Title of Invention	"A PROCESS FOR MANUFACTURING OF CRANKSHAFT LIKE MACHINE PART THROUGH COSTING OF DECTIVE ISON"
Abstract	The present invention provides a process for manufacturing of crankshaft through casting of ductile iron which solves the technical problems associated with the methods of manufacturing of crankshaft. The novel process of the present invention essentially comprises an alloy composition, casting, heat treatment and machining, wherein the novelty of manufacturing crankshaft is achieved by multi-step heat treatment followed by salt bath quenching.

Title of Invention

"A PROCESS FOR MANUFACTURING OF CRANKSHAFT LIKE MACHINE PART THROUGH COSTING OF DECTIVE ISON"

Abstract

The present invention provides a process for manufacturing of crankshaft through casting of ductile iron which solves the technical problems associated with the methods of manufacturing of crankshaft. The novel process of the present invention essentially comprises an alloy composition, casting, heat treatment and machining, wherein the novelty of manufacturing crankshaft is achieved by multi-step heat treatment followed by salt bath quenching.

Full Text	The present invention relates to a process for manufacturing of crankshaft through casting of ductile iron. The present invention particularly relates to a process which solves the technical problems associated with the methods of manufacturing of crankshaft. The main industrial usage of the process of the present invention is for the manufacture of automobile and I.C. engine components, such as crankshaft, sliding valve operating mechanism in reciprocating compressor. Machine or automobile components having mechanical properties, machinability property, reliability of durability and the power tolerance properties like that of a crankshaft is normally manufactured through the process of forging. Such class of forging process has its inbuilt merits and demerits, such as, higher mechanical properties, higher manufacturing cost due to high cost of dies, higher energy consumption, low rate of production, higher material wastage, lower damping properties. The search in the prior art indicates the knowledge in the public domain as follows: Reference may be made to US patent no. 5,551,995: Spheroidal graphite cast iron crank shaft and a crank shaft manufactured from such cast iron wherein spheroidal graphite cast iron for crank shafts having a tensile strength of 75 Kgf/mm. sup.2 or more and having excellent conformability and machinability.which cast iron consisting, by area ratio, of graphite of 5 to 15%, ferrite of not more than 10%, and balance pearlite matrix, said cast iron having a Brinell Hardness (HB) of 241 to 277. The drawbacks of this patent are as follows: (i) The strength and hardness of the crankshaft obtained is quite low. (ii) The patent does not talk about fatigue strength and impact energy and surely it will be low as austempering treatment is not imparted on the casting. Reference may be made to US patent no. 4,880,477: Process of making an austempered ductile iron article wherein an austempered ductile iron alloy with a mixed austenitic-bainitic structure is made by a method which enables the iron to withstand high cyclical stresses while having a high resistance to abration. Articles such as automobile roller follower camshafts that are made from the iron alloy may have portions thereof selectively austempered to reduce the overall cost and time required to manufacture the article. The drawbacks of this patent are: though author has given an example of camshaft development through austempered ductile iron (ADI) route, it is not clear whether the crankshaft like parts can be developed or not as because revolution per minute, torsoinal strength, UTS, bending and fatigue strength is much higher for crankshaft since what mechanical properties has been achieved in this patent is not mentioned. Reference may be made to US patent no. 5.753.055: Process for austempering includes austenizing a ductile iron casting of low alloy content followed by quenching the work piece for a controlled period of time in a quench medium such as water, an aqueous polymer solution or a medium speed quench oil. The work piece is then austempered in an air tempering furnace, resulting in a ausferrite microstcture essentially free of pearlite and martensite. The process eliminates the need for a molten salt bath for quenching and austempering. The drawbacks of this patent are as follows: i) The patent talks about the development of ADI on laboratory specimens but does not talk about development of real engineering components, ii) It does not say whether the bainite structure is stable after mechanical working. iii) It does not specify about fatigue properties of the developed material which is most important for developing crankshaft like machine parts that under goes cyclic loading. From the hitherto known prior art processes it is clear that there is a definite need to provide a process which solves the technical problems associated with the methods of manufacturing of crankshaft like products. The main object of the present invention is to provide a process of manufacturing crankshaft like machine part through casting of ductile iron, which obviates the drawbacks of the hitherto known prior art processes as detailed above. Another object of the present invention is to provide a process which enables ease of manufacture and can be cast with more dimensional precision than steel. Yet another object of the present invention is to provide a process wherein sand moulds are used instead of die, thus tooling cost will be negligible. Still another object of the present invention is to provide a process wherein production rate is very high. Still yet another object of the present invention is to provide a process which saves material as density of the component is less than forged one for equal strength. A further object of the present invention is to provide a process wherein costly forging route can be successfully replaced by casting route. In the present invention there is provided a process of manufacturing crankshaft like machine part through casting of ductile iron, wherein the cast iron having the broad composition as: 3.0 to 3.5 % of carbon, 2.0 to 2.6 % of silicon, 0.1 to 0.6 % manganese, 1.0 to 2.0 % nickel, 0.2 to 0.8 % of molybdenum, less than 0.02 % of sulphur and phosphorus is melted in a furnace and treated with 0.02 to 0.06 % magnesium and silicon dust in the ladle. This melt is poured into sand mould and allowed to cool to room temperature. The cast product so obtained is pre-heating at a temperature in the range of 350 to 450 degree Centigrade followed by heating to a temperature in the range of 790 to 910 degree Centigrade in a conventional furnace with a residence time of 2.5 to 3.5 hours and then quenched into a salt bath that is maintained at a temperature in the range of 250 to 400 degree Centigrade. The residence time in the salt bath being 2.5 to 3.5 hours. The product is finished by conventional machining. The novel process of the present invention essentially comprises: an alloy composition, casting, heat treatment and machining, wherein the novelty of manufacturing crankshaft like machine part through casting of ductile iron is achieved by the non-obvious inventive steps involving multi-step heat treatment followed by salt bath quenching. Accordingly the present invention provides a process for manufacturing of crankshaft characterized in that it comprises the step of casting of ductile iron involving multi-step heat treatment followed by salt bath quenching with a definite temperature range and residence time, the said process comprises melting cast iron in a furnace and treating the melt with 0.02 to 0.06 % magnesium and silicon dust, pouring the treated melt into a sand mould and allowing to cool to room temperature, subjecting the casting so obtained to pre-heating at a temperature in the range of 350 to 450 degree Centigrade followed by heating to a temperature in the range of 790 to 910 degree Centigrade in a furnace with a residence time of 2.5 to 3.5 hours, quenching the heat treated casting in a salt bath maintained at a temperature in the range of 250 to 400 degree Centigrade, for a residence time in the salt bath of 2.5 to 3.5 hours, removing the casting from the salt bath and allowing to cool in air to room temperature, subjecting the cooled casting to machining to get desired crankshaft. In an embodiment of the present invention the cast iron is having the broad composition as, 3.0 to 3.5% of carbon, 2.0 to 2.6% of silicon, 0.1 to 0.6% manganese, 1.0 to 2.0% nickel, 0.2 to 0.8% of molybdenum, less than 0.02% of sulphur and phosphorus. The novel process of the present invention of manufacturing machine elements such as crank shaft through the route of casting and the subsequent heat treatment and then machining has been described in the following example which should not be construed to limit the scope of the present invention. Example-1 A 5HP reciprocating single throw Kirloskar oil engine crankshaft was developed using austempered ductile iron. Pattern for casting was prepared incorporating machining and shrinkage allowance. Green sand mould was prepared using that pattern. Ductile iron was prepared with the composition by weight, 3.3 % carbon, 2.5% silicon, 0.5% manganese, 1.5% nickel, 0.5% molybdenum, sulphur and phosphorus below 0.02%, 0.04% magnesium. The ductile iron was poured inside the mould at the temperature 1320 degree C. Then the casting was allowed to cool inside the mould to room temperature. Then the casting was cleaned and runners, risers are cutoff. Machining of the cast crankshaft including oil holes was done leaving only 0.2 micron grinding allowance. Heat treatment of the crankshaft was carried out by putting the casting inside a furnace and holding the casting at a temperature 850 degree C. for 2 hours. Then quenched in a salt bath at temperature 330 degree and kept at that temperature for 1.5 hours. Then casting was taken out from the salt bath and kept in open air and cooled to room temperature. In-situ metallography of the heat treated crankshaft was carried out and it was found that the microstructure consisted of lower bainite with considerable amount of retained austenite. Final grinding and balancing of the crankshaft was done and dimensional measurements were carried out where wear may take place. The crankshaft was fitted inside a new 5 hp Kirloskar oil engine which was connected with centrifugal irrigation pump load. Lubrication oil (lube oil) was poured up to the level marked in the engine. Temperature of the lube oil is an indication of friction between journal and bearing. Cooling water lines (inlet & outlet) were connected with the engine block to cool the engine. Temperature of the outlet cooling water and exhaust temperature of the engine is an indicator of the normal and stable running of the engine. An irrigation pump load was connected with the 5 hp Kirloskar oil engine fitted with the developed crank shaft to extract ground water and to pump it to irrigational paddy field. The engine with the pump load was run for 109 hours as shown in Table 1.0 and found that running of the engine was very stable. Engine was run at 1490 RPM without load and 1420 RPM with load Total hours run was 109.5 hours. Total fuel consumed during running the engine =102 Its. Table-1 Performance evaluation of ADI crankshaft for 5HP reciprocating single throw Kirloskar oil engine(Table Removed) Weight of ADI crankshaft before field trial: 851860 gms. Weight of the ADI crankshaft after field trial: 851860 gms. After the field trial, the crankshaft was taken out of the engine and dimensional measurements were carried out again and found that no wear has been taken place. Micrograph of the crankshaft was taken after field trial by in-situ and found bainite structure was stable. The novelty of the process of the present invention resides in the novel route for manufacturing a crankshaft and the similar items by casting and then heat treating in a specific sequence. The process essentially comprises: an alloy composition, casting, heat treatment and machining. The novelty of manufacturing crankshaft like machine part through casting of ductile iron is achieved by the non-obvious inventive steps involving multi-step heat treatment with the prescribed temperature range and the residence time, and the sequence of operation, starting with the cast iron and reaching to the heat treated ductile iron followed by salt bath quenching with the prescribed temperature range and the residence time, thus providing the required mechanical properties of the final cast product. The main advantages of the present invention are: 1) The material is easy to manufacture and can be cast with more dimensional precision than steel. 2) Since sand moulds are used instead of die, tooling cost is negligible. 3) Production rate is very high.Saves material as density of the component is less than forged one for equal strength.Costly forging route can be successfully replaced by casting route. We Claim: 1. A process for manufacturing crankshaft characterized in that it comprises the step of casting of ductile iron involving multi-step heat treatment followed by salt bath quenching with a definite temperature range and residence time, the said process comprises melting cast iron in a furnace and treating the melt with 0.02 to 0.06 % magnesium and silicon dust, pouring the treated melt into a sand mould and allowing to cool to room temperature, subjecting the casting so obtained to pre-heating at a temperature in the range of 350 to 450 degree Centigrade followed by heating to a temperature in the range of 790 to 910 degree Centigrade in a furnace with a residence time of 2.5 to 3.5 hours, quenching the heat treated casting in a salt bath maintained at a temperature in the range of 250 to 400 degree Centigrade, for a residence time in the salt bath of 2.5 to 3.5 hours, removing the casting from the salt bath and allowing to cool in air to room temperature, subjecting the cooled casting to machining to get desired crankshaft. 2. A process as claimed in claim 1, wherein the cast iron used is comprising 3.0 to 3.5% of carbon, 2.0 to 2.6% of silicon, 0.1 to 0.6% manganese, 1.0 to 2.0% nickel, 0.2 to 0.8% of molybdenum and less than 0.02% of sulphur and phosphorus. 3. A process for manufacturing of crankshaft through casting of ductile iron, substantially as herein described with reference to the example.

Full Text

The present invention relates to a process for manufacturing of crankshaft through casting of ductile iron. The present invention particularly relates to a process which solves the technical problems associated with the methods of manufacturing of crankshaft.
The main industrial usage of the process of the present invention is for the manufacture of automobile and I.C. engine components, such as crankshaft, sliding valve operating mechanism in reciprocating compressor.
Machine or automobile components having mechanical properties, machinability property, reliability of durability and the power tolerance properties like that of a crankshaft is normally manufactured through the process of forging. Such class of forging process has its inbuilt merits and demerits, such as, higher mechanical properties, higher manufacturing cost due to high cost of dies, higher energy consumption, low rate of production, higher material wastage, lower damping properties.
The search in the prior art indicates the knowledge in the public domain as follows: Reference may be made to US patent no. 5,551,995: Spheroidal graphite cast iron crank shaft and a crank shaft manufactured from such cast iron wherein spheroidal graphite cast iron for crank shafts having a tensile strength of 75 Kgf/mm. sup.2 or more and having excellent conformability and machinability.which cast iron consisting, by area ratio, of graphite of 5 to 15%, ferrite of not more than 10%, and balance pearlite matrix, said cast iron having a Brinell Hardness (HB) of 241 to 277. The drawbacks of this patent are as follows:
(i) The strength and hardness of the crankshaft obtained is quite low.
(ii) The patent does not talk about fatigue strength and impact energy and surely it will be low as austempering treatment is not imparted on the casting.
Reference may be made to US patent no. 4,880,477: Process of making an austempered ductile iron article wherein an austempered ductile iron alloy with a mixed austenitic-bainitic structure is made by a method which enables the iron to withstand high cyclical stresses while having a high resistance to abration. Articles such as automobile roller follower camshafts that are made from the iron alloy may have portions thereof selectively austempered to reduce the overall cost and time required to manufacture the article. The drawbacks of this patent are: though author has given an example of camshaft development through austempered ductile iron (ADI) route, it is not clear whether the crankshaft like parts can be developed or not as because revolution per minute, torsoinal strength, UTS, bending and fatigue strength is much higher for crankshaft since what mechanical properties has been achieved in this patent is not mentioned.
Reference may be made to US patent no. 5.753.055: Process for austempering includes austenizing a ductile iron casting of low alloy content followed by quenching the work piece for a controlled period of time in a quench medium such as water, an aqueous polymer solution or a medium speed quench oil. The work piece is then austempered in an air tempering furnace, resulting in a ausferrite microstcture essentially free of pearlite and martensite. The process eliminates the need for a molten salt bath for quenching and austempering. The drawbacks of this patent are as follows:
i) The patent talks about the development of ADI on laboratory specimens but does not talk about development of real engineering components, ii) It does not say whether the bainite structure is stable after mechanical
working.
iii) It does not specify about fatigue properties of the developed material which is most important for developing crankshaft like machine parts that under goes cyclic loading.
From the hitherto known prior art processes it is clear that there is a definite need to provide a process which solves the technical problems associated with the methods of manufacturing of crankshaft like products.
The main object of the present invention is to provide a process of manufacturing crankshaft like machine part through casting of ductile iron, which obviates the drawbacks of the hitherto known prior art processes as detailed above.
Another object of the present invention is to provide a process which enables ease of manufacture and can be cast with more dimensional precision than steel.
Yet another object of the present invention is to provide a process wherein sand moulds are used instead of die, thus tooling cost will be negligible.
Still another object of the present invention is to provide a process wherein production rate is very high.
Still yet another object of the present invention is to provide a process which saves material as density of the component is less than forged one for equal strength.
A further object of the present invention is to provide a process wherein costly forging route can be successfully replaced by casting route.
In the present invention there is provided a process of manufacturing crankshaft like machine part through casting of ductile iron, wherein the cast iron having the broad composition as: 3.0 to 3.5 % of carbon, 2.0 to 2.6 % of silicon, 0.1 to 0.6 % manganese, 1.0 to 2.0 % nickel, 0.2 to 0.8 % of molybdenum, less than 0.02 % of sulphur and phosphorus is melted in a furnace and treated with 0.02 to 0.06 % magnesium and silicon dust in the ladle. This melt is poured into sand mould and allowed to cool to room temperature. The cast product so obtained is pre-heating
at a temperature in the range of 350 to 450 degree Centigrade followed by heating to a temperature in the range of 790 to 910 degree Centigrade in a conventional furnace with a residence time of 2.5 to 3.5 hours and then quenched into a salt bath that is maintained at a temperature in the range of 250 to 400 degree Centigrade. The residence time in the salt bath being 2.5 to 3.5 hours. The product is finished by conventional machining. The novel process of the present invention essentially comprises: an alloy composition, casting, heat treatment and machining, wherein the novelty of manufacturing crankshaft like machine part through casting of ductile iron is achieved by the non-obvious inventive steps involving multi-step heat treatment followed by salt bath quenching.
Accordingly the present invention provides a process for manufacturing of crankshaft characterized in that it comprises the step of casting of ductile iron involving multi-step heat treatment followed by salt bath quenching with a definite temperature range and residence time, the said process comprises melting cast iron in a furnace and treating the melt with 0.02 to 0.06 % magnesium and silicon dust, pouring the treated melt into a sand mould and allowing to cool to room temperature, subjecting the casting so obtained to pre-heating at a temperature in the range of 350 to 450 degree Centigrade followed by heating to a temperature in the range of 790 to 910 degree Centigrade in a furnace with a residence time of 2.5 to 3.5 hours, quenching the heat treated casting in a salt bath maintained at a temperature in the range of 250 to 400 degree Centigrade, for a residence time in the salt bath of 2.5 to 3.5 hours, removing the casting from the salt bath and allowing to cool in air to room temperature, subjecting the cooled casting to machining to get desired crankshaft.
In an embodiment of the present invention the cast iron is having the broad composition as, 3.0 to 3.5% of carbon, 2.0 to 2.6% of silicon, 0.1 to 0.6% manganese, 1.0 to 2.0% nickel, 0.2 to 0.8% of molybdenum, less than 0.02% of sulphur and phosphorus.
The novel process of the present invention of manufacturing machine elements such as crank shaft through the route of casting and the subsequent heat treatment and then machining has been described in the following example which should not be construed to limit the scope of the present invention.
Example-1
A 5HP reciprocating single throw Kirloskar oil engine crankshaft was developed using austempered ductile iron. Pattern for casting was prepared incorporating machining and shrinkage allowance. Green sand mould was prepared using that pattern. Ductile iron was prepared with the composition by weight, 3.3 % carbon, 2.5% silicon, 0.5% manganese, 1.5% nickel, 0.5% molybdenum, sulphur and phosphorus below 0.02%, 0.04% magnesium. The ductile iron was poured inside the mould at the temperature 1320 degree C. Then the casting was allowed to cool inside the mould to room temperature. Then the casting was cleaned and runners, risers are cutoff. Machining of the cast crankshaft including oil holes was done leaving only 0.2 micron grinding allowance. Heat treatment of the crankshaft was carried out by putting the casting inside a furnace and holding the casting at a temperature 850 degree C. for 2 hours. Then quenched in a salt bath at temperature 330 degree and kept at that temperature for 1.5 hours. Then casting was taken out from the salt bath and kept in open air and cooled to room temperature. In-situ metallography of the heat treated crankshaft was carried out and it was found that the microstructure consisted of lower bainite with considerable amount of retained austenite. Final grinding and balancing of the crankshaft was done and dimensional measurements were carried out where wear may take place. The crankshaft was fitted inside a new 5 hp Kirloskar oil engine which was connected with centrifugal irrigation pump load. Lubrication oil (lube oil) was poured up to the level marked in the engine. Temperature of the lube oil is an indication of friction between journal and bearing. Cooling water lines (inlet & outlet) were connected with the engine block to cool the engine. Temperature of the outlet cooling water and exhaust temperature of the engine is
an indicator of the normal and stable running of the engine. An irrigation pump load was connected with the 5 hp Kirloskar oil engine fitted with the developed crank shaft to extract ground water and to pump it to irrigational paddy field. The engine with the pump load was run for 109 hours as shown in Table 1.0 and found that running of the engine was very stable.
Engine was run at 1490 RPM without load and 1420 RPM with load
Total hours run was 109.5 hours.
Total fuel consumed during running the engine =102 Its.
Table-1
Performance evaluation of ADI crankshaft for 5HP reciprocating single throw Kirloskar oil engine(Table Removed)
Weight of ADI crankshaft before field trial: 851860 gms.
Weight of the ADI crankshaft after field trial: 851860 gms.
After the field trial, the crankshaft was taken out of the engine and dimensional
measurements were carried out again and found that no wear has been taken
place. Micrograph of the crankshaft was taken after field trial by in-situ and found
bainite structure was stable.
The novelty of the process of the present invention resides in the novel route for manufacturing a crankshaft and the similar items by casting and then heat treating in a specific sequence. The process essentially comprises: an alloy composition, casting, heat treatment and machining.
The novelty of manufacturing crankshaft like machine part through casting of ductile iron is achieved by the non-obvious inventive steps involving multi-step heat treatment with the prescribed temperature range and the residence time, and the sequence of operation, starting with the cast iron and reaching to the heat treated ductile iron followed by salt bath quenching with the prescribed temperature range and the residence time, thus providing the required mechanical properties of the final cast product.
The main advantages of the present invention are:
1) The material is easy to manufacture and can be cast with more
dimensional precision than steel.
2) Since sand moulds are used instead of die, tooling cost is negligible.
3) Production rate is very high.Saves material as density of the component is less than forged one for
equal strength.Costly forging route can be successfully replaced by casting route.

We Claim:
1. A process for manufacturing crankshaft characterized in that it comprises
the step of casting of ductile iron involving multi-step heat treatment
followed by salt bath quenching with a definite temperature range and
residence time, the said process comprises melting cast iron in a
furnace and treating the melt with 0.02 to 0.06 % magnesium and silicon
dust, pouring the treated melt into a sand mould and allowing to cool to
room temperature, subjecting the casting so obtained to pre-heating at a
temperature in the range of 350 to 450 degree Centigrade followed by
heating to a temperature in the range of 790 to 910 degree Centigrade in
a furnace with a residence time of 2.5 to 3.5 hours, quenching the heat
treated casting in a salt bath maintained at a temperature in the range of
250 to 400 degree Centigrade, for a residence time in the salt bath of 2.5
to 3.5 hours, removing the casting from the salt bath and allowing to cool
in air to room temperature, subjecting the cooled casting to machining to
get desired crankshaft.
2. A process as claimed in claim 1, wherein the cast iron used is comprising
3.0 to 3.5% of carbon, 2.0 to 2.6% of silicon, 0.1 to 0.6% manganese, 1.0
to 2.0% nickel, 0.2 to 0.8% of molybdenum and less than 0.02% of
sulphur and phosphorus.
3. A process for manufacturing of crankshaft through casting of ductile iron,
substantially as herein described with reference to the example.

Documents:

1178-del-2003-abstract.pdf

1178-del-2003-claims.pdf

1178-DEL-2003-Correspondence-Others.pdf

1178-del-2003-correspondence-po.pdf

1178-del-2003-description (complete).pdf

1178-del-2003-form-1.pdf

1178-DEL-2003-Form-18.pdf

1178-del-2003-form-2.pdf

1178-del-2003-form-3.pdf

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Patent Number

210335

Indian Patent Application Number

1178/DEL/2003

PG Journal Number

01/2008

Publication Date

04-Jan-2008

Grant Date

28-Sep-2007

Date of Filing

19-Sep-2003

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI - 110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	MANOJ KUMAR JAS	CMERI, DURGAPUR, INIDA.
2	SUDIP KUMAR SAMANTA	CMERI, DURGAPUR, INIDA.
3	DEBI PRASAD CHATTOPADHYAY	CMERI, DURGAPUR, INIDA.
4	SIDDHARTHA KUMAR	CMERI, DURGAPUR, INIDA.

PCT International Classification Number

B22C 9/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA