Non-magnesium process to produce compacted graphite iron (CGI)

Abstract

The present invention pertains to a non-magnesium process to produce Compacted Graphite Iron (CGI) by placing a treatment alloy into a treatment ladle, and then placing an inoculant over the treatment alloy in the treatment ladle and pouring a molten base metal there over. The treatment alloy comprises iron, silicon and lanthanum, wherein lanthanum is 3-30% by weight of the treatment alloy, silicon is 40-50% by weight of the treatment alloy, and the remaining is Iron. Lanthanum in the treatment alloy makes the graphite precipitate as vermiculite (compacted form) instead of flake or spheroids. With extended process window offered by this new process (0.03-0.1% residual lanthanum in the metal) required to make CGI, this new process removes the stringent process control (0.01-0.02% residual magnesium in the metal) dictated by the magnesium process of making CGI.

Claims

1. A non-magnesium process to produce compacted graphite iron comprising by placing a treatment alloy into a treatment ladle, placing an inoculant there over in the treatment ladle and pouring a molten base metal there over, wherein said treatment alloy comprises iron, silicon and lanthanum, wherein the lanthanum is 3-30% by weight of the treatment alloy, and silicon is 40-50% by weight of the treatment alloy, wherein the treatment alloy optionally comprises at least one of calcium and aluminum in a range of 0.5-3% each by weight of the treatment alloy, and the rest of the treatment alloy is iron, and required additional percentage of said treatment alloy is 0.4-2% by weight of composition of said base metal, and said inoculant is 0.1-0.5% by weight of the composition, wherein the inoculant optionally is a ferrosilicon composition comprising at least one of calcium, aluminum, barium or lanthanum, or combination thereof.

2. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein said lanthanum is in a range of 3-10% by weight of the treatment alloy.

3. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein the treatment alloy comprises at least one of calcium and aluminum or a combination thereof, wherein calcium and aluminum are in a range of 0.5-3% each by weight of the treatment alloy.

4. The non-magnesium process to produce compacted graphite iron according to claim 2, wherein the treatment alloy comprises at least one of calcium and aluminum or a combination thereof, wherein calcium and aluminum are in a range of 0.5-3% each by weight of the treatment alloy.

5. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein said treatment alloy is treated with a base metal which comprises 3-5% carbon by weight of the base metal, 1.5-5% Silicon by weight of the base metal, and less than 0.016% sulphur by weight of base metal.

6. The non-magnesium process to produce compacted graphite iron according to the claim 5, wherein the base metal comprises at least one of manganese, copper, tin, antimony, molybdenum, vanadium or pearlite promoting alloying elements to increase the strength of the metal.

7. The non-magnesium process to produce compacted graphite iron according to claim 6, wherein at least said manganese is in a range of 0.15-0.8% by weight of the base metal, copper is in a range of 0.1-0.8% by weight of the base metal, or tin is in a range of 0.01-0.1% by weight of the base metal, or combination thereof.

8. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein said inoculant is a ferrosilicon composition, the ferrosilicon composition comprising at least one of calcium, aluminum, barium or lanthanum, or combination thereof.

9. The non-magnesium process to produce compacted graphite iron according to claim 2, wherein said inoculant is a ferrosilicon composition, the ferrosilicon composition comprising at least one of calcium, aluminum, barium or lanthanum, or combination thereof.

10. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein adding inoculant is done: by placing on top of the treatment alloy with in the treatment ladle, or during transfer from treatment ladle to pouring ladle, or in instream during pouring into the casting mold, or as blocks or inserts in the mold during casting into the mold.

11. The non-magnesium process to produce compacted graphite iron according to claim 2, wherein adding inoculant is done: by placing on top of the treatment alloy with in the treatment ladle, or during transfer from treatment ladle to pouring ladle, or in instream during pouring into the casting mold, or as blocks or inserts in the mold during casting into the mold.

12. The non-magnesium process to produce compacted graphite iron according to claim 1 is an open pour ladle process wherein the treatment ladle is kept open during the treatment process.

13. The non-magnesium process to produce compacted graphite iron according to claim 2 is an open pour ladle process wherein the treatment ladle is kept open during the treatment process.

14. The non-magnesium process to produce compacted graphite iron according to claim 1, wherein the treatment alloy can be added in the form of lumps, or powder as in cored wires or inserts in in-mold process of producing compacted graphite iron.

15. A non-magnesium process to produce compacted graphite iron comprising by placing a treatment alloy into a treatment ladle, placing an inoculant there over in the treatment ladle and pouring a molten base metal there over, wherein said treatment alloy comprises iron, silicon and lanthanum, wherein the lanthanum is 3-10% by weight of the treatment alloy, and silicon is 40-50% by weight of the treatment alloy, wherein the treatment alloy comprises at least one of calcium and aluminum in a range of 0.5-3% each by weight of the treatment alloy, and the rest of the treatment alloy is Iron, and required additional percentage of said treatment alloy is 0.4-2% by weight of composition of said base metal, and said inoculant is 0.1-0.5% by weight of the composition, wherein the inoculant optionally is a ferrosilicon composition comprising at least one of calcium, aluminum, barium or lanthanum, or combination thereof.

Description

BRIEF DESCRIPTION OF THE DIAGRAMS

(1) FIG. 1 Schematically illustrates the process window one has to maintain tightly while using magnesium during manufacturing CGI. Residual magnesium % required to be maintained is 0.01-0.02.

(2) FIG. 2 Illustrates the schematic of this invention process where metal from the furnace is tapped directly into an open treatment ladle containing treatment alloy and inoculant

(3) FIG. 3 Illustrates this invention process where metal from the furnace is tapped directly into an open treatment ladle containing treatment alloy and inoculant

(4) FIG. 4 Illustrates the wide stable process window range one has to maintain while using this treatment alloy containing lanthanum for the production of CGI. Residual lanthanum % required to be maintained is 0.03-0.1.

(5) FIG. 5 Illustrates typical microstructure of CGI produced by the lanthanum process (a) ferritic grade (b) pearlitic grade

DETAILED DESCRIPTION

(6) Perhaps, the most stringent concern of using magnesium for the production of CGI is that its use requires close control over magnesium percentage during treating the base metal by magnesium as well as during pouring of molds after the magnesium treatment. In other words, the processing window of the magnesium strictly needs to be monitored and additions of required elements for the process are added at very specific timings, keeping the temperature and the reaction in mind.

(7) FIG. 1 according to Dr Steve Dawson in his paper of process control for production of CGI, 106.sup.m AFS casting congress, USA, 2002 illustrates a graphical representation of the nodularity percentage in the cast iron versus the magnesium percentage, to determine at what point the transition from flake to CGI and CGI to ductile iron occurs, This buffer is necessary to ensure that flake-type graphite does not form before the end-of-pouring, which may be as long as fifteen minutes after the initial magnesium addition. The total process window is shown between the line 1 and line 2, which points out for a stable formation of compacted graphite iron, further to A which it would solidify as ductile iron. The stable CGI plateau exists over a range of approximately 0.008% magnesium and is separated from grey iron by an abrupt transition.

(8) This invention, as explained further, helps to remove such stringent controlling factor by removing the magnesium completely from the production procedure and permitting or allowing a longer stable processing window for the production of CGI having a longer/wider stable range for the treatment alloy, percentage makes the process more user friendly.

(9) The best and other modes for carrying out the present invention are presented in terms of the embodiments, herein depicted in FIG. 2 The embodiments are described herein for illustrative purposes and are subject to many variations. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but are intended to cover the application or implementation without departing from the spirit or scope of the present invention. Further, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. Any heading utilized within this description is for convenience only and has no legal or limiting effect.

(10) The terms a and an herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

(11) FIG. 2 illustrates schematic of process flow of manufacturing compacted graphite iron (CGI). Initially, a treatment alloy is placed into a treatment ladle, which is generally an open pour ladle and then placing an inoculant in the treatment ladle and pouring a molten base metal there over. The treatment alloy comprises of iron, silicon and lanthanum, wherein lanthanum is 3-30% by weight of the treatment alloy, silicon is 40-50% by weight of the treatment alloy, and the remaining is iron, hence forming a treatment alloy to be as FeSiLa or ferro silicon lanthanum alloy. The variations of the treatment alloy could also be such as pure lanthanum metal, iron lanthanum alloy, in-mold alloy with finer sizes of above composition of the treatment alloy. Alternatively, a cored wire with 100% lanthanum powder or FeSiLa powder of varying lanthanum percentage or above two mixed with inoculant powder.

(12) As per the FIG. 2 & FIG. 3, metal is melted in an induction furnace with proper chemistry control and wherein the base metal contains 3 to 5% carbon by weight of the base metal, 1.5 to 5% silicon by weight of the base metal and less than 0.016% sulfur by weight of the base metal. Depending on the grade of CGI, base metal may contain manganese in the range of 0.015 to 0.8% by weight of the base metal, and copper in the range of0.1% to 0.8% by weight of the base metal or tin within the range 0.01% to 0.1% by weight of the base metal which could be also in combination thereof with other elements.

(13) According to a preferred embodiment of the non-magnesium process to produce compacted graphite iron, the treatment alloy is 0.4-2% by weight of the composition of the base metal, and the inoculant is 0.1-0.5% by weight of the composition. Inoculation with ferro silicon inoculants is the final stage in the preparation of graphitic irons and involves the introduction of small quantities of ferro silicon inoculant containing elements such as at least calcium, aluminum, barium or lanthanum, or a combination thereof.

(14) The process according to the FIG. 2 & FIG. 3 involves a treatment alloy consisting of a single rare earth element added as a ferrosilicon alloy. The rare earth metal in the treatment alloy is only lanthanum and could vary from 3 to 30%. The typical composition of the alloy could be silicon (Si) of 40 to 50%, and lanthanum (La) from 3 to 30%, the rest could be iron (Fe) along with few recommended additives like calcium (Ca) and aluminum (Al) of 1% each or more as per the quantity required to produce the CGI. In another embodiment, the treatment alloy may have calcium and aluminum in the rage 0.5% to 3% each by weight of the treatment alloy.

(15) The beneficial effects of lanthanum is in reducing chill and carbide formation in any cast iron indicating that the role of lanthanum in rare earth additions used to produce compacted graphite cast iron (CG cast Iron) is important. Mostly it's been seen that rare earth metals are added into the formation of such alloys but in mixture of two or more rare earth metal but it is the focus of this invention to bring out the advantageous of using only lanthanum as a single rare earth metal.

(16) In another embodiment, the inoculant is added during the transfer of metal from the furnace to treatment ladle, or from the treatment ladle to the pouring ladle or in stream during pouring of the ladle into molds or as blocks or inserts into the mold during pouring into the mold cavity, or as blocks or as inserts in the mold during casting into the mold. The treatment ladle could be kept open the whole time of the process. Once the treatment ladle consisting of the treatment alloy and the inoculant is ready, the base metal form the induction furnace is poured into the treatment ladle directly, which then results in compacted graphite iron.

(17) FIG. 4 is an extension to the FIG. 1 and is enabled to show the best range that one can limit to as the wide stable process one has to maintain while using this treatment alloy containing lanthanum for the production of CGI. FIG. 5 is an exemplary image of the results occurred by using this process of using only lanthanum. The images in FIG. 5 are typical microstructure of CGI produced in two grades (a) ferritic grade and (b) pearlitic grade.

(18) Once the treatment process is finished, the metal is then poured into a variations of holdings that could be just another ladle for the convenience or pouring directly into casting molds.

(19) The above-mentioned descriptions represent merely the exemplary embodiment of the present disclosure, without any intention to limit the scope of the present disclosure thereto. Various equivalent changes, alterations or modifications based on the claims of present disclosure are all consequently viewed as being embraced by the scope of the present disclosure.