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Comparison of TEGOSTAR 738 with ASTM B 23-2 alloy
(Based on US measuring techniques)
The typical stress-strain diagram of known bearing metals is curved over its whole length, whereas the stress-strain behaviour of TEGOSTAR 738 presents a marked linear range, and the J.A.E.L. point lies just below 25 % ultimate strength in com-pression, see Fig. 1. That means that TEGOSTAR 738, contrary to all other bearing metals, possesses a large elastic range, approx. 6 times larger than that of the alloy ASTM B 23-2, taking the 100°C J.A.E.L. values as reference. This results in a considerable reduction of plastic deformation under high load and high temperature. Fig. 2 shows these creep characteristics of TEGOSTAR 738 as compared with ASTM B 23-2 alloy. The creep intensity of TEGOSTAR 738 is 8 times lower. Fig. 3 shows the higher extended yield point as a function of the reduced TEGOSTAR layer thickness applied on the steel supporting body. In general, all bearing materials show this composite effect, but it can only be utilized if the material possesses reduced creep characteristics, like TEGOSTAR 738. ASTM B 23 does not give any data of the material properties regarding impact-bearing capacity. We tested this property and found that for TEGOSTAR 738 and ASTM B 23-2 alloy, it lies on an equally high level. Advantages of TEGOSTAR 738 as against ASTM B 23-2 alloy:
More than double compressive strength Greatly reduced creep intensity Longer service life of the friction bearings Higher utilizable compressive strength due to reduced layer thickness of the
bearing metal High impact-bearing capacity Suitability for all application ranges Environmentally compatible alloy without lead, cadmium, nickel and arsenic
Fig. 1: Chemical composition and physical properties of TEGOSTAR 738 and ASTM B 23-2 alloy
Tin
An
tim
on
y
Co
pp
er
Zin
c
Silv
er
20
C
100
C
20
C
100
C
20
C
100
C
20
C
100
C
Deg
F
Deg
C
Deg
F
Deg
C
Deg
F
Deg
C
TEGOSTAR 81,3 12,0 6,0 0,6 0,1 7,35 12660 7020 11840 6530 19300 10300 26 14 458 235 680 360 970 540
ASTM B23-2 89,00 7,5 3,5 7,39 6100 3000 3350 1100 14900 8700 24,5 12 466 241 669 354 795 424
Temp. of Complete
Lique-faction
Proper Pouring Temp.
Sp
ecif
ic G
ravi
ty
Alloy Grade
Yield Point, psiBrinell
HardnessMelting Point
Johnson`s Apparent Elastic
Limit, psi (J.A.E.L.)
Ultimate Strength in Compression,
psi
Specified Nominal Composition of Alloys, percent
Fig. 2: Creep characteristics of TEGOSTAR 738 and ASTM B 23-2 Fig. 3: Higher extended yield point of TEGOSTAR 738, as a function of the reduced
layer of bearing metal applied on steel
0
1
2
3
4
5
6
Time, sec
Load 15 MPa
Temperature 100°C, 212 F
100.000 500.000 1.000.000
ASTM B23-2
TEGOSTAR
Cre
ep d
efor
mat
ion,
%
0,5 2,5 4,5 6,5
TEGOSTAR layer thickness, mm
7000
14000
21000
28000
Ext
ende
d Y
ield
, ps
i Temperature: 100 C, 212 F
Remarks on the US measuring techniques
In the U.S.A., the ASTM standard is valid. There are basic values and measuring techniques for representing material data, which differ from European standards. In Europe, for example, the permanent elongation limit or extended yield point, respectively, is usually defined at an elongation of 0.2 %. According to ASTM the corresponding yield point lies at an elongation of 0.125 %. The compressive strength is defined at a linear compression of 50 %, the corresponding ultimate strength in compression according at a linear compression of 25 %. The usual unit is psi. 1 psi = 0.0068948 N/mm² . The J.A.E.L. value (Johnson's Apparent Elastic Limit) usual in the U.S.A. is explained in the sketch below for torsional strain. It applies analogously to tensile and compressive strain. Johnson's Apparent Elastic Limit (J.A.E.L.) uses the straight line of a deformation, which is, for example 2/3 greater than the deformation measured, and puts it as a tangent line against the measured deformation curve. The measured linear deformation is given with MN/0M. The ascending gradient of 0Q is based on a deformation value which is by 2/3 higher, i.d. NQ = 0.66 MN. The parallel line to 0Q is 01Q1
