Compacted graphite cast iron appeared in the 1960s as a new type of cast iron material. my country is one of the earliest countries to study vermicular graphite cast iron. In 1966, Shandong Mechanical Design Institute published a paper on rare earth high-strength gray cast iron, marking the successful development of vermicular graphite iron production technology in my country.
So far, research results at home and abroad agree that rare earths are the dominant elements in the production of compacted graphite cast iron. my country is rich in rare earth resources, which provides extremely favorable conditions and material foundation for the development of vermicular graphite cast iron in my country.
Because compacted graphite iron has the properties of both ductile iron and gray cast iron, it has unique uses in steel ingot molds, automobile engines, exhaust pipes, glass molds, diesel engine cylinder heads, and brake parts. Applications in other areas have achieved good results. In particular, the commissioning of the compacted graphite cast iron exhaust pipe assembly line of my country's second automobile plant marks that my country's compacted graphite cast iron production has reached a high level.
So far, it is difficult to estimate the world's output of compacted graphite cast iron. This is because compacted graphite cast iron is often counted within the output of gray cast iron, rather than from a separate project. The annual output of vermicular graphite cast iron in my country is not exact, but is approximately tens of thousands of tons.
The vermigating agents used in the production of vermicular graphite cast iron in my country all contain rare earth elements, such as rare earth ferrosilicon magnesium alloys, rare earth ferrosilicon alloys, rare earth calcium silicon alloys, rare earth zinc magnesium ferrosilicon alloys, etc. As a result, a series of creeping agents suitable for national conditions has been formed.
my country is in a leading position in the research on the formation mechanism of vermicular graphite cast iron. In addition, extensive and in-depth research has been conducted on the processing technology of compacted graphite cast iron, molten iron smelting and furnace quality control, and the normal and high temperature properties of compacted graphite cast iron. It should be pointed out in particular that under the conditions of cupola furnaces in my country, many factories can stably produce vermicular graphite cast iron and have achieved significant economic benefits. It can be expected that the use of compacted graphite cast iron's good comprehensive properties, high mechanical properties, high strength at high temperatures, small oxidation growth, dense structure, high thermal conductivity and low cross-section sensitivity to replace some of the High-grade gray cast iron, ductile iron and malleable iron will achieve good technical and economic results.
The brand name is: RuT Gray cast iron (referred to as gray cast iron) is a new type of engineering structural material characterized by good mechanical properties and thermal conductivity as well as low cross-section sensitivity.
Brief history In 1947, the British H. Morrogh discovered worm-like graphite while studying the use of cerium to treat ductile iron (ductile iron for short). Since Moreau's research work at that time and later focused on how to obtain spherical graphite and its properties, worm-like graphite was considered to be the product of failure to process ductile iron. In 1955, Americans J.W. Estes and R. Schneidenwind first proposed the use of vermicular graphite cast iron (referred to as vermicular iron); in 1966, Scherlen (R.D. Schelleng) continued to propose the application of vermicular iron. A 1965 U.S. patent mentioned that by adding an alloy to the molten iron containing 0.05% to 0.06% magnesium, 0.15% to 0.50% titanium, and 0.001% to 0.015% rare earth metals, a worm-like graphite structure can be obtained. . By 1976, the American Foote Mining Company formulated these elements into a Mg-Ti series alloy in a certain proportion and supplied it to the market as a commodity, called "Foote" alloy. Therefore, vermicular iron has more industrial applications. application. In the 1960s, the Austrians studied the impact of rare earths on molten iron and obtained a reliable method for producing vermicular iron. They obtained an Austrian patent in 1968. In the 1960s, China added rare earth ferrosilicon alloys to high-carbon molten iron, and found that the macroscopic fracture surfaces of some of the samples were "spotted" and the graphite was worm-shaped. Its performance exceeded the HT300 index in the Chinese standard. In view of the shortage of scrap steel sources in domestic high-grade gray cast iron production at that time, no scrap steel was added, and only rare earth ferrosilicon alloys were used to directly process cupola high-carbon molten iron to produce high-grade gray iron castings. This became the starting point of the research at that time. During the experiment, it was discovered that the strength of cast iron with worm-like graphite was greatly improved, thus obtaining high-strength gray cast iron without adding scrap steel.
Since the above-mentioned high-grade cast iron is obtained by treating it with rare earth, it has been named as rare earth high-grade gray cast iron, rare earth (gray) cast iron, etc. Since 1965, China has consciously researched and applied vermicular graphite as a new engineering material. In the late 1970s, based on the morphology of graphite seen under an optical microscope and striving to unify the nomenclature with foreign countries, China called it worm-shaped graphite cast iron, also known as vermicular graphite cast iron. The "Vermicular Graphite Cast Iron Committee" was established at the 44th Annual International Foundry Conference in 1977, and the name of this cast iron was also unified as "Compact Vermicular Graphite Cast Iron".
The mechanical properties depend on the creeping state of graphite and the matrix structure, among which the creeping state of graphite has the greatest influence. ——Steel House