Calcium metal cored wire is widely used in the steelmaking production. Calcium treatment improves the quality of molten steel, and improve the quality of steel products.
The pure calcium wire is used as a deoxidizing agent, desulfurizing agent, and alloying agent. The calcium element can change the form and quantity of inclusions in steel, and effectively improve the castability in the process of aluminum-killed molten steel continuous casting, and solve the problem of nozzle blockage.
Background of Calcium Metal Cored Wire
Due to the low density, low melting point, and low boiling point of calcium metal, add to molten steel in the form of calcium lump, the oxidation burning loss rate is high, the yield is low, and the accuracy of composition control is poor.
In 1980’s, the calcium cored wire feeding method appeared. The calcium cored wire is wrapped by edge rolling. It is wrapped with steel strip on the outer layer, and filled with calcium metal granules or metal calcium wire inside. The calcium cored wire is fed into the molten steel through the wire feeder. In this way, the yield is high and the alloy composition is precisely controlled.
The manufacturer of calcium cored wire in general use the cold rolling low carbon steel strip to wrap the calcium powder (or mixed with iron powder). A few manufacturer of calcium metal cored wire used the cold rolling low carbon steel strip to wrap the pure calcium wire.
Technical Requirement for Calcium Metal Cored Wire
The calcium metal has great affinity with oxygen. It with low density, low melting and boiling point. There are special and strict requirements for the production of calcium metal cored wire.
- The purity of metal calcium should be high, and the higher the purity, the higher the adding efficiency.
- The chemical composition of calcium metal cored wire should be uniform.
- There is no air between the steel strip and the core wire to avoid oxidation of metal calcium.
- The cored wire should have a certain strength so that it can penetrate the slag on the surface of the molten steel and enter the bottom of the molten steel. The steel strip can reduce the burning loss of metal calcium, make the metal calcium and molten steel fully react, and improve the absorption rate of calcium.
The disadvantage of traditional calcium cored wire
At present, most of the calcium cored wire manufacturers use the pure calcium metal powder or calcium iron alloy powder as the core materials. There are voids between the calcium particles, which cause the adding amount of calcium metal uncontrolled.
The cored wire filled with calcium metal granules must be sealed, otherwise the calcium metal granules will leak, and oxidized easily.
The thickness of the steel strip of the cored wire is only 0.3-0.6mm, which leads to the poor strength of the cored wire filled with metal calcium granules. It starts to react when it enters the surface of the molten steel, and cannot reach the bottom of the molten steel. The reaction time between the calcium metal and the molten steel is short and the reaction is insufficient.
The Production Process of the High Purity Calcium Metal Cored Wire
In order to make up for the shortcoming of the traditional calcium cored wire. The technologists invented a new production process of high purity of calcium metal cored wire.
- The calcium metal refinement and casting process: The calcium metal is refined under vacuum environment and is cast into calcium metal rod (club).
- Calcium metal rod passivation process: The calcium metal is isolated from the air to avoid oxidation.
- The coating of steel strip: The inner side of steel strip is coating with high temperature gasification materials. According to the requirements of the product wire diameter to determine the diameter of pure calcium metal wire. The pure calcium metal wire was wrapped by steel strip, which is tightly welded in an anaerobic environment. While ensuring the sealing effect of the calcium cored wire, a preliminarily formed cored wire of sufficient length can be produced.
- Solid calcium cored wire producing process: Heat the preliminarily formed cored wire to temperature 230-1100℃ in a horizontal heating furnace, then enter the horizontal extruder for extrusion, and finally pull it into a finished cored wire to make a finished cored wire with a diameter of 7-16mm, strip steel thickness 1-2mm. The whole process is carried out in an anaerobic environment.
- The finished cored wire reheat treatment: In order to improve the strength of the cored wire, it should be reheat in anaerobic environment. After the reheat treatment, packing the finished cored wire product.
The new production method of high purity calcium metal cored wire make up the shortcoming of traditional calcium alloy cored wire. It is purer and stronger, and it can be used in the production of high quality steel such as continuous casting and rolling steel sheet, aluminum killed-steel, and special steel.