Abstract
Duplex stainless steel finds widespread use in various sectors of manufacturing and related fields. It has many advantages due to its distinctive structural combination of austenite and ferrite grains. It is the need of the current generation due to its better corrosive resistance over high production austenitic stainless steels. This paper reviews the weldability of duplex stainless steels, mentions the reason behind the need for duplex stainless steels and describes how it came into existence. The transformations in the heat-affected zones during the welding of duplex stainless steels have also been covered in this paper. The formation, microstructure and changes in high temperature and low temperature heat-affected zones have been reviewed in extensive detail. The effects of cooling rate on austenite formation has been briefly discussed. A comparison of weldability between austenitic and duplex stainless steel is also given. Finally, the paper reviews the applications of the various grades of duplex stainless steel in a variety of industries like chemical, paper and power generation and discusses the future scope of duplex stainless steel in various industrial sectors.
Highlights
Stainless steel was developed in the early 20thcentury
During heat treatment, the initial grades of stainless steel were prone to grain boundary carbide precipitation, welding and intergranular corrosion attack
The low temperature heat affected zone has a thermal history which might result in the formation of intermetallic phases and is found further away from the fusion line [25]
Summary
Stainless steel was developed in the early 20thcentury. Production techniques at that time, resulted in higher amounts of carbon in these steels. During heat treatment, the initial grades of stainless steel were prone to grain boundary carbide precipitation, welding and intergranular corrosion attack. The addition of titanium pinned the grain boundaries that confined the enormous ferrite grain growth in the heat-affected zone due to the formation of chromium from carbides by titanium This provided the foundation for the discovery of the second generation of duplex [4, 5]. These grades having higher alloy contents encouraged intermetallic precipitation which led to reduction in properties [9] This shortcoming led to the development of lean duplex which had a lower alloy content, especially Molybdenum. On the basis of welding aspects, this paper compares austenitic and duplex stainless steels
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