CA1283030C - Process for producing a low alloy white cast iron and product resulting therefrom - Google Patents
Process for producing a low alloy white cast iron and product resulting therefromInfo
- Publication number
- CA1283030C CA1283030C CA000511175A CA511175A CA1283030C CA 1283030 C CA1283030 C CA 1283030C CA 000511175 A CA000511175 A CA 000511175A CA 511175 A CA511175 A CA 511175A CA 1283030 C CA1283030 C CA 1283030C
- Authority
- CA
- Canada
- Prior art keywords
- alloy
- slugs
- product
- iron
- silicon
- 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 - Lifetime
Links
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 66
- 239000000956 alloy Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 37
- 229910001037 White iron Inorganic materials 0.000 title claims abstract description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 43
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 22
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 21
- 235000000396 iron Nutrition 0.000 claims abstract description 17
- 229910052742 iron Inorganic materials 0.000 claims abstract description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 14
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 14
- 239000011651 chromium Substances 0.000 claims abstract description 14
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 13
- 239000010703 silicon Substances 0.000 claims abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000010791 quenching Methods 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229920000620 organic polymer Polymers 0.000 claims abstract description 10
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 9
- 239000007788 liquid Substances 0.000 claims abstract description 9
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 8
- 238000005266 casting Methods 0.000 claims abstract description 7
- 238000002844 melting Methods 0.000 claims abstract description 7
- 230000008018 melting Effects 0.000 claims abstract description 7
- 230000000171 quenching effect Effects 0.000 claims abstract description 7
- 230000009466 transformation Effects 0.000 claims abstract description 6
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims abstract description 4
- 241000237858 Gastropoda Species 0.000 claims description 41
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 15
- 239000011733 molybdenum Substances 0.000 claims description 12
- 229910000734 martensite Inorganic materials 0.000 claims description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 9
- 229910052802 copper Inorganic materials 0.000 claims description 9
- 239000010949 copper Substances 0.000 claims description 9
- 229910001018 Cast iron Inorganic materials 0.000 claims description 3
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 claims description 2
- 239000000047 product Substances 0.000 claims 20
- 235000016768 molybdenum Nutrition 0.000 claims 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims 7
- 229910052748 manganese Inorganic materials 0.000 claims 7
- 235000002908 manganese Nutrition 0.000 claims 7
- 239000011572 manganese Substances 0.000 claims 7
- 229910000881 Cu alloy Inorganic materials 0.000 claims 2
- 229910001182 Mo alloy Inorganic materials 0.000 claims 2
- 235000019589 hardness Nutrition 0.000 description 18
- 238000005275 alloying Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 1
- 229910000616 Ferromanganese Inorganic materials 0.000 description 1
- 229910018487 Ni—Cr Inorganic materials 0.000 description 1
- 229910000805 Pig iron Inorganic materials 0.000 description 1
- 241001201614 Prays Species 0.000 description 1
- CUXOXWIOJSVENR-UHFFFAOYSA-N [Cu].[Mo].[Mn].[Si].[C] Chemical compound [Cu].[Mo].[Mn].[Si].[C] CUXOXWIOJSVENR-UHFFFAOYSA-N 0.000 description 1
- JAPNAHDTYXQWPO-UHFFFAOYSA-N [Ni].[Cr].[Mn].[Si].[C] Chemical compound [Ni].[Cr].[Mn].[Si].[C] JAPNAHDTYXQWPO-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- VNNRSPGTAMTISX-UHFFFAOYSA-N chromium nickel Chemical compound [Cr].[Ni] VNNRSPGTAMTISX-UHFFFAOYSA-N 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- 238000011020 pilot scale process Methods 0.000 description 1
- ZLIBICFPKPWGIZ-UHFFFAOYSA-N pyrimethanil Chemical compound CC1=CC(C)=NC(NC=2C=CC=CC=2)=N1 ZLIBICFPKPWGIZ-UHFFFAOYSA-N 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D5/00—Heat treatments of cast-iron
- C21D5/04—Heat treatments of cast-iron of white cast-iron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/06—Cast-iron alloys containing chromium
- C22C37/08—Cast-iron alloys containing chromium with nickel
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
Abstract of the Disclosure A process for producing a low alloy white cast iron is disclosed. The process comprises the steps of melting an alloy consisting essentially of about 2.5 to 4.0% carbon, 0.3 to 0.8% silicon, 0.3 to 0.8% manganese, 0.75 to 2.0% nickel and O to 0.75% chromium, the balance being iron except for incidental impurities commonly found in cast irons; casting such alloy into moulds to produce the desired product; removing the product from the moulds while its surface temperature is above the transformation temperature of the alloy; and cooling it by quenching into a liquid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
Description
. l2~n3c~
PROCESS FOR PROD~CING A LOW ALLOY WHITE CAST IRON
AND PRODUCT RESULTING THEREFROM
This invention relates to a process for producing a low alloy white cast iron, and more particularly to the production of a low alloy white cast iron for use as grinding media in the form of balls or truncated cones known as "slugs" in the ore processing industry.
Mat~rials used in grinding media applications where wear resistance is required include alloy steels, both cast and forged, and alloy white cast irons in the as-cast and heat treated condition. Alloy white cast irons are divided into two groups, one containing approximately 8 to 30% chromium and the other 0 to 4% chromium. High chromium white cast irons necessitate a special heat treatment above the transformation temperature to allow them to reach their full potential. This heat treatment combined with their high alloy content renders them uneconomical for many ore grinding applications. The other group of white cast irons is generally more economical although an amount of certain alloying elements is required to yield optimum properties.
It is widely recognized that low alloy white cast irons with a microstructure consisting of carbide and martensite offer high wear resistance in most ore grinding applications. Carbide is present in all white cast irons;
martensite, on the other hand, is obtained through a combination of alloy content and processing conditions. If the conditions for martensite formation are not met, an 3(P3~) undesirabl~ pha~e known as pearllte will be produced upon cooli~ from the transfo~ation temperature. Many alloying elements have been used over the years to avoid the formation of pearllte~ These elements are used either alone or in the combined form, and they include nickel, chromium, molybdenum, copper, manyanese and vanadium.
Because o~ its outstanding wear r2sistance, a nickel-chromium white cast iron known as Ni-Har~ has been ~uccass~ully used ~or ovar Xorty years to make grlnding medla. The microstructur~ o~ Ni-Hard consist~ essentially o~ oarbide and martensite, and its hardnes~ i~ 600 Brinell in the chill cast and stress relieved condition.
Compositional ranges suggested for the manufacture of Ni~
Hard grinding ball~ and 51ug8 are about 3~ carbon, 0.5 ~ilicon, 0.5% manganes~, 1.5-4% nickel and 1.0-2 chromium, the re~t being iron.
A low alloy white cast iron having a hardness and a microstructure similar to those o~ Ni-Hard was disclo~ed in applicant's Canadian Patent No. 1,125,056. ~he alloying ~- 20 elaments were 2.5 to 4% carbon, 0.3 to 0.8% sillcon, 0.3 to 1.0~ manganesa and 1.7 to 3.5% nickel.
The procedure followed for producing the above alloy was as follow: Iron and the above alloying elements were melted in a suitable furnace and cast into moulds. The cast product was sha~en out o~ the moulds at a tempera~ure a~ove the transformation temperaturs and was either cooled with fine water ~prays or sub~ected to forced ai~ or still air cooling to cool it between approximat~ly 1~00F and *is a trademark ~l2~3(~3() ~ 3-400F at a minimum rate of 2.5F/sec. The above combination of alloy content and processing conditions produced an alloy with a microstructure consisting essentially of martensite and carbide with no pearlite.
However, the minimum amount of nickel needed in the above process to avoid the formation of pearlite was 1.7%.
In addition, the hardness of the cast product was not uniform throughout~
Although the above low alloy white cast iron was less lQ expensive than Ni-Hard because it aontained less nickel and no chromium, it was felt that more research was needed to further decrease the nickel content and thus, to develop a more cost-effective alloy for grinding media application. It was also desirable to develop a product having a more uniform hardness.
The process in accordance with the present invention comprises the steps of melting an alloy consisting essentially of about 2.5 to 4~ carbon, 0.3 to 0.8~
silicon, 0.3 to 0.8% manganes~, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except for incidental impurities commonly found in cast irons, casting such alloy into moulds, removing the cast product from the moulds while its surface temperature is above the transformation temperature of the particular alloy white cast iron and cooling it by quenching into a liguid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
; `
. .
~3n30 The above alloy combination and processing conditions produces a microstructure consisting essentially of martensite and carbide with a uniform hardness in excess of 600 Brinell.
The cast product is then subjected to a heat treatment of 4 to 8 hours at 400-600F to transform any retained austenite into martensite and to relieve casting stresses.
In the making of grinding media such as slugs, the size of slugs varies generally but is preferably in the range lQ o~ approximately 1 to 3 in. Alloy content, particularly nickel, and cooling rates are adjusted as a ~unction of slug size: Low alloy content and high cooling rates being used with small slugs and high alloy content and low cooling rates with large slugs. Best results are obtained 5 with the following combinations:
For 1-1/2 in. and smaller slugs: 0.75 to 1.5~
nickel and 0 to 0.5% chromium and cooling rates in the range of 7.5 - 25F per second.
For 2, 2-1/2 and 3 in. slugs: 1.25 to 2% nickel and 0.25 to 0.75% chromium and cooling rates in the range of 2.5 - 7.5'F per second.
The volume of polymer used in the cooling medium is in the range of 5 - 30% and is adjusted so as to provide a controlled rate of cooling which, for a given slug size and alloy content, will prevent the formation o~ pearlite and, at the same time will not generate cracks in the ~inal product. For best results, th2 temperature of the liquid medium is kept in the range of 90 - 130~F.
:~2~33~330 , Before arriving at the preferred embodiment a test program on alloys containing 0.5 ko 3.0% nickel and 0 to 2% chromium was carried out on a pilot scale. Each alloy was based on a cast iron mixture containing approximately 3% carbon, 0.6% silicon and 0.6% manganese, the remainder being iron. Other variables investigated in the test program were the concentration in the range o~ 2.5 - 30%
by volume of the organic polymer and the temperature, in the range of 1200 - 1800F, Erom which the grinding slugs are quenched into the liquid medium.
An example of the procedure followed in the test program will now be disclosed. Metal charges consisting of pig iron, steel scrap, ferro-manganese, ~erro-silicon, nickel and ferro-chrome were melted in a coreless ; 15 induction furnace and poured into cast iron moulds containing either 1-1/2 or 2-1/2 inch slug cavities. The slugs were shaken out of the moulds at 1500F and were quenched immediately into water containing 2.5 - 10% and 10 - 30~ Aqua-Quench* for the 1-1/2 and 2-1/2 in. slugs respectively. The corresponding cooling rates were sstablished using thermocouples inserted into the slug cavities while the metal was still molten and connected to a recording instrument. The as-cast slugs were then subjected to a heat treatment o~ 4 hours at 500F. None o~
the slugs were cracked and their microstructure consisted essentially of martensite and carbide. Table 1 shows the relationship between alloy content, cooling rate and hardness for the heat treated slugs.
*Trade Mark 12~13(~30 -6~
EFFECT OF ALLOY CONTENT AND COOLING RATE
ON THE HARDNESS OF 1-1/2 AND 2-1/2 IN.
GRINDING SLUGS
, Slug~lloy ContentCooling A~erage Sizeweight % Rate Brinell in. Ni Cr F/s Hardness 0.75 0.5 19.3 635 1.0 0.5 19.3 615 `:
~ 1/21.5 0 g.6 635 :
: ~ 1.5 0.25 20.8 680 ! ~ :
; 1.5 0.57.5 690 1.5 0.54.7 615 2-1/2 1.50.75 3.7 650 , . 2.0 0.5 2.4 660 - --- ... _ __ Full scala foundry tests have shown that the new white aast iron of the present invention may be melted and cast using standard foundry practice and casting methods. The ~ ., lZ1~3~30 _7 melting equipment used so far in these full scale tests has been a channel-type induction furnace. However, other melting equipment such as cupolas or various types of electric furnaces could also be used. Tests to date were run on 1-1/8, 1-1/2, 2, 2-1/2 and 3 inch grinding slugs cast in permanent moulds. The composition of the slugs ls given in Table II.
TABLE II
COMPOSITION IN WEIGHT PERCENT OF
GRINDING SLUGS PRODUCED DURING
FULL SCALE FOIJNDRY ~ESTS
.. .. _ Slug Carbon Silicon Manganese Nickel Chromium Size in.
~ 1-1/8 3.6 0.55 0.6 0.9 0.4 ; 1-1/2 3.4 0.55 0.6 0.9 0.4 2 3.2 0.55 0.6 1.4 0.4 - 2-1/2 3.2 0.55 0.6 1.7 0.4 3 3.2 0.55 0.6 1.9 0.4 _ . _ . __ . .
The slugs were ~uenched from a temperature in tha range of 1400 - 1600F into water containing 8% by volume of Aqua-Quench 200 for the 1-1j8 and 1-1/2 inch slugs and 21, 24 and 27~ by volume of Aqua-Quench 200 for the 2, 2-~Z~3~3Q
1/2 and 3 inch slugs respectively. The slugs were removed from the quenching solutions at a temperature in the range of 100 - 300F and heat treated for 4 hours at 500F. The re-sulting hardness of the slugs was in excess of 600 Brinell and their microstructure consisted essentiall~ of martensite and carbide.
SUPPLEMENTARY DISCLOSURE
In carrying out the foregoing disclosed process it also has been found that other low alloy cast irons exhibit-ing the beneficial physical characteristics exhibited by the presently disclosed nickel low alloys, can be made by the same process steps.
The further group of alloying elements is referred to as a molybdenum/copper group, the range of elements for which are given below. In addition to the low alloys of the molybdenum/copper group of alloying elements, it also has been found that cer-tain physical characteristics of the re-sultant low alloy can be enhanced, and the required range of quantity of the alloying elements can be beneficially reduced by the presence of other alloying additives.
Thus, the use of nickel alloyed scrap material in the alloy melt, so as to introduce a small quantity of nickel, has the effect of improving the low alloy thus obtained by endowing the alloy with improved hardness, in the higher end of the hardness range, without undue impairment of the requisite toughness characteristics. At the same time, the required quantity of Molybdenum in the alloy is reduced.
~`
_g_ In similar fashion, the subject low alloys may contain small quantities of chromium with beneficial effect on the hard-ness, again moving it into the higher end oE the hardness range, while at the same time diminishing the re~uired quan-tity of at least one of the significant alloying elements.
A typical range of low alloy composition alloying components for the Molybdenum/copper group of alloys is given below in Table III.
. .
Table III - Typical Analysis Composition of Low Alloy Alloying Elements Slug Size Carbon Silicon Manganese Molybdenum Copper inches dia. % % % % %
1 1/8 3.6-3.90.5-0.7 0.5-0.70.2-0.5 0.5-0.7 1 1/2 3.3-3.60.5-0.7 0.5-1.00.2-0.5 0.5-0.7 2 3.1-3.4 0.5-0.7 0.5-1.00.5-0.7 0.5-0.7 2 1/2 3.1-3.40.5-0.7 0.5-1.00.5-0.7 0.6-0.8 The slugs were quenched from a temperature in the range 1400 - 1600F into water containing 4% by volume oE Aqua-Quench 200 (T.M.) for the 1 1/8 and 1 1/2 inch diameter slugs; and 15% and 18% by volume of Aqua-Quench 200 for the 2 and 2 1/2 inch diameter slugs, respectively. The slugs were removed from the quenching solutions at a temperature in the range 100 to 300F and heat treated for ~ hours at 500F.
The resulting slugs had a hardness in the range 600 to 675 Brinell; a Rockwell hardness of 60 (average), and density of 0.275 to 0.285 lb. per cubic inch. The microstructure was martensitic matrix with alloy carbides dispersed throughout.
: ~`' ' ' ' , ., ~ ,.
3 Z~3030 The procedure followed in a test program was the same as that disclosed above in relation to the low nickel alloys.
The relationship between alloy content, cooling rate and hardness of the heat treated slugs was substantially as follows in Table IV.
Table IV
Variation of Cooling Rate, Hardness with Slug Size and Alloy Content Slug Size Alloy Content Cooling Rate Average Hardness InchesWeight % Degrees FBrinell Dia.Molybdenum/ per second Copper _ _ _ _ _ 1 1/2 .20 / .8 19.6 630 .25 / .7 20.4 670 .30 / .6 27.5 685 2 1/2 .5 / .8 4.5 620 .55 / .7 3.5 640 .60 / .6 2.5 665 In addition to the foregoing product it was found that the addition of small percentages of nickel in the range 0.25 to 0.45 weight percent promotes slug hardness to the upper end of the range, while enabling the Molybdenum content to be reduced to the range 0.2 to 0.7 weight percent.
Although the invention has been disclosed with re-ference to preferred embodiments, it is to be understood that it is not limited to such embodiments but by the scope of the claims only.
.
PROCESS FOR PROD~CING A LOW ALLOY WHITE CAST IRON
AND PRODUCT RESULTING THEREFROM
This invention relates to a process for producing a low alloy white cast iron, and more particularly to the production of a low alloy white cast iron for use as grinding media in the form of balls or truncated cones known as "slugs" in the ore processing industry.
Mat~rials used in grinding media applications where wear resistance is required include alloy steels, both cast and forged, and alloy white cast irons in the as-cast and heat treated condition. Alloy white cast irons are divided into two groups, one containing approximately 8 to 30% chromium and the other 0 to 4% chromium. High chromium white cast irons necessitate a special heat treatment above the transformation temperature to allow them to reach their full potential. This heat treatment combined with their high alloy content renders them uneconomical for many ore grinding applications. The other group of white cast irons is generally more economical although an amount of certain alloying elements is required to yield optimum properties.
It is widely recognized that low alloy white cast irons with a microstructure consisting of carbide and martensite offer high wear resistance in most ore grinding applications. Carbide is present in all white cast irons;
martensite, on the other hand, is obtained through a combination of alloy content and processing conditions. If the conditions for martensite formation are not met, an 3(P3~) undesirabl~ pha~e known as pearllte will be produced upon cooli~ from the transfo~ation temperature. Many alloying elements have been used over the years to avoid the formation of pearllte~ These elements are used either alone or in the combined form, and they include nickel, chromium, molybdenum, copper, manyanese and vanadium.
Because o~ its outstanding wear r2sistance, a nickel-chromium white cast iron known as Ni-Har~ has been ~uccass~ully used ~or ovar Xorty years to make grlnding medla. The microstructur~ o~ Ni-Hard consist~ essentially o~ oarbide and martensite, and its hardnes~ i~ 600 Brinell in the chill cast and stress relieved condition.
Compositional ranges suggested for the manufacture of Ni~
Hard grinding ball~ and 51ug8 are about 3~ carbon, 0.5 ~ilicon, 0.5% manganes~, 1.5-4% nickel and 1.0-2 chromium, the re~t being iron.
A low alloy white cast iron having a hardness and a microstructure similar to those o~ Ni-Hard was disclo~ed in applicant's Canadian Patent No. 1,125,056. ~he alloying ~- 20 elaments were 2.5 to 4% carbon, 0.3 to 0.8% sillcon, 0.3 to 1.0~ manganesa and 1.7 to 3.5% nickel.
The procedure followed for producing the above alloy was as follow: Iron and the above alloying elements were melted in a suitable furnace and cast into moulds. The cast product was sha~en out o~ the moulds at a tempera~ure a~ove the transformation temperaturs and was either cooled with fine water ~prays or sub~ected to forced ai~ or still air cooling to cool it between approximat~ly 1~00F and *is a trademark ~l2~3(~3() ~ 3-400F at a minimum rate of 2.5F/sec. The above combination of alloy content and processing conditions produced an alloy with a microstructure consisting essentially of martensite and carbide with no pearlite.
However, the minimum amount of nickel needed in the above process to avoid the formation of pearlite was 1.7%.
In addition, the hardness of the cast product was not uniform throughout~
Although the above low alloy white cast iron was less lQ expensive than Ni-Hard because it aontained less nickel and no chromium, it was felt that more research was needed to further decrease the nickel content and thus, to develop a more cost-effective alloy for grinding media application. It was also desirable to develop a product having a more uniform hardness.
The process in accordance with the present invention comprises the steps of melting an alloy consisting essentially of about 2.5 to 4~ carbon, 0.3 to 0.8~
silicon, 0.3 to 0.8% manganes~, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except for incidental impurities commonly found in cast irons, casting such alloy into moulds, removing the cast product from the moulds while its surface temperature is above the transformation temperature of the particular alloy white cast iron and cooling it by quenching into a liguid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
; `
. .
~3n30 The above alloy combination and processing conditions produces a microstructure consisting essentially of martensite and carbide with a uniform hardness in excess of 600 Brinell.
The cast product is then subjected to a heat treatment of 4 to 8 hours at 400-600F to transform any retained austenite into martensite and to relieve casting stresses.
In the making of grinding media such as slugs, the size of slugs varies generally but is preferably in the range lQ o~ approximately 1 to 3 in. Alloy content, particularly nickel, and cooling rates are adjusted as a ~unction of slug size: Low alloy content and high cooling rates being used with small slugs and high alloy content and low cooling rates with large slugs. Best results are obtained 5 with the following combinations:
For 1-1/2 in. and smaller slugs: 0.75 to 1.5~
nickel and 0 to 0.5% chromium and cooling rates in the range of 7.5 - 25F per second.
For 2, 2-1/2 and 3 in. slugs: 1.25 to 2% nickel and 0.25 to 0.75% chromium and cooling rates in the range of 2.5 - 7.5'F per second.
The volume of polymer used in the cooling medium is in the range of 5 - 30% and is adjusted so as to provide a controlled rate of cooling which, for a given slug size and alloy content, will prevent the formation o~ pearlite and, at the same time will not generate cracks in the ~inal product. For best results, th2 temperature of the liquid medium is kept in the range of 90 - 130~F.
:~2~33~330 , Before arriving at the preferred embodiment a test program on alloys containing 0.5 ko 3.0% nickel and 0 to 2% chromium was carried out on a pilot scale. Each alloy was based on a cast iron mixture containing approximately 3% carbon, 0.6% silicon and 0.6% manganese, the remainder being iron. Other variables investigated in the test program were the concentration in the range o~ 2.5 - 30%
by volume of the organic polymer and the temperature, in the range of 1200 - 1800F, Erom which the grinding slugs are quenched into the liquid medium.
An example of the procedure followed in the test program will now be disclosed. Metal charges consisting of pig iron, steel scrap, ferro-manganese, ~erro-silicon, nickel and ferro-chrome were melted in a coreless ; 15 induction furnace and poured into cast iron moulds containing either 1-1/2 or 2-1/2 inch slug cavities. The slugs were shaken out of the moulds at 1500F and were quenched immediately into water containing 2.5 - 10% and 10 - 30~ Aqua-Quench* for the 1-1/2 and 2-1/2 in. slugs respectively. The corresponding cooling rates were sstablished using thermocouples inserted into the slug cavities while the metal was still molten and connected to a recording instrument. The as-cast slugs were then subjected to a heat treatment o~ 4 hours at 500F. None o~
the slugs were cracked and their microstructure consisted essentially of martensite and carbide. Table 1 shows the relationship between alloy content, cooling rate and hardness for the heat treated slugs.
*Trade Mark 12~13(~30 -6~
EFFECT OF ALLOY CONTENT AND COOLING RATE
ON THE HARDNESS OF 1-1/2 AND 2-1/2 IN.
GRINDING SLUGS
, Slug~lloy ContentCooling A~erage Sizeweight % Rate Brinell in. Ni Cr F/s Hardness 0.75 0.5 19.3 635 1.0 0.5 19.3 615 `:
~ 1/21.5 0 g.6 635 :
: ~ 1.5 0.25 20.8 680 ! ~ :
; 1.5 0.57.5 690 1.5 0.54.7 615 2-1/2 1.50.75 3.7 650 , . 2.0 0.5 2.4 660 - --- ... _ __ Full scala foundry tests have shown that the new white aast iron of the present invention may be melted and cast using standard foundry practice and casting methods. The ~ ., lZ1~3~30 _7 melting equipment used so far in these full scale tests has been a channel-type induction furnace. However, other melting equipment such as cupolas or various types of electric furnaces could also be used. Tests to date were run on 1-1/8, 1-1/2, 2, 2-1/2 and 3 inch grinding slugs cast in permanent moulds. The composition of the slugs ls given in Table II.
TABLE II
COMPOSITION IN WEIGHT PERCENT OF
GRINDING SLUGS PRODUCED DURING
FULL SCALE FOIJNDRY ~ESTS
.. .. _ Slug Carbon Silicon Manganese Nickel Chromium Size in.
~ 1-1/8 3.6 0.55 0.6 0.9 0.4 ; 1-1/2 3.4 0.55 0.6 0.9 0.4 2 3.2 0.55 0.6 1.4 0.4 - 2-1/2 3.2 0.55 0.6 1.7 0.4 3 3.2 0.55 0.6 1.9 0.4 _ . _ . __ . .
The slugs were ~uenched from a temperature in tha range of 1400 - 1600F into water containing 8% by volume of Aqua-Quench 200 for the 1-1j8 and 1-1/2 inch slugs and 21, 24 and 27~ by volume of Aqua-Quench 200 for the 2, 2-~Z~3~3Q
1/2 and 3 inch slugs respectively. The slugs were removed from the quenching solutions at a temperature in the range of 100 - 300F and heat treated for 4 hours at 500F. The re-sulting hardness of the slugs was in excess of 600 Brinell and their microstructure consisted essentiall~ of martensite and carbide.
SUPPLEMENTARY DISCLOSURE
In carrying out the foregoing disclosed process it also has been found that other low alloy cast irons exhibit-ing the beneficial physical characteristics exhibited by the presently disclosed nickel low alloys, can be made by the same process steps.
The further group of alloying elements is referred to as a molybdenum/copper group, the range of elements for which are given below. In addition to the low alloys of the molybdenum/copper group of alloying elements, it also has been found that cer-tain physical characteristics of the re-sultant low alloy can be enhanced, and the required range of quantity of the alloying elements can be beneficially reduced by the presence of other alloying additives.
Thus, the use of nickel alloyed scrap material in the alloy melt, so as to introduce a small quantity of nickel, has the effect of improving the low alloy thus obtained by endowing the alloy with improved hardness, in the higher end of the hardness range, without undue impairment of the requisite toughness characteristics. At the same time, the required quantity of Molybdenum in the alloy is reduced.
~`
_g_ In similar fashion, the subject low alloys may contain small quantities of chromium with beneficial effect on the hard-ness, again moving it into the higher end oE the hardness range, while at the same time diminishing the re~uired quan-tity of at least one of the significant alloying elements.
A typical range of low alloy composition alloying components for the Molybdenum/copper group of alloys is given below in Table III.
. .
Table III - Typical Analysis Composition of Low Alloy Alloying Elements Slug Size Carbon Silicon Manganese Molybdenum Copper inches dia. % % % % %
1 1/8 3.6-3.90.5-0.7 0.5-0.70.2-0.5 0.5-0.7 1 1/2 3.3-3.60.5-0.7 0.5-1.00.2-0.5 0.5-0.7 2 3.1-3.4 0.5-0.7 0.5-1.00.5-0.7 0.5-0.7 2 1/2 3.1-3.40.5-0.7 0.5-1.00.5-0.7 0.6-0.8 The slugs were quenched from a temperature in the range 1400 - 1600F into water containing 4% by volume oE Aqua-Quench 200 (T.M.) for the 1 1/8 and 1 1/2 inch diameter slugs; and 15% and 18% by volume of Aqua-Quench 200 for the 2 and 2 1/2 inch diameter slugs, respectively. The slugs were removed from the quenching solutions at a temperature in the range 100 to 300F and heat treated for ~ hours at 500F.
The resulting slugs had a hardness in the range 600 to 675 Brinell; a Rockwell hardness of 60 (average), and density of 0.275 to 0.285 lb. per cubic inch. The microstructure was martensitic matrix with alloy carbides dispersed throughout.
: ~`' ' ' ' , ., ~ ,.
3 Z~3030 The procedure followed in a test program was the same as that disclosed above in relation to the low nickel alloys.
The relationship between alloy content, cooling rate and hardness of the heat treated slugs was substantially as follows in Table IV.
Table IV
Variation of Cooling Rate, Hardness with Slug Size and Alloy Content Slug Size Alloy Content Cooling Rate Average Hardness InchesWeight % Degrees FBrinell Dia.Molybdenum/ per second Copper _ _ _ _ _ 1 1/2 .20 / .8 19.6 630 .25 / .7 20.4 670 .30 / .6 27.5 685 2 1/2 .5 / .8 4.5 620 .55 / .7 3.5 640 .60 / .6 2.5 665 In addition to the foregoing product it was found that the addition of small percentages of nickel in the range 0.25 to 0.45 weight percent promotes slug hardness to the upper end of the range, while enabling the Molybdenum content to be reduced to the range 0.2 to 0.7 weight percent.
Although the invention has been disclosed with re-ference to preferred embodiments, it is to be understood that it is not limited to such embodiments but by the scope of the claims only.
.
Claims (23)
1. A process for producing a low alloy white cast iron comprising:
a) melting an alloy consisting essentially of about 2.5 to 4.0% carbon, 0.3 to 0.8% silicon, 0.3 to 0.8 manganese, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except: for incidental impurities commonly found in cast irons;
b) casting said alloy into moulds to produce the desired product;
c) removing the product from the moulds while its surface temperature is above the transformation temperature of the alloy, and d) cooling it by quenching into a liquid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
a) melting an alloy consisting essentially of about 2.5 to 4.0% carbon, 0.3 to 0.8% silicon, 0.3 to 0.8 manganese, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except: for incidental impurities commonly found in cast irons;
b) casting said alloy into moulds to produce the desired product;
c) removing the product from the moulds while its surface temperature is above the transformation temperature of the alloy, and d) cooling it by quenching into a liquid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
2. A process as defined in claim 1, further comprising the step of heat treating the product at a temperature of 400-600°F for a time period of 4 to hours.
3. A process as defined in claim 2, wherein the product is heat treated at a temperature of about 500°F
for about 4 hours.
for about 4 hours.
4. A process as defined in claim 1, wherein the products are grinding slugs in the size of 1 to 3 in, and wherein the cooling rate is in the range of 2.5 to 25°F/sec.
5. A process as defined in claim 4, wherein the nickel content and cooling rates are adjusted as a function of slug size, low nickel alloy content and high cooling rates being used with small slugs, and high nickel alloy content and low cooling rates with large slugs.
6. A process as defined in claim 4, wherein the volume of polymer used in the. liquid medium is in the range of 5 to 30% and increases with slug size.
7. A process a defined in claim 4, wherein the temperature of the liquid medium is kept in the range of 90 to 130°F.
8. A low alloy white cast iron consisting essentially in weight percent of about 2.5 to 4% carbon, 0.3 to 0.8%
silicon, 0.3 to 0.8% manganese, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except for incidental impurities commonly Pound in cast irons, said alloy being quenched in a liquid medium containing water and an organic polymer to form a microstructure consisting essentially of martensite and carbide and a uniform hardness in excess of 600 Brinell.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
silicon, 0.3 to 0.8% manganese, 0.75 to 2.0% nickel and 0 to 0.75% chromium, the balance being iron except for incidental impurities commonly Pound in cast irons, said alloy being quenched in a liquid medium containing water and an organic polymer to form a microstructure consisting essentially of martensite and carbide and a uniform hardness in excess of 600 Brinell.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
9. A process for producing a low alloy white cast iron comprising a molybdenum/copper alloy, the process compris-ing:
a) melting an alloy consisting essentially of about 3.1 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% mangan-ese: 0.2 to 0.7% molybdenum; 0.5 to 0.8% Copper, the balance being iron except for incidental impurities commonly found in cast iron;
b) casting said alloy into molds to produce the desired product;
c) removing the desired product from the molds while its surface temperature is above the transformation temperature of the alloy; and d) cooling it by quenching into a liquid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
a) melting an alloy consisting essentially of about 3.1 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% mangan-ese: 0.2 to 0.7% molybdenum; 0.5 to 0.8% Copper, the balance being iron except for incidental impurities commonly found in cast iron;
b) casting said alloy into molds to produce the desired product;
c) removing the desired product from the molds while its surface temperature is above the transformation temperature of the alloy; and d) cooling it by quenching into a liquid medium containing water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
10. The process as defined in claim 9, wherein said alloy consists essentially of about 3.1 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% manganese; 0.2 to 0.7% molyb-denum; 0.5 to 0.7% copper, -the balance being iron except for incidental impurities commonly found in cast irons.
11. The process as defined in claim 9 wherein said alloy consists essentially of about 3.6 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 0.7% manganese; 0.2 to 0.5% molyb-denum; 0.5 to 0.7% copper, the balance being iron except for incidental impunities commonly found in cast irons.
12. The process as defined in claim 9, wherein said alloy consists essentially of about 3.3 to 3.6% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% manganese; 0.2 to 0.5% molyb-denum; 0.5 to 0.7% copper, the balance being iron except for incidental impurities commonly found in cast irons.
13. The process as defined in claim 9, wherein said alloy consists essentially of about 3.1 to 3.4% carbon; 0.5 to 0.7 silicon; 0.5 to 1.0 manganese; 0.5 to 0.7% molybden-um; 0.5 to 0.7% copper, the balance being iron except for incidental impurities commonly found in cast irons.
14. The process as defined in claim 9 wherein said al-loy consists essentially of about 3.1 to 3.4% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% manganese; 0.5 to 0.7%.molybdenum;
0.6 to 0.8% copper; the balance being iron except for inci-dental impurities commonly found in cast irons.
0.6 to 0.8% copper; the balance being iron except for inci-dental impurities commonly found in cast irons.
15. The process as defined in claim 9 wherein said pro-duct comprises slugs in the size range 1 1/8 inch to 2 1/2 inch diameter.
16. The process as defined in claim 10, wherein said product comprises slugs of substantially about 2 inch diameter, or greater.
17. The process as defined in claim 11 wherein said product comprises slugs of substantially about 1 1/8 inch diameter.
18. The process as defined in claim 12 wherein said product comprises slugs of substantially about 2 inch dia-meter.
19. The process as defined in claim 13 wherein said product comprises slugs of substantially about 2 1/2 inch diameter.
20. The process as set forth in claim 9, said product comprising slugs in the size range 1 1/8 inch to 1 1/2 inch diameter, said slugs being quenched from a temperature in the range 1400 to 1600 °F into water containing 9% by volume of organic polymer.
21. The process as set forth in claim 9, said product comprising 2 inch diameter slugs, being quenched from a tem-perature in the range 1400 to 1600 °F into water containing 14% by volume of organic polymer.
22. The process as set forth in claim 9, said product comprising 2 1/2 inch diameter slugs, said slugs being quenched from a temperature in the range 1400 to 1600 °F into water containing 17 % by volume of organic polymer.
23. The process for producing a low alloy white cast iron comprising a molybdenum/copper alloy, the process com-prising:
a) melting an alloy consisting essentially of about 3.1 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% mangan-ese; 0.2 to 0.7% molybdenum; 0.25 to 0.45% nickel; 0.3 to 0.3% copper, the balance being iron except for impurities commonly found in cast irons;
b) casting said alloy into molds to produce the desired product;
c) removing the desired product from the molds while its surface temperature is above the traus Brustin tem-perature of the alloy; and d) cooling it by quenching into liquid medium con-taining water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
a) melting an alloy consisting essentially of about 3.1 to 3.9% carbon; 0.5 to 0.7% silicon; 0.5 to 1.0% mangan-ese; 0.2 to 0.7% molybdenum; 0.25 to 0.45% nickel; 0.3 to 0.3% copper, the balance being iron except for impurities commonly found in cast irons;
b) casting said alloy into molds to produce the desired product;
c) removing the desired product from the molds while its surface temperature is above the traus Brustin tem-perature of the alloy; and d) cooling it by quenching into liquid medium con-taining water and an organic polymer at a sufficiently high rate to prevent the formation of pearlite but not so high as to generate cracks in the product.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000511175A CA1283030C (en) | 1986-06-09 | 1986-06-09 | Process for producing a low alloy white cast iron and product resulting therefrom |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000511175A CA1283030C (en) | 1986-06-09 | 1986-06-09 | Process for producing a low alloy white cast iron and product resulting therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1283030C true CA1283030C (en) | 1991-04-16 |
Family
ID=4133316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000511175A Expired - Lifetime CA1283030C (en) | 1986-06-09 | 1986-06-09 | Process for producing a low alloy white cast iron and product resulting therefrom |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1283030C (en) |
-
1986
- 1986-06-09 CA CA000511175A patent/CA1283030C/en not_active Expired - Lifetime
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