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iglidur® M250 - Material data

Materials table

General features Unit iglidur® M250 test method
Density g/cm³ 1,14
Colour Anthracite
Max. humidity absorption at 23°C/50% R. H. % weight 1,4 DIN 53495
Max. water absorption % weight 7,6
Coefficient of surface friction, dynamic, against steel µ 0,18 - 0,40
PV values max. (dry) MPa x m/s 0,12

Mechanical properties
Bending E-module MPa 2.700 DIN 53457
Tensile strength at +20 °C MPa 112 DIN 53452
compressive strength MPa 52
Maximum recommended surface pressure (20° C) MPa 20
Shore D hardness 79 DIN 53505

Physical and thermal properties
Max. long term application temperature °C +80
Max. short term application temperature °C +170
Lower application temperature °C -40
Heat conductivity [W/m x K] 0,24 ASTM C 177
Coefficient of thermal expansion (at 23° C) [K-1 x 10-5] 10 DIN 53752

Electrical properties
Specific forward resistance Ωcm > 1013 DIN IEC 93
Surface resistance Ω > 1011 DIN 53482
'Table 01: Material Data


Figure 01: Permitted pv-values for iglidur® M250


Figure 01: Permitted PV values for iglidur® M250 bearings with 1 mm wall thickness in dry operation against a steel shaft, at 20°C, installed in a steel housing.

X = Surface speed [m/s]
Y = Load [MPa]


 
The self-lubricating plain bearing made of iglidur® M250 distinguishes itself through its impact strength, vibration dampening and wear resistance. They prove to be particularly good under stresses in which the vibration dampening of the bearing is called for, for instance in sports equipment and packaging machines. As they are also in a position to tolerate dirt, they are ideal for use in agricultural machinery and garden equipment.


Figure 02: Maximum recommended surface pressure dependent on the temperature (20 MPa to +20 °C)

X = Temperature [°C]
Y = Load [MPa]
Figure 03: Deformation under load and temperatures

X = Load [MPa]
Y = Deformation [m/s]

Mechanical properties

Maximum recommended surface pressure represents a mechanical material parameter. Tribological conclusions cannot be drawn from it. With increasing temperatures, the compressive strength of iglidur® M250 plain bearings decreases. Fig. 02 clarifies this connection.


 

 

 
iglidur® M250 bearings have a maximum recommended surface pressure of 20 MPa. Compared with other iglidur® materials, the iglidur® M250 bearings are very elastic. By this elasticity they can yield very well, but reset themselves again. A plastic deformation is negligible up to the maximum recommended surface pressure.


Maximum surface speed

m/s Rotating oscillating Linear
Constant 0,8 0,6 2,5
Short-term 2 1,4 5
Table 02: Maximum surface speeds

Permitted surface speeds

As a standard, iglidur® M250 is manufactured as a thick-walled bearing. iglidur® M250 is best suited for low to medium surface speeds. The maximum permitted surface speeds in the dry operation are 0.8 m/s (rotating) and 2.5 m/s (linear) respectively. In practice these limit values are not always reached due to interactions.


Temperature limits

iglidur® M250 Operating temperature
Lower - 40 °C
Upper, long-term + 80 °C
Upper, short-term + 170 °C
Secure axially in addition + 60 °C

Table 03: Temperature limits for iglidur® M250

Temperatures

The short-term permitted maximum temperature is 170° C. The iglidur® M250 bearings should however be exposed to this temperature only without any more load. The long-term permitted application temperature lies at 80°C. Here you'll find the wear limit, thus also the temperature at which the wear increases disproportionately. An additional securing is recommended at temperatures higher than +60°C.
 


Figure 04: Coefficients of friction dependent on the surface speed, p = 0,75 MPa

X = Surface speed [m/s]
Y = Coefficient of friction μ
Figure 05: Coefficients of friction dependent on the load, v = 0,01 m/s

X = Load [MPa]
Y = Coefficient of friction μ

Friction and wear

The coefficient of friction µ of a bearing is, among other things, influenced by surface speed and load (Fig. 04 and 05).

iglidur® M250 Dry Grease Oil Water
Coefficients of friction µ 0,18 - 0,40 0,09 0,04 0,04

Table 04: Coefficients of friction for iglidur® M250 against steel (Ra = 1 μm, 50 HRC)



Fig. 07 Figure 06: Wear, rotating application with different shaft materials, p = 1 MPa, v = 0.3 m/s
 
Y = wear [μm/km]
 
A = Aluminum, hard-anodized
B = machining steel
C = Cf53
D = Cf53, hard chrome-plated
E = St37
F = V2A
G = X90

Shaft materials

Friction and wear also depend to a high degree on the reverse partner. The most favorable surface finish of the shaft for iglidur® M250 bearings is at Ra = 0.6 mm, considering the coefficient of friction. Figures 06 and 07 display a summary of the results of tests with different shaft materials conducted with iglidur® M250 plain bearings. In rotation, the shaft material plays only a relatively minor role for loads up to 2 MPa. For this reason, a suitable shaft material should be considered for high loads. These are the hardened shafts, such as CF53 or hard-chromed shafts. From Fig. 07 it becomes clear that iglidur® M250 is substantially better suited for rotation than for swivelling motion. Here it must be mentioned that in practice the vibrations acting on the bearing are often extremely high in pivoting movements. Here the iglidur® M250 can exercise its particularly dampening properties. In our test such vibrations are excluded, so that the comparison between rotation and pivoting operation amazes at first.
 

Wear in swivelling and rotating applications Fig. 07: Wear in swivelling and rotating applications with various shaft materials, with p = 2 MPa Y = wear [μm/km]
 
A = Cf53
B = hard chrome-plated
C = V2A
D = St37
 
Color blue = rotating
Color pink = oscillating
 

Medium Resistance
Alcohols + to 0
Hydrocarbons +
Fats, oils, without additives +
Fuels +
Diluted acids 0 to -
Strong acids -
Diluted bases +
Strong bases 0
+ resistant      0 partially resistant      - non-resistant
All specifications at room temperature [+20℃]
Table 05: Chemical resistance of iglidur® M250

Electrical properties
iglidur® M250 bearings are electrically insulating.

Specific forward resistance > 1013 Ωcm
Surface resistance > 1011 Ω

Chemical resistance

iglidur® M250 bearings have a good resistance against chemicals. They are resistant to most lubricants. The iglidur® M250 is not affected by most weak organic and inorganic acids.

Radioactive rays

Bearings made of iglidur® M250 are conditionally usable under radioactive radiation. They are resistant up to a radiation intensity of 1 · 104 Gy.

UV-resistant

iglidur® M250 bearings are permanently resistant against UV rays.

Vacuum

In vacuum, iglidur® A250 plain bearing degases. The relatively high humidity absorption of the bearing therefore permits the bearing to be used in vacuum only restrictedly.


Maximum moisture absorption
At +23 °C/50 % r.h. 1.4 % weight
Max. water absorption 7,5 % weight

Table 06: Moisture absorption

Effect of moisture absorption on plain bearings Diagram 10: Effect of moisture absorption
 
X = Moisture absorption [weight %]
Y = Reduction of inside diameter [%]

humidity absorption / moisture absorption

The humidity absorption of iglidur® M250 bearings amounts to about 1.4% in standard climatic conditions. The saturation limit in water is 7.5%. This should be considered according to application conditions.


Diameter
d1 [mm]
Shaft h9
[mm]
iglidur® M250
D11 [mm]
Housing H7
[mm]
Up to 3 0 - 0,025 +0,020 +0,080 0 +0,010
> 3 to 6 0 - 0,030 +0,030 +0,105 0 +0,012
> 6 to 10 0 - 0,036 +0,040 +0,130 0 +0,015
> 10 to 18 0 - 0,043 +0,050 +0,160 0 +0,018
> 18 to 30 0 - 0,052 +0,065 +0,195 0 +0,021
> 30 to 50 0 - 0,062 +0,080 +0,240 0 +0,025
> 50 to 80 0 - 0,074 +0,100 +0,290 0 +0,030

Table 07: Important tolerances for iglidur® M250 bearings according to ISO 3547-1 after the press-in.

Installation tolerances

iglidur® M250 bearings require relatively large bearing clearances for optimum performances. These ensure that the bushings work reliably even with thermal expansion and water absorption. The disadvantages of the bearing clearance are again compensated by the vibration dampening properties. The bearings are designed for press-fit in a housing with h7 tolerance. After the installation in a housing with nominal diameter, the inner diameter of the bearing automatically adjusts to the D11 tolerance. The shaft should have at least an H9 tolerance.