How to measure furnace temperature for zinc alloy die casting?

Zinc alloy melting is an important part of the die-casting process. The melting process is not only to obtain molten metal, but also to obtain the chemical composition that meets the requirements. Zinc alloy die-casting parts can obtain good crystalline structure and gas. Correct zinc alloy die-casting process specification is an important guarantee for obtaining high-quality castings< br /> 1、 The best melting temperature for zinc alloy die-casting: the melting point of zinc alloy for die-casting is 382~386 ℃, and the appropriate temperature control is an important factor for the control of zinc alloy composition. In order to ensure the good fluidity of the alloy liquid to fill the cavity, the temperature of the molten metal in the zinc pot of the die-casting machine is 415~430 ℃, and the upper limit of the die-casting temperature of thin-walled parts and complex parts can be taken; The lower limit can be taken for thick wall parts and simple parts. The temperature of molten metal in the central smelting furnace is 430~450 ℃. The temperature of molten metal entering the gooseneck is basically the same as that in the zinc pot. The pouring temperature can be accurately controlled by controlling the molten metal temperature of the zinc pot< br /> 2、 (When the melting temperature is too high) the reaction between the iron crucible and the zinc liquid is accelerated, and the oxidation reaction of iron occurs on the surface of the crucible to produce oxides such as Fe2O3; Iron will also react with zinc liquid to form FeZn13 compound (zinc slag), which is dissolved in zinc liquid. Burning loss of aluminum and magnesium elements,
The rate of metal oxidation increases, the burning loss increases, and the zinc slag increases. The hammer head will be stuck due to thermal expansion. The iron element in the cast iron crucible is melted into the alloy more, and the reaction between zinc and iron is accelerated at high temperature. It will form hard particles of iron-aluminum intermetallic compound, causing excessive wear of hammer head and gooseneck. The iron element in the cast iron crucible is melted into the alloy more, and the reaction between zinc and iron is accelerated at high temperature. It will form hard particles of iron-aluminum intermetallic compound, causing excessive wear of hammer head and gooseneck. Fuel consumption increased accordingly. The higher the temperature, the coarser the crystallization of the casting and the lower the mechanical properties< br /> 3、 (When the melting temperature is too low) the fluidity of the alloy is poor, which is not conducive to forming and affects the surface quality of the die casting< br /> 4、 (How to keep the temperature stable) The current melting pot or furnace of the die-casting machine is equipped with a temperature measurement and control system, which is regularly checked to ensure the accuracy of the temperature measuring instrument, and the actual temperature of the furnace is regularly measured with a portable thermometer (thermometer) for correction. Experienced die-casting workers observe the molten liquid with the naked eye. If the molten liquid is not too viscous and clear after scraping, and the slag is not very fast, it means that the temperature is appropriate; If the molten liquid is too thick, the temperature is low; After slag scraping, a layer of white frost will soon appear on the liquid surface, and the slag is too fast, indicating that the temperature is too high, which should be adjusted in time. The best method is to use the central smelting furnace and the die-casting machine furnace as the holding furnace, so as to avoid the large temperature change caused by directly adding zinc ingots into the zinc pot for melting. Centralized melting can ensure the stability of alloy composition. Alternatively, the advanced automatic feeding system of molten metal can maintain a stable feeding speed, the temperature of molten alloy and the liquid level of zinc pot. If the material is directly added in the zinc pot, it is suggested to change the addition of the whole alloy ingot at one time to the addition of small alloy ingots several times, which can reduce the temperature change caused by the material addition< br /> 5、 (Control of zinc slag) It is a complex physical and chemical process to melt the alloy from solid to liquid. The gas reacts with the molten metal chemically, and the reaction of oxygen is the strongest. The alloy surface is oxidized to produce a certain amount of scum. The scum contains oxides and intermetallic compounds of iron, zinc and aluminum. The scum scraped from the melt surface usually contains about 90% zinc alloy. The reaction rate of zinc slag formation increases exponentially with the increase of smelting temperature. Under normal conditions, the slag yield of the original zinc alloy ingot is less than 1%, within the range of 0.3~0.5%; The slag yield of remelting nozzle and waste workpiece is usually between 2% and 5%