7/29/2019 6713 Welding Abstracts http://slidepdf.com/reader/full/6713-welding-abstracts 1/59 Opening Session Chairmen: E. Belinco OPENING ADDRESS , “ 2010 " Good Morning: I am proud to announce that the “Welding and Joining 2010 Conference” is formally open Ladies and Gentlemen, It is a great pleasure and privilege for me to welcome such a great community of people involved in welding to the Welding and Joining 2010 Conference in Tel-Aviv. Welding technologists are involved in research and development, production, construction, and inspection functions connected with welded products. The complexity of welding is readily apparent when one considers that fusion welding involves temperature gradients of thousands of degrees, over distances of less than a centimeter occurring on a time scale of seconds, involving multiple phases of solids, liquids gases and plasma. It is only the true technologist who is willing to deal with a process of such complexity in order to achieve the end result of a fabricated product of commercial usefulness, of high quality, safety, and affordable cost. Reports and analyses conducted by ASME, ASM and other leading organizations point to the many changes affecting the technical professions. One main change is the migration of jobs to high-tech fields of engineering, biotechnology and environmental science and nanotechnology. Since technology and joining go hand-in-hand, this change has profound implications for welding scientists and engineers. Its output is a visible trend from conventional arc welding to computerized systems, high-energy joining and solid-state bonding, from metals to materials
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Department of Metallurgical and Materials Engineering
Colorado School of Mines
Golden, Colorado 80401, U.S.A.
Abstract
Underwater wet welding offers significant cost savings over other repair techniques for
submerged structures such as petroleum production platforms, ships, piers, and other maritime
structures. Due to the deleterious effect of the water environment and increased pressure on
weld quality, underwater wet welds are generally plagued with defects. Innovative approaches
that include tailored consumable design and advanced welding process control need to be
developed to quality wet welds at greater depths. Several fundamental approaches adopted to
enhance the characteristics and performance of shielded metal arc (SMA) electrodes for wet
welding of steel structures will be discussed in the presentation. Weld pool deoxidation,
inclusion population control, porosity mitigation, and exothermic reactions are some of the
selected methodologies. A delicate balance between deoxidizers and alloying agents must be
developed to result in optimal weld metal composition. Manganese is added to the electrode
coating to replenish its loss from the weld pool. Additions of titanium and boron produce a
microstructure of 60 to 90 vol. pct. acicular ferrite, which was exceptional since typical wet
welds exhibit only around 10 vol. pct. of this microstructure. The resulting fine acicular ferrite
is less susceptible to cleavage fracture than the coarse primary ferrite, the predominant
microstructure in wet welds at greater depths. Being powerful deoxidizers, the additions of rare
earth metals produces further reduction in weld metal oxygen and increased the recovery of manganese, titanium, and boron in the weld metal by protecting them from oxidation. Nickel
additions to oxidizing and rutile grade electrodes result in increased impact toughness.
Weld porosity caused by both hydrogen and carbon monoxide at the level of 10 vol. pct. has
commonly been reported in wet welds but it can be reduced through electrode formulation
optimization. Past research results show hydrogen as the main culprit of pore formation. More
recent findings, however, are able to clarify the effects of carbon and metal transfer mode on
porosity (carbon monoxide formation). Careful control of the weld materials (electrode, flux,
base metal) and welding process control can significantly reduce the amount of porosity in the
Composite laser components made by diffusion bonding of similar or dissimilar crystalline laser
elements have proven to be useful for many applications in the area of solid state lasers. The
formation of stress-free and durable bonds by adhesive-free bonding technique is essential for
the obtainment of high optical quality elements, especially for high power applications.
Optical pumping of large laser rods in order to achieve very high power levels requires of
solving the thermal effects problems induced by the active cooling of the crystalline rod. One
possibility of how to decrease the thermal effects (such as thermal lensing and thermal stress-
induced birefringence) and to enhance the laser system performances is by using a laser rod with
two end-caps at both sides. Such composite laser rod enlarges the active material cooling surface
and improves laser active media thermal uniformity and heatsink.
Beside the above, there are plenty of more applications to which diffusion bonding of opticalelements can contribute. These include creating of large scale optical elements to achieve sizes
larger than the commercially available components, bonding of cladding layers on elongated
optical elements (such as laser rods or slabs), joining of two thin optical elements one on top of
the other in order to create passively Q-switched microchip solid-state laser devices, and more.
Another aspect associated with the operation of large active laser elements at the high power
regime is increasing their tensile strength. This is needed to avoid the fracture of laser element as
a result of the large thermal gradient induced at the element's surface by the active cooling. In
the course of the present study strengthening by a factor of 3-5 was achieved by thermo-
chemical treatment of commercial elements at acidic environment under controlled atmosphere.
These issues will be discussed in the present lecture.
The assembled tubes are inserted into the welding machine so that the electrodes can
load the flanged weld joint preparations (see Fig. 2). After the electrode loads are
applied, a welding current is passed between the electrodes through the parts being
welded.
Initial current can be relatively low (ramp-up) to provide low heating which
establishes the electrical contact and allows the mating parts to deform to complywith the electrode loading. This initial deformation phase forms an even contact
between the electrodes and mating parts, and prevents localized contact which can
lead to local overheating. Localized overheating can result in localized melting,
liquid metal expulsion, localized electrode wear, and other negative effects.
After the ramp-up current is applied and the electrodes and parts are “seated in”,
higher currents are applied to provide temperatures high enough for interfacial
welding. The welding current may cause interfacial melting for a fusion weldingapplication. If fusion temperatures are not obtained at the interface, the welding
current and electrode pressure can provide a combination of shear and upset
(reduction in thickness) deformation required for solid state welding. In both casesshear displacement and/or deformation is imposed on the welded interface by the
action of the compressing electrodes. Fusion welds may have liquid metal expelled
from the weld interface under such loading conditions.
After the welding current is terminated, an additional lower current can be applied for
additional heat treating of the weld, or the weld can simply be allowed to cool under pressure.
Electrodes are normally made out of copper alloy to provide high electrical and
thermal conductivity. The electrodes are usually water cooled to:
Prevent electrode overheating
Provide cooling between the electrodes and the parts being welded to prevent
electrode sticking Provide for cooling of the parts after welding
The combination of very high current density and high cooling rates imposed by thewater cooled copper electrodes results in very rapid heating and cooling. Welding
cycle times under these conditions can be very short, normally no longer than a few
seconds, and under special conditions, shorter than one second.
Creative use of current pulsing throughout the welding cycle can be used to provide
control of heating effects. In this example of folded tube to flanged tube welding,
the double thickness of metal in the folded tube will require more heat delivered tothe fold than that required to heat the flanged tube to the same temperature. A
constant welding current will tend to over-heat the flange and under-heat the fold, producing poor welds. Pulsing of the welding current can allow heat to flow into the
folded region during peak current, and provides cooling to the flange region between
current pulses. Thus pulsing can result in a more even temperature distribution in the
parts being welded.
A cross section of a typical folded tube to flanged tube weld is shown in Fig 3. The
welded region between the fold and the flange is clearly displayed. Also displayed isthe weld between the two sides of the fold, producing a solid welded transition
between the tubes.
Welding Materials
This section is intended as a general guideline for DRW of materials for a view of the
applicability of the process. Specific alloys are not discussed and may be subject to
special consideration. Discussions with the alloy vendor are appropriate in these cases.
Low carbon steel
Low carbon steel tube to low carbon steel tube DR welds can be welded over a relatively
broad range of variables. Low carbon steels are normally defined as 0.04 to 0.15% Cand without other alloying elements which may affect strength.
Coated steels
Galvanizing and / or galvannealing of steel parts may require modified variable selection, but in general does not significantly affect weldability. Other metallic coatings generally
should be weld-able, but non-metal coatings including polymers, silicones, solid
Fig 3, Folded tube to flanged tube weld cross section
Care should be taken in all DRW of coated materials and parts to continue to apply the
weld force during cooling to assure solidified coatings. This means that the “hold time”
in DRW, which is the time the force is maintained after the passage of weld current
ceases, may have to be increased beyond values used for welding bare materials.
2.1.3 Medium Carbon Steels
Medium carbon steels are normally defined as 0.15 to 0.30% C and without other
alloying elements which may affect strength. If the steel contains medium carbon, the
weld may need to be cooled slowly by increasing ramping down the welding current withtime. Alternatively, quench and temper methods may be used by re-heating the weld in
the welding machine after cooling the weld. Such procedures can generate a tempered
Martensite microstructure in the weld/heat affected zone of parts welded
2.1.4 Stainless Steels
Ferritic stainless steel to ferritic stainless steel are generally DRW weldable if the carboncontents are low. By their nature, these steels are not commonly used with any coating.
Austenitic stainless steel to austenitic stainless steel is also generally weldable.Increased “hold time”, the retention of the welding force after the current ceases, may be
required to avoid hot cracking during weld solidification for some austenitic stainless
steel alloys. .
It is necessary to remove any oxide scale from the surfaces of stainless steel in the weld
locations prior to DRW welding. Stainless steel oxide scale may be very stable during
welding, separating the welding interfaces and hindering the DWR process.
DRW of Aluminum alloys has not been demonstrated to any significant degree as yet.Aluminum oxide is extremely stable, and melts at temperatures well above aluminum
metal. Oxide layers present on the surface of the aluminum alloys is significant barrier
to bonding. In addition, hydrogen from any source (adhered moisture, dirt, thick hydroxide layers on the oxide) can cause porosity in any melted aluminum. Additionaldevelopment must be pursued before the DRW of aluminum alloys becomes an accepted
process.
2.1.6 Dissimilar metal welds
Dissimilar material DRW is also possible in many cases, but very few procedures have
been developed for specific metal combinations. The only combination successfullywelded so to date cast iron to steel using two different methods. Other combinations are
surely possible, but range in weld-ability from robust to poor.
corrosion, thermal stress due to differences in thermal expansion between the dissimilar
metals, and the resulting thermal fatigue must be considered carefully before such joints
can be made and deployed. Inter-layers of more compatible metal foils may be used to
avoid the formation poor interfacial structure.
Configurations and Applications
DRW is a very flexible, enabling welding process with capabilities of welding a broadrange of materials and configurations. Although the early development work has
concentrated on circular cross section tubes, flanges, and tube to flat configurations. An
example is the tube (folded end) to tube (side) seen in Figure 4. Other more complex
configurations have resulted in successful joints.
Figure 5 is a cross section of a gas storage device showing three different DRW weld
configurations. This device is in production, and a very large number of these devicesare in service (contact SpaceForm Welding Solutions for more information)
An Overview: The Israeli Certified Welding Inspector
ICWI) Program - 10 YEARS LATER
Shimon Addess, Chairman, the Examination and Qualification Committee - INWC
Abstract
In July 1997 the Israeli National Welding Committee (INWC) formulated a draft
procedure for the activities of its proposed Examination and Qualification Committee for
welding inspectors.
Today the Examination and Qualification Committee operates according to the rules set
out in the second edition of the “Quality Manual for the Qualification of Welding
Inspectors and Bodies Qualifying Welders”.
In May 1999 the INWC published its “Standard for NWC Certification of Welding
Inspectors” NWC-WI-1(5/1999) which later in March 2002 became the Israeli Standard
2213.
The first four welding inspectors were qualified in 1999, the year that the INWC became
an International section of the American Welding Society (AWS).
2004 saw the signing of a reciprocity agreement between the INWC and the AWS for mutual recognition of the certification of welding inspectors in the two countries.
Israel and Canada are the only two countries which have a reciprocal recognition
agreement with the USA.
The updated edition, NWC-WI-1(8/2008) is based on AWS QC1-2007 and AWS
B5.1:2003 but includes an additional oral exam which the INWC has had in its program
since the year 2000.
By May 2009 there were 56 Israeli Certified Welding Inspectors including one American
Micro- and macro- structural integrity changes in the material, flaw development are
accompanied by acoustic emission (AE). Functional relationship between parameters of
AE signals and the kinetic characteristics of such processes can be used for inspection,
diagnostics and assessment of structural integrity of high energy piping and equipment.For this purpose, the authors have created and continuously develop Quantitative
Acoustic Emission (QAE) Non-Destructive Inspection (NDI) technology that allows to:
Perform AE measurements of the entire piping system during operation under
strong variable background noise conditions.
Identify flaw related continuous and burst AE signals for reliable revealing and
location of micro and macro flaws while accurately filtering out flaw not related
AE signals produced by friction, knocks and vibration.
Identify flaw type including individual micro- cracking, system of micro- cracks
of different nature, fracturing and de-bonding of hard inclusions, local and mass
plastic deformation.
Detect indications of creep damage at stages 3, 4 and 5 in weld joints and base
material.
Assess flaw's danger level in terms of fracture mechanics criteria.
Perform a long term monitoring of flaw propagation providing important
information for predictive maintenance.
The created technology was successfully applied for inspection of more than 120
operating high energy piping systems. The findings of QAE NDI were confirmed by
different NDE methods and metallurgical investigations in multiple blind and verification
The Magnetic Pulse Welding (MPW) process, a cold solid state welding
process, is an industrial process, operating at several high volume
manufacturing facilities.
MPW is accomplished by the magnetically driven, high velocity, oblique
angle, impact of two metal surfaces. At impact, the surfaces (which will
always have some level of oxidation) are stripped off and ejected by the
closing angle of impact. The surfaces which are then metallurgically pure are
pressed into intimate contact by the magnetic pressure, allowing valence
electron sharing and atomic-level bonding. This process has been
demonstrated in the joining of tubular configurations of a variety of metals
and alloys[1] [2] [3]
. Product designers are frequently constrained by the
restrictions of traditional joining technologies, which place certain limitations
on the type of joint, the materials that can be joined and the quality of the joint. Solid state welding allows manufacturers to significantly improve their
product designs and production results by enabling both dissimilar and similar
materials to be welded together, thus providing the opportunity to use lighter
and stronger material combinations. Magnetic pulse welding is a fast, non-
contact and clean solid state welding process. A review of the main elements
of the process is presented here along with typical quality testing results and