Claims:1. A quenching oil composition comprising:
(a) an API Group I base oil or an API Group II base oil or a combination of Group I, Group II base oils; and
(b) an additive composition comprising:
(i) 2-5 wt.% of an ashless hydrocarbyl substituted succinic acid derivative based wetting agent;
(ii) 2-5 wt.% of a hardening agent; and
(iii) 0.2-0.5 wt.% of an antioxidant,
wherein the wetting agent and the hardening agent are present in a weight ratio of 1:1.

2. The quenching oil composition as claimed in claim 1, wherein the ashless hydrocarbyl substituted succinic acid derivative based wetting agent is present preferably in a range of 2-3 wt.% of the quenching oil composition.

3. The quenching oil composition as claimed in claim 1, wherein the hardening agent is present preferably in a range of 2-3 wt.% of the quenching oil composition.

4. The quenching oil composition as claimed in claim 1, wherein molecular weight of the ashless hydrocarbyl substituted succinic acid derivative is present in a range of 700 to 1500 g/mol.

5. The quenching oil composition as claimed in claim 1, wherein the antioxidant comprises a combination of a hindered phenol and an amine-based antioxidant.

6. The quenching oil composition as claimed in claim 1, wherein the hardening agent comprises alkali metals or alkaline earth metals.

7. The quenching oil composition as claimed in claim 6, wherein the hardening agent comprises alkaline earth metals in a range of 2-5 wt.%, preferably in a range of 2-3 wt.%, of the quenching oil composition.

8. The quenching oil composition as claimed in claim 7, wherein the alkaline earth metals comprise calcium and barium.

9. The quenching oil composition as claimed in claim 1, wherein the wetting agent and the hardening agent in 1:1 weight ratio are present in a range of 4-10 wt.%, preferably in a range of 4-6 wt.%, of the quenching oil composition.

10. The quenching oil composition as claimed in claim 1, wherein nitrogen content of the wetting agent is present in a range of 1 to 5 wt.%.

11. A process for preparation of a quenching oil composition, the process comprising:
(a) feeding API Group-I base oil or API Group-II base oil or a combination of Group-I, Group-II base oils into a blending kettle;
(b) heating the base oil while stirring, till temperature of the base oil reaches to a range of 45-55°C;
(c) adding an additive composition and continuously stirring for a period of at least 60 minutes by maintaining the temperature at a range of 50-55°C; and
(d) stopping the heating process once a homogenous final product is obtained.

12. The process as claimed in claim 11, wherein the additive composition of step (c) comprises:
(i) 2-5 wt.% of an ashless hydrocarbyl substituted succinic acid derivative based wetting agent;
(ii) 2-5 wt.% of a hardening agent; and
(iii) 0.2-0.5 wt.% of an antioxidant,
wherein the wetting agent and the hardening agent are present in a weight ratio of 1:1. , Description:FIELD OF THE INVENTION:
[001] The invention relates to the development of quenching oil composition with improved cooling characteristics in terms of enhanced cooling rate and optimum hardening power. The composition of the quenching oil comprises an additive composition, comprising a wetting agent, a hardening agent and an antioxidant, in combination with API Group-I base oil, API Group-II base oil or a combination of Group I, Group II base oils. The improved performance of the quenching oil is observed for the synergistic combination of wetting agent and hardening agent present in a weight ratio of 1:1. The wetting agent is present in a range of 2-5 wt.%, preferably in a range of 2-3 wt.%; and the hardening agent is present in a range of 2-5 wt.%, preferably in a range of 2-3 wt.% of the quenching oil composition. Particularly, the invention relates to the development of quenching oil composition suitable to get enhanced cooling rate with optimum hardening power in medium to high viscosity quenching oils. The quenching oil composition exhibits excellent thermo-oxidation stability and low soot forming tendency for ensured surface cleaning of the finished components.

BACKGROUND OF THE INVENTION:
[002] Quenching oils have major application in heat treatment cell in the manufacturing industries, where the controlled heating and cooling is done in order to obtain desired structure sensitive properties in terms of hardness, strength, and ductility. Desired properties are obtained as a result of phase transformation on controlled heating and cooling. Heat treatment of steels is represented graphically by Fe-C phase diagram. The phases present in Iron (Fe)-Carbon (C) phase diagram are a, d ferrite phase, ? austenite phase, molten alloy and cementite. Fe exists in body-centered cubic (BCC) structure in a, d ferrite phase (max. solubility of C in a phase: 0.022%) and face-centered cubic (FCC) structure in ? austenite phase (max. solubility of C in ? phase: 2%). Although austenite phase exists at high temperature, the rate at which steels are cooled from austenite phase and grain size of parent austenite has profound influence on microstructure properties of steel at room temperature. When the steel from the ? phase is cooled, it slowly reverts back to low temperature arrangement a phase. Since the solubility of carbon in a phase is very less, excess of the carbon ejects out of crystal lattice to revert back to low temperature arrangement. Depending upon the cooling conditions, the rate at which solute particles eject out of crystal lattice vary resulting in different microstructures such as pearlite structure (composed of lamellar structure of alternate platelet ferrite and cementite) under slow cooling conditions, bainite structure (composed of non-lamellar structure of platelet ferrite and carbide precipitate) under medium cooling condition and martensite transformation (distorted body centered tetragonal, hard and brittle structure) under fast cooling condition. Steels must be cooled sufficiently fast in the region of 500-600°C in order to avoid the formation of pearlite structure (soft constituents) for obtaining maximum hardness and strength. Different cooling conditions to obtain desired properties could be achieved by carefully tailoring the quenching oil composition.

[003] Quenching process in quenching medium occurs mainly in three stages namely vapor phase, nucleate boiling stage and convection stage. Cooling characteristics of quenching oils in the form of cooling curve is obtained as per ASTM D6200 method. Important parameters obtained from cooling curve are Tvp (transition from vapor phase to nucleate boiling stage), maximum cooling rate, Tcp (transition temperature from nucleate boiling stage to convection phase), cooling rate at 300°C and hardening power. Shorter the duration of vapor phase, higher the cooling rate in the range of 500-600°C and lower the Tcp, higher the hardening power. Duration of vapor phase, nucleate boiling stage and cooling rate at 300°C depends upon the quenching oil composition, nature of wetting agents, type of base oil, its viscosity, molecular weight, distillation range, etc.

[004] Quenchants are classified as gas quenchants, aqueous quenchants, bio quenchants and mineral oil-based quenchants. Mineral oil based quenchants are mainly composed of highly refined base oils with good thermo-oxidative stability at operating temperature, accelerators, wetting agents, and antioxidants to get the desired cooling characteristics and service life. When the phenomenon of quenching process occurs, generally the surface cools more rapidly than the center resulting in generation of internal stresses and distortion. Internal stresses could be reduced
• by conducting the quenching process at operating temperature close to the temperature at which the formation of martensite will start (Ms);
• by the use of high-speed quenching oils for uniform and better hardening profile.
High-speed quenching oils with enhanced cooling rate are used for hardening of low alloy steels. Enhanced cooling rate and optimum hardening are desirable cooling characteristics in heat treatment process and could be obtained by carefully selecting the appropriate base oil or their combinations and optimized dosage of wetting agents, hardening agents, and their combinations.

[005] Chinese application CN102382952A by Shanghai Jinhai Special Lubricating Oil Factory describes superspeed quenching oil composition comprised of refined base oil 85-95, composite cooling accelerant composed of polyisobutene and machine oil at wt. ratio of 50:50 2-10, brightener 1-5, composite antirust agent composed of barium petroleum sulphonate and machine oil at wt. ratio of 40: 60 1-3 and surfactant (Span-80) 1-2 wt.%

[006] Chinese patent CN102212662B by Shanghai Petrofer Special Lubricant Co. Ltd describes quenching oil composition with ultrahigh cooling speed, good thermal oxidative stability, high and uniform surface hardness comprised (by wt.%) of refined mineral oil (kinematic viscosity: 6-9 mm2/s at 40°C) 80-97, cooling accelerant (mixture of phenolic oleoresin and polybutene) 1-10, antioxidant (di-Ph amine alkylate) 1-5 and anionic surfactant (sodium alkane sulphonate) 1-6.

[007] Chinese patent CN102140570B by Changzhou Longbang Lubrication Technology Co. Ltd describes energy-saving and environment-friendly quenching oil composition for mechanical bearings with improve quality comprises (by wt.%) of base oil (150N or 500N class II base oil) 79-98.45, cooling accelerant (polyisobutene with a mol. wt. of 680-3400) 1-8, brightening agent (imidazoline oleate) 0.05-5 and antioxidant (phenol ester with high mol. wt.) 0.5-8. With the described quenching oil composition deformation amount is reduced by 30% compared to standard value.

[008] Chinese patent CN102605149B by Austria (Xiamen) Bearing Co. Ltd describes quenching oil composition for heat treatment comprising machine oil, calcium petroleum sulphonate, 2,6-di-tert-butyl-p-cresol, imidazoline oleate and polyisobutylene-bis-succinimide with reduced deformation of bearing ring, eliminate post finish processing and reduced cost.

[009] Japanese patent JP5490434B2 by Idemitsu Kosan Co. Ltd and US patent US3866603 by Shell Oil Co. describes quenching oil composition with high cooling performance comprising base oil having kinematic viscosity at 40°C 4-20 mm2/s and alkenyl or alkyl succinimides.

[0010] Chinese application CN101029349A by Nanjing University of Aeronautics and Astronautics describes composite additive for quenching oil composed of rare earth sulphonate oil-soluble additive 70-80, 2,6-di-tert-butyl-p-cresol as antioxidant 10-15, succinimide dithiophosphate as anti-aging agent 7-12.5 and succinimide as brightener 0-5.

[0011] WO publication WO2006122585A1 by Shell Internationale Research Maatschappij B.V. describes quenching oil composition comprising one or more additives and a saturated base oil having a kinematic viscosity at 100°C "K" expressed in centistokes and a viscosity index "I", wherein I is >120 and K >2 cSt. The composition consists of 95% of base oil and 5% of a std. additive package consisting of a high molecular weight succinic acid additive, a high molecular sodium sulphonate additive, a calcium alkyl salicylate, and a silicon-based antifoam additive.

[0012] PCT Int. Appl. (2003), WO2003052145A1, WO2003052146A1, US20050039832, and EP1456420 by Lubrizol Corporation describes quenching oil suitable for industrial quench hardening of steel articles based on the mineral and/or synthetic oil having kinematic viscosity at 40°C of 40-210 Saybolt Universal Seconds, and a satd. content of 80-100%, 0.2-10% by wt. of aliphatic polyolefin having av. mol. wt. of 300-10,000, preferably from isobutylene; 0.2-10% of metal salts of hydrocarbyl-substituted phenols, salicylic acid, carboxylic acids, and/or sulphonic acids, and/or alkaline-earth metal salts of hydrocarbyl substituted saligenin derivatives; 0.1-5% of optional hydrocarbyl-substituted succinic esters, amides, ester-amides, imides, amine salts, acid-esters, acid-amides ester-amine salts, amide-amine-salts and/or acid-amine salts. Described composition showed high cooling rate as well as decreased cooling rate at <300°C to prevent warping of complex articles.

[0013] US patent US6239082B1 by ExxonMobil Research and Engineering Co. describes quenching oil composition for high-speed cooling of heated metals comprised of natural or synthetic base oils having a minimum flash point of 120°C and a combination of poly(iso)alkylene and poly(iso)alkylene succinic anhydride or succinic acid. Described quenching oil composition results in improved metallurgical consistency, machinability and reduces residue on quenched metal parts.

[0014] US patent US3866603A by Shell Oil Co. describes high speed quenching oil contained mineral oil plus 5% of bis(polyisobutenyl)succinimide of tetraethylenepentamine and polished Ni balls quenched for 11.4 sec in the medium from 1625 F and disclosed a high surface brightness.

[0015] Polish application PL192434B1 by Inst. Technologii Nafty describes quenching oil composition for metal heat treatment comprising: (1) highly refined petroleum oil obtained by petroleum vacuum distillation and having kinematic viscosity of 3.5-12.0 mm2/s at 100°C 40-98, (2) highly refined petroleum oil obtained from petroleum residues with asphalt phase removed using propane and having kinematic viscosity of 25-38 mm2/s at 100°C 0-50, (3) polyisobutylenesuccinimide 40-70, (4) overbase calcium alkyl salicylate 30-60, (5) oxidation inhibitor, preferably di(2,6-diisobutylphenyl) methane 0-5 wt. parts.

[0016] Patent publications US20030096714A1, WO2003008653A1, JP2001192689A and JP2000045018A by Idemitsu Kosan Co. Ltd describes heat treatment of metal gears comprised of hydrocarbon base oil with kinematic viscosity 5-40 mm2/s at 100°C, 0.01-5 wt.% of a phosphate ester, 0.5-10 wt.% of an alkenyl succinimide (optionally borated) and 0.5-10 wt.% of alkaline earth salicylates, phenates and sulphonates with good quench hardenability, brightness, and rust prevention characteristics.

[0017] Patent publications JP07070632A, US5250122A and US5376186A by Idemitsu Kosan Co. Ltd describes heat treatment oil composition comprised of =1 mineral oils or synthetic oils of S content =300 ppm added with S or S compounds to make the total S content 3-1000 ppm and additives of =1 of sulphonic acid alkaline earth salts, phenol alkaline earth salts, alkenyl succinic acid derivative, aliphatic acids, aliphatic acid derivative, phenolic antioxidants, and amine antioxidants. The said composition is suitable for quenching or tempering of precision steel articles (esp. automotive gears) and promotes surface brightness without distortion.

[0018] Japanese application JP61268794A by Idemitsu Kosan Co. Ltd describes heat treatment oil compositions for bearing races and gears, comprise lubricating base oils, fatty acids, fatty acid monomers, compounds. selected from succinic acid (I), alkyl succinic acid, and/or alkenyl succinic acid, and optionally waxes. A test piece (SUJ-2) was quench-hardened at 800 °C using an oil composition containing paraffin oil 98, coconut oil fatty acids 0.75, oleic acid (II) 0.25, and I 1.0% to give a product with excellent brightness both on the surface and at the edge, compared with excellent brightness on the surface but brown at the edge using a similar composition without I and II.

[0019] JP52004508A describes quenching oil composition for bright quenching of steel comprised of solvent-refined and hydro refined lubricating base oil (viscosity 10-600 cSt at 37.8°C and containing <0.05% total S) is mixed with 10-1000 ppm (as N) oil-sol. alkenyl succinimide to obtain a quenching oil for steel. Thus, base oil (sp. gr. 0.864, flash point 204°C, viscosity 23.10 cSt at 37.8°C, viscosity index 106 and S content 0.03%) 96.5, alkenyl succinimide-type additive 1.0, and polybutene [9003-29-6] (average molecular weight 2500) 2.5 parts were combined to give a steel-quenching oil having sp. gr. 0.865, flash point 208°, viscosity 30.97 cSt at 37.8°C, viscosity index 125, and S content 0.03%. When Cr steel was heated 10 min under N2 at 850°C and quenched in the oil, the specimen had high brightness for a long period.

[0020] US patent US3925113A by Shell Oil Co. describes quenching oil composition composed of base oil, ashless detergent (mono(polyisobutenyl)succinimide of tetraethylenepentamine) 5% by weight. A typical base oil is HVI 100 neutral mineral oil 78, HVI 150 bright stock 7, and a low-viscosity mineral oil (40-7 SUS at 100°F) vol.% containing loriol antioxidant (2,6-di-tert-butyl-4-methylphenol) 0.25 vol.%. The mineral base oil preferably contains 0.005-0.04 wt.% vicinal dihydrocarbyl-substituted 2-mercaptothiazole.

[0021] SU1247423A1 describes quenching oil comprised of alkenyl succinamide (mol. wt. 300-10,000) 2-5, polymethylsiloxane 0.002-0.003, Ionol 0.3-0.5% and purified distilled oil having viscosity of 18-20 cSt at 50°C the balance.

[0022] JP61015913A and EP113157A1 described quenching oils for hardening of metals consists of mineral oils as a major component, ashless dispersants of polyol-polyamide succinic acid derivative 0.3-7.5, detergents of alkali or alkaline earth metal alkyl-or aryl sulphonates or -phenates 0.02-2.5 and ashless antioxidants 0.01-2.0 wt.%. Thus, a quenching oil mixture was manufactured by mixing mineral oil 36, polyisobutenyl succinimide [average component tetraethylenepentamine bis(polyisobutenylsuccinimide)] 48, Ca phosphonate phenate 6, and di(nonylphenyl)amine 10 wt.%. By addn. of the additives to the mineral oil, the quenching rate and amt. of pptn. (panel Coker test) were changed from 82 to 45°/s and from 355 to 82 mg, respectively.

[0023] JP60004597A describes quenching oil composition for hardening and tempering of steel comprised of reaction product of boric acid and an imide of polybutenyl succinate and tetraethylenepentamine, paraffinic mineral oil 87% lubricity and 84% reflection after hardening SUJ-2 [12725-40-5], compared to 72 and 65 when using the mineral oil solely.

[0024] EP113157A1 describes oil-based quenching fluids for processing ferrous metals comprising of polyisobutenylsuccinimide-terminated polyethylenepolyamine, Ca phosphonate phenate, hindered antioxidant. Thus, a concentrate (to be mixed at a 2.5 wt.% level in a hydrocarbon oil) contained an oil 36, above succinimide 48, a Ca phosphonate phenate 6 and antioxidant 10 wt.%.

[0025] JP05279730A by Nippon Oil Co. Ltd describes composition comprised of mineral oils 100, ethylene-a-olefin copolymers 0.01-20, and alkali earth metal salts of alkyl salicylic acids 0.05-5.0 parts. The composition is stable against oxidation and maintain high cooling rate after prolonged use.

[0026] CS 267032 B1 19900212 described quenching oil composition with improved surface quality comprised of 0.03-10% reaction product (I) of B, alkenylsuccinic anhydride, and polyethylenepolyamine (R = isobutylene residue with mol. wt. of 700-1400; x = 2-5). The typical quenching bath for carburized Cr-Ni steels consists of I 0.4, Ca petroleum sulphonate 4%, and bearing oil as the balance.

[0027] EP0113157 by Edwin Cooper & Co. Ltd described improved quench oil for use in heat treating ferro-metals comprising a major amount of mineral oil containing (a) an ashless dispersant (e.g. alkenyl succinimide, alkenyl succinic ester, alkenyl succinic ester-amide or alkylphenolformaldehyde-amine Mannich condensate), (b) an alkaline earth or an alkali metal detergent (e.g. calcium aryl sulphonate, calcium phosphonate phenate), and (c) an ashless antioxidant (e.g. alkylated diphenylamine, sterically hindered phenols or sulphurized alkylphenols).

[0028] Chinese application CN101062880A by Sinopec Beijing Research Institute of Chemical Industry and China Petroleum and Chemical Corp. describes composite additive for quenching oil comprised of polymn. inhibitor, dispersant, and metal deactivator at wt. ratio of 0.1-10:1:0.1-10. The polymn. inhibitor consists of phenols antioxidant and amines antioxidant at wt. ratio of 1:0.2-5. The dispersant is one or more of polyalkene succinimide and polyalkene succinimide P-containing derivatives. The metal deactivator is one or more of poly-alkyl siloxanes, alkyl benzene sulphonic acid amine salt and alkyl naphthalene sulphonic acid amine salt.

[0029] Therefore, keeping in view of the above, a developmental program was initiated by the inventors of the present invention at the laboratory level. Different combinations of performance additives were used in the development of high-speed quenching oil compositions with optimum hardening power and are described in the present invention. The present invention discloses the following technical advancements over the prior art:
• Desired performance in terms of enhanced cooling rate (CR) (93-113oC/sec) and optimum hardening power (HP) (800-1300) obtained with synergistic combination of ashless hydrocarbyl substituted succinic acid derivative based wetting agent and hardening agent such as sulphonates of alkali earth metals at optimized dosage. The sulphonates of alkali earth metals comprise neutral calcium sulphonate.
• Hardening agent contains up to 2-5 wt.% alkaline earth metals, preferably in a range of 2-3 wt.% for desired hardness. Wetting agent and hardening agent are present in 1:1 weight ratio at a concentration range of 4-10 wt.%, preferably in a range of 4-6 wt.% of the quenching oil composition for desired performance.

SUMMARY OF THE INVENTION:
[0030] The present invention discloses a novel quenching oil composition comprising an additive composition further comprising (a) an ashless hydrocarbyl substituted succinic acid derivative based wetting agent (b) a hardening agent and (c) an antioxidant; in combination with API Group-I base oil, premium quality severely hydrotreated/hydroprocessed API Group-II base oil or a combination of Group I, Group II base oils in a viscosity range of 15-60 cSt at 40°C.

TECHNICAL ADVANTAGES OF THE INVENTION:
[0031] The present invention has the following advantages over the cited prior arts:
(i) enhanced cooling rate (CR) (93-113oC/sec) and optimum hardening power (HP) (800-1300);
(ii) novel component based additive system for quenching of alloy steel automotive components; and
(iii) excellent thermo-oxidative stability, and low soot forming tendency for ensured surface cleaning of finished product.

OBJECTIVES OF THE INVENTION:
[0032] It is a primary objective of the present invention to provide a novel quenching oil composition comprising an API Group I base oil or an API Group II base oil or a combination of Group I, Group II base oils; and an additive composition comprising (a) an ashless hydrocarbyl substituted succinic acid derivative based wetting agent (b) a hardening agent and (c) an antioxidant.

[0033] It is a further objective of the present invention to provide an additive composition comprised of equal weight ratio of 1:1 of synergistic combination of wetting agent and hardening agent at optimized dosage. The synergistic combination results in enhanced cooling rates with optimum hardening power.

[0034] It is another objective of the present invention to provide a quenching oil composition suitable for quenching of low alloy low carbon steel for automotive components manufacturing industries (gears, shafts, splines etc.).

[0035] Yet another objective of the invention is to provide a process for preparation of a quenching oil composition.

ABBREVIATIONS:
BCC: Body-centered cubic
FCC: Face-centered cubic
CR: Cooling rate
HP: Hardening power
PIB: Poly isobutylene TBN: Total base number
WA: Wetting agent
AO: Antioxidant

DETAILED DESCRIPTION OF THE INVENTION:
[0036] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps of the process, features of the system, referred to or indicated in this specification, individually or collectively and any and all combinations of any or more of such steps or features.

Definitions
[0037] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have their meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

[0038] The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0039] The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.

[0040] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0041] The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.

[0042] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0043] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products and processes are clearly within the scope of the disclosure, as described herein.

[0044] The present invention relates to a novel quenching oil composition developed after optimizing physico-chemical, thermo-oxidative stability, and cooling and hardening characteristics. The composition of the quenching oil comprises an additive composition in combination of API Group-I base oil, premium quality severely hydrotreated/hydroprocessed API Group-II base oil or a combination of Group I, Group II base oils in a viscosity range of 15-60 cSt at 40°C.

[0045] In another embodiment of the invention, the additive composition for use in the quenching oil composition comprises a) an ashless hydrocarbyl substituted succinic acid derivative based wetting agent for enhanced cooling rate, b) a hardening agent, and c) an antioxidant. The additive composition comprises (a) 2-5 wt.% of an ashless hydrocarbyl substituted succinic acid derivative based wetting agent; (b) 2-5 wt.% of a hardening agent, and (c) 0.2-0.5 wt.% of an antioxidant, wherein the wetting agent and the hardening agent are present in a weight ratio of 1:1.

[0046] In another embodiment of the invention, the ashless hydrocarbyl substituted succinic acid derivative based wetting agent is present preferably in a range of 2-3 wt.% of the quenching oil composition. The hardening agent is present preferably in a range of 2-3 wt.% of the quenching oil composition.

[0047] In yet another embodiment, the ashless succinic acid derivative based wetting agent comprises ashless hydrocarbyl substituted succinic acid derivatives such as esters, amides, ester-amides, imides, amine salts, acid esters, acid-amides, ester-amine salts, amide-amine salts and acid amine salts. The dosage of the wetting agent is in a range of 2-5 wt.%, and preferably in a range of 2-3 wt.%, of the quenching oil composition. Other wetting agents evaluated during this study are polyisobutylene-based polymer, calcium alkyl salicylate, self emulsifiable ester such as water immiscible fully esterified C1-C9 alkyl ester of trimer acid. The molecular weight of the hydrocarbyl substituted succinic acid derivative is in a range of 700 to 1500 g/mol. Further, nitrogen content of the wetting agent is present in a range of 1 to 5 wt.%. Molecular weight and nitrogen content are few of the specific characteristic properties of wetting agent, which are optimized for enhanced performance.

[0048] In another embodiment, the antioxidant comprises a combination of a hindered phenol and an amine-based antioxidant. The preferred range of antioxidant is 0.2-0.5 wt.% of the quenching oil composition.

[0049] In another embodiment, the hardening agent used in this invention comprises alkali metals or alkaline earth metals. Examples of preferred alkali metals include Potassium (K) and Sodium (Na), and alkaline earth metals include Calcium (Ca) and Barium (Ba). The hardening agent is selected from a group comprising of sulphonates of calcium and barium. It comprises neutral calcium sulphonates such as low total base number (TBN) calcium sulphonate, and high total base number (TBN) calcium sulphonate preferably low TBN calcium sulphonate. The dosage of the hardening agent is present in a range of 2-5 wt.%, preferably in a range of 2-3 wt.%, of the quenching oil composition.

[0050] In yet another embodiment, the combination of the wetting agent and the hardening agent is present in a range of 4-10 wt.%, preferably in a range of 4-6 wt.%, in 1:1 weight ratio of the quenching oil composition.

[0051] In another embodiment of the invention, the quenching oil composition provides enhanced cooling rate (CR) in a range of 93-113°C/sec and optimum hardening power (HP) in a range of 800-1300.

[0052] In another embodiment, the present invention discloses a process for preparation of a quenching oil composition, wherein the quenching oil composition comprises base oils and additive composition.

[0053] In yet another embodiment of the invention, the present invention provides a process for preparation of a quenching oil composition, the process comprising: (a) feeding API Group-I base oil or API Group-II base oil or a combination of Group-I, Group-II base oils into a blending kettle; (b) heating the base oil while stirring till temperature of the base oil reaches to a range of 45-55°C; (c) adding an additive composition and continuously stirring for a period of at least 60 minutes by maintaining the temperature at a range of 50-55°C; and (d) stopping the heating process once a homogenous final product is obtained.

EXAMPLES:
[0054] Having described the basic aspects of the present invention, the following non-limiting examples illustrate specific embodiments thereof. Those skilled in the art will appreciate that many modifications may be made in the invention without changing the essence of the invention.

Experimental blend preparation and testing:
[0055] The chosen additives are mixed in selected base oils at an appropriate temperature of 45-55°C, so that mixture gets clear and homogeneous. A quenching oil of said composition is described in the below experiments.

[0056] Several candidate blends of aforesaid additives and base stocks as disclosed in Tables 1-8, were prepared in the viscosity ranges from 15-60 cSt at 40°C and evaluated in laboratory for critical properties like thermo-oxidative characteristics as per IP-48 and cooling curve characteristics as per ASTM D 6200.

Effect of different wetting agents on the cooling characteristics:
[0057] The effects of wetting agent 1 (WA1) and wetting agent 2 (WA2) on the cooling characteristics, Max CR and hardening power (HP) as per ASTM D 6200 in presence of Group-I/Group-II base oil, at viscosity of 15/30/40/50/60 cSt, and antioxidant (AO) of 0.3% is disclosed in Table 1. Green color represent the data with Group-1 base oil and red color represents the data with Group II base oils.

Wetting agent 1(WA1)
Poly isobutylene (PIB) Succinimide Wetting agent 2 (WA2)
Polymer based Poly isobutylene (PIB)
Dosage (%) 0.5 1 2 3 4 5 0.5 1 2 3
Max CR, oC/s
66-79/ 71-85 68-80/ 73-85 93-102/ 98-104 95-105/ 100-106 95-105/ 100-106 95-105/ 100-106 60-65/ 63-67 62-65/ 63-67 62-65/ 63-67 62-65/ 63-67
Hardening Power (HP)
400-450/ 430-500 400-500/ 440-550 500-600/ 520-650 500-620/ 530-650 500-620/ 530-650 500-620/ 530-650 200-250/ 300-350 200-250/ 300-350 200-250/ 300-350 200-250/ 300-350
Table 1: Effect of WA1 and WA2 on Max CR and HP

[0058] The effects of wetting agent 3 (WA3) and wetting agent 4 (WA4) on the cooling characteristics, Max CR and hardening power (HP) as per ASTM D 6200 in presence of (Group-I / Group-II base oil, at viscosity of (15/30/40/50/60 cSt), and antioxidant (AO): of 0.3%) is disclosed in Table 2. Green color represent the data with Group-1 base oil and red color represents the data with Group II base oils.

Wetting agent 3 (WA3)
Low Total Base Number (TBN) Ca Sulphonate
Wetting agent 4 (WA4)
High Total Base Number (TBN) Ca Sulphonate
Dosage (%) 0.5 1 2 3 0.5 1 2 3
Max CR, oC/s 60-65/ 63-70 65-68/ 66-70 68-70/ 70-75 70-75/ 70-75 70-75/ 70-75 75-80/ 75-80 75-85/ 78-89 75-85/ 78-89
Hardening Power (HP) 300-350/ 320-350 320-360/ 330-360 350-400/ 360-420 350-400/ 360-420 620-640/ 630-680 630-650/ 650-680 650-800/ 670-800 650-800/ 670-800
Table 2: Effect of WA3 and WA4 on Max CR and HP

[0059] The effects of wetting agent 5 (WA5) and wetting agent 6 (WA6) on the cooling characteristics, Max CR and hardening power (HP) as per ASTM D 6200 in presence of (Group-I / Group-II base oil, at viscosity of (15/30/40/50/60 cSt), and antioxidant (AO): of 0.3%) is disclosed in Table 3. Green color represent the data with Group-1 base oil and red color represents the data with Group II base oils.

Wetting agent 5 (WA5)
Calcium Alkyl Salicylate) Wetting agent 6 (WA6)
Self emulsifiable ester,
Water immiscible fully esterified C1 to C9 alkyl ester of a trimer acid
Dosage (%) 0.5 1 2 3 4 5 0.5 1 2 3 4 5
Max CR, oC/s 65-70/ 65-70 70-75/ 70-75 70-75/ 70-80 75-80/ 72-83 75-80/ 72-83 75-80/ 72-83 60-65/ 61-66 60-65/ 61-66 60-68/ 62-68 60-70/ 62-72 60-70/ 62-72 60-75/ 62-75
Harde-ning Power (HP) 620-640/ 630-680 630-650/ 650-680 650-800/ 670-800 650-800/ 670-800 650-800/ 670-800 650-800/ 670-800 200-250/ 220-280 220-250/ 220-280 250-280/ 280-320 280-320/ 300-350 280-350/ 300-350 280-350/ 300-350
Table 3: Effect of WA5 and WA6 on Max CR and HP

[0060] The following remarks were observed on the cooling characteristics, i.e., Max CR and hardening power (HP):
• Poly isobutylene (PIB) succinimide (WA1) of tetraethylene tetraamine at the minimum dosage of 2% in Group-I/Group-II base oil of 15-60 cSt results in Max CR = 93oC/s and hardening power up to 650. Therefore, maximum cooling is achieved, but hardness is not achieved.

[0061] Furthermore, different combinations of poly isobutylene (PIB) succinimide with other additives in different ratios were tried to achieve optimum hardness = 800.

Effect of different of hardening agents on the cooling characteristics:
[0062] Initially, calcium sulphonates were evaluated as wetting agents for the purpose of enhancing cooling rate. However, later it was observed that calcium sulphonates act as a hardening agent in combination with wetting agent such as PIB succinimide to improve the hardening power of the quenching oil composition. So, evaluation of calcium sulphonates as such of different TBN can be considered as effect of different hardening agents.

Effect of combination of wetting agents on the cooling characteristics:
[0063] The effects of combination of wetting agents on the cooling characteristics, Max CR and hardening power (HP) as per ASTM D 6200 in presence of Group-I/Group-II base oil, at viscosity of 15/30/40/50/60 cSt, and antioxidant (AO) of 0.3% is disclosed in Tables 4-7.

[0064] The effects of combination of wetting agent 1 (WA1: PIB succinimide) and wetting agent 2 (WA2: PIB) on the cooling characteristics is disclosed in Tables 4 and 5. Green color represent the data with Group-1 base oil and red color represents the data with Group II base oils.

Ratio 1:1 ratio 1:2 ratio 1:3 ratio
WA1: PIB succinimide 0.5 1 2 3 4 5 0.5 1 2 3 0.5 1 2
WA2: PIB 0.5 1 2 3 4 5 1 2 4 6 1.5 3 6
Max CR, oC/s 66-79/ 71-85 68-80/ 73-85 93-102/ 98-104 95-105/ 100-106 95-105/ 100-106 95-105/ 100-106 66-79/ 71-85 68-80/ 73-85 93-102/ 98-104 95-105/ 100-106 66-79/ 71-85 68-80/ 73-85 93-102/ 98-104
Hardening Power (HP) 420-480/ 450-500 420-500/ 450-550 520-650/ 520-680 550-650/ 530-700 550-650/ 530-700 550-650/ 530-700 420-500/ 450-550 450-550/ 500-600 520-650/ 520-680 550-650/ 530-700 420-500/ 450-550 520-650/ 520-680 520-650/ 520-680
Table 4: Effect of combination of WA1 and WA2 on Max CR and HP

Ratio 2:1 ratio 3:1 ratio
WA1: PIB succinimide 1 2 4 6 1.5 3 6
WA2: PIB 0.5 1 2 3 0.5 1 2
Max CR, oC/s 68-80/ 73-85 93-102/ 98-104 95-105/ 100-106 95-105/ 100-106 93-102/ 98-104 95-105/ 100-106 95-105/ 100-106
Hardening Power (HP) 420-480/ 450-500 520-650/ 520-680 550-650/ 530-700 550-650/ 530-700 520-650/ 520-680 550-650/ 550-700 550-650/ 560-700
Table 5: Effect of combination of WA1 and WA2 on Max CR and HP

[0065] The effects of combination of wetting agent 1 (WA1: PIB succinimide) and wetting agent 3 (WA3: Low TBN Ca Sulphonate) on the cooling characteristics is disclosed in Tables 6 and 7.

Ratio 1:1 ratio 1:2 ratio 1:3 ratio
WA1: PIB succinimide 0.5 1 2 3 4 5 0.5 1 2 3 0.5 1 2
WA3: Low TBN Ca Sulphonate 0.5 1 2 3 4 5 1 2 4 6 1.5 3 6
Max CR, oC/s 66-79/ 71-85 68-80/ 73-85 93-104/ 98-108 95-106/ 100-113 95-106/ 100-113 95-106/ 100-113 66-79/ 71-85 68-80/ 73-85 93-104/ 98-105 95-106/ 100-108 68-80/ 73-85 68-80/ 73-85 95-105/ 100-105
Hardening Power (HP) 400-450/ 430-500 400-500/ 440-550 830-900/ 850-930 850-930/ 1000-1300 850-930/ 1000-1300 850-930/ 1000-1300 400-450/ 430-500 400-500/ 440-550 600-700/ 600-750 600-720/ 600-750 400-500/ 440-550 500-600/ 540-650 570-700/ 600-750
Table 6: Effect of combination of WA1 and WA3 on Max CR and HP

Ratio 2:1 ratio 3:1 ratio
WA1: PIB succinimide 1 2 4 6 1.5 3 6
WA3: Low TBN Ca Sulphonate 0.5 1 2 3 0.5 1 2
Max CR, oC/s 68-80/ 73-85 93-104/ 98-105 95-105/ 100-106 95-106/ 100-108 93-102/ 98-104 95-105/ 100-106 95-106/ 100-109
Hardening Power (HP) 400-500/ 440-550 500-630/ 520-650 500-620/ 530-650 530-650/ 550-700 500-600/ 520-650 500-620/ 530-650 500-620/ 530-650
Table 7: Effect of combination of WA1 and WA3 on Max CR and HP
[0066] The following remarks were observed on the cooling characteristics, i.e., Max CR and hardening power (HP):
• Combination of PIB succinimide (WA1) and PIB (WA2) in different concentrations and ratios in Group-I/Group-II base oil at viscosity 15 to 60 cSt has no effect in enhancing cooling characteristics.
• Combination of PIB succinimide (WA1) and Low TBN Ca Sulphonate (WA3) in 1:1 ratio at a concentration of 4-10 wt.%, preferably in 4-6 wt.% in Group-I/Group-II base oil at viscosity 15 to 60 cSt is optimized to get cooling rate of 93-113oC/s, and hardening power of 800-1300.

Effect of different antioxidants on thermo-oxidation stability:
[0067] The effects of different antioxidants on thermo-oxidation stability of quenching oil compositions as per IP 48 data is disclosed in Table 8. Furthermore, KV ratio is the kinematic ratio which is the ratio of final kinematic viscosity after IP 48 test to the initial kinematic viscosity before starting the IP 48 test.

1:1 ratio of PIB Succinimide and Low TBN Calcium Sulphonates in Group-I /Group-II base oil (15/30/40/50/60 cSt) at percentage dosages 4-10 wt.%
Phenolic Antioxidant 0.25 - 0.5 - 0.10 0.15 0.2 0.2 0.3-0.4
Aminic Antioxidant - 0.25 - 0.5 0.15 0.15 0.2 0.3 0.3-0.4
KV ratio (KVf/KVi) 1.8/1.7 1.85/1.8 1.7 /1.6 1.75/1.65 1.3/1.25 1.25/1.2 1.2/1.15 1.15/1.1 1.8/1.7
% Increase in carbon residue 0.7/0.65 0.8/0.7 0.7/0.65 0.8/0.7 0.32/0.27 0.3/0.25 0.15/0.12 0.13/0.10 0.9/0.8

[0068] The following remarks were observed due to the effect of different antioxidants on thermo-oxidation stability:
The combination of phenolic and aminic antioxidant in total amount of 0.2-0.5 wt.% ensure low soot forming tendency and excellent thermo-oxidation stability for ensured surface cleaning and improve surface finishing of finished components.

Measurement of the cooling characteristics as per ASTM D 6200:
[0069] In this method, an Inconel alloy 600 cylindrical probe of 12.5 mm diameter and 60 mm length was heated to a temperature of 850°C, soaked for at least two minutes and transferred to the center of the quench oil sample. The probe was equipped with type K thermocouple and was connected to the computer for cooling curve data acquisition. The temperature inside the probe analysis and cooling times were recorded at selected time intervals to establish cooling temperature versus time. The cooling characteristics of quenching oils is reported in terms of maximum cooling rate (CR) (°C/s), temperature at the maximum cooling rate (°C), cooling rate (°C/s) at 300°C and the time in seconds from immersion to three different temperatures mainly (a) 600°C, (b) 400°C, and (c) 200°C etc