Characteristics of seamless metal calcium wire calcium treatment
The characteristics of seamless metal calcium wire calcium treatment are divided into four points. Next, Xiaobian will explain to you what it is.
1. Metallurgical properties of calcium: Basic characteristics: Melting point is 850℃, boiling point is 1480℃, density is 1.55g/cm3, melting degree in molten steel is close to zero, it has a greater affinity for oxygen, and liquid calcium can dissolve Al2O3 inclusions. The Al2O3 in molten steel is treated with calcium to form large liquid inclusions, which are easier to float. It reduces the blockage of the nozzle caused by excessive Al2O3 in the molten steel, and improves the pouring properties of the molten steel. After calcium treatment, the Al2O3 inclusions remain spherical and improve the performance after rolling.
2. The treatment effect of calcium on molten steel: calcium is added to the molten steel, and part of it is dissolved on the liquid steel to become dissolved calcium in the steel; part of it is evaporated in the form of steam; part of it reacts with Al2O3 inclusions or S in the steel to form impurities. During the refining and continuous casting process after the treatment, such impurities float into the slag, and the remaining part remains in the steel to become inclusions. Denaturation treatment of inclusions: Al2O3 becomes CaO-Al2O3 or CaO-Al2O3-CaS; CaS becomes CaOAl2O3-CaS. Can effectively change the fluidity of molten steel. Save the use of alloys and other deoxygenated and desulfurized substances, and save smelting costs.
3. The process principle and effect of seamless calcium wire (high calcium wire): The condition of inclusions in molten steel is related to the amount of calcium added, the time of addition, and the speed of addition. Speed: Unsuitable feeding line speed, low calcium absorption rate, calcium is evaporated; suitable speed, high calcium absorption rate, less calcium evaporation. Time: After feeding the calcium line, samples were taken immediately, and the impurities in the steel changed significantly. Most of them were converted into CaO-Al2O3-CaS inclusions. The size was small and the shape was close to spherical, but it was not completely spheroidized. Sampling in the crystallizer, most of the inclusions become CaO-Al2O3 inclusions, forming a spherical shape, and the CaS content is low. CaO, Al2O3, CaS, and Ca are all lower than when the wire was first fed. When sampling in the billet, the inclusions change again and become CaO-Al2O3-CaS inclusions. The shape is no longer spherical, and the size is slightly larger than in the crystallizer. This is because when the steel solidifies, S is isolated and reacts with calcium to generate CaS, which polymerizes with the inclusions and increases in size.The Al and O in the molten steel react, and the inclusions expand again. Calcium feeding amount: The amount of the feeding line (CaSi line) should be sufficient to form 12CaO7 Al2O3. At the same time, the loss should be considered. It is generally believed that the residual calcium content in the steel after the feeding line is 30-40ppm. The calcium denaturation treatment of silicon-calcium wire, calcium-iron wire, aluminum-calcium wire, and pure calcium wire will also be very different.The content of residual calcium in molten steel is also an important indicator of calcium treatment in molten steel. When the mass fraction of acid-melted aluminum is 0.02-0.05%, the residual calcium mass fraction is 29ppm and the Ca/Al is 0.058-0.145. The test results show that W(Ca)/W(Al): 0.13-0.20 is the best, and the general silicon calcium wire dosage is 0.9kg/ton of steel.
4. After feeding the seamless calcium wire (high calcium wire), the composition of the inclusions and the content of S and O in the steel: S≤10*10-4% in the steel: CaO-Al2O3-CaS or CaO-Al2O3-CaS-MgO formed in the steel. When S≥30*10-4% in steel, CaS is formed in steel, and the original O content in steel is high, then the CaO formed by Ca and O, the feeding line should be selected at the end of the de-O treatment.
