Calcium Silicon Cored Wire Manufacturing and Wire Feeding Process

What Calcium Silicon Cored Wire Is

Calcium silicon cored wire, generally shortened to CaSi cored wire, is a treatment additive in wire form. A mild steel sheath is filled with calcium silicon alloy powder, the sheath is closed into a tube and coiled, and the finished coil is injected into molten iron or molten steel with a wire feeder. The point of putting the additive inside a wire is timing and placement: the calcium and silicon are delivered below the metal surface, at a chosen depth, in a controlled quantity per minute, instead of being thrown onto the bath where air and slag would consume most of the reactive elements before they could do their work.

Raw Materials for the Core

Two materials determine the behaviour of the finished wire: the alloy powder in the core and the steel strip that forms the sheath.

Component	Material	Function in the wire
Core	Calcium silicon alloy powder, typically in the Ca 28–32% and Si 55–62% range with the balance iron	Supplies the calcium for deoxidation, desulphurisation and inclusion modification, and the silicon for deoxidation and alloying
Sheath	Low carbon mild steel strip	Carries the powder through the feeder, protects it from the atmosphere, and dissolves into the bath once the wire is submerged

The core powder is screened to a controlled particle-size fraction. A fraction that is too coarse feeds unevenly and packs loosely, so the calcium delivered per metre of wire varies from coil to coil; a fraction that is too fine bridges in the dosing hopper and causes the filling weight to drift. The sheath must be ductile enough to be formed and closed without cracking, and low enough in carbon and residual elements that it does not upset the chemistry of the heat being treated.

Manufacturing Steps

Strip preparation. Cold rolled mild steel strip is slit to the width required for the finished wire diameter and cleaned so that the closure seam will form properly.

Forming. The strip is progressively roll formed into a U or open tube section, leaving a channel for the powder.

Filling. Calcium silicon powder is dosed into the open channel at a controlled rate so that the core weight per metre of wire is held within the specification.

Closing. The tube is closed and locked by roll forming, giving either a locked seam construction or a fully closed sheath depending on the wire design.

Sizing and coiling. The wire is drawn or sized to its final diameter, checked for a sound seam and even core, and coiled onto a carrier for shipment.

Inspection. Core weight per metre, wire diameter, sheath integrity and alloy chemistry are verified before the coil is released.

Core weight per metre is the controlling variable in the whole process. Two coils of the same diameter can behave completely differently in the ladle if one carries more alloy powder per metre than the other, because the treatment response depends on the mass of calcium and silicon actually delivered, not on the length of wire fed.

Wire Feeding in Ladle Treatment

The calcium silicon cored wire is used with the wire feeding method. The addition speed is set from the diameter of the wire and from the melting point of the wire material, so that the sheath melts at the intended depth rather than at the surface. The wire is fed vertically through a wire feeder and inserted smoothly into the molten iron or molten steel, where it melts at that ideal depth and the physicochemical reaction takes place inside the bath.

Working below the surface is what makes the process efficient. Calcium has a low boiling point and a strong affinity for oxygen and sulphur, and if it is released at the bath surface much of it burns or reports to the slag instead of the metal. By keeping the reaction submerged, the added elements are largely protected from reaction with the air and with the slag, and the proportion of the addition that ends up dissolved in the metal, the element yield, rises accordingly.

Why the Process Improves Cast Iron and Cast Steel

Higher and more repeatable element yield. Submerged injection keeps calcium and silicon in the metal instead of in the slag or the atmosphere.

Better desulphurisation and deoxidation. The calcium reacts with sulphur and oxygen in the bath, lowering sulphur content and reducing oxide inclusions.

Cleaner steel. Calcium treatment modifies the remaining inclusions into a form that resists clogging and improves castability, which matters most in continuously cast and thin section product.

Improved cast iron and cast steel quality. More consistent chemistry and cleaner metal translate into fewer rejects and more predictable mechanical results.

Lower cost per treated tonne. Because less of the addition is lost, the same treatment result is reached with less alloy, which reduces the cost of casting and steelmaking and improves the economics of the foundry or steel plant.

The process also suits automated operation. A wire feeder delivers a measured length at a controlled speed, so the treatment becomes a recorded quantity rather than an operator judgement, and the same result can be repeated heat after heat.

Quality Control and Storage

Incoming checks on a CaSi cored wire coil should cover the alloy chemistry of the core, the core weight per metre, the wire diameter and the integrity of the closure seam. Wire that has absorbed moisture should not be fed, because damp powder can sputter at the bath surface and disturb the feeding rate. Coils are therefore stored under cover on a dry floor, kept clear of standing water and of prolonged exposure to humid air, and used in rotation so that older stock is consumed first. Before a coil goes onto a feeder, a short run through the straightener should be made to confirm that the wire pays off without kinking or snagging.

Frequently Asked Questions

Q: What is calcium silicon cored wire?
It is a treatment additive made from calcium silicon alloy powder enclosed in a mild steel sheath, supplied as a coil and injected into molten metal with a wire feeder.

Q: Why is the additive put inside a wire instead of being added in bulk?
Because the sheath carries the reactive calcium below the metal surface, where it reacts with the bath rather than burning at the surface or reporting to the slag.

Q: What determines the wire feeding speed?
The speed is set from the diameter of the cored wire and the melting point of the wire material, so that melting occurs at the intended depth in the bath.

Q: What benefit does the process bring to cast iron and cast steel?
Submerged feeding raises the yield of the added elements, improves desulphurisation and deoxidation, and so improves the quality of the cast product while lowering the cost of the treatment.

Q: What is the most important quality parameter of the wire?
Core weight per metre. It decides how much calcium and silicon a given length of wire actually delivers, and it must be consistent from coil to coil.

Q: How should the wire be stored?
Under cover, on a dry floor, away from standing water and prolonged humid air, and consumed in rotation so that the oldest coils are fed first.