Here's a quick overview of how stainless steel is made from mine to manufacturer.
Due to its excellent corrosion resistance, high strength and attractive appearance, stainless steel (inox) has a wide range of uses in both industrial and consumer markets. Most stainless steel begins life in a similar way before it is processed. This processing, together with the exact alloy composition of the steel, determines many of its characteristics.
So, to understand how stainless steel is made, we must first dive into its composition.
WHAT IS STAINLESS STEEL?
Stainless steel (INOX) is an alloy of iron and chromium.
While stainless steel must contain at least 10.5% chromium, the exact components and ratios will vary depending on the required quality and use of the steel. Other common additives include: • Nickel • Carbon • Manganese • Molybdenum • Nitrogen • Sulfur • Copper • Silicon. The exact composition of the alloy is strictly measured and evaluated during the alloying process to ensure that the steel exhibits the required qualities. Common reasons for adding other metals and gases to a stainless steel alloy include:
Increased resistance to corrosion
High temperature resistance
Resistance to low temperatures
Improved strength
Improved weldability
Improved formability
Controlling magnetism
However, what's in your stainless steel isn't the only factor in determining its unique characteristics... The way it's made will further alter the properties of the steel.
HOW IS STAINLESS STEEL MADE?
The exact process for a type of stainless steel will vary in later stages. The way a type of steel is shaped, processed, and finished plays a significant role in determining how it looks and functions. Before you can make a deliverable steel product, you first need to create a molten alloy. That's why most types of steel share common initial steps.
Step 1: Melting
The production of stainless steel begins with the melting of scrap metal and additives in an electric arc furnace (EAF). Using high-powered electrodes, EAF heats metals for many hours to create a molten, liquid mixture.
Since stainless steel is 100% recyclable, many stainless steel orders contain as much as 60% recycled steel. This helps not only to control costs but also to reduce environmental impact.
The exact temperatures will vary depending on the quality of the steel being made.
Step 2: Carbon removal
Carbon helps to increase the hardness and strength of iron. However, too much carbon can create problems such as carbide precipitation during welding. Before casting molten stainless steel, it is necessary to calibrate and reduce the carbon content to the appropriate level. There are two ways that foundries control the carbon content.
The first is through argon oxygen decarbonization (AOD). Injecting an argon gas mixture into molten steel reduces the carbon content with minimal loss of other essential elements.
Another method used is vacuum oxygen decarburization (VOD). In this method, the molten steel is transferred to a second chamber where oxygen is injected into the steel while heat is applied. A vacuum then removes the outgassing from the chamber, further reducing the carbon content.
Both methods offer precise control of carbon content to ensure the proper blend and exact characteristics in the final stainless steel product.
Step 3: Setup
After carbon reduction, a final balancing and homogenization of temperature and chemistry occurs. This ensures that the metal meets the requirements for its intended grade and that the composition of the steel is consistent throughout the batch. Samples are tested and analyzed. Adjustments are then made until the mixture meets the required standard.
Step 4: Formation
With the molten steel created, the foundry must now create a primitive shape that is used to cool and process the steel. The exact shape and dimensions will depend on the final product.
From here, the steps will vary depending on the intended class and final product or function.
The following steps are the most common:
1. Hot rolling
Performed at temperatures above the recrystallization temperature of the steel, this step helps to adjust the rough physical dimensions of the steel. Precise temperature control throughout the process keeps the steel soft enough to work with without changing its structure. The process uses repeated passes to slowly adjust the dimensions of the steel. In most cases, this will involve rolling through multiple mills over time to achieve the desired thickness.
2. Cold rolling
Often used when precision is required, cold rolling occurs below the recrystallization temperature of the steel. Multiple support rolls are used to shape the steel. This process creates a more attractive, uniform finish. However, it can also deform the structure of the steel and often requires heat treatment to recrystallize the steel to its original microstructure.
3. Annealing
After rolling, most steel goes through an annealing process. This involves controlled heating and cooling cycles. These cycles help soften the steel and relieve internal stress. The exact temperatures will depend on the grade of steel, with both heating and cooling affecting the final product.
4. Descaling or pickling
As steel is processed through various steps, scale often builds up on the surface, which can affect the stain resistance, durability and weldability of the steel. Removing this scale is essential to creating the oxide barrier that gives the stainless layer its characteristic corrosion and stain resistance. The scale is removed using an acid bath or by controlled heating and cooling in an oxygen-free environment. Depending on the final product, the metal may be returned to the rolling mill for further processing. This is followed by repeated annealing stages until the desired properties are achieved.
5. Cutting
Once the steel is processed and ready, the batch is cut to fit the order requirements. The most common methods are mechanical methods, such as guillotine cutting, circular knives, high-speed knives or die cutting. However, for complex shapes, flame or plasma cutting can also be used. The best option will depend on both the desired steel grade and the desired shape of the delivered product.
6. Finishing
Stainless steel is available in a variety of finishes from matte to mirror. Finishing is one of the final steps in the manufacturing process. Common techniques include acid or sand etching, sandblasting, belt grinding, and belt polishing. At this point, the steel is given its final shape and is ready for shipment to the customer.
CONCLUSION
Understanding the appropriate grades and types of stainless steel for specific applications and environments is an essential part of ensuring long-lasting results and optimizing costs. Whether you're looking for something strong and corrosion-resistant for marine environments or something stunning and easy to clean for restaurant use, there's a stainless steel alloy available to suit your needs.
English 
Bosnian