Slab and beam blank moulds are built from copper mould plates — two broad faces and two narrow faces. Plates are expensive, so choosing the right copper and coating, and refurbishing at the right time, has a direct effect on cost per ton cast.
Why copper, and why an alloy
Copper conducts heat very well, which lets the mould pull heat out of the steel fast enough to form a strong shell. But pure copper softens at the temperatures seen at the meniscus. Alloying elements keep the copper strong and hard while losing only a little conductivity.
Cu-Cr-Zr
Copper-chromium-zirconium is the standard material for slab mould plates. After heat treatment it keeps high hardness and strength at working temperature, so the plates resist distortion, cracking and wear. Its conductivity is lower than silver-bearing copper but still very high. For most broad faces and narrow faces it is the right choice.
Cu-Ag
Silver-bearing copper has higher conductivity and better softening resistance than pure copper, but lower strength than Cu-Cr-Zr. It is used for some narrow faces and lower-load moulds, and is the usual material for billet mould tubes.
Coatings
- Nickel — protects the copper and is easy to apply in graded thickness.
- Nickel-cobalt / cobalt-nickel — harder and more wear-resistant than nickel, for the lower part of the mould where wear is highest.
- Graded or multi-layer coatings — thinner at the meniscus, where heat transfer matters most, and thicker at the bottom, where wear matters most.
The best coating depends on your casting speed, steel grades and how plates fail today: wear at the bottom, cracks at the meniscus, or coating peeling.
New plate or refurbishment?
Each refurbishment removes the old coating and a thin layer of copper, repairs damage, and re-coats the face. A plate can usually be refurbished several times before it reaches minimum thickness. When there is enough copper left, refurbishment costs much less than a new plate. When the plate is near minimum thickness or has deep cracks, a new plate is the better choice.
What to send for a quote
For new plates: the drawing number of each plate, length, width and thickness, copper grade, coating type and thickness, and quantity. For refurbishment: the drawing, the current thickness and photos of the face.
See our copper mould plates page, or send your drawings for a quote.