Stainless Steel - Group 5+6

Outokumpu Stainless Steel

Outokumpu is a global leader in stainless steel with cold-rolling capacity of 2.6 million tonnes. They create advanced materials that are efficient, long lasting and recyclable – helping to build a world that lasts forever.

Stainless steel is an ideal material to create lasting solutions in demanding applications from cutlery to bridges, energy to medical equipment. Stainless steel as a material is 100% recyclable, corrosion-resistant, maintenance-free, durable and hygienic.

Outokumpu's operations in Sweden include integrated stainless steel mill in Avesta and cold rolling mills in Kloster and Nyby. All of the Swedish mills focus on high performance stainless grades, and they became part of Outokumpu after Avesta Sheffield acquisition in 2001. Together, they form the Avesta business line in the Coil EMEA business area.

Outokumpu's integrated stainless steel mill in Avesta includes melt shop, hot rolling mill and cold rolling mill. Avesta produces thick, two-metre wide coil and plate, with particular emphasis on special grades, such as duplex grades. The site also houses an R&D centre. Avesta, together with Nyby and Kloster mills, is part of the Avesta business line in the Coil EMEA business area.

History

The Avesta site has a long history of producing steel, especially duplex grades: Avesta invented and produced first commercial duplex stainless steel in 1924.

Outokumpu has been instrumental in developing the stainless steel industry into what it is today. Indeed the history is as old as that of stainless steel itself, dating back a century to sites in Germany and the UK where stainless steel was invented in the beginning of the 1900s and in Sweden, where duplex was invented.

The production facilities now cover all continents and are located in China, Finland, Germany, Mexico, Sweden, the UK and USA.

The mills in Sweden produce high-performance stainless steel, from high-alloyed austenitic to various duplex grades. Outokumpu even owns the largest known chromite reserves in Europe and thus has unique competitive advantage in its access to raw material that makes steel stainless: chromium.

Process

1. Bring in the metal and sort it:
Outokumpu's stainless steel production is based on recycling, with the main raw material being recycled steel. Radio-actvitiy is checked before the steel can be used in production. If the steel is found to contain radioactive qualities it is returned to the company who brought up.

2. Scrap Pre-heating 300 degrees Celsius:
This process melts any ice or snow that might be on the steel before it goes into the electric Arc Furnace, this prevents any explosions occurring when the steel is put in the furnace. 


3. The Arc furnace at 1650 degrees Celsius for 1 hour:
Melting takes place in an electric arc furnace, which is charged with recycled steel and other raw materials – nickel, molybdenum oxide and ferrochrome. A major advantage of Outokumpu's integrated production process is that the ferrochrome produced in-house can be fed directly into the furnace in a molten form, saving considerable quantities of energy. 

4. Converter:
In this part of the melting process, they add oxygen to reduce the coal component, the steel is therefore refined to determine the composition of the it according to the customers requirements. 

5. Adding and adjusting:
The steel is rinsed with sulphur and transported to the ladle furnace. This is where they ensure the correct composition of the steel and make sure it has the correct temperature for casting. Argon gas is allowed to bubble through the steam to remove any informalities within the steel, i.e.; leftover debris.

6. Casting.
The steel is cast between 35 to 45 minutes. Steel is cast at a metre per minute which equals a flow of steel of circa 2 tonnes per minute. After the cast is complete, a cutting machine cuts the slabs into approximately 14 meters long (and weighing 20-26 tons). After the casting, some types of steel are sent to  be polished so there are no surface defects within the material. The polishing happens at 800 degrees Celsius. 

7. Hot grinding:
Slabs of stainless steel, are transferred to the hot rolling mill. The steel has a thickness of 140-200mm at this stage and is reduced to somewhere 2.5mm and 12.7mm with a length up to 1km. The temperature is raised to 1250 degrees celsius within the mill. The steel is transported through the mill 3 to 9 times depending on the thickness needed at 1010 degrees calcium. When the steel is ground, it gets rolled into a band roll, that is then weighed, marked and sent to cool off. First in the air and then in water. The steel is either then sent to the customer or to the cold grinder.

8. Cold grinding:
The steel gets to cool off under controlled circumstances for the steel to be the correct mechanical requirements. The steel is then sandblasted to clean the surface of the steel. Two thirds of the material is then sold as heated and sandblasted hot ground steal and the other third that is left goes to be cold grinder again. In the cold grinding process the steel is ground down to 1.5mm at the thinnest. The cold grinding gives the steel a nice finish. The steel sheet is finished off, it is cut into certain dimensions depending on the customer.