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Module 1: Cutting Fluids

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Cutting Fluid Additives

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Video 1: Composition structure of Cutting FluidsSo, we are discussing about machining fluids and its properties, benefits, when you willuse this cutting fluids in the machining operation what are the things that we are going getbenefit out of it, as well as if you do not use it how the friction coefficient goes highthen the power and other things goes high so that the requirement will be very highand the losses will be more. So, now, we will move on to the other part where we will studyabout the additives. What are the additives that are used in thecutting fluids? What are its properties? How this will affect various properties of thecutting fluid? And how it will benefit the product and all those things we will see.So, the cutting fluid additives, there are many additives ranging from emulsifiers tothe rust inhibitors and their mechanisms and all those things.If you see the cutting fluids there are ah two types of cutting fluids normally metalworkingfluids are the broadly says this word, but ah cutting fluids are specified words. So,cutting fluids are one part of metalworking fluids. Metalworking fluids even metal formingacross some of the grease is they will use, some of the lubricants they will use thoseare also come under the a metalworking fluids. So, cutting fluid is subset of the metalworkingfluid. In the cutting fluids where are there arethe oil based cutting fluids and the water based cutting fluids. In the water based cuttingfluids we all because since we are talking about the water based because water basedyou will give you the better cooling ability for that purpose we always go for water based.In the water base we have emulsions based and we have solutions, but normally we justgo to the emulsions type mostly. But the additives normally whatever we use are the commonlyused by the people operating people are extreme pressure reduce, anti wear resistivefriction,modifier, emulsifiers, biocides, corrosion, inhibitors are rust inhibitors antifoam andantifogging some of the things are commonly used names only ok, antifoam are the anotherone. If you see the cutting fluid composition structurewhat are the things it will have? It will have a base, but that is called the mineraloils are we can say the esters and second followed by the emulsifiers, normally sulphonatessoaps synthetic tensides these are all the some of the examples that will normally blendwith the cutting fluid. The third one is corrosion prevention, for the corrosion prevention normallycorrosion inhibitors are used which are again sulphonates soaps, amines, fatty acids andamides group pH regulators, pH regulators is required because if the pH goes up anddown. So, then there is a chances of metallurgicalchanges on the product because of the the change in pH the it will causes the a metallurgicalchanges because of the high temperature that is there in during the machining operationand all those things. So, wear protection normally tool where one has to protect forthat purpose mineral oil esters. Again we can see a this is a normally lubricant basedparticles you can use or dominating character; that means, that you can use less amount ofwater in the composition and all those things. Biocides normally biocides are used for theah formation of microbial organisms in the ah cutting fluids.So, antifoaming agents normally antifoaming agents are used such as silicon oils, wax,emulsions and all those things these are used to not generate the foam during the machiningoperation. If the ah foam takes place what will happen the visibility goes up and thereis a disturbance in the machining operation also causes that is why normally antifoamingagents are used. So, emulsifiers just we get into the emulsifierswhat are the emulsifiers? How these are going to help on? These are the majors thing thatthe cutting fluid consist whenever you mix it is a emulsifiers. Emulsifiers are substanceswhich reduce the surface tension at the interface of two normally immiscible phases are allowingto mix ok. When there are two phases assume that there is a oil you have a oil you havea water if you are going to mix these are not going to mix because they have their differencesurface tensions. Whenever you mix the emulsifier what will happen? This emulsifier will reducethe surface tension between these two that means, relative surface tension that probablylike the highest surface tension material surface tension will be reduced and broughtnear to the lower surface tension. So, that both will become miscible that is what theintention of using the emulsifier. Emulsifier belongs to general class of compoundswhich are called as the surfactants actually ok, emulsifier ok, whenever you are talkingabout the surface tension reduction. So, these are used by the surfactants ok. So, the othername is also calls surfactant. If you see here you have a water you have oil wheneveryou use the surfactant surfactant will have the polar group and nonpolar. So, polar groupwill try to attach to the polar group that is called H 2 O and nonpolar group will attachedto the tail that is ah oil non polar. So, you have a head that is polar and tail nonpolar.So, what is polar and what is nonpolar? Some some people may be from b tech they may knowwhat is polar what is nonpolar. So, let me explain about polar molecules and nonpolarmolecules and all those things. In the polar molecules; that means, that since a emulsifierhas both polar and nonpolar head. So, what the polar head is going to do is electronsare not equally shared that is why you can see here the not shared equally. So, one someplaceminus are not constant there, one part of molecule is more negative than another partof molecules. So that means, that some part will have morenegativeness some part will have less negativeness and all those thing there will be a differencebetween these two things are commonly hydrophilic means what I will tell you in the upcomingslides, what is hydrophilic, what is hydrophobic and all those things. So, this will take careof the water content polar molecule the nonpolar molecules electrons are equally shared. So,electrons are equal shared in the nonpolar region and the no part of molecules is distinctlynegative or positive. So that means, there is no much differentiationbetween any part of this non polar region in a molecules. So, normally these are alla hydrophobic. So, water fearing and this hydrophilic means water loving. So, it willlove. So, the hydrophilic means it will the spread assume that I have a surface of hydrophilicsurface on which if I put water it will love; that means, it will spread easily. In hydrophobicmeans you just fear. So, it is not like assume that a particular person for example, commonexample of the phobia if you see if there is a diagnosis of CT scan there will be acylindrical hole big hole will be there. So, some people may fear inside going that iscalled phobia. So, you do not want to go; that means, that another waterfalls and hydrophobicsurface it will not go it do not want to spread on that one just let me go away by so it willbe having a a spherical type of ball and it will go some. Example is lotus leave thatis called hydrophobic surface basically. This is about the mechanism. However, we willgo into the complete mechanism when a surface active emulsifier is used to combine withwater and oil if you see in the picture. So, normally this blue circles. This blue circlesare nothing, but you are polar molecules is attached to the water; that means, this blueone is water this is oil. So, while the nonpolar tails that is blacklines which are there inside the yellow region are attracted to oil and allowing the waterto combine this means combine anyhow. You will see another picture you will have waterand oil initially assume that I am mixing water and oil. So, this surface tension isdifferent and viscosity is different and the density of this fluids are different, wheneveryou add both these things what will happen it will be separate entity, one is this oneanother one is this one ok these are separate entities when you add emulsifier. So, whatwill happen? This is a polar head and nonpolar tail this will go and occupy ah their respectiveregions. It is polar go and occupy the polar regions that is water and it will dis integratethe oil molecules and it form a emulsion ok. Emulsion does not mean that it is a uniformfluid it may be a uniform fluid. But the thing is that these interfaces are still existing;that means, that I mean to say water is a uniform thing I am not saying whenever youmix water with oil it is not that single entity it is a dual entity which where is the twothings are there , but uniformly dispersing. In, if you do not add it is non uniform dispersingif you add the oil and water will have uniform dispersing that is the what I mean to sayok. So, now you can see is a surfactant and oil,normally surfactant is nothing, but one of the emulsifier whenever you are mixing withthis water aqua solution. So, initial system normally what will happen once you have asurfactant plus oil is there just you put into the water what will happen this oil moleculeswhich are surrounded by the surfactants will try to pull into the water because it is waterloving. Assume that this polar molecules of water loving molecules this will try to gointo the water whenever you want to go. Now, it will disintegrate this disintegrateand form a uniform dispersion that is what you can see here. The surfactant moves tothe water phase surfactant that polar head tries to move into the water phase that iswhy it will gradually become these type of things ok, and uniform.So, I am last what will happen it will pick up. Anyhow it is mechanism is shown here;however, the nanoemulsion is taken from the Google, but how the emulsification takes inthe water and oil emulsion. So, that is mechanism that I want to show ok. You have a water wherein you put the oil and you put the ah surfactant are emulsifiers then you just stir it. Thepolar head will track the nonpolar hill a group of polar hills will go by disintegratingfrom oil molecule and form at different different uniform locations to make a uniform emulsionthat is called liquid liquid emulsion.
Video 2: Classification and Types of EmulsionsClassification of emulsifiers, if you see the classification of emulsifier normallymonomolecular film is there, another one is multimolecular film is there, solid particlefilm also is there ok. If you see the monomolecular film as you have seen if it is in water thisis the water region and this is the oil region and you can form a monomolecular film thatis called coherent monomolecular film you can form here that is called whatever thepoint here is said is here. And flexible film formed by the sulphonatedacid. So that means, at the film is flexible enough and can prepare oil in water or waterin oil emulsions. You can meet two types of a emulsions either in oil in water or waterin oil. What is water in oil and oil in water will see in the upcoming slides.Lower surface tension and increase the stability of emulsions. The surface tensions it lowerthe surface tension of the oil or another fluid which is about to mix two fluids whicheverhaving the highest surface tension it will reduce to bring to the second one and tryto mix it. Example potassium laurate is the one thing, polyoxyethylene sorbitan is anothermonooleate is the another one. So, these are the two examples of monomolecular film basedemulsifiers ok. Multimolecular films emulsifier strong andrigid formed a mostly by the hydrocolloid as I said colloid. Emulsifier is liquid toliquid here if it is semi solid to liquid or solid to liquid normally it is called lesscolloid hydrocolloids. Normally if you might people might have heard about hydrogels, gelatinhydrogels, t e g hydrogels, p l e hydrogels , or p e g p l e p g hydrogels, there arehydrogels, hydro gel. So, you have a sphere where in the water isbounded by the structure interlinking of this is nothing, but the hydrogel. It will havehydrothat means water will be there it will be in a network form if you cut you cannotsee that one. It will be embedded in the polymer networks ok that is about the colloid. Producesoil in water emulsion this normally produces the only one type that is called oil in wateremulsion may not be vice versa have no effect on the surface tension.So, it will have the lower effect of the surface tension; that means, that it will may notform the emulsion proper because it may not reduce the surface tension as I expected ora person that is going to mix is expect. So acacia is one thing and gelatin is anotherthing if you can see multimolecular you can see all the things are on the surface it isnot there in the inside the surface ok. This is how about the multimolecular will takesplace. And solid particle films film formed by thesolid particles that are ah small in size compared to the droplet of the dispersed phasethese are the solid particles that forms on the surface. Can form oil in water and waterin oil emulsion both are emulsions it can form. Particle must be wet in both phasesin order to remain at the interface with that; that means, that it should be wet if a particleis there it should wet from the oil side it should wet from the leaf that is water side.So, it should be able to wet on the both sides. For example, graphite is one of the example,bentonite is another example these are the examples of the emulsifier.So, ah you can see oil in water emulsions. Oil in water emulsions is one type of thingand the second one is water in oil emulsions, multiple emulsions and micro emulsion theseare the different varieties of emulsions are there. If you see water in oil emulsion itis look like this anyhow I will show you a bigger picture in not this one just you willcome across in the next slide or something this is called water in oil emulsion.These are the water molecules blue one are water molecules, here the orange one is oilwhich is a continuous phase and dispersed phase is water. Oil in the water here oilis ah spirit and water is there in the continuous phase. Water in oil emulsion oil is the dispersionmedium and the water is the dispersive medium ok. See water in oil; that means, it is simplyshows oil is my continuous phase and I am putting water in it ok. That is all simple.So, in this one oil is a dispersion medium where is is continuous medium water is justdropped in. These are greasy not water washable. What will happen when ever these are emulsionsare also used in washing industry, these are also used in many many industries such aspaste industries emulsions are used detergent liquids nowadays ah these are used in allthese things. Used externally to provide the cooling effect, normally this also helps inthe cooling effect. Why I am saying is you have oil which is a better lubricant wheneverif you want a cooling ability what you do you cannot use directly you have to mix water.If you mix water cooling ability as from the curve of ah lubrication versus the coolingyou see the water is a better coolant. So, you have to mix it if you mix it water yourcooling ability will increase. Evaporation of the moisture from the surfacelike skin if normally these also will use in the cold cream, so evaporation of the moisturewill takes place; that means, water content is very less. So, equally goes up off if thetemperature increases and prefer for external use like creams and all those things. Normally,water content will be very less and oil content is major content which is a continuous phasewhenever you apply on this ice cold creams and all those things water will goes off thatis what its. So, these are the one varieties that will normally use in the metal cuttingalso. For analogy purpose we have taken from creams and all those things.If you can see oil droplets that is called the oil in water this is a continuous phasewater is a continuous phase that is dispersion medium and oils are dispersed inside ok.And this oils along with the surfactants it will disintegrate and forms another one. So,oil heat is the oil and this is a water water molecules, only thing you just it clearlyobserved where the polar side of emulsion is sticking. Water molecule if it is hereyour polar head is sticking to that one if you see in this first figure non polar issticking ok. Polar always with water non polar always with leaf of that is called with oilthat is about the water in oil, oil in water emulsions.In oil in water emulsion water is the dispersion and oil is a dispersion that mean that youhave water where in your putting oil; that means, that have a water in a glass just Iam putting coconut oil to it some drops of coconut oil to it. Non greasy and easily removablethe skin because main content is water, so you just like of it will goes off and usethe externally provide the cooling effect that is called what is in the preset you havea major amount of water is there. So, it will be dominating cooling effects for the cuttingfluids. Preferred in internal use as a bitter tasteoil can be masked; that means, that normally this also used in the toothpaste applicationsand all those things slightly it will be give the bitter taste. If you see how the oil inwater water in oil looks like these are the droplets, if you are not going to use emulsifiersyou will have different sizes you can see at the different sizes will be there and thisis about water in oil where this blue ones are water and this particles are oil yellowones are oil. So, this is about oil in water, water in oil emulsions.Now we will go to multiple emulsion. So, what do you mean by multiple emulsions? You havewater and oil both two things are there, there are still more advanced things are there thatis called oil in water in oil water in oil in water. So, will go through it the multipledimensions are emulsion system in which dispersed phase contain the smaller droplets that possessesthe same composition as external phase. That means, the internal structure and completelyexternal structure will have a same; that means, water in oil in water. So, water isthere inside, oil is there on top of it again water will be there that is called you cansee the multiple emulsions called in two ways, oil in water in oil water in oil in water.So, this type two types of emulsions are there. If you see the picture you can clearly understandhow this will be for example, I will take the water oil in water emulsion if you seesame like ah continuous phase is water and internal phase again will be water if it isa there is a water then and if you take a spheroid which is the oil inside again waterwill be there ok. That is called water inside the oil and on top of it you have a wateragain ok. That is what the this one. So, microemulsions is another one, normallymicro nano if you go the basic advantage that you get is surface area will be large. So,if you have a more surface area what will happen suspending inside the liquid ah insidea leaf fluid will be easy that is what the advantage that is why people nowadays talkabout microemulsion, nanoemulsions and all those things. So, many somebody may be interestedin taking up the ah cutting fluid with microemulsions nanoemulsions and you can check the performance.
Video 3: Extreme Pressure, Anti-Foam Additives and BiocidesSo, next we will move on to extreme pressure additives. What is this extreme pressure additivesand all those things we will see. So, extreme pressure additives a work reactingwith a metal form a compound that reacts a protective layer on the metal surface. Sincethis layer is softer than metal under extreme pressure conditions it bears of protectingin the metals. That means, whenever extreme pressure additive is added to the cuttingfluid if it is falls during the machining operation what will happen it forms a layerthat is soft compared to my parent material of that material.And whenever there is a pressure that falls are sharing takes place what will happen thatsoft layer will goes off by keeping the original metal layer intact that is what extreme pressureadditives will do. This layer is removed and extreme pressure additive as a form anotherlayer. What I mean to say is that since my cutting fluid is continuously falling if oneextreme pressure additive layer which is soft gone automatically it is falling. So, it willform another layer that is what it mean to say.In contrast to action to antiwear additives extreme pressure to control the wear insteadof preventing it it will control the wear that mean as I said it forms continuouslythe softer layer on the metal layer. So, that it will not damage my, the to assume thattool is there and cut work piece is moving on. So, if I have a cutting fluid continuouslyfalling even though it takes off only it forms a soft layer extreme pressure additive fuseit will take off again, since the cutting fluid is there around continuously fallingit will form another layer and it will control the wear up to the certain limit it will notprevent or something it cannot prevent, but it will control up to certain limit.So, if you see here what will happen, this is a surface where some of the metal surfaceit will form on the soft layer will form on this one. If the soft layer goes off againsoft layer will come. If you see in the tribiological where where the soft layer will be formedon this one and soft layer will goes off whenever there is a sliding because of certain normalload also is there. So, what will happen this soft layer will goes off and soft layer willbe uniformly it goes off it will form it goes off it will form. So, again I will goes off.So, that is the beauty about this one in the tribiological aspect.Added fluids where the cutting fluid forces are particularly high such as tapping andbroaching operation . These are applied for heavy load processes where the cutting forcesare high like broaching operation you need to have lot of forces during the machiningoperation. So, even though it forms soft layer the softlayer because of the heavy loads may take away and still have it forms into a layer.High pressure additives provide tougher more stable form of lubrication the chip tool interface.Means it will form a stable soft layer continuously till the cutting fluid fall in that area.Extreme pressure additive include sulphur chlorine and phosphorus compounds, these reactat high temperature in cutting zones to form metallic sulphate, chlorides and phosphatewhat will happen. These are all made up of sulphur chlorine or phosphorus compounds.These compounds will react in the machining region where the temperature is very highand form metallic sulphates, metallic chlorides and metallic phosphides. This will form andit will give the soft layer, provide extreme pressure lubrication that is always the softlayer will be questioning it will give the lubrication like questioning and all thosethings. Also provide a film that tool surface withanti weld properties to minimize build up edge, that mean what will happen it will formin and if it is soft layer is forming there is no formation of built up edge on top ofit if instantaneously there is a molten metal that is sticking to the surface from the chipback side on to this one since there is a high pressure additive which form a soft layeron this one what will happen it may not directly contact with my tool material. So, at certainpoint of time it may goes off. So, there is no formation of built up edge. Continuouslyif it falls is a soft layer do not have energy soft layer will goes off and because of thecutting fluid intake is regular. So, another soft layer will form. So, there is no possibilityof forming the built up edge. The possibility I cannot say a 100 percent is not there Icannot say, but possibility will less possibility will be there.
Video 4: Rust InhibitorsAnother important addition to the cutting fluid is rust inhibitor. So, rust inhibitorsmeans whenever the machining operation is going on is a cutting fluid contains 1 isto 10, assuming 10 litres of water the water will fall on a machining zone where the temperatureis high. And assume that I have a work piece of iron based work piece, in that circumferencesrust formation on my product that is coming out from the machine region is one of theproblem. So, how to prevent for that purpose we should always try to have the rust inhibitorsin the cutting fluid or rust inhibitors should be preblended in the cutting fluid so thatthis rusting effect will not takes place ok. So, water is the best and most economicalcoolant ok, because it is freely available at the same time cost free and it has if yousee the graph it has a better cooling ability. If you see the graph like lubrication versuscooling abilities water stays here ok. So, for that purpose this is a better coolantand it has no charge ok. So, causes part rust normally if you are notgoing to use this part will cost causes the rust formation. Rust in oxidize iron normallyif you see in a upcoming slides as you can see whenever I said in a previous lecturesalso if you have a mild steel plate you just put into the at open atmospheric conditionsrainfalls and air blows and on top of it and all this thing rust will takes place. Rustis nothing, but oxide film takes place and it is easily around able with nail if youjust scratch it it will goes off ok. Chemical cutting fluids contain the rust inhibitorsnormally synthetic and semi synthetic cutting fluids will basically contains this ah rustinhibitor. So, these are in the polar form as I said polar non polar and it is formsa passive passivating layer. If you see a polar film and a passivating film negativelycharged long thin molecules attracted and firmly bond on themselves on the metal; thatmeans, if you are falling a polar film; that means, that polar head will go and stick onthe surface. So, that it will not allow the water content to come ok. So, that is oneone passivating film inhibitors combined the chemically with a metal ah and form nonporousprotective coating that prevents the rust ok.So, it will form a passive layer passivative layer means whenever you have rust inhibitorsare there these rust inhibitors it just go and coat on top of it; that means, that itwill go and sit on the top of it. So, that water content after that one if you are goingto put this one in a open atmosphere also what will happen because of the moisture contentin the water in the air are the chemicals that are present in the air like oxygen andall those things it will prevent from the rusting that is by making a passivating film.Modes of corrosion inhibition, such there are some modes that is barrier protectionjust you form a barrier like you just have a coating on top of it, the water moleculeswill be there. Cathodic protection normally this is a chemical reaction activate activecorrosion inhibition, anodic passivation and self healing and all those things. These arethe some of the chemical techniques where the anti rusting or rust inhibition will takesplace. Normally the some of the commonly used isbarrier protection. So, barrier protection is just you have a passivate layer, the layerwill be there on top of it if the waterfalls also it do not have much effect it will sitthere is no direct contact between two surfaces ok. There is no direct contact ok this isabout the anti rusting ok. So, surface integrity, I was just talkingabout the surface integrity and surface roughness I have already taught you. But I forgot togive you some other glimpse that is called surface integrity is surface condition ofthe work piecebeing modified by the manufacturing process the term is coined by the MichaelField and John F Kahles in 1964. Surface integrity means surface morphology plus surface metalurgyok.