Metal founding – Process – With measuring – testing – inspecting – or condition determination
Patent
1986-05-07
1987-05-26
Godici, Nicholas P.
Metal founding
Process
With measuring, testing, inspecting, or condition determination
164150, 164154, B22D 4600
Patent
active
046677259
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for producing cast-iron containing structure modifying additives, and preferably additives which will cause carbon to precipitate in vermicular graphite form.
Vermicular graphite is defined as "Form III"-graphite in ISO/R 945-1969, and alternatively "Type IV"A according to ASTM Specification A 247.
Cast-iron is one of the most essential materials in industrial casting processes, and upon solidifying may precipitate carbon in cementite, Fe.sub.3 C form, to form white cast-iron or in graphite form, to form grey cast-iron. White cast-iron is brittle, but has a high compression strength and is highly resistant to wear. Grey cast-iron can be readily worked and has an extremely wide field of use within machine technology. In grey cast-iron graphite is normally precipitated in flake form. This results in a cast-iron of limited rupture strain (0.5%). Grey cast-iron has good thermal conductivity, but undergoes permanent changes in volume at elevated temperatures, which restricts its use for some purposes. Consequently, attempts have been made to change the morphology of the precipitated graphite, by incorporating certain additives. In this respect, magnesium, or magnesium in combination with rare earth metals like cerium, has normally been used, these modifying additives preventing the growth of flaky graphite and resulting in a graphite in the form of small spheroids or nodules. This material is known as nodular cast-iron or spheroidal-nodular iron. The use of nodular iron as a construction material has grown widely within the construction field. Additional developments within this field have involved the creation of other graphite morphologies, of which the majority have obtained but limited technical use. It has been found, however, that so-called compacted graphite cast-iron, or so-called vermicular iron, has properties which render it of particular interest, and which give it a superiority over grey cast-iron and nodular iron in respect of many different areas of use. Minor deviations from desired additive quantities and the presence of impurities, however, are factors which make it impossible to use cheap raw materials, and hence manufacture has been restricted to a few foundries which have built-up an expertise by carrying out large numbers of tests and experiments and by using raw materials and additives which are well defined through experience and which are often expensive.
There is therefore an obvious need for a method by means of which preparation of any molten bath of cast-iron material can be controlled in a manner to bring the bath to solidify to vermicular iron with a reproduceable result.
In the casting of metals, great importance is placed on the composition of the molten bath, although the physical state and other factors influencing the course followed by crystallisation of the bath-constituents are also factors of decisive importance with respect to the final properties of the end product.
The chemical composition of the bath, such as alloying elements, impurities, gas content, etc., can be quickly monitored and checked with the aid of modern analysis apparatus, enabling necessary corrections to be made.
On the other hand, however, no method has yet been fully developed by means of which it is possible to predict and control swiftly and reliably the nature of the crystal structure which a given bath of molten material will obtain upon solidifying under prevailing solidification conditions, even though many experiments and tests carried out to this end are found described in the relevant literature, and many patent applications relating to such methods have been filed.
Casting materials can be divided into two main groups, depending on the nature of the solidification process, of which main groups the first includes material which solidify in a single phase (primary solidification processes). This group incorporates most types of steel, aluminium alloys and copper alloys. The other group incorporates materials which solidify in two or more phases (secon
REFERENCES:
patent: 4333512 (1982-06-01), Sugiura et al.
patent: 4598754 (1986-07-01), Yen et al.
Godici Nicholas P.
Heinrich Samuel M.
Sinter-Cast AB
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