Stainless steel boilermaking

Overview

ABSTRACT

Due to its resistance to corrosion, its main property, stainless steel is a material of choice for steel metal work. A classification of stainless steels is proposed in this article: basic notions, structure diagrams and surface states. Martensitic, ferritic, ferritic-austenitic and austenitic stainless steels are then detailed by type through their composition, properties, treatments, forming, etc. The sound knowledge of the properties and behaviors of the stainless steel involved allows for adapting the industrial implementation methods to the end use (e.g. clad plates welding or assembly of tubes on tubular plates).

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AUTHORS

Pierre SOULIGNAC: Materials engineer from Ecole des Mines de Nancy - Industeel
Bernard BONNEFOIS: Materials engineer - Le Creusot Materials Research Center, Industeel
Etienne SOUTIF: Welding engineer - Technip

INTRODUCTION

The main defining property of stainless steels is their resistance to corrosion, making them the materials of choice for the chemical, petrochemical, pulp and paper, power generation, food and beverage, water, construction and civil engineering industries. This corrosion resistance is due to their high chromium content (10-30%), reinforced by additions of molybdenum (up to 7%) and other alloying elements such as tungsten, copper, nickel, nitrogen... Nickel and nitrogen are used to reinforce the structure of austenitic stainless steels, as they often play a positive role in their corrosion resistance, unlike carbon.

The presence of a "passive layer" on the surface of stainless steels, a guarantee of their good service life, means that it is essential to maintain – or, where necessary, reconstitute – during boiler-making operations, the surface condition adapted to the service conditions of the appliances or equipment.

To select and use the most appropriate processing methods for each stainless steel (of which there are around a hundred), it is essential to know its properties and processing behavior, which are, to a first approximation, related to the family to which it belongs.

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