CHEMICAL COMPOSITION % max
Steel grade	C	Si	Mn	P	S	Nb or V
STC 370	0.25	0.35	0.30-0.90	0.04	0.04	-
STC 440	0.25	0.35	0.30-0.90	0.04	0.04	-
STC 510 A	0.25	0.35	0.30-0.90	0.04	0.04	-
STC 510 B	0.18	0.55	1.5	0.04	0.04	-
STC 540	0.25	0.55	1.6	0.04	0.04	0.15 max
STC 590 A	0.25	0.35	0.30-0.90	0.04	0.04	-
STC 590 B	0.25	0.35	1.5	0.04	0.04	-
Remark: STC 550 Nb in combination with V may be added. In this case the maximum value of Nb+V shall be 0.15%

MECHANICAL PROPERTIES min
Steel grade	Tensile strength Mpa	Yeild point or proof stress Mpa	Elongation %
Steel grade	Tensile strength Mpa	Yeild point or proof stress Mpa	Elongation %
STC 370	370	251	30
STC 440	440	305	10
STC 510 A	510	380	10
STC 510 B	510	380	15
STC 540	540	390	20
STC 590 A	590	490	10
STC 590 B	590	490	15

category	Tolerance on Wall thickness
Hot-finished seamless steel tube	±12.5% however the minimum value is 0.5mm
Cold-finished seamless steel tube	±10% however the minimum value is 0.3mm
Cole finished electric resistance welded steel tube	±8% however the minimum value is 0.15mm

Processes of manufacture and heat treatment
Designation of grade	Process of manufacture	Heat treatment	Application
STC 370	Hot finishing seamless	As manufactured	Cutting
STC 440	Cold finishing electric resistance welding	As cold drawn or stress relieving	Honing
STC 510 A	Cold finishing seamless	As cold drawn or stress relieving	Cutting and honing
	Cold finishing electric resistance welding	As cold drawn or stress relieving	Honing
STC 510 B	Cold finishing seamless	Stress relieving	Cutting and honing
	Cold finishing electric resistance welding	Stress relieving	Honing
STC 540	Hot finishing seamless	As manufactured	Cutting
STC 590 A	Cold finishing seamless	As cold drawn or stress relieving	Cutting and honing
STC 590 B	Cold finishing seamless	Stress relieving	Cutting and honing

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