The so-called super iron concentrate (HCM) refers to iron concentrates with high iron content and low gangue content. Generally referred to as iron concentrate with a SiO 2 content of less than 2% and a TFe content of approximately 70%. At present, such high-grade concentrates are not listed as the standard of commodity ore, so they are often called super concentrates or ultra-pure concentrates.
Super iron ore used for producing sponge iron or direct reduction of metal pellets, instead of scrap for electric steelmaking. With the development of the beneficiation process, the product quality of the super concentrate is also constantly improving. Now, in addition to the direct reduction of an electric furnace steelmaking, the sponge iron metallized pellets have been directly rolled; the production of metal iron for powder metallurgy Powder, used to suppress complex mechanical parts, such as special-shaped gears; instead of iron-red to produce magnetic materials, for radio communication, telephone, speaker, radar, television, magnetic separator, etc., can also be used for sewage treatment.
I. Direct reduction - Direct reduction of electric steelmaking is developed from the production of sponge iron instead of scrap. The iron ore used for direct reduction is a super iron concentrate or a rich ore. It can be used as a heat source and a reducing agent for natural gas or ordinary coal or petroleum . This technology has developed rapidly in countries and regions with less metallurgical coke and more coal and petroleum resources, such as Venezuela, Mexico, and Iran. The first direct reduction-electric furnace steel plant in the United States that used imported high-grade concentrates was put into operation in 1969.
From an economic point of view, under the same production, the direct reduction of the construction investment is basically the same as that of the blast furnace. But the production cost of sponge iron is much lower than that of blast furnace molten iron. According to the British report in 1973, the production cost of sponge iron is 28.6 US dollars / t, while the cost of blast furnace hot metal (93% Fe) is 127 US dollars / t. From the perspective of energy consumption, sponge iron is 16.16 MJ / t, while blast furnace molten iron It is 14.49 MJ/t. Since the coke price is three times more expensive than ordinary coal, the cost of blast furnace hot metal is higher than that of sponge iron.
Direct reduction - electric furnace steelmaking requirements for concentrate quality are generally SiO 2 content below 2%, the production of sponge iron metallized pellets SiO 2 content below 3%. High SiO 2 content will not only reduce the production capacity of electric furnace And the power consumption is high.
Second, the sponge iron pellets directly rolled steel with a purity of more than 99% of the super iron concentrate for direct reduction to obtain sponge iron, and then can roll steel, opening up a new way for steel production.
It is reported that Professor Singer of Swansea University in the United Kingdom will use super-fine concentrate powder with impurity content less than 1%, ie iron oxide content greater than 99%, to make ball with organic binder and produce gas reduction in rotary kiln or shaft furnace. A metallized sponge iron pellet is produced, and then the steel is hot rolled with the pellet. The process flow is shown in the figure below.
The mechanical properties of the rolled steel are close to that of low carbon steel and can be used for construction and construction of low stress structural parts.
This new process does not require blast furnaces and converters; it does not operate ingots, has fewer production steps, and has a lower reduction temperature, which can save a lot of energy. Corrosion tests of this steel show that the corrosion rate is faster at the beginning (in a few minutes or hours), but it is gradually slower, and finally it is similar to conventional products. The welding test shows that the purity of the concentrate is in the range of 99.2 to 99.4%, and the welding performance is not problematic. The UK's Overseas Development Department is very interested in this new process and is currently conducting research on pellet rolling in India and Brazil. Zinc-plated lower corrugated plate rolled in India with this material, product purity is less than 99% elongation, is limited to civilian hardware.
Although this new process is in the research stage, it is estimated that the unit investment is only 25-30% of the blast furnace and converter joint ventures.
In China, the Northeast Institute of Technology conducted a laboratory study. The super iron concentrate is reduced to a sponge iron pellet, and two sponge iron pellets are placed in a container and pressed by a press. From the phase diagram, the rolled pellets have obvious metal structure, which is basically ferrite. Similar to ordinary low carbon steel, the gap between the pellets is not seen after rolling, which proves the high wet ball cohesiveness. Well, it can be integrated to meet the basic requirements of rolling steel; its grain has a certain degree of plate structure, which shows good plasticity and uniform impurity distribution. The composition of the reducing agent can also be rolled out of a steel material equivalent to high carbon steel or rolled thin iron or the like. A unit uses a reduced metal iron powder to test a strip of 250-300 mm wide, which has a smooth surface and good toughness. [next]
Third, the production of iron powder with super iron concentrate
Iron powder is an indispensable metal raw material in the national economic construction and is widely used in machinery, electronics and chemical industries. With the development of the national economy, its use and use will become larger and larger.
In the past, the production of iron powder at home and abroad was mainly based on rolling steel scales (ie, iron oxide scale). In recent years, we have gradually researched and developed super concentrates as raw materials. According to statistics, the current iron powder production capacity in several major regions and countries in the world is about 545,000 t/a, and the iron powder production in China is estimated to be 14,000 t/a. The iron powder produced by using high-purity iron concentrate powder has good performance and stable quality. High output, low cost and low energy consumption, so high-purity iron concentrate gradually replaced steel scales. In this regard, the world's advanced industrial countries have developed rapidly, not only in the application of breakthroughs, but also make full use of the country's mineral resources, production is also increasing year by year. According to reports, the production of iron powder from super concentrates is: 160,000 t/a in Sweden, 80,000 t/a in the United States, and 40,000 t/a in Japan. China produces superfine ore as raw material to produce iron powder. On a small scale. For example, in the Kazuo Iron Mine in Chaoyang, the anti-flotation method is used to produce ultra-pure iron concentrates of 3000-5000 tons per year for permanent magnet materials produced by the Beijing Research Institute of Mining and Metallurgy.
The reduced iron powder NC100.24 produced by Hogannas of Sweden with super concentrate powder has a good comprehensive performance and is well-known in the international market. The company uses super concentrates for solid carbonization reduction and atomization to produce iron powder. The United States, Japan, the Soviet Union, and Germany all have successful experiences in the production of iron powder. It has successively established a powder metallurgy plant that directly reduces iron trioxide into iron powder.
The development and production of iron powder in China began in the 1960s, and many manufacturers such as Shanghai, Jinjiang, Chengdu, Tianjin, Wuhan and Anshan, Qingdao Powder Metallurgy Plant have been established. These manufacturers produce iron powder by using a secondary reduction method and using iron scales as raw materials. In May 1983, Benxi Nonferrous Metals Research Institute began to work on the production of iron powder from super iron concentrate. After more than two years of hard work, the iron powder with TFe greater than 99% was produced, and all the indicators met the national standards. , chemical and physical properties are stable, customer satisfaction, in December 1985 through the identification of the Liaoning Provincial Metallurgical Agency. The total cost of iron powder produced with super iron concentrate is estimated to be 1,170 yuan / t, the market price is about 1,700 yuan / t (identification time price).
The iron powder produced by super concentrate is used in the manufacture of powder metallurgy mechanical parts (such as shaped gears, plastic wires, sheets, strips, etc.), which can improve the utilization rate of materials and reduce the energy consumption during the processing of products; On the welding electrode, the welding efficiency of the welding rod can be greatly improved. In addition, it is widely used in flame cutting, electronics industry, chemical catalysts, electrostatic copiers and other fields.
4. Super iron concentrate is used to produce ferrite magnetic materials.
Ferrites are widely used in the electronics industry and occupy an important position. It is the basic material for communication in telephone, radio, television, radar, etc., especially for the manufacture of electronic computer core memory. It also occupies a considerable proportion in other industrial and household appliances.
The technical requirements of the electronics industry for ferrite vary with the type of ferrite. Especially for hard ferrite, the Fe 2 O 3 content must be greater than 98%, and the SiO 2 content should not exceed 0.6 to 0.8%. Of course, the higher the purity, the better. Such as: a hard ferrite factory in Italy, normally using a mixture of natural iron oxide (containing Fe 2 O 2 98.6%, SiO 2 0.6 ~ 0.8%) and synthetic oxide as a magnetic material, the effect is very good . According to the data, when the SiO 2 content is less than 0.6%, the produced ferrite exhibits uniform crystallization. Soft ferrites with excellent electromagnetic properties can only be made with relatively low (0.2%) materials containing SiO 2 . The soft ferrite that produces the electronic core memory can only be made from materials of a more stringent nature. Under ideal conditions, iron oxides of SiO 2 , Na 2 O, K 2 O and CaO should be absent. However, industrial products are allowed to contain certain impurities such as: SiO 2 0.03%, Na 2 O and/or K 2 O 0.05%, CaO 0.03%, traces of other impurities, total impurity content of 0.8%.
With this material, a barium ferrite magnetic strip having a magnetic field strength of 96 kA/m can be produced to produce a 167-C type cylindrical magnetic separator. According to the juice calculation, the use of barium ferrite with a magnetic energy product of 3.5 to 3.7 can solve the problem of manufacturing a magnetic separator having a magnetic field strength of 111 to 119 kA/m.
Our super iron ore powder has a trial strontium ferrite and barium ferrite. The magnetic material factory of Anshan City uses super concentrate as raw material, and the magnetic energy product produced by the magnetic material is generally more than 3, and the high energy can reach 3.8. Its performance is equivalent to the index obtained by using iron red as raw material, but the price can be cheap 50. ~60%.
5. Application of super iron concentrate in other aspects
Sponge iron with high purity can be used as raw material for smelting special steel. For example, the Benxi Iron and Steel Metallurgical Research Institute has used the super iron concentrate supplied by the Yingkou Pandishan Iron Mine to produce ultra-low carbon stainless steel. It is highly resistant to corrosion and can be used in chemical equipment. The domestic price is about 40 lower than the imported price. %.
The Harbin Institute of Civil Engineering and Architecture used super iron concentrate to treat sewage, and the test results were good. Super iron concentrate can also be used to make magnetic fluids, magnetic media, catalysts, etc.
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