AUSTENITIC STAINLESS DAMASCENE STEEL

Transcription

1 AUSTENITIC STAINLESS DAMASCENE STEEL Damasteel s austenitic stainless Damascene Steel is a mix between types 304L and 316L stainless steels which are variations of the 18 percent chromium 8 percent nickel austenitic alloy. These alloys can be considered for a wide variety of applications where one or more of the following properties are important: Resistance to corrosion Resistance to oxidation Easy of fabrication Excellent formability Each alloy represents a good combination of corrosion resistance and fabrication. This combination of properties is the reason for the extensive use of these alloys. These alloys are used in a variety of products for use in specific conditions. Some examples of their uses are in flatware cutlery, jewellery, watches and other applications where corrosion resistance and aesthetics are important. For more information and general information see reference 1. Chemical composition of Damasteel 95x,x (weight-%) of the two different alloys used. Grade Etch C Si Mn Cr Ni Mo Colour 316L < L Dark < Mechanical Properties Annealed Material (bar and plate), minimum values at 20 C of 95x,x Steel Grade Proof Strength Tensile Elongation Impact Value Rp0.2 MPa Rm1.0 MPa Strength Rm MPa A5 % KV J 95x,x

2 Physical Properties The physical properties for 304L and 316L are nearly the same. However, there is a minor difference in the density between the two grades. Data according to EN Density Kg/dm to 7.9 Modulus Of Elasticity GPa 200 Poissons Ratio 0.3 Thermal Conductivity W/m C 15 Heat Capacity J/kg C 500 Electrical Resistivity µωm 0.73 Corrosion Resistance The Cr-Ni and the Cr-Ni-Mo standard stainless steels have a versatile corrosion resistance and are therefore suitable for a wide range of applications. For a more detailed description of their corrosion resistance properties please refer to Sandvik Steel Corrosion Handbook, see reference 2. Fabrication Hot working Stainless steel has a higher, almost double deformation stress when hot worked at temperatures between 1160 to 950 C ( F) compared to normal low alloy carbon steels. Hand forging must therefore be performed on relatively small dimensions. A good control of the heating temperature is needed and an electric or gas fired furnace is recommended. Long heating times at temperatures above 850 C (1580 F) leads to scale formation. After the last forging step, a rapid cooling in air or water will prevent reduced corrosion resistance in the grain boundaries. Otherwise, a quench-annealing is recommended.

3 Heat treatment If the material has been cooled too slowly after a hot forming or a welding operation, quench annealing should be performed. Undesirable grain structures will then be dissolved and any residual stress or cold working will also be removed. Annealing temperature 1050 C (1820 C) followed by rapid cooling in water or air depending on thickness of material is recommended. Hardening These grades cannot be hardened by heat treatment. However, they can be hardened by cold working. Cold working Like the conventional austenitic stainless steels these grades can be formed and fabricated by a full range of cold working operations. The cold working ductility is good and any cold working operations will increase the strength and the hardness of the material. This has the advantage that a patterning step for example forging or coining can sometimes be performed in the cold condition. Welding Austenitic stainless steels, in general, have excellent weldability and they do not normally require post-weld heat treatment. The grade can be welded by a full range of conventional welding methods. For best result use a 316L filler metal to ensure the best results. Machining As with the conventional austenitic stainless steels, the austenitic damascene steel has some specific machinability properties. Low tensile strength but a strong work hardening Tendencies for buildup of material on the tool edge Tough and stringy chips can be prevented by using chip curler tools Heavier feeds and slower speeds are used for machining the austenitic materials than those used for carbon steels. This reduces the work hardening and the tool edge build-up. For general guidelines, see reference 3.

4 Grinding and Polishing Normal grinding and polishing procedures for austenitic stainless can be used also for the damascene steel. Grinding wheel recommendation: Silicon Carbide, 46 grit, soft, open density, ceramic bonded. (C46J6V) Speed: 35 m/sec Feed: mm/stroke Speed of the work piece may be 1/60 of the grinding speed. Abrasive Belt Grinding Application Belt type Mesh Speed (m/s) Lubrication Plate, Strip, Bar or Wire Rough Grinding Al 2 O Grease Fine Grinding Polishing Cutlery and Jewelry Fine grinding Polishing Etching Etching is done to develop the patterns on the finished piece. The best conditions for etching are good polished surfaces carefully degreased. The work piece is then dipped into the etching acid. After etching the piece must be carefully cleaned in water. When the desired effect has been achieved a final cleaning with brush, soap and water in order to eliminate any further etching caused by residual acid.

5 Etching Acid 1 1. Water 60% H 2 SO 4 40% Soap 2. Water 63% H2SO 4 30% HClO 4 7% 3. Water - HCl 80% HNO3 20% 4. Water 75% HCl 14% alcohol 11% Addition Fe(III)Cl 10g/l Cu(II)Cl 10g/l Approx. time (min) Etching Colour 316L 304 Dark Grey Black Deep relief Grey Black An increased temperature may be needed when using alternative 1 and 4 because they may react slowly. The second and the third alternatives give a heavier attack and deeper relief, but unhealthy gases are formed. The acids must be handled with care and ensure that the work place is well ventilated. If the surfaces still have oxides present from the heat treatment, pitting corrosion may occur. 1 H 2 SO 4 Sulfuric acid HClO 4 Perchloric acid HCl Hydrochloric acid Fe(III)Cl Iron(III) chloride, also called ferric chloride CU(II)Cl Copper(II) chloride

6 Products Damasteel has a standard production programme and the latest issue of this can be found at. The following products can be supplied, subject to capacity being available on mill production lead times. Hot rolled plate Bar Rod Billet Reference 1. Design guidelines for the selection and use of stainless steel, NiDi, Sandvik Steel Corrosion Handbook Stainless Steel, 1999 ISBN: Sandvik Coromant, Knowledge base, Information given in this datasheet may be subject to alterations without notice. Care has been taken to ensure that the contents of this publication are accurate but Damasteel and its affiliated companies to not accept responsibility for errors or for information which is found to be misleading. Suggestions for or descriptions of the end use or application of products or methods of working are for information only and Damasteel and its affiliated companies accept no liability in respect thereof. Before using products supplied or manufactured by the company the customer should satisfy themselves of their suitability.