WO2011111063A2

WO2011111063A2 - High performance multipurpose oil composition for hydraulic cum cutting applications

Info

Publication number: WO2011111063A2
Application number: PCT/IN2011/000150
Authority: WO
Inventors: L. M. Pandey; A. K. Jaiswal; S. Pappy; C. B. Semwal; R. Mookken; K. P. Naithani; R. K. Malhotra
Original assignee: Indian Oil Corp Ltd
Current assignee: Indian Oil Corp Ltd
Priority date: 2010-03-08
Filing date: 2011-03-08
Publication date: 2011-09-15
Anticipated expiration: 2012-09-08
Also published as: WO2011111063A3; WO2011111063A9

Abstract

A high performance multipurpose oil composition required for circulating, hydraulic and smooth gear cutting operations and satisfactory lubrication of hydraulic systems during running of gear hobbing machines is disclosed herein. The multipurpose oil comprises of a mixture of solvent refined mineral base stock and severely hydro-processed based stock oils incorporated therein suitably chosen additives which provide for extreme synergism of different optimum superior properties for the oil proven by different physico-chemical tests as compared with conventionally known oils.

Description

High Performance Multi irpose Oil Composition for Hydraulic Cum Cutting

Applications

FIELD OF THE INVENTION

[001] This invention relates to the development of high performance composition of multipurpose oil, which can be used for circulating, hydraulic and gear cutting applications. In general, hydraulic oil and cutting oil are being used in gear hobbing machines.

BACKGROUND OF THE INVENTION AND PRIOR ART

[002] In automobile gear manufacturing industry, gear hobbing, gear shaping and gear shaving are important operations. Gear hobbing process is done to produce gears with precise geometries. In this process, the cutting tool (hob) and work piece rotate continuously displaying a rotational relationship. A right quality of gear cutting fluid is required to manufacture gears with precise geometries. The precise gear geometries are important to have efficient transmission of power.

[003] Conventionally, two different types of lubricants are used in the gear hobbing machines, one satisfying the lubrication requirements of hydraulic system and the other has to fulfill the requirements of cutting application. As oil from hydraulic system leaks and mixes into the cutting sump or vice versa, it defeats the performance requirements of gear hobbing machines. In day-to-day plant operations, it is practically impossible to prevent ingress of hydraulic oil into cutting oil and vice versa. Hence, these oils with conventional formulations can often lead to the failure of performance of gear hobbing machines. Sometimes intermixed oils result in ineffective sealing, drop in pressure and jerky motion of the tool, which in turn affect the tool life and surface finish of the manufactured gears. This is due to the additive incompatibility between conventional hydraulic and cutting oils and hence two incompatible chemistry based oils are not recommended for such applications. Thus tailor made multipurpose oil is required for smooth and satisfactory operations for gear hobbing machines.

[004] The presence of metal particles in gear cutting oil is generally responsible for leakages through valves and results in uneven tool clearances, which leads to inaccuracies in geometries of the gears thus manufactured. It results in higher contact pressure on the tool and leads to generation of more amount of heat during gear hobbing process, thereby shortens the tool life and tends towards rise in temperature of the cutting oil sump. The customers/users expect problem free operation of the gear hobbing machines.

[005] AU200137370A of Mobil Oil France discloses a neat cutting oil composition comprising from 10-99% of the white mineral oil and from 3-40% of an ester from a dicarboxylic acid and a mono-alcohol. Also it comprises at least one ingredient selected from the group consisting of lubricity agents, antioxidants, extreme pressure and antiwear agent and antimist agents. The composition is used in honing, super finishing agent, grinding, gear grinding (claimed), internal and external broaching, tapping, threading, gear cutting, shaving, gear hobbing, gear generating, reaming, automatic works, milling, form turning, planning, parting off, drilling, boring, sawing etc.

[006] US983193A of Idemitsu Kosan Co discloses an oil composition for heat treatment of a gear and gear treated by using the oil composition, which comprises mineral oil having a kinematic viscosity of 5-40 mm²/sec at 100°C for heat treatment of gear and phosphoric acid ester compound which can improve the resistance to pitching and oxidation stability, brightness test, cooling property test, FZG test.

[007] JP03469546B2 assigned to Yushiro Chem Ind; Honda Motor Co discloses a cutting oil composition for gear cutting which comprises the base oil (for example, mineral oil, synthetic oil) with a kinematic viscosity of 8-50 mm /sec at 40°C with a chlorine free, sulphur containing extreme pressure additive. The composition can also be used as fuel lubricity and antiwear additives in combustion fuels such as hydrocarbon fuels, jet fuel, rocket fuel and diesel fuels.

[008] There are some other related patents, viz, GB1230106A (Dow Corning) on gear cutting, DD220968B1 (Heartol Werk) on cutting oil composition for gear cutting and broaching; TW200508384 (Idemitsu Kosan Co) for buffer, power stearing, gear cutting and grinding process, plastic working and motor vehicles; AU199921113A (Verginia Tech) for lathing, broaching, tapping, threading, gear shaping, reaming, drilling, milling, hobbing, grinding, turning operations; US7645727B2 (GM Global Tech) for reducing wear on a metal working tool, preferably a hobbing tool.

[009] Efforts are underway to find ways and means for achieving compatible additive chemistries in different applications such as circulating, hydraulic and cutting applications. [010] The property of hydraulic oil plays a vital role in the performance of hydraulic systems and decides proper movement of tools/jobs etc. The conventional hydraulic oil specifications viz. DIN 51524 Part II and Indian Standard IS-11656 satisfies hydraulic oil requirements. The property of conventional cutting oil is to meet the performance requirements of all machining operations on ferrous or non-ferrous metals and is being used for gear hobbing, gear shaving, screw cutting, tapping, milling and reaming operations etc. The Indian standard IS- 3065 covers the cutting oil requirements. There is no national or international standard available for multipurpose oil for hydraulic cum cutting applications. However, few multipurpose products are commercially available in the market.

[011] The important properties for antiwear hydraulic oil is adequate viscometrics, superior antirust and anticorrosive properties towards steel and yellow metals, excellent thermal/oxidation stability and adequate antiwear properties for smooth running of hydraulic system. In addition, satisfactory and smooth gear cutting operation properties such as excellent cooling, oiliness and load bearing capability/extreme pressure properties are required. The important properties (Table 1) required for multipurpose oil for satisfactory running of gear hobbing machine are as follows:

• adequate viscometrics

• superior antirust/anticorrosive property

• excellent thermal/oxidation stability

• excellent oiliness property

• superior anti wear/extreme pressure property

Table 1: Important properties of multipurpose oil:

• Steel rod rating

Seal Swelling test

DIN-53521 ÷ ;:·■^■.·^■ % Change in volume

@100°C for 168 hrs

Weld load, Kgs IP-239 • Load bearing capability, Kgs

Wear Scar Dia, mm D-4172 • Wear of balls, mm

Tapping torque rig test D-5619 • % Efficiency

• Coefficient of friction

SRV friction wear test In-house

• BSD, mm

[012] In addition, during actual gear hobbing operation, multipurpose oil should provide no abnormal smell, lesser amount of fume / smoke generation, free of sludge / debris generation during extended use.

[013] Thus there exists a need to develop an oil that possesses excellent thermal/oxidation stability, superior yellow metal compatibility to provide adequeate sealing, accurate pressure, smooth motion of cutting tool and system free of sludge and debris etc to achieve extended service life.

[014] A primary advantage of this invention is to provide a high performance multipurpose oil composition having superior compatibility amongst the chosen additive system.

[015] Another advantage of this invention is to provide a superior multipurpose oil composition having excellent metal compatibility, thermal/oxidation stability, less sludge building tendency, low reactive acidity and superior load bearing capability.

[016] A further advantage of this invention is to provide an operator friendly composition having excellent machining operation in the gear hobbing machine or system.

[017] Another advantage ot mis invention is to provide viscometrics, use of synthetic and incorporation of superior class additives to exhibit aforesaid properties to enhance the useful life of the oil as well as machine / tool. DESCRIPTION OF THE INVENTION

[018] According to the present invention there is provided a high performance multipurpose oil composition which comprises a mixture of solvent refined mineral base stock, severely hydro-processed base stock and additives selected from sulphur and phosphorus containing ashless and metal containing alkyl thiophosphates as an antiwear/extreme pressure additive, detergent, lubricity improver, antioxidant, metal deactivator and antifoam.

[019] In accordance with the preferred embodiments of this invention, considering various requirements of multipurpose oil and with a view to achieve excellent thermal/oxidation stability and tribologial performance, a balanced tailor made additive package has been formulated by incorporating high performance compatible additives in combination with solvent refined and new class of hydro-processed base stocks.

[020] Mineral lubricating base oils used in this invention can be suitable solvent extracted, de waxed, hydro-finished base-stocks having high viscosity index (HVI). The mineral oil base stocks can be in combination with the base stocks obtained from severely hydro- processed technique having very high viscosity index (VHVI) or synthetic base stocks, to achieve optimum viscometrics.

[021] The mixture comprises of 47 to 53 wt% of above said solvent refined base stocks and 40 to 45 wt% of severely hydro-processed base stocks.

[022] The efficient additives present in this composition can be an array of conventional additives available commercially such as antiwear, extreme pressure agent, lubricity improver, antioxidant, metal deactivator, detergent and antifoam additives etc.

[023] The antiwear/extreme pressure additives can be either of metal or ashless or in combination of sulphur and phosphorus containing used and belong to classes of alkyl thiophosphates. This can be of C2 to C14 alkyl dithiophosphate.

[024] The antioxidant used in this invention is hindered phenol. The hindered phenol can be ortho-alkylated hindered phenol.

[025] The detergent used in this invention is natural or synthetic metal containing petroleum sulphonate having 200 to 300 TBN.

[026] The chosen lubricity improver provides superior antiwear/extreme pressure performance. The lubricity improver can be complex alkyl ester of varying alkyl chain length and polyvalent alcohols. The molecular weight of this lubricity improver can be 3,000 to 17,000 gm/mol.

[027] To improve lubricity and to impart further antiwear and extreme pressure performance, alkyl ester can be used in combination with other additives to enhance overall performance.

[028] This new formulation of high performance multipurpose oil, according to this invention showed extreme synergism with respect to all designated properties.

[029] In view of the prevailing hydraulic oil and cutting oil specifications, following tests were adopted for performance evaluation of multipurpose oil viz. kinematic viscosity @ 40°C, kinematic viscosity @ 100°C, Total acid number (TAN), Copper strip corrosion @ 100°C for 3 hours, rust prevention test as per D 665 'B' method, Cincinnati Milacron thermal stability test as per 'A' procedure and tapping torque test.

[030] The high performance multipurpose oil composition prepared as per the present invention was evaluated in the laboratory for various properties to assess the performance.

[031] After the detailed lab evaluation, this new high performance multipurpose oil was put for field evaluation in an established gear-manufacturing plant with an aim to establish the performance and service life of oil.

[032] The important outcome ot the field trial on multipurpose oil is as follows:

• The high performance multipurpose oil possesses adequate viscometrics, higher viscosity index, superior antirust and anticorrosive properties with excellent cooling efficiency and load bearing capability

• No abnormal fumes/smoke, no change in color of oil, no sludge generation and no changes in color of metal chips during the field trial

• New oil provided excellent lubrication to hydraulic machine for the movement of tool / jobs etc.

• New oil provided excellent lubrication, cooling efficiency and load carrying capability, which resulted to better surface finish of manufactured gears with no distortion in designed gear profile

• Flow of oil from sump via pump was good, which provided better surface coverage by oil eliminating the possibility of metal, to metal welding and resulted to better surface finish • Enhancement of cutting tool life of around 15% for the number of gears manufactured during the trial over the conventional oil

• Used oil samples collected at different intervals and evaluated for kinematic viscosity @ 40°C, @ 100°C showed no abnormal rise in viscosity, minimal change in TAN and no abnormal wear metals build-up

• The reduction in temperature rise of sump oil was around 2-3 °C lower over conventional oil

[033] An important benefit emerging out is the development of high performance multipurpose oil, which is having extreme synergism between the chosen additive system. The composition met the performance requirements of gear hobbing machines for hydraulic and cutting applications during the field evaluation.

[034] A high performance multipurpose oil composition prepared according to the preferred embodiment is herein described in the following examples:

Example!:

[035] 0.2 gms of ashless dialkyl dithiophosphate having C2 to C14 alkyl chain length was mixed with 0.8 gms of metal containing dialkyl dithiophosphate, 2 gms of polymerized ester from fatty compounds, v.zs gms ot allcyl ester, Ό. 2 gms of metal containing petroleum sulphonate and 0.30 gms of phenolic antioxidant and remainder being mixture of solvent refined and severely hydroprocessed base oil to form a blend of VG 10 to 70 of kinematic viscosity @ 40°C.

Example 2:

[036] 0.4 gms of ashless dialkyl dithiophosphate having C2 to CI 4 alkyl chain length was mixed with 1.5 gms of metal containing dialkyl dithiophosphate, 4 gms of polymerized ester from fatty compounds, 1.5 gms of alkyl ester, 0.10 gms of metal containing petroleum sulphonate and 0.80 gms of phenolic antioxidant and remainder being mixture of solvent refined and severely hydroprocessed base oil to form a blend of VG 10 to 70 of kinematic viscosity @ 40°C. [037] The invention also includes hydraulic and cutting applications using the multipurpose oil composition according to the invention.

[038] Further, the present invention describes details of the physico-chemical tests covering the high temperature stability, field simulated rig data and field experiences during the development of the new multipurpose oil. The multipurpose oil possesses better metal compatibility, high temperature/oxidation stability required for hydraulic system, efficient cooling of tools and superior load bearing capability required for satisfactory cutting operation. In addition, the invention describes the validation of laboratory data in an actual field trial done in the gear hobbing machines.

[039] The details of the said important test procedures are given below.

DEMULSIBILITY TEST

[040] The ASTM D-1401 test method [1] measures the demulsibility characteristics of industrial oil. Demuslibility is the ability of the oils to separate out from the water. This test measures, how rapidly and completely the oil / water emulsion separates after mixing equal volume of the oil and water for 5 minutes interval as per test conditions.

CINCINNATI MILACRON THERMAL / OXIDATION STABILITY TEST (METHOD - A) [041] To measure the thermal / oxidation stability of industrial oils, the Cincinnati

Milacron (CM) - A method [2] is most appropriate to consider, in this performance test, the polished pre- weighed copper and steel rods are placed in a beaker containing 200 ml of oil and heated to 135°C for 168 hrs, at the end of test, the copper and steel rods are examined for discoloration due to corrosion caused from acidic moieties and degradation compounds formed during thermal/oxidation process. The aged oils are to be evaluated for sludge content by filtration, percent change in viscosity at 40°C and chanee in total acid number.

FOUR BALL WEAR TEST

[042] The ASTM D-4172 test procedure is used for evaluation of the antiwear properties of industrial oils. The oil is tested in four-ball machine, where a rotating ball slides on three stationary balls. Three ½ inch diameter balls are clamped together and covered with the test oil. The oil is heated @ 75°C and then a forth ball (top ball) is pressed downward with the force 15 Kg into the cavity formed by the three clamped, stationary balls. This arrangement forms three- point contact. The top ball is then rotated at 1200 rpm for 60 minutes. The average scar diameter (mm) of the three stationary balls and load used in the test is reported.

SRV OSCILLATING FRICTION WEAR TEST

[043] SRV test rig used to assess the coefficient of friction of candidates applying 200N load, on the hardened bottom lapped disc, 50Hz frequency for 1 hour, in a point contact position on top of 10mm ball dia and coefficient of friction and Ball Scar Dia (BSD) were observed on candidate oils.

TAPPING TORQUE TEST RIG

[044] The tapping torque test ng used to simulate the process of metal removal of the candidate oils in the laboratory. The rig used to evaluate cutting efficiencies of test oils. The tapping torque test is performed on Ducom tapping torque tester using SAE 4140 steel by following ASTM D-5619 test procedure. The conventional hydraulic oil, cutting oil, available in the market, and combinations thereof also evaluated and examined in the present study.

[045] The field evaluation carried out on the developed candidate oil in the gear hobbing machine in a gear manufacturing company. The criteria used to assess the performance during the field trial was tool life, amount of smoke/fumes generated and its smell for operators' friendliness, color of machined metal chips, surface finish, gear profile, cooling efficiency of cutter, temperature of the sump oil, skin temperature of the machined gears and top up rate of oil etc. As per the industry practices, tool life of cutter was assessed by means of number of gear pieces manufactured before tool is damaged and thereby leads to inferior surface finish of the machined gear pieces. The used oils were also collected at different intervals and checked for physico-chemical properties and wear meiai analysis etc.

PERFORMANCE EVALUATION OF TEST OILS IN LABORATORY

[046] The physico-chemical properties of candidate vs. reference oil are comparable. The newly developed candidate possesses excellent thermal/oxidation stability and superior metal compatibility as seen in CM-A test. The aged oil (CM- A) showed minimal percentage change in kinematic viscosity and nil sludge (figure- 1). It results to higher accuracies, precise movement of tool and work pieces in the hydraulic circuits of gear hobbing machines.

[047] The tapping torque test result clearly indicates that candidate oil possess a shade better efficiency in tapping torque test from reference oil. After artificially mixing of 5% of conventional hydraulic oil in conventional gear cutting oil, thus the contaminated oil showed deterioration in tapping efficiency to the tune of 25% (Table-2). The intermixing of such oils during actual operation in the field therefore leads to reduced tool life and results to inferior surface finish and distortion in geometries of gears thus manufactured. The surface finish of the nuts in tapping torque test was much smooth with the candidate oil, as seen under optical microscope, in comparison to the other test oils.

Table - 2: Test Results of Tapping Torque Rig Tests on Conventional oil and New Oil:

FIELD EVALUATION ON NEW CANDIDATE OIL

[048] In order to validate the performance of newly developed candidate, new oil was charged in the sumps of hydraulic and cutting systems of the gear hobbing machine. No abnormal fumes/smoke, no appreciable change in color of oil, nil sludge generation and no change in color of metal chips observed during the trial. The new oil provided excellent lubrication to the hydraulic machine for the movement of tools/jobs, superior cooling of tool and excellent load bearing capability, it resulted to excellent surface finish with precise gear geometries of the gears thus manufactured. The test results of used oils collected at different intervals showed minimal change in kinematic viscosity, total acid number and no abnormal wear debris build-up (Fig-2, Fig-3, Fig-4 and Fig-5). The top-up rate of candidate oil and skin temperature of the machined gear pieces was normal. The enhanced tool life of around 15% with the increase in number of gear pieces manufactured before the tool is changed for refurbishing and the sump oil average temperature was lower of around 2-3°C from reference oil.

[049] The newly developed candidate oil showed all required qualities and was recommended for wide scale use in gear nobbing machines.

DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANING DRAWINGS

Figure 1 shows the results in Cincinnati Milacron thermal / oxidation stability test.

Figure 2 shows the percentage change in kinematic viscosity @ 40°C of the candidate oil vs reference oil.

Figure 3 shows the percentage change in kinematic viscosity @ 100°C of the candidate oil vs reference oil.

Figure 4 shows the change in TAN of used oils during field trial.

Figure 5 shows the results of wear metals build-up during field trial.

Claims

WE CLAIM:

1. A high performance multipurpose oil composition comprising:

a mixture of solvent refined mineral base stock and severely hydro-processed base stock, and

additives selected from sulphur and phosphorus containing ashless and metal containing alkyl thiophosphates as an antiwear/extreme pressure additive, detergent, lubricity improver, antioxidant, metal deactivator and antifoam.

2. The high performance multipurpose oil composition as claimed in claim 1, wherein said mixture comprises 47 to 53 wt% of said solvent refined mineral base stock and 40 to 45 wt% of severely hydro-processed base stock.

3. The high performance multipurpose oil composition as claimed in 1, wherein the additive system is chosen in such way that it is compatible for a high performance multipurpose oil.

4. The high performance multipurpose oil composition as claimed in claim 1, wherein the lubricity improver is selected from alkyl esters of varying alkyl chain length and polyvalent alcohols in dosage of 0.25 to 1.50 wt%.

5. The high performance multipurpose oil composition as claimed in claim 1, wherein phenolic antioxidant between 0.30 to 0.80 wt%, metal containing detergent between 0.02 to 0.10 wt%, polymerized ester from fatty compounds between 2 to 4 wt%, ashless and ash containing alkyl (C2-C14) dithiophosphate between 0.60 to 2.30 wt%.

6. The high performance multipurpose oil composition as claimed in claim 5, wherein the antioxidant is hindered phenol and preferably ortho-alkylated hindered phenol.

7. The high performance multipurpose oil composition as clamed in claim 5, wherein the detergent is synthetic or natural metal containing petroleum sulphonate having 200-300 TBN.

8. The high performance multipurpose oil composition substantially as herein described and illustrated particularly with reference to the examples.

9. The high performance multipurpose oil composition as applied to gear hobbing applications.