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Grupo Alfonso Gallardo> Corrugados Azpeitia > Production Process

Production Process


To produce carbon or low alloy steel in an electric steel mill, the following operations are followed:

Handling and storage of raw materials:

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Scrap is stored in the scrap yard where different qualities of scrap are classified by density and chemical composition. Then it is loaded in baskets, adding lime as a flux, and then taken to the electric furnace.

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The electric heat along with natural gas burners with oxygen and carbon injections melts the scrap. The final product is molten steel, which passes on to the next stage.

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Induction Furnace: Molten steel is transferred to the Ladle Furnace where, with the addition of ferroalloys and flux, the final composition is adjusted and the sulphur is captured from the steel to form a layer of slag.

The molten steel is solidified into a semi-product called a "billet," a steel rectangular ingot with different lengths, which is done in the continuous casting.


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Continuous casting: Continuous casting is a process that casts from a sequence of ladles of molten steel into billets.

The steel is poured into a regulating deposit that then pours it into a hollow copper "ingot" mould that has the billetís square shape, and is then forcefully cooled with water in order to begin solidification.

When the billet is removed from the ingot mould, as it passes water is sprayed over its exterior to solidify it completely before cutting it with an oxycut to the desired length.

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After the first steel mill process and after obtaining the billet, the process continues with the hot rolling in order to obtain the ribbed rebar for reinforced concrete. Rolling consists of continuously reducing the cross-section of the billet by passing it through various rolling cylinders. The rolling stages are as follows:

Reheating Furnace: Its purpose is to heat the billet to the rolling temperature. For this, we use natural gas burners.


Grinding mill: This consists of four horizontal-vertical columns where the square cross sections of the 140 x 140 billets are reduced, slowly becoming rectangular until becoming round with a diameter of approximately 85 mm.

Intermediate mill: These are the reductions made between the grinding and finishing mill. The bar passes through the continuous rolling boxes which continue reducing the cross-section and produces a second cropping of the billet.
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Finishing mill: This is what we call the last reduction. After having passed this, the product has the desired form and cross-section. Here the ribs are carved.
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Thermo-mechanical treatment: With the aim of increasing the ribbed steelís resistance, the rebar is continuously thermo-mechanically treated. This treatment consists in hardening the barís surface upon finishing the last rolling process. For proper thermo-mechanical treatment, the barís temperatures, rolling speed, pressure and water pressure are controlled. The result is a product with surface resistance and a ductile core.
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Finishing and packaging: The finishing and packaging process depends on the way we supply the rebar. If it is supplied in bars, the product is evacuated in a toothed cooling sheet so that it cools uniformly throughout its complete diameter and length. Once cool, it is cut into bars at the established sales length and packaged.
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If it is supplied in a "spooler" the ribbed wire is sent to a mandrel where it is rolled around it while the wire moves straight throughout the mandrelís cone. This way we get a torsion-free roll , which is then strapped before being shipped.
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Here is where the final identification package labels are placed, showing all of the information including cast number, product, quality, production date, quality certificates and manufacturer.


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