CA1057086A - Method of treating cast iron - Google Patents
Method of treating cast ironInfo
- Publication number
- CA1057086A CA1057086A CA244,038A CA244038A CA1057086A CA 1057086 A CA1057086 A CA 1057086A CA 244038 A CA244038 A CA 244038A CA 1057086 A CA1057086 A CA 1057086A
- Authority
- CA
- Canada
- Prior art keywords
- alloy
- iron
- weight
- titanium
- magnesium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910001018 Cast iron Inorganic materials 0.000 title claims abstract description 8
- 238000000034 method Methods 0.000 title claims description 21
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 52
- 239000000956 alloy Substances 0.000 claims abstract description 52
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910052742 iron Inorganic materials 0.000 claims abstract description 28
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 24
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims abstract description 11
- 229910052799 carbon Inorganic materials 0.000 claims abstract 2
- 239000010936 titanium Substances 0.000 claims description 35
- 239000011777 magnesium Substances 0.000 claims description 33
- 229910052719 titanium Inorganic materials 0.000 claims description 33
- 229910052749 magnesium Inorganic materials 0.000 claims description 31
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 29
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 26
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 23
- 229910052710 silicon Inorganic materials 0.000 claims description 15
- 239000010703 silicon Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 8
- 150000002910 rare earth metals Chemical class 0.000 claims description 5
- 239000002054 inoculum Substances 0.000 claims 2
- 239000010439 graphite Substances 0.000 abstract description 29
- 229910002804 graphite Inorganic materials 0.000 abstract description 29
- 235000000396 iron Nutrition 0.000 abstract description 12
- 239000000155 melt Substances 0.000 abstract description 8
- 230000035939 shock Effects 0.000 abstract description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 13
- 239000005864 Sulphur Substances 0.000 description 13
- 238000007792 addition Methods 0.000 description 6
- 238000005266 casting Methods 0.000 description 4
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 235000010755 mineral Nutrition 0.000 description 3
- 238000010079 rubber tapping Methods 0.000 description 3
- 229910001021 Ferroalloy Inorganic materials 0.000 description 2
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 2
- 229910001122 Mischmetal Inorganic materials 0.000 description 2
- 229910000805 Pig iron Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- MHKWSJBPFXBFMX-UHFFFAOYSA-N iron magnesium Chemical compound [Mg].[Fe] MHKWSJBPFXBFMX-UHFFFAOYSA-N 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Landscapes
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A quantity of an alloy having 30-80% by weight Si; 3-15% by weight Mg; 3-25% by weight Ti; 0.05-1.0% Ce and the balance Fe, is added, as a single treatment, to molten carbon-containing iron to produce a cast iron with a compacted graphite structure. The cast irons so pro-duced combine the strength and ductility normally associated with nodular graphite irons with the better thermal con-ductivity and resistance to thermal shock normally associated with elongated flake graphite irons. Particularly preferred alloys for use in the invention have a ratio of Mg:Ti between 1:1 and 1:2 by weight, a ratio of Mg:Ce between 50:1 and 2:1 by weight, and are added to the melt in an amount between about 0.8% to 1.8% by weight of the molten iron.
It is also preferred that the melt be innoculated, for ex-ample with ferrosilicon, subsequent to alloy addition.
A quantity of an alloy having 30-80% by weight Si; 3-15% by weight Mg; 3-25% by weight Ti; 0.05-1.0% Ce and the balance Fe, is added, as a single treatment, to molten carbon-containing iron to produce a cast iron with a compacted graphite structure. The cast irons so pro-duced combine the strength and ductility normally associated with nodular graphite irons with the better thermal con-ductivity and resistance to thermal shock normally associated with elongated flake graphite irons. Particularly preferred alloys for use in the invention have a ratio of Mg:Ti between 1:1 and 1:2 by weight, a ratio of Mg:Ce between 50:1 and 2:1 by weight, and are added to the melt in an amount between about 0.8% to 1.8% by weight of the molten iron.
It is also preferred that the melt be innoculated, for ex-ample with ferrosilicon, subsequent to alloy addition.
Description
This invention relates to the manufacture of cast iron with compacted graphite.
Compacted graphite is a preferred name given to flake graphite which has become rounded, thickened and shortened compared with the normal elongated flakes commonly found in grey cast irons. This modified form of graphite has been known by various names including 'compacted', 'vermicular', 'quasi-flake', 'aggregate flake', 'chunky', 'stubby', 'up-graded', 'semi-nodular' and 'floccular' graphite.
Most cast irons have elongated flake graphite structures and such irons are comparati~ely weak and brittle, but have good thermal conductivity and resistance to thermal shock. It is kn ~ , however, that it is possible to produce cast irons having a nodular graphite structure and these are ductile and comparatively strong, but they have lower thermal conductivity and in some circumstances poorer resistance to thermal shock.
Irons with compacted graphite structures combine the hlgh strength and ductility often associated with nodular graphite irons whilst retaining good thermal conductivity and resistance to thermal shock.
Those skilled in the art of iron founding are aware that compacted graphite structures can be produced by alloying with magnesium but the process is difficult to control because of the very narrow range of magnesium contents required to produce the structure (0.015 to 0.02 per cent). Such control is often impracticable and for this reason the process has up to now only had limited commercial use.
Inco and Schelleng (Britlsh Patent Specification No. 1 069 058) who refer to the graphite form as 'vermicular graphite', were able to extend the range of permissible magnesium contents by the addition of 0.15 to 0.5 per cent titanium and 0.001 to 0.015 per cent rare earth metal added separately to the molten iron.
This quantity of titanium is regarded as high, but was .
1057(~86 claimed to be necessary to cover a wide range of magnesium contents (0.005 to 0.06 per cent) whilst avoiding the formation of nodular graphite structures.
.
The usual way of producing compacted graphite irons in which the main added ingredient is magnesium is to add the magnesium as 5-per cent magnesium ferro-silicon containing cerium: the titanium is added either as ferrotitanium or titanium metal in the ladle or as ferrotitanium or titanium-bearing pig iron in the furnace charge. In some cases the cerium is added separately as mischmetall or any other convenient source.
The object of this invention is to provide a method of treating cast iron which can be used to produce compacted graphite structures in the cast iron without the danger of either having too much titanium present ln a low magnesium iron or alternatively, of producing nodular graphite because there is insufficient titanium in the case of a high magnesium.
We aim to improve the reliability with which a cast iron is obtained having the required compacted graphite structure despite deviations from the expected values for the amount of metal treated or the sulphur content of the iron. According to the invention this ?
is achieved, instead of by adding the ingredients separately, by a single treatment of the iron with an alloy containing silicon, magnesium, titanium and a rare earth, the balance being iron.
Preferably the alloy has the following nominal composltions by weight:
Silicon : 30-80%
Magnesium : 3-15%
Titanium : 3-25%
Cerium : 0.05-1.0 Balance : iron ~05708~; :
The ratio of Mg:Ti is preferably between l:l a B 1:2 and the ratio of Mg:Ce may be between 50:1 and but is preferably between 50:1 and 10:1.
The preferred composition is:-Silicon : 40-60%
Magnesium : 4-6%
Titanium : 5-8~
Cerium : 0.1-0.5%
Balance : iron Alloys of the kind embodied in this invention can be produced by a variety of methods well-known for the production of ferroalloys based upon ferrosilicon.
The titanium and cerium (and rare earths, if any) may be incorporated in the alloy by reduction of minerals containing these elements during the smelting process for the ferroalloys. Alternatively, they may be lncorporated by adding metallic master alloys such as mischmetall and titanium metal to the molten ferro-silicon prior to casting into chilled moulds. Another alternative is to reduce the titanium and cerium (and rare earths, if any) from suitable minerals directly into the molten ferrosilicon alloy. The proportion of rare earths which may be present partly replacing the cerium will depend upon the method of producing the alloy, since the cheapest available sources of cerium will be used and will vary according to whether they are mineral or master alloy in origin.
The addition of such an alloy in a single treatment ensures that the quantity of titanium added increases automatically with an increa~e in the quantity of magnesium added so that there is always sufficient titanium present to inhibit the formation of nodular graphite which over-treatment with magnesium might otherwise produce. There is therefore a certain latitude in the quantity of alloy added which makes process control less critical, for example, variations in the quantity of iron treated can be tolerated, and which .4.
thus makes the process more practical for use in commercial foundries.
The alloy will not give titanium contents as high as those speciied in the above-mentioned British Patent Specification No. 1 069 058 and recent work has shown that when the magnesium content is in the range 0.01 to 0~035 per cent, the titanium content need only be in the range 0.06 to 0.15 per cent, and only a trace of cerium is needed.
Preferably the iron is inoculated, for example with ferrosilicon, after the addition of the alloy.
An alloy containing by weight 44.5 per cent silicon, 4.9 per cent magnesium, 6.5 per cent titanium and 0.3 per cent cerium was prepared by melting cerium bearing magnesium-ferrosilicon and adding 7.5 per cent titanium by weight and 1 per cent magnesium to replace any loss of this element during preparation of the alloy. The melt was cast into chill moulds and the solidified alloy subsequently crushed and graded. Graded alloy ~ to 1 inch in size was used in the following examples producing test bars, although coarser grades can be used for treating larger quantities of iron in a commercial foundry.
Example 1 Iron of high purity was melted in an electric furnace and lts composition adjusted to produce an iron of approximately eutectic composition. Four taps were taken from the melt and a different quantity of the alloy (i.e. 0.80%, 1.00%, 1.33% and 1.67~) was added to each by tapping the iron onto the alloy in a casting ladle. Silicon metal was added to the four taps as required to maintain similar final silicon contents.
Each tap was inoculated with 0.25 per cent ferrosilicon prior to pouring.
4 inch diameter test bars were cast from each tap.
Each bar was ultrasonically tested to give a ready indication of its graphite structure and a specimen was .5.
1057086 ~ ~
cut from midway between the edge and centre of each bar and its microstructure examined visually to determine the nature of the graphite structure and classify it. The classification used consists of numbers ranging from 1 to 8, classifications 1 to 4 being flake forms ranging from coarse to fine, classification 5 being fully compacted graphite, classification 6 being mainly compacted graphite with a few nodules but nevertheless still acceptable as compacted graphite, and classifications 7 and 8 being less acceptable as compacted graphite because of the presence of an increasing proportion of nodules. The results obtained and the compos~tion of the respective test bars were as follows:-Alloy C% Si% Mn% S% P% Ti% Mg% Ultra Graphite added ~ - r~ -- _ km/s 0.803.75 2.11 0.18 0.016 0.01 0.060 0.017 5.08 6 1.00 0.015 0.084 0.020 5.03 6 1.33 0.020 0.092 0.022 5.02 6 1.67 0.019 0.129 0.035 5.02 6 /
The similarlty of the ultrasonic velocity figures for all of the test bars reflects the similarity in their graphite structures whlch can be identified as compacted graphite corresponding to a known ultrasonic velocity range of about 4.75 - 5.12 Xm/second in 4 inch diameter test bars. The visual examination confirmedthese results.
Thus, alloy additions ranging from 0.8% to 1.67%
have the desired effect of producing compacted graphite in the treated iron.
Example 2 Iron based on recarbonized steel scrap but of similar composition to that treate~ in Example 1 was .6.
melted and two taps were taken from the melt, each being treated with a different amount of the alloy (i.e. 1.80~ and 1.25%) by tapping onto the alloy in a casting ladle.
12 inch diameter by16 inch test bars were cast and examined ultrasonically and visually as to their graphite structure as in Example 1. The results, and also the composition of the test bars were as follows:-.-Alloy C% Sl~ Mn% S% P% Ti% Mg% Ultra- Graphite added ~ km/sC class t , ,,.... _ ........... ...... . . . ,~
1.80 3.76 1.64 0.22 0.010 0.01 0.074 0.027 4.98 5 . ...... .... ..... .... . . :, 1 25 L o.olg _ 0 052 0 0l~ _ _ These results lndicate that the desired fully compacted graphlte structure was produced in the test bars. The lower ultrasonic velocity corresponds to the coar9er'st~ucture of the graphite in these 12 inch diameter test bars as compared wlth the 4 inch diameter test bars in Example 1.
Exam~le 3 The alloy used in this example contained by weight 44.0 per cent silicon, 5.2 per cent magnesium, 6.9 per ' cent titaniu~ and 0.3 per cent cerium, this being prepared as descrlbed above in'relation to Examples l and 2.
, . .
A melt of high-purity pig iron with an initial sulphur content of 0.014% was treated, a set of five taps being taken from the melt and each being treated With a different amount of the alloy (i.e. 0.50%, 0.73%, ' 1.00%, 1.23% and 1.50%) by tapping onto the alloy in a ~057~)86 casting ladle. Each tap was inoculated with 0.25~
ferrosilicon before being used to cast a 4 inch diameter ~-and a 1.2 inC~ dia~eter test bar.
The 4 inch diameter test bars were examined ultra-sonically and visually as described above in Example 1 and the 1.2 inch diameter bars were only examined visually.
The results, together with composition of the t~st ~`
bars, were as follows:- ~
..... '.................................... , ' ~ .
Alloy C% Si~ Mn% S% P% Ti% Mg% Ultra- Graphite _ added veonlic c] ass _ Xm/s 4 in. 1.2 in.
0 3.76 1.68 0.24 0.014 0.01 ~0.01 _ _ _ _ 0.50 0.013 0.035 0.009 4.00 3 2-3 0.73 0.014 0.054 0.018 4.97 5 5 1.00 0.012 0.066 0.021 5.00 5 5 1.23 0.012 0.074 0.024 5.12 5 5-6 1.50 0.012 0.095 0.031 5.12 5 5-6 . ,... . _ . ~.= ........... .. _ ~ he same melt was then treated so as to increase its sulphur content to 0.030% and another five taps were taken and each treated with a different amount of the alloy as described abo~e, inoculated with 0.25% ferro-sllicon and cast to form a 4 and 1.2 inch diameter test bar whlch were examined as to their graphite structure.
The results were as follows:-.
Alloy C~ Si% Mn% S% P% Ti% Mg% Ultra- Graphite added Senlic cl ass km/s 4 in. 1.2 in.
. .. ... . . .............. . . ..
0 3.72 1.67 0.24 0.03 0.01 <0.01 ~ _ _ _ 0.50 0.025 0.036 0.009 3.44 1 1 0.73 0.025 0.054 0.016 3.47 2 2 1.00 0.025 0.062 0.018 4.06 3 3 1.23 0.025 0.077 0.019 4.86 4-5 3-4 1.50 0.025 0.094 0.022 4.94 5 5 _ Finally, the melt with increased sulphur content was treated again to increase its sulphur content to 0.050% and another five taps were taken and each treated -with a different amount of the alloy as described above, inoculated with 0.25% ferrosilicon and used to form 4 inch and 1.2 inch diameter test bars which were examined as to their graphite structure. The results and com?o~ition of the test bars were as follows:-Alloy C% Si% Mn% S~ P~ Ti% Mg% Ultra Graphite added veonlic c Lass _ _ ~ km/s 4 in. 1.2 in.
0 3.71 1.69 0.24 0.050 0.01 C-0.5 0.047 0.034 0.009 3.43 1 1 0.73 0.047 0.049 0.015 3.55 1 1 1.00 0.041 0.060 0.017 3.81 1 3 1.23 0.042 0.074 0.020 3.96 1 3 `
1.50 0.032 0.091 0.021 3.83 3 3 = _ . . . ' The results obtained using the three series of differing sulphur content can be presented in graphic form as shown in the accompanying drawing, each curve 1, 2, 3 being a plot of the graphite classification against the quantity of added alloy for a particular sulphur content 0.014%, 0.030~, 0.050%, respectively.
The graph uses the results obtained from examination of the 4 inch diameter test bars, not the 1.2 inch diameter test bars.
.
These results show that an increasing quantity of alloy is required with increasing sulphur content to produce compacted graphite. They also show that compacted graphite can be obtained with additions of between 1.25 per cent and 1.5 per cent with base sulphur contents of 0.014 per cent and 0.03 per cent. Therefore, if it is .. . . ~ .
~ ` ~
1~)57086 only known that the sulphur content of the iron to be treated is below 0.03 per cent, the quantity of alloy to be added can be calculated on the assumption that the sulphur content is 0.03 per cent. If the sulphur content in fact lies below 0.03 per cent, the risk of over-treatment (excess magnesium) to give nodular graphite will be minimised by the simultaneous addition of titanium which the alloy provides.
Irons containing more than 0.03 per cent sulphur are preferably desulphurised prior to treatment with the alloy rather than treating the irons with larger quantities of the alloy.
It is known that the effect of cerium in producing compacted graphite is also achieved by replacing a proportion of the cerium by other rare earth elements or a mixture of other rare earth elements. Where an amount of cerium is méntioned, in the Examples above and in the claims, it is to be understood that up to approximately half of this amount may be replaced by other rare earth elements, or indeed all the cerium could be replaced by other rare earth although generally it i9 more economical to use cerium.
.10.
,
Compacted graphite is a preferred name given to flake graphite which has become rounded, thickened and shortened compared with the normal elongated flakes commonly found in grey cast irons. This modified form of graphite has been known by various names including 'compacted', 'vermicular', 'quasi-flake', 'aggregate flake', 'chunky', 'stubby', 'up-graded', 'semi-nodular' and 'floccular' graphite.
Most cast irons have elongated flake graphite structures and such irons are comparati~ely weak and brittle, but have good thermal conductivity and resistance to thermal shock. It is kn ~ , however, that it is possible to produce cast irons having a nodular graphite structure and these are ductile and comparatively strong, but they have lower thermal conductivity and in some circumstances poorer resistance to thermal shock.
Irons with compacted graphite structures combine the hlgh strength and ductility often associated with nodular graphite irons whilst retaining good thermal conductivity and resistance to thermal shock.
Those skilled in the art of iron founding are aware that compacted graphite structures can be produced by alloying with magnesium but the process is difficult to control because of the very narrow range of magnesium contents required to produce the structure (0.015 to 0.02 per cent). Such control is often impracticable and for this reason the process has up to now only had limited commercial use.
Inco and Schelleng (Britlsh Patent Specification No. 1 069 058) who refer to the graphite form as 'vermicular graphite', were able to extend the range of permissible magnesium contents by the addition of 0.15 to 0.5 per cent titanium and 0.001 to 0.015 per cent rare earth metal added separately to the molten iron.
This quantity of titanium is regarded as high, but was .
1057(~86 claimed to be necessary to cover a wide range of magnesium contents (0.005 to 0.06 per cent) whilst avoiding the formation of nodular graphite structures.
.
The usual way of producing compacted graphite irons in which the main added ingredient is magnesium is to add the magnesium as 5-per cent magnesium ferro-silicon containing cerium: the titanium is added either as ferrotitanium or titanium metal in the ladle or as ferrotitanium or titanium-bearing pig iron in the furnace charge. In some cases the cerium is added separately as mischmetall or any other convenient source.
The object of this invention is to provide a method of treating cast iron which can be used to produce compacted graphite structures in the cast iron without the danger of either having too much titanium present ln a low magnesium iron or alternatively, of producing nodular graphite because there is insufficient titanium in the case of a high magnesium.
We aim to improve the reliability with which a cast iron is obtained having the required compacted graphite structure despite deviations from the expected values for the amount of metal treated or the sulphur content of the iron. According to the invention this ?
is achieved, instead of by adding the ingredients separately, by a single treatment of the iron with an alloy containing silicon, magnesium, titanium and a rare earth, the balance being iron.
Preferably the alloy has the following nominal composltions by weight:
Silicon : 30-80%
Magnesium : 3-15%
Titanium : 3-25%
Cerium : 0.05-1.0 Balance : iron ~05708~; :
The ratio of Mg:Ti is preferably between l:l a B 1:2 and the ratio of Mg:Ce may be between 50:1 and but is preferably between 50:1 and 10:1.
The preferred composition is:-Silicon : 40-60%
Magnesium : 4-6%
Titanium : 5-8~
Cerium : 0.1-0.5%
Balance : iron Alloys of the kind embodied in this invention can be produced by a variety of methods well-known for the production of ferroalloys based upon ferrosilicon.
The titanium and cerium (and rare earths, if any) may be incorporated in the alloy by reduction of minerals containing these elements during the smelting process for the ferroalloys. Alternatively, they may be lncorporated by adding metallic master alloys such as mischmetall and titanium metal to the molten ferro-silicon prior to casting into chilled moulds. Another alternative is to reduce the titanium and cerium (and rare earths, if any) from suitable minerals directly into the molten ferrosilicon alloy. The proportion of rare earths which may be present partly replacing the cerium will depend upon the method of producing the alloy, since the cheapest available sources of cerium will be used and will vary according to whether they are mineral or master alloy in origin.
The addition of such an alloy in a single treatment ensures that the quantity of titanium added increases automatically with an increa~e in the quantity of magnesium added so that there is always sufficient titanium present to inhibit the formation of nodular graphite which over-treatment with magnesium might otherwise produce. There is therefore a certain latitude in the quantity of alloy added which makes process control less critical, for example, variations in the quantity of iron treated can be tolerated, and which .4.
thus makes the process more practical for use in commercial foundries.
The alloy will not give titanium contents as high as those speciied in the above-mentioned British Patent Specification No. 1 069 058 and recent work has shown that when the magnesium content is in the range 0.01 to 0~035 per cent, the titanium content need only be in the range 0.06 to 0.15 per cent, and only a trace of cerium is needed.
Preferably the iron is inoculated, for example with ferrosilicon, after the addition of the alloy.
An alloy containing by weight 44.5 per cent silicon, 4.9 per cent magnesium, 6.5 per cent titanium and 0.3 per cent cerium was prepared by melting cerium bearing magnesium-ferrosilicon and adding 7.5 per cent titanium by weight and 1 per cent magnesium to replace any loss of this element during preparation of the alloy. The melt was cast into chill moulds and the solidified alloy subsequently crushed and graded. Graded alloy ~ to 1 inch in size was used in the following examples producing test bars, although coarser grades can be used for treating larger quantities of iron in a commercial foundry.
Example 1 Iron of high purity was melted in an electric furnace and lts composition adjusted to produce an iron of approximately eutectic composition. Four taps were taken from the melt and a different quantity of the alloy (i.e. 0.80%, 1.00%, 1.33% and 1.67~) was added to each by tapping the iron onto the alloy in a casting ladle. Silicon metal was added to the four taps as required to maintain similar final silicon contents.
Each tap was inoculated with 0.25 per cent ferrosilicon prior to pouring.
4 inch diameter test bars were cast from each tap.
Each bar was ultrasonically tested to give a ready indication of its graphite structure and a specimen was .5.
1057086 ~ ~
cut from midway between the edge and centre of each bar and its microstructure examined visually to determine the nature of the graphite structure and classify it. The classification used consists of numbers ranging from 1 to 8, classifications 1 to 4 being flake forms ranging from coarse to fine, classification 5 being fully compacted graphite, classification 6 being mainly compacted graphite with a few nodules but nevertheless still acceptable as compacted graphite, and classifications 7 and 8 being less acceptable as compacted graphite because of the presence of an increasing proportion of nodules. The results obtained and the compos~tion of the respective test bars were as follows:-Alloy C% Si% Mn% S% P% Ti% Mg% Ultra Graphite added ~ - r~ -- _ km/s 0.803.75 2.11 0.18 0.016 0.01 0.060 0.017 5.08 6 1.00 0.015 0.084 0.020 5.03 6 1.33 0.020 0.092 0.022 5.02 6 1.67 0.019 0.129 0.035 5.02 6 /
The similarlty of the ultrasonic velocity figures for all of the test bars reflects the similarity in their graphite structures whlch can be identified as compacted graphite corresponding to a known ultrasonic velocity range of about 4.75 - 5.12 Xm/second in 4 inch diameter test bars. The visual examination confirmedthese results.
Thus, alloy additions ranging from 0.8% to 1.67%
have the desired effect of producing compacted graphite in the treated iron.
Example 2 Iron based on recarbonized steel scrap but of similar composition to that treate~ in Example 1 was .6.
melted and two taps were taken from the melt, each being treated with a different amount of the alloy (i.e. 1.80~ and 1.25%) by tapping onto the alloy in a casting ladle.
12 inch diameter by16 inch test bars were cast and examined ultrasonically and visually as to their graphite structure as in Example 1. The results, and also the composition of the test bars were as follows:-.-Alloy C% Sl~ Mn% S% P% Ti% Mg% Ultra- Graphite added ~ km/sC class t , ,,.... _ ........... ...... . . . ,~
1.80 3.76 1.64 0.22 0.010 0.01 0.074 0.027 4.98 5 . ...... .... ..... .... . . :, 1 25 L o.olg _ 0 052 0 0l~ _ _ These results lndicate that the desired fully compacted graphlte structure was produced in the test bars. The lower ultrasonic velocity corresponds to the coar9er'st~ucture of the graphite in these 12 inch diameter test bars as compared wlth the 4 inch diameter test bars in Example 1.
Exam~le 3 The alloy used in this example contained by weight 44.0 per cent silicon, 5.2 per cent magnesium, 6.9 per ' cent titaniu~ and 0.3 per cent cerium, this being prepared as descrlbed above in'relation to Examples l and 2.
, . .
A melt of high-purity pig iron with an initial sulphur content of 0.014% was treated, a set of five taps being taken from the melt and each being treated With a different amount of the alloy (i.e. 0.50%, 0.73%, ' 1.00%, 1.23% and 1.50%) by tapping onto the alloy in a ~057~)86 casting ladle. Each tap was inoculated with 0.25~
ferrosilicon before being used to cast a 4 inch diameter ~-and a 1.2 inC~ dia~eter test bar.
The 4 inch diameter test bars were examined ultra-sonically and visually as described above in Example 1 and the 1.2 inch diameter bars were only examined visually.
The results, together with composition of the t~st ~`
bars, were as follows:- ~
..... '.................................... , ' ~ .
Alloy C% Si~ Mn% S% P% Ti% Mg% Ultra- Graphite _ added veonlic c] ass _ Xm/s 4 in. 1.2 in.
0 3.76 1.68 0.24 0.014 0.01 ~0.01 _ _ _ _ 0.50 0.013 0.035 0.009 4.00 3 2-3 0.73 0.014 0.054 0.018 4.97 5 5 1.00 0.012 0.066 0.021 5.00 5 5 1.23 0.012 0.074 0.024 5.12 5 5-6 1.50 0.012 0.095 0.031 5.12 5 5-6 . ,... . _ . ~.= ........... .. _ ~ he same melt was then treated so as to increase its sulphur content to 0.030% and another five taps were taken and each treated with a different amount of the alloy as described abo~e, inoculated with 0.25% ferro-sllicon and cast to form a 4 and 1.2 inch diameter test bar whlch were examined as to their graphite structure.
The results were as follows:-.
Alloy C~ Si% Mn% S% P% Ti% Mg% Ultra- Graphite added Senlic cl ass km/s 4 in. 1.2 in.
. .. ... . . .............. . . ..
0 3.72 1.67 0.24 0.03 0.01 <0.01 ~ _ _ _ 0.50 0.025 0.036 0.009 3.44 1 1 0.73 0.025 0.054 0.016 3.47 2 2 1.00 0.025 0.062 0.018 4.06 3 3 1.23 0.025 0.077 0.019 4.86 4-5 3-4 1.50 0.025 0.094 0.022 4.94 5 5 _ Finally, the melt with increased sulphur content was treated again to increase its sulphur content to 0.050% and another five taps were taken and each treated -with a different amount of the alloy as described above, inoculated with 0.25% ferrosilicon and used to form 4 inch and 1.2 inch diameter test bars which were examined as to their graphite structure. The results and com?o~ition of the test bars were as follows:-Alloy C% Si% Mn% S~ P~ Ti% Mg% Ultra Graphite added veonlic c Lass _ _ ~ km/s 4 in. 1.2 in.
0 3.71 1.69 0.24 0.050 0.01 C-0.5 0.047 0.034 0.009 3.43 1 1 0.73 0.047 0.049 0.015 3.55 1 1 1.00 0.041 0.060 0.017 3.81 1 3 1.23 0.042 0.074 0.020 3.96 1 3 `
1.50 0.032 0.091 0.021 3.83 3 3 = _ . . . ' The results obtained using the three series of differing sulphur content can be presented in graphic form as shown in the accompanying drawing, each curve 1, 2, 3 being a plot of the graphite classification against the quantity of added alloy for a particular sulphur content 0.014%, 0.030~, 0.050%, respectively.
The graph uses the results obtained from examination of the 4 inch diameter test bars, not the 1.2 inch diameter test bars.
.
These results show that an increasing quantity of alloy is required with increasing sulphur content to produce compacted graphite. They also show that compacted graphite can be obtained with additions of between 1.25 per cent and 1.5 per cent with base sulphur contents of 0.014 per cent and 0.03 per cent. Therefore, if it is .. . . ~ .
~ ` ~
1~)57086 only known that the sulphur content of the iron to be treated is below 0.03 per cent, the quantity of alloy to be added can be calculated on the assumption that the sulphur content is 0.03 per cent. If the sulphur content in fact lies below 0.03 per cent, the risk of over-treatment (excess magnesium) to give nodular graphite will be minimised by the simultaneous addition of titanium which the alloy provides.
Irons containing more than 0.03 per cent sulphur are preferably desulphurised prior to treatment with the alloy rather than treating the irons with larger quantities of the alloy.
It is known that the effect of cerium in producing compacted graphite is also achieved by replacing a proportion of the cerium by other rare earth elements or a mixture of other rare earth elements. Where an amount of cerium is méntioned, in the Examples above and in the claims, it is to be understood that up to approximately half of this amount may be replaced by other rare earth elements, or indeed all the cerium could be replaced by other rare earth although generally it i9 more economical to use cerium.
.10.
,
Claims (13)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of treating molten carbon-containing iron to produce a cast iron with a compacted graphite structure com-prising adding to the molten iron in a single step a quantity of an alloy containing silicon, magnesium, titanium and a rare earth, the balance being iron, the alloy containing silicon, magnesium, titanium and a rare earth in amounts to produce cast iron with a compacted graphite structure.
2. A method according to Claim 1 in which the alloy has the following nominal composition by weight:
Silicon : 30-80%
Magnesium: 3-15%
Titanium : 3-25%
Cerium : 0.05 - 1.0%
Balance : Iron
Silicon : 30-80%
Magnesium: 3-15%
Titanium : 3-25%
Cerium : 0.05 - 1.0%
Balance : Iron
3. A method according to Claim 2 in which the ratio of mangesium to titanium in the alloy is between 1:1 and 1:2 by weight.
4. A method according to Claim 2 in which the ratio of magnesium to cerium is between 50:1 and 2:1 by weight.
5. A method according to Claim 4 in which the ratio of magnesium to cerium is between 50:1 and 10:1 by weight.
6. A method according to Claim 2 in which the alloy has the following nominal composition by weight:
Silicon : 40-60%
Magnesium: 4-6%
Titanium : 5-8%
Cerium : 0.1-0.5%
Balance : Iron
Silicon : 40-60%
Magnesium: 4-6%
Titanium : 5-8%
Cerium : 0.1-0.5%
Balance : Iron
7. A method according to Claim 1 in which the alloy is added to the extent of 0.8% to 1.8% by weight of the molten iron.
8. A method according to Claim 1 in which, after the addition of the alloy, the iron is treated with an inoculant.
9. A method according to Claim 8 in which the inoculant is ferrosilicon.
10. An alloy for use in the method according to Claim 2 the alloy being of the following nominal composition by weight:
Silicon : 30-80%
Magnesium : 3-15%
Titanium : 3-25%
Cerium : 0.05-1.0%
Balance : Iron
Silicon : 30-80%
Magnesium : 3-15%
Titanium : 3-25%
Cerium : 0.05-1.0%
Balance : Iron
11. An alloy for use in the method according to Claim 3 the alloy being of the following nominal composition by weight:
Silicon : 40-60%
Magnesium : 4-6%
Titanium : 5-8%
Cerium : 0.1-0.5%
Balance : Iron
Silicon : 40-60%
Magnesium : 4-6%
Titanium : 5-8%
Cerium : 0.1-0.5%
Balance : Iron
12. A method according to Claim 7 in which the amount of the alloy added is such as to produce a final titanium content in the treated iron of less than 0.15% by weight.
13. A method according to Claim 12 in which the amount of the alloy added is such as to produce a final titanium content in the treated iron of between 0.06 and 0.15% by weight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,038A CA1057086A (en) | 1976-01-21 | 1976-01-21 | Method of treating cast iron |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,038A CA1057086A (en) | 1976-01-21 | 1976-01-21 | Method of treating cast iron |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057086A true CA1057086A (en) | 1979-06-26 |
Family
ID=4105033
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA244,038A Expired CA1057086A (en) | 1976-01-21 | 1976-01-21 | Method of treating cast iron |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1057086A (en) |
-
1976
- 1976-01-21 CA CA244,038A patent/CA1057086A/en not_active Expired
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