CA1311993C - Gray cast iron having both increased wear resistance and toughness - Google Patents
Gray cast iron having both increased wear resistance and toughnessInfo
- Publication number
- CA1311993C CA1311993C CA000553034A CA553034A CA1311993C CA 1311993 C CA1311993 C CA 1311993C CA 000553034 A CA000553034 A CA 000553034A CA 553034 A CA553034 A CA 553034A CA 1311993 C CA1311993 C CA 1311993C
- Authority
- CA
- Canada
- Prior art keywords
- solid
- austenite
- matrix
- iron
- wear resistance
- 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
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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
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)
- Heat Treatment Of Articles (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
Abstract of the Disclosure A method is disclosed for making gray iron having both increased wear resistance and impact toughness, comprising: (a) solidifying a hypoeutectic gray iron melt (i) to which has been added a carbide forming agent in an amount of .3-.8% by weight, selected from the group consisting of Ti, V and Mo, and, advantageously, a high carbon austenite-ferrite forming agent in an amount of .5-3.0%, by weight, selected from the group consisting of nickel and copper, and at a solidification rate to form a matrix with a mixture of flake graphite and eutectic carbide suspended in the matrix; and (b) heat treating the solid by (i) heating to a temperature and for a period of time to fully austenitize the solid (ii) quenching the solid to a temperature level and for a period of time to decompose austenite to form and high carbon austenite and ferrite matrix and (iii) air cooling the solid to room temperature.
The hypoeutectic gray iron contains less than 4.35% carbon equivalent and preferably comprises, by weight, 2.5-3.0% carbon, 2.0-2.5% silicon, .5-.90%
manganese, and the remainder iron.
The hypoeutectic gray iron contains less than 4.35% carbon equivalent and preferably comprises, by weight, 2.5-3.0% carbon, 2.0-2.5% silicon, .5-.90%
manganese, and the remainder iron.
Description
GRAY CAST IRON HAVING BOTH INCREASED
WEAR RESISTANCE AND TOUGHNESS
The invention relates to the art of making gray cast iron and, more particularly, to the technology involving chemistry variations and heat treating variables for improving the characteristics of wear resistance and toughness.
Gray cast iron is the least expensive of all the cast metals. This is due to the type of raw materials used: pig iron, cast iron scrap, steel scrap, limestone, coke and air, all of which are relatively inexpensive. Most gray cast iron used commercially is used primarily in the as-cast condition. There has been some attention to heat treatment and low alloying for lS gray cast irons through the years.
The general consensus of foundry operators in this country indicates that the composition of gray cast iron should be about (using weight percentages here and throughout the description): 2.0-4.0 carbon: 1.25-3.25 silicon: .75-1.25 manganese: .08-.12 sulfur: and .07-.20 phosphorus.
In the field of abrasive wear, gray cast iron is usually used where the required impact toughness in service is not severe. Such cast iron is resistant to abra~ive wear because of the presence of a high amount of carbides in the matrix of the cast iron. Most gray ca~t irons will contain at least 10% by weight primary complex ' , ',:
~-~7~
: , ~ , ., , , .
~.'. . -.
. ~ : , , , ~31~93 iron carbides. Unfortunately, however, these carbides are normally massive and impart a degree of brittleness to the cast iron which considerably limits its usefulness with reference to impact strength. While relegating gray cast iron to applications without the need for high impact strength, the main developmental effort has been to improve machining.
One attempt to provide greater machinability while retaining excellent wear resistance and fatigue resistance of gray cast irons involves heat treating the as-cast iron to reduce hardness while retaining the carbidic microstructure (see U.S. patent 4,230,506). In this patent, the cast metal was alloyed with a combination of carbide forming agents such as chromium, nickel, copper, molybdenum, and vanadium. They were used in combination to provide a composite total in an amount of 2.25-3.85%; this is a considerable amount of carbide forming agent. The improvement in machinability was achieved by heat treating to an austenitizing temperature, slowly cooling over a period of l-l/2 hours to a temperature level of 400F, and then air cooling.
Slow cooling promoted the production of pearlite and reduced the hardness of such cast iron, making it more readily machinable. After machining, the iron was quenched to transform any retained austenite to martensite.
The problem with the 4,230,506 patent is that ~ear resistance is retained or improved at the sacrifice of toughness and strength characteristics, making it unsuitable for applications that require a high level for both of these characteristics.
Similarly~ in U.S. patent 3,384,515, the - solution to the problem of machinability was to control heat treating to permit the promotion of complex iron carbides while providing for incipient spheroidization of ~' :; .
. .
~.. , ,, , -, . , ~ , ~
.~, , . ~ .
-` 13~1~93 pearlite, thereby avoiding martensite and reducing the hardness of the material. The same problem with respect to lack of enhancement of toughness and strength characteristics in such a carbidic cast iron remains.
In U.S. patent 2,885,284, an attempt was made to provide for an increase in both the abrasive wear as well as the impact properties of the gray cast iron.
The contribution of this patent is to incorporate high amounts of alloying ingredients in the form of aluminum and manganese to promote contrary characteristics.
Aluminum is added in amounts greater than 1% to promote graphitization and manganese is added in amounts greater than 1.5% to promote carbide stabilization. There is no attempt to modify or introduce any unusual heat treating parameters: there is simp}y a reliance upon conventional processing and heat treating steps. The disalosure admits, in column 2, lines 27-33, that the amount of aluminum or manganese that is incorporated will depend upon which characteristic is desired in the final product, namely, to increase toughness the carbon must ~ be predominantly in the form graphite promoted by the ;j~ u~e o~ aluminum, and to provide for increased hardness I the ¢arbon must be predominantly in the form of Carbides~ which is promoted by the incorporation of mangan-~e. This disclosure i8 an "either/or" teaching in that the there is no suggestion that both of such ; ¢haracteristi¢s can be achieved at a high level at the same time.
This invention is dlrected towards the provi~ion of~a gray oa~t~iron having both increased wear r ~i~tan¢e and toughness which can be achieved by modlfi¢ation both in the chémistry and the heat treating te¢hnigue~ for gray cast lron, and which additionally ha~ hlgh ten~ile strength, hlgh damplng capaclty, high heat oonductivity, and more ductility than conventional ca~t irons.
, ", , " ~ i~
: .
:: - ~ ' .. : .
--` 1311993 The above advantagea have been achieved by development of chemistry and process controls which disperse a predetermined mixture of eutectic aarbide particles and flake graphite throughout a matrix of high carbon austenite and ferrite In accordanee with one aspect of the present invention, there is provided a method of making a more wear resistant gray cast iron which has high wear resistance and impact strength, comprising (a) solidi-fying a hypoeutectic gray iron melt to whieh has beenadded (i) a carbide forming agent in an amount of 0 3 to 0 8% by weight, selected from the group consisting of Ti, V, Cr and Mo and, (ii) a high carbon austenite-ferrite forming agent in an amount of 0 5 to 3 0% by weight, selected from the group consisting of nickel and copper, the solidification being at a rate to~form a ~'! matrix with a mixture of flake graphite and eutectic earbide suspended in the matrix and (b) heat treating the ~olid by ~i) heating to a temperature and for a period of time to fully austenitize the solid and (ii) qu nehing the solid to a predetermined temperature lev 1 and holding at that level for a period of time to deeompo~- au~tenit- to form a high earbon austenite and ferrit- matrix, earrying in suspension at a mixture of 40 to 60% flake graphite and the remainder eutectic earbide partieles and (iii) air cooling the solid to room temperature - ~ ~ The hypoeutQctic gray iron eontains less than 4 35% earbon eguival-nt and pr-ferably eomprises, by ~weight, 2 5 to 3 0% earbon, 2 0 to 2 5% silicon, 0 5 to 0 90% mangane~e, and the remainder iron Pre~erably, the heat treating eomprise~
heating to a t-mperature level of 1560 to 1590 F for a period~of time o~ 1 5 to 2 5 hours; and the quenching 35~ step eQmprises guenehing to a temperature level of 450 to 800 F ~or a period of time of 1 5 to 2 5 hours The , ~ . : ; ' ' :
' ' '' ':, , :, : ' ~'' :''~ ~ " ' ' -- 1311~93 rate at which such quenching i6 carried out is preferably in the range of 300 to 375-F per minute.
The resultant cast iron will comprise a micro-structure having the suspended mixture comprised of 40 to 60% flake graphite and the remainder of the mixture eutectic carbide. Such mixture is controlled by the selection of the solidification rate and by the selec-tion of chemistry for the gray cast iron melt. The casting will preferably have a tensile strength of 45 to 55 ksi, an impact strength of 30 to 35 ft/lb, and pre-ferably an elongation of about 2%. Such product consti-tutes a further aspect of the invention. The wear resistance of such casting is 2 to 3 times greater than conventional gray cast irons and when measured by a standard sleeve test is 0.0028 to 0.0019 inch per 1000 hours. The casting also is characterized by resistance to scuffing whereby the ratio of horsepower to produce scuffing divided by the normal horsepower is greater than 1.5. These wear resistance parameters are achieved through attainment of a type A graphite flake in the casting.
In the description which follows, reference is made to the accompanying drawing, wherein:
Figure 1 i8 a photo-micrograph of the structure of the casting produced by the method of this invention, the microstructure being shown at an enlargement of 500X. Areas of flake graphite, eutectic carbide, and austenite ferrite are indicated.
The preferred method for making a gray cast iron having both increased wear resistance and impact toughness comprises: (a) solidifying a hypoeutectic gray iron melt (i) to which has been added a carbide forming first agent in an amount of 0.3 to 0.8% by weight, selected from the group consisting of titanium, vanadium, chromium, and molybdenum, and a second agent ,~ :
-. .
:
---`` 131~3 5a to facilitate the formation of high carbon austenite-ferrite, said second a~ent being present in an B~
1 3 ~ 3 amount of .5-3.0% by weight, selected from the group consisting of nickel and copper and (ii) at a solidification rate to form a matrix with a mixture of flake graphite and eutectic carbide suspended in the matrix; and (b) heat treating the solid by (i) heating to a temperature and for a predetermined period of time to fully austenitize the solid (ii) quenching the solid to a temperature level and for a period of time to decompose austenite to form a high carbon austenite-ferrite matrix and (iii) air cooling the solid.
.
Chemistrv A conventional wear resis~ant gray iron usually contains 3.0-4.0% carbon, 1.5-3.0% silicon, and .5-.9 manganese. This method lowers the carbon content and adds both a carbide forming agent and an agent to facilitate the formation of high carbon austenite-ferrite during heat treatment. The carbide forming agent is made in addition to the normal carbide forming tcndencies of manganese which is a normal part of gray cast iron.
Aluminum is specifically absent from the prqsent chemistry because it i8 a graphitizer which works against carbide formation and encourages pin hole defects. The -~ addition of a graphitizing agent is conspicuously absent from the present invention because graphitization can be controlled through process parameters with a given lower amount of carbon.
- Specifically, the chemistry comprises, preferably, 2.5-3.0% by weight carbon (a hypoeutectic iron-carbon alloy would comprise less than 35% carbon equivalent). If the carbon content were to be below ,, , ~
WEAR RESISTANCE AND TOUGHNESS
The invention relates to the art of making gray cast iron and, more particularly, to the technology involving chemistry variations and heat treating variables for improving the characteristics of wear resistance and toughness.
Gray cast iron is the least expensive of all the cast metals. This is due to the type of raw materials used: pig iron, cast iron scrap, steel scrap, limestone, coke and air, all of which are relatively inexpensive. Most gray cast iron used commercially is used primarily in the as-cast condition. There has been some attention to heat treatment and low alloying for lS gray cast irons through the years.
The general consensus of foundry operators in this country indicates that the composition of gray cast iron should be about (using weight percentages here and throughout the description): 2.0-4.0 carbon: 1.25-3.25 silicon: .75-1.25 manganese: .08-.12 sulfur: and .07-.20 phosphorus.
In the field of abrasive wear, gray cast iron is usually used where the required impact toughness in service is not severe. Such cast iron is resistant to abra~ive wear because of the presence of a high amount of carbides in the matrix of the cast iron. Most gray ca~t irons will contain at least 10% by weight primary complex ' , ',:
~-~7~
: , ~ , ., , , .
~.'. . -.
. ~ : , , , ~31~93 iron carbides. Unfortunately, however, these carbides are normally massive and impart a degree of brittleness to the cast iron which considerably limits its usefulness with reference to impact strength. While relegating gray cast iron to applications without the need for high impact strength, the main developmental effort has been to improve machining.
One attempt to provide greater machinability while retaining excellent wear resistance and fatigue resistance of gray cast irons involves heat treating the as-cast iron to reduce hardness while retaining the carbidic microstructure (see U.S. patent 4,230,506). In this patent, the cast metal was alloyed with a combination of carbide forming agents such as chromium, nickel, copper, molybdenum, and vanadium. They were used in combination to provide a composite total in an amount of 2.25-3.85%; this is a considerable amount of carbide forming agent. The improvement in machinability was achieved by heat treating to an austenitizing temperature, slowly cooling over a period of l-l/2 hours to a temperature level of 400F, and then air cooling.
Slow cooling promoted the production of pearlite and reduced the hardness of such cast iron, making it more readily machinable. After machining, the iron was quenched to transform any retained austenite to martensite.
The problem with the 4,230,506 patent is that ~ear resistance is retained or improved at the sacrifice of toughness and strength characteristics, making it unsuitable for applications that require a high level for both of these characteristics.
Similarly~ in U.S. patent 3,384,515, the - solution to the problem of machinability was to control heat treating to permit the promotion of complex iron carbides while providing for incipient spheroidization of ~' :; .
. .
~.. , ,, , -, . , ~ , ~
.~, , . ~ .
-` 13~1~93 pearlite, thereby avoiding martensite and reducing the hardness of the material. The same problem with respect to lack of enhancement of toughness and strength characteristics in such a carbidic cast iron remains.
In U.S. patent 2,885,284, an attempt was made to provide for an increase in both the abrasive wear as well as the impact properties of the gray cast iron.
The contribution of this patent is to incorporate high amounts of alloying ingredients in the form of aluminum and manganese to promote contrary characteristics.
Aluminum is added in amounts greater than 1% to promote graphitization and manganese is added in amounts greater than 1.5% to promote carbide stabilization. There is no attempt to modify or introduce any unusual heat treating parameters: there is simp}y a reliance upon conventional processing and heat treating steps. The disalosure admits, in column 2, lines 27-33, that the amount of aluminum or manganese that is incorporated will depend upon which characteristic is desired in the final product, namely, to increase toughness the carbon must ~ be predominantly in the form graphite promoted by the ;j~ u~e o~ aluminum, and to provide for increased hardness I the ¢arbon must be predominantly in the form of Carbides~ which is promoted by the incorporation of mangan-~e. This disclosure i8 an "either/or" teaching in that the there is no suggestion that both of such ; ¢haracteristi¢s can be achieved at a high level at the same time.
This invention is dlrected towards the provi~ion of~a gray oa~t~iron having both increased wear r ~i~tan¢e and toughness which can be achieved by modlfi¢ation both in the chémistry and the heat treating te¢hnigue~ for gray cast lron, and which additionally ha~ hlgh ten~ile strength, hlgh damplng capaclty, high heat oonductivity, and more ductility than conventional ca~t irons.
, ", , " ~ i~
: .
:: - ~ ' .. : .
--` 1311993 The above advantagea have been achieved by development of chemistry and process controls which disperse a predetermined mixture of eutectic aarbide particles and flake graphite throughout a matrix of high carbon austenite and ferrite In accordanee with one aspect of the present invention, there is provided a method of making a more wear resistant gray cast iron which has high wear resistance and impact strength, comprising (a) solidi-fying a hypoeutectic gray iron melt to whieh has beenadded (i) a carbide forming agent in an amount of 0 3 to 0 8% by weight, selected from the group consisting of Ti, V, Cr and Mo and, (ii) a high carbon austenite-ferrite forming agent in an amount of 0 5 to 3 0% by weight, selected from the group consisting of nickel and copper, the solidification being at a rate to~form a ~'! matrix with a mixture of flake graphite and eutectic earbide suspended in the matrix and (b) heat treating the ~olid by ~i) heating to a temperature and for a period of time to fully austenitize the solid and (ii) qu nehing the solid to a predetermined temperature lev 1 and holding at that level for a period of time to deeompo~- au~tenit- to form a high earbon austenite and ferrit- matrix, earrying in suspension at a mixture of 40 to 60% flake graphite and the remainder eutectic earbide partieles and (iii) air cooling the solid to room temperature - ~ ~ The hypoeutQctic gray iron eontains less than 4 35% earbon eguival-nt and pr-ferably eomprises, by ~weight, 2 5 to 3 0% earbon, 2 0 to 2 5% silicon, 0 5 to 0 90% mangane~e, and the remainder iron Pre~erably, the heat treating eomprise~
heating to a t-mperature level of 1560 to 1590 F for a period~of time o~ 1 5 to 2 5 hours; and the quenching 35~ step eQmprises guenehing to a temperature level of 450 to 800 F ~or a period of time of 1 5 to 2 5 hours The , ~ . : ; ' ' :
' ' '' ':, , :, : ' ~'' :''~ ~ " ' ' -- 1311~93 rate at which such quenching i6 carried out is preferably in the range of 300 to 375-F per minute.
The resultant cast iron will comprise a micro-structure having the suspended mixture comprised of 40 to 60% flake graphite and the remainder of the mixture eutectic carbide. Such mixture is controlled by the selection of the solidification rate and by the selec-tion of chemistry for the gray cast iron melt. The casting will preferably have a tensile strength of 45 to 55 ksi, an impact strength of 30 to 35 ft/lb, and pre-ferably an elongation of about 2%. Such product consti-tutes a further aspect of the invention. The wear resistance of such casting is 2 to 3 times greater than conventional gray cast irons and when measured by a standard sleeve test is 0.0028 to 0.0019 inch per 1000 hours. The casting also is characterized by resistance to scuffing whereby the ratio of horsepower to produce scuffing divided by the normal horsepower is greater than 1.5. These wear resistance parameters are achieved through attainment of a type A graphite flake in the casting.
In the description which follows, reference is made to the accompanying drawing, wherein:
Figure 1 i8 a photo-micrograph of the structure of the casting produced by the method of this invention, the microstructure being shown at an enlargement of 500X. Areas of flake graphite, eutectic carbide, and austenite ferrite are indicated.
The preferred method for making a gray cast iron having both increased wear resistance and impact toughness comprises: (a) solidifying a hypoeutectic gray iron melt (i) to which has been added a carbide forming first agent in an amount of 0.3 to 0.8% by weight, selected from the group consisting of titanium, vanadium, chromium, and molybdenum, and a second agent ,~ :
-. .
:
---`` 131~3 5a to facilitate the formation of high carbon austenite-ferrite, said second a~ent being present in an B~
1 3 ~ 3 amount of .5-3.0% by weight, selected from the group consisting of nickel and copper and (ii) at a solidification rate to form a matrix with a mixture of flake graphite and eutectic carbide suspended in the matrix; and (b) heat treating the solid by (i) heating to a temperature and for a predetermined period of time to fully austenitize the solid (ii) quenching the solid to a temperature level and for a period of time to decompose austenite to form a high carbon austenite-ferrite matrix and (iii) air cooling the solid.
.
Chemistrv A conventional wear resis~ant gray iron usually contains 3.0-4.0% carbon, 1.5-3.0% silicon, and .5-.9 manganese. This method lowers the carbon content and adds both a carbide forming agent and an agent to facilitate the formation of high carbon austenite-ferrite during heat treatment. The carbide forming agent is made in addition to the normal carbide forming tcndencies of manganese which is a normal part of gray cast iron.
Aluminum is specifically absent from the prqsent chemistry because it i8 a graphitizer which works against carbide formation and encourages pin hole defects. The -~ addition of a graphitizing agent is conspicuously absent from the present invention because graphitization can be controlled through process parameters with a given lower amount of carbon.
- Specifically, the chemistry comprises, preferably, 2.5-3.0% by weight carbon (a hypoeutectic iron-carbon alloy would comprise less than 35% carbon equivalent). If the carbon content were to be below ,, , ~
2.5~, it would be difficult to provide the desired amount of carbide/graphite ratio (40:60 to 60:40) that is necessary for~the~wear resistance of this invention. If thc carbon~c~ontcnt werc in excess of 3%, processing ~: : ' ' ' ' ' ' ' ~, - -. , -~ 3 ~ 3 parameters would tend to form an excessive amount ofgraphite. It is desirable for the starting melt for this invention that it have a carbon equivalent in the range of 3.2-4.35 because below 3.2 too much carbide is formed, and above 4.35 too much graphite is formed, making it difficult to control the graphite/carbide ratio. Silicon is present in an amount of 2.0-2.5% and manganese remains at .5-.9%. If the silicon and manganese contents were to be below the designated amounts of 2.0 and .5%, respectively, there would be insufficient volumes of graphite or carbide formation; if the upper limit of manganese was exceeded, Mn segregation will occur and a nonuniform matrix structure will result. If the upper limit of silicon is exceeded, excessive carbide and/or graphite formation will occur.
The additional carbide forming agent, which is added to the gray iron melt herein, comprises molybdenum, titanium, chromium, or vanadium. Any one or all of these ingredients may be added as long as they are present in the alloy melt in an amount in the range of .3-.8% as combined. If less than .3% is employed, the carbide volume will be too low; if greater than .8% is employed, then too much carbide will be present.
In order to promote the decomposition of austenite into high carbon austenite and ferrite, without the formation of pearlite or martensite, during the heat treatment and cooling sequence, it is desirable to add either nickel and/or copper in an amount of .5-3.0%, which functions as a pearlite suppressor and thus an austenite-ferrite former. If the amount of these elements, singly or combined, were to be below .5%, then pearlite formation in larger castings will occur, and if exceeding 3.0%, the alloying agent would be wated and is uneconomical.
The above melt is fully solidified at a rate .
.
, 131 ~3 over a period of 4-16 minutes to ensure the formation of a carbon mixture in the form of 40-60% by volume graphite and the remainder eut`ectic carbide.
S Processing The solidification of the melt as indicated above is then subjected to a heat treatment sequence which comprises heating to an austenitizinq temperature in the range of 1560-1590F (848.9-865.6C) and held at such temperature for a period of 1.5-2.5 hours, during which time the casting will be fully austenitized. The casting is then quenched to a temperature level of 450-800F and held for a period of l.S-2.5 hours. The quench rate should be in the range of 300-375F per minute. If the-quench rate were to be slower than 300F
per minute, the~opportunity for formation o pearlite would be incrèased. If the quench rate were to exceed - 375F per minute, the tendency for forming quenching cracks (due to high thermal stresses) would be e~perienc-d. The quench rate is important because it attempts, by way of processing! to determine the desirable matrix of austenite and ferrite. By observing x ~ the quench rate and the required chemistry, such heat treatment 8equence will resu}~t in a cast iron matrix of austenite-ferrite having a suspended carbon mixture in the form of 40-60% flake graphite and the remainder in the~form of eutectia carbide particles. This proportioned~misture i~s one of the key aspects of providing for simultaneous enhancement of wear resistance 3~0~and impact resistance.~
Following the decomposition of austenite to hiqh - c~arbon~austenite and ferrite,~the casting or solidiflcation Ls th~en cooled to room temperature by air cooling.
35~
,: . , :: . . .
, .
131~93 g Microstructure The resulting casting will have a microstructure which consists of a high carbon austenite and ferrite matrix with a suspended mixture of flake graphite and eutectic carbide particles. There is a conspicuous absence of martensite or pearlite in the microstructure.
The suspended mixture particles constitute about 20~ by volume of the microstructure. The graphite particles will be in the form of type A flake graphite because of good inoculation using ferro-silicon. Such type A
graphite will influence the damping capacity, thermal conductivity, and machinability of the gray cast iron.
The physical characteristics of such gray cast iron will have a wear resistance which is at least 2-3 times greater than that of conventional gray cast irons, and with the limited samples that have been tested to date the wear resistance shows .0028-.0019 inch per 1000 ; hours of a conventional s~leeve test, such test being outlined in the Metals Handbook.
~ ; 20 In addition, the wear resistance is - ~ characterized by resistance to scuffing wherein the ratio of horsepower to produce scuffing divided by the normal horsepower is greater than 1.5. Gray cast iron, having a type A graphite in a martensitic matrix, normally exhibits a resistance to scuffing in the range of 1.39-1 45 ; The impact resistance was tested to be in the range of 25-35 ft/lbs, where a conventional gray cast iron has a charpy;notch impact value normally in the 30~ range of 1-2 ft/lbs.
~ The tensile strength of such resultant cast iron ?~ : is 45-55 ksi, which is in the high range for gray cast iron,~and elongation of about 1-2%. The hardness for such material is the range of 160-248 BHN.
35 ~
, , .
.. . . - -~ ' ~
: ~ ' , ' . ': ' lo - 13~ ~ ~93 ExamPles Several examples were prepared by melting a gray iron starting material which consisted of silicon in an amount of 2.3%, manganese .6~, with phosphorus being .12%, and sulphur being .10%. The carbon content of the gray iron was varied according to that shown in Table I
along with variations in the added carbide forming agent, and variations in the addition of nickel as an agent to encourage the decomposition of austenite to high austenite and ferrite. Heat Treatment was employed as indicated (such treatment being to heat the casting to 1570F for two hours, quench to 600F, and hold for two hours, then air cool). The wear resistance and impact resistance were recorded for each such example.
While various examples of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is intended to cover in the appended claims all such changes and equivalents as fall within the true spirit and scope of the invention.
, ,~ .
~, ,', .~:
:
,:
1 3 1 ~ 3 V V ~ N U~ ~" ~1 0 N
2~ ~0 =
a ~ ;~ O ~
.
~ N~ a 'e 3 3 Z ~ l æ
;~
~ ~ ~X
3 1~ 0 , ~ :
The additional carbide forming agent, which is added to the gray iron melt herein, comprises molybdenum, titanium, chromium, or vanadium. Any one or all of these ingredients may be added as long as they are present in the alloy melt in an amount in the range of .3-.8% as combined. If less than .3% is employed, the carbide volume will be too low; if greater than .8% is employed, then too much carbide will be present.
In order to promote the decomposition of austenite into high carbon austenite and ferrite, without the formation of pearlite or martensite, during the heat treatment and cooling sequence, it is desirable to add either nickel and/or copper in an amount of .5-3.0%, which functions as a pearlite suppressor and thus an austenite-ferrite former. If the amount of these elements, singly or combined, were to be below .5%, then pearlite formation in larger castings will occur, and if exceeding 3.0%, the alloying agent would be wated and is uneconomical.
The above melt is fully solidified at a rate .
.
, 131 ~3 over a period of 4-16 minutes to ensure the formation of a carbon mixture in the form of 40-60% by volume graphite and the remainder eut`ectic carbide.
S Processing The solidification of the melt as indicated above is then subjected to a heat treatment sequence which comprises heating to an austenitizinq temperature in the range of 1560-1590F (848.9-865.6C) and held at such temperature for a period of 1.5-2.5 hours, during which time the casting will be fully austenitized. The casting is then quenched to a temperature level of 450-800F and held for a period of l.S-2.5 hours. The quench rate should be in the range of 300-375F per minute. If the-quench rate were to be slower than 300F
per minute, the~opportunity for formation o pearlite would be incrèased. If the quench rate were to exceed - 375F per minute, the tendency for forming quenching cracks (due to high thermal stresses) would be e~perienc-d. The quench rate is important because it attempts, by way of processing! to determine the desirable matrix of austenite and ferrite. By observing x ~ the quench rate and the required chemistry, such heat treatment 8equence will resu}~t in a cast iron matrix of austenite-ferrite having a suspended carbon mixture in the form of 40-60% flake graphite and the remainder in the~form of eutectia carbide particles. This proportioned~misture i~s one of the key aspects of providing for simultaneous enhancement of wear resistance 3~0~and impact resistance.~
Following the decomposition of austenite to hiqh - c~arbon~austenite and ferrite,~the casting or solidiflcation Ls th~en cooled to room temperature by air cooling.
35~
,: . , :: . . .
, .
131~93 g Microstructure The resulting casting will have a microstructure which consists of a high carbon austenite and ferrite matrix with a suspended mixture of flake graphite and eutectic carbide particles. There is a conspicuous absence of martensite or pearlite in the microstructure.
The suspended mixture particles constitute about 20~ by volume of the microstructure. The graphite particles will be in the form of type A flake graphite because of good inoculation using ferro-silicon. Such type A
graphite will influence the damping capacity, thermal conductivity, and machinability of the gray cast iron.
The physical characteristics of such gray cast iron will have a wear resistance which is at least 2-3 times greater than that of conventional gray cast irons, and with the limited samples that have been tested to date the wear resistance shows .0028-.0019 inch per 1000 ; hours of a conventional s~leeve test, such test being outlined in the Metals Handbook.
~ ; 20 In addition, the wear resistance is - ~ characterized by resistance to scuffing wherein the ratio of horsepower to produce scuffing divided by the normal horsepower is greater than 1.5. Gray cast iron, having a type A graphite in a martensitic matrix, normally exhibits a resistance to scuffing in the range of 1.39-1 45 ; The impact resistance was tested to be in the range of 25-35 ft/lbs, where a conventional gray cast iron has a charpy;notch impact value normally in the 30~ range of 1-2 ft/lbs.
~ The tensile strength of such resultant cast iron ?~ : is 45-55 ksi, which is in the high range for gray cast iron,~and elongation of about 1-2%. The hardness for such material is the range of 160-248 BHN.
35 ~
, , .
.. . . - -~ ' ~
: ~ ' , ' . ': ' lo - 13~ ~ ~93 ExamPles Several examples were prepared by melting a gray iron starting material which consisted of silicon in an amount of 2.3%, manganese .6~, with phosphorus being .12%, and sulphur being .10%. The carbon content of the gray iron was varied according to that shown in Table I
along with variations in the added carbide forming agent, and variations in the addition of nickel as an agent to encourage the decomposition of austenite to high austenite and ferrite. Heat Treatment was employed as indicated (such treatment being to heat the casting to 1570F for two hours, quench to 600F, and hold for two hours, then air cool). The wear resistance and impact resistance were recorded for each such example.
While various examples of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is intended to cover in the appended claims all such changes and equivalents as fall within the true spirit and scope of the invention.
, ,~ .
~, ,', .~:
:
,:
1 3 1 ~ 3 V V ~ N U~ ~" ~1 0 N
2~ ~0 =
a ~ ;~ O ~
.
~ N~ a 'e 3 3 Z ~ l æ
;~
~ ~ ~X
3 1~ 0 , ~ :
Claims (11)
1. A method of making a more wear resistant gray cast iron with high wear resistance and impact strength, comprising:
(a) solidifying a hypoeutectic gray iron melt to which has been added (i) a carbide forming first agent in an amount of 0.3 to 0.8% by weight, selected from the group consisting of titanium, vanadium and molybdenum, and (ii) a high carbon austenite/ferrite forming agent in an amount of 0.5 to 3.0% by weight selected from the group consisting of nickel and copper, said solidification being at a rate to form a matrix with a mixture of flake graphite and eutectic carbide suspended in said matrix; and (b) heat treating said solid by (i) heating to a temperature and for a period of time to fully austenitize the solid, (ii) quenching said solid to a predetermined temperature level and holding at said level for a period of time to decompose austenite to form a high carbon austenite and ferrite matrix carrying in suspension a mixture of 40 to 60% flake graphite and the remainder eutectic carbide particles, and (iii) air cooling the solid to room temperature.
(a) solidifying a hypoeutectic gray iron melt to which has been added (i) a carbide forming first agent in an amount of 0.3 to 0.8% by weight, selected from the group consisting of titanium, vanadium and molybdenum, and (ii) a high carbon austenite/ferrite forming agent in an amount of 0.5 to 3.0% by weight selected from the group consisting of nickel and copper, said solidification being at a rate to form a matrix with a mixture of flake graphite and eutectic carbide suspended in said matrix; and (b) heat treating said solid by (i) heating to a temperature and for a period of time to fully austenitize the solid, (ii) quenching said solid to a predetermined temperature level and holding at said level for a period of time to decompose austenite to form a high carbon austenite and ferrite matrix carrying in suspension a mixture of 40 to 60% flake graphite and the remainder eutectic carbide particles, and (iii) air cooling the solid to room temperature.
2. The method of claim 1, in which said hypo-eutectic iron contains less than 4.35% carbon equivalent.
3. The method of claim 1, in which said hypo-eutectic gray iron melt comprises, by weight, 2.5 to 3.0% carbon, 2.0 to 2.5% silicon, 0.5 to 0.9% manganese, and the remainder iron.
4. The method of claim 1, in which said step (b)(i) comprises heating to 1560° to 1590°F for 1.5 to 2.5 hours.
5. The method of claim 1, in which step (b)(ii) comprises quenching to a temperature level of 450° to 800°F for 1.5 to 2.5 hours.
6. The method of claim 6, in which said quench rate is 300° to 375°F/minute..
7. The method of claim 1, in which solid formed by step (a) is a casting useful in automotive wear applications.
8. A product resulting from the practice of the method of claim 1, which is characterized by a tensile of 40 to 50 ksi, and an impact strength of 30 to 35 ft/lbs.
9. The product of claim 8, in which said wear resistance is 0.0019 to 0.0028 inch per 1000 hours of sleeve test.
10. The product of claim 9, in which said wear resistance is further characterized by a resistance to scuffing ratio greater than 1.5.
11. The product as in claim 8, in which the graphite for said product is in the type A form.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94514586A | 1986-12-22 | 1986-12-22 | |
| US945,145 | 1986-12-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1311993C true CA1311993C (en) | 1992-12-29 |
Family
ID=25482696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000553034A Expired - Lifetime CA1311993C (en) | 1986-12-22 | 1987-11-27 | Gray cast iron having both increased wear resistance and toughness |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0272788B1 (en) |
| JP (1) | JPS63166929A (en) |
| AU (1) | AU601249B2 (en) |
| CA (1) | CA1311993C (en) |
| DE (1) | DE3780138T2 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0272788B1 (en) * | 1986-12-22 | 1992-07-01 | Ford Motor Company Limited | A method of making wear resistant gray cast iron |
| US5242510A (en) * | 1992-09-25 | 1993-09-07 | Detroit Diesel Corporation | Alloyed grey iron having high thermal fatigue resistance and good machinability |
| GB9718982D0 (en) * | 1997-09-09 | 1997-11-12 | T & N Technology Ltd | Disc brake rotor |
| US6395107B1 (en) | 2000-01-28 | 2002-05-28 | Sundaresa V. Subramanian | Cast iron for use in high speed machining with cubic boron nitride and silicon nitride tools |
| DE10064248A1 (en) * | 2000-12-22 | 2002-07-04 | Zf Sachs Ag | Cast iron alloy for a friction element of a friction clutch and friction element for a friction clutch |
| CN102211178B (en) * | 2011-04-14 | 2013-09-18 | 河北坤腾泵业有限公司 | Composite suspending agent for producing roller sleeve and disc lining of vertical mill |
| ITUB20152456A1 (en) * | 2015-07-24 | 2017-01-24 | Zanardi Fond S P A | PROCEDURE FOR THE PRODUCTION OF MECHANICAL COMPONENTS IN LAMELLAR IRON OR VERMICULAR. |
| CN109609737B (en) * | 2018-12-13 | 2020-09-25 | 苏州东海玻璃模具有限公司 | Method for eliminating stress of vermicular graphite cast iron glass mold |
| CN113337686B (en) * | 2021-05-31 | 2022-02-18 | 东风商用车有限公司 | Engine cylinder cover and preparation method thereof |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR89010E (en) * | 1967-07-19 | |||
| GB545102A (en) * | 1940-05-30 | 1942-05-11 | Mond Nickel Co Ltd | Improvements relating to cast iron |
| GB840490A (en) * | 1957-06-06 | 1960-07-06 | Goetzewerke | Improvements relating to the manufacture of piston rings |
| US3384515A (en) * | 1965-06-21 | 1968-05-21 | Gen Motors Corp | Process of preparing improved cast iron articles |
| JPS55128563A (en) * | 1979-03-28 | 1980-10-04 | Nissan Motor Co Ltd | Cast iron excellent in wear and seizure resistance |
| US4230506A (en) * | 1979-05-06 | 1980-10-28 | Textron, Inc. | Cam shaft manufacturing process |
| JPS6052515A (en) * | 1983-09-01 | 1985-03-25 | Hitachi Metals Ltd | Manufacture of tough and hard gray cast iron |
| JPS6119759A (en) * | 1984-07-05 | 1986-01-28 | Toyota Motor Corp | Abrasion resistant cast iron |
| US4596606A (en) * | 1984-09-04 | 1986-06-24 | Ford Motor Company | Method of making CG iron |
| EP0272788B1 (en) * | 1986-12-22 | 1992-07-01 | Ford Motor Company Limited | A method of making wear resistant gray cast iron |
-
1987
- 1987-11-13 EP EP87310035A patent/EP0272788B1/en not_active Expired - Lifetime
- 1987-11-13 DE DE19873780138 patent/DE3780138T2/en not_active Expired - Lifetime
- 1987-11-24 JP JP29593687A patent/JPS63166929A/en active Pending
- 1987-11-27 CA CA000553034A patent/CA1311993C/en not_active Expired - Lifetime
- 1987-12-21 AU AU82879/87A patent/AU601249B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| DE3780138D1 (en) | 1992-08-06 |
| AU601249B2 (en) | 1990-09-06 |
| AU8287987A (en) | 1988-06-23 |
| EP0272788B1 (en) | 1992-07-01 |
| JPS63166929A (en) | 1988-07-11 |
| EP0272788A1 (en) | 1988-06-29 |
| DE3780138T2 (en) | 1993-02-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0174087B1 (en) | A method of making compacted graphite iron | |
| US2485760A (en) | Cast ferrous alloy | |
| EP1384794B1 (en) | Spheroidal cast iron particulary for piston rings and method for its production | |
| US4484953A (en) | Method of making ductile cast iron with improved strength | |
| US6258180B1 (en) | Wear resistant ductile iron | |
| US4891076A (en) | Gray cast iron having both increased wear resistance and toughness | |
| CA1311993C (en) | Gray cast iron having both increased wear resistance and toughness | |
| Sckudlarek et al. | Effect of austempering temperature on microstructure and mechanical properties of ductile cast iron modified by niobium | |
| Stefanescu | Classification and basic types of cast iron | |
| US4541878A (en) | Cast iron with spheroidal graphite and austenitic-bainitic mixed structure | |
| US2542655A (en) | Gray cast iron | |
| US4475956A (en) | Method of making high strength ferritic ductile iron parts | |
| Davis | Classification and basic metallurgy of cast irons | |
| Lee et al. | Influence of casting size and graphite nodule refinement on fracture toughness of austempered ductile iron | |
| JPH0238645B2 (en) | KOKYODOKYUJOKOKUENCHUTETSUNOSEIZOHOHO | |
| US4867804A (en) | Manufacturing process of toughened bainitic nodular graphite cast iron | |
| JPS627260B2 (en) | ||
| CN113462955B (en) | High-strength high-toughness isothermal quenching ductile iron material and preparation method and application thereof | |
| JP2567258B2 (en) | Iron-based casting having high strength, high rigidity, and high toughness, and a method for producing the same | |
| JPS6196054A (en) | Spheroidal graphite cast iron and manufacture thereof | |
| CN109280845B (en) | High-strength and high-toughness chromium ductile iron | |
| SU1725757A3 (en) | Wear-resistant cast iron | |
| Hafiz | „Influence of heat treatment parameters in variable austempering temperature process on mechanical properties and fracture of SG-iron” | |
| Kowalski et al. | Shaping the Structure and Properties of ADI with High Mn Content through Changes in Chemical Composition and Heat Treatment | |
| SU1763506A1 (en) | Wear-resistant cast iron |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |