Welding – Conceptual approach
Part - I
#01. What is welding?
Welding is the process of joining two metallic parts by application heat with or without pressure.
#02. What are different types of welding?
Basically there are two type of welding, first one is fusion welding and second one is pressure welding. Fusion welding is also known as non pressure welding.
#03. How fusion welding is classified?
Fusion welding is classified as electron beam welding, laser welding, brazing, soldering, braze weld, metal arc welding, carbon arc welding, submerged arc welding, inert gas welding, electro-slag welding, argon arc welding and tungsten arc welding.
#04. How pressure welding is classified?
Pressure welding is classified as forge welding, seam welding, spot welding, projection welding, butt welding, flash welding and percussion welding.
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#05. What are the types of electrodes?
Arc welding electrodes are basically divided into two parts bare electrodes and coated electrodes.
#06. Why we use direct current in case of Carbon arc welding?
We cannot use alternating current in carbon arc welding because we cannot maintain a fix polarity in case of ac current.
#07. In carbon arc welding, what happens if carbon content carried over to job?
If carbon content is carried over to job then resultant weld will be brittle and unsound.
#08. What is done to overcome problem mention in above question?
To overcome the problem, the carbon electrode is connected to the negative terminal and in this case, at electrode tip heat generated is less than at job so that carbon content is not carried over to job.
#09. What is the most common material to used in core of electrodes?
Mild steel is most commonly used material in core wire of electrodes.
#10. What are the metals and alloys other than mild steel to be used in core of electrodes?
The materials used in core of electrodes are low alloy steel, nickel steel, chromium molybdenum steel, and manganese molybdenum steel, nickel molybdenum vanadium steel, lead bronze etc.
@ Point to be noted: In case of mild steel electrodes only covering and flux varies whereas composition remains the same.
#11. How does covering is provided on the electrode?
The covering is provided by either dipping the electrode or extrusion.
#12. What is the function of Flux coating provided on the electrode?
The main function of flux coating provided on the electrode is to provide reducing atmosphere to prevent oxidation, help in slag formation, stabilizing arc and to provide necessary alloy metal to the weld metal.
#13. What are the common ingredients of a flux that helps in slag formation and metal refining?
The most common ingredients of a flux that helps in slag formation are asbestos, mica, silica, fluorspar, stealite, titanium dioxide, iron oxide, magnesium carbonate, calcium carbonate and different grades of alumina.
#14 Which ingredients are used as arc stabilizer?
Potassium silicate and potassium titanate are used as arc stabilizer. And helped by titanium dioxide, feltspar and mica.
#15. What are standard size of electrodes used in industrial applications?
The electrodes are commonly manufactured in standard lengths of 250,300,350 and 400 mm while standard sizes of electrodes are 1.6, 2, 3.2, 2.5, 4, 5, 6, 7, 8 and 9 mm.
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