Bronze

General information about bronze

From a historical point of view, the term bronze refers to alloys of copper and other metals, excluding only zinc. Depending on the metal selected, different types of bronze can be defined, for example tin bronze, aluminium bronze or manganese bronze.

From a technical point of view, the term bronze is precise only for tin bronze, which is also the best-known bronze alloy. In the case of tin bronze, a distinction is made between wrought and cast alloys. The division into one of the groups takes place via the tin content in the bronze. Wrought alloys have a maximum tin content of 8.5%, while cast alloys have a tin content of up to 22%.

With bronze, however, it is rare to work exclusively with two metals. In order to add further components and additives to the alloy, other metals are added to the alloy, for example to influence the properties. Popular metals for this purpose are phosphorus to increase the hardening capacity or nickel to increase the corrosion resistance (also in seawater).

Production of bronze

To produce bronze, the raw materials (pure metal, block metal or recycling material) are first melted down in large induction furnaces. The molten material, the melt, is then transferred to a casting furnace. Depending on whether it is a wrought or a cast alloy, the following processes differ from this point on. In the case of casting alloys, the melt is cast into a mould directly close to the end mould or even ready for final moulding. This ensures a short process, but also restricts the design and construction possibilities. In the case of wrought alloys, on the other hand, an ingot or strand mould is first cast, which is then brought into its final shape in further processes. Typical forming processes for wrought bronze alloys include rolling, drawing and extrusion.

The rolling process is subdivided into several process steps. First the ingots are rolled in several passes in so-called hot rolling mills. The oxide layer formed during hot rolling is then removed and cold rolling is continued.

Another forming process for bronze is extrusion. This process is used to produce bronze rods, bronze tubes, bronze profiles and bronze wires. Here, too, the starting material is first heated and then pressed through a forming die with high force. In the manufacture of a bronze tube, a mandrel is inserted into the device in the middle of the die. If the bolt is pressed against it, a cavity is created in the middle of the product.

How is bronze used?

Bronze is a material that can be used in many ways.

Wrought bronze alloys are used in almost all branches of industry, mainly because of their properties. Especially in electrical engineering, bronze is used due to its very good electrical conductivity in the form of current-conducting springs or plug-in sockets.

Bronze cast alloys are used in shipbuilding, for example for ship propellers, due to their very good corrosion resistance. Other areas of application for bronze casting alloys are, for example:

• Automotive
• Food industry
• Construction