Al2O3 in inclusion of 310S casting process. The less they are, the lower the interfacial tension, and the more difficult they are to eliminate. It has been proved that the stronger the chemical bond of deoxidation products, the higher the melting point, the greater the cohesion, and the weaker their chemical interaction with liquid steel. Therefore, even if the refractory solid particles as long as there is enough interfacial tension, it can float from the steel to the slag layer at a very fast speed, that is to say, there are many strong deoxidizer deoxidizing products are easy to float and eliminate. The melting rate also depends on the chemical composition of the charge. The resistance of 0.20% carbon steel is 6 times that of copper, while that of 0.90% carbon steel is l4 times that of copper. The charge can be regarded as the secondary circuit of the current according to Joule's law: b. High carbon, low phosphorus. If there is no licensing conditions for slag picking, the operation at this time in addition to the use of powder spraying dephosphorization, can also use decarbonization boiling, and dephosphorization in decarbonization. Steel castings are parts made of cast steel, similar in properties to cast iron but stronger than cast iron. In casting, steel castings are prone to defects such as porosity defects and inaccurate Angle positioning, which may lead to shell fracture in long-term use. In order to fully deoxygenate molten steel, calcium carbide slag should be kept for 20 ~ 30min. If calcium carbide slag is used to produce steel, the free carbon in the slag will also make the finished carbon of steel. Calcium carbide slag is divided into weak calcium carbide slag (CaC21 % ~ 1.5%) and strong calcium carbide slag (CaC22 % ~ 4%) due to different calcium carbide content.
One of the advantages of 310S corrosion resistant casting steel castings is the flexibility of design. The design choice of the shape and size of the castings, especially the parts with complex shapes and hollow sections, can be made by the unique process of core formation. Its shape and shape change is very easy, from the drawing to the finished product transformation speed is very fast, is conducive to rapid quotation response and shorten the delivery time. The stress concentration factor of shape and perfect design as well as the overall structure reflect the flexibility and technological advantages of steel casting design: However, the temperature rise of molten steel can not be endlessly too high, because the high smelting temperature not only wastes a lot of raw materials and electric energy, but also erods the furnace lining seriously. For the electric furnace with large capacity, due to high enthalpy and difficult cooling, it is easy to appear high temperature steel or affect the reduction operation and steel pouring. C. Low carbon, high phosphorus.
In order to avoid the rapid cooling of the molten pool, the ore should be added in batches, each batch of about 1.0% to L.5% by weight of molten steel, and when the reaction of the first batch of ore begins to weaken, the next batch of ore should be added at an interval of 5 to 7 minutes. The uniform and intense boiling of molten pool is mainly controlled by the rate of adding ore and the interval time maintained. When the temperature of molten pool is high, the rate of adding ore cannot be too fast. If fierce flame appears in the furnace door and electrode hole, ore should be stopped to avoid spatter or steel running accidents. Steel casting metallurgical manufacturing has strong adaptability and variability, can choose different chemical composition and structure control, adapt to the requirements of various projects; It can choose mechanical properties and service properties in a wide range through different heat treatment processes, and has good welding properties and processing properties. Molybdenum in many tungsten steels can replace part of tungsten in composition, so strict attention should be paid to the ingredients. Sometimes the liquid steel is deoxidized well, but due to the high content of hydrogen in the steel, it will also cause a rise, identified as follows: remove the liquid steel, a small amount of aluminum forced deoxidization, and then gently inject the liquid steel into the deoxidization cup, if not rising, indicating poor deoxidation; If it still rises, the hydrogen content in steel is higher.
It must be pointed out that blowing or CO gas into the molten pool can produce a good boiling, but it does not solve the oxidation of impurities in the steel, and the oxidation of many impurities is dependent on oxygen. Therefore, if oxygen is not supplied to the molten pool during the oxidation period, argon or CO gas can not be blown alone, and the liquid steel will not be relatively pure. The isotropy of cast steel material and the strong overall structure of cast steel result in engineering reliability. In addition, it has a competitive edge in price and economy due to its lightweight design and short delivery time. The fourth stage: melting low temperature zone charge stage. The three-phase arc is similar to the point heat source, and the thermal radiation of each phase is not uniform, so the temperature distribution in the furnace is not uniform. In general, the charge melting is faster at the bottom of the electrode and the hot spot area near the 2# electrode, while the charge melting is slower at the low temperature area near the door, steel outlet and the wall of the l# furnace. The fourth stage is mainly to melt the charge in these parts.
Practice has proved that reasonable oxygen blowing and early production of molten slag can inclusion fully floating. After oxygen blowing, due to the action of oxygen flow, the molten pool is partially boiling, which is conducive to the collision and floating of inclusions. The slag is not only beneficial to dephosphorization, but also can adsorb nonmetallic inclusions well. Four, melting period dephosphorization operation melting period of the correct operation, can remove 50% to 70% of the phosphorus in the steel, the remaining residual phosphorus in the oxidation period by means of the interface reaction between slag and steel, automatic slag flow, make new slag or use powder spraying dephosphorization and other methods to continue to remove. The weight of steel castings varies over a wide range. Small weight can be only tens of grams of investment precision castings, and the weight of large steel castings can be several tons, tens of tons or even hundreds of tons.
310S casting process corrosion resistant castings defect uneven structure. After the liquid metal is injected into the mold, the first layer of liquid metal with the mold wall is rapidly solidified into fine grains due to the rapid temperature drop. With the distance from the die wall, the influence of the die wall gradually weakens, and the crystals grow into columnar crystals parallel to each other along the direction perpendicular to the die wall. In the center of the casting, the heat dissipation has no significant direction, and can grow in all directions until each other, so the equiaxed crystal area is formed. It can be seen that the structure in the casting is not uniform, generally speaking, the grain is more. At this point, Stokes formula can be simplified into the following formula: V =Kr2 i. Melting of charge after the start of power supply, is the beginning of the melting period, the melting of charge is generally second, the distribution of all kinds of charge should be reasonable.
A large number of production practice has been summarized: high carbon steel melting, good fluidity, steel temperature should be lower, low carbon steel temperature should be higher; Viscosity, such as high chromium steel, steel temperature should be higher, and fluidity or corrosion of refractory materials, such as high silicon steel, high manganese steel or high manganese high silicon steel, steel temperature should be lower; The temperature control of high alloy steel with more alloying elements and impurities should be higher, while the temperature control of general alloy steel should be lower. The tissue is not dense. The crystallization of liquid metal is carried out by the growth of branches, and the liquid gold between branches solidifies. However, it is difficult to fill all the branches with metal, resulting in the general incompactness of castings. In addition, the liquid metal injected into the mold may form loose or even shrinkage cavity if its volume shrinks during cooling and solidification without sufficient replenishment. The graphite in cast iron often appears in larger size flake, ball or other shape, which can also be regarded as an uncompact structure. The advantage of this kind of steel making is that the molten steel can be protected by slag, which can not only reduce the temperature of molten steel, but also control the secondary oxidation and suction of molten steel. In addition, the non-metallic inclusions suspended in steel can be fully washed by slag, which is conducive to floating and removal, and can be further deoxidized and desulfurized by mouth spout. Therefore, this kind of steel is more common.
The surface of corrosion-resistant castings is rough. The surface is generally rough and cannot be compared with the machined surface, and the shape is more complex. In general, most metal oxides boil at the metal's boiling point, such as M0's boiling point of 4800℃, and M003. The boiling point of is only ll00℃, so the volatilization of many metal oxides often precedes the direct volatilization of the element. There are many metal oxides in the smoke and dust escaping from the furnace door or electrode hole during the melting period, most of which are Fe203. This is because iron occupies a proportion in the charge and the vapor pressure of liquid iron is also large, so the smoke and dust escaping during the melting period are mostly brownish red.
