WATER-SOLUBLE METALWORKING FLUIDS

Transcription

1 Registered trade mark Stevens Industrial Services (SIS) Ltd HIGH PERFORMANCE FLUIDS WATER-SOLUBLE METALWORKING FLUIDS general information booklet

2 Preface Unfortunately, it is a fact of life that metal working fluids are accorded a position of minor importance. The importance of these fluids only occurs when there are problems: the production process is suffering! Though, problems can be easily prevented if you know what you are doing. With this booklet we want to give you a little information about what a soluble metal working fluid actually is and how to realise a healthy, clean and trouble free production minimum of waste. A very important factor for trouble-free working is the correct choice of the fluid. Important parameters for a correct choice concerning fluids are material, product, machine and the nature of the industry. The wide range of chlorine-free THE WORKS products can help you to make the right choice. Our sales team are ready to give you any assistance you require. We hope that this booklet will help contribute to the optimisation of cutting fluid usage in your company.

3 Contents 1. General page 1 2. Main purpose of cutting fluids page 2 3. Structure of cutting fluids page 3 4. Maintanance and control of coolants page 5

4 1. General 1 Cutting fluids are preparations/mixtures used in the cutting and forming metal working industry for cooling, lubrication and swarf transport. CLASSIFICATION CUTTING FLUIDS: CUTTING FLUIDS 1. NEAT FLUIDS 2. WATER-SOLUBLE FLUIDS 1. Products, mostly based on vegetable or mineral oil, non-water soluble such as: - - Tapping fluids; - Stamping and deep drawing fluids. 2. Oil in water emulsion. If a mineral oil is introduced into water it will separate. To get a stable emulsion we have to add an emulsifier, so that water and any other additives do not separate. Other classifications of emulsion are: Synthetic emulsion : contains 0% min. oil; Semi synthetic emulsion : contains up to 40% min. oil; Mineral oil based emulsion : more than 40% min. oil. Production speed and price ( /m³) mostly dictates the choice of the cutting fluid and given a choice of neat or water-soluble the choice will often be water-soluble coolants. The economics involve not only the purchase of coolant but also the costs of waste fluids and by machine stoppage because of fluid change. Since the costs for waste disposal and machine stoppage become more important every year it is essential to keep these costs as low as possible. Crucial factors to maintain the costs as low as possible are: Right choice of the coolant, other oils and accessories. Setting up an efficient control and maintenance system. The right choice of the coolant must be made together with the supplier because only they can judge if their coolant is suitable for your application.

5 2. Main purpose of cutting fluids 2 During a metal cutting process temperatures of more than 1000 C will occur (see drawing). This heat transmission is 75% into the swarf, 18% into the tool tip and 7% into the product/component. It is therefore very important to keep the heat development as low as possible through lubrication and dissipation of the heat through cooling. Main tasks for cutting fluids are: lubrication and cooling. Cooling: Can be done best by water because water has excellent heat exchange properties. Further, water is a thin fluid which can remove the swarf easily Lubrication: Mostly done with a mineral oil containing extreme pressure (EP) properties, to keep friction as low as possible leading to less tool wear and prevention of swarf build-up and the opportunity for metals welding together.

6 A cutting fluid is necessarily very complex to be able to fulfill the many demands, such as: 3 -Cooling; -Lubrication; -Universal application; -Long life; -Noise reduction; -Prevention of metal welding and swarf built up; -Reduction of dimensional instability; -No foaming; -No sticking; -No dangerous vapours; -Skin friendly; -Friendly for machine paint; -Rust protection; -Surface optimisation -etc -Nowadays, increasingly, a cutting fluid must also be health and environment friendly. 3. STRUCTURE OF CUTTING FLUIDS To enable the fluids to meet all these requirements, a large number of different substances are required. An inventory of substances, which may be used in cutting fluids, showed that there are a total of over 300 different individual substances. Today, cutting fluids should (must) be free of many of the substances that were used as additives in the past, such as: 1. Chlorine; 2. Nitrite; 3. Di-ethanolamine; 4. Aromatic hydrocarbons; 1. When using chlorine-containing additives, harmful by-products occur at increased temperatures. These are very poisonous and irritating for the skin. (chlorine-containing vapours can penetrate our body and give severe health problems). Further, the disposal of chlorine-containing waste is more expensive than non-chlorine waste. These are excellent reasons to use chlorine-free metal working fluids. Chlorine-containing fluids were previously used because of there excellent EP properties in the temperature range of C. and because chlorine contributed to the stability of the coolants.

7 2. Nitrites had, in the past, a good record as anti rust inhibitors Nitrite however, forms nitrosamine, which is proven to cause cancer. The process for forming nitrosamine occurs more rapidly if there are amines in the fluid, especially di-ethanol amine (= emulsifier and corrosion inhibitor). The use of nitrite-free coolants only is no guarantee that nitrosamine can not be formed, because nitrite can get into the fluid over a period of time through: - Micro-organisms transforming nitrate in drinking water (used for diluting the coolant) into nitrite; - Absorption of nitrogen oxide from the air (exhaust gases); - Nitrite containing hardening salt, cleaners and/or corrosion inhibitors. So, a coolant must not only be free of nitrite, but it also must be free of diethanolamine to prevent the forming of nitrosamine, which can cause cancer. One should try to keep the nitrite content in the coolant below 50 ppm ( determined by analytical test strips), because amine-containing substances can always enter the fluid and nitrosamine can still be formed. 4. The use of basic oils with a high percentage of aromatic hydrocarbons (often cheap) can form, if heated below 1000 C, polycyclic aromatic hydrocarbons (PAH s). These polycyclic aromatic hydrocarbons can cause cancer. So it is important to use oils with an extreme low percentage of aromatic hydrocarbons. This is possible by using modern, more expensive refinery techniques. Environment- and health friendly metal working fluids are costly and need good maintenance and 'house-keeping' The Works products are completely chlorine free, nitrite free and di-ethanol amine free. The mineral oils have an extremely low percentage of aromatic hydrocarbons (<<0.5%)!

8 4. MAINTANANCE AND CONTROL OF COOLANTS Soluble cutting fluids typically consist of 95% water. The remaining 5% has to do almost all the work. Therefore, you need to control and maintain the fluid. 5 What you can easily do yourself: A. CLEANING Start with a clean machine. If there is any doubt, clean and disinfect thoroughly with a fluid advised by the supplier of the coolant. Also, use a cleaning- and disinfectant fluid if you change the coolant for any reason. The function of the cleaning is to soften dirt and to kill bacteria in the machine, especially on difficult places such as pipes and pumps. Also it is advised, 8 to 12 hours before cleaning out the machine, to add disinfectant cleaning fluid to the dirty coolant according the directions for use. There are two types of water-soluble system cleaners in The WORKS program which provide this disinfectant and cleaning process. Do not use cleaners like detergents, petroleum, degreasers etc. The residues of these products have an undesirable destructive effect influence on new on the coolants coolant. CLEANING OUT THE MACHINE WILL GIVE A POSSITIVE INFLUENCE TO THE LONG LIFE AND STABILITY OF THE NEW COOLANT B. TO MIX AN EMULSION An emulsion should always be mixed in such a way that water is poured into the mixing tank and the coolant concentrate is then stirred into the water whilst mixing forcefully. This is the only way to ensure that a perfect oil-inwater emulsion is produced. MIXING RULE: FIRST WATER - THEN OIL.

9 C. SLIDEWAY OIL 6 Use a slideway oil which can be combined with the coolant and which has de-mulsifying properties so that the oil can be skimmed off. The Works has first class slideway oils in its program that have excellent tolerance to The Works coolants. D. REFRACTOMETER Measure, with a regular frequency, the dilution of the water-soluble cutting fluid with a refractometer. This is because water evaporates and the coolant concentrate stays in the machine, resulting in increasing dilution. Reading scale A high concentration gives: - Poor heat dissipation; - Poor swarf removal; - Higher alkaline value, creating an unpleasant fluid for the skin - Higher concentrate consumption. A low concentration gives: - Poor lubrication, which means extra tool wear and poor product surface; - Corrosion; - No resistance against bacterial growth. NOTE: Use the right refractometer factor and dilution chart of the coolant. Ask for the correct dilution chart for each of The Work water-soluble coolants. Refractometer reading x factor = % mixing ratio.

10 E. ph VALUE AND NITRITE MEASUREMENT 7 Frequently measure the ph value of the coolant with a ph- indicating test strip or with a ph-meter (note that the ph meter has to be calibrated frequently). The ph value of the mixing water should be neutral, in other words around 7. The ph value of the mixed emulsion should be between 8,4 and 9,5. If the ph value is too low the corrosion protection will be reduced as well as the long life stability. If the emulsion is too high, (alkaline) it will tend to degrease the skin and remove the natural skin protection. Some materials, like aluminium, are very sensible for strong alkaline coolants Up to 14 ph value Steel Aluminium 7, neutral 5,6 skin Skin damage Alkaline Corrosion Acid ph measurement with indicating test strips

11 Frequently measure the nitrite value in the coolant with nitrite indicating test strips. When the nitrite value is more than 50 ppm, you should consider changing the fluid for health reasons (clean out the machine thoroughly). 8 Nitrite measurement with indicating test strips Other measurements like testing the oil- and dirt-content of the fluid can be done by the supplier of the coolant. E. WATER HARDNESS The hardness of the water depends on its content of water-soluble calcium and magnesium compounds. In very hard water the calcium and magnesium ions react with components of the emulsifying oil. This reaction forms compounds which are not soluble in water and may be precipitated in the circulation system. Since these reactions use up part of the emulsifier, it reduces the stability of the emulsion. This may lead to de-mulsification and oil separation. Soft water will increase the risk of foam. The ideal water hardness is 8 and 15 DH The Works has a control case in its sales program, consisting: hand refractometer, ph-, nitrite-, and waterhardness testing strips and dipslides for bacterial and fungicide test.

12 F. MAINTANANCE 9 Frequently remove tramp oils from the coolant such as: slideway oils hydraulic oils and cutting oils. This can easily be done by: - Vacuum; - Absorption; - Skimmer (Jokisch chain-skimmer). Filter the coolant frequently. An important accessory is a coolant and swarf vacuum cleaner with oil-water separation abilities (see photo below) or a professional emulsion cleaning system. Coolant and swarf vacuum cleaner, with filter and separation abilities The contaminared coolant is Skimmed from the surface Emulsion cleaning system for tramp oil removal (ca. 98,5%) and filtering of particles, capacity 480 ltr./ h (possible also for hire)

13 More expensive methods, like separating the tramp oils and particles by centrifuge (see photo above), give an even better coolant cleaning and therefore a longer life stability. A regular costs calculation is therefore important 10 It is clear that the long life stability also depends on the product material. E.g. cast iron and cast aluminium cause additional pollution and the coolant therefore needs extra attention. To record the measurements taken, it is advised to list in writing, the results in a weekly machine report. The advantage is that the machine operator can take remedial action in time if something is not ok. Water soluble coolants need to be checked frequently and the results must analysed and corrective measures taken. Further: Ask the supplier for the safety data sheet(s) according the directive 91/155/EEC. This safety data sheet mentions all the relevant information about the product, such as: storage, transport, health and safety regulations, etc.. All metal working fluids are subject to the European chemical waste law. This includes the waste from the so-called biodegradable coolants.