Detection method for qualified molten iron in Mediate frequency melting inductionfurnace smelting
Mediate frequency heating furnaces are used to heat metal for forging or metal heat treatment services; Mediate frequency induction melting furnaces are used to melt metals for casting services. In the process of melting metal in the Mediate frequency furnace, in order to obtain qualified molten steel. Three items of testing are required before the furnace: analysis of the chemical composition of the molten steel, detection of the temperature of the molten steel, and judgment of the deoxidation quality of the molten steel.
1. Analysis of the chemical composition of molten steel
Mediate frequency furnace ironmaking and steelmaking process must be equipped with rapid chemical analysis before the furnace, so that samples can be sampled and tested at any time according to needs, and reliable data can be obtained to control the melting process of the intermediate frequency furnace. For carbon steel, the five major elements of carbon, silicon, manganese, sulfur and phosphorus are mainly analyzed; for alloy steel, in addition to these five major elements, the alloy elements contained in it still need to be assayed.
When analyzing the composition of molten steel in front of the intermediate frequency furnace, the required time is short, and the residence time of molten steel in the furnace should be minimized to prevent the inhalation of molten steel and the burning of elements. If the analysis finds that the chemical composition does not meet the standard requirements, it is necessary to add various ferroalloy elements to adjust to meet the requirements.
2. Detection of molten steel temperature
The temperature of molten steel is one of the important process parameters in the steelmaking process of intermediate frequency furnace, the measurement and judgment of molten steel temperature. It can be carried out in the furnace or outside the furnace; it can be measured with high-precision instruments, or it can be judged by empirical methods; it can measure the temperature in gaps. Continuous temperature measurement is also possible.
Generally, a thermocouple is used to measure the temperature of molten steel, and the thermocouple is composed of two thermoelectric wires of different metal materials. One end of the two wires is welded together, and the other end is connected in series with a millivolt meter or potentiometer to form a closed circuit. When the welding end of the thermocouple is heated and there is a temperature difference between the two ends, a thermoelectric potential is generated in the circuit. The temperature is determined from the thermoelectric potential.
The thermocouple wires that can be used to measure the temperature of molten steel include platinum-rhodium, tungsten-molybdenum, tungsten-rhenium, iridium-rhodium, tungsten-iridium, and indium-rhenium. Platinum-rhodium thermocouples and tungsten-molybdenum thermocouples are commonly used in production. The temperature measurement limit of the former is 1600～1800℃, and the temperature measurement limit of the latter is 2000℃. In order to avoid corrosion and bonding of molten steel when thermocouples are in use, a protective tube needs to be installed on the top of the thermocouple wire in contact with molten steel. The materials used for the protection tube include quartz, silicon carbide, zirconia, and berkelium carbide. Among them, quartz tubes are commonly used.
3. Judgment of molten steel deoxidation quality
Before the final deoxidation with aluminum, take the molten steel pouring round cup sample to judge the deoxidation situation. Casting molds are generally made of steel, and sand molds are also used. The degree of deoxidation of molten steel is determined according to the shrinkage of the round cup during the solidification process.