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

Define maximum allowable working pressure, Q. Define Maximum Allowable Work...

Q. Define Maximum Allowable Working Pressure? The MAWP to be marked on the Section VIII nameplate is defined as the maximum gauge pressure permissible at the top of a completed

Design a shaft to transmit power, Design a shaft to transmit power from a m...

Design a shaft to transmit power from a motor to a lathe head stock through a pulley by means of a belt drive. The pulley weighs 200 N and is located at 300 mm from the centre of t

Explain conveyor and auger, Conveyor and auger Two Hydraulic motors are...

Conveyor and auger Two Hydraulic motors are provided for individual control of two conveyors and Auger, which are provided for individual control of material on both the sides

Evaluate the speed of train, Evaluate the speed of train: A train of ...

Evaluate the speed of train: A train of mass 200KN has frictional resistance of 5N per KN. Speed of train, at the top of an inclined of 1 in 80 is 45 Km/hr. Find speed of tra

Pressure at bottom of a cone, I have a tank that has a 30" dia at the top...

I have a tank that has a 30" dia at the top and is 24" deep. It connects to a cone that is 30" dia at the top and goes to a 15" dia in 12". I plan on filling the tank with golf ba

Estimate future capacity requirements, Estimate Future Capacity Requirement...

Estimate Future Capacity Requirements: An electronic packaging centre operates 250 days per year, with one eight hour shift. Management believes that a capacity cushion of 15

Radiative heat transfer, how to find view factor for a cylinder to humanbod...

how to find view factor for a cylinder to humanbody at a distance?

Inspection of tyres , Inspection of Tyres STEPS Both the tyres are...

Inspection of Tyres STEPS Both the tyres are checked for free rotation. Loose spokes are to be tightened. At the same time it is checked that the tyre is not dam

State of cad data exchange, State of CAD Data Exchange: "Are we closel...

State of CAD Data Exchange: "Are we closely there yet?" the dreaded question we hear wailing from the back of the car. "Yes, nearly there" is our cheerful response. We didn't

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