What are ferrous metals

Types of metal in construction: the large overview of materials

Metals are all chemical elements that have a crystalline structure with a metallic bond. Metals are always characterized by high density and strength as well as good thermal and electrical conductivity. Most of them are malleable and have a shiny surface, some metals are magnetic. A special feature of metals is their plastic deformation under high loads - they "flow". For this reason, when they are used in construction, it is not their breaking load that is decisive, but the stress equivalent to a yield point. Metals are divided

  • according to their density: in light metals (density up to 4.5 g / cm3 e.g. aluminum, beryllium, magnesium, titanium, zirconium) and heavy metals such as iron (Fe), copper (Cu), zinc (Zn), lead ( Pb), nickel (Ni), tungsten (W),
  • according to their chemical resistance: in precious metals and base metals, as well
  • in ferrous and non-ferrous metals (= non-ferrous metals)

What is Nirosta?

Stainless steels are alloyed stainless steels with a chromium content of at least 10.5% and a maximum carbon content of 1.2%. This makes Nirosta (name of a protected brand) particularly resistant to chemically aggressive substances.

No building project without iron and steel

Little goes in the construction industry without ferrous materials. In addition to iron itself, it is primarily its refined version, steel, with which many construction projects, especially in the industrial sector, are realized. Just think of profiles and supports, reinforcement, but also roof coverings or facade cladding.

Iron has a density of 7.86 g / cm3, a melting point at 1536 ° C and its boiling point at approx. 3070 ° C. It occurs in ores as oxide and carbonate, such as. B. Magneteisenstein, Roteisenstein, etc. before.

However, pure iron is too soft as a building material. The metal only becomes hard enough when it is alloyed. For this, the iron is mixed with elements such as carbon, sulfur or silicon or with other metals (aluminum, chromium, nickel, tungsten, manganese). Iron alloys with a share of more than 2.06% carbon are called cast iron. Alloys with less than this 2.06% carbon are called steel. Depending on their content of other alloying elements, a distinction is made between unalloyed and alloyed steel. By changing the composition and adding elements, the properties of the material are further improved: a further addition of carbon or chromium increases the hardness, chromium or nickel the corrosion resistance, etc.

  • Alloy with carbon makes iron stronger, more pressure-resistant and more brittle (cast iron or steel)
  • Alloy with manganese / tungsten makes iron harder
  • Alloys with chrome, aluminum and copper make iron more rust-resistant
  • Alloy with nickel makes iron more heat resistant
  • Alloy with silicon makes iron acid-resistant and more elastic

Stainless steel has a high degree of purity

Stainless steels are high-quality steel mixtures that have a high degree of purity and whether their uniform properties are intended for heat treatment. A distinction is made between stainless steel according to its properties (e.g. chemically resistant, heat-resistant, high-temperature resistant, weldable steels, steels with special physical or magnetic properties ...) and according to their use, e.g. B. Construction, mechanical engineering, tool, high-speed, roller bearing steels, etc.

Non-ferrous metals for rust-free building

The so-called non-ferrous metals include silver, gold, magnesium and titanium. However, these are not as interesting for the construction industry as aluminum, zinc, copper and lead, which are less susceptible to rust than ferrous metals. Let's take a closer look at the most important representatives.

aluminum is probably the best-known light metal, but due to its energy-destroying extraction it repeatedly (and rightly) falls into disrepute. In addition to iron and steel, aluminum is the most widely used construction metal, mainly used for window frames, doors, shutters, roofing and facades. Its advantages: low weight, easily deformable in cold and warm condition, easy processing by soldering, welding, gluing or riveting.

This is also used very often copper with its alloys brass (copper-zinc alloy possibly with lead and other additives), tombac (brass with over 67% copper), bronze (copper and tin) and gunmetal (copper, zinc and tin). Copper roofs and copper pipes are known.

zinc can - for example in comparison to aluminum - be produced quite cheaply. It is easy to process and, thanks to its oxide surface, is well protected against rust. In the construction industry, zinc is the ultimate anti-corrosion agent and is used, for example, to coat steel. In addition, zinc - but mostly as an alloy (titanium zinc) and not in its pure state - is used for roofing, gutters, downpipes or for facade cladding.

Did you know?

Corrosion is the damage and destruction of metals by chemical reaction (with gases or mechanically) or by electrochemical reaction (by water, acids, bases). Corrosion protection is created by applying dense coatings (e.g. made of tin, zinc).

Another important representative of the non-ferrous metals is the corrosion-resistant and very soft one lead. The metal can be cut and shaped very easily, even when cold, which makes it particularly interesting for small-area outdoor applications. For centuries, lead was an important, often used building material, but it is now known that it is poisonous and can damage people and nature. Lead is now gradually being replaced by other metals, and its use for pipes, for example, is now also banned.

Surface finishing of metals

To protect against corrosion, the surfaces are refined using special processes. That includes that Tinwhere a special hot-dip process or electrolytic deposition of tin creates a layer up to 40 µm thick (tinplate).

At the Hot-dip galvanizing a zinc coating of approx. 3.0 mm is applied to the steel surface in the immersion process at temperatures between 440 ° and 465 ° C, with special processes also up to 15 mm. The zinc layer must adhere well and be covering, without bubbles and without pores. On the surface, it appears glossy, matt or zink-flowered in gray. Further methods of surface finishing:

  • Zinc spraying is primarily suitable for repair work on the construction site
  • Anodizing (Anodizing is the oxidation of aluminum surfaces) of aluminum in accordance with ÖNORM C 2531
  • Special coatings such as fire protection coating etc.
  • Other surface treatments such as B. Plastic coating, powder coating, enamelling, chrome plating, copper plating and other electroplating processes

In order to give the surface color, the parts are usually stove-enamelled, powder-coated or specially color-coated. All RAL colors are possible, the surface can look from dull matt to glossy and its surface can be smooth, textured with a fine hammer or even with "orange peel".