Heat Treatment Cycle Time Reduction of Cylinder Head by Microalloying Aluminium Alloy 2006-32-0029
Aluminium finds diverse applications in the automotive industry. However, owing to its somewhat poor mechanical properties, the metal is unsuitable for structural applications. The problem is overcome by addition of alloying elements like zinc, copper, silicon, etc. and these alloys on proper heat-treatment show substantial improvement in the mechanical properties. Further enhancement of their mechanical properties can be brought about by the addition of small percentages of zirconium, which helps in the grain refinement of the cast alloy ingots.
At present for cylinder head the aluminium alloy used requires to be heat treated for a cycle time of about 15 hours (T6 condition) to achieve the desired mechanical properties. The proposed aluminium alloy, which contain microalloying element, Zirconium of about 0.12 weight %, can achieve the required mechanical properties with about five times reduced cycle time (T5 condition) only. All other properties viz., castability, machinability, wear resistance, high temperature tensile properties etc., were studied for the microalloyed alloy and found to be superior than the aluminium alloy being used at present. Cylinder head manufactured using the microalloyed alloy, tested for performance related tests is found to be comparable to the present alloy.
As the cycle time for heat treatment is reduced the productivity is increased and cost of manufacture is reduced. Distortion of the component due to heat treatment is decreased significantly as solution treatment is eliminated. Most importantly as the wear resistance of the part is increased due to microalloying, the regions of high wear in cylinder head can be free from valve inserts. This leads to reduction in number of parts to be assembled and thus ease of assembly and manufacturing.