Nodulizer is the main means to obtain ductile iron. This article will briefly analyze the classification and properties of nodularizers.
Classification of nodulizers
According to the output of ductile iron castings, nodulizers can be divided into alloy-like nodulizers, block nodulizers, core wire nodulizers, and powder nodulizers.
1. Alloy-like nodulizer
Including magnesium-silicon alloy, magnesium-silicon alloy, calcium alloy (used more in Japan), nickel-magnesium alloy, pure magnesium alloy and rare earth alloy.
The most widely used alloys in the world are rare earth-magnesium-silicon alloys.
However, the ratio of rare earth to magnesium in Chinese foundries is 0.5~2.2, and that in foreign countries is 0.1~0.3.
1.1.1 Calcium alloy
Calcium and magnesium nodularizers are mainly used by Japanese casting manufacturers.
Production of Shin-Etsu (SHIN-ETSU), NC5, NCl0, NCl5, NC20, NC25, the magnesium content changed from 4% to 28%. However, calcium levels did not vary much; they ranged from 20% to 31%. This type of alloy has a small tendency to white mouth, but requires high processing temperature and a large amount of residue after treatment.
1.1.2 Nickel-magnesium alloy
Nickel-magnesium alloys are produced by International Nickel Corporation. The nickel content is as high as 82-85%, calcium 20%, magnesium 13%-16%. However, the nickel content is as low as 57% to 61% (of which Mg 4.0 ~ 4.5%, Ca <2.5%, Fe 32 ~ 36%). German chemical company produces nickel-magnesium alloys, of which Ni 47~51%, Mg l5~17%, C1.0% Si28~32%, RE1.0%. The advantages of these alloys are that they are heavy, the reaction is stable, and nickel alloys can act as alloys. But it is characterized by high price, and this alloy is basically not used in Chinese foundries in China.
1.1 Nickel-silicon alloy
Nickel-silicon alloys are basically not used in China at present.
1.2 Pure magnesium alloy
The processing of pure magnesium alloy requires a special die-casting magnesium bag, which has a high magnesium absorption rate. But it requires very strict security handling, resulting in a smaller percentage of production applications.
1.3 Rare earths
When the iron foundry invented ductile iron, rare earths were used, which greatly promoted the industrial application of ductile iron.
But the price is high, and the chilling tendency is large. If the installation is finished, the graphite will deteriorate. So now it is no longer used as a nodularizer alone, only as an auxiliary element.
2. Bulk spheroidizer
Direct compression molding to the designed magnesium and iron and silicon content. The silicon content in this spheroidizer is very low. Therefore, it is called a low-pressure block spheroidizer, which provides a follow-up space for cast iron, which is beneficial to the production of cast iron. However, this alloy is easy to float, and the treatment effect is unstable. So it’s better to use with bulk nodulizer.
3. Core wire spheroidizing machine
The magnesium powder and iron powder are coated on the thin steel plate or steel plate and poured into the molten iron to achieve the purpose of forming a ball. But this nodulizer is expensive, the equipment investment is large, and the alloy absorption rate is high, so the cost of processing ductile iron hardly increases.
4. Power spheroidizing machine
The power spheroidizer is a Russian patent. Mix the magnesium powder and inhibitor into the bag. The molten iron flows over the surface of the alloy and reacts with the alloy layer and layer. Iron foundries call this special process MC.
Each nodulizer has its own advantages and disadvantages. The cast iron factory should choose the appropriate nodulizer according to its own products and production processes to reduce investment costs and improve production efficiency.