In the past 20 years, due to the rapid development of China's iron and steel industry, ore mining has not kept pace with the development of the iron and steel industry, and the output and quality of iron ore cannot meet the needs of steel production, which has caused the number of China's iron ore imports to increase year by year.
China's iron ore is characterized by its scattered distribution, small reserves, and low grade of raw ore. Lean ore accounts for more than 80% of the total iron ore reserves. The reserves of ore resources are about 40 billion tons, of which more than 20 billion tons can be exploited, and more than 8 billion tons can reach economic scale. According to the current mining scale, it can be mined for about 40 years, and the output cannot meet the needs of the rapid growth of China's steel. At present, the largest mining area in China is the Anshan mining area in the northeast.
The mechanical strength of an ore refers to the ability of the ore to resist impact, friction and extrusion. It strives to be stronger in order to avoid the increase in the amount of dust in the smelting process that affects the air permeability of the blast furnace. It should be pointed out that the above refers to the strength at room temperature and does not reflect the actual situation in the blast furnace. The mechanical strength of varieties of iron ore at high temperature needs further research.
The softening properties of iron ore include two aspects: the softening temperature and the softening temperature range of iron ore. Softening temperature refers to the temperature at which iron ore begins to deform when heated under a certain load; The softening temperature range refers to the temperature range where the ore starts to soften to the end of softening. Blast furnace smelting requires a high softening temperature of iron ore and a narrow softening temperature range.
The various physical and chemical indicators of iron ore remain relatively stable in order to maximize production efficiency. Among the aforementioned indicators, the stability of ore grade, gangue composition and quantity, and content of harmful impurities is particularly important. Blast furnace smelting requires composition fluctuation range: iron-containing raw material (TFe)<±0.5%～1.0%; (S, q)<±0.2%～0.3%; basicity of sinter is ±0.03-0.1. In order to ensure the stability of the composition of the ore, it is also very necessary to strengthen the whole grain and mixing of the original branch.