partially via an increase in engine efficiency. To achieve this, industry needs to utilise new
materials that can withstand higher operating temperatures and stresses. Many of the nickel-based
alloys suitable for these applications, eg MAR-M-002, are difficult to join using conventional
welding techniques. This paper describes a technique used to successfully weld 2.5 mm thick plates
of cast MAR-M-002. The technique used FEA modelling to analyse stresses during welding and
multiple axis electron beam deflection to alter the temperature and stress distribution around the
fusion zone to prevent the initiation or propagation of cracks. FEA modelling of the process has
been used to reduce the total number of practical tests, and hence, to conserve the limited material
supply. This technique has made it possible to produce crack free welds in what is usually classed
as an 'impossible to weld' alloy.
Abstract: Laser welding is a well known process, so is GMAW. But the joining of the processes,
the so called laser hybrid welding is not that known, yet. Looking into the laser welding we realise,
after many years use that there are some limitations to the process. One of the most significant is
that the process deals poorly with the ability to bridge gaps between plates that are to be joined.
This has its drawbacks on welding economy, the tolerances on ingoing parts has to be very high, the
laser process can not tolerate more than 0,1 mm gap between the plates. The GMAW process on the
other hand has the ability to deal with the joint tolerances in a better way, the backside is of course
the productivity and the penetration properties. In the laser hybrid process where the two processes
are joined in the same welding head, we are experienceing a great improvement in several
properties. Gaps are no longer a big problem, the process can deal with gaps up to 2,0 mm with the
present technology, (it is possible to coop with larger gaps using an oscillation of the laser beam,
but this is only on experimental stage yet). This now means that costs for ingoing parts will be
reduced. Process stability at high welding speeds is acchived.
There are many advantages in high strenght steels that are sensitive to heat input; better mechanical
properties are possible to obtain. Looking at the stainless materials the process has many
advantages, one of the most important is the joint volume reduction in thicker materials, another is
the ability to weld in duplex stainless steels.
Abstract: Monte Carlo (MC) and finite difference (FD) hybrid method is applied to numerically
model the growth of austenite grains caused by welding thermal cycle in the heat affected zone
(HAZ) of steel welds. The grain growth behaviors and pinning effects by dispersed particles are
modeled by MC method while steep changes in temperatures with time and over space are by FD
method. The connection of the two methods is made possible by correlating MC step to the real
time through the grain growth theory. The model results are in a good agreement with experiments
as well as previous experimental results published, and it is indicated that the developed model can
be used to obtain a better understanding of the austenite grain structure development in HAZ and
even to improve the grain refinement technology using dispersed particles.