Sandvik innovation: achieve required chemistry in single layer

April 11, 2014 11:34 am

Sandvik has done extensive research and developed welding wires to get the chemistry in single layer which reduces product time and problems associated with welding like distortionWeld overlay is normally used in the context of adding filler metal on a substrate to either provide corrosion protection, build-up base material for dimensions or provide wear resistance.All known arc welding processes like GMAW, GTAW, ESW, SAW and SMAW are being used to do weld overlay. While talking about corrosion-resistance weld deposit, the most popular chemistries are 304/304L, 316/316L and 347.Today for getting the above mentioned chemistry, we have to apply two or three layers to take care of dilution effect from the base material.Sandvik Materials Technology, a product area within the global Sandvik Group, has been in the forefront of developing new alloys for the industry in-line with the growing demands of the customers for enhanced corrosion resistance and superior product life cycles. Sandvik has done extensive research and developed welding wires to achieve the required chemistry in single layer. The major benefit in getting the chemistry in single layer are huge reduction in production time, less consumption of welding consumables and reduced problems associated with welding like distortion.The paper will cover the details about the welding wire Sandvik 24.13.LHF, Sandvik 24.16.3.L and Sandvik 24.13.LNb grade chemistry, mechanical properties and actual trial result of Sandvik 24.16.3.L grade.Today’s way of wire cladding•    To get chemical comp. 304/304L or 308/308L overlay: 1st layer 309L, 2nd and 3rd layer 308L•    To get chemical comp. 347 overlay: 1st layer 309L, 2nd and 3rd layer 347•    To get chemical comp. 316/316L overlay: 1st layer 309L, 2nd and 3rd layer 316L.Advantages of single-layer surfacing•    Saving time: less welding time, shorter lead time•    Increasing productivity: higher output, faster in production, less weld cleaning and distortion•    Cutting costs: less inventory, lower transportation cost.Suitable processes for weld surfacing •    TIG•    Plasma-arc•    MIG •    Submerged-arc welding.Influence of parameters•    Surfacing has to be done in such a way that the dilution always is kept low.•    The arc should always “rest” on the weld pool and on the previous bead welded.•    Position of torch is therefore very important.•    Lower amps, higher voltage and lower speed are generalrecommendations to keep dilution lowThree innovative welding wire grades•    Sandvik 24.13.LHF (ER 309L high ferrite): for single layer 304/304L or 308/308L•    Sandvik 24.13.LNb (ER 309LNb): for single layer 347•    Sandvik 24.16.3.L (ER 309LMo): for single layer 316/316L.Sandvik 24.13.LHF•    Used for TIG, MIG, plasma-arc and submerged-arc welding•    Particularly suitable for overlay welding and joining dissimilar steels•    Excellent resistance to hot cracking due to its enhanced ferrite content•    Suitable for overlay welding of carbon and low alloy steels, where a type 304/304L, 308/308L overlay is required.Ferrite contentThe ferrite number according to the DeLong diagram, based on the aim composition = 16FN.The data is typical for non-heat treated all weld metal made by MIG welding with a shielding gas of Ar + 2 per cent O and TIG or plasma arc welding with argon as shielding gas.Thermal expansion per C, from 20 C to 400 C 18 x 10-6. Density, gm/cubic cm, at 20 C 7.9.Sandvik 24.13.LNb •    A niobium stabilised over alloyed filler metal •    Suitable for overlay welding of carbon and low alloy steels, where a type 347 overlay is required•    Used for TIG, MIG, plasma-arc and submerged-arc welding.Austenitic matrix with a ferrite content of about 13 FN according to DeLong.Sandvik 24.16.3.L •    Sandvik 24.16.3.L is unique•    Particularly suitable for overlay welding on carbon and low alloy steels•    The corrosion resistance of the weld overlays are at the same level as the 316/316L base metal •    Pitting resistance is very good due to high Cr, Mo and N-content •    Used for TIG, plasma-arc, MIG and submerged-arc welding•    SANDVIK 24.16.3.L overlays fulfill requirements in NACE MR0175 or MR0175/ISO15156•    Corrosion resistance of SANDVIK 24.16.3.L similar as/better than that of 316/316L base metal•    Overlays made with SANDVIK 24.16.3.L are fully austenitic•    High Ni-content increase resistance to H2S induced stress corrosion (SSC)•    High Cr and N-content increase resistance of 316/316L to mixed corrosion with carbon dioxide (CO2) and water containing chlorides (pitting and crevice corrosion).Austenitic matrix with a ferrite content of about 11 FN according to DeLong Ferrite measurementFerrite number was measured using ferritoscope in the machined component at 1.6 mm down from top surface and the results are:ApplicationSome of the applications where single layer weld overlay is being used are valve and valve components, cladding on pipe and pipe fittings.ConclusionThe overlay weld tested has a chemical composition that is substantially higher than that of 316L. This means that the composition gives margin for variation in dilution with the base metal. No fissures or other defects could be seen at the micro study. The ferrite content of <5 per cent, tells that the solidification mode of the weld metal is primarily ferritic, which is rather safe concerning hot cracking.It is possible to achieve 304/304 L, 316/316L and 347 chemistries in single layer using welding wire. The carbon content in the base material decides the final chemistry (316/316L). Dilution control is a key to get desired result in single layer weld overlay technique. The savings in terms of welding time and consumable is quite significant with single layer weld overlay.