Steel

The word "steel" describes a variety of workable (rollable and forgeable) iron alloys used very widely thanks to their almost unlimited properties.

Two basic processes are nowadays applied in the manufacture of steel:

• from iron ore: smelting in blast furnaces to obtain pig iron which is refined into steel by the oxygen lance process
• from scrap steel: smelting of scrap steel in electric arc furnace

The steel making process initially reduces the contents of tramp elements such as phosphorus and sulfur; alloying the resultant melt with other elements such as chromium, nickel, molybdenum etc. gives the desired properties.

Stahl Gerlafingen operates a modern high efficiency electric arc furnace for melting down scrap steel.

 

Scrap
Scrap steel, a waste material produced by our civilisation, is available in various forms. Just think of the many cars and lorries taken off the road each year, of the various installations and plants such as bridges, factories or giant sea-going ships subjected to the cutting torch.

This waste in the form of scrap steel is remelted in an electric arc furnace at Stahl Gerlafingen into high quality structural and reinforcing steel grades.

 

Electric shaft furnace
Stahl Gerlafingen has installed an electric shaft furnace of the latest design which consists of a crucible, a shaft arranged on the side above it and three power feed graphite electrodes with holders.

Scrap is preheated in the shaft by the chemical and tangible heat of combustion gases which brings about a corresponsing saving of energy.

After the tapping operation is completed, the emptied crucible is filled with pre-heated scrap; the energy of the arc between the electrodes and the scrap melts it down. At the same time, oxygen does the metallurgical work, that is, it lowers the carbon, phosphate and sulfur contents. Lime bonds the chemical compounds which form and run through the furnace door in the form of slag.

The melting down of the new charge (approximately 70 tons of steel), is continuously monitored to determine the correct tapping point which depends on temperature and the chemical composition of the melt.

When the required temperature and the chemical composition are reached, the taphole in the furnace base is opened and the melt allowed to run into a ladle lined with fire-proof coating.

 

Secondary metallurgy
The fast tap-to-tap times achieved with modern electric arc furnaces do not provide for fine adjustment of metallurgical quality.

Fine adjustments are introduced in a secondary process in what is referred to as a ladle furnace.

This is where the chemical composition of the steel and the temperature of the steel are adjusted to the level required for continuous casting. The grades of steel produced in Gerlafingen are unalloyed carbon steel grades with properties dependent on the appropriate carbon and manganese content. Vanadium forms a fine grain and is required in some steel varieties.

 

Continuous casting plant
Over the last 40 years, continuous casting has become increasingly popular in the production of rolling steel, particularly flat steel bars and long steel products.

Liquid steel is continuously poured into water-cooled copper molds with intermediate dimensions very close to those of the finished products (billets or slabs). Just the same amount of steel as enters the mold in liquid form is removed from the bottom end, solidified on the surface (mold 800 mm long) and cut with flame cutting machines to the required length. Slabs (130 x 170 up to 130 x 300 sq.mm) are carried to the storage by side loading form trucks.

 

Rolling mills
Stahl Gerlafingen operates two rolling mills set up for the production of high-quality structural and reinforcing steels.

Flat steel bars and universal plate from 100 to 300 mm wide is produced on what are known as a heavy product mill. The slabs cast in the steelworks are heated in a rotary hearth surface to the rolling temperature (approx. 1’200°C) and subsequently rolled in a roughing mill specially set up for this production. The rolled product cools down on a cooling bed and is then cut immediately to the required length and stacked in bundles. Each bundle is then labeled to show the steel quality, the charge number, dimensions and weight. The second rolling mill is a very modern, combined steel bar and rod mill, or a combi mill.

12.5 m long 130 x 170 mm slabs, 2.1 tons in weight, are heated in a continuous pusher-type furnace with a capacity of 100 t/h to the rolling temperature and then rolled in the rolling mills into the required product.

Rod mill:
For rolling wire 5.5 to 16 mm dia. and ribbed reinforcing steel 8 to 16 mm dia., supplied in coils. The final rolling speeds to achieve the smallest wire diameters are up to 100 mm/sec.

Standard specified properties of coiled reinforcing steel are achieved by inline water quenching from the rolling temperature.

Bar mill:
Reinforcing steel rods and steel bars up to 100 mm wide are rolled here on to a cooling bed almost 100 m long. Reinforcing steel rods are also quenched direct from the rolling temperature, just like the coiled product.

 

Reinforcing mat factory
High-quality, strainhardened reinforcing steel is made from rods produced in our own rolling mill (mill train) and reinforcing mats are welded in the Mat Factory of Stahl Gerlafingen AG. The soft and smooth rolled rods are cold-rolled in several stages (total deformation by 15%) and ribbed on the surface at the same time. This strainhardening operation gives the rods the technological properties required by the standards and the necessary adherence within the concrete provided by the ribbing.

These strainhardened, ribbed steel rods are available in coils or are welded into mats of various sizes and shape for reinforcing concrete structures.

Steel

The word "steel" describes a variety of workable (rollable and forgeable) iron alloys used very widely thanks to their almost unlimited properties.

Two basic processes are nowadays applied in the manufacture of steel:

• from iron ore: smelting in blast furnaces to obtain pig iron which is refined into steel by the oxygen lance process
• from scrap steel: smelting of scrap steel in electric arc furnace

The steel making process initially reduces the contents of tramp elements such as phosphorus and sulfur; alloying the resultant melt with other elements such as chromium, nickel, molybdenum etc. gives the desired properties.

Stahl Gerlafingen operates a modern high efficiency electric arc furnace for melting down scrap steel.

 

Scrap
Scrap steel, a waste material produced by our civilisation, is available in various forms. Just think of the many cars and lorries taken off the road each year, of the various installations and plants such as bridges, factories or giant sea-going ships subjected to the cutting torch.

This waste in the form of scrap steel is remelted in an electric arc furnace at Stahl Gerlafingen into high quality structural and reinforcing steel grades.

 

Electric shaft furnace
Stahl Gerlafingen has installed an electric shaft furnace of the latest design which consists of a crucible, a shaft arranged on the side above it and three power feed graphite electrodes with holders.

Scrap is preheated in the shaft by the chemical and tangible heat of combustion gases which brings about a corresponsing saving of energy.

After the tapping operation is completed, the emptied crucible is filled with pre-heated scrap; the energy of the arc between the electrodes and the scrap melts it down. At the same time, oxygen does the metallurgical work, that is, it lowers the carbon, phosphate and sulfur contents. Lime bonds the chemical compounds which form and run through the furnace door in the form of slag.

The melting down of the new charge (approximately 70 tons of steel), is continuously monitored to determine the correct tapping point which depends on temperature and the chemical composition of the melt.

When the required temperature and the chemical composition are reached, the taphole in the furnace base is opened and the melt allowed to run into a ladle lined with fire-proof coating.

 

Secondary metallurgy
The fast tap-to-tap times achieved with modern electric arc furnaces do not provide for fine adjustment of metallurgical quality.

Fine adjustments are introduced in a secondary process in what is referred to as a ladle furnace.

This is where the chemical composition of the steel and the temperature of the steel are adjusted to the level required for continuous casting. The grades of steel produced in Gerlafingen are unalloyed carbon steel grades with properties dependent on the appropriate carbon and manganese content. Vanadium forms a fine grain and is required in some steel varieties.

 

Continuous casting plant
Over the last 40 years, continuous casting has become increasingly popular in the production of rolling steel, particularly flat steel bars and long steel products.

Liquid steel is continuously poured into water-cooled copper molds with intermediate dimensions very close to those of the finished products (billets or slabs). Just the same amount of steel as enters the mold in liquid form is removed from the bottom end, solidified on the surface (mold 800 mm long) and cut with flame cutting machines to the required length. Slabs (130 x 170 up to 130 x 300 sq.mm) are carried to the storage by side loading form trucks.

 

Rolling mills
Stahl Gerlafingen operates two rolling mills set up for the production of high-quality structural and reinforcing steels.

Flat steel bars and universal plate from 100 to 300 mm wide is produced on what are known as a heavy product mill. The slabs cast in the steelworks are heated in a rotary hearth surface to the rolling temperature (approx. 1’200°C) and subsequently rolled in a roughing mill specially set up for this production. The rolled product cools down on a cooling bed and is then cut immediately to the required length and stacked in bundles. Each bundle is then labeled to show the steel quality, the charge number, dimensions and weight. The second rolling mill is a very modern, combined steel bar and rod mill, or a combi mill.

12.5 m long 130 x 170 mm slabs, 2.1 tons in weight, are heated in a continuous pusher-type furnace with a capacity of 100 t/h to the rolling temperature and then rolled in the rolling mills into the required product.

Rod mill:
For rolling wire 5.5 to 16 mm dia. and ribbed reinforcing steel 8 to 16 mm dia., supplied in coils. The final rolling speeds to achieve the smallest wire diameters are up to 100 mm/sec.

Standard specified properties of coiled reinforcing steel are achieved by inline water quenching from the rolling temperature.

Bar mill:
Reinforcing steel rods and steel bars up to 100 mm wide are rolled here on to a cooling bed almost 100 m long. Reinforcing steel rods are also quenched direct from the rolling temperature, just like the coiled product.

 

Reinforcing mat factory
High-quality, strainhardened reinforcing steel is made from rods produced in our own rolling mill (mill train) and reinforcing mats are welded in the Mat Factory of Stahl Gerlafingen AG. The soft and smooth rolled rods are cold-rolled in several stages (total deformation by 15%) and ribbed on the surface at the same time. This strainhardening operation gives the rods the technological properties required by the standards and the necessary adherence within the concrete provided by the ribbing.

These strainhardened, ribbed steel rods are available in coils or are welded into mats of various sizes and shape for reinforcing concrete structures.