Introduction to Stainless Steels
It comes as a surprise to many that ‘stainless steel’ is not stainless. Discolouration is not uncommon and salt water environments in particular can give rise to corrosion: this is even noticeable at domestic level where dark spots appear caused by the mild salt solutions used during automatic dishwashing cycles.
The importance of stainless steel 1 is best reflected by the worldwide annual consumption which was reported at over 50 million tonnes in 2019. Generally recognised for its corrosion properties the material range is also widely used where strength coupled with elevated temperature resistance to oxidation.
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The Principal Arc Welding Processes
There are four basic welding processes that generate the heat necessary to melt metals by striking an electric arc between an electrode and a metal. Other arc processes are in use but have limited application or lack control and quality characteristics. Initially developed towards the end of the 19th century, arc welding quickly became a commercially important processes especially in the shipbuilding sector in the second world war.
An arc is a discharge of energy between two conductors at different voltages. In welding It can be initiated by bringing the conductors, an electrode and the metals to be joined, together momentarily to create a short circuit and then drawing them apart to produce a continuous arc. Experience is necessary so that the two components do not stick together. The arc can only be maintained over a very limited separation and with manual welding this relies on operator skill. Development over the past few decades has resulted in the production of sophisticated power supplies to help stabilise the arc.
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