Name | Molybdenum iron |
Synonyms | Molybdenumiron Molybdenum iron |
CAS | 12382-30-8 |
Molecular Formula | FeMo |
Molar Mass | 151.785 |
Use | Used to eliminate the temper brittleness of nickel and chromium steel, improve the strength, wear resistance and impact strength of steel |
Ferromolybdenum alloy | Ferromolybdenum refers to an alloy formed by melting molybdenum and iron with a molybdenum content in the range of 55.0% to 75.0%. Molybdenum iron standard requirements of molybdenum content of more than 55%, the actual production of most molybdenum content of about 60%. It is mainly used for steel-making molybdenum element additive. Because molybdenum can reduce the eutectic decomposition temperature of steel, expand the range of steel quenching temperature, thus affecting the depth of steel hardening. Molybdenum is often used in combination with other elements such as chromium, nickel, barium, etc. The steel has a uniform fine grain structure, and the strength, elastic limit, wear resistance and impact strength of the steel are improved. Molybdenum is widely used in refining structural steel, spring steel, bearing steel, tool steel, stainless acid-resistant steel, heat-resistant steel and magnetic steel and a series of steel. In addition, the application of molybdenum in alloy cast iron, gray iron grains smaller, and can improve the performance of gray iron at high temperature, improve its wear resistance. |
History of discovery | molybdenum was discovered in 1778 by the Swedish chemist, C.W.Scheele. In 1894, molybdenum was first used in the production of armored steel plates. Ferromolybdenum was first produced in France in 1900, as reported by A.Coutagne. Molybdenum-containing steel was found to have special properties in 1910. The reduction of molybdenite with carbon and the production of ferromolybdenum with lime as a flux were carried out in an electric furnace before 1930. This method has to be refined many times for desulfurization and decarburization, resulting in a decrease in the recovery rate of molybdenum. Later instead of molybdenum sulfide first oxidized to molybdenum oxide, and then the metal thermal reduction method of molybdenum oxide reduced to molybdenum iron. Molybdenum ore was found in the late Qing Dynasty in China. On the eve of the First World War began mining, has been built production base of yangjiaizi, Jinji city, xiaosigou, Baoshan, Luanchuan and so on. Jilin Ferroalloy Factory started production of ferromolybdenum in 1956. |
Properties and uses | molybdenum has an atomic weight of 95.94. The outer layer has an electronic structure of 4 d55s1, a melting point of 2615 ° C., a boiling point of 4610 ° C., and a density (20 ° C.) of 10.2g/cm3. The binary phase diagram of molybdenum and iron is shown in Figure 1. Molybdenum and iron form two solid solutions of α and γ and two intermetallic compounds ε(Fe7Mo6) and σ(FeMo) phases. Industrial Ferromolybdenum contains about 60% Mo, melting temperature of 1800~1900 deg C; Density of about 9.0g/cm3. Ferromolybdenum is an iron alloy, which is produced by smelting molybdenite or refined molybdenum ore after roasting in an electric furnace. It is mainly used as the additive of alloying elements for smelting magnetic steel, structural steel and high speed steel. The Ferromolybdenum produced in our country contains about 55% molybdenum. If only a small amount of molybdenum is contained in the steel, calcium molybdate can be used as an element additive, and the cost is much lower than that of ferromolybdenum. The role of molybdenum in steel can be summarized as improving hardenability, improving thermal strength, preventing temper brittleness, improving remanence and coercivity and corrosion resistance in some media, and can prevent pitting tendency and so on. Due to the various beneficial effects of molybdenum in steel, in a series of steels such as structural steel, spring steel, bearing steel, tool steel, stainless acid-resistant steel, heat-resistant steel (also called hot steel), magnetic steel, has been widely used. Molybdenum in cast iron to improve the strength and toughness is very effective, the addition of 0.25% ~ 1.25%, Pearlite matrix structure can also be formed for castings with medium and large cross sections. Commonly used in rolls and other wear-resistant castings. Fig.1 binary phase diagram of molybdenum and iron |
molybdenum concentrate | molybdenum mineral of industrial value is molybdenite (MoS2), in nature, it forms a single molybdenum sulfide deposit and a copper-molybdenum deposit associated with copper ore. Molybdenum ore contains Mo 0.2% ~ 0.5%, and molybdenum concentrate can only be obtained after beneficiation and enrichment. Smelting molybdenum concentrate for Ferromolybdenum, containing MOS2>75%,Pb |
oxidation roasting of molybdenum concentrate | The oxidation roasting of molybdenum concentrate is carried out in a multi-bore furnace. Usually 8 to 12 layers. The molybdenum concentrate is added to the edge of the uppermost layer of the furnace from the top feed hole, and the mechanical rake driven by the central axis pushes the concentrate to the center of the furnace and falls into the next layer. Then it is pushed from the center to the edge and falls into the lower layer. This is repeated until it is discharged from the discharge hole of the lowermost layer. During the movement of molybdenum concentrate in the furnace, from top to bottom, the initial moisture is evaporated, the flotation agent is burned, and the charge is gradually heated. It is ignited when the ignition point of molybdenite is reached. The sulfur in the concentrate is oxidized to sulfur dioxide by oxygen in the air entering from the door opening, and a large amount of heat is released at the same time. The temperature of each layer in the baking furnace should be strictly controlled within the specified range. The maximum temperature in the furnace should be controlled below 680 ° C to avoid the loss of molybdenum caused by the sublimation of moo3. Gas (or fuel) nozzles are provided in the lower 2-3 layers of the furnace to maintain the calcination temperature and continue the desulfurization reaction. The temperature range of molybdenum concentrate controlled by 8-layer roasting furnace and the change of sulfur content of molybdenum concentrate are as follows: sulfur content in molybdenum calcine obtained by roasting |
smelting raw material | Ferrosilicon is used to reduce molybdenum calcine to produce ferromolybdenum. The reaction heat can not meet the requirements of the process, and it is necessary to add some aluminum and nitrate to supplement the reaction heat. The environment is polluted by nitrogen oxide produced by the reaction of niter, and the ratio of aluminum to iron ore can be adjusted to supplement heat. The requirements for raw materials are as follows: (1) the proportion of S10mm in molybdenum calcine is required to be less than 10%, (2) the silicon powder contains 75% ~ 77% of Si; particle size (3) aluminum particles containing Al>90%,Cu (4) iron ore containing Fe>65%,S (5) steel scrap is plain carbon steel scrap, crimp length (6) fluorite containing CaF2>90%. Particle size (7) niter containing NaNO3>90%. all raw materials shall be thoroughly dried, and shall not contain moisture, so as to avoid sputtering and accidents in the smelting process. The raw materials are accurately weighed according to the calculated ratio, and mixed into the mixer, and then loaded into the melting furnace, and melted by the upper ignition method. |
Ferromolybdenum melting furnace | the structure of ferromolybdenum melting furnace is shown in figure 4. The upper furnace tube is built with refractory bricks, and the bottom is a sand nest made of river sand. After the charge is mixed evenly, it is loaded into the melting furnace, and the center is slightly raised. Place the ignition mixture (a mixture of niter and aluminum particles) in the upper part of the charge, and stick a small hole in the lower part of the ignition mixture into the charge. A small amount of magnesium dust is added to the ignition mixture, and the reaction is ignited with a red-burning iron rod (or open flame or electric arc), and the reaction is carried out automatically. The melting furnace tube with an inner diameter of 1700 ~ 1800mm and a height of about 2000mm can be equipped with 4000 ~ 5000kg of molybdenum calcine and its corresponding burden per furnace. The reaction time was about 4-5min. After completion of the reaction, the reaction mixture was sedated for 30-50min, and the slag hole was opened to discharge the slag. After the slag was discharged, the furnace tube was lifted. After cooling for another 6-8H, the Ferromolybdenum ingot was removed, quenched with water for 40-60min, broken, finished and packed. The finishing of the resulting scrap metal is returned to the smelting. Mo content> 55%,C Figure 4: Schematic diagram of ferromolybdenum melting furnace 1-furnace shell; 2-clay brick lining; 3-slag mouth; 4-sand base; 5-surface of sand socket made of new sand; 6-molten pool containing Ferromolybdenum; 7-smoke shield |
Ferromolybdenum production process | Ferromolybdenum is produced by smelting molybdenite or roasted refined molybdenum ore in an electric furnace. The main raw material for smelting Ferromolybdenum is molybdenite (MoS2). Before smelting, molybdenum concentrate is usually oxidized and roasted in a multi-bore furnace to obtain roasted molybdenum ore with sulfur content less than 0.07%. Outside the furnace method is generally used in the smelting of ferromolybdenum. The furnace was a cylinder placed on a sand base, lined with clay brick, using 75% silicon-containing ferrosilicon and a small amount of aluminum particles as a reducing agent. After the charge is added to the furnace tube once, the upper ignition method is used for smelting. On the surface of the material with an initiator (niter, aluminum or magnesium chip), after ignition that intense reaction, and then sedation, slag, removal of the furnace tube. The Ferromolybdenum ingot is cooled in the sand socket first, then sent to the cooling room for flushing cooling, and finally broken and finished. The metal recovery rate was 92 ~ 99%. Molybdenum oxide briquettes have been widely used in the steelmaking industry in recent years instead of ferromolybdenum. Ferromolybdenum is usually melted by metal thermal reduction method. The process flow is shown in figure 2. Firstly, molybdenum calcine (MoO3) was obtained by oxidation roasting of molybdenum concentrate (MoS2>75%), and then Ferromolybdenum was obtained by metal thermal reduction method. The main reactions were:(1)2MoS2+7O2 → 2MoO3+4SO2 ↑ (2) 2MoO3 + 3Si → 2Mo +3sio2. Ferromolybdenum production process flow diagram |
Application | is used to eliminate the temper brittleness of nickel and chromium steel, improve the strength of steel, abrasion resistance and impact resistance |