PROCESS FOR HARD TURNING

FIELD OF THE INVENTION

[0001] The present disclosure pertains to technical field of machining of hard metallic materials. In particular, the present disclosure pertains to an atomized nano fluid spray impingement cooling system and process for machining of hard to cutmetallic materials.

BACKGROUND

[0002] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Many mechanical components are manufactured, at least in part, by being machined or turned on a turning lathe or similar machine. Hard metals or difficult-to-cut metallic materials produce localized extreme temperature during machining. This limits machining efficiency and also quickly wears out expensive cutting tools. Short tool life may contribute to machine downtime, high maintenance costs and damage to a metal workpiece being machined.

[0004] Hard machining with conventional flood cooling has been reported in the art but found to be ineffective.Prior art references that describe use of cutting fluids/lubricantsin hard machining are as follows: 1. Chetan, Behera, B.C., Ghosh, S., and Rao, P.V., (2016) Application of nanofluids during minimum quantity lubrication: A case study in turning process, Tribology International, 101, 234-246; 2. Padmini, R., Krishna, P.V., and Rao, G.K.M., (2016) Effectiveness of vegetable oil based nanofluids as potential cutting fluids in turning AISI 1040 steel, Tribology International, 94, 490-501 ; 3. Amrita, M., Srikant, R.R, Raju, and A.V.S.R., (2015) Performance Evaluation and Economic Analysis of Minimum Quantity Lubrication with Pressurized/Non-Pressurized Air and Nanofluid Mixture, International Journal of Mechanical, Aerospace, Industrial, Mechatronicsand Manufacturing Engineering, 9(6), 1012-1017; 4. Sharma, A.K., Tiwari, A.K. & Dixit, A.R., (2014) Progress of Nanofluid Application in Machining: A Review. Materials and Manufacturing Processes, 30(7), 813-828 DOI: 10.1080/10426914.2014.973583; 5. Khandekar, S., Sankar,M.R., Agnihotri, V., and Ramkumar, J., (2012) Nano-Cutting Fluid or Enhancement of Metal Cutting Performance, Materials and Manufacturing Processes, 27: 1-5; 6. Sahu, S.K., Mishra, P.C., Orra, K., and Sahoo, A.K. (201 ^Performance assessment in hard turning of AISI 1015 steel under spray impingement cooling and dry environment, Proc IMechE Part B: J Engineering Manufacture, 229(2), 251 - 265; 7. Landers, A., Balsari, P. and Gil, E. (2012) Nano-Cutting Fluid for Enhancement of Metal Cutting Performance, American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012, 73; 8. Sharma, A.K., Tiwari, A.K., and Dixit, A.R., (2015) Improved Machining Performance with Nanoparticle Enriched Cutting Fluids under Minimum Quantity Lubrication (MQL)Technique: A Review, Materials Today: Proceedings, 2, 3545 - 3551; 9. Sodavadia, K. P., and Makwana A.H.,(2014) Experimental Investigation on the Performance of Coconut oil Based Nano Fluid as Lubricants during Turning of AISI 304 Austenitic Stainless Steel, International Journal of Advanced Mechanical Engineering, 4(1), 55-60; 10. Hadi, M., and Atefi, R, (2015) Effect of Minimum Quantity Lubrication with Gamma-Al203 Nanoparticles on Surface Roughness in Milling AISI D3 Steel, Indian Journal of Science and Technology, 8(S3), 130-135;11. Yan, J., Zhang, Z., and Kuriyagawa, T., (2011), Effect of Nanoparticle Lubrication in Diamond Turning of Reaction-Bonded SiC, International journal of automation technology, 5(3), 307-312.12.A.K. Sharma, RK. Singh, A.R Dixit, A.K. Tiwari, Novel uses of alumina-MoS2 hybrid nanoparticle enriched cutting fluid in hard turning of AISI 304 steel, Journal of Manufacturing Processes 30 (2017) 467-482.

[0005] Hard dry machining with conventional flood cooling lowers the required cutting force and power requirements. However, achievable tool life and part finish often suffer under completely dry condition due to higher cutting temperature and thus accelerate tool wear rate. In addition, extreme tribological conditions developing at dry severe friction, and high tool-chip and work-flank interface temperature accelerate tool wear and reduce the strength of cutting tool, leading to tool failure and as a consequence deteriorate surface integrity. Further, use of flood cooling in hard turning displays thermal shock and thereby accelerating fracture of work-piece and cutting tool. Since temperature plays a vital role on tool wear, cutting forces, work surface finish and chip segmentation, there is a great deal of research on controlling cutting temperatures in hard turning applications.

[0006] The present invention satisfies the existing needs, as well as others, and generally overcomes the deficiencies found in the prior art.

[0007] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

OBJECTS OF THE INVENTION

[0008] It is an object of the present disclosure to provide a system and method for machining of hard metals that overcome one or more disadvantages associated with conventional techniques of machining of hard metallic materials.

[0009] It is a further object of the present disclosure to provide a new and improved cooling technique for hard turning applications.

[0010] It is another object of the present disclosure to provide a system and method for machining of hard metals by which service life of cutting tool can be enhanced.

[0011] It is another object of the present disclosure to provide a method for hard turning a workpiece, which is capable of reducing cutting temperature and tool wear and improving surface quality of workpiece being machined.

[0012] It is another object of the present disclosure to provide a cutting fluid that can effectively lubricate and cool a cutting tool-workpiece interface during machining.

[0013] It is another object of the present disclosure to provide a cutting fluid that can be used for cooling and lubrication in machining of hard metallic materials.

[0014] It is another object of the present disclosure to provide a cutting fluid that can provide both cooling and lubrication effects during hard turning.

[0015] It is another object of the present disclosure to provide a cutting fluid that exhibits improved machining characteristics compared to conventional cutting fluids. [0016] It is another object of the present disclosure to provide a cutting fluid that does not produce hazardous gas during machining.

SUMMARY OF THE I VENTION

[0017] According to one aspect, there is provided a system and method for machining hard metallic materials which can effectively control temperature and wear of cutting tools during cutting operations, thereby increasing tool life and productivity. The system and method disclosed herein are capable of producing atomized nano fluid spray that can provide cooling and lubrication between a workpiece and a cutting tool during machining. The atomized nano fluid spray can effectively reduce cutting temperature and tool wear, which ultimately improve tool service life, cutting speed, productivity and surface quality of processed workpiece.

[0018] In another aspect of the present disclosure, there is provided nano fluids that can be used as cutting fluid for machining of difficult-to-cut metallic materials. The disclosed nano fluids can provide both cooling and lubrication effects during machining of hard metallic materials, and can effectively control temperature and wear at cutting zone.

[0019] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0021] FIG. 1 shows schematic diagram of exemplary atomized nano fluid spray cooling cutting system, in accordance with embodiments of the present disclosure.

DETAILED DE SCRD7TION OF THE INVENTION

[0022] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0023] Unless the context requires otherwise, throughout the specification which follow, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense that is as "including, but not limited to." [0024] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0025] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0026] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0027] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. [0028] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0029] Various terms are used herein. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0030] In an aspect, the present disclosure provides a system and method for machining hard metallic materials, which can effectively control temperature and wear of cutting tools during cutting operations, thereby increasing tool life and productivity. The system and method disclosed herein are capable of producing atomized nano fluid spray that can provide cooling and lubrication between a workpiece and a cutting tool during machining. The atomized nano fluid spray can effectively reduce cutting temperature and tool wear, which ultimately improve tool service life, cutting speed, productivity and surface quality of processed workpiece.

[0031] In an embodiment of the present disclosure, an internal mixing nozzle can be used to mix compressed nano fluid and compressed air, and convert the resulting mixture into an atomized spray. The atomized nano fluid spray can then be sprayed onto a desired cutting zone where tiny droplets of cutting nano fluid get evaporated due to presence of heat at the cutting zone. Thus, the nano fluid spray can act as an effective cooling and lubricating media between tool-work and tool-chip interface.

[0032] In another aspect of the present disclosure, there is provided nano fluids that can be used as cutting fluid for machining of difficult-to-cut metallic materials. The disclosed nano fluids can provide both cooling and lubrication effects during machining of hard metallic materials, and can effectively control temperature and wear at cutting zone.

[0033] Referring to FIG. 1, there is shown a schematic diagram of exemplary atomized nano fluid spray cutting system 100 in accordance with embodiments of the present disclosure. The cutting system 100 can include a spraying system which can be coupled to a nano fluid tank and an air compressor. Different types of nano fluid with different concentrations can be prepared and stored in the nano fluid tank. The air compressor can be configured to discharge constant output pressure during machining of a workpiece. A workpiece can be fixed between live and dead centres and a cutting insert can be clamped to a holder as shown in FIG. 1. The working parameters of the cutting system such as cutting speed, feed rate, depth of cut in HMT lathe machine, air pressure and nano fluid pressure in spraying device can then set or adjusted to correspond to the workpiece. The distance between the spray nozzle and the cutting edge of the cutting tool may be varied in order to limit drop in nano-fluid pressure that may take place as it travels from the nozzle head to the cut section. Preferably, the distance between the spray nozzle and the cutting edge of the cutting tool can be 20±lcm. An infrared thermal camera can be utilized to record the cutting temperature at chip-tool interface.

[0034] Further, with respect to FIG. 1, the present disclosure relates to an atomized nano fluid spray cutting system (100) that comprises a spraying device (102) operatively coupled with a nano fluid tank (104) that stores at least one nano fluid; and an air compressor (106) configured to discharge constant pressure output of said nano fluid during machining of a workpiece.

[0035] In an aspect, the workpiece (108) can be fixed between live and dead centres, and wherein a cutting insert of a cutting tool (110) is clamped to a holder.

[0036] In another aspect, one or more working parameters of said system can be set or adjusted to correspond to said workpiece (108), wherein said one or more working parameters can be selected from any or a combination of cutting speed, feed rate, depth of cut in lathe machine, air pressure, water pressure, and nano fluid pressure in said spraying device (102).

[0037] In yet another aspect, the spraying device (102) can be operatively coupled with a spraying nozzle (112) that can be configured such that distance between said spray nozzle (112) and cutting edge of cutting tool (110) is varied in order to limit drop in nano-fluid pressure that takes place as the nano fluid travels from the nozzle head to the cut section. In an aspect, the spray nozzle (112) can be kept vertically at a distance of around 20 cm from the cutting edge of the cutting tool (110). [0038] In an aspect, the proposed system can be operatively coupled with an infrared thermal camera (114) configured to record cutting temperature at chip-tool interface.

[0039] In another aspect, the at least one nano fluid can be synthesized from any or a combination of nano particles of Aluminium oxide (AI ₂ O ₃ ) and Titanium oxide (T1O ₂ ).

[0040] In an aspect, compressed air from the air compressor (106) and the at least one nano fluid can be mixed in an internal mixing atomizing nozzle that is operated through said spraying device (102) to yield air mixed nano fluid. In an aspect, the internal mixing atomizing nozzle can be configured to convert the air mixed nano fluid into an atomized spray. In another aspect, the atomized spray can act as an effective cooling and lubricating media between tool-work and tool-chip interface.

[0041] In an exemplary testing process, hard turning of a workpiece under nano fluid (with 0.01% volume fraction) spray impingement cooling may be performed three times with fixed parameters to understand experimental uncertainty. A total of 15-20 experiments using single cut may be performed using different combination of nano fluid and volume fraction. For each experiment, new workpiece of same material and new cutting edge of cutting tool can be used. Cutting temperature with its magnitude value, and average work surface roughness may be measured during machining of a workpiece. The flank wear width and chip image can be measured using an optical microscope.

[0042] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

EXAMPLES

[0043] The present disclosure is further explained in the form of following examples. However, it is to be understood that the foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

Example 1: Investigation of performance of various cutting tools in hard turning under atomized nano fluid spray cooling condition.

[0044] An actual experimental set-up and methodology to investigate the performance of cutting tools in hard turning under atomized nano fluid spray cooling condition is shown in FIG. 1. Nano particles were first synthesized from two different metal powders namely Aluminium oxide (AI ₂ O ₃ ) and Titanium oxide (Ti0 ₂ ) by using a planetary ball mill for 10 hours. Once the desired sizes of nano particles were obtained and characterized, the particles were suspended in a base fluid (water) via two step method at three different concentrations. Compressed air and Nano fluids were mixed in an internal mix atomizing nozzle and operated through the spraying system. The internal mixing nozzle converted the air mixed nano fluid into an atomized spray. The spray nozzle was kept vertically at a distance of 20 ± 1 cm from the tool tip as shown in FIG. 1. The atomized nano fluid spray struck the cutting zone where tiny droplets of cutting nano fluid got evaporated due to presence of heat at cutting zone. The nano fluid spray acted as an effective cooling and lubricating media between tool-work and tool-chip interface.

[0045] Flank wear of cutting tool, average surface roughness of workpiece, cutting temperature at chip-tool interface and chip morphology were studied to judge the performance of Nano fluid impingement spray cooling in hard turning. Cutting speed, feed rate, depth of cut, air pressure and water pressure were considered to be machining parameters whereas types of Nano fluid and its volume fraction were considered to be variable in the hard turning process. The nanofluid concentrations used are listed in below Table 1. Several test runs were carried out using fixed and variable machining parameters. For each type of nano fluid with three different particle concentrations, the turning operation was performed 3 times. The hard turning operation was conducted by using a high precision HMT lathe. Commercial available multi-layer (A CVTiCN/TiN) coated carbide insert was used for machining hard-to-cut heat-treated AISI D2 tool steel. Cutting temperature at chip-tool interface for each test was measured during the machining using the infrared thermal camera. The cutting tool flank wear was measured using optical microscope, the average work surface roughness was measured using Taylor Hobson surface roughness tester, and chip shape, colour, tooth profile present on edge of chip were identified using image captured by optical microscope. Performance capability of nano fluids and its volume fraction have been decided based on magnitude of flank wear width, chip-tool interface temperature and average surface roughness. For machinability point of view, smaller the better criteria for all considered performance characteristics is favourable. However among all nano fluids and its volume fractions, the best performer nanofluid and its volume fraction is estimated based on lower flank wear width, lower chip-tool interface temperature and lower average surface roughness obtained in turning process. By utilising best nanofluid and its volume fraction, the continuous turning operation has been performed to obtain the tool life of cutting tool on the basis of standard criteria i.e. 0.3mm of flank wear width.

TABLE 1: Nano particle concentration in nano fluid

ADVANTAGES OF THE INVENTION

[0046] The present disclosure provides an atomized nano fluid spray impingement cooling process for machining of difficult-to-cut metallic materials.

[0047] The present disclosure provides a system and method for machining of hard metals by which service life of cutting tool can be enhanced.

[0048] The present disclosure provides a method for hard turning a workpiece, which is capable of reducing cutting temperature and tool wear, thereby improving tool life and surface quality of processed workpiece.

[0049] The present disclosure provides a nano fluid for hard turning applications, which is much easier to produce and less complex.

[0050] The present disclosure provides a nano fluid that can effectively control temperature and wear at cutting zone. [0051] The present disclosure provides a simple, highly efficient and cost effective system which is capable of machining difficult-to-cut metallic materials.

[0052] The present disclosure provides a system for turning difficult-to-cut metallic materials, which can be easily operated by an unskilled operator.

[0053] The present disclosure provides a system for machining of hard metals, which is compact and requires less workplace.

[0054] The disclosed hard turning system creates a cutting environment which is advantageous over dry and wet cutting environments.

[0055] The present disclosure provides a new and improved method that significantly reduces machining time for fine turning of difficult-to-cut metallic materials.

[0056] The present disclosure provides a cutting fluid that can provide both cooling and lubrication effects during machining.

[0057] The present disclosure provides a cutting fluid that exhibits improved machining characteristics compared to conventional cutting fluids.

[0058] The present disclosure provides a cutting fluid that does not produce hazardous gas during machining.