Furnace lining material and molding material used for smelting high manganese steel in intermediate frequency furnace
We all know that high manganese steel easy to work hardening, which is difficult to process, the vast majority of castings, very small amount of forging processing methods. High manganese steel casting performance is better. The low melting point of steel (about 1400 ℃), steel liquid, solidus temperature interval is small, (about 50 ℃), tundish nozzle low thermal conductivity of steel, so the molten steel flow is good, easy to pour molding. High manganese steel linear expansion coefficient of 1.5 times for the pure iron, carbon steel 2 times, so the casting volume shrinkage and linear high alumina bricks shrinkage are large, prone to stress and crack casting temperature of 1400 + (80- 100) 80-100 to see the situation and the complexity of the casting plant, up to 150. High-manganese steel casting process In the high-energy impact of the working conditions, high manganese gunning mix steel and ultra-high manganese steel casting applications are broad. Many foundries do not have the necessary knowledge to produce such steel castings. Is a brief description of the specific operation for producers of reference. 1, the chemical composition of high manganese steel in accordance with national standards are divided into five grades, the main difference is the carbon content, the range is 0.75% -1.45%. The impact of large, low carbon ramming mass content. Manganese content between 11.0% -14.0%, generally should not be less than 13%. Ultra-high manganese steel is not the national standard, but the manganese content should be greater than 18%. Silicon content of high and low impact on the impact toughness, it should take the lower limit to not more than 0.5% is appropriate. Low phosphorus and magnesia carbon refractory low sulfur is the most basic requirements, due to the high manganese content of natural play desulfurization, it is the most important phosphate, try to make phosphorus less than 0.07%. Chromium is to improve the wear resistance, generally about 2.0%. 2, charge into the furnace material is determined by the chemical composition. The main charge is high quality carbon steel (or ingot), high carbon ferromanganese, medium carbon ferromanganese, high carbon ferrochrome and high manganese steel back to the charge. Here is a reminder of the people think that as long as the chemical composition is appropriate, you can use more with the charge back. This person is harmful. The reason why some plant products of poor quality, are out of this. Not only high-manganese steel, ultra-high manganese steel, all metal castings, must not be too much to use back to the charge, the charge should not be more than 25%. So, what about the excess charge As long as the waste to a minimum, no excess charge back. 3, melting Here focus on the charging sequence, whether in the IF furnace, or electric arc furnace smelting, always smelting carbon steel, and various types of ferromanganese and other precious alloy materials, to be divided into several times, each into the furnace a small, expensive The elements are added at the end to reduce burn. Block should be as small as possible to 50-80mm is appropriate. Melting, the furnace temperature reached 1580-1600 ℃, to deoxidation, dehydrogenation, denitrification, available aluminum wire, can also be used Si-Ca alloy or SiC and other materials. Deoxidizer must be pressed to the depths of the furnace. At this point the metal surface covered with cover agent, cut off the outside air. But also to calm for some time, so that oxides, inclusions have sufficient time to float. However, many enterprises, only aluminum wire or aluminum scrap, and then sprinkle metal surface, and not cover, would not be wasted! During this period, in time to adjust the carbon and manganese to the manganese and carbon content. Before the molten steel is baked, it is necessary to bake the ladle above 400 ℃. In the baked during the V-Fe, Ti-Fe, rare earth and other trace elements to do metamorphic treatment, is to make a crystal refinement of the necessary means, its impact on product performance is essential. 4, charge and molding materials to extend the furnace order, when the distinction between steel and the lining of the property. Manganese steel is alkaline, of course, the use of magnesia lining material. Pounding the lining to turn again and again to change operation. Add lining materials can not be too thick, about 80 cm each time is appropriate, to complete a long time to bake baking. Such as improving production efficiency, I recommend the use of forming crucible, from the demolition furnace ramming into, not 1 hour, you can put into production, while forming the crucible on the benefit of anti-wear furnace. Of course, the length of the furnace and the operator has a great relationship. Many operators like throwing the same athletes, the charge from 34 meters into the furnace outside, not safe and hurt furnace order, the furnace should be placed in the mouth next to the preheat, and then slowly with the clip charge Along the furnace placed in the mouth next to the preheat, and then slowly with the clip along the furnace wall into the furnace. Modeling materials and coatings should also be consistent with the properties of liquid metal, or with ZTE materials (such as chromite sand, corundum, etc.). If you want to get a crystal refinement of the collective, the use of large thermal storage of chromite sand is correct, especially the EPC production plant, with it will overcome the shortcomings of slow cooling. 5, the casting process design Manganese steel is characterized by large solidification shrinkage, heat dissipation is poor, accordingly, in the process of casting shrinkage taken 2.5% -2.7%, casting the more grow up, the more should take the ceiling. Sand and sand core of the concession must be better. Gating system to take open. A plurality of discrete runners are introduced from the thin wall of the casting and have a flat, wide, trumpet-like shape with a cross-sectional area near the casting which is greater than the cross-sectional area associated with the runner so that the molten metal is quickly and smoothly injected into the mold , To prevent the mold temperature difference is too large. Riser diameter is greater than the diameter of the hot section, close to the hot section, the height is 2.5-3.0 times the diameter, must be hot riser or pouring riser, so that sufficient high-temperature liquid metal casting to shrink in the empty space . The sprue, the riser at a high (sand box with 5-8. The slope) is also correct. Pouring as fast as possible low temperature. Once the solidification, to timely loose sand box. Smart designers are always good at using cold iron, including iron in the cold inside the cold iron, which not only refine a crystal, eliminating shrinkage, shrinkage, and improve the process yield, of course, the appropriate dosage and specifications should be considered of. Inner iron to be clean, fusible, the amount of less suitable. The three dimensional dimension of the outer cold iron is a function of 0.6 to 0.7 times the three dimensional dimension of the coolant. Too small does not work, too big cause casting cracking. Casting in the type of long-term insulation, until less than 200 ℃ and then open the box. 6, heat treatment Heat treatment cracking, is the low temperature phase caused by too fast. So the correct operation is below 350 ℃, the heating rate of <80 ℃ / h, 750 ℃ the following, <100 ℃ / h, and have different periods of insulation. To> 750 ℃, the casting was plastic state, you can quickly heat up. To 1050 ℃ according to the thickness of the casting to determine the holding time, and then rose to 1100 ℃ or more. Give the furnace cool down and leave room for water as soon as possible. When the temperature is too slow to heat up, holding time is too short, after baked into the water time interval is too long (not> 0.5min), all of which affect the quality of castings. Water temperature should be <30 ℃, quenching, the water temperature <50 ℃, the water should not be less than 8 times the weight of the casting. Cold water from the pool into the bottom, warm water from the pool top surface outflow. Casting in the pool to keep moving in three directions. 7, cutting and welding Because of poor thermal conductivity of manganese steel, so cut the riser should pay great attention. Casting is best placed in the water, was cutting part of the exposed water, cutting a certain amount of stubble, heat treatment after grinding off. Many plants, welding and welding become inevitable. Selection of austenitic manganese-nickel electrode (D256 or D266 type), specifications slender, φ3.2mm × 350mm, the outer coating is alkaline. Operation using small current, weak arc, a small bead and more welding, and always maintain a low temperature, less heat method of operation. While welding while striking, eliminating stress. Important castings must be inspected. 8, the production considerations Attention to the producers, not only to reduce production costs, but more importantly, no waste, the maximum quality products, and then to maximize the expansion of occupation of market share. This seems to be slow and costly, in fact, fast and provincial, this concept not only recognizes that more important is to do. Third, the use of High manganese steel is designed for heavy industry to provide a use of anti-wear steel, applications include quarrying, mining, mining, coal industry, casting and steel industries. Other First, quarrying, mining, mining and mining industry Gravel, top, hammer, backhoe bucket, conveyor belt, link belt, lifting bucket, quarry truck base, gravel production line, bulldozer, Sandblasting cleaning equipment, waste treatment equipment performance characteristics by anti-wear technology, the material surface can reach 500 - 550 Brinell hardness, continue to maintain the internal Flexibility, surface friction to minimize the available high manganese steel or similar materials for welding, can be acetylene torch cutting, non-magnetic and so on.
