Introduction

Stainless steel has become more than a material; it is a symbol of reliability and resilience. From the shimmering facade of skyscrapers to the sterile precision of surgical instruments, and the enduring quality of everyday objects, stainless steel had woven itself into the very fabric of modern life. It has a sheen that speaks of elegance and durability. Discovered in the early 20th Century it has evolved over the years and is used in diverse applications. Described in this article are the important  Stainless Steel properties and Stainless Steel types

Process

Iron ore along with coke and limestone is fed into a blast furnace, and hot air is blasted into the mixture. A reduction reaction occurs, producing molten iron or pig iron, which contains a high percentage of carbon and impurities such as silicon, manganese and sulphur. The molten pig iron is poured into a vessel called an LD ( Lintdz Donowitz) converter or BOF ( Basic oxygen furnace), where high-purity oxygen is blown through it. This oxidizes the carbon and other impurities producing molten steel with low carbon content.  Alloying elements like chromium, nickel, manganese, and molybdenum, are added to achieve specific characteristics. A secondary refining process is then conducted in an Argon Oxygen Decarburization ( AOD) furnace, where argon and oxygen are blown into the molten steel, further reducing the carbon content and refining the composition. This process helps in precisely controlling the levels of carbon, chromium and other metals.  If ultra-low carbon content is required, the Vacuum Oxygen Decarburization (VOD)  process is used.  The refined molten stainless steel is cast into semi-finished shapes like blooms, billets or slabs. To obtain a finished saleable product like sheets, the slabs are hot rolled, and then cold rolled in mills to form coils. An annealing process follows to relieve stresses, followed by a pickling process to remove surface oxide scales. The sheets are then slit, cut and stacked for packing and despatch.

Stainless Steel Types

Stainless steel is a versatile material used in a wide range of applications due to its corrosion resistance, strength, and durability. There are several types of stainless steel, classified primarily based on their crystalline structure. Here are some of the  primary categories :
 

Grades and Applications

The term "stainless steel" is used to describe a family of about 200 alloys of steel with remarkable heat and corrosion-resistant properties. The carbon percentage can range from  0.03 to 1.2%. Its distinguishing property is the high amount of chromium that enhances its corrosion resistance, and strength, and making the alloy rustproof, which is among the most important Stainless Steel Properties.

In India the standard  IS 6911: 1992 is widely followed. This defines the types, chemical analysis, mechanical properties, corrosion resistance and dimensional tolerances. However, AISI Stainless Steel Grades are generally used to classify stainless steel types as listed below :
 

SAE grades are also used for classifications.

Market Scenario

Presently the market size in India is estimated to be Rs 1,31,840 Crores with a CAGR of 6.2% up to 2034. The main sectors contributing to this growth are the construction and automotive industries. Much of the stainless steel is recycled, which makes it a relatively eco-friendly material.  About 43% of the Stainless Steel Manufacturing is located in western India due to its proximity to major ports for the import of alloying elements. Further, western India is also a major consumer and exporter. Austentic stainless steel is the most widely used type amounting to nearly 73%. Major producers like Arcelor Mittal, Jindal Stainless Ltd, and Nippon Steel have a substantial share of about 53%, with the balance shared by many other manufacturers. Major players are investing in research and development in the area of high-grade stainless steel with enhanced corrosion resistance and other special features.

Conclusion

Stainless steel has become more than a material; it is a symbol of reliability and resilience. In the shimmering facades of skyscrapers, the sterile precision of surgical instruments, and the enduring quality of everyday objects, stainless steel had woven itself into the fabric of modern life. We can expect continued  innovation in this field driven by  technological advancements.