Workshop on Welding & Brazing in Pune & Chennai

TWO-DAY WORKSHOPS ON EMERGING LEARNING IN THIN SHEET JOINING RESISTANCE WELDING & MIG BRAZING

5 - 6 October 2015
FRONIUS INDIA TECHNOLOGY CENTER, CHAKAN, PUNE
9 - 10 October 2015
IC & SR AUDITORIUM, IIT MADRAS, CHENNAI

INTRODUCTION

The automotive industry is in a new era of greater to sustain its leadership and to sustain growth and capacity management. There is a need to adapt to the changing environment. As the market demands superior performance, higher speed, low fuel consumption, more comfort, more safety and improved aesthetics, designers are looking for new lighter materials with better weight to strength ratios with ease to fabricate. The automotive manufacturers have started to use thinner grades of various Advanced High Strength Steel (AHSS), Ultra High Strength Steel (UHSS) grades, Dual Phase (DP) steels, TRIP (Transformation Induced Plasticity) steel and so on. HSLA (High Strength Low Alloy) steel offers a combination of high strength and good weldability.
Besides, changes in the auto body structure design are also promising; typical examples of such promising measures are the use of tailored blank (TB) and hydro-forming (HF) components. As these efforts advance, the hurdles that welding has to overcome are increasingly higher and new technologies for joining them are being developed. Both car weight reduction and enhanced collision safety can only be achieved through improved reliability of weld joints, by optimising the chemistry and metallographic structure of high strength sheets and developing new welding processes (power supply and work methods). Welding methods for automotive industry must be able to achieve high production rates, provide superior quality weldments, be easily mechanised with short set-up times, have the flexibility to accommodate design changes and maintain acceptable working environment standards. The excellent physical material characteristics of these latest generation steels are derived from heat treatment processes. It follows that the steels are more easily affected by heat, hence they cannot be readily MIG welded, and spot welding is possible. Hence, Resistance welding and MIG brazing are gaining momentum as candidate processes for joining thin sheets. The trends in welding technology both in the existing and new processes that are gaining entry into production of automotive industry are to be taken to production shops for achieving sustained quality and enhanced productivity, especially in the context of India, where almost all automotive manufacturers in the world have set their base. The workshop is intended to serve this purpose of taking the technologies to the shop floors effectively.

RESISTANCE WELDING
Almost all variants of Resistance Welding (RW) processes are widely used in the high-volume manufacture of sheet metal products and the automotive industry has relied on RW as a principal joining method for many decades. A typical car contains at least 2000 to 3000 Resistance Spot Welds (RSW). The advantages of RSW in high volume automotive manufacturing include less expense (per-weld cost), speedy process (< 1 second per weld), easy automation (flexible process), no per-weld consumables (i.e. no issues of piece-cost, inventory, additional weight or recycling difficulties) and low training costs (as in manual operations).
In the recent past, a host of developments are taking place in the RW processes viz., MFDC, Robotic RW, Deformation RW, Modified Projection Welding, to name a few. The use of robotic spot welding is increasingly being used in automotive industry extensively. The speed, precision, efficiency, and the resulting cost reductions afforded by automated resistance spot welding are well documented and accepted, particularly in the automotive industry. However, industry requires that even the most mature solutions continue to evolve. Robotic welding plays a key role in enabling car companies to keep pace with demand for new, more technologically advanced, higher quality products. Automakers are looking for robots with greater repeatability and weld requirements down to ± 2 mm.
As the demands on spot welding applications increase during the manufacture of automobiles, end-users exploring all of the new technologies to help make better products for their customers. Advancements in both AC and DC (inverter-type) weld controllers and the coming of servo gun technology will all help expand welding applications for difficult materials, such as thin or exotic metals. These new technologies are much more capable of dealing with those materials.
The use of single-source control for multiple robots is also emerging. Capabilities have been developed to control up to four robots from a single controller and teach pendant. This lets the robots work closely together without concerns about them colliding. It also provides a safer work environment with all robots under the sole control of a single pendant.
The concept of using a robot to manipulate parts for pedestal-type welding machines has been widely used by many of the Japanese automotive parts suppliers. Once a part is tack welded in a fixture, it can be "passed" between stations by multiple robots.
Resistance spot welding systems which are based on medium-frequency inverters are recently gaining in importance and are being used for welding of steel sheets. The energy can be effectively utilized for spot welds at lower current levels with desired nugget size in Medium Frequency Direct Current (MFDC). With the established parameters for weld lobe, current is the most influencing factor in achieving the wider welding window in MFDC. In general, MFDC process saves 20% of the total energy. MFDC can be the adaptive welding technology for welding of thin sheets in RSW process. Medium Frequency Direct Current (MFDC) technique offers automatic load distribution in which 3 phase current drawn from the capacitor that are used in the system and also from the mains, thus reducing the peak current.

GMA BRAZE WELDING
Welding Processes of GI sheet Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. In addition to melting the base metal, a filler material is often added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that can be as strong as the base material. Pressure may also be used in conjunction with heat, or by itself, to produce a weld.
Welding of galvanized steel is done almost exactly the same way as welding of the bare steel of the same composition; the same welding processes, volts, amps, travel speed, etc. can be used with little modification when the switch is made from uncoated steel to galvanized steel - unless the zinc coating is unusually thick.

An extension of the GMA process, GMA braze welding utilises a filler metal with a lower melting point than the parent metal. The joint relies neither on capillary action nor on intentional melting of the parent metal. Shielding gases of argon / oxygen type are the most suitable, the low oxygen level being sufficient to permit excellent edge wash and a flat weld without causing surface oxidation. The low heat input minimises damage to the coating on the underside of the parent plate, enables the corrosion resistant bronze filler to cover any of the coating damaged by the arc, and minimises the level of distortion when welding sheet metal components. Finishing costs of sheet metal components such as automotive panels can therefore be reduced substantially.
Cold Metal Transfer (CMT) is a welding process developed by Fronius Welding, Austria. The process is based upon conventional Dip Transfer MIG welding where material deposition is initiated at the point of short circuit of the wire electrode into the molten weld pool. However, whereas traditional welding processes are controlled electrically CMT employs an innovative wire feed system, integrated to a high speed digital control which controls material transfer and the amount of thermal input to the work piece.
CMT is characterised by an arcing period during which both the work surface and the wire electrode are heated. The molten electrode is then fed forward to make contact with the work surface. At the point of short circuit the welding current is cut practically extinguishing the welding arc and hence limiting the amount of heat transferred to the work piece. After a defined short circuit duration the electrode is mechanically retracted pinching the molten droplet from the end of the electrode. The arc is then re - ignited and the process repeats. This hot cold, arc on arc off cycle is repeated up to 70 times per second depending on welding parameters employed. When compared to conventional MIG welding processes, CMT exhibits a high wire melting coefficient requiring in the region of 20 – 30% less thermal energy for welding. Although suited to a range of welding applications, notably thin aluminium, when considering arc brazing the process offers single sided access, with reduced part distortion - due to low thermal input, minimal weld spatter - greatly reducing the requirement for rework, and good gap bridging capabilities.

REWEEL 15
WELDING RESEARCH INSTITUTE (WRI), Bharat Heavy Electricals Limited (BHEL), and INDIAN WELDING SOCIETY (IWS) are jointly organising this series of two-day Workshops on “RESISTANCE WELDING – EMERGING LEARNING” (REWEEL 15) with the theme Emerging Learning in Thin Sheet Joining – Resistance Welding and MIG Brazing at Pune and Chennai.
REWEEL 15 is organised with the support of The Indian Institute of Technology Madras, Chennai and the Dr. D. Y. Patil Institute of Engineering & Technology (DYPIET), Pune.
REWEEL will deliberate on the recent trends in resistance welding processes and the MIG Brazing. Thanks to the support of DVS, German Welding Society, and faculty supported by the German Welding Institute, GSI SLV Duisburg, Germany, and expert from Fronius, Austria, the first workshop in this series will be held at Pune on 5-6 October 2015 and the second at Chennai during 9-10 October 2015.
Mr. Stefan Schreiber, Deputy Head of Department of Materials and Process Engineering, GSI SLV Duisburg, Germany, will be the key speaker of the workshop. The lectures during the workshop will provide full coverage of all important topics on materials, welding equipment, innovations and the latest industrial applications in resistance welding. The topics will also cover the recent developments in resistance welding with special emphasis on adaptive control technologies and applications for welding of challenging materials e.g. aluminium alloys and advanced high strength steels etc., as well as new achievements on inspection of weld quality. There would be a session from the leading experts in the Indian industry.
Fronius, Austria have agreed to join in with their automotive welding expert to deliver lecture on MIG Brazing and its advancements and some of the best practices being employed by the Automotive Sector in Europe.

There will be a session on Q&A on issues faced by industry in resistance welding and also on MIG Brazing. The participants are requested to send the issues to be discussed well in advance along with the registration forms to the organisers.

PROFILE OF THE KEY SPEAKER
Mr. Stefan Schreiber is from GSI SLV Duisburg, Germany, which is the largest of the ten training and educational institutes for welding engineering in Germany; and one of the largest and most important welding engineering institute in the whole of Europe. They have about 215 employees, including 31 engineers.
SLV Duisburg works on Education and examination, quality assurance, construction surveillance, manufacture qualification, destructive and non-destructive testing and research. In Duisburg, about 200 people can be trained practically. They have about 600 seats in their 16 lecture rooms in Essen, Gelsenkirchen, Kamen-Heeren-Weve, Oberhausen, Wesel and Wuppertal.
The Resistance Welding Facilities (3 labs with about 50 different machines) and expertise at SLV Duisburg includes Spot Welding (RSW), Projection Welding, Roller Seam Welding, Pressure Butt Welding, Flash Butt Welding, and associated processes such as Stud Welding and Mechanical Joining Processes (Clinch, Tox,...). Automotive industry personnel from all major OEMs, such as Audi, Volkswagen, Mercedes Benz, Porsche and their suppliers are regularly trained and certified through one or three week resistance welding trainings in SLV Duisburg, Germany. It is actively associated with optimization of resistance welding equipment, quality standards and evaluation of resistance welding controllers and machinery from all over the world. This is where SLV Duisburg plays a nodal role.

ADDRESS FOR CORRESPONDENCE:
INDIAN WELDING SOCIETY
Institutions Building (Near Kailasapuam Club)
BHEL Township
Tiruchirappalli – 620 014
Tamil Nadu, India
Phone: + 91-431- 2551847, 257 2988, 257 2702
E mail: hqiwsindia@gmail.com