Castings Research

A wide variety of projects are carried out with public and  industrial funding.

  • EPSRC has recently sponsored research on the reliability of castings and the development of semi-levitation melting, and is currently supporting projects on investment casting, the tilt filling of moulds and the production of titanium aluminide castings.
  • The EC has supported projects on titanium in cast irons and the use of non destructive testing techniques for predicting the properties of austempered ductile irons.
  • Certain PhD research projects are supported by foreign governments and international organisations.
  • All remaining research is supported on a confidential basis by UK and overseas industry.

The various research projects can be classified as follows: 

  • Production of Reliable Castings.
    One of the key underlying themes of recent work has been to study the detrimental effects of filling moulds with molten metal under conditions that lead to surface turbulence. It has been shown that molten metal flow becomes unstable once its velocity exceeds a critical value of ~0.5 m/s. This results in bubble formation and subsequent damage and also the incorporation of double oxide film defects into castings. Both significantly reduce the reliability of castings and so it is essential that such defects are at least minimised and preferably eliminated by improving the filling of moulds. This is being achieved by radical changes to the design of running systems and by using alternatives to gravity pouring, such as tilt pouring.
  • Melting and Casting Titanium Aluminides.
    The family of titanium aluminides has great potential for a range of applications in the aerospace and automotive sectors, including turbine blades, turbocharger rotors and valves. The casting route is economically attractive but technically difficult as a result of the high reactivity of these alloys in the molten condition which precludes the use of conventional melting in a refractory crucible. The IRC is developing a process based on high power Induction Skull Melting in which the alloy is melted in a water-cooled copper crucible prior to investment casting into a ceramic shell mould. The high power minimises contact between the molten alloy and the crucible and significantly improves the superheat compared with that achieved in conventional ISM furnaces. Current research also includes assessing the reliability of TiAl castings as a function of mould filling, establishing the solidification behaviour of these alloys and investigating their tendency to undergo hot tearing.
  • Investment Casting.
    The IRC is undertaking a major EPSRC-funded project with the objective of obtaining a fundamental understanding of all aspects of the investment casting process. This has substantial industrial support from production foundries and suppliers to the industry. The aim is to produce higher quality and more reliable products with less scrap and improved dimensional tolerances. Each stage of the process is being investigated in detail, namely wax pattern production, ceramic shell production and performance, de-waxing (autoclaving) and metal casting. The research involves extensive experimental work combined with computer modelling. It is planned to derive rules which govern the processes which can then be used in the development of either analytical or rule-based software.The use of models incorporating fundamental behaviour at the major stages of the investment casting process will allow a significant improvement in its capability so that net shape castings can be produced routinely
  • Refractories for Investment Casting.
    Refractory materials play an important role in the production of investment cast components as the quality of the finished casting is directly dependent upon the performance of the ceramic shell moulds, ceramic foam filters and ceramic cores or inserts. Improvements in the quality of ceramic materials comes with a greater understanding of the fundamental physical, chemical and mechanical properties of basic systems. The research is carried out within a laboratory environment but closely replicates the conditions used in industry.
  • High Performance Cast Irons.
    The current research involves developing non destructive testing (NDT) to predict the properties of austempered ductile irons (ADI) so that end-users have greater confidence that the required properties have been achieved. The approach being used is to use ultrasonic velocity measurements to assess the graphite morphology and multi-frequency eddy current testing to assess the nature of the matrix. Multiple regression analysis is being used to derive algorithms which relate the tensile properties to the NDT measurements. To date, it has been found possible to predict proof and tensile strengths of both test bars and commercial castings to within ~10% of the actual values. Although not yet accurate enough to preclude the need for routine tensile testing, the ability to predict the properties of ADI castings with such a degree of certainty is nevertheless a significant step forward.

Recently Completed Projects

casting researchThese have included the following: 

Heat Treatment of Aluminium alloys.
Traditional heat treatments of aluminium castings involving a water quench seem designed to pre-stress the casting and thus contribute to the failure of the casting in service. Work has investigated other heat treatment methods to provide the required mechanical properties without introducing stresses or other adverse effects. It has been shown that ageing heat treatment of cast Al - 4.5 Cu - Ag alloys can produce tensile strengths of 500 MPa combined with a 10% elongation to failure.

Inoculation.
A number of projects have been carried out to study the role of inoculation on the mechanisms of the nucleation and growth of graphite in cast irons, particularly SG irons. Extensive metallography (mainly SEM) and computer modelling of phase diagrams has led to new insights into the complex sequence of events which occurs in molten iron during the spherodisation and inoculation treatments which ultimately control the structure and properties of these materials.

Titanium in cast irons.
An EC-funded CRAFT project has re-evaluated the effects of titanium (introduced from steel scrap) on the structure, properties and machinability of ductile irons, including Austempered Ductile Iron (ADI).

Flow defects in cast irons.
A detailed study of the flow of cast iron in greensand moulds using real-time radiography and computer modelling has recently been completed. This has established the causes of flow defects in commercial chilled grey iron castings.

Future Plans

  • Production of light weight TiAl valves for high efficiency engines
  • Net shape casting of TiAl components
  • Casting of burn resistant Ti alloys to net shape
  • Development of high strength ferrous and non ferrous alloys
  • Enhanced quality control of molten aluminium
  • Effect of mould filling on the reliability of cast irons