Capability
Foundry
Allard-Europe is equipped with 4 medium-frequency induction furnaces. This allows us to melt 37 tons at one time, but also gives us the necessary flexibility for customization in function of material selection and molds.
From design to casting
Sand molding is the start of the Foundry: a series of well-controlled steps to turn loose sand and a model into a mold into which liquid steel or white cast iron can be poured. Sand molding is the process of making a negative impression model of the part to be cast in chemically bonded molding sand. That sand is compacted in a molding box to form the mold.
We use silica sand as molding sand, and bind it with furan resin. For higher temperature resistance, we use chromite sand in some areas of the mold case. All the sand is neatly separated after casting and recovered for reuse.
The operators in the Foundry make the channels needed for the casting process:
- Pouting channels to let the steel in
- Risers/feeders to compensate for shrinkage during solidification
- Venting channels so that gases can escape
Cores are used for hollow spaces in the casting, executed in molding sand, ceratec or ceramic. These are placed in the mold before the mold is closed.
Cope and drag of the molding box are placed on top of each other, accurately aligned and secured.
What are the pitfalls?
Because steel forms are so heavily stressed by heat and flow, one must:
- Use special sand mixtures
- Apply coatings correctly
- Accurately compact the molding sand in the mold
- Perfectly plan venting
- Position and support cores accurately
The art of casting
Casting steel or white iron castings is true craftsmanship because they are one of the most difficult and demanding metals to cast. The process requires a combination of material knowledge, experience, process control, ability to interpret and dexterity that you cannot replace with just machines or standard procedures.
The choice of materials determines the recipe of the metals that enter the smelter(s). The composition of the input is carefully monitored and controlled. The melt is then poured into a ladle that is brought above the mold box.
Allard-Europe masters various casting techniques to obtain the most homogeneous structure possible from the casting and avoid possible casting errors:
- Use of vortex funnels
- Use of shrouds
- Use of casting trays
On fire
Pouring with the correct pouring temperature is a crucial part of the casting process for steel and white cast iron. The temperature, determined from experience and simulation, determines:
- The flow ability (how well the mold fills)
- Solification and thus the risk of defects
- The microstructure (especially in white cast iron)
- Oxidation, inclusions and mold damage
Cool down
Once the liquid steel is poured into the sand mold, the solidification and cooling process begins. This happens in the closed mold. Slow cooling occurs through the sand – which is a poor conductor of heat – which prevents cracking. This also minimizes residual stresses and allows the micro-structure inside the casting to develop normally.
Larger castings require days to weeks to cool sufficiently. On the other hand, some castings (e.g., in duplex) will need to be shaken out quickly to accelerate cooling.
When the casting has cooled and solidified sufficiently, it should be removed from the sand mold. The entire mold is placed in a vibrating chute or crusher. The vibrations cause the sand mold to collapse and the sand falls through a grid. The cast is left behind on the vibrator.
