1. Field of application

1.1 This standard applies to seamless circular tubes and pipes(hereinafter briefly referred to as "tubes") made of unalloyed steels as listed in table 1. These tubes are predominantly used in the constructin of chemical plant, vessels, pipework and for general mechanical engineering purposes. They are designed to meet high performance requirements. Normally there are no limiting vaiues or the maximum permissible working pressure of these tubes. The permissi l working temperature shall not exceed 300℃ are specified in Appendix A.)

The limits of application and other specifications given in this standard shall apply except in cases here other specifications are contained in codes of practice for specific fields of application, e.g. the Technische Regeln fur Dampfkessel (TRD) (Technical rules on steam boilers) or the Technische Regeln fur Druckbehalter (TRB)
(Technical rules on pressure vessels), AD-Merkblatter (AD Instrucation sheets).

Chemical composition of steels for seamless circular tuves subject to special repuirements

steel grade		Type of deoxidization (R, killed (including semi-killed)) (RR, fully killed)	chemical composition, % by mass
Symbol	Material number		C	P	S	N¹)	Addition  of nitrogen fixing elements (e.g.not less than  0,020% AItotal
St37.0	1.0254	R	0.17	0.040	0.040	0.009²)	-
St44.0	1.0255	R	0.21	0.040	0.040	0.009²)	-
St52.0³)	1.0421	RR	0.22	0.040	0.035	-	Yes

¹) A content in excess of the maximum value started is permitted if a phosphorus content less than the maximum specifled by 0,005% P per 0,001% N is observed. However, the nitrogen content shall not exceed a value of 0.012% in the cast analysis and 0,014% in the product analysis.
²) The specified maximum values do not apply if the steels are supplied with the RR (instead of R) type of deoxidization
³) The content shall not exceed 0.55% Si and 1,06% Mn in the cast analysis or 0,60% Si and 1,70% Mn in the product analysis

table 3. Amounts by which the chemical composition in the product analysis may deviate from the limiting values applicable to the cast analysis {see table2}

Element	Amount by which the product analysis may deviate from the limiting values applicable to the analysis % by mass
C	+0,02
P	+0,010
S	+0,010
N	+0,001¹)

¹) A contant in excess of the maximum value stated is permitted if a phosphorus content less than the maximum specified by 0,005% P per 0,001% N is observed. However, the nitrogen contant shall not exceed a value of 0,012% in the cast analysis and 0,014% in the product analysis (this does not apply to the RR type of deoxidization.

table 4. Mechanical properties of tubes in the as delivered condition at room ternperature For wall thickness exceeding 65 mm, the values shall be agreed at the time of ordering

Steel grade		Upper yield stress ReH for wall thicknesses, in mm,			Tensile strangth Rm N/mm²	Elongation after fracture A5
Symbol	Material  number	up to 16	over 16 up to 40	over 40 up to 65		lonigtudinal	transverse
St 37.0	1.0254	235	225	216	350²) to 480	25	23
St 44.0	1.0256	275¹)	265¹)	255¹)	420²) to 550	21	19
St 52.0	1.0421	355	345	335	500²) to 650	21	19

steel-chemical composition (DIN1629):

Brand	Chemical Composition(%)
	C max	Si max	Mn	P max	S max
St 35	0.17	0.35	≥0.40	0.025	0.025
St 45	0.21	0.35	≥0.40	0.025	0.025
St 52	0.22	0.55	≤1.60	0.025	0.025

Steel grade		Chemical Composition(%)
Steel name	Steel number	C max	Si max	Mn	P max	S max	Al min
E215	1.0212	0.10	0.05	0.70	0.025	0.025	0.025
E235	1.0308	0.17	0.35	1.20	0.025	0.025	-
E355	1.0580	0.22	0.55	1.60	0.025	0.025	-

Mechanical Properties(Mpa):

Steel grade	BK		BKW		BKS			GBK		NBK
	Yield strength Rm N/mm min	Elongation% min	Yield strength Rm N/mm min	Elongation % min	Yield strength Rm N/mm min	Tensile Strength ReH N/mm min	Elongation % min	Yield strength Rm N/mm min	Elongation % min	Yield strength Rm N/mm min	Tensile Strength ReH N/mm min	Tensile Strength ReH N/mm min
St35	480	6	420	10	420	315	14	315	25	340-470	235	25
St45	580	5	520	8	520	375	12	390	21	440-570	255	21
St52	640	4	580	7	580	420	10	490	22	490-630	355	22

Steel grade		Minimum values for the delivery condition
Steel name	Steel number	+ C		+ LC		+ SR			+ A			+ N
		Rm Mpa	A%	Rm Mpa	A%	Rm Mpa	ReH Mpa	A%	ReH Mpa		A%	Rm Mpa	ReH Mpa	A%
E215	1.0212	430	8	380	12	380	280	16	280		30	290-430	215	30
E235	1.0308	480	6	420	10	420	350	16	315		25	340-480	235	25
E355	1.0580	640	4	580	7	580	450	10	450		22	490-630	355	22