Chinese FOB Prices of Silicon Calcium Cored Wire: Ca30Si60 and Ca28Si55
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What the February 1 Offer Sheet Quotes
The price sheet released by Chinese cored wire producers on February 1 covers two silicon calcium wire specifications, both with a nominal diameter of 13 mm and both quoted on an FOB China basis in US dollars per tonne. The quoted ranges are 1650 to 1750 USD per tonne for the Ca30Si60 index and 1500 to 1600 USD per tonne for the Ca28Si55 index. The two indexes differ mainly in the calcium and silicon content of the powder fill, which is what drives the gap of roughly 150 USD per tonne between them. Buyers comparing the two figures should also weigh the wire diameter, sheath thickness and fill weight, because a lighter fill per metre lowers the unit price but also lowers the calcium delivered per metre of wire.
Silicon Calcium Cored Wire Prices on February 1
| Index | Price range (USD/tonne, FOB) | Remarks |
|---|---|---|
| Ca30Si60 φ13 mm | 1650 – 1750 | FOB China |
| Ca28Si55 φ13 mm | 1500 – 1600 | FOB China |
In the index notation, Ca30Si60 denotes approximately 30 % calcium and 60 % silicon in the powder fill, and Ca28Si55 denotes approximately 28 % calcium and 55 % silicon. Iron and carbon are kept low in both fills so that the wire can be fed into aluminium-killed or low-carbon steels without adding harmful residuals.
Why Calcium Is Fed as Cored Wire
Calcium has a very low boiling point and a strong affinity for oxygen, sulphur and alumina, so adding it loose to a ladle gives poor and unpredictable recovery. Wrapping the powder in a steel sheath and injecting it below the slag at a controlled speed places the calcium in the deep part of the melt, where it dissolves and reacts before it can float out. The three jobs it performs are deoxidation of residual oxygen, desulphurisation of the steel, and modification of solid alumina inclusions into calcium aluminate phases that stay liquid at steelmaking temperatures, which reduces clogging of submerged entry nozzles during continuous casting.
Wire Construction and Diameter Control
A silicon calcium cored wire is built from a low-carbon steel strip folded into a tube and filled with crushed calcium silicon powder. For the 13 mm specification quoted on this sheet, diameter tolerance, sheath thickness and powder fill ratio are the three parameters that determine how the wire behaves in the feeder. The sheath provides mechanical strength and shields the powder during injection; the fill carries the active chemistry. Fill ratio is stated per coil on the packing list so that the buyer can compare the actual kilograms of calcium silicon purchased, not just the price per tonne of wire.
Choosing Between Ca30Si60 and Ca28Si55
Heat size and sulphur target: heavier heats or tighter sulphur specifications favour the higher calcium fill for fewer metres of wire.
Steel grade: low-carbon and interstitial-free grades favour a low-carbon sheath and a clean fill with minimal carbon pickup.
Feeder capability: the injection speed and guide tube diameter must match the wire type, so the machine limits should be checked first.
Coil weight and handling: coil mass affects spool change frequency and the number of joints in long casting sequences.
Certification: a mill certificate stating the chemical composition of the powder fill should accompany each lot.
Feeding Practice and Recovery
Recovery depends more on feeding practice than on the wire itself. The wire should enter the melt below the slag layer at a steady rate, with the ladle already deoxidised so that the calcium is not consumed by free oxygen. Holding and stirring after injection allow the calcium aluminate inclusions to grow and float into the slag, so a short argon stir after feeding usually improves the result. Feed rate, injection depth and stir time are set for each steel grade and ladle size, and a trial heat is the normal way to fix those parameters before a full casting sequence is committed.
Frequently Asked Questions
Q: What do Ca30Si60 and Ca28Si55 mean in the price sheet?
They are the two indexes quoted: approximately 30 % Ca with 60 % Si, and approximately 28 % Ca with 55 % Si in the powder fill.
Q: What was the FOB China price of 13 mm silicon calcium cored wire on February 1?
The sheet quoted 1650 to 1750 USD per tonne for Ca30Si60 and 1500 to 1600 USD per tonne for Ca28Si55.
Q: Why is the 13 mm diameter so widely used?
It is a practical compromise: thick enough to hold fill weight and reach below the slag, thin enough for standard wire feeders to inject at controlled speed.
Q: How does cored wire improve calcium recovery compared with loose additions?
Injecting the powder below the slag keeps the calcium in the deep melt, so less is lost by flotation and oxidation before it reacts.
Q: What does the wire do to inclusions?
It modifies solid alumina into liquid calcium aluminate phases that resist clogging and can be floated out into the slag.
Q: Which data should be checked against a certificate for each lot?
Powder fill chemistry, calcium and silicon content, wire diameter, sheath thickness, fill ratio per metre and coil weight.
