Production of ADI

herstellung-adi-1The production of ADI

 

The material ADI gains ist strength from a special form of heat-treatment. This heat-treatment process is shown in the following diagram:

 

A-B: Heating stage to 840-950° C
B-C: Austenitizing phase – soaking stage for the saturation of carbon by the austenite
C-D: Quick transfer to a salt bath
D-H: Ausferritizing by isothermal soaking between 250 – 400° Celsius after H: Cooling to room temperature.

herstellung-adi-2

The following diagram shows the hardening property of the material which is dependant upon temperature plotted against time:Abhängigkeit Durchhärtbarkeit im Temperatur – Zeit Diagramm

The cooling time can be extended for thicker components through the alloying with Cu, Ni and Mo, thus pushing the perlite peak to the right.

A sufficiently long soaking time in the ausferrite areas must be maintained so that the austenite can stabilize.

 

Requirements for the safe production of cast parts from ADI:

 

  • The alloy composition must be matched to the quenching conditions in the hardening shop – the most important influencing factor on this is the competence of the annealing shop and is command over the process!!
  • The decisive element for the establishment of the hardening parameters (e.g. its duration) is always the slowest area of a part to cool down. N.B.: Usually, but not always, also the thickest part!
  • A separate test bar is only of limited significance. Evidence of grain structure and properties (such as hardness or ductility) should be gained from the component itself.
  • The founder must adhere to his prescribed analysis.

metallurgische-grundlagen_1Metallurgical Fundamentals

 

When the mechanical properties have the same metallic base such as:

  • tensile strength
  • fatigue strength
  • ductile yield,
  • yield stress etc..

 

depend on the structure of the matrix present in the material.

This matrix structure is created by ADI heat-treatment. This assumes a good level of collaboration between the founder and the annealing shop. The analysis required is made according to the individual form of the component.

 

Only where the analysis is known and the form has been established can the desired hardness for the ausferritizing be given through the soaking time in the annealing shop.

 

… thus it may be ensured that the component reaches the required level of hardness.