CA1164777A - Cast iron with spheroidal graphite with austenitic- bainitic mixed structure - Google Patents
Cast iron with spheroidal graphite with austenitic- bainitic mixed structureInfo
- Publication number
- CA1164777A CA1164777A CA000353926A CA353926A CA1164777A CA 1164777 A CA1164777 A CA 1164777A CA 000353926 A CA000353926 A CA 000353926A CA 353926 A CA353926 A CA 353926A CA 1164777 A CA1164777 A CA 1164777A
- Authority
- CA
- Canada
- Prior art keywords
- cast iron
- weight
- temperature
- period
- minutes
- 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
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- 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 process for the production of spheroidal graphite cast iron with an austenitic-bainitic structure.
In this process, a cast iron containing up to 0.3 % of manganese and from 0.2 to 0.8 % of molybdenum is subjected to an austenitic heat treatment at a temperature of 800 to 860°C for a period of 10 to 60 minutes. The austenized cast-iron is then fast cooled in less than 2 minutes to a temperature of 350 to 400°C and held at this temperature for a period of 5 to 60 minutes.
A process for the production of spheroidal graphite cast iron with an austenitic-bainitic structure.
In this process, a cast iron containing up to 0.3 % of manganese and from 0.2 to 0.8 % of molybdenum is subjected to an austenitic heat treatment at a temperature of 800 to 860°C for a period of 10 to 60 minutes. The austenized cast-iron is then fast cooled in less than 2 minutes to a temperature of 350 to 400°C and held at this temperature for a period of 5 to 60 minutes.
Description
1 ~6~77~
The present invention is concerned with a process for the production of spheroidal graphite cast iron having a mixed austenitic-bainitic structure.
A spheroidal cast iron with the associated basic structure and mechanical properties - besides the usual spheres of application - is suitable as a production ma-terial for areas where until now heat treated steels had been used exclusively - for example crankshafts for motor-vehicle engines, segmented shafts and pistons for power assisted steering systems, fifth wheel kingpins for commer-cial vehicle couplings (semi-trailed), driveshaft heads for motor-vehicle driveshafts, and coupling bodies for trailer couplings.
Among spheroidal graphite cast irons, types with a bainitic structure have been known and in use for a long time, as being materials with a high tensile strength an~
high resistance to abrasion. During manufacture these castings are generally heated to an austenisation tempera-ture of 920 to 950C and maintained at this temperature for between 2 and 5 hours, until the carbon content of the matrix has become more or less evenly distributed and any ledeburite, which might be present after casting, has been dlssolved.
After the austenisation, the cast irons are cooled down so fast that a premature austenite transformation into pearlite iron is prevented prior to reaching the isothermal bainite transformation temperature. The cast iron is held at the bainitizing temperature until the baini-te reaction has stopped. The casting is then cooled - as usual - to room temperature (Giesserei (Foundry) 65 (brochure) (1978) No. 4, pages 73 to 80).
There is also spheroidal graphite cast iron with a bainite structure, which is based on alloyed cast iron, where directly in connection with the cooling process -B.~ 1 'P
7 7 ~
a bainite reaction is produced because of the con-tent of nickel, molybdenum, copper and possibly also chromium and manganese, depending on the wall thickness of the casting (German published application D.O.S. 18 08 515).
A slightly alloyed spheroidal graphite cast iron with conventional quantities of carbon, silicon, phosphorus, sulphur and magnesium, a molybdenum content of 0,10 to 0,26 % and a manganese content of 0,3 to 1,~ % is also known from German published application D.O.S. 23 34 992.
The casting which consis-ts of the above is hea-t treated to an austenisation temperature of 900C and after being held at this temperature for a period of two hours, is cooled in a bath at 300C for a period of ]0 minutes to 4 hours. As a result of these treatments it is possible to obtain an austenite-bainite structure, which gives a tensile strength of 1100 N/mm , an elongation at rupture at 10 ~ and a hardness of 270 to 300 HB.
According to the present invention, there is provided a process for producing a spheroidal graphite cast iron having an austenitic-bainitic structure and a manganese content of up to 0.3 ~, whi.ch does not interfer with favor-able properties.
The process according to the invention which is of the type comprising the steps of:
subjecting a cast iron containing manganese and molybdenum to an austenitic heat treatment, cooling the austenitized cast iron to a bainitizing temperature of 350 to 400C, preferably 375C, and holding the cast iron at this temperature for a period corresponding to the desired proportion of bainite, is characterized in that:
the cast iron used as starting material contains up to 0.3 % by weight of manganese and 0.2 to 0.8 ~ by weight of molybdenum;
The present invention is concerned with a process for the production of spheroidal graphite cast iron having a mixed austenitic-bainitic structure.
A spheroidal cast iron with the associated basic structure and mechanical properties - besides the usual spheres of application - is suitable as a production ma-terial for areas where until now heat treated steels had been used exclusively - for example crankshafts for motor-vehicle engines, segmented shafts and pistons for power assisted steering systems, fifth wheel kingpins for commer-cial vehicle couplings (semi-trailed), driveshaft heads for motor-vehicle driveshafts, and coupling bodies for trailer couplings.
Among spheroidal graphite cast irons, types with a bainitic structure have been known and in use for a long time, as being materials with a high tensile strength an~
high resistance to abrasion. During manufacture these castings are generally heated to an austenisation tempera-ture of 920 to 950C and maintained at this temperature for between 2 and 5 hours, until the carbon content of the matrix has become more or less evenly distributed and any ledeburite, which might be present after casting, has been dlssolved.
After the austenisation, the cast irons are cooled down so fast that a premature austenite transformation into pearlite iron is prevented prior to reaching the isothermal bainite transformation temperature. The cast iron is held at the bainitizing temperature until the baini-te reaction has stopped. The casting is then cooled - as usual - to room temperature (Giesserei (Foundry) 65 (brochure) (1978) No. 4, pages 73 to 80).
There is also spheroidal graphite cast iron with a bainite structure, which is based on alloyed cast iron, where directly in connection with the cooling process -B.~ 1 'P
7 7 ~
a bainite reaction is produced because of the con-tent of nickel, molybdenum, copper and possibly also chromium and manganese, depending on the wall thickness of the casting (German published application D.O.S. 18 08 515).
A slightly alloyed spheroidal graphite cast iron with conventional quantities of carbon, silicon, phosphorus, sulphur and magnesium, a molybdenum content of 0,10 to 0,26 % and a manganese content of 0,3 to 1,~ % is also known from German published application D.O.S. 23 34 992.
The casting which consis-ts of the above is hea-t treated to an austenisation temperature of 900C and after being held at this temperature for a period of two hours, is cooled in a bath at 300C for a period of ]0 minutes to 4 hours. As a result of these treatments it is possible to obtain an austenite-bainite structure, which gives a tensile strength of 1100 N/mm , an elongation at rupture at 10 ~ and a hardness of 270 to 300 HB.
According to the present invention, there is provided a process for producing a spheroidal graphite cast iron having an austenitic-bainitic structure and a manganese content of up to 0.3 ~, whi.ch does not interfer with favor-able properties.
The process according to the invention which is of the type comprising the steps of:
subjecting a cast iron containing manganese and molybdenum to an austenitic heat treatment, cooling the austenitized cast iron to a bainitizing temperature of 350 to 400C, preferably 375C, and holding the cast iron at this temperature for a period corresponding to the desired proportion of bainite, is characterized in that:
the cast iron used as starting material contains up to 0.3 % by weight of manganese and 0.2 to 0.8 ~ by weight of molybdenum;
- 2 -~,,,~
the austenitic heat -treatment is carried out a~
a temperature of 800 to 860C,preferably 820 to 830C,for a period of 10 to 60 minutes, preferably 10 to 25 minutes;
the cooling step is carried out in a fast manner over a period of less than 2 minutes; and the cast iron is held at the bainitizing tempera-ture for a period of 5 to 60 minutes, preferably 20 to 25 minutes.
The manganese content in the cast iron used as starting material may preferably lie in the range 0,01 to 0,25 % by weight. At least one of the following elements may be contained in the cast iron in the proportions specified:
nickel up to 3 ~ by weight molybdenum 0.2 to 0.8 ~ by weight copper 0.1 to 1 5 % by weight.
Molybdenum, if present, is preferably present in the proportion 0.25 to 0.4 % by weight. Copper, if present, is preferably present in the proportion 0.4 to 0.6 ~ by welght.
The cast iron used as starting material may also contain carbon and/or silicon. The carbon content may amount to 2,5 to 3,7 % - preferably 3,0 to 3,2 % by weight -and the silicon content 2,0 to 3,0 % - for preference 2,2 to 2,6 % by weight.
One of the advantages achieved with the process according to the invention is that - in comparison to the prior art processes - heat treatment is much less costly without impairing the good material properties shown by an austenite-balnite structure cast iron with spheroidal graphite.
The accompanying photographic illustration is of a metallographic specimen of a type of spheroidal graphite cast iron having a bainite austeni-te structure and enclosed
the austenitic heat -treatment is carried out a~
a temperature of 800 to 860C,preferably 820 to 830C,for a period of 10 to 60 minutes, preferably 10 to 25 minutes;
the cooling step is carried out in a fast manner over a period of less than 2 minutes; and the cast iron is held at the bainitizing tempera-ture for a period of 5 to 60 minutes, preferably 20 to 25 minutes.
The manganese content in the cast iron used as starting material may preferably lie in the range 0,01 to 0,25 % by weight. At least one of the following elements may be contained in the cast iron in the proportions specified:
nickel up to 3 ~ by weight molybdenum 0.2 to 0.8 ~ by weight copper 0.1 to 1 5 % by weight.
Molybdenum, if present, is preferably present in the proportion 0.25 to 0.4 % by weight. Copper, if present, is preferably present in the proportion 0.4 to 0.6 ~ by welght.
The cast iron used as starting material may also contain carbon and/or silicon. The carbon content may amount to 2,5 to 3,7 % - preferably 3,0 to 3,2 % by weight -and the silicon content 2,0 to 3,0 % - for preference 2,2 to 2,6 % by weight.
One of the advantages achieved with the process according to the invention is that - in comparison to the prior art processes - heat treatment is much less costly without impairing the good material properties shown by an austenite-balnite structure cast iron with spheroidal graphite.
The accompanying photographic illustration is of a metallographic specimen of a type of spheroidal graphite cast iron having a bainite austeni-te structure and enclosed
- 3 -,, , 1 ~6~77~
spherulites, as obtained by carrying out the process according to the invention. In this illustration, the dark needles are bainite and the light structural components are austenite.
~,~....
spherulites, as obtained by carrying out the process according to the invention. In this illustration, the dark needles are bainite and the light structural components are austenite.
~,~....
Claims (14)
1. A process for producing a spheroidal graphite cast iron having a mixed austenitic-bainitic structure, comprising the steps of subjecting a cast iron containing manganese and molybdenum to an austenitic heat treatment, cooling the austenitized cast iron to a bainitizing temperature of 350 to 400°C, and holding the cast iron at this temperature for a period corresponding to the desired proportion of bainite, characterized in that:
the cast iron used as starting material contains up to 0.3 % by weight of manganese and 0.2 to 0.8 % by weight of molybdenum;
the austenitic heat treatment is carried out at a temperature of 800 to 860°C for a period of 10 to 60 minutes;
the cooling step is carried out in a fast manner over a period of less than 2 minutes; and the cast iron is held at the bainitizing tempera-ture for a period of 5 to 60 minutes.
the cast iron used as starting material contains up to 0.3 % by weight of manganese and 0.2 to 0.8 % by weight of molybdenum;
the austenitic heat treatment is carried out at a temperature of 800 to 860°C for a period of 10 to 60 minutes;
the cooling step is carried out in a fast manner over a period of less than 2 minutes; and the cast iron is held at the bainitizing tempera-ture for a period of 5 to 60 minutes.
2. A process as claimed in claim 1, characterized in that the austenitic heat treatment is carried out at a temperature of 820 to 830°C.
3. A process as claimed in claim 1 or 2, charac-terized in that the austenitic heat treatment is carried out for a period of 10 to 25 minutes.
4. A process as claimed in claim 1, characterized in that the austenited cast iron is cooled to a temperature of about 375°C.
5. A process as claimed in any one of claim 1, characterized in that the cast iron is held at the bainitiz-ing temperature for a period of 20 to 25 minutes.
6. A process as claimed in claim 1, 2 or 5, characterized in that the cast iron used as starting ma-terial contains from 0.01 % to 0.25 % by weight of manganese.
7. A process as claimed in claim 1, characterized in that the cast iron used as starting material also contains up to 3 % by weight of nickel.
8. A process as claimed in claim 1, characterized in that the cast iron used as starting material also contains from 0.1 to 1.5 % by weight of copper.
9. A process as claimed in claim 8, wherein the content of copper is ranging from 0.4 to 0.6 % by weight.
10. A process as claimed in claim 1, wherein the content of molybdenum in the cast iron is ranging from 0.25 to 0.4 % by weight.
11. A process as claimed in claim 1, character-ized in that the cast iron used as starting material also contains from 2 to 3 % by weight of silicon.
12. A process as claimed in claim 11, wherein the content of silicon is ranging from 2.2 to 2.6 % by weight.
13. A process as claimed in claim 1, character-ized in that the cast iron used as starting material also contains from 2.5 to 3.7 % by weight of carbon.
14. A process as claimed in claim 13, wherein the content of carbon is ranging from 3.0 to 3.2 % by weight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353926A CA1164777A (en) | 1980-06-12 | 1980-06-12 | Cast iron with spheroidal graphite with austenitic- bainitic mixed structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353926A CA1164777A (en) | 1980-06-12 | 1980-06-12 | Cast iron with spheroidal graphite with austenitic- bainitic mixed structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164777A true CA1164777A (en) | 1984-04-03 |
Family
ID=4117171
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000353926A Expired CA1164777A (en) | 1980-06-12 | 1980-06-12 | Cast iron with spheroidal graphite with austenitic- bainitic mixed structure |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1164777A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4880477A (en) * | 1988-06-14 | 1989-11-14 | Textron, Inc. | Process of making an austempered ductile iron article |
| US5028281A (en) * | 1988-06-14 | 1991-07-02 | Textron, Inc. | Camshaft |
-
1980
- 1980-06-12 CA CA000353926A patent/CA1164777A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4880477A (en) * | 1988-06-14 | 1989-11-14 | Textron, Inc. | Process of making an austempered ductile iron article |
| US5028281A (en) * | 1988-06-14 | 1991-07-02 | Textron, Inc. | Camshaft |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |