eliminate the harmful effects of interfering elements
Measures to eliminate the harmful effects of interfering elements
When smelting cast iron, the negative effects of interfering elements contained in the charge cannot be ignored. In order to ensure the quality of the castings, necessary countermeasures must be taken.
1.Strictly manage the charge and control the chemical composition of the molten iron. To control the influence of various interfering elements, it is first necessary to determine the location of the problem and determine the content of each element that may cause the problem, and then it is possible to take corresponding countermeasures. If a spectrum analyzer is used, it is very convenient to analyze the content of various alloying elements, trace elements and other interfering elements. It can also dynamically adjust the composition of the molten iron according to the analysis before the furnace to realize real-time control. At present, among the cast iron production enterprises in my country, very few have such conditions. When analyzing quality problems, in addition to C, Si, Mn, P, S five elements, there are not many companies that can measure the content of other alloying elements and trace elements. In the face of the current situation of many variables in the supply of raw materials, when producing castings with high technical content, it is difficult to ensure the quality of castings and make them stable and consistent. From this point of view, it is very necessary for each region to be led by the foundry association to establish technical service centers for production enterprises, and to be equipped with the necessary testing facilities.
2. Suppresses the effects of interfering elements. If ductile iron contains interfering elements, which affect the spheroidization of graphite and cause graphite distortion, its harmful effects can be suppressed by adding alloying elements. In this regard, the first thing to mention is cerium (Ce). Ce is a very active element and can interact with a variety of interfering elements to form compounds with high melting points, such as Ce2Sb2O3, Ce2S3, Ce2Pb, Bi2Ce4, CeAl2, etc., thereby inhibiting its harmful effects. However, the amount of Ce added should be determined through experiments according to the condition of the interfering elements, and should not be too much, otherwise, agglomerated graphite is prone to appear.
3.Use high-purity pig iron for correction.
In the past, when countries in the world produced iron castings with particularly strict requirements, most of them used charcoal pig iron produced in Sweden. The impurity content of this pig iron was very low. Later, due to the rapid increase in the demand for high-quality ductile iron castings in various industries, general casting pig iron was difficult to achieve. To meet this requirement, and the content of various alloying elements in scrap steel continues to increase, the demand for high-purity pig iron is increasingly urgent. Although charcoal pig iron is good, it is expensive and the quantity available is limited, so high-purity pig iron that can be mass-produced has emerged. This kind of pig iron is mainly made by injecting molten iron obtained from blast furnace into converter and blowing with oxygen. The content of various impurities is very low, and the price is quite attractive. The slag produced by blowing high-purity pig iron contains a variety of metal oxides, from which rare and precious metals can be extracted. For example, some iron ore contains vanadium and titanium, and the slag produced when blowing high-purity pig iron is the raw material for refining vanadium and titanium. Therefore, the high-purity pig iron produced by the iron smelting plant can make full use of resources and has a considerable advantage in terms of selling price. The prospect of this type of pig iron is certainly promising.