Flash butt welding-flashing, Mechanical Engineering

Assignment Help:

Flash Butt Welding-Flashing

The phenomenon of flashing is of extreme importance in achieving satisfactory welds. Flashing can begin only after a molten bridge has been formed somewhere along the interface. If the parts fit accurately, difficulty in initiating the process may be experienced and it may be necessary to level the butting surfaces to give local contact. This procedure is much different from that for resistance pressure welding where a good fit is desirable to exclude the atmosphere and prevent surface contamination. In the flash welding, surface contamination is removed in the spatter during flashing and molten metal is expelled in the final upset or forging operation.

Once a molten bridge has been formed it is set in motion over the interface by the electrodynamic forces resulting from the distortion of the current path through the work pieces. While it traverses over interface at a speed of 10 cm / s, more heat is generated in the bridge by the joule effect and is lost to the colder metal at each end. Assuming the bridge does not freeze, it will be broken in one of two ways. It may either explode because of the combined influence of overheating and the pinch effect or it may race to the edge of the work piece where it becomes extended in the form of an arc between the work faces until it ruptures. In either event, much of the metal contained in the bridge is propelled out of the joint as spatter.

Because, there is inevitably considerable inductance in the secondary circuit, collapsing of the electrical field at rupture results in a voltage surge which is capable to initiate an arc, although the open circuit voltage cannot sustain it and it is rapidly extinguished.

The Considerable heat is generated in these brief arcing periods which accounts for the efficiency of the process compared with resistance butt welding.


Related Discussions:- Flash butt welding-flashing

Thyristor fundamentals of electricity , Thyristor: The thyristor is just l...

Thyristor: The thyristor is just like an ordinary diode. Thyristor

Find out the recoil-velocity of the gun, Find out the recoil-velocity of th...

Find out the recoil-velocity of the gun: As shell of mass 200 gm is fired at a velocity of 50 metres/second by a gun of mass 20 kg. Find out the recoil-velocity of the gun.

Explain the intensive properties of a system, Explain the Intensive Propert...

Explain the Intensive Properties of a System Intensive properties are those, which have similar value for any part of the system or the properties which are independent of the

Components of steam power plant, Component s of Steam Power Plant: Th...

Component s of Steam Power Plant: There are four components of steam power plant: 1. The boiler: Hot-source reservoir in which the combustion gases raise steam. 2. Engi

Derive a regression forecasting equation, Derive a regression forecasting e...

Derive a regression forecasting equation: The general manager of a company producing road rollers is convinced that the demand for road rollers is associated to the number of

Cutting technology., can you explain about merchant circle,cutting forces

can you explain about merchant circle,cutting forces

Leaf spring, weight of leaf spring in bus

weight of leaf spring in bus

3 Games in Supply Chain, I have three assignment in Supply Chain Engineerin...

I have three assignment in Supply Chain Engineering. It is a Games assignment in: 1- Beer Game 2000 words. 2- Risk Pooling Game, Object of this game is to rewrite properly correct

Washing and drying a motorcycle, Washing and Drying a Motorcycle :  It is ...

Washing and Drying a Motorcycle :  It is important to wash and dry the motorcycle before servicing. It would ensure cleanliness during the service and would not allow any dust ent

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd