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Inoculation alloy against micro-shrinkage cracking for treating cast iron castings

Inactive Publication Date: 2005-08-18
PECHINEY ELECTROMETALLURGIE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012] The purpose of the invention is to provide inoculating alloys that can be used to treat liquid cast iron enabling efficien

Problems solved by technology

Since the casting time of a part is very short, the dissolution kinetics of the slugs must be very fast.
These defects make parts more brittle; moreover, if the parts have to be machined afterwards, for example to straighten a surface, the presence of such a defect on the surface will inevitably make it necessary to scrap the defective parts.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0030] A treated cast iron ladle originating from the preliminary operation was inoculated in the ladle using a powder inoculating alloy with a size grading between 2 and 10 mm, with a “Foundry Grade” composition, the remainder being mainly Fe, used at a dose of 200 g per tonne of cast iron.

[0031] This cast iron was used to cast V parts with geometry identical to that defined in the control test, arranged in clusters in a 36-part sand mould supplied by an inlet duct in which there is a filter composed of a refractory foam.

[0032] The parts obtained were examined by optical microscopy on a polished section to determine the metal structure as a function of the porosity depth and level.

[0033] The density of graphite modules at the heart of the branches was measured at 120 / mm2.

[0034] The average porosity of the parts was evaluated at 2.4%.

example 2

[0035] A second treated cast iron ladle from the preliminary operation was inoculated in the ladle using an inoculating alloy with a size grading of between 2 and 10 mm of composition: [0036] Si=75.4%, Al=0.94%, Ca=0.86%, La=2.2%, Bi=0.92%, remainder mainly Fe, used at a dose of 200 g per tonne of cast iron.

[0037] This iron was used to cast V parts with geometry identical to that defined in the control test, arranged in clusters in a 36-part sand mould supplied by an inlet duct in which there is a filter composed of a refractory foam.

[0038] The parts obtained were examined by optical microscopy on a polished section to determine the metal structure as a function of the porosity depth and level. The density of graphite modules at the heart of the branches was measured at 360 / mm2.

[0039] The average porosity of the parts was evaluated at 0.3%.

example 3

[0040] A third treated cast iron ladle originating from the preliminary operation was used to cast V parts with geometry identical to that defined in the control test, arranged in clusters in a 36-part sand mould supplied by an inlet duct in which 25 g slug is located composed of an inoculating alloy for treatment in the mould, with composition: [0041] Si=73.6%, Al=3.92%, Ca=0.78%, La=2.1%, Bi=0.97%, remainder mainly Fe. The parts obtained were examined by optical microscopy on a polished section to determine the metal structure as a function of the porosity depth and level. The density of graphite modules at the heart of the branches was measured at 320 / mm2.

[0042] The average porosity of the parts was evaluated at 0.2%.

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Abstract

Inoculation alloys for treating cast iron castings containing, by weight, 0.005% to 3% of an element selected from the group consisting of bismuth, lead and antimony, 0.3 to 10% of metals of the rare-earth group and optionally aluminum up to 5%, and calcium up to 1.5%, the remainder being ferro-silicon, lanthanum constituting more than 90% of the rare-earth metals contained in the composition. The inventive alloys enable efficient inoculation of cast iron and avoid occurrence of micro-shrinkage cracking in the cast parts. The alloys are conditioned in the form of slugs or powder.

Description

DOMAIN OF THE INVENTION [0001] The invention relates to the treatment of liquid cast iron for manufacturing parts for which it is required to obtain a structure with no iron carbides and no micro-shrinkage cavities. STATE OF THE ART [0002] Cast iron is a well-known iron-carbon-silicon alloy widely used for manufacturing of mechanical parts. It is known that to obtain good mechanical properties of these parts, it is important to eventually obtain an iron+graphite structure, minimising the formation of Fe3C type iron carbides that make the alloy hard and brittle. [0003] It may be desirable for the graphite formed to be spheroidal, vermiform or lamellar, but the essential prior condition to be satisfied is to avoid the formation of iron carbide. To achieve this, the liquid cast iron is subjected to an inoculation treatment before casting, that facilitates the appearance of graphite rather than iron carbide during cooling. [0004] Therefore the inoculation treatment is very important. It...

Claims

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Application Information

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IPC IPC(8): B22D5/00B22D27/20C21C1/08C21C1/10C22C28/00C22C29/18C22C37/10
CPCB22F2998/00C21C1/08C21C1/105C22C28/00C22C37/10B22F1/0003B22F1/0014B22F1/09B22F1/052C21C1/10
Inventor MARGARIA, THOMAS
Owner PECHINEY ELECTROMETALLURGIE
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