[ Welding ]
[ Welding ]
Stainless steel welding characteristics & suitability with dissimilar metals
Welding plays a key role in all types of fabrication . This article discusses the mechanism of welding different categories of stainless steel with carbon steel , galvanised steel , aluminium , copper and tungsten .
By A . K . Vaish , Ritesh Patel *, B . J . Chauhan , S . D . Kahar , Ankit Bhojani , K . M . Bhaisaheb and Keshva Narayana .* Department of Metallurgical and Materials Engineering , The M . S . University of Baroda , India ; * Larsen and Toubro Ltd ., Hazira .
Welding is a fabrication process in which metals are heated , melted and mixed to produce a joint , whereby two or more parts are fused together . When used with filler material , it produces a stronger weld than the base material . The weldability of stainless steel is influenced by its alloying elements .
Versatile stainless steel Stainless steel comprises at least 10.5 % chromium , < 1.2 % carbon and other alloying elements such as nickel , molybdenum , nitrogen , titanium , niobium , manganese , etc . Chromium forms a stable oxide ( Cr 2 O 3 ) film on the surface , which is continuous , impervious and passive to stop any further reaction between steel and the surrounding atmosphere and protects the steel from further oxidation . A higher chromium content in stainless steel leads to higher resistance to oxidation . It possesses higher strength at room temperature as well as at high temperatures . Stainless steel can be grouped into five main categories : ( i ) Ferritic stainless steel Its microstructure is ferrite with a body-centered cubic grain structure . It is non-hardenable by heat treatment and marginally hardenable by cold rolling . ( ii ) Martensitic stainless steel It is austenitic at temperatures 950-1000 ° C , but transforms to martensite on cooling to room temperature . This steel can be quenched in oil or air from 1050 ° C ( when fully austenitic ) and then tempered to obtain a yield strength of 550-1860 Mpa . ( iii ) Austenitic stainless steel Has an austenite crystalline structure as well as a face-centered cubic structure . This steel is a single-phase FCC material and can be strengthened by cold working and cold solution strengthening . ( iv ) Duplex stainless steel Contains low carbon and is a mixture of ferrite ( bcc ) plus austenite ( fcc ). This steel has both structures and gets the benefit of both phases . ( v ) Precipitation – hardening stainless steel An iron-nickel-chromium alloy containing one or more precipitationhardening elements such as
40 Stainless Steel World December 2023 www . stainless-steel-world . net