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Aluminium Heat Treatment
Since the 1980’s the automobile industry has built upon the lightweight material aluminium and the resulting weight-saving in vehicles.
The Hanomag Heat Treatment Group specialised early in the heat treatment of aluminium and, with approximately 45,000 tonnes a year, is the leading aluminium heat-treater in Germany.
Alongside the metallurgical advancements, there has also been intensive development in the are of workability. Currently, the main areas of development in the processing of aluminium are in foundry technology and heat treatment.
Our modern roller-hearth installations are used primarily for the treatment of cylinder heads for the automobile industry. However, shaped components for cross-members, frames, consoles and side-panels are annealed according to DIN 1725T2. We use the following process in the heat treatment of aluminium components:
Solution Annealing with Warm-Ageing
Solution annealing with subsequent warm-ageing increases the strength of the material through precipitation-hardening.
Basically, precipitation-hardening encompasses all heat treatment measures that utilise the temperature-dependency of the solubility of mixed crystals to obtain an increase in strength.
Hardening comprises three stages:
Solution annealing is carried out, depending on the alloy, according to DIN 1706 at temperatures between 480 - 550 °C. A temperature is selected at which a sufficient amount of alloying element is dissolved in the mixed crystals to ensure that the precipitation-hardening effect occurs after quenching and ageing.
The precipitation-hardening effect is dependant on the solution annealing temperature, the pre-annealing time, the temperature of the cooling medium, the temperature of the component at the moment of quenching, the ageing temperature and the ageing time.
This process is very demanding of the heat treatment shop and requires absolute precision. If, for example, the specified maximum temperature for solution annealing is exceeded, the grain boundaries can melt, rendering the component useless.
We have been using this process for more than 15 years and have gained a great deal of experience, which we would be happy to share with you.
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