September 23rd, 2009
Duplex stainless steel was first created in order to address corrosion problems stemming from chloride bearing cooling waters or other chemical process fluids.
Duplex stainless steel is a family of grades which are ranged in accordance to their corrosion performance, as well as their content of alloy; Duplex’s alloy content being almost equal proportions of ferrite and austenite.
Super Duplex was a term phrased in order to indicate its highly alloyed composition of which provides a pitting resistance of >40. The chemical composition is based on Cr% + 3.3Mo% + 16N%.
Super Duplex contains very high levels of chromium which provides above average resistance to acids, caustic solutions and acid chlorides. It also provides high levels of corrosion resistance to any environment which uses chemicals or petrochemical solutions. It is fast replacing 300 series stainless steel or high nickel super-austenitic steels.
Based on a chemical composition which has high contents of nickel, chromium and molybdenum, Super Duplex improves intergranular and pitting corrosion resistance. With the addition of nitrogen to promote structural hardening it not only raises yield strength but also strength values without impairing its toughness.
The Various Alloys
Super Duplex stainless steel resides in the group of Duplex stainless steel. It is graded for its corrosion performance and for its content of alloy. Duplex can be divided into four groups:
1. Super Duplex, which contains 25-26Cr and increased Mo and N. This grade is comparable to 25 Cr and 2507
2. Lean Duplex stainless steel such a 2304 which contains no added Mo
3. 2205, which is a grade considered the work horse as it accounts for over 80% duplex use
4. 25 Cr duplex.
All of these materials are available from us here at Chemipetro.
Tags: Duplex, duplex alloys, duplex stainless steel, Super Duplex
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September 17th, 2009
The two phase microstructure led to the name Duplex. The microstructure consists of grains of ferritic and austenitic stainless steels. When Duplex stainless steel melts it hardens from this liquid phase into a completely ferritic structure. As it cools to room temperature approximately half of these ferritic grains change into austenitic grains. The result is that Duplex stainless steel contains about half of each material, ferrite and austenite.
This Duplex structure gives this particular family of stainless steel its much applauded properties. For one it provides about twice the strength of regular ferritic or austenitic stainless steels. Duplex stainless steels also provide much higher levels of toughness and ductility over ferritic grades. They don’t, however, match these superior properties provided in austenitic grades of stainless steel.
Superior Qualities
While all stainless steels offer resistance to corrosion, the levels depend on their individual compositions. If chloride pitting or crevice resistance is required then they must contain in their composition a mixture of chromium, molybdenum and nitrogen. Duplex stainless steel has corrosion resistance levels that are similar to austenitic stainless steels. For instance from types 304 or 316 grades to 6% molybdenum stainless steels.
Duplex grades have excellent resistance to stress corrosion cracking. This is a property that has been inherited from their ferritic makeup. While austenitic stainless steels provide superior corrosion resistance, ferritic stainless steel provides superior stress cracking resistance.
Due to the lower nickel and molybdenum composition, Duplex stainless steels can be lower in cost. Apart from this and due to their yield strength, it is often possible to reduce the thickness. The combination of these two factors offers not only cost savings, but also savings in relation to weight – especially when compared to austenitic stainless steels.
Duplex stainless steel can be found here at Chemipetro, one of the UK’s leading manufacturers of pipe fittings and flanges, for reasonable prices.
Tags: austenitic stainless steels, Duplex, duplex alloys, duplex stainless steel, ferritic stainless steel
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September 15th, 2009
The principle behind flanges is that mechanical force needs to be exerted in order to preload the gasket. The mechanical force is usually provided by bolts. The reason for this is that when internal pressure is applied, the flange – in conjunction with a gasket – is able to maintain a seal.
They allow for two pipes to be mechanically connected to one another. They also allow for a pipe to be mechanically connected to a host of other equipment such as a valve or tee fitting. A flange however needs to be first attached or connected to the pipe through either welding or threading. They can be used either internally or externally for strength. Their use allows for the easy assembly or disassembly of pipes.
Flanges are sized according to their nominal bore size, which for most pipes does not represent their actual outside or inside diameters. For instance a pipe with a nominal diameter of say 1 inch is not indicative of the size of the pipe. In this instance the outside diameter would be 1.315 inches. The inside diameter of any pipe is determined by the thickness of its wall. For this reason it is imperative that manufacture of all and any pipe flanges is matched to the piece of the bore size of the matching pipe.
Industry Standards
The manufacture of flanges is subject to various industry standards, all of which are adhered to by us here at Chemipetro; a reputable, leading supplier worldwide of pipe fittings and flanges.
One such standard is the NORSOK standard. This standard is intended to confirm or bear out the fact that a manufacturer has the experience, the qualifications and the necessary equipment and facilities to manufacture according to the acceptable properties of the materials being used. The materials in question are Duplex SS, high alloyed austenitic SS, Nickel based alloys and Titanium and its alloys.
Tags: Duplex, duplex alloys, Flanges, Pipe Flanges
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September 10th, 2009
In order to understand Duplex stainless steel, it is first necessary to understand the alloys which are present in it. These are Ferritic Alloys and Austenitic Alloys.
Austenitic Alloys are produced from a combination of both an iron solution and an alloy which when cooled, change into other mixtures; such as cementite and ferrite. At times – and to some extent – pearlite is also produced from the mixture. This is an alloy that is able to withstand corrosion and due to its cold working, provides far increased strength.
Austenitic alloys consist of two types of series, the first being the 200 series. The 200 series contains nickel, chromium and manganese while the second 300 series contains only chromium and nickel. Austenitic’s mechanical properties can be changed via the use of quenching, tempering or annealing.
Ferritic Alloys belong to the 400 series of stainless steel alloys. It is an alloy that is more popular than iron as it contains the same substances capable of producing cast iron and steel. Each is not hardened even when submitted to heat treatments or other solutions. Ferritic alloy is also resistant to corrosion due to its oxidation properties.
Duplex stainless steel is known for its corrosion resistant properties, which lends itself to both the construction and forming of flanges and pipe fittings.
Duplex stainless steel was introduced to the welding industry in the 90’s. Its primary focus lay in welding but since then its uses have been developed and expanded. Its properties were so well presented that fabricators and engineering specialists immediately saw its potential in construction uses.
Luckily, these materials are now available through us: leading flange supplier Chemipetro.
Tags: Duplex, duplex alloys, duplex stainless steel, Flanges, Pipe Fittings
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August 16th, 2009
When it comes to working with steel there are a number of problems that occur with the passing of time. Some of the more common ones are rust and corrosion. It is for this purpose that we have created Duplex alloys that are stronger and more durable than normal steels.
This means that you steel piping is protected from rust when used in water industries such as plumbing. We’ve designed our duplex alloys to be able to be used in industries where temperatures are high and ordinarily steel would buckle or warp.
We also offer a range of fittings that are constructed from duplex to ensure a linger lifespan of these fittings which means longer periods between maintenance and less wear and tear to those pieces.
Convenient delivery and shipping
We are very well positioned to ensure fast and efficient delivery to both local customers and customers abroad. Our ranges of products are of such a standard that we do have overseas customers requesting our products.
Our incredible range of duplex stainless steels are of superior strength and therefore offer much higher resistance to corrosion damage than ordinary stainless steel does. Go ahead and place your order today and we will get your order off to you in the shortest time possible depending on location.
Tags: Duplex, duplex alloys, duplex fittings
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