347/ 1.4550 square stainless steel at high temperatures improved intergranular corrosion resistance and good mechanical properties, stabilized with niobium alternative stainless 321/ 1.4541. The 347/1.4550 is particularly useful in applications with intermittent heating in the 400–900 ° C range . 347 / 1. 4550 is an austenitic stainless steel belonging to standard CrNi stainless steels. 347 / 1. 4550 can be welded in all sizes without becoming susceptible to intergranular corrosion.
Austenitic CrNi standard grades are the most widely used range of stainless steels. Well balanced material properties make them suitable for the manufacture of many products.
347/4550 stainless steel has excellent corrosion resistance in solutions of many halogen-free organic and inorganic compounds over a wide range of temperatures and concentrations. It can withstand many organic and sufficiently diluted mineral acids, depending on the temperature of the solution. 347 / 1. 4550 grade stainless steel can be subjected to uniform corrosion in strong mineral acids such as hot concentrated nitric acid and hot strong alkaline solutions.
Due to the niobium content, the risk of sensitization for intergranular corrosion is greatly reduced compared to other austenitic CrNi standard grades with normal carbon content .
Presence of anti-corrosion or accelerating compounds eg . transition metal ions or organic compounds 347/ 1 4550'n may affect the corrosion behavior.
347 / 1. 4550 is prone to chloride induced stress corrosion cracking at temperatures above about 50 ° C, depending on the applied stress and the chloride concentration in the environment. Pre-cold deformation of the structure under load increases the risk of stress corrosion cracking.
347 / 1. 4550 square stainless steel can be easily formed and fabricated through all cold forming processes. The head can be used for pulling and bending. Any cold working process will increase the strength and hardness of the material and may leave it somewhat magnetic. Work hardening is accentuated by the partial transformation of the austenite phase of the material to hard martensite .
347 / 1. 4550 has excellent weldability and is suitable for all conventional welding methods (such as MMA, MIG, MAG, TIG, SAW, LBW or RSW) except gas welding. 347 / 1. 4550 stainless steel has approximately 50% higher thermal expansion and lower thermal conductivity compared to carbon steels. This means that greater deformation and higher shrinkage stresses can be caused by welding.
Autogenous welding can be used in thin sections. To ensure that the weld metal properties (eg strength, corrosion resistance) are equivalent to those of the base metal, preferably compatible or slightly over-alloyed fillers should be used. Suitable filler metals are 19 9 Nb or 19 9 L.
Generally, post-weld heat treatment is not required. In special cases where the risk of stress corrosion cracking or fatigue is high, stress relief may be considered.
To fully restore the corrosion resistance of the weld bead, the color change in the weld should be removed by pickling and passivation.
Surface dross particles containing Nb can be formed by TIG and plasma welding.
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