The iron is the fourth most abundant in the Earth’s crust metal and is part of several minerals, such as oxides. Steel is an alloy of iron with a proportion of less than 2.1% carbon. The stainless steel used in the windows, contains in addition a minimum of 10.5% chromium or other metals such as nickel and molybdenum, which makes them more resistant to corrosion.
The metalwork broke slowly at the end of the 19th century, imitating the large civil works of steel and glass prices are more competitive but with low grades. Little by little there would be its industrialization with profiles of iron lighter and more resistant.
The evolution of the steel has managed materials like stainless steel, alloys of high corrosion resistance and long-lasting, and which also allows windows all open systems. Drawback however, is their low thermal insulation. On the other hand, enameled steel windows are less expensive than stainless steel.
Processes of transformation of iron and steel
The uses of pure iron are limited in such a way that most of this is subjected to special treatments that transform it into wrought iron, cast iron or steel. The wrought iron as used years ago was a different from the of the steel manufacturing process. This was called pudelizacion and was to make more malleable iron burning bituminous coal in furnaces, whose walls of the Crucible are joined with a paste of iron oxide.
This system stopped using since it required a more manual work, giving way to open Crucible Furnaces, Bessemer converters systems although today can be replaced by steel of low carbon of better quality and lower cost of production.
The most common processes for foundry and refining of iron and steel are made in blast furnaces, where the heat comes from the combustion of gas and raw material is iron ore. Here blend coking coal – making fuel – with iron ore, which absorbs more carbon, resulting in cast iron, becoming refined once in steel by means of air and limestone.
Stainless steels and alloy steels, requiring to be manufactured under a very stringent specifications are produced in electric arc furnaces. This type of furnace, whose raw material is scrap iron, has a better thermal efficiency compared to conventional ovens and the purity of the product is higher, but its production is on a smaller scale.
There are five different types of steel of different alloys and for different uses, these are carbon steels – representing more than 90% of all steels; Alloy steels; Low alloy steels ultra-strong; Stainless steels and tool steels.
Between the different processes of stainless steel finish is laminate, which is done first in hot, passing the material between a series of metal rollers that flatten it to the shape you are looking for. Then is it laminated in cold, which reduces its thickness and gives it more strength and hardness.
Different colors can be given to the finish and with different methods. One of them is the colored electrolytic, which is made by a chemical process that consists in submerging steel in an acid solution. The layer formed receives the light interference, giving rise to an effect of intense color that can be bronze, gold, purple, red and green. There are also finishes enamels, lacquers and varnishes that in addition to providing color protect it.
Properties of stainless steel
Stainless steel is the most used for window profiles alloy. Chromium-containing – that is always more than 10.5% – increases the depth of hardening, resistance to high temperatures and corrosion. Also many stainless steel alloys contain nickel, which also strengthen these properties, give ductility. Molybdenum, which greatly increases the depth of hardening of steel and its resistance to aggressive environments is also common.
The system of protection of these elements works forming a transparent protective layer and thin so-called passive layer. When it is damaged with scratches stainless steel, this layer becomes to form instantly with the oxygen of the air or the water, protecting the surface from oxidation.
However, despite the passive layer, chrome and other elements, its surface can be rust, which is the formation of iron oxide and whose process of oxidation is what we call corrosion. This can occur when the composition of the steel is not appropriate for the weather conditions and work to which it is subjected.
To avoid this possible corrosion, protects its surface with paint and special varnishes, increasing its resistance to external agents. It can happen also, cracks or punctures forming in small areas of steel where there is no oxygen, such as compact corners, mechanical joints or poorly finished welds.
The passive layer may also be affected by some acids that attack, hydrochloric acid, hydrofluoric acid and sulfuric acid. While that other elements such as nitrogen and titanium alloy, improve resistance to corrosion of stainless steels and also enhance its formability, strength and fire resistance.
Durability is one of the great properties of stainless steel, while another of its advantages is that its non-porous and smooth surface prevents bacteria or other organisms to adhere and survive in it. For this reason, use tends to be more frequent than other materials in the food and medical industries.
Cleaning, maintenance and recycling
Stainless steel is an easy-to-clean material. To clean the dirt or fingerprints using a soft cloth or sponge soaked in water with SOAP or a Microfiber cloth slightly dampened with water, while a soft cloth with a normal dishwasher can be used to remove grease stains.
It is important to avoid using abrasive powder, since they can scratch the surface. Nor disinfectants should be used with bleach in prolonged or contact very concentrated or cleaners with chlorides. Salt can also cause damage to the stainless steel.
Steel wool or wire brushes, which in addition to scratch it can remove remains of steel carbon, causing in case of wet oxidation should not use. The frequency of cleaning in the windows of stainless steel on the outside, with a moderate soil, is normally between 6 and 12 months.
Depending on the area, the profiles can be exposed to some or other agents, such as pollution, marine atmospheres and/or spray salt on roads to prevent freezing, which can cause the appearance of brown spots. You should be one or more of the above conditions or for an abundant soil, it is recommended to use stainless steel cleaner containing phosphoric acid and a cleaning every 3-6 months.
It is advisable to dry the surface once cleaned and rinsed, to prevent get watermarks, especially in hard water areas where also leave residues of lime. Treatments of glazed, lacquered or anticorrosive varnishes protect it and allow extending its useful life.
Stainless steel is 100% recyclable. Even after decades of use, it can be recycled again and again, without any loss of quality. To produce stainless steel stainless steel recycling, energy needs are reduced in their manufacture.