DIN 1626 Welded Circular Unalloyed Steel Tubes Subject to Special Requirements
DIN 1629 Seamless Circular Unalloyed Steel Tubes Subject to Special Requirements
DIN 17175 Seamless Tubes of Heat-Resistant Steels
Steel Grade Symbol Type of deoxidiz
-ation
Chemical Composition (cast analysis) %
(max unless otherwise specified)
C Si (1) Mn P S N (2)
St 37.0 R 0.17 - - 0.040 0.040 0.009(3)
St 35.8 - 0.17 0.10-0.35 0.40-0.80 0.040 0.040 -
NOTES:
(1) The minimum Si content is allowed to fall below 0.10%, when the steel is aluminium-killed or vacuum-deoxidized. 
(2) A content in excess of the maximum value stated is permitted if a P content less than the maximum specified by
0.005% P per 0.001% N is observed. However the N content shall not exceed a value of 0.012% in the cast analysis
and 0.014% in the product analysis.
(3) The specified value does not apply if the steels are supplied with the RR (instead of R) type of deoxidization.
R=killed, including semi-killed
RR= fully killed
Amounts by which the chemical composition in the product/sample analysis may deviate 
from the limiting values applicable to the cast analysis.
Element St 37.0
Allowable Deviation Amount %
St 35.8 
Upper Limits Quoted in Cast Analysis Allowable Deviation
Amount (2) %
C   0.02   0.24 0.02
Si   -   0.35 0.03
Mn   -   1.00 0.04
P   0.010   0.040 0.010
S   0.010   0.040 0.010
N   0.001(1)   - -
NOTES:
(1) A content in excess of the maximum value stated is permitted if a P content less than the maximum specified by
0.005% P per 0.001% N is observed. However the N content shall not exceed a value of 0.012% in the case analysis
and 0.014% in the product analysis (this does not apply to the RR type of deoxidization).
(2) In a cast the deviation of an element in a sample analysis is permitted to be below the minimum value or only 
above the maximum value of the range stipulated for the cast analysis, though not both at the same time.
Steel Grade Symbol Upper Yield Stress ReH Tensile
Strength
Rm
Elongation after  Impact 
for Wall thicknesses, in mm Fracture A5 Strength
ReH£16 16<ReH£40 40<ReH£60 Longitudinal Transverse Transverse
Min   N/mm2 Min   % Min  J
St 37.0 235 225 215 350(1) -480  25 23 -
St 35.8 235 225 215 360-480 25 23 34
NOTE:
(1) For cold finished tubes in the NBK condition, minimum values of tensile strength lower than this value 
by 10N/mm2 is permitted.