Stainless Steel Manufacturing Processes

Stainless steel is an alloy of steel with chromium as one of its elements. The other alloying elements may vary according to the structural and chemical properties required for the stainless steel. It is used in a wide range of applications from automobile to shipping components and consumer products to bulk material and handling equipment. One of the major positives of stainless steel is that it never easily corrodes because of the presence of chromium. There are a number of standard alloys of stainless steel. The manufacturing of stainless steel is a complex process. The basic manufacturing of stainless steel entails the following series of steps.

Casting of stainless steel
All the raw materials are heated together in an electric furnace for about 8-12 hours. When the raw materials are melted, they are poured into molds of required dimensions and allowed to cool. The casted stainless steel can be rectangular, billets, tubular or slabs.

Hot rolling
The semi-finished stainless steel then undergoes hot rolling process where the thickness of the sheets of stainless steel are reduced and made uniform. The stainless steel is passed through two rolls until the specified gauge is obtained.

Annealing
After the hot rolling process, the heat treatment of the stainless steel begins. Annealing is a process of heat treatment where the steel is heated and cooled in controlled settings to soften the final product. This process reduces the stress formed in the hot rolling process.

Sometimes, the stainless steel also undergoes age hardening where the strength of the product is increased by melting. Hardening at the right temperature is important. If the steel is heated at a lower temperature, it results in stainless steel of higher strength and lower toughness. On the other hand, if the steel is heated at a higher temperature, the stainless steel obtained is of higher toughness and lower strength.

The heating process as such does not alter the properties of the stainless steel. However, the cooling process determines the properties of the final product. After heating the stainless steel for about 900-1000 degrees Fahrenheit, the material is cooled by processes like water quenching where the raw material is subjected to ice bath for a couple of hours. This is essentially used for thicker sections of the steel. For thinner sections, cool air is blasted on sections of the metal and the process is called as air blasting.

Descaling
Descaling becomes necessary for a smoother final product. Heat treatment can cause formation of scales on steel. The most commonly used method for descaling is pickling where acids are used to descale the steel. In electro cleaning, the surface is applied with electric current using phosphoric acid and cathode to remove the scales. Depending upon the type of stainless steel, the process of annealing and descaling can span several steps.

Finishing
This is a vital step in the production of stainless steel as it determines the applications of steel and makes it easier to use. Depending upon the application, they can undergo smooth or rough finishing. Hot rolling, cold rolling, annealing, descaling  these processes depend on the application of the stainless steel.

Further treatments
Stainless steel may undergo further treatment depending upon its uses in an industry. It may undergo shaping, additional heat treatment, descaling and/ or welding.