CN101341262A

CN101341262A - Process for production of compacted graphite iron

Info

Publication number: CN101341262A
Application number: CNA2006800481058A
Authority: CN
Inventors: R·西伦
Original assignee: NOVACAST TECHNOLOGIES AB
Current assignee: NOVACAST TECHNOLOGIES AB
Priority date: 2005-12-20
Filing date: 2006-12-14
Publication date: 2009-01-07
Anticipated expiration: 2026-12-14
Also published as: SE0502817L; MX2008007968A; EP1974062A1; KR20080089577A; EP1974062B1; US20120090803A1; BRPI0620077A2; WO2007073280A1; SE529445C2; US20090183848A1; CN101341262B

Abstract

A process for production of compacted graphite iron using in-mould addition of a magnesium alloy is disclosed. The process is characterised by a step of pre-treating the base iron in a ladle or in a furnace with an alloy containing cerium and performing a structure forming treatment in a reaction chamber in the mould using an alloy containing magnesium and lanthanum.

Description

The manufacture method of vermicular cast iron

Technical field

The present invention relates to the manufacture method of cast iron, this cast iron has the main structure that is made of the graphite shape of compacting.This method combines based on the pre-treatment of base iron and final processing in mould.

Background technology

Vermicular cast iron be have between the flake graphite shape and spherical between the cast iron alloy of graphite-structure.Graphite shape is by the conditional decision in the molten steel solidification process.Handle the base iron preferably have 4.0 to 4.4 carbon equivalent and to be lower than 0.02% sulphur content with the iron silicon alloy that contains 4-10% magnesium, can obtain the graphite-structure of compacting.Mg content must remain on usually in+extremely narrow limit in/-0.003%, and is about 0.008 to 0.015% according to the situation of base iron with rate of cooling in the foundry goods that will make.Per-cent used herein is meant weight percent.Usually in ladle, carry out with the processing that magnesium carries out.The magnesium boiling point is 1090 ℃, and because the temperature of iron is usually above 1400 ℃ in treating processes, so therefore some magnesium disappear as steam, and some combine with sulphur, oxygen and nitrogen in the iron.In the iron put procedure before cast, the content of activated carbon further reduces.This minimizing gradually of activated carbon is known as disappears.

For fear of these problems, magnesium is handled and can be carried out at each mould inside.The technology that is known as processing/technology in the mould is known during spheroidal graphite cast iron is made.This technology of particular form described in WO 01/54844 A1 is fit to the manufacturing of vermicular cast iron.Technology is based on magnesium alloy being put into the indoor of die casting system in the mould.In casting process, flowing molten iron is gone into this chamber and is dissolved this alloy gradually.The metal of handling is filled casting cavity then.When making in this way, eliminated the problem that magnesium disappears.

A problem is that the sulphur content in the base iron usually changes.Therefore, must regulate Mg content.But this almost is impossible when handling in using mould, because the treatment chamber in each mould is identical.Another problem is, the processing of carrying out with magnesium makes the variation sensitivity of this structure to rate of cooling.Under high rate of cooling, for example in the thin part of foundry goods, it is spherical that graphite shape more is tending towards.Under long-term rate of cooling, promptly in thicker part, graphite is with flaky precipitate.

Be known that the processing alloy that contains magnesium and cerium has alleviated these problems.But the high-content of cerium can increase the danger of some casting defect, for example forms primary carbides and contraction.

Summary of the invention

The objective of the invention is to address these problems.

The present invention relates to according to adding the method for making vermicular cast iron in the mould that utilizes magnesium alloy of claim 1.Define preferred embodiment in the dependent claims.

The amount of regulating cerium explicitly with the sulphur content in the base iron.Should regulate cerium content according to following formula:

% cerium=(% sulphur-0.006) * 2.9+A

According to the structure of foundry goods, i.e. the variation of sectional dimension and casting modulus, the preferably change between 0.01 to 0.03 of the value of A.Because cerium has high boiling point (3470 ℃) and high density (6.14 gram/cubic centimetre), it does not show any extinction effect.By cerium is added in the base iron, it can suitably dissolve, and because cerium also has the shaping structures effect, therefore can add less magnesium alloy in the reaction chamber of mould.

Handle alloy and preferably contain the magnesium of 3-6% and the lanthanum of 0.5-1.5%.Lanthanum has the advantageous effect that reduces defective (for example carbide and contraction) in the foundry goods.It is the highest to the influence of shrinking just to have handled the back, therefore preferably adds lanthanum as far as possible lately.

Used alloy can have various compositions, because most important key element is total ratio of reactive metal.But the example of the composition of commercial alloys comprises:

For magnesium alloy: 48%Fe, 45%Si, 5%Mg, 1.0%Al, 0.5%La and 0.5%Ca and

All the other rare earth elements for cerium alloy: 65%Fe, 25%Ce, 7%La and surplus.

According to the preferred embodiments of the invention, cerium is added in stove or the ladle (and be not as magnesium alloy a part), and magnesium is added in the mould.

Use the method proposed, with do not have preregulated common mould in handle and compare, the addition of magnesium is reduced by at least 30%.

The Mg content that reduces in the foundry goods is favourable, and for example making, the casting defect of scum silica frost and little contraction and so on minimizes.

Claims

1. utilize and add the method for making vermicular cast iron in the mould of magnesium alloy, it is characterized in that ladle or in stove with the alloy pre-treatment base iron that contains cerium, and use the alloy that contains magnesium and lanthanum to carry out shaping structures in the reaction chamber in mould and handle.

2. the process of claim 1 wherein with the alloy pre-treatment base iron that contains cerium reaching 0.008 to 0.025% cerium content, and in mold, use the alloy that contains 3-6% magnesium and 0.5-1.5% lanthanum further to handle iron.

3. claim 1 or 2 method, wherein the minimum percent of cerium is calculated according to (%S-0.006) * 2.9+0.01 in the base iron, and wherein S adds the sulphur content in the iron before the cerium.