Flash butt welding-flashing, Mechanical Engineering

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.

Posted Date: 9/17/2012 3:56:23 AM | Location : United States







Related Discussions:- Flash butt welding-flashing, Assignment Help, Ask Question on Flash butt welding-flashing, Get Answer, Expert's Help, Flash butt welding-flashing Discussions

Write discussion on Flash butt welding-flashing
Your posts are moderated
Related Questions
V iolatio n of K-P Statement: A HE produce work 'W' by exchanging the heat with one reservoir at temp. T 1 only. The K-P statement is violated.   H.P. is extract

Di fferentiate between strength of material and engineering mechanics Sol.: Three primary areas of mechanics of solids are statics, dynamics and the strength of materials.

Illustrate Newton's law of viscosity. Explain the importance of viscosity in fluid motion. Describe the effects of temperature on viscosity of water and that of air? Discuss hyd

What is entropy microscopically

Various applications of numerical methods in the field of m=numerical engineering.

Calculate the displacement of a particle: The displacement of a particle is given by the equation, x = 10 t 3  - 7 t 2   + 6 t + 2       I.            Calculate its d


hi i have an assignment in control system can u do it ?

(a) Illustrate with examples the different types of constrained motions ? (b) Describe in detail the following Mechanism : (i) Single slider crank chain mechanism (ii) Fou

Assets Markets and the LM Curve The assets markets are the markets in which money, bonds, stocks, houses and other forms of wealth are traded. There are a large variety of asse