It's probablty the alloying elements in the S.S, Stainless steel typically has high levels of chromium and nickel. These elements form stable oxides on the metal surface which protects the surface from rusting. When you cut with an oxy-acetylene torch, your are literally burning the iron in the steel with the extra oxygen you supply. The chromium and nickel are much more stable at high temps than iron (that's why jet engine alloys use a lot of chromium and nickel) and may be protecting the iron from making contact with the oxygen from the torch. No contact = no iron burning = no cutting.
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| The elements which gives stainless steel their desired properties produce oxides which reduce the operation to a slow melting away process when the conventional oxy-acetylene cutting equipment is used. By injecting a suitable flux directly into the stream of cutting oxygen before it enteres the torch, the obstructing oxides are removed. The chromium in stainless steel has a great affinity for oxygen, and will form a film of chromium oxide on the surface of the steel at a molecular level. The film itself is about 130 Angstroms in thickness, one Angstrom being one millionth of one centimetre. This is like a tall building being protected from the rain with a roof the thickness of one sheet of ordinary copy paper. This layer is described as passive, tenacious and self-renewing. Passive means that it does not react with or influence other materials; tenacious means that it clings to the layer of steel and is not transferred elsewhere; self-renewing means that if damaged or forcibly removed, more chromium from the steel will be exposed to the air and form more chromium oxide. So, even if a stainless steel object withers away by use and reuse, it will still remain stainless. In powder cutting, iron powder is introduced into a standard oxy-acetylene cutting torch flame. The heat of combustion of the iron powder increases the total heat of the flame. Referring to the statement about chromium oxide above, by introducing iron powder into the flame, these oxides are kept from forming, and the cut is able to occur. The high iron content particles, oxidize at the torch tip, producing a very high temperature and concentrated heat. The powder also produces a reducing action on the metal, and a high velocity gouging action. When cutting non-ferrous metal like aluminum or copper, about 10-30 percent aluminum powder can be added to the iron powder. According to my source, special powder cutting torches are available for this purpose. A couple of ways to cut thick stainless is with a plasma torch as it produces massive heat to flush away stainless particles with ease, or with the use of the fiberglas reinforced cut-off wheels.
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On Wed, Jul 28, 2010 at 4:27 PM, SANKET SINGH <sanket.singh71@googlemail.com> wrote:
Dear friend,While u cut SS material using a Oxyacetylene flame(gas cutting), the temperature generated during the process is not high enough to melt the Chromium oxide layer formed on the surface of the SS material, the melting point of chromium oxide = 2430 degree centigrade (approximately), to reach such a high temperature u have to give a very high input on a small area which is not possible by Gas Cutting, as large amount of heat is dissipated. Plasma Cutting Process has the ability to Deliver such a high heat input at a point, so that it can attain that temperature and hence it easily cuts SS.
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