A Detailed Examination of Weldability Lobes for a Range of Zinc-Coated Steels

Gould, Jerry E.; Peterson, Warren

doi:10.4271/880279

Cited by 9 publications

(5 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar conclusions can be drawn from experimental results obtained when spot welding zinc coated steel, 18,27 which showed either very little change in the sheet/sheet resistance or extremely low values of resistance at this interface at all times during the welding process. However, as previously indicated in this review, most investigators consider that the interfacial resistances most probably play a significant role in the heat development during the welding process.…”

Section: Present Status Of Electrothermal Modellingsupporting

confidence: 81%

Review of resistance spot welding of steel sheets Part 1 Modelling and control of weld nugget formation

Williams¹,

Parker²

2004

International Materials Reviews

167

View full text Add to dashboard Cite

Resistance spot welding is the principal method of welding sheet steel products. In practice, the manufacture of welds of acceptable quality depends on the definition of optimum welding parameters and the implementation of suitable controls to ensure constant weld quality over a long production run. The ability to make a weld is best defined by a weldability lobe outlining the available manufacturing tolerances between minimum and maximum limits. Both two-and three-dimensional weldability lobes exist defined in terms of weld time, welding current and electrode force. Production variables influencing weld growth are discussed, particularly the effect of electrode diameter. The importance of welding machine characteristics relative to weld growth is highlighted. In particular, the rigidity of the machine coupled with the weight and frictional effects developed in the electrode head assembly are shown to be important factors influencing weld growth. Also important are the electrical characteristics of the machine, including transformer configuration current waveform and current 'off' time in the nonconducting part of the waveform. A reliable control philosophy is an essential requirement of any inprocess feedback system if high quality spot welds are to be produced in high volume. Various model simulations indicate that changes, with time, in electrode/sheet and sheet/sheet interfacial resistances control weld nugget formation and growth. The relative contributions of these resistances are discussed. Heat generation and temperature distribution in the weld are determined by the current and force distribution across these interfaces. One-, two-and three-dimensional models have been developed to describe the temperature distribution in the weld zone and weld nugget growth. These models have limited application due to inadequate input data to describe the transient conditions appertaining in the weld zone. Current waveform, inductance effects, and friction/rigidity of the electrode head assembly, are not considered. Neural networks and fuzzy logic control have shown promise in classifying weld quality into predetermined groupings. The way forward is to adopt a multidisciplinary approach, taking into account the various interactions between the thermal, electrical, mechanical and metallurgical phenomena developed during the welding process. Models describing these phenomena should be interlinked to simulate heat generation and growth in the weld zone. The resulting model could be coupled with experimentally developed trends to optimise inputs to a neural network, the output of which is used, through a fuzzy logic controller, to take appropriate corrective action to ensure the required weld quality. It is stressed that any mathematical simulation or control system must take into account changes that occur at the welding electrodes as a consequence of electrode wear. The latter are discussed in Part 2 of this review.

show abstract

Section: Present Status Of Electrothermal Modellingsupporting

confidence: 81%

Review of resistance spot welding of steel sheets Part 1 Modelling and control of weld nugget formation

Williams¹,

Parker²

2004

International Materials Reviews

167

View full text Add to dashboard Cite

show abstract

“…1 Abnormal process conditions in resistance spot welding Fig. 2 A typical weld lobe curve and its two response variables welds under certain conditions of other process parameters in an experiment matrix [19]. In this case, the welding current cannot be chosen independently as a ®xed-level factor shown in Fig.…”

Section: Design Of Experimentsmentioning

confidence: 99%

Resistance spot welding of aluminium and steel: A comparative experimental study

Cho

Hu²,

2003

Proceedings of the Institution of Mechanical Engineers, Part B:

View full text Add to dashboard Cite

Abnormal process conditions or faults exist in production. This paper investigates the effect of these abnormal conditions on the quality of resistance spot welding of selected steel and aluminium alloys and compares the results. Various process variables including abnormal process conditions are selected and analysed by using a two-stage, sliding-level experimental method. According to the experiment matrix, acceptable ranges of welding current in their lobe curves and corresponding button diameters are obtained. The effects of the factors and their levels on the welding current and button diameter are discussed and evaluated for both steel and aluminium welding. It is concluded that any abnormal process condition can decrease the width of suitable current ranges in the lobe curve. Among the abnormal process conditions, button diameter is greatly influenced by the electrode size in steel and the poor fit-up condition in aluminium. It is also shown that aluminium has a larger variance in button diameter, showing a less robust process in resistance spot welding.

show abstract

“…The resistive heat generated at the sheet/sheet interface results in localised melting that on solidification forms the weld nugget. Although the RSW of uncoated and even coated steel sheets is now well established, [1][2][3][4][5][6][7] the same has remained a challenge for aluminium alloys due to the rapid electrode wear to the extent that redressing of electrodes is needed only after a very few spots. In contrast, a few thousand spots with galvanised steels and even 10 000 spots with uncoated steel are possible without electrode redressing.…”

Section: Introductionmentioning

confidence: 99%

Minimising electrode wear in resistance spot welding of aluminium alloys

Patil

Tilak

Srivastava

et al. 2011

Science and Technology of Welding and Joining

View full text Add to dashboard Cite

Rapid electrode wear due to localised random alloying between copper and aluminium at high temperature is by far the greatest challenge for the resistance spot welding of aluminium alloys. An effective recourse would be to enhance the overall electrical conductivity along the electrode/ sheet interface to reduce the resistive heating of copper electrode and to prohibit direct contact between electrode and sheet during welding. We propose here the application of carbon black paste in fluidic form as a barrier along the electrode/sheet interface both for the enhancement of electrical conductivity and for the prohibition of direct electrode to sheet contact. Carbon black is chemically inert to both copper and aluminium and in fluidic form allows the enhancement of thermal and electrical conductance due to better conformability within a pressurised contact. The present experimental study has shown a significant enhancement in electrode life in the presence of the carbon black based barrier coating along the interface.

show abstract

A Detailed Examination of Weldability Lobes for a Range of Zinc-Coated Steels

Cited by 9 publications

References 2 publications

Review of resistance spot welding of steel sheets Part 1 Modelling and control of weld nugget formation

Review of resistance spot welding of steel sheets Part 1 Modelling and control of weld nugget formation

Resistance spot welding of aluminium and steel: A comparative experimental study

Minimising electrode wear in resistance spot welding of aluminium alloys

Contact Info

Product

Resources

About