What are the specific uses of silicon carbide and recarburizer in cast iron smelting? In recent years, as the country's requirements for the atmospheric environment have increased, it has become a consensus to strictly limit the pollution emissions of industrial enterprises. The melting of cast iron has changed from cupola to induction furnace melting. With the widespread promotion of electric furnace smelting, there are two kinds of non-metallic materials - silicon carbide and recarburizer, which are also increasing in the application of cast iron smelting.
The superheating temperature of the electric furnace smelting is obviously lower than that of the cupola, and the metallurgical condition is also worse than that of the cupola, especially the white mouth tendency and the shrinking tendency are higher than that of the cupola smelting. In order to improve the metallurgical quality of electric furnace smelting, reduce the heritability of pig iron and improve the mechanical properties of castings, the application of non-metallic materials such as silicon carbide and recarburizer has become an inevitable trend, especially when electric furnace smelting produces high quality cast iron parts.
At present, the silicon carbide products in the domestic market are black and green, their purity is different, and the price is different. Different companies can choose different silicon carbide products according to their own conditions and conditions. The microstructure and properties of cast iron depend to a large extent on the microstructure and quality of the raw materials. Low grade silicon carbide (about 85% SiC) is an excellent deoxidizer, which speeds up steelmaking and facilitates the control of chemical composition. Improve the quality of steel.
Silicon carbide can be used as a deoxidizer for steel making and a modifier for cast iron structures. It can be used as a raw material for the manufacture of silicon tetrachloride, and is the main raw material for the silicone resin industry. Silicon carbide deoxidizer is a new type of strong composite deoxidizer, which replaces the traditional silicon powder carbon powder for deoxidation. Compared with the original process, the physical and chemical properties are more stable, the deoxidation effect is better, the deoxidation time is shortened, energy is saved, and the energy is improved. Steelmaking efficiency, improving the quality of steel, reducing the consumption of raw and auxiliary materials, reducing environmental pollution, improving working conditions, and improving the comprehensive economic benefits of electric furnaces are of great value.
Due to the genetic influence of graphite in pig iron, a large amount of scrap steel and recarburizer have to be used for electric furnace melting. The use of recarburizers is very important, especially for cylinders and cylinder head castings with high requirements for compactness. It is necessary to use high temperature graphitized recarburizer. If there is no carbonization agent that has been graphitized by high temperature, it has a large amount of impurities, a large amount of ash, and it takes a long time to diffuse into the molten iron.
If the smelting time is short, the composition of the upper and lower irons in the electric furnace is not uniform, and the casting is likely to cause shrinkage defects after casting. In addition, the high-temperature-treated recarburizer has a high nitrogen content, and the nitrogen-containing scrap is increased to increase the nitrogen content in the molten iron. When a certain content is reached, crack-like pore defects are formed in the casting.
The method of adding the recarburizer: in the early stage, it is added simultaneously with the charge, and the middle stage charge has been partially melted, and the molten iron can be added in the late stage of melting. However, do not add more than 0.2% later to avoid coarse graphite. The use of recarburizers must use graphite recarburizers of good quality and low nitrogen content.
If the iron contains low Ti, it is impossible to neutralize a large amount of nitrogen, and at this time, a large amount of pores are generated due to the N2 removal. A good recarburizer containing graphite carbon should be between 95% and 98%, and the S content should be below 0.5%. N content of 500~4000ppm is a poor quality recarburizer.
In short, the use of two non-metallic materials, such as silicon carbide and recarburizer, on cast iron has its advantages and disadvantages. It must be carefully selected and used reasonably to achieve the desired results.
What is calcined petroleum coke?
Calcined petroleum coke is derived from the calcination of petroleum coke, which is a by-product of the delayed coking unit's feedstock oil cracking at high temperatures to produce light oil. The yield of petroleum coke is about 25-30% of the feedstock oil. Petroleum coke is a black or dark gray hard solid petroleum product with metallic luster and porosity. It is a carbonaceous material composed of tiny graphite crystals in the form of granules, columns or needles. The petroleum coke component is a hydrocarbon containing 90-97% carbon, 1.5-8% hydrogen, and nitrogen, chlorine, sulfur and heavy metal compounds.
In order to adapt the petroleum coke (green coke) to the requirements, the green coke must be calcined. The calcination temperature is generally around 1300 ° C, in order to remove the petroleum coke volatiles as much as possible. This can reduce the hydrogen content of petroleum coke re-products, and according to the degree of calcination, the temperature is about 1300 ° C for calcined petroleum coke, and at about 2700 ° C is graphitized petroleum coke, so that the degree of graphitization of petroleum coke is increased, thereby improving graphite The high temperature strength and heat resistance of the electrode and the conductivity of the graphite electrode are improved.
What are the uses of calcined petroleum coke?
Calcined petroleum coke can be used in industries such as graphite, steel casting and chemical industry depending on the index. Graphitized petroleum coke is of higher quality and more expensive. According to the different sulfur content, it can be divided into high sulfur coke (sulfur content above 3%) and low sulfur coke (sulfur content below 3%). Low sulfur coke can be used as anode paste and prebaked anode for aluminum plant and for steel The graphite electrode used in the factory. Among them, high quality low sulfur coke (sulphur content less than 0.5%) can be used to produce graphite electrode and carbonizer. General quality low sulfur coke (sulphur content less than 1.5%) is commonly used in the production of prebaked anodes. Low-quality petroleum coke is mainly used for smelting industrial silicon and producing anode paste. High-sulfur coke is generally used as fuel for cement plants and power plants.
1. Used as prebaked anode material for aluminum
The prebaked anode is made of petroleum coke and pitch coke, and the coal bitumen is made of a binder, and then calcined to have a stable geometric shape, which is called a carbon anode block for aluminum electrolysis. The sulfur content of this calcined coke is mainly 3.0% or 2.0%, and some have requirements for vanadium content, and the particle size is mainly 0-30mm.
2. Petroleum coke recarburizer: calcined petroleum coke and graphitized petroleum coke
The sulfur content of the calcined petroleum coke is generally in the range of 0.5% to 1%, and the sulfur content of the graphitized petroleum coke is 0.05% to 0.3%. The calcined petroleum coke recarburizer is generally used for gray iron casting, and the graphitized petroleum coke recarburizer is used for ductile iron.
3. Graphite electrode
Graphite electrode refers to a kind of calcined petroleum coke and pitch coke as the main material, coal tar pitch as the binder, which is made by calcination of raw materials, crushing and milling, compounding, kneading, forming, roasting, impregnation, graphitization and mechanical processing. The high temperature resistant graphite conductive material, called artificial graphite electrode, is distinguished from the natural graphite electrode prepared by using natural graphite as a raw material.
Calcined petroleum coke can be used in the industries of graphite, smelting and chemical industry depending on its quality. Low-sulfur, high-quality cooked coke, such as needle coke, is mainly used to manufacture ultra-high-power graphite electrodes and some special carbon products. In the steel-making industry, needle coke is an important material for developing new technologies for electric steelmaking. Medium sulfur, ordinary cooked coke, used in large quantities for aluminum smelting. High sulfur and ordinary coke are used in chemical production, such as the manufacture of calcium carbide, silicon carbide, etc., as well as fuel for metal casting. Most of the petroleum coke produced in China belongs to low-sulfur calcined petroleum coke, which is mainly used for aluminum smelting and graphite production.
About the steel or iron casting materials, there are many kinds of calcined petroleum coke recarburizers. The factory should choose the recarburizer suitable for itself. In addition to the requirements for particle size, the specificaitons are also include the fixed carbon content, sulfur content and nitrogen content.
In the general furnace smelting process, the calcined petroleum coke particle below 0.2mm is very easy to be lost. If it is added later, the loss is more severe. Nowadays, more 1-5mm calcined petroleum coke is used and the effect is also good. However, it is still based on the needs of different manufacturers.
The length of residence time of the recarburizer in the molten iron, the temperature of the molten iron, that make the effect of stirring in the electric furnace are different. The diffusion rate of the recarburizer is related to the concentration of the recarburizer. Therefore, there are many factors that need to be grasped in the process of using a recarburizer, everyone should pay attention.
Correct useing method of calcined petroleum coke recarburizer to increase carbon content in induction furnace
1. Using 5T or more electric furnace, we recommend the dispersion method. According to the requirement of carbon content, according to the ratio of ingredients, the recarburizer and the metal charge are added together with the batch materials to the lower part of the electric furnace, and a layer of metal charge is used as a layer of carbon reinforcer. The carbon absorption rate can reach 90%-95%. The recarburizing agent should not be slag when it is melted, otherwise it will be easily wrapped in the waste residue and affect the absorption of carbon.
2. The use of 3T medium-frequency induction furnace, our carbon-reinforcing agent company recommended to join the method. When melting or remaining a small amount of molten iron in the furnace, add the added carbonizer to the surface of the molten iron at one time, and immediately add the metal charge, and press all the recarburizer into the molten iron to make the recarburizer fully contact with the molten iron, the absorption rate is above 90%.
3. The use of small medium-frequency electric furnace, raw materials with high-carbon materials such as pig iron, we recommend fine-tuning of carbon-reducing agents. After the molten steel/iron water is melted, the carbon content can be adjusted on the surface of the steel/iron water. The vortex stirring or manual stirring of the steel (iron) water in the electric furnace smelting dissolves and absorbs the product, and the carbon absorption rate is about 93%.
What is a recarburizer? A recarburizer is an carbon additive for steel & iron casting. In the production of steel, it not only reduces the use of pig iron, but also increases the amount of steel scrap. The recarburizer is an essential carbon raw material for the production of high-quality steel. At the same time, in gray cast iron and ductile iron, the recarburizer also plays a very good role in carbon addition.
What are the advantages of using a recarburizer for steel & iron casting? Everyone knows that when steel is manufactured, castings are prone to various problems. This is not only a waste of financial resources, but also loss of human resources, and finally a waste of resources.
The recarburizing agent is used in casting, which can greatly increase the amount of steel scrap, reduce the use of pig iron or even eliminate the use of pig iron, and greatly reduce the production cost.
The recarburizers are mainly come from coal and petroleum coke. Most of the recarburizers are petroleum coke, and are suitable for electric furnace melting, and a small part of the reheating agent with a particularly fast absorption rate is used for the cupola.
In the feeding mode of electric furnace smelting, the recarburizing agent should be placed together with the charging materials such as scrap steel. The addition of small doses can be added to the surface of the molten iron, but it is necessary to avoid feeding large quantities into the water to prevent excessive oxidation and carbonation. The effect is not obvious and the carbon content of the casting is insufficient.
The amount of recarburizer added depends on the ratio of other raw materials and the carbon content. Different types of castings can be selected according to the needs of different types of recarburizers. Petroleum coke recarburizer can reduce the amount of pig iron. The amount of impurities, the choice of recarburizers can reduce the cost of living from that. For this reason, most manufacturers use petroleum coke recarburizers to reduce production costs.
What is petroleum coke? Petroleum coke is a product obtained by separating crude oil from heavy oil by distillation and then thermally cracking the heavy oil. From the appearance, coke is a black block (or granule) of irregular shape and size. ), with metallic luster, coke particles have a porous structure, the main elemental composition is carbon, and contains less impurities than coal.
Petroleum coke can be used in the industries of graphite, smelting and chemical industry depending on its quality. Low-sulfur, high-quality cooked coke, such as needle coke, is mainly used to manufacture ultra-high-power graphite electrodes and some special carbon products. In the steel-making industry, needle coke is an important material for developing new technologies for electric steelmaking. Medium sulfur, ordinary cooked coke, used in large quantities for aluminum smelting. High sulfur and ordinary coke are used in chemical production, such as the manufacture of calcium carbide, silicon carbide, etc., as well as fuel for metal casting.
Most of the petroleum coke produced in China is low-sulfur coke, which is mainly used for aluminum smelting and graphite production. It is mainly used for the production of carbon products, such as graphite electrodes and anode arcs, for steel making, non-ferrous metals, and aluminum smelting; for the production of carbonized silicon products, such as various grinding wheels, sand sheets, sandpaper, etc.; Production of synthetic fibers, acetylene and other products can also be used as fuel, but when used as fuel, it needs to be crushed by a graded impact mill for superfine pulverization. It can be burned after making coke powder through JZC-1250 equipment, using coke powder as fuel. Mainly some glass factories, coal water slurry plants, etc.
Another use of petroleum coke is to produce higher quality carbon materials after calcination. For example, 3.0% of high sulfur calcined coke after calcination can be used as prebaked anode for aluminum, and low sulfur calcined petroleum coke can be used as recarburizer. It is a low-demand use such as gray cast iron. After deep processing of petroleum coke, graphitized petroleum coke can be obtained. It is a high-quality carbon material and can be used as a recarburizer.
Recarburizers, as the name suggests, are substances that have a carbon-increasing effect. It is believed that friends who have worked in steel mills are no strangers. Recarburizers are additives used to supplement the carbon content of molten steel. In the deoxidation process in the early stage of steel smelting, a large amount of carbon will be removed, and the molten iron will be converted into molten steel. However, in the later stage of smelting, if the amount of carbon in the molten steel is small, it will also affect the steel, so it is necessary to add some recarburizer. To increase the carbon in the molten steel.
As one of the objects of iron and steel manufacturers' purchase, recarburizers have important applications in the process of steel making. First of all, we must start from what is a recarburizer. Carbon reinforcers are the collective name of carbon products, and their main components. It is a carbon element. At present, there are many carbonaceous recarburizers, and the high-quality carbonizing agent has a good graphitization effect. At a certain temperature, the graphite of carbon in the recarburizer can be clearly seen by using a microscope. Form and recarburizer production process are various and have the purpose of enhancing carbon in practical applications.
The main purpose of the recarburizer is to increase the carbon content lost during the steel making process. If the carbon content does not meet the expected requirements during the steel making process, a certain proportion of recarburizer should be added. The main purpose is to raise the molten steel. The carbon content of the material thus smelts the ideal steel.
In fact, if you want to supplement the carbon content in the molten steel, you need to do a strict quality test on the added recarburizer to prevent the introduction of excessive impurities in the recarburizer, thus affecting the quality of the steel. We all know that the recarburizer is added in the later stage of steel smelting, so the determination of the impurity content in the recarburizer cannot be ignored.
The recarburizer has a wide range of uses and can also be used in the foundry industry. In the casting, the recarburizer has the purpose of reducing the gradual cost, and the recarburizer as the casting material can greatly reduce the gradual cost, and the recarburizer has the lubricating use and can be effectively improved. The service life of the castings improves the gradual quality.
A recarburizer (calcined petroleum coke) is an auxiliary additive. So how can we use it correctly? Now the recarburizer manufacturer introduces you how to use the recarburizer correctly.
When using a recarburizer, place the recarburizer in the middle and lower part of the furnace as much as possible, and add other charge to reduce the overflow of the recarburizer and increase the contact surface between the recarburizer and the molten iron. Improve carbon efficiency.
If the furnace is used in a relatively large furnace, it should be added in multiple times, which can better improve the dissolution rate and increase the absorption rate of the graphitized recarburizer. At the same time, the recarburizer is placed on the bottom of the furnace, and it can also buffer the impact on the bottom of the furnace when the iron is added. This also protects the role of the lining.
The recarburizing agent is used in casting, which can greatly increase the amount of scrap steel, reduce the amount of pig iron or use no pig iron. Therefore, we should use this correctly when using it to better reduce costs.
Graphitized petroleum coke recarburizers are widely used in steelmaking and casting. Due to the impact of the market, many manufacturers are looking for ways to increase production efficiency while saving resources. Therefore, the scrap + recarburizer process is launched in many steel casting manufacturers.
No matter what method has its advantages and disadvantages, but the disadvantage of this method is that the nitrogen content of the waste is much higher than that of cast iron, so the induction furnace melts the cast iron, we must pay attention to the nitrogen level. Want, this is the only way to solve this way should pay attention to the nitrogen content of the recarburizer.
The choice of graphitized petroleum coke recarburizers is the basis that many manufacturers are now seeking. Because the graphitized sulfur content of the material is double zero, the recarburizer is characterized by a soft, elastic texture that can be traced on paper.
Therefore, everyone should choose recarburizers. On the one hand, they should be more assured of their factory production process, on the other hand, the method of identifying high-quality recarburizers, and the local testing institutes for actual testing. This combination is more conducive to improving the quality of castings to increase production efficiency.
It is customary to say that steel is a general term for steel and iron, but the actual steel and iron are different. The two are mainly divided by the amount of carbon. For the increase of carbon content, it is necessary to use a recarburizer, and a petroleum coke recarburizer[calcined petroleum coke & graphitized petroleum coke] is commonly used.
The carbon content classification standard for steel.
China has used the carbon content of steel as the grading standard for many years. In the national standard for casting carbon steel, regarding the steel grade, chemical composition and mechanical properties, the “ZG” in the grade indicates cast steel, and then The figure indicates the nominal value of the weight fraction of carbon in the steel, expressed in parts per million. Cast carbon steel is classified into three grades according to the phosphorus and sulfur content of its impurity elements, and the grades of grades of phosphorus and sulfur are less than 0.04% (I grade) steel; and the quality of grade II grade steel is less than 0.05%. Less than 0.06% is ordinary (III grade) steel.
1. Low carbon steel: usually C% <0.25%, called low carbon steel, low strength, good plasticity and weldability.
2, medium carbon steel: C% is 0.25 ~ 0.60%, called medium carbon steel, has higher strength, but poor plasticity and weldability.
3, high carbon steel: C%> 0.60%, called high carbon steel. Poor plasticity and weldability, but high strength and hardness after heat treatment.
More than 2% carbon is cast iron, and cast iron is mainly gray cast iron and ductile iron. Recarburizers[CPC & GPC] are often used in the smelting of cast iron.
1. Gray cast iron C%: 2.7%-3.9%. Ordinary gray cast iron is mainly cast iron in which carbon is precipitated in the form of flake graphite. Gray cast iron is widely used. In the total output of various types of cast iron, gray cast iron accounts for more than 80%.
2. Ductile iron C%: 3.5% -3.9%, ductile iron is a high-strength cast iron material, its comprehensive performance is close to steel, it is based on its excellent performance, has been successfully used for casting some force complex, strength Parts with high toughness and wear resistance. Ductile iron has rapidly developed into a cast iron material that is second only to gray cast iron and is widely used. The so-called "iron-based steel" mainly refers to ductile iron.
Graphite products have been widely used in industrial sectors such as metallurgy, machinery, electrical, chemical, textile, and defense because of their many excellent properties.
Two important changes in the graphite refractory industry are the widespread use of magnesia carbon bricks in steelmaking linings and the application of aluminum carbon bricks in continuous casting. One of the main uses of graphite is in the production of refractory materials, including refractory bricks. , crucible, continuous casting powder, mold core, mold, detergent and high temperature resistant materials.
Graphite products are currently used in large quantities in the world for magnesia carbon bricks, and have become a traditional use of graphite. Conventional graphite clays are made of flake graphite with a carbon content greater than that of graphite, which is currently produced in foreign countries. Important improvements in technology.
The type of graphite used, the size and quality of the graphite have greater flexibility. Secondly, the traditional clay graphite crucible is replaced by silicon carbide graphite crucible. The products are increasingly used in mining systems, diesel systems, railway systems and high-tech. industry.
Graphite particles are mainly derived from the scraps generated during the machining of graphite electrodes and the waste products generated by the graphitization process. They are one kind of graphite products. Because graphite scraps have electrical conductivity, thermal conductivity, high temperature resistance, low ash content and high carbon content. It has a good chemical stability and is widely used as a recarburizer for steelmaking furnaces.
The combination of domestic graphite column and self-produced wear-resistant plate technology has made outstanding contributions to the development of China's automobile industry, greatly improving the production efficiency of automobiles, and lowering the cost of automobiles. It is used in guide bushes, guide columns and self-control. Lubricating the graphite column on the bearing and wear plate, the graphite product can also be made by carbonizing the carbon refractory material in a resistance furnace at 2500 ° C ~ 2800 ° C to make it graphitized.
Graphite products can be used as reaction tanks and autoclave linings in the chemical industry. They are also widely used in the manufacture of corrosion-resistant heat exchangers and masonry high-temperature furnaces. Graphite has a high scattering cross section and a very low thermal neutron absorption cross section. The high scattering cross section is used to slow down the neutrons, the low absorption cross section prevents the neutrons from being absorbed, allowing the nuclear reactor to achieve critical or normal operation with a small amount of fuel, which is used in graphite materials for the nuclear industry.