Quality and selection of the hottest rare earth no

Quality and selection of rare earth nodulizing agent (2)

configuration of 1, 2, 1 nodulizing elements

composition preparation principles and characteristics: to have strong nodulizing ability, it is obvious that magnesium is the main component, and the boiling point of magnesium is low. Adding it to molten iron can make molten iron churn violently and react evenly up and down; After alloying, the specific gravity is increased to make it difficult to float in molten iron, which can reduce the oxidation and burning loss of magnesium. The ability of digesting and neutralizing anti spheroidizing elements. Rare earth elements have strong abilities of desulfurization and degassing, purifying molten iron and eliminating anti spheroidizing elements. Moreover, China is rich in rare earth resources, and the cost of obtaining raw materials is low. The nodulizer reaction is stable and easy to operate. Although calcium cannot be used alone as a nodulizer, using it to form a composite nodulizer with magnesium and rare earth can not only reduce the content of MgO in the nodulizer, make the nodulizing treatment stable, but also reduce the large white mouth tendency caused by rare earth. Therefore, the principle and characteristics of the composition of spheroidizing agent are to give full play to the advantages of various spheroidizing elements to improve the spheroidizing effect, and to meet the needs of castings with different production conditions and structures by adjusting the content of spheroidizing elements

1, 2, 2 kinds of spheroidizing agents

according to the principle of spheroidizing and anti spheroidizing element configuration, a variety of spheroidizing agents have been developed at home and abroad, generally including the following: pure magnesium: This is a commonly used spheroidizing agent abroad, and its domestic application is relatively small. The advantages and disadvantages of producing ductile iron by adding magnesium under pressure are also obvious. Copper magnesium, nickel magnesium: this alloy was used in early China, but the cost is high, and the accumulation of copper and nickel in the returned material is difficult to control, resulting in a decline in toughness. Silicon magnesium iron alloy: generally, the lowest magnesium content is 3.54.5%, and the highest is 1015%. The commonly used alloys are magnesium 510%, silicon 4247%, and the rest are pastes. The lower the magnesium content is, the smoother the spheroidization reaction is, and the higher the magnesium recovery rate is (the recovery rate of magnesium containing 4% can be higher than that of 9% alloy magnesium). Langsheng high performance materials business department (hereinafter referred to as "HPM") is a leading supplier of high-tech plastics by 10%. However, the low magnesium spheroidizing agent is the increase of silicon content in molten iron. The nodulizer is used to treat molten iron with low content of sulfur and anti nodulizing elements and cast castings with medium section thickness. At present, large quantities of nodular cast iron to be used in the manufacturing of nodular cast iron in China will have a certain contradiction with the production conditions and raw material procurement of China's casting enterprises. Rare earth magnesium alloys: including rare earth silicon magnesium, rare earth calcium magnesium, rare earth copper magnesium and other alloys, are rare earth magnesium alloy spheroidizing agents developed by Chinese engineers in the early 1960s based on China's reality. They integrate the advantages and disadvantages of various spheroidizing elements, especially rare earth magnesium calcium alloys. They are the main spheroidizing agents widely used in China at present, Thus, a manufacturing technology road of nodular cast iron suitable for China's national conditions has been found

2. Production control points of nodulizer quality

at present, the rare earth nodulizer used in China mainly includes pyrometallurgy, cored wire method, briquetting method, mechanical mixing method, etc. according to the processing and manufacturing methods, and pyrometallurgy is the basis of the latter methods, and it is also the main method of producing rare earth nodulizer. Using this method to produce spheroidizing agent, the key points of quality control mainly include the following aspects:

2. 1 raw material preparation

rare earth ferrosilicon alloy: This is the only source of rare earth elements in the spheroidizing agent, which requires no moisture, no pulverization, uniform composition and no inclusions. Rare earth ferrosilicon containing% rare earth is the most commonly used. It is introduced that high silicon rare earth ferrosilicon (commonly known as one-step production of rare earth ferrosilicon, containing 55% silicon) and commonly used low silicon rare earth ferrosilicon (commonly known as two-step production of rare earth ferrosilicon, containing% silicon) are used to produce spheroidizing agent. Under laboratory conditions, the microstructure and properties of the nodular iron prepared are basically the same, which can meet the production requirements with a warranty period of generally 6 years. However, the tensile strength of the former is slightly higher, while the latter has a large amount of ferrite, which should be paid attention to in use. Of course, this still needs further verification of industrial mass production

metallic magnesium: magnesium mainly exists in the Mg Si alloy phase in the alloy, which is conducive to reducing the oxidation and burning loss of magnesium. Magnesium in alloys can also be divided into effective magnesium and ineffective magnesium. Ineffective magnesium mainly refers to magnesium oxide. Therefore, it is required that the raw material metal magnesium still has a long way to go. It must have high purity (first-class magnesium, containing more than 99.7% magnesium), less impurities and cannot be oxidized. Ferrosilicon: it is required to have low aluminum, dense structure, no pulverization, no inclusions, and ferrosilicon with the national standard below 75 is refractory and has many impurities, so it is not suitable for use. Calcium silicon and barium silicon: it is mainly to determine and control the precise content of Ca and BA in the alloy. A small amount of Ca and Ba will increase the invalid oxidation. Click the "run" button on the main interface of the control software to increase the content of magnesium, resulting in intense combustion, increased white mouth tendency and rapid decay of the nodulizer when used. Scrap steel: carbon steel and silicon steel are generally used, and other alloy steels are prohibited, because the alloy elements therein may be anti spheroidizing elements, and production is not easy to control. In addition, scrap steel is required to be free of oil, rust and pollution, especially iron rust is easy to be reduced to magnesium oxide by magnesium