Zinc alloy melting is an important part of the die-casting process, the melting process is not only to obtain molten metal liquid, more importantly, get the chemical composition in line with the provisions of zinc alloy die casting can get good crystal structure and gas. The correct zinc alloy die casting process is an important guarantee for obtaining high quality castings.
First, zinc alloy die-casting The best melting temperature: die-casting zinc alloy melting point of 382 ~ 386 ℃, the appropriate temperature and dwarf control zinc alloy composition is an important factor in the control. In order to ensure good fluidity of the alloy liquid filling cavity, die-casting machine zinc bath metal liquid temperature of 415 ~ 430 ℃, thin-walled parts, complex pieces of die-casting temperature desirable upper limit; thick pieces, simple pieces to take the lower limit. The temperature of the molten metal in the central melting furnace is 430 ~ 450 ℃. The temperature of the molten metal entering the gooseneck is basically the same as that of the zinc pot. The temperature of the molten metal can be controlled by controlling the temperature of the molten metal.
Zinc Die Casting Second, the (melting temperature is too high) iron crucible and zinc solution to speed up the crucible surface oxidation reaction of iron and other oxides of Fe2O3; iron and zinc reaction will be generated FeZn13 compound (dross), dissolved in zinc Liquid. Aluminum, magnesium burns,
Metal oxidation speed, burning increased, increased dross. Thermal expansion will occur stuck hammer phenomenon. Cast iron crucible in the iron element into the alloy more, high temperature reaction of zinc and iron to speed up. Will form iron-aluminum intermetallic compound of hard particles, so that hammer, gooseneck excessive wear. Cast iron crucible in the iron element into the alloy more, high temperature reaction of zinc and iron to speed up. Will form iron-aluminum intermetallic compound of hard particles, so that hammer, gooseneck excessive wear. Fuel consumption increased accordingly. The higher the temperature, the larger the casting and the mechanical properties.
Third, (when the melting temperature is too low) alloy fluidity is poor, is not conducive to forming, affecting the surface quality of die castings.
Zinc Die Casting Four, (how to maintain the stability of the temperature) Now die-casting machine melting pot or furnace are equipped with temperature measurement and control system, regular inspection to ensure the accuracy of temperature measurement equipment, regularly with a portable thermometer (thermometer) measured furnace actual temperature, to be Correction. Experienced die-casting trade union with the naked eye to observe the melt, if the scraping that the melt is not too thick, but also more clear, from the slag is not very fast, indicating the appropriate temperature; melt is too thick, then the temperature is low; Slag liquid level soon after a layer of white frost, from the slag too fast, indicating that the temperature is high, should be adjusted. The best way is to use the central melting furnace, die-casting furnace furnace for the insulation furnace, so as to avoid zinc in the zinc directly into the melting of zinc caused a significant temperature changes. Concentrated melting to ensure that the alloy composition is stable. Or the use of advanced metal liquid automatic feeding system, to maintain a stable feed rate, the temperature of the alloy liquid and zinc pot liquid level. If it is in the zinc pot directly feeding, it is recommended to add a whole alloy ingot to add a few pieces of alloy ingot, can reduce the temperature range caused by feeding.
Zinc Die Casting Five, (control of the dross) by melting the alloy from the solid state to the liquid, is a complex physical and chemical process. Gas and molten metal chemical reaction, in which the reaction of oxygen is the most intense, the alloy surface is oxidized to produce a certain amount of scum. The scum contains oxides and iron, zinc, and aluminum intermetallics, and scum scraped from the surface of the melt usually contains about 90% of the zinc alloy. The reaction rate of the dross formation increases exponentially with the melting temperature. Under normal circumstances, the original zinc alloy ingot slag production is less than 1%, in the range of 0.3 to 0.5%; and heavy melting water, waste parts and other slag production is usually between 2% to 5%.