Carefully chosen materials come together with strong skills in casting techniques to ensure the high quality of the final product. Experience spanning several decades forms the foundation for our expertise. We have in-depth knowledge of the whole process, from start to finish. We continuously monitor and develop the quality of our work.
In centrifugal casting, the molten metal is poured into a steel mould, which rotates around its axis either horizontally (shown in the picture) or vertically. The exterior of the mould is cooled with water to ensure directional solidification. The method produces dense castings of consistent quality. During the casting process, any porosity present in the molten metal becomes localised to the inner layer, which is removed by machining.
In the continuous casting technique, the molten metal is poured from a furnace to a graphite die, via a crucible. The die is cooled with the aid of a water-cooling jacket, to guarantee directional solidification. In the casting of hollow billets, a mould is placed inside the die to produce the interior shape for the billet. This method allows the production of precisely dimensioned billets for further machining. Billets intended for automatic machining must be straightened before delivery.
Bronze alloys are used in the production of machines whose parts must have good sliding properties and be resistant to seawater and chemical corrosion. This group of materials covers a wide range of metals. Bronze alloys are used not only when dry lubrication and great strength are required; they also offer good machinability and finishability.
Combining strength with wear resistance, tin bronzes are the right choice when the material needs to retain its dimensions even under heavy loads and when subjected to sudden impacts. Mating material should be hard and tempered. Tin bronzes do not have good surface-pressure-resistance properties but are resistant to seawater.
Known for its corrosion resistance, aluminium bronze possesses great strength but has poorer sliding properties and wear resistance than the above-mentioned alloys. Its use for sliding bearings is recommended only when the strength properties offered by tin bronze are insufficient. Aluminium bronze is resistant to seawater.
Gunmetal is the most affordable and commonly used material for general-purpose sliding bearings. In addition to being resistant to seawater, it has good wear resistance and sliding properties. Gunmetal is not recommended for sliding bearings when sand cast, as the technique reduces its resistance to the effects of exposure to seawater.
In conditions where lubrication must be intermittent or otherwise may be insufficient, leaded tin bronze is the best material for bearings in terms of wear resistance and sliding properties. Water-based lubricants may also be used with leaded tin bronze. Leaded tin bronzes can withstand high surface pressure and are resistant to seawater.
With better strength characteristics than gunmetal and tin bronze, manganese bronze is in nearly the same class as aluminium bronze. It possesses higher machinability than aluminium bronze, but in respect of wear resistance and sliding properties it ranks below gunmetal and tin bronze. This alloy is malleable.
Johnson Metall AB
SE-703 83 Orebro
+46 1917 5100