Atramat® Standard Needles Martensitic Stainless Steel Examples: AISI 420 : Z 35 C14 AISI 420 F : Z 22 CD 13-1 Their general chemical composition is: CARBON : From 0,1 to 0,4 % CHROMIUM : From 11,5 to 14,5 % Some additional elements can be added to slightly modify the performance of the stainless steel. Sulphur provides an easier drillability and molybdenum increases the corrosion resistance. Thanks to their very good formability and drillability, the martensitic chromium stainless steels have been the most widely used in the market. This stainless steel family reaches its mechanical characteristics, and its corrosion resistance after heat treatment. The hardening process is obtained by heating and air quenching (quick cooling) the metal, followed by a tempering operation. After quenching : we obtain a martensitic microstructure. Heating Quenching KEY INFORMATION 1. The basic stainless steel of the market 2. Certainly the easiest machinability 3. Main drawback : The choice of parameters that balances the different performances (High Bending Resistance, Ductilty, Easy attaching, Good Corrosion Resistance) is very limited.* 6
Atramat® Premium Needles Austenitic Stainless Steel This the family of the AISI 300 Stainless steels, used in the Atramat® Premium range of needles. This family of steels is used by MANI and ETHICON (for high quality sutures). Examples: AISI 304 : X5 Cr Ni 18-10 AISI 302 : X10 Cr Ni 18-8 Their general chemical composition is: CARBON : < 0.15 % NICKEL : From 6 to 13 % CHROMIUM : From 17 to 20 % Additional elements : Molybdenum, Copper, Manganese Due to their chemical composition, the structure of these stainless steel grades is fully austenitic at low and high temperatures. It is the austenitic structure that gives the ductile comportment of the needle. Thanks to the important chromium content, these steels have an excellent corrosion resistance. For example, they can be used in surgical implants. The mechanical resistance of the austenitic stainless steels is given by a strong cold working. During a strong cold working, the carbon atoms penetrate the austenic structure, creating a solid solution that strongly strengthens the wire. Cold working Soft austenite Harder austenite It is its specific structure that gives the 300 stainless steels their excellent mechanical performances for needle application. These performances are today the best on the market. The formability and the drillability of such stainless steels is really difficult, and need a specific process. To achieve the perfect adequacy between high tensile strength and ductility, a perfect knowledge of the raw material elaboration linked to the specific know-how of the needle manufacturer is required . The Atramat® Premium Needle bending resistance is improved by more than 40% compared to a classical 420F martensitic taper point needle, while maintaining an excellent ductility. KEY INFORMATION 1. The best steel on the market 2. Most difficult machinability 3. Main advantage: Combine high bending resistance with high ductility. 7
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