Thixoforming : Semi-solid Metal Processing

Figure 9.7 Oil pump cover for Honda cars.
In a Japanese thixocasting project, moulding methods, optimal billet heating
speeds and copper die materials were established for an iron thixocasting process.
The manufacturing method was studied with an oil pump cover (Figure 9.7). An
improvement in the volume efficiency of the oil pump was confirmed due to the
stiffness improvement and clearance reduction effects.
9.3
Thixocasting of Steel Alloys
The multitude of steel materials with their wide range of mechanical properties,
relatively low costs combined with the advantages of the productive high-pressure
die-casting process open up numerous areas of application. This chapter takes a
closer look at the current work in the field of thixocasting of steel alloys.
9.3.1
Inductive Heating for Steels: Adaptation and Process Control
9.3 Thixocasting of Steel Alloysj319
Already in the processing of aluminium alloys it was found that complete form filling
and good component characteristics depend on the globulitic microstructure.
With regard to the melting behaviour of steel materials, high requirements are
placed on the reheating process. First, the warming must be fast enough that
coarsening of the solid phase is reliably avoided. Since steel billets have almost
three times the energy content of an Al billet, the nominal power must be greater than
at least 15 kW kg 1 . Otherwise, the industrial user is forced to invest in 10 or more
individual heating devices to use the short cycle times of a pressure die-casting
machine when required. Second, precision of the reheating process is required
because for some annealing steels a variation of only 15 K can makes a difference of
30–60% in the content of liquid phase. A few degrees difference in temperature