ECOLOGICAL LUBRICANTS FOR FORMING AND CUTTING APPLICATIONS

Transcription

1 ECOLOGICAL LUBRICANTS FOR FORMING AND CUTTING APPLICATIONS A. IGARTUA, J. BARRIGA, J. PÉREZ TEKNIKER, Otaola 2, 26 Eibar, SPAIN; L. MUNTADA, P. NAVÍO BRUGAROLAS, Polígono Cova Solera, 8191 Rubi, SPAIN; P. LEHTO, W. KÖNIG, G. HAGG, A. ZABALA, E. HEINKINEN, J. DAHLSTEN SUMMARY Ecological lubricants have been developed in this work to be used in different forming and cutting processes. In the formulation biodegradable and non-toxic compounds have been considered. The ecotoxicity of final lubricants has been measured through Daphnia Magna tests. For a first screening some standard Ball on Disc tribological tests have been performed. In a Falex Tapping Torque machine Rotational Drawing tests have been made ready to simulate the drawing process and evaluate the efficiency of forming fluids. The final validation of the lubricants was performed through field tests. Fluorinated products showed good properties for drilling / collaring (forming) application, but at prohibitive prices. For pipe bending a successful ecological lubricant has been obtained based on organic acids soap and esters. For deep drawing application a lubricant to be used diluted in water was proved to perform properly. It was formulated with native esters, sulphur additives and potassium soap. Keywords: lubricants, ecological, forming, cutting, tribotesting. 1 INTRODUCTION Lubricant plays a key role in cutting and forming processes and mineral oil containing chloro-paraffines are actually used. Whereas the performance of the lubricant is good, from environmental point of view, it has some drawbacks: toxicity, pollution, skin irritating. In the present work new ecological lubricants have been developed for these applications. Their performances have been compared by means of tribological and field tests. Toxicity of new products has also been measured. 2 LABORATORY TESTS Basic tribological characterisation of new lubricants has been performed through Ball on Disc tests (point contact). Application oriented testing has also been applied: Ring on Disc (surface contact), Cylinder on Disc (line contact) and Rotational Drawing tests (Figure 1). A testing procedure has been defined at Tekniker to test lubricants under drawing conditions with a Falex Tapping Torque machine. This test allows measuring the torque during the drawing operation and so we can evaluate the efficiency of the fluid. Toxicity of new lubricants has been measured through Daphnia Magna Test (OECD 22). 3 TUBE DRILLING AND FORMING The T-Drill method of pipe branching is applicable to almost every malleable material including stainless steel, Cu-Ni, aluminium alloys and copper. This method combines drilling and forming operations (Figure 2). By means of this technique one simple weld joint instead of three is required. Figure 1:Rotational-Drawing test device Figure 2: Scheme of drilling/forming process. Forming of T-junctions in stainless steel tubes demands very high performances for the lubricant. More than 33 new products have been developed by BRUGAROLAS for drilling/forming application avoiding the presence of environmental hazardous components such as chlorine compounds. Some fluorinated pastes have been formulated.

2 3.1 Tribotesting Pre-screening basic laboratory tests were performed in order to have a closer idea about the wear behaviour of new lubricants. Ball on disc test with a ceramic ball and steel disc produces abrasive wear (Figure 3). In general terms chlorinated lubricants show better performances than ecological ones. 1,9,8,7,6,5,4,3,2,1 TD CHLORINE 4 TD CHLORINE 2 TD CHLORINE 1 BALL ON DISC Disc: Polished Steel / Ball: Silicon Nitride Conditions: 25ºC / 11.88mm /.9m/s / 4.4lb /.8GPa / 7rpm / 165min µ average µ stable ECO PASTE TD1 ECO PASTE TD2 ECO PASTE TD3 ECO PASTE TD4 ECO PASTE TD5 ECO PASTE TD7 ECO PASTE TD8 ECO PASTE TD6 ECO PASTE TD9 ECO PASTE TD1 ECO PASTE TD11 ECO PASTE TD12 ECO PASTE TD13 ECO PASTE TD14 ECO PASTE TD15 ECO PASTE TD16 ECO PASTE TD17 ECO PASTE TD19 ECO PASTE TD2 ECO PASTE TD22 BIO PASTE TD1 BIO PASTE TD2 BIO PASTE TD3 BIO PASTE TD5 BIO PASTE TD4 Figure 3: Ball on Disc tests with drilling/forming lubricants 3.2 CNC and field tests It is possible to adapt the drilling/forming tooling to a CNC machine. An advantage of this way of testing is to control more the real process (temperature, mechanism of wear, current consumption ). The first thing observed is that the performance of the ecological lubricants (as Ecopaste 1) when forming copper is similar to chlorine lubricants, but the real challenge and the scope of this work is to reach a proper solution for stainless steel. The Fluorinated 1 lubricant followed by Ecopaste 15 have similar behaviour than chlorine lubricants in the test performed in the CNC Machine. T-DRILL has developed a methodology to evaluate the wear of the tools in their machines. Results of their tests are summarised in Figure 4. A 8, 7, 6, 5, 4, 3, 2, 1,, SUMMARY RESULTS T-DRILL TEST TD CHLORINE 1 TD CHLORINE 3 ELM-243 ELM-244 ECOPASTE TD (3) ECOPASTE TD (4) ECOPASTE TD (5) ECOPASTE TD (6) ECOPASTE TD (7) ECOPASTE TD (8) ECOPASTE TD (9) ECOPASTE TD (1) ECOPASTE TD (11) ECOPASTE TD (12) ECOPASTE TD (13) ECOPASTE TD (14) ECOPASTE TD (15) ECOPASTE TD (16) ECOPASTE TD (17) ECOPASTE TD (18) ECOPASTE TD (19) ECOPASTE TD (2) ECOPASTE TD (21) ECOPASTE TD (22) ECOPASTE TD (23) BIOPASTE TD (1) BIOPASTE TD (2) BIOPASTE TD (3) BIOPASTE TD (4) BIOPASTE TD (5) BIOPASTE TD (6) BIOPASTE TD (7) FLUORINATED 1 FLUORINATED 2 Figure 4: Current consumption in T-Drill tests The addition of a 1% of solid lubricants such as CO 3 Ca, MoS 2, (PO 4 ) 2 Ca 3, ZnO, Amine Cianurate or organic molybdenum compounds over mineral base oil with hydrocarbon wax thickener and sulphured synthetic ester and amine phosphate additives, does not improve the current consumption during the drilling/forming application. The thickener based on a hydrocarbon wax gives slightly lower current consumption than the urea compound. The increase of concentration of overbased sulphonates +S additives slightly affects the current consumption, but the increase of concentration of sulphured natural ester + amine phosphate decrease the current consumption significantly. Fluor derivatives (fluorinated polyeter compounds) have the best performance of the environmentally friendly pastes, similar to chlorinated lubricants. Results obtained in the CNC Machine correlate very well with those obtained in the field tests carried out by T-DRILL. 3.3 Environmental properties The addition of Organic Mo or MoS 2 does not modify the toxicity behaviour, but with other solid lubricants more toxic effect is observed in Daphnia Magna tests. When using urea compound as thickener or without thickener we obtain slightly lower toxicity than with Hydrocarbon wax. Differences are not big. When increasing the concentration of Overbased sulphonates +sulphur, decrease the toxicity. The additive sulphurised olefine gives lower toxicity than the sulphurised synthetic ester. It is not possible to measure the ecotoxicity of Fluorinated lubricants because are totally insoluble, but they are assumed to be less toxic than chlorinated products. Products ELM 243, Ecopaste 5, 6, 7, 8, 11, 13, 15 and Biopaste 4 are practically non-toxic (> mg/l) for Daphnia Magna, as required by several Ecolabels. 4 PIPE FORMING, BENDING AND CUTTING Several processes are involved in pipe manufacturing from a sheet of metal to the final product. So it is important that all the lubricants used were easy to clean. Eight lubricants have been formulated by BRUGAROLAS for pipe bending applications and 3 for cutting applications. Some are formulated with highly refined mineral oil, esters, surfactants and sulphur additives and made washable. Ecopipe bending 4 and Ecopipe Forming Synthetic have been obtained based on organic acids soap and esters. Ecopipe Cutting 1 and Ecopipe Forming Milky 1 are formulated with rapeseed oil, sulphur and phosphorus additives, the Ecopipe Cutting 2 with organic acid soap and esters, and the

3 Ecopipe Cutting 3 is based on rapeseed oil, sulphur and phosphorus additives. 4.1 Tribotesting The friction coefficient in abrasive conditions of Eco Pipe Bending 4 is very low (~.3) near half the value of this parameter for the Reference Bending 1 in the same testing conditions (Figure 5),6,5,4,3,2,1 BALL ON DISC Disc: Polished Steel / Ball: Silicon Nitride Conditions: 25ºC / 2.68mm / 3.2m/s / 3lb / 1.5GPa / 15rpm / 165m µ average µ stable REF. BENDING 1 ECO PIPE B 1 ECO PIPE B 2 ECO PIPE B 3 ECO PIPE B 4 Figure 5: Coefficient of friction of bending lubricants Some cutting fluids were tested in the SRV tribotester with the material normally used in this application: a sheet of HSS (AISI 34). Very strong abrasion was observed in the test performed with Reference Cutting oil, but only moderate occurs with Ecopipe Cutting 3 lubricant. Also the coefficient of friction was lower with the new ecological fluid (Table 1) Lubricant CUTTING ECO PIPE CUTTING 3 Friction Sheet Wear (mg) Wear mechanism Very strong abrasion/adhesion Moderate abrasion Table 1: SRV tests For the forming application some water-based fluids have been studied. In standard abrasive Ball on Disc tests it can be seen that one of the new lubricants presents low friction and lower wear than the others (Table 2). Lubricant Friction Wear (mm) Ball Disc New Forming 1,381 2,155 2,18 New Forming 2,35,5,168 Reference Forming 1,159 1,55 1,155 Reference Forming 2,159,5,773 Table 2: Ball on disc tests The lubricant New Forming 2 have very good friction and wear properties for this application as water base fluid lubricant. The previous New Forming 1 had very bad properties: high wear and friction in tests. Ecopipe Bending 4 has very good friction behaviour as pure oil. For cutting applications 3 lubricants have been formulated: Ecopipe Cutting 1, 2, 3. The Ecopipe- Cutting 3 have good properties in NORMA cutting operations and in the test carried out in oscillating conditions (see Table 1). 4.2 Field Tests More than bendings are possible to carry out with the oil Ecopipe Bending 4, a synthetic product water-soluble (Table 3). The oil is very easy to clean and the number of oil applications can increase. The wear decreases when increasing the number of bendings because the contact pressure decrease. The New Forming 1 and 2 lubricants have been tested in JARO. The performance of New Forming 1 was good at the beginning but later the performance decrease. The performance of New Forming 2 is much better. This relationship has been observed at the laboratory. 4.3 Environmental properties Ecopipe Bending 4 lubricant is practically non toxic (569 mg/l) in the test of Daphnia Magna as required by several Ecolabels. The toxicity has been reduced 5 times in relation to the previous used lubricant Reference Bending 1 (99 mg/l). The previously used Reference Forming 1 and 2 are toxic (1.74 and mg/l resp in Daphnia Magna test). New lubricants for this application New Forming 1 and 2 are practically non toxic (11.34 and 114 mg/l resp.). Ring Oil Reference Bending 1 Oil Ecopipe Bending bending 1841 bending 4 bending 792 bending bending Wear 1 st.42gr/tube.231gr/tube.18gr/tube.87gr/tube.64gr/tube Wear 2 nd.131gr/tube.77gr/tube.45gr/tube.38gr/tube.37gr/tube Table 3: Field bending tests in NORMA 5 DRAWING APPLICATIONS Nine lubricants have been developed by BRUGARO- LAS for this application. The results from these lubricants have been compared with 3 references: Reference MP (normal steel and normal pressure), Reference LP (low pressure) Chlorine HP (hard operations, combined with petroleum). The biolubricants are formulated with native or biodegradable esters and sulphur-phosphorus additives and the other lubricants are formulated without chlorine, with highly refined mineral oil, esters and sulphur additives. All the formulated alternatives are water-washable.

4 Brugarolas has developed two more lubricants for deep drawing application to be used diluted in water: Bio Deep Drawing 2 (BDD2) and Bio Deep Drawing 2 modified, BDD2M (improving antifoaming and antiwear behaviour). Both lubricants are formulated with native esters, sulphur additives, potasium soap and both are water-soluble lubricants. Their behaviour has been compared with actual lubricant: Reference Stala Efficiency (%) Stainless Steel 5.1 Tribotesting Rotational Drawing tests have been performed in laboratory to screen lubricants. In the drawing simulated test, the highest efficiency is showed for the Deep Drawing 2 as alternative for the Reference MP. Bio Deep Drawing 3 is selected for this application because is more environmentally friendly and his efficiency is a 6% higher than the Reference (Fig. 6) MP Efficiency (%) Normal Steel DRAWING 2 DRAWING 3 BIO DRAWING 3 Figure 6: Rotational Drawing tests The efficiency of the Bio Deep Drawing 1, based on native esters and sulphur phosphorous additives is 6% higher than the Reference LP. This lubricant is a clear alternative for Reference LP (Figure 7). 18 Efficiency (%) SS+WP LP DRAWING 1 BIO DRAWING 1 Figure 7: Rotational Drawing tests The efficiency of all the substitutes of Chlorine HP have lower efficiency. In the field Chlorine HP is diluted in petroleum, but the efficiency when diluted is also higher than the lubricant substitutes. It is very difficult to find an environmentally friendly substitute for high pressure deep-drawing application (Figure 8). The test at the Tapping Torque machine with waterbased fluids shows that the efficiency of the deep drawing increase, when increasing the concentration of lubricant. From 17% to 3% concentration of BDD2M allow to increase the efficiency a 4%. At the same concentration the efficiency of Reference Stala is a bit higher (Figure 9) CHLORINE HP DRAWING 4 DRAWING 5 DRAWING 6 Figure 8: Rotational Drawing tests STALA 17% Efficiency (%) SS+Blue P BIO DRAWING 2 MOD 17% BIO DRAWING 2 17% Figure 9: Rotational Drawing tests DRAWING 7 BIO DRAWING 2 MOD 3% 5.2 Field tests BDD2 reduces significantly the dirt accumulating to draw ring (with Reference Stala, the operator has to wipe dry the draw ring after every cycle to keep up with the quality). Slipping properties are excellent, the transition line is much lower than with Reference Stala. This means that the material flows better and stretches less in process. The work piece is much cleaner, resulting less work in later steps of the production process. 5.3 Environmental properties Ecological products, less harmful for the environment have been achieved (see Table 4). TEST SUBSTANCE EC5(mg/l)Daphnia Reference MP 6.11 DRAWING DRAWING BIO DRAWING Reference LP 5.25 DRAWING BIO DRAWING Chlorine HP 5.46 DRAWING DRAWING DRAWING DRAWING BIO DD % BIO DD 2 MOD 16-18% 427 Table 4 Daphnia Magna Tests

5 The lubricant BDD2M is practically non toxic (>mg/l) in Daphnia Magna as required by several Ecolabels. 6 CONCLUSIONS For drilling/forming application a non-toxic solution has been found. Fluor derivatives a performance similar to chlorinated lubricants. The problem is the high price of these products, which will prevent companies from using them. For pipe bending, forming and cutting applications completely successful solutions have been achieved. Ecopipe Bending 4 has been obtained based on organic acids soap and esters. For severe, high-pressure deep drawing applications no ecological alternative has been found. For normal or low pressures harmless alternatives are been formulated. Also for sink manufacturing in stainless steel a good water soluble product has been formulated. 7 S [1] Metalworking fluids, Ind. Lubr. and Trib., 1995, 47, (3), [2] Alternative lubricant base stocks, Ind. Lubr. and Trib., 1997, 49, (2), [3] Lubricant additives, Ind. Lubr. and Trib., 1997, 49, (1), [4] T. W. Dicken: Biodegradable Greases, Ind. Lubr. And Trib., 19, 46, (3),3-6.