Title of Invention	INTEGRATED THERMOMECHANICAL PROCESS TO ACHIEVE MINIMUM STRENGTH IN 10% DEPTH
Abstract	The present invention comprises of thermo-mechanical process & optimized C-Mn type steel to produce heat treatment response of achieving desired strength in minimum top 10% of the surface layer without need for micro alloy addition. Thus, the low cost steel grade composition and its integrated processing is developed which produces required strength & micro structural effect in minimum top 10% of surface layer suitable for automotive and general engineering application.

Title of Invention

INTEGRATED THERMOMECHANICAL PROCESS TO ACHIEVE MINIMUM STRENGTH IN 10% DEPTH

Abstract

The present invention comprises of thermo-mechanical process & optimized C-Mn type steel to produce heat treatment response of achieving desired strength in minimum top 10% of the surface layer without need for micro alloy addition. Thus, the low cost steel grade composition and its integrated processing is developed which produces required strength & micro structural effect in minimum top 10% of surface layer suitable for automotive and general engineering application.

Full Text	FORM 2 THE PATENT ACT 1970 & The Patents Rules, 2003 PROVISIONAL / GOMPL^T^^PECTFTCATION' (See section 10 and rule 13) 1. TITLE OF THE INVENTION "THERMODYNAMIC PROCESS TO ACHIEVE MINIMUM STRENGTH IN) 10% DEPTH." 2. APPLICANT (a) NAME : MAHINDRA & MAHINDRA LTD. (b) NATIONALITY: Indian Company registered under the provisions of the Companies Act, 1956 (c) ADDRESS : R&D CENTRE, AUTO SECTOR, 89, M.I.D.C, NASHIK- 422007. Maharashtra State, India 3. PREAMBLE TO THE DESCRIPTION PROVISIONAL The following specification describes the invention. COMPLETE The Following specification particularly describes the invention and the manner in which it: performed. 4. DESCRIPTION (Description starts from page 2) 5. CLAIMS: N.A 6. DATE AND SIGNATURE: Given at the end of last page of specification. 7. ABSTRACT OF THE INVENTION: N.A 1 Technical Field: The present invention relates to a thermomechanical process to achieve minimum strength in 10% depth. More particularly, the present invention relates to a thermomechanical process for steel forgings to achieve desired strength in minimum top 10% of surface layer. Prior Art: The hot forming of steel is a type of thermomechanical process which involves heating of cut billets/bars in electric or fuel fired equipment followed by shaping in dies in various deformation steps using hammers/presses. The excess metal which comes out as peripheral flash is trimmed off. On completion of trimming operation, the forged parts are cooled naturally to room temperature. Then they undergo different heat treatment processes using batch or continous type electrical or fuel fired furnaces, located at different location generally called as "Heat treatment section." The heat treatment processes could be normalizing, isothermal annealing or hardening or tempering or sherodised annealing or solution treatment. The automotive component designs are optimized for shape, size and weight to provide required stiffnes and strength. For fatigue /dynamic load service conditions, the strength ranges of 660-790MPa, 820-980MPa, 850-lOOOMPa are very common and constitutes a large volume production for automotive and general engineering applications. Many types of plain carbon and alloy steels are being used to get above strength levels by carrying out subsequent hardening and tempering treatments. These days micro alloy steels containing small micro alloy additions of Nb, Ti etc are used for forging where the forgings are cooled in controlled manner to achieve 2 precipitation of micro constituents like nitrides, carbonitrides which gives required strengthening of the parts and thus need for separate quenching and tempering process is avoided. These micro alloy additions are expensive and have poor machinability and hence calls for additional requirement of sulfur addition. The prior art is illustrated in figure 1.of the accompanying drawing. Figure 1. shows the schematic graphical representation of existing process of Hot forming(Pl) and subsequent heat treatment processes(P2, P3, P4). PI consists of 1,2 & 3. P2 consists of 4, 5 & 6 P3 consists of 4, 5 & 7 P4 consists of 4, 5 & 8 (1) indicates heating upto 1200 deg C , (2) indicates forging at 1200 deg C, (3) indicates air cooling to room temperature(RT), (4) indicates reheating upto 900 deg C, (5) indicates forging, (6),(7) & (8) indicates cooling at different rates. Deficiencies or drawbacks of Prior Art: 1. Separate hardening and tempering process are necessary after hot forging to produce desired strength levels. 2. Expensive micro alloy additions are needed to produce desired microstructure for Controlled cooling. 3. Large amount of thermal energy is consumed during different repeated heating processes. 4. Longer cycle time (loading, process and unloading time for subsequent processes.) 5. Repeated material handling and transportation. 6. Higher equipment cost i.e furnace for subsequent heat treatment processes. 7.Higher environmental impact i.e fossil fuel depletion, emission of gases. 3 Summary of the Invention: The present invention comprises of the chemical composition of C-Mn type steel which is optimized to produce heat treatment response of achieving desired microstructure in minimum top 10% of the surface layer without need for micro alloy addition . Thus, the low cost steel grade composition and its integrated processing is developed which produces required microstructural effect in minimum top 10% of surface layer suitable for automotive and general engineering applications. The main objective of the present invention is to manufacture low cost automotive and general engineering forged components where the required strength levels are achieved in top minimum 10% of surface layer to withstand the fatigue load condition. The purpose of the present invention is to utilise residual heat of forging to integrate hot forming process with subsequent heat treatment process for controlled transformation and thereby eliminating need for subsequent hardening and tempering process. Advantages of the Present Invention: 1. No separate hardening and tempering processes are required after hot forging to produce desired strength levels. 2. The required strength level is achieved in top minimum 10% of surface layer by tailoring low cost alloy. 3. Large amount of thermal energy is saved as different repeated heating processes are eliminated. 4. The cycle time is reduced as reheating processes are eliminated. 5. Cost of the new integrated set up is much lower than furnace cost as it uses the residual heat and no separate heating coils are required. 4 Description of the Present Invention: Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter. The steel forging for automotive and general engineering applications are made from different types of plain carbon and alloy steels and are quenched and tempered after hot forging process to three different types of strength levels (viz. 660-790 MPa, 820-980 MPa, 850-1000 MPa). As the fatigue failure initiate at the surface, in reality , the above strength levels are required to be present in minimum top 10% of surface layer. This change in concept of component design is used to develop low cost steel chemistries suitable to produce required strengths in top minimum 10% of the layer by integrating hot forging processes and its subsequent heat treatment thereby the residual heat of forging can be saved. The forgings are forged at higher side of the recommended temperature so that advantage of higher austenizing temperature is achieved to get enhanced hardenability and cooling starts from the temperature above 900° C. This helps to get required strength in top 10% of the outer layer. The steel alloy compositions are based on low cost consideration by use of varying carbon and manganese content for the required strength levels. For different part weight and section thickness these composition ranges and the corresponding cooling rates can be varied to get desired results. Also small addition like Cr (0.15 - 0.30%) and Mo (0.08-0.15%) can be done to get required results. 5 Based on the chemistry range chosen, the required minimum cooling rate can be decided using theoretical calculations to predict time - temperature transformation curves. The alloy chemistries and the min cooling rate to get three types of strength levels are shown in the following table. Strength level(MPa) Approx.Equivalent Hardness (BHN) Chemistry Range* Forging & triming operaton. At 10 & 11. Cooling Rate at 12. 660-790 190-230 %C= 0.35-0.55 %Mn= 0.6-1.25 Temp, range 1200 to 900 deg Cooling rate of 30-350Deg.C/minute. (from still air toforced airincluding additionof mist). 820-950 241-285 %C= 0.35-0.55 %Mn= 1.0-1.65 850-100 248-302 %C= 0.38-0.55 %Mn= 1.0-1.65 * These are predominant chemistry limits. The steel generally contains other elements like Si, S, P, Al, N, Cr, Ni, Mo, V and the limits for these can be as per national and international standards and steel making practices related to forging quality steels. Various automotive components like crankshaft, suspension , knuckles , connecting rods, wheel bearing spindles, levers, companion flange, axle shafts, etc were processed by above methods and validated by actual testing for satisfactory performance. The present invention is illustrated in figure 2 of the accompanying drawing. Figure 2 shows the schematic graphical representation of the new method of Integrated heating i.e forging+ different heat treatment processes. (9) indicates heating upto 1200 deg C, (10) indicates forging start at 1200 deg C, (11) indicates forging finish 6 & triming operation at temp, range of 1200 to 900 deg C , (12) indicates cooling from temperature range of 1200 to 900 deg. C to temperature range of 300 deg C to ambient temp, by using cooling rate of 30 to 350 deg. C per minute. Dated this 26m of May, 2006. M..D.BHATE AGENT FOR THE APPLICANT 7

Full Text

FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL / GOMPL^T^^PECTFTCATION' (See section 10 and rule 13)
1. TITLE OF THE INVENTION
"THERMODYNAMIC PROCESS TO ACHIEVE MINIMUM STRENGTH IN) 10% DEPTH."
2. APPLICANT
(a) NAME : MAHINDRA & MAHINDRA LTD.
(b) NATIONALITY: Indian Company registered under the provisions of the
Companies Act, 1956
(c) ADDRESS : R&D CENTRE, AUTO SECTOR,
89, M.I.D.C,
NASHIK- 422007. Maharashtra State, India
3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specification describes the invention.

COMPLETE
The Following specification particularly describes the invention and the manner in which it: performed.

4. DESCRIPTION (Description starts from page 2)

5. CLAIMS:

N.A

6. DATE AND SIGNATURE: Given at the end of last page of specification.
7. ABSTRACT OF THE INVENTION: N.A
1

Technical Field:
The present invention relates to a thermomechanical process to achieve minimum strength in 10% depth. More particularly, the present invention relates to a thermomechanical process for steel forgings to achieve desired strength in minimum top 10% of surface layer.
Prior Art:
The hot forming of steel is a type of thermomechanical process which involves heating of cut billets/bars in electric or fuel fired equipment followed by shaping in dies in various deformation steps using hammers/presses. The excess metal which comes out as peripheral flash is trimmed off. On completion of trimming operation, the forged parts are cooled naturally to room temperature. Then they undergo different heat treatment processes using batch or continous type electrical or fuel fired furnaces, located at different location generally called as "Heat treatment section."
The heat treatment processes could be normalizing, isothermal annealing or hardening or tempering or sherodised annealing or solution treatment.
The automotive component designs are optimized for shape, size and weight to provide required stiffnes and strength. For fatigue /dynamic load service conditions, the strength ranges of 660-790MPa, 820-980MPa, 850-lOOOMPa are very common and constitutes a large volume production for automotive and general engineering applications. Many types of plain carbon and alloy steels are being used to get above strength levels by carrying out subsequent hardening and tempering treatments.
These days micro alloy steels containing small micro alloy additions of Nb, Ti etc are used for forging where the forgings are cooled in controlled manner to achieve
2

precipitation of micro constituents like nitrides, carbonitrides which gives required strengthening of the parts and thus need for separate quenching and tempering process is avoided. These micro alloy additions are expensive and have poor machinability and hence calls for additional requirement of sulfur addition.
The prior art is illustrated in figure 1.of the accompanying drawing.
Figure 1. shows the schematic graphical representation of existing process of Hot
forming(Pl) and subsequent heat treatment processes(P2, P3, P4).
PI consists of 1,2 & 3.
P2 consists of 4, 5 & 6
P3 consists of 4, 5 & 7
P4 consists of 4, 5 & 8
(1) indicates heating upto 1200 deg C , (2) indicates forging at 1200 deg C, (3) indicates
air cooling to room temperature(RT), (4) indicates reheating upto 900 deg C, (5) indicates
forging, (6),(7) & (8) indicates cooling at different rates.
Deficiencies or drawbacks of Prior Art:
1. Separate hardening and tempering process are necessary after hot forging to produce desired strength levels.
2. Expensive micro alloy additions are needed to produce desired microstructure for Controlled cooling.
3. Large amount of thermal energy is consumed during different repeated heating processes.
4. Longer cycle time (loading, process and unloading time for subsequent processes.)
5. Repeated material handling and transportation.
6. Higher equipment cost i.e furnace for subsequent heat treatment processes.
7.Higher environmental impact i.e fossil fuel depletion, emission of gases.
3

Summary of the Invention:
The present invention comprises of the chemical composition of C-Mn type steel which is optimized to produce heat treatment response of achieving desired microstructure in minimum top 10% of the surface layer without need for micro alloy addition . Thus, the low cost steel grade composition and its integrated processing is developed which produces required microstructural effect in minimum top 10% of surface layer suitable for automotive and general engineering applications.
The main objective of the present invention is to manufacture low cost automotive and general engineering forged components where the required strength levels are achieved in top minimum 10% of surface layer to withstand the fatigue load condition.
The purpose of the present invention is to utilise residual heat of forging to integrate hot forming process with subsequent heat treatment process for controlled transformation and thereby eliminating need for subsequent hardening and tempering process.
Advantages of the Present Invention:
1. No separate hardening and tempering processes are required after hot forging to
produce desired
strength levels.
2. The required strength level is achieved in top minimum 10% of surface layer by tailoring low cost alloy.
3. Large amount of thermal energy is saved as different repeated heating processes are eliminated.
4. The cycle time is reduced as reheating processes are eliminated.
5. Cost of the new integrated set up is much lower than furnace cost as it uses the residual heat and no separate heating coils are required.
4

Description of the Present Invention:
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter.
The steel forging for automotive and general engineering applications are made from different types of plain carbon and alloy steels and are quenched and tempered after hot forging process to three different types of strength levels (viz. 660-790 MPa, 820-980 MPa, 850-1000 MPa). As the fatigue failure initiate at the surface, in reality , the above strength levels are required to be present in minimum top 10% of surface layer. This change in concept of component design is used to develop low cost steel chemistries suitable to produce required strengths in top minimum 10% of the layer by integrating hot forging processes and its subsequent heat treatment thereby the residual heat of forging can be saved.
The forgings are forged at higher side of the recommended temperature so that advantage of higher austenizing temperature is achieved to get enhanced hardenability and cooling starts from the temperature above 900° C. This helps to get required strength in top 10% of the outer layer.
The steel alloy compositions are based on low cost consideration by use of varying carbon and manganese content for the required strength levels. For different part weight and section thickness these composition ranges and the corresponding cooling rates can be varied to get desired results. Also small addition like Cr (0.15 - 0.30%) and Mo (0.08-0.15%) can be done to get required results.
5

Based on the chemistry range chosen, the required minimum cooling rate can be decided using theoretical calculations to predict time - temperature transformation curves.
The alloy chemistries and the min cooling rate to get three types of strength levels are shown in the following table.

Strength level(MPa) Approx.Equivalent Hardness (BHN) Chemistry Range* Forging & triming operaton. At 10 & 11. Cooling Rate at 12.
660-790 190-230 %C= 0.35-0.55 %Mn= 0.6-1.25 Temp, range 1200 to 900 deg Cooling rate of 30-350Deg.C/minute. (from still air toforced airincluding additionof mist).
820-950 241-285 %C= 0.35-0.55 %Mn= 1.0-1.65
850-100 248-302 %C= 0.38-0.55 %Mn= 1.0-1.65
* These are predominant chemistry limits. The steel generally contains other elements like Si, S, P, Al, N, Cr, Ni, Mo, V and the limits for these can be as per national and international standards and steel making practices related to forging quality steels.
Various automotive components like crankshaft, suspension , knuckles , connecting rods, wheel bearing spindles, levers, companion flange, axle shafts, etc were processed by above methods and validated by actual testing for satisfactory performance.
The present invention is illustrated in figure 2 of the accompanying drawing.
Figure 2 shows the schematic graphical representation of the new method of Integrated heating i.e forging+ different heat treatment processes. (9) indicates heating upto 1200 deg C, (10) indicates forging start at 1200 deg C, (11) indicates forging finish
6

& triming operation at temp, range of 1200 to 900 deg C , (12) indicates cooling from temperature range of 1200 to 900 deg. C to temperature range of 300 deg C to ambient temp, by using cooling rate of 30 to 350 deg. C per minute.

Dated this 26m of May, 2006.

M..D.BHATE AGENT FOR THE APPLICANT

7

Documents:

817-mum-2006-abstract(22-5-2007).pdf

817-MUM-2006-ABSTRACT(28-11-2011).pdf

817-MUM-2006-ABSTRACT(GRANTED)-(29-12-2011).pdf

817-mum-2006-abstract1.jpg

817-mum-2006-claims(22-5-2007).pdf

817-MUM-2006-CLAIMS(AMENDED)-(28-1-2011).pdf

817-MUM-2006-CLAIMS(AMENDED)-(28-11-2011).pdf

817-MUM-2006-CLAIMS(GRANTED)-(29-12-2011).pdf

817-mum-2006-correspondance-recieved.pdf

817-mum-2006-correspondence(7-9-2007).pdf

817-MUM-2006-CORRESPONDENCE(IPO)-(2-1-2012).pdf

817-mum-2006-correspondence(ipo)-(28-1-2010).pdf

817-mum-2006-description (complete).pdf

817-mum-2006-description (provisional).doc

817-mum-2006-description(complete)-(22-5-2007).pdf

817-MUM-2006-DESCRIPTION(GRANTED)-(29-12-2011).pdf

817-MUM-2006-DESCRIPTION(PROVISIONAL)-(29-5-2006).pdf

817-mum-2006-drawing(22-5-2007).pdf

817-mum-2006-drawing(29-5-2006).pdf

817-MUM-2006-DRAWING(GRANTED)-(29-12-2011).pdf

817-MUM-2006-FORM 1(28-11-2011).pdf

817-MUM-2006-FORM 13(28-11-2011)-1.pdf

817-MUM-2006-FORM 13(28-11-2011).pdf

817-MUM-2006-FORM 13-(28-11-2011).pdf

817-MUM-2006-FORM 18(7-9-2007).pdf

817-mum-2006-form 2(22-5-2007).pdf

817-MUM-2006-FORM 2(GRANTED)-(29-12-2011).pdf

817-MUM-2006-FORM 2(PROVISIONAL)-(29-5-2006).pdf

817-mum-2006-form 2(title page)-(22-5-2007).pdf

817-MUM-2006-FORM 2(TITLE PAGE)-(28-1-2011).pdf

817-MUM-2006-FORM 2(TITLE PAGE)-(28-11-2011).pdf

817-MUM-2006-FORM 2(TITLE PAGE)-(GRANTED)-(29-12-2011).pdf

817-MUM-2006-FORM 2(TITLE PAGE)-(PROVISIONAL)-(29-5-2006).pdf

817-mum-2006-form 3(22-5-2007).pdf

817-MUM-2006-FORM 3(28-1-2011).pdf

817-mum-2006-form 5(22-5-2007).pdf

817-MUM-2006-FORM 9(21-6-2007).pdf

817-mum-2006-form-1.pdf

817-mum-2006-form-2.doc

817-mum-2006-form-2.pdf

817-mum-2006-form-26.pdf

817-MUM-2006-MARKED COPY(28-11-2011).pdf

817-MUM-2006-REPLY TO EXAMINATION REPORT(28-1-2011).pdf

817-MUM-2006-REPLY TO HEARING(28-11-2011).pdf

817-MUM-2006-SPECIFICATION(AMENDED)-(28-1-2011).pdf

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Patent Number

250355

Indian Patent Application Number

817/MUM/2006

PG Journal Number

52/2011

Publication Date

30-Dec-2011

Grant Date

29-Dec-2011

Date of Filing

29-May-2006

Name of Patentee

MAHINDRA & MAHINDRA LTD.

Applicant Address

R&D Centre, Auto Sector 89, M.I.D.C., Nashik-

Inventors:

#	Inventor's Name	Inventor's Address
1	PONKSHE, Shripadraj Ramchandra	C/o Mahindra & Mahindra Ltd., R&D Centre, Auto Sector 89, M.I.D.C., Nashik-422007.
2	PARAB, Pratap Eknath	C/o Mahindra & Mahindra Ltd., R&D Centre, Auto Sector 89, M.I.D.C., Nashik-422007.
3	PANSE, Sudhir Shridhar	C/o Mahindra & Mahindra Ltd., R&D Centre, Auto Sector 89, M.I.D.C., Nashik-422007.

PCT International Classification Number

C21D9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA