(2) Fluorite gangue iron concentrate sinter    The gun spar (3CaO•2SiO 2 •CaF 2 ) is a compound unique to the fluorine-containing slag and is located at the point A of the C 3 S 2 -CaF 2 cross-section in the ternary phase diagram CaO-SiO 2 -CaF 2 , see Figure 4 its molecular basicity of 1.5, alkalinity of 1.4 mass, which is a high-melting phase. According to the literature , F 2 , HF and SiF 4 are all volatile gases. Some people think that the instability of gun spar causes the slag skin to fall off, which is the main reason for the damage of the steel lining and the tuyere. However, for sintering, the fluorite containing fluorite gangue has a lower temperature in the liquid phase formation. When the sintering temperature reaches above 1450% , a volatile gas is generated, but during the condensation process, most of the fluorine-containing minerals still Gun spar minerals precipitated. From the differential thermal curve of the synthetic gunite ( Fig. 5), it can be seen that no phase change point was found before melting. Therefore, gun spar is a relatively stable mineral.    The structure of the gun spar is Ca 4 Si 2 O    With the increase of carbon content, titanium magnetite and perovskite have increased, and titanium hematite and calcium ferrite have decreased. Other Plastic Injection Machine Tooth Brush Injection Molding Machine,Toothbrush Injection Molding Machines,Toothbrush Injection Molding Machinery BOLE INTELLIGENT MACHINERY CO., LTD , https://www.bolemachinery.com
   China's Baotou magnetic concentrate ore is of this type. The concentrate is characterized by low silica in the gangue and mainly in the form of silicates, with a certain amount of fluorite and rare earth minerals. Its mineral composition and microstructure are characterized as follows.
   The main minerals of self-fluxing sinter are magnetite, hematite and floating soil. The binder phase minerals are mainly gunite (3CaO•2SiO 2 •CaF 2 ) , vitreous and a small amount of fluorite and ferric acid-calcium. (CaO•Fe 2 O 3 ) , ferric acid hemi-calcium (CaO•2Fe 2 O 3 ), followed by a very small amount of calcium fayalite, strontium calcium silica (R 0.356 • Ca 0.299 • Si 0.361 • O 1.565 ) , residual Lime and beta -type calcium orthosilicate. The total amount of binder phase is about 20 to 25%.
The magnetite grains in the sinter are dense, mostly semi-self-crystal or other crystal. The grain size is small, the phase between the grains is small, and there is a local phenomenon of magnetite. The microstructure is poor in uniformity and often has a non-uniform granular structure. There are many micropores in the magnetite grains and grains, so there are more secondary hematite and ferric acid semi-calcium. The mineral composition of the fluorite gangue iron concentrate sinter is:
(1) The self-fluxing sintered ore binder phase is mainly gunite, and the quartz gangue self-fluxing sintered ore binder phase is mainly calcium iron olivine.
(2) In addition to the gunite in the binder phase, there are a small amount of fluorite, ferric acid semi-calcium and rare earth minerals. Ferric acid hemi-calcium (CaO•2Fe 2 O 3 ) is a unique mineral of low-silicon self-fluxing sinter. Due to the low quartz content in the concentrate, the lime in the self-fluxing sinter is also relatively reduced, and the gun spar takes calcium oxide, resulting in ferric acid hemi-calcium.
(3) There is very little residual lime in the binder phase. Because the gunite takes calcium oxide , the content of β -type orthosilicate and calcium olivine is less, and the calcium fluoride has low liquid viscosity and good fluidity. Digested lime, so limestone white spots are rarely seen in such sinter.
(4) The magnetite grains are dense, the binder phase is small, and the iron mineral and the binder phase are uneven granular structure. The quartz gangue self-fluxing sinter has a high bonding phase, and the iron minerals are mostly island-shaped, which are more evenly distributed in the binder phase and have a granular structure. From the macroscopic structure, the sinter loose porous thin-walled structure has poor strength, especially the drop strength is poor, and there are many granules.
   The research by the joint experimental group of Baotou Iron and Steel Company and Beijing Iron and Steel Institute shows that this structure is mainly due to the fact that the sinter liquid contains calcium fluoride, which reduces the viscosity and surface tension of the liquid phase, resulting in a loose porous thin wall of the sintered ore. structure. Tests and demonstrated with 10% SiO 2 having a high or increased slag basicity of sintered ore to reduce the content of the sinter cuspidine, can increase the viscosity and surface tension of the liquid phase of the sinter thickened liquid, liquid The phasor is increased, so that the structure of the sinter is changed from a porous thin wall to a mesoporous thick wall, which increases the strength. 
   When the alkalinity is between 0.6 and 1.5 , the magnetite is mostly coarse and shaped, and the structure of the magnetite has micropores and cracks, and the amount of bonded phase between the grains is small. The binder phase is mainly gunite and glass phase, and the fluorite is distributed in the binder phase. As the alkalinity increases, the glass phase gradually decreases from 10.5% to 2.5%, and the gunite increases from 12.5% to 26%, which is the main cement phase in the alkalinity. Since the compressive strength of the glass phase and the spar is very low, the sinter has a low drum index. [next]
   When the basicity is increased from 1.6 to 2.4 , the magnetite is mostly semi-automorphic and its crystal, forming an aerobic structure and an interlaced network structure with calcium ferrite. The so-called ablation structure is that magnetite is mostly etched into residual crystals or semi-automorphic crystals by calcium ferrite. Magnetite and calcium ferrite are tightly connected, which promotes the contact between calcium ferrite and magnetite. And with large friction, the crystal form must be inlaid firmly. The so-called interlaced network structure is ferric acid monocalcium and ferric acid hemi-calcium, which are hair-like, needle-like, column-like cross-section and closely intertwined, so that the microstructure network is integrated. On the other hand, calcium ferrite is also in the form of a strip-like, hair-like structure with the gun spar, which strengthens the consolidation of the gun spar. When the alkalinity reaches 2.0 , the calcium ferrite mineral reaches 20%, and the strength of the sintered ore is remarkably improved. Due to the great changes in the mineral composition and microstructure of the sinter, the quality of the high alkalinity sinter containing fluorite gangue has also undergone a fundamental change.
  (III) Vanadium- titanium magnet concentrate ore sinter
   The mineral composition of the sinter contains iron magnetite (Fe 3 O 4 SS), titanium hematite (Fe 2 O 3 SS), gangue ore with perovskite, calcium ferrite, and diopside. , calcium silicate and glass, etc. With the increase of alkalinity, both titanomagnetite and titanium hematite solid solution are reduced, among which titanium hematite is reduced more, perovskite and calcium ferrite are increased, and vitreous is relatively reduced. Figure 6 shows the change in the composition of each mineral as a function of alkalinity.
   The vanadium-titanium magnetite sinter is characterized in that the titanomagnetite is a silicate glass phase and a small amount of calcium ferrite and a portion of the titanium hematite crystal are consolidated. Its microstructure is characterized by fine mineral grains, titanium hematite, glass phase, perovskite content, less calcium ferrite, and occasionally dicalcium silicate.
   The melting point of perovskite is
   Titanium Pangang sinter hematite (alkalinity 1.75), the content of 30%, compared with the normal content of hematite basicity of sintered ore with 10% disparities. The biopsy of the sintered cup shows that the titanium hematite is mainly formed by reoxidation. Since titanium hematite dissolves many elements such as titanium, oxidation is apt to occur. In addition, there is more crystallized titanium hematite in the place where the melt is concentrated. It is rapidly cooled and crystallized from the high temperature and high viscosity melt, and has a high performance of low temperature reduction and pulverization of the sintered ore. Impact. [next]
 (Iv) high aluminum gangue self-fluxing sintered ore
   The iron-bearing minerals of the sinter are magnetite, floating soil, and secondary hematite, and the native hematite and magnetite in the concentrate appear during low-carbon sintering. In the production of self-fluxing sinter, magnetite forms a solid solution with iron spinel (FeO•Al 2 O 3 ) . In the binder phase appears silicate, aluminum melilite (2CaO • Al 2 O 3 • SiO 2) and it akermanite (2CaO • MgO • 2SiO 2) a solid solution, Jiaohuang feldspar. In addition, there are calcium fayaite, calciteite (CaO•FeO•2SiO 2 ), Mengsan oblique pyroxene (CaO•2(Fe, Mn, Mg)0•3SiO 2 ), variegated pyroxene (Ca• Mg)O•(Mg•Fe)O•2SiO 2 ). The latter is a pyroxene like the pyrite pyroxene, and its composition is between diopside [(CaO•MgO•2SiO 2 or CaMgSi 2 O 6 ) And the oblique enstatite (between MgO•SiO 2 or Mg 2 (Si 2 O 2 ) , the phase composition was found to be Ca 1.12 (Fe 0.85 , Mg 0.35 ) by means of an electron probe when studying high-aluminum self-fluxing sintered ore. ) (Si 1.6 Al 0.32 )O 6.16 .
The characteristics of the mineral composition of the high-aluminum gangue sinter mineral indicate that when the sinter contains no Al 2 O 3 , the calcium silicate is formed when the sintering alkalinity is greater than 0.5 . C 2 S occurs when the sinter contains Al 2 O 3 4.5% alkalinity greater than 0.9 or Al 2 O 3 7% alkalinity 1.3 to 1.4 . This characteristic of alumina gangue sinter is beneficial to improve sinter strength.
   Quartz gangue hematite with addition of lime and bauxite (Al 2 O 3 • 2H 2 O) tests showed: 1.18 found no basicity calcium silicate, calcium iron olivine binder phase is predominantly elastically Wax (2CaO•Al 2 O 3 •SiO 2 ), fayalite, ferrite and aluminum ferrite. As Al 2 O 3 increases in the sinter, the dicalcium ferrite decreases. In the sinter with less than 7% Al 2 O 3 , there is only ferric-calcium ferrite, and there is a complex ferrite (CaO•FeO•xFe 2 O 3 and 3CaO•FeO•7Fe 2 O 3 ), calcium aluminophosphate. 3 7 ~ 12% Al 2 O, mainly 4CaO • Al 2 O 3 • Fe 2 O 3, when the Al 2 O 3 12%, occurred CaO • Al 2 O 3 • 2Fe 2 O 3. In The silicate binder phase of the high aluminosilicate contains more aluminum feldspar, as well as iron-magnesium stellite and cordierite H 2 (MgFe) 4 Al 8 Si 10 O 37 . Therefore, after adding Al 2 O 3 , sintering The composition of the final structure of the mine is complicated.
   The study of high-alkalinity sintered ore mixed with iron ore and bauxite showed that many Al 2 O 3 were found but no calcium orthosilicate, and aluminum yellow feldspar and iron were encountered in a fairly wide range of alkalinity (1.5 to 4.5). Acidate binder phase, 5CaO•3Al 2 O 3 appears when the alkalinity is higher than 4.5 .
(V) manganese ore sinter
   The important mineral of manganese ore is pyrolusite (MnO 2 ), after preheating ( greater than
   (6) Magnesium gangue self-fluxing sinter
   In many cases, concentrates and fines contain some MgO. Because the presence of magnesium oxide can improve the quality of sinter and reduce the viscosity of blast furnace slag, many regions of the sinter plant now incorporate dolomitized limestone in the sinter.
   In the case of normal carbon sintering, the magnetite and the floc body form a solid solution with MgO in the magnesium-containing sintered ore . FeO and MgO can form a continuous solid solution ( magnesium floater ). Magnesia magnetite exists in natural minerals and is also encountered in process rocks. Using limestone dolomitization sintered self-fluxing sintered ore, by means of electron probe studies show that when the basicity of from 0.5 to 2.3 time, MgO content increased from 0.63 1.31% magnetite, iron and calcium The medium content increased from 0.51 to 3.96%. When the sinter contains high enough MgO , in addition to calcium ferrite, magnesia (MgO•Fe 2 O 3 ) is also found in the microstructure .
The silicate binder phase composition is quite complex. Forsterite (Mg 2 SiO 4 or 2MgO•SiO 2 ), fayalite (Fe 2 SiO 4 or 2FeOSiO 2 ) and calcium orthosilicate (Ca 2 SiO 4 or 2CaO•SiO 2 ) form a solid solution in the sintered ore. When MgO is higher than CaO content in the sinter , the olivine phase is close to natural olivine (MgFeSiO 4 ), or calcium olivine (MgCaSiO 4 ). Magnesia sulphurite (Ca 3 Mg(SiO 4 ) 2 Or 3CaO•MgO•2SiO 2 ) and magnesium-containing pyroxene are frequently found. If there is a considerable amount of Al 2 O 3 in addition to MgO , the silicate binder phase in the sinter contains spinel (MgO•Al 2 O 3 ).
The addition of magnesium oxide to the sinter can stabilize the polycrystalline transformation of calcium orthosilicate at low temperatures, and thus is beneficial to the strength of the quartz gangue self-fluxing sinter.
   Magnesium oxide-containing sinter often contains a refractory phase which is formed in a solid phase reaction and thereafter. Therefore, it is necessary to increase the amount of carbon to be completely melted by the magnesium oxide containing sinter. When the liquid phase is cooled, the residue of these refractory phases can serve as a crystallization center, which can reduce the vitreous in the binder phase under the same conditions as ordinary lime-rich self-fluxing sinter.