Indian Welding Journal

C. Karthikeyan ¹, V. Anbazhagan ¹, K. G. K. Murti ¹, M. N. Chandrasekharaiah ¹, V. G. Jagannath ²

Affiliations
1 The Welding Research Institute, BHEL, Tiruchirapalli - 620 020, IN
2 The Welding Research Institute, BHEL, Tiruchirapalli - 620 020, IN

Abstract

Laser Matrial Processing technology has deeply penetrated into various industrial applications since 1966(1) when the first industrial CO₂ Laser was built. Since then the versatility and importance of Laser in material processing has been gaining recognition and acceptance with the result that many industries in the developed countries utilise Laser systems. This has encouraged further investigations into the improvement processing methods using Laser to overcome the presently confronted difficulties.

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C. Karthikeyan ¹, K. G. K. Murti ¹, V. Anbazhagan ¹

Affiliations
1 Welding Research Institute, BHEL, Tiruchirapalli - 14, IN

Abstract

Laser material processing technology has started taking deep ischolar_mains in our country and no more it is a mystery. Though the technology started penetrating in our country for nuclear applications, no doubt, it has deepened into other industrial sectors like defence, transport, electronics, space, energy, etc.

Welding Research Institute (WRI) has a 575 Watts capacity CO₂ Laser supplied by M/s. Coherent, USA. In WRI, the following laser material processing feasibility investigations were carried out for the applications of

• Laser welding of battery can hermetic sealing,

• Laser welding of stainless steel spindle assembly,

• Laser cutting of silicon wafers,

• Laser scribing of silicon steel transformer laminations, and

• Laser scribing of solar cells.

The details of the investigations are brought out in this paper, which will give more explanations about the advantages of Laser material processing compared to conventional material processing techniques. A comparison of performance between Laser and EBW is brought out in the paper for the benefit of the readers.

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K. Asokkumar ¹, C. S. Nizam ², V. R. Samuel ¹, K. G. K. Murti ¹, S. Manoharan ¹, P. Pughazhendi ², V. Ravindran ²

Affiliations
1 Welding Research Institute, BHEL, Trichy - 620 014, IN
2 Boiler plant of BHEL, Trichy - 620 014, IN

Abstract

Flash butt welding is used extensively for welding of steel for different applications ranging from rails to automobile wheels in our country. Although this process is widely used for past six decades, there is still apprehension in adaptation of this process in certain critical applications for want of proper reliable N.D.T. method or proper quality assurance method. The present work addresses this problem of reliable N.D.T. method by suggesting the adaptation of computer based parameter monitoring system for checking every production joint. The first part of the work discusses the development of a P.C. based weld monitoring system. The second part of the work discusses the evaluation of the performance of the developed monitoring system in the actual production environment by welding economiser tube joints.

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K. Asokkumar ¹, V. R. Samuel ¹, S. Manoharan ¹, K. G. K. Murti ¹

Affiliations
1 Welding Research Institute, BHEL, Tiruchirapalli, IN

Abstract

Resistance spot welding is being used extensively in the automobile electrical and consumer goods industries in our country. With high quality coupled with low cost demanded by many industries, it is important to adapt resistance welding controllers for assuring quality of spot welded joints. The present paper examines the dynamic resistance behaviour during resistance spot welding of low carbon steel and austenitic stainless steel with a view to study the applicability of dynamic resistance based controllers Low carbon steel sheet of 1 mm and austenitic stainless steel sheet of 0.5 mm were used for spot welding trials and tensile shear test is used for evaluation of joint quality. Nugget diameter and indentation were again measured. The details of instrumentation system for dynamic resistance measurement and method of computation are being discussed. Dynamic resistance values are computed for every weld trial and parameters such as current pressure and time are varied to study its influence on be: i dynamic resistance as well as tensile shear strength. It was found that there is good correlation between tensile shear load, nugget diameter and indentation with the percentage drop in dynamic resistance. This work suggests that the percentage drop in dynamic resistance can be used as criteria for ensuring the quality of the spot welded steel joints.

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A. Shanmugam ¹, A. Raja ¹, A. Santha Kumari ¹, K. l. Rohira ¹, K. G. K. Murti ¹

Affiliations
1 Welding Research Institute, BHEL, Tiruchirapalli - 620 014, IN

Abstract

The term “Process stability" refers to the dynamic behaviour of the welding arc. In MIG welding process it depends on number of factors like power source characteristics, shielding gas, welding conditions, mode of metal transfer and wire chemistry etc. However the influence of each of these factors on the process stability is reflected in the current and voltage waveform of the welding arc. Since the current and voltage signals of an arc welding process are stochastic signals by nature, it requires statistical signal theory for evaluating the process stability. Therefore the current and voltage signals are measured using high speed data acquisition system and analysed. This paper presents the results of the investigation carried out on the influence of shielding gas mixture on the process stability in solid wire MIG welding under short circuit and spray transfer conditions, using statistical approach.

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