deva.metal Handbuch EN fÃ¼r GGB - Supresores

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4 Counter materials Counter materials The deva.metal ® sliding materials can only be used with counter material hardness of at least 180 HB. If an additional lubricant is introduced into the sliding contact, hardness values of >130 HB are also admissible. In abrasive environments, a hardened 35 HRC/45 HRC surface should be used. The ideal mating surface roughness for deva.metal ® is R a = 0.2 to 0.8 μm (obtained by grinding). Rougher surfaces are also acceptable depending on the operating conditions. To obtain the right surface roughness, it is also possible to use bushings of a suitable hardness. Hard-faced layers or galvanised protective layers (normally coated, hard-chrome and nickelplated) can be used to a limited extent. The corrosion criteria for the counter materials should be determined on the basis of the relevant operating conditions. The adjacent table provides an overview of some of the possible counter materials. Counter materials for normal applications Material No. 1.0543 1.0503 1.7225 DIN designation ZSt 60-2 C45 42CrMo4 USA AISI Grade 65 1045 4140 Counter material for corrosive applications Material No. 1.4021 1.4057 1.4112 1.4122 DIN designation X 20Cr13 X 17CrNi16-2 X 90CrMoV18 X 39CrMo17-1 Counter materials for use in sea water Material No. DINdesignation USA AISI 420 431 440B USA AISI Comparable standards GB B.S. 9 70 55C 080M46 708M40 Comparable standards GB B.S. 9 70 420S37 432S29 Comparable standards GB B.S. 9 70 F AFNOR A60-2 CC45 42CD4 F AFNOR Z20C13 Z15CN16.02 (Z70CV17) F AFNOR 1.4460 1.4462 X 4CrNiMo27-5-3 X2CrNiMoN22-5-3 329 UNS531803 318513 Z3CND24-08 2.4856 Inconel 625 Table 4.1 – Main possible counter materials polished turned V S – Specific wear ground R a 0.2 - 0.8 0.1 0.2 0.38 0.8 2.1 4.6 μm Surface roughness R a in [μm] Model representation (refering to different examinations) Figure 4.1 – Effect on counter material surface roughness on micro wear of composite 12
deva.metal ® maintenance-free 5 Fits and tolerances In order to ensure satisfactory performance, the bearing outside diameter, bearing bore, shaft diameter and the bore of the housing should be finished to the recommended limits. Interference fit deva.metal ® bearings should be installed into the housing with an interference fit between the outside diameter of the bush and the bore of the housing. Housing bore The housing bore should be finished to H7 tolerance with a maximum surface finish of R a = 3.2 μm. Housing bore Bearing outer diameter Table 5.1 – Tolerances Tolerance H7 r6 Outer diameter of bearing Sufficient close fitting of a bearing depends on its wall thickness and the operating conditions. Additionally the bearings must be mechanically protected against displacement or rotation, if they operate continuously at temperatures above 150 °C or if they have to absorb axial loads (see Fig. 5.1). Clearance The required assembled clearance for deva.metal ® bearings operating under dry conditions depends upon the bearing load and the operating temperature. In order to ensure satisfactory operation it is essential that the correct running clearance is used. Under dry running conditions any increase in the clearance recommended will result in a proportional reduction in performance. Bearing bores are manufactured pre-finished. Consider the contraction of the bearing bore when the bearing is installed into the housing. The inner diameter of the bearing is reduced by approx. 75 to 95% of the actual excess dimension by press fitting Fig. 5.1 – Mechanical fixation of deva.metal ® bushings the bearing into the housing. deva.metal ® sliding bearings are manufactured in such a way that finishing work is not necessary for normal installation after assembly. The resulting contraction is already taken into consideration during production. Fits and Tolerances Application Operating conditions Shaft tol. Bearing inner-Ø: Tolerance machined before installation Bearing inner-Ø: Tolerance machined after installation Mechanical equipment Normal op.: Temp.100 °C sep.det. separate determination separate determination Precision allowances h8 D7 E8 Table 5.2 – Tolerances deva.metal ® 13
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