Description

Introduction

Pig iron is usually divided into steel pig iron, casting pig iron, alloy pig iron according to different uses. Steel is divided into carbon steel and alloy steel according to different components. Alloy steel is on the basis of carbon steel, in order to improve or obtain some properties and deliberately add an appropriate amount of one or more elements of steel, there are many types of elements added to steel, mainly chromium, manganese, vanadium, titanium, nickel, molybdenum, silicon. In addition, iron ore is also used as catalyst for synthesis of ammonia (pure magnetite), natural mineral pigments (hematite, vitarite, limonite), feed additives (magnetite, hematite, limonite) and precious medicinal stone (magnet), but the amount is small. Iron and steel products are widely used in all sectors of the national economy and all aspects of people’s life. They are essential basic materials for social production and public life. Since the invention of the converter steelmaking process in the mid-19th century, steel has been the most important structural material, occupies a very important position in the national economy, is an important pillar industry of social development, is the most important and most used metal material in modern industry. Therefore, people often take steel, steel output, variety, quality as a measure of a country’s industry, agriculture, national defense and science and technology development level of an important symbol.

Classification

There are a wide variety of iron ore species. About 300 kinds of iron minerals and iron-bearing minerals have been discovered, among which more than 170 kinds are common. However, under the current technical conditions, the industrial utilization value is mainly magnetite, hematite, magnehematite, ilmenite, limonite and siderite.
Our iron ore resources are many but not rich, mainly middle and low grade ore, rich ore resource reserves of 1.8%, while poor ore reserves of 47.6%. There are more medium and small mines, fewer large ones, and even fewer large ones. The ore type is complex, refractory to beneficiation and the proportion of multi – component ore is significant. The reserves of refractory hematite and multi-component symbiotic iron ore account for 1/3 of the total reserves in China, and the common (associated) biological components mainly include more than 30 kinds of V, Ti, Cu, Pb, Zn, Co, Nb, Se, Sb, W, Sn, Mo, Au, Ag, S and rare earth elements. The most important ones are Ti, V, Nb, Cu, Co, S and rare earth elements. The economic value of some cobiological components even exceeds that of iron ore. For example, Bayan Obo iron ore contains abundant REO, Ta and Nb. The reserves of V and Ti in Panzhihua vanado-ilmenite rank first in the world. With the improvement of separation and application technology, these cobiological components will be fully recovered comprehensively. Some useful components of red ore have fine distribution size, or are closely embedded with harmful components, so it is difficult to separate and recover, resulting in low recovery rate of iron ore beneficiation, and a large number of useful components are lost to tailings. Some magnetite deposits are mainly of middle and low grade, but easy to be mined and selected. There are a large number of low grade ores with marginal benefits in them. If there are appropriate economic stimulus policies, they can also be fully exploited and utilized

Magnetite

The main component is Fe3O4, that is, Fe3O4, each Fe3O4 molecule has two +3 valence iron atoms and 1 +2 valence iron atoms, that is, Fe2O3-FeO, oxygen atom is -2, in which the mass fraction of Fe is about 72.3597945571%. Equiaxed system. Single crystals are often octahedral and less often rhombic dodecahedral. On a diamond decahedral surface, the long diagonal direction is often striped. The aggregate is mostly dense block and granular. Color is iron black, streaks are black, semi-metallic luster, opaque. Hardness 5.5~6.5. Specific gravity is 4.9~5.2. It has strong magnetism.In magnetite, a considerable amount of Ti4+ is often substituted for Fe3+ by similar isotropy, and Mg2+ and V3+ are also substituted for Fe2+ and Fe3+, thus forming some mineral subspecies, namely:

(1) titano-magnetite Fe2+(2+x)Fe3+(2-2x)TixO4(0< x< 1), containing TiO212%~16%. At room temperature, titanium is separated into plate – and columnar ilmenite and cloth – grained ilmenite.
(2) vanadium magnetite FeV2O4 or Fe2+(Fe3+V)O4, containing V2O5 sometimes as high as 68.41%~72.04%.
(3) vanado-titanomagnetite is the solid solution product of the above two minerals with more complex composition.
(4) chromium magnetite contains Cr2O3 up to a few percent.
(5) The MgO content of magnesium magnetite can reach 6.01%

Magnetite is the main mineral of iron ore in magmatic ore deposits, contact metasomatism hydrothermal ore deposits, sedimentary metamorphic iron deposits, and a series of iron ore deposits associated with volcanism. In addition, it is also common in placer deposits.

Magnetite can be oxidized into hematite (pseudohematite and limonite), but it still retains its original crystalline form.

Hematite

The main component of hematite is Fe2O3, that is, iron oxide. In nature, there are two kinds of homogeneous polyimage Fe2O3, namely α-Fe2O3 and γ-Fe2O3, in which Fe mass fraction is about 69.9433034300%. The former is stable under natural conditions and is called hematite; The latter is not as stable as α-Fe2O3 under natural conditions, in a metastable state, known as magnehematite.
It often contains homomorphic compounds Ti, Al, Mn, Fe2+, Ca, Mg and a small amount of Ga and Co. Tripartite system with rare intact crystals. The crystalline hematite is steel gray and cryptocrystalline. Earthy hematite is red in color. Streaks are cherry red or fresh pork liver color. Metallic to semi-metallic luster. Sometimes the luster is dull. Hardness 5~6. The specific gravity is 5~5.3.
Aggregates of hematite come in various forms, forming some mineral subspecies, namely:
(1) Specularite is a collection of rosette or flake hematite with metallic luster.
(2) mica hematite crystalline fine scaly hematite with metallic luster.
(3) oolitic or nephritic hematite an oolitic or nephritic hematite.
Hematite is one of the iron minerals widely distributed in nature. It can be formed in various geological processes, but mainly in hydrothermal processes, sedimentary processes and regional metamorphism. In the oxidation zone, hematite can be formed from limonite, fibritite and goethite by dehydration. But can also become goethite and water hematite, etc. Under reduction conditions, hematite can be converted to magnetite, which is called pseudo magnetite.

Magnehematite

γ-Fe2O3, its chemical composition often contains Mg, Ti and Mn mixtures. Equiaxed, pentagonal tritetrahedral crystals, mostly granular aggregate, dense massive, often with magnetite illusion. Color and stripes are brown, hardness 5, specific gravity 4.88, strong magnetic.
Magnehematite is mainly formed by secondary changes of magnetite under oxidation conditions. Fe2+ in magnetite is completely replaced by Fe3+ (3Fe2+→2Fe3+), so the octahedral site occupied by 1/3Fe2+ is vacant. In addition, magnehematite may be formed by the loss of water from fibritite, or by the organic action of iron oxides.

limonite

In fact, it is not a mineral species, but a mixture of goethite, fibritite, hydrogoethite, fibritite, and water-containing silicon oxide, argillite, etc. The change of chemical composition is large, so is the change of water content.

Iron ore distribution
(1) goethite α-FeO(OH), containing 62.9% Fe. Containing no quantitative adsorption of water, said water goethite HFeO2·NH2O. Rhombic system, needle, columnar, sheet, or scaly. It is usually piniform, nephriform, or stalactiform. Cut mask parallel or radial fibrous structure. Sometimes form dense massive, soil – like, but also oolitic. Color red brown, dark brown to black brown. After weathering into powder, ochre – like limonite is yellowish brown. Goethite stripe is reddish-brown, hardness 5~5.5, specific gravity 4~4.3. The limonite striation is generally light brown or yellowish brown, hardness 1~4, specific gravity 3.3~4.
(2) gamma-Feo (OH), containing Fe 62.9%. The adsorbed water containing no quantity is called FeO(OH)·NH2O. Rhombic system. Common scaly or fibrous aggregates. Color dark red to black red. Streaks are orange or brick red. Hardness 4~5, specific gravity 4.01~4.1.

Iron ore classification

Iron ore can be divided into natural type and industrial type according to the characteristics of mineral composition, structure, structure and mining, separation, metallurgy and technological flow.

1. Natural types
1) According to the iron-bearing species, it can be divided into: magnet ore, hematite, pseudo-or semi-pseudo-hematite, vanadite-titanium magnet ore, limonite, siderite and mixed ore composed of two or more kinds of iron-bearing minerals.
2) According to the content of harmful impurities (S, P, Cu, Pb, Zn, V, Ti, Co, Ni, Sn, F, As), it can be divided into high sulfur iron ore, low sulfur iron ore, high phosphorus iron ore, low phosphorus iron ore, etc.
3) According to structure and structure, it can be divided into disseminated ore, net vein disseminated ore, striated ore, banded ore, dense massive ore, brecciform ore, as well as oolitic, bean, kidney, honeycomb, powdery, earthy ore, etc.
4) According to gangue minerals, it can be divided into quartz type, amphibole type, pyroxene type, plagioclase type, sericite chlorite type, skarn type, actinite type, serpentine type, iron dolomite type and jasper type iron ore.

2. Type of industry
1) Industrial available iron ore, that is, table iron ore, including iron ore for steel, iron ore for iron, optional iron ore.
2) Iron ore temporarily unavailable for industrial use, i.e. off-balance sheet iron ore, has an iron content between the lowest industrial grade and the boundary grade.

Industrial quality requirement
1. Iron ore for steelmaking (formerly known as open-hearth rich ore)
Ore lumpiness requirement:
Iron ore for open hearth 50~250 mm;
Iron ore for electric furnace 50~100 mm;
Converter iron ore 10~50 mm.
Quality of ore directly used in steelmaking (suitable for magnet ore, hematite, limonite).

2. Iron ore for ironmaking (formerly known as blast furnace bonanza)
Ore lumpiness requirements: generally 8~40mm.
Iron ore used in iron making can be divided into: according to the pH of slag-making components:
Alkaline ore (CaO+MgO)/(SiO2+Al2O3)> 1.2;
Self-fusible ore (CaO+MgO)/(SiO2+Al2O3)=0.8~1.2;
Semi-self-fusible ore (CaO+MgO)/(SiO2+Al2O3)=0.5~0.8;
Acid ore (CaO+MgO)/(SiO2+Al2O3)< 0.5.
Acid converter steelmaking pig iron ore P≤0.03%
Basic open hearth steelmaking pig iron ore P≤0.03%~0.18%
The pig iron ore P≤0.2%~0.8% in basic side-blown converter steelmaking
Thomas pig iron ore P≤0.8%~1.2%
Common cast pig iron ore P≤0.05%~0.15%
High phosphorus cast pig iron ore P≤0.15%~0.6%

3.Selected iron ore
For ore with low iron content or high iron content but harmful impurity content exceeding the specified requirements or iron ore with associated beneficial components, it is necessary to carry out beneficiation treatment, and the selected iron concentrate powder can be used in the furnace after batching sintering or pellet treatment.
Requirements for ore to be processed:
Magnet ore TFe≥25%, mFe≥20%;
Hematite TFe≥ 28%-30%;
Siderite TFe≥25%; Limonite TFe≥30%.
The classification of industrial types of ores to be selected is usually based on a single low intensity magnetic separation process, using magnetic iron share to classify. According to our country mine production experience, the general standard is:
Ore type mFe/TFe(%)
Single low intensity magnetic separation ore ≥65
Ore separation by other processes. 65
Another classification standard can also be used for magnet ore and hematite:
mFe/TFe≥85 magnet ore
mFe/TFe85~15 mixed ore
mFe/TFe≤15 hematite

The magnetite supplied by our company is as follows:

Thehematite supplied by our company is as follows: