Software

Introduction

Our computer program is designed for calculating the solidification of steel castings and comes complete with an operating manual. This is a specialist program and some training may be required.

The software will operate on Windows 3.1 and Windows 9x.

A printer may be useful to print data but is not required.

Technical detail:

The programme works on the Modulus principles which are outlined on work carried out by N. Chvorinov (1940), R. Wlodawer (1966/67), J. Jamar (1975) and Ableidinger/Heine.

Since 1940, it has been theoretically possible to calculate the solidification times of castings by Chvorinov's method regardless of the type of casting and alloy.

Imagine a sphere which has stored a certain amount of heat in its volume (V).

Due to heat losses to the moulding sand via the surface (SA) of the sphere, it will finally solidify. Imagine further a thin plate of identical weight, i.e. a body with the same volume and the same stored heat. This plate will solidify significantly faster than the sphere, since this quantity of heat can be transmitted to the moulding sand over a much greater surface area. Chvorinov defined the ratio:

Modulus (cm) =

Volume (cm³) / Surface Area (cm²) transmitting heat

The calculation of the modulus can, of course, be carried out in any other arbitrary unit, e.g. in inches. It is noteworthy that the casting modulus represents a length which can be measured directly with a ruler when the geometrical relationships are known.

The larger the volume, the more heat is stored, the longer is the solidification period and the greater the modulus. The greater the surface area emitting heat, the smaller is the modulus and the shorter the solidification period.

The following formula shows the relationship between solidification period and modulus.

Solidification period T( min.) = M² k

Where k is a constant which amounts to about 2.1 for steel castings, when M is entered in cm .

If M is calculated in inches the constant amounts to 13.125 because of the change in units.

This constant applies for steel poured at about 15500C into silica sand. It will vary slightly with alloy, moulding material and temperature.

The essence of the modulus method consists in dividing the actual casting into basic geometric bodies and calculating the ratio volume/surface area for each basic body. Only the casting surfaces in contact with sand are included on the surface area. The contact surfaces of the basic body at which it joins other components of the casting are not included, since for long periods little or no cooling takes place at these surfaces.

Jamar first reported in 1975 that the modulus, as calculated by Chvorinov and Wlodawer is also effected by shape, so that a cube for example, has an approx. 35 % longer solidification time that a sphere with the same geometrical modulus.

The work of H. Ableidinger and Heine confirmed in principle these details of Jamar using large scale tests. For this reason the geometric modulus must be multiplied by a factor in order to be able to calculate the true solidification time. If the shape of the casting varied from zone to zone e.g. from cuboid to bar or to plate shaped, then the deviations in solidification time according to Jamar must definitely be taken into consideration.

Calculations which are included in the programme:

• Modulus and weight for bar, cylinders, tube, plate, cuboid, ring.
• Automatic corrections of modulus according to Jamar.
• The junction method of determining modulus which are included in Wlodawer's directional Solidification of Steel Castings 2nd Edition 1967 (German).
• Reducing modulus by using chills (surface and subsurface).
• Increasing modulus by using Isotherm tiles (surface and subsurface).
• The feeding and end-zone utilising radiographic standards. This enables the user to quickly establish the need for chills and or padding.
• Padding (reinforcement) to extend feeding zone.
• The liquid shrinkage and liquidus for any alloy.
• The liquid demand and automatic recalculation of feeder size.
• Feeders - open top - blind top - open side - blind side. Round or oval, insulated or sand. Modulus Extension Factor (M.E.F.) fully adjustable depending on insulation material used.
• Ring feeders and bar feeders insulated or sand.
• The feeder neck size (round or square).
• The topping powder weight.
• The ladle characteristics of customers individual ladles.
• The runner system flow rates.
• The ingate flow rates.
• The ingate fountain effect.
• The estimated temperature drop during pouring.
• The fill rate through critical sections.
  

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