The difficulty of ferrous metal die cast is that its melting point is higher than nonferrous metal, so the die-casting die and injection system have a poor working condition. Generally die-casting mould has a very short service life, which has a bad influence on the die cast field. Recent years, nonferrous metal die cast grows very fast because of the improvement of the mould material. Now we can manufacture gray iron, iron, nodular cast iron, carbon steel,
stainless steel and alloy steel die casts, and the weight is from dozens to several thousand grams. The mechanical property of ferrous metal die cast is better than sand cast, its dimensional accuracy can reach IT12～IT14 grade and surface roughness Ra0.8～6.3. Foreign ferrous metal die-casting die often use tantalum, zirconium, molybdenum alloy (TZM alloy), which can be used for 10 thousand to 20 thousand times. We always use 3W23Cr4MoV or 3Cr2W8V as molding part material, which can be used for more than 5 thousand times.
When it comes to the choosing of die cast machine, mold structure and die casting parameter, ferrous metal die cast is basically the same as nonferrous metal. The differences are: the preheating temperature of mold is 200℃～250℃, the continuous production temperature is 250 ℃～300 ℃. In order to reduce the heat treatment of die-casting mold and the solidifying contraction of the alloy, we should choose a low temperature of 1550 ℃～1560 ℃. If we use molybdenum alloy, we can improve the mold temperature. Casting temperature. The commonly used ferrous metal casting temperatures are: 1300 ℃～1350 ℃ for cast iron, 1440 ℃～1460 ℃ for medium carbon steel, and alloy steel ferrous metal die casting generally use a higher specific pressure and lower filling speed. Meanwhile, we should choose water-based paint with hot spraying. The gating system of ferrous metal die casting mold should be able to make the metal liquid smoothly go into the mould cavity. The die casting mold will be too hot after long time, so the time for holding pressure and mold stripping should be as short as possible. The gate should be wider and thicker than that of ferrous metal die casting. Usually the thickness of the ingate is 3～5 mm, the width should be about 70% of gate length which was set for the parts. Circular castings are often use ring gates. Although ferrous metal die-casting tech has made some progress, there should be further research and development on the die-casting mold materials and heat treatment, die-casting mold structure, die casting machine and die casting parameters and so on.