Long-Life Bearings for Engine Accessories

Transcription

1 Long-Life Bearings for Our next-generation bearings for engine accessories highly reliable and durable against premature white structure flaking. New! Patent approved

2 Long-Life Bearings for ow can we solve the problem with white structure flaking? Positioning and applications of high chrome steel material Engine accessories for automobiles need to be highly durable and reliable. Bearings for engine accessories used under harsh conditions may generate white structure flaking. White structure flaking. mm Surface origin-type flaking Dust-contaminated environments Long-life bearings Sub-surface origin-type flaking Clean environments White structure origin-type flaking Environments where hydrogen is apt to enter the bearing steel Close-up of white structure flaking Prevention of foreign matter contamination Material Carburized steel eat treatment Strengthening Material Reduction of nonmetallic intermediate Strengthening of bearing steel Grease Material NSK bearings for engine accessories will solve the problem. NSK has ascertained the cause of white structure flaking with our state-of-the-art technologies. To solve the problem, we have developed new long-life bearings for engine accessories utilizing AB grease and high chrome steel material. The new bearings are durable against white structure flaking, and offer excellent durability against seizure and rust, meeting vehicle needs well into the future. <Durability against white structure flaking> µm Sealed-clean bearings for T/M Four-row, sealed tapered roller bearings Optimization of material ingredients NSJ Cost reduction Dust-resistant bearing New TF bearings γ R control TF bearing Optimum ingredients Carbonitriding Strengthening of solid solution by nitrogen i-tf bearings Special heat treatment UR treatment Super-TF bearings Mass-produced steel Control of particle distribution of nonmetallic intermediates Z-steel EP-steel igh purification Reduction of O in steel Reduction of impurities Specially melted steel VIM-VAR Electrical conductivity added AB grease igh reliability applications Airplanes applications Increase of chromium quantity Optimization of chromium quantity igh reliability applications SJ Steel ES Steel AB Grease More than twice as durable as conventional grease igh chrome steel material Compared with SUJ, Four times more durable with SJ Ten times more durable with ES Newly designed AB grease and high chrome steel Long-Life Bearings for

3 Mechanism of white structure flaking and preventive measures to be taken What are the causes of white structure flaking? Long-Life Bearings for NSK eliminates the causes of white structure flaking. igh surface pressure Micro-slip Water Vibration Formation of a new surface at the area of rolling contact Solutions <Catalyst of new surface formation> Thickness of grease film Generation of hydrogen ions caused by tribo-chemical reaction Static electricity generated between the pulley and belt discharges between the ball and ring, accelerating the generation of hydrogen, which is caused by the decomposition of grease. Intrusion and diffusion of hydrogen atoms into the steel Formation of white color structure Prevention of metallic contact by ensuring a solid grease film Electric conductivity effects of grease Inhibition of hydrogen intrusion/diffusion Stable base structure for hydrogen Prevents metallic contact by ensuring a solid film of grease (oil film). Prevents static electricity from being generated between the pulley and belt by energizing the bearing at all times. Solutions Inhibits intrusion and diffusion of hydrogen by reducing abrasion through fine dispersion of highhardness chromium carbide. Prevents white etching constituents from forming by controlling diffusion (movement) of carbon atoms. AB grease AB grease combined with nanoscale carbon particles helps solve the problem. Newly designed AB grease and high chrome steel Long-Life Bearings for igh chrome steel material igh chrome steel, resistant to white structure flaking, also helps solve the problem. Generation of white structure flaking White structure flaking Flaking patterns of bearings are largely classified into sub-surface origintype flaking in clean environments and surface origin-type flaking in waterand dust-contaminated environments. White structure flaking is a subsurface origin-type, not caused by a defect in inner materials such as nonmetallic intermediates, but by intrusion of hydrogen into the bearing steel generated by tribo-chemical reaction, which in turn forms a white etching constituent and generates flaking sooner than the end of the calculated operational life. Close-up of white structure flaking seen in commercially available bearings Conceptual diagram of hydrogen intrusion Grease film Rolling element Fixed ring gas Reactional film ydrogen release speed, ppm/sec Data set. Measured amount of hydrogen in bearings without flaking Temperature, C ydrogen release speed, ppm/sec Data set. Measured amount of hydrogen in bearings with flaking Temperature, C Data sets and show the measured amount of hydrogen that intruded into the bearing after durability tests. Intrusion of hydrogen was seen in the bearing with flaking, with a peak at around 3 C. Intrusion of hydrogen was not found in the bearing without flaking, and no hydrogen peak was detected. 3

4 AB grease and high chrome steel ensure long life and resistance to white structure flaking. What are the performance characteristics of AB grease and high chrome steel? Long-Life Bearings for Together they ensure unprecedented long life. AB Grease An innovative grease, combined with nanoscale carbon particles, with electric conductivity. AB grease enables bearing use in environments up to C by improving property stability at high temperatures. AB grease contains no environmentally harmful substances. Furthermore, with electric conductivity, AB grease is more than twice as durable against white structure flaking. igh Chrome Steel igh chrome steel enhances the bearing s durability against white structure flaking. The operational life of SJ is four times longer than SUJ, while ES lasts ten times longer than SUJ. In addition, high chrome steel is excellent for dimensional stability and can be used in hightemperature environments. Four types of bearings for automobile engine accessories Bearing specification Bearing material Grease Current specification SUJ Current grease ➀Standard specification SUJ AB ➁igh-temperature specification SJ3 AB ➂Long-life specification SJ AB ➃Ultra long-life specification ES ➀ Standard specification AB grease-packed bearings enhance durability against white structure flaking. They are recommended as standard specification bearings for conventional uses of engine accessories. ➁ igh-temperature specification igh heat-resistant bearings with SJ3, which solve problems with SUJ in hightemperature environments, are recommended for engine accessories used at high temperatures, up to C. <Characteristics of SJ3>. Less softening during tempering due to dimensional stabilization treatment. Less softening in high-temperature environments 3. Excellent dimensional stability ➂ Long-life specification SJ has longer operational life than SUJ and enables longer operational life than bearings with standard specifications. This specification is recommended when downsizing of bearings is required. ➃ Ultra long-life specification ES provides maximum durability against white structure flaking. This specification is optimal for bearings for engine accesories.

5 Long-Life AB Grease Measured durability data of AB grease Long-Life Bearings for Prevention of metallic contact Nanocarbon forms a more solid grease film. The grease utilizes a thickener with stability (hardening/softening with time) at high temperatures. Electric conductivity Combined with electrically conductive substances, static electricity is prevented from charging between the pulley and the belt. Results of AB grease electric conductivity Electric resistance Constant voltage power supply Slip ring Measuring instrument Test bearing Bearing: (φ φ 7 mm) min, F r = F a = 9.N, 3 C Electric conductivity: 93.% Electric conductivity:.% AB grease Current grease.9 Test bearing: 33 equivalent P/C:. Speed: min Before countermeasures were taken AB 3.9 Test bearing: 3 P/C:.3 Speed: 7 min Rotational fluctuation: ±.% Results of white structure flaking durability test (grease) AB 3 Measurement results for EL oil film Load: 7N Speed:. m/s Temperature: C Grease supplied thickness:. µm) Grease supplied thickness:. µm) AB Current grease After one minute thickness:. µm) After one minute thickness:. µm) The oil film of AB grease is more than. times thicker than that of conventional greases Representative properties of AB grease Item AB Test method Appearance Black, buttery Thickener Diurea Base oil Ether oil Kinetic viscosity of C base oil mm /sec C 3 JIS K3 Worked penetration JIS K (.3) C, W Dropping point C or higher JIS K (.) Copper corrosion Passed JIS K (.B) C, h Evaporation %, C, h. JIS K (.B) Oil separation %, C, h.3 JIS K (.7) Oxidation stability. JIS K (.) MPa, C, h Worked stability 33 JIS K (.) C, W Water washout resistance %, 79 C, h. JIS K (.) Low-temperature Activated.3 torque N m Rotations. JIS K (.) Rust test.% NaCI,, ASTM D73 C, h, %R.9 Test bearing: 33 equivalent P/C:.7 Speed: min Bearing temperature: 7 C AB 3 3 Blending nanoscale carbon particles into AB grease creates electric conductivity, eliminating static electricity generated between the belt and the pulley. Since static electricity is not charged inside the bearing, discharge phenomena is reduced and decomposition of the grease is inhibited, which in turn prevents the generation of hydrogen. As a result, long-life AB grease-packed bearings resist white structure flaking far better than conventional bearings and are also more resistant to seizing..9 Test bearing: 3 P/C:. Speed: min Bearing temperature: 3 C Results of seizure durability test (grease) AB 7

6 Long-Life igh Chrome Steel Improved wear resistance Finely dispersing and precipitating, high-hardness chromium carbides inhibit abrasion, preventing new surface formation, and reduce tribo-chemical reactions (generation of hydrogen). Inhibited hydrogen diffusion igh hydrogen trapping energy. White structure flaking durability L, h Low Alternator test Chromium quantity No flaking generated Test bearing: 33 equivalent P/C:. Speed: min igh Stabilized carbide and base structures Inhibits diffusion of carbon in steel, and controls formation of white etching areas. Compared with SUJ, SJ and ES have longer operational lives due to their abrasion resistance, hydrogen intrusion/diffusion inhibition, and stabilized carbide and base structures. White structure flaking durability L, h Low ydrogen charging test No flaking generated Chromium quantity Relationship between chromium quantity and white structure flaking durability Test bearing: Sample of a thrust bearing P/C:. Speed: min igh Measured durability data of SJ and ES.9 Test bearing: 33 equivalent P/C:. Speed: min Grease: Before countermeasures taken 3 Long-Life Bearings for SUJ SJ ES.9 Test bearing: 3 P/C:.3 Speed: 7 min Rotational fluctuation: ±.% Grease: Before countermeasures taken Results of white structure flaking durability test (material) SUJ SJ ES 3 ydrogen diffusion rate, ppm/h Conceptual illustration of the hydrogen trapping function SUJ: Weak trapping function Fast hydrogen diffusion ydrogen may accumulate in stress concentration areas such as micro damages igh chrome steel: Strong trapping function Slow hydrogen diffusion ydrogen cannot accumulate easily ydrogen diffusion rate SUJ SJ ES Rate of change, % Seizure PV value, GPa m/s..... Dimensional stability of each material ES SJ SUJ (usual heat treatment) Left at 7 C Seizing test for each material SUJ SJ ES.9 Test bearing: 33 equivalent P/C:.7 Speed: min Bearing temperature: 7 C SUJ + Current grease SJ + AB grease 3 By using high chrome steel as a bearing material to counter white structure flaking, wear resistance is improved, tribo-chemical reactions due to wear are reduced, intrusion/diffusion of hydrogen (hydrogen trapping effect) is inhibited, and carbides and base structure are stabilized (movement of carbon atoms is inhibited at the time of white etching area formation). SJ and ES provide longer life against white structure flaking and exhibit higher durability against seizure than conventional materials..9 Test bearing: 3 P/C:. Speed: min Bearing temperature: 3 C SUJ + Current grease SJ + AB grease Results of seizure durability test (material) 3 Newly designed AB Grease and igh Chrome Steel Long-Life Bearings for 9