WHAT IS STAINLESS STEEL, ITS HISTORY, TYPES OF STAINLESS STEEL
Table of Contents
Dear Folks! In this article, let’s see all about Stainless steel, its history, types of stainless steel.
INTRODUCTION
Stainless steels are an important class of engineering materials that have been used widely in a variety of industries and environments. Stainless steels are used in a wide variety of applications, such as power generation, chemical and paper processing, and in many commercial products such as kitchen equipment, surgical and medical tools and automobiles.
WHAT IS STAINLESS STEEL?
Stainless steels constitute a group of high alloy steels based on the Fe-Cr, Fe-Cr-C, and Fe-Cr-Ni systems. Stainless steels must contain a minimum of 10.5 wt% chromium. This level of chromium allows the formation of passive surface oxide that prevents oxidation and corrosion of the underlying metal under ambient, non-corrosive conditions.
Corrosive media that attack and remove the passive oxide cause corrosion of stainless steel. Corrosion can take many forms, including pitting, crevice corrosion and intergranular attack. The forms of corrosion are influenced by the corrosive environment and the metallurgy of the material.
HISTORY – A SHORT REVIEW
The addition of Cr to steels and its beneficial effect on corrosion resistance is generally attributed to Frenchman Berthier. In 1821, he developed a 1.5 wt% Cr alloy for cutlery applications.
- 1821: Frenchman Berthier experiments with Cr additions to steel.
- 1897: German Goldschmidt develops techniques to produce low carbon, Cr bearing alloys.
- 1904-1909: 13 wt% and 17 wt% Cr alloys produced in France and Germany.
- 1913: Englishman brearly casts first commercial ingot at Thomas firth and sons.
- 1916: U.S patent for 9 to 16 wt% Cr steel with less than 0.7 wt% carbon.
TYPES OF STAINLESS STEEL
Unlike other material systems, where classification is usually based on chemical composition, stainless steels are categorized based on the metallurgical phases, which is predominant. The three possible phases of stainless steel are martensite, ferrite, and austenite.
The American Iron and Steel Institute (AISI) uses a system with three numbers, followed by with or without a number. Examples SS304, SS304L
- Martensitic stainless steel
- Ferritic stainless steel
- Austenitic stainless steel
- Duplex stainless steel
- Precipitation hardened stainless steel
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Author: MOHAMMEDRIYAZDHEEN A (Director – Projects and Business Operations)
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