The MgO in slag is eroded usually by furnace lining while making steel. In the process of smelting, the slag and refractory materials will get touched; MgO concentration in slag should almost reach saturation. There is a close relationship between the content of saturated MgO and CaO/SiO2. For slag with low alkalinity (CaO/SiO2<2.0), the higher the proportion of FeO is, the lower proportion of saturated MgO. When FeO content is low and saturated MgO content is high, the slag will erode more refractories. While for slag with high alkalinity (CaO/SiO2 >2.0), the saturated MgO content will not be seriously affected by the FeO content, what’s more the slag will not erode much more refractories. Therefore, improve slag alkalinity can strongly protect refractories.
The service life of ladle is directly influenced by refining time, so it is important to improve steelmaking technology so that to shorten smelting time.
The service life of ladle will be reduced by 3-5 heats once shut down, so to achieve efficient production, the key is shortening smelting cycle. On the premise of using advanced technology to guarantee the best steel quality and the lowest total consumption, shorten the smelting cycle to the minimum, improve equipment and shorten shut down time.
With the expansion of the production scale of the grade steel, the automatic free -opening rate of the ladle will affect the smoothly running of production and quality of the slab. The quality of the products have been improved by analyzing the influential factors and adopting appropriate counter-measures, such as using flow guiding sand which also named stuffing sand
Flow Guiding Sand is a kind of ladle slide nozzle filler which is successfully developed by Yilong Refractory in recent years, results show that ladle castable success rate of automatic free-opening rate can reach above 95 percent. There is no metallic inclusion in ingot surface, is a kind of ideal ladle slide nozzle filler. Steel flow initiator contains metal mixture whose weight is heavier and melting point is lower than molten steel. Before pouring we put it into the upper nozzle, using it to burn and cause the molten steel within the upper nozzle will not be solidified, to achieve the purpose of automatic pouring and avoid the problem of ingot inclusions.
One research of Luoyang Research Institute of Refractory shows that the higher content of water in flow guiding sand, the lower compression strength of the sintered temperature product, the greater the apparent porosity, the smaller the bulk density, resulting the lower of ladle automatic opening and pouring rate.
Now magnesia-chromite brick, magnesia-dolomite brick, dolomite brick are the main products used for AOD lining.
There are natural dolomite at good quality in Europe, there calcined dolomite brick to are used generally to construct AOD lining. And magnesia-dolomite brick added with zirconia is used for tuyere, calcined dolomite brick with magnesia is used for slag line. For steel-tapping spout, magnesia carbon materials and magnesia dolomo carbon brick are widely used.
The corrosion resistance ability of magnesia chrome brick is high for high alkaline slag with magnesia and low alkaline residue with chrome, it’s the best choice for furnace whose slag composite changes are big, and it is widely used in Japan and America. While because magnesia chrome brick is expensive and chrome can do damage to the environment, so such kind of refractory brick is used less and less in the recent years. Only a small amount of small converters which don’ t work continuously use magnesia chrome brick.
Compared with the past magnesia chrome brick, dolomite brick is cheaper, but its serving life is also shorter.
Nowadays because magnesia calcium brick has good high-temperature resistance, slagging resistance and thermal shock resistance, and also it can purify molten steel. So it is gradually used in jumbo furnace which works continuously, and a trend of taking place of other refractory bricks seems to happen.
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