different spheroidization methods for ductile iron

There are different spheroidization methods to choose in the production of ductile iron,today Anyang Huatuo Metallurgy will introduce different spheroidization methods to you,the foundries can choose according to their production condition.

1.Pressure plus magnesium method.According to the different pressurization methods, it can be divided into external pressurization and self pressurization.The external pressure type used in the early days is to place the processing bag full of molten iron in a closed pressure tank, and the required pressure is established by compressed air or nitrogen.The other is to use magnesium vapor to build up pressure in the molten iron ladle by adding pure magnesium into the sealed molten iron ladle. Magnesium quickly generates a large amount of magnesium vapor in the molten iron ladle. When this vapor passes through the molten iron, a part of it is absorbed by the molten iron. Absorption, the other part escapes and quickly establishes a saturated vapor pressure corresponding to the temperature of the molten iron in the inner space of the bag, and at this time, magnesium is no longer boiled and vaporized and lost.

2.Infusion method.It is the most widely used spheroidizing treatment method at home and abroad.In order to reduce the intensity of the reaction between molten iron and magnesium and the volatilization rate of magnesium vapor, the infusion method usually uses alloy nodularizers with lower magnesium content.During the spheroidizing treatment, first put the spheroidizing agent into one side of the dam, cover it with ferrosilicon alloy, tighten it a little, and then cover it with rust-free iron filings, steel plates or other covering agents.en spheroidizing, the molten iron should be flushed into the other side of the molten iron ladle as much as possible. The absorption rate of magnesium by the infusion method is generally 30% to 50%. In order to improve the spheroidizing effect, the ratio of the height to the diameter of the treatment package can be increased; the low magnesium alloy spheroidizing agent can be used; the temperature of the molten iron and the covering dosage can be reasonable.

3.Cored wire feeding method.The application of the wire feeding method to produce ductile iron castings is simply to insert the cored wire covered with magnesium and other alloying elements directly into the molten iron for spheroidization to produce ductile iron. The entire spheroidization process can be completely automation.The diameter of the commonly used cored wire is generally 9mm and 13mm, and the built-in powder alloy generally contains 25% to 30% of magnesium. When there are special needs, a certain amount of RE, Ca, Ba, etc. are added to improve the performance of the casting.

4.Cover method. It was invented by the British Cast Iron Research Association and it widely used in the production of ductile iron abroad.During the spheroidizing process of the cover bag method, the addition of alloy is the same as that of the punching method, and then the cover is placed on the treatment bag and its periphery is sealed well, and the molten iron is injected into the cover, and the molten iron will pass through the iron on one side of the cover. The liquid injection hole (the molten iron should not be directly aimed at the alloy stacking place) flows into the bag. In this way, the outside gas can be completely isolated from the inside of the bag, the oxidation and burning of magnesium can be reduced, the absorption rate of magnesium can be improved (generally 60% to 65% or more), and the working environment can be improved.

5.Internal method.The spheroidizing agent is placed in the specially designed reaction chamber in the pouring system. During the pouring process, the molten iron flows through the reaction chamber and reacts with the spheroidizing agent for spheroidizing treatment. In order to ensure the stability of the spheroidization treatment and reduce the burning loss, the size of the reaction chamber and the gating system should be strictly calculated. Generally, the reaction chamber is arranged in the runner under the sprue. 

In general, the above spheroidizing treatment methods have their own advantages and disadvantages. It is hoped that each ductile iron casting manufacturer can comprehensively evaluate each spheroidizing treatment method according to their own production conditions, make use of their strengths and avoid weaknesses, and choose their own spheroidization treatment method. , to ensure the quality of ductile iron.