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Seamless Precision Steel Tube

DIN2391 seamless precision steel tube, DIN2391 cold drawn seamless precision steel tube, DIN2391 round seamless precision steel tube

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Description

DIN2391 seamless precision steel tube

Materials of DIN2391 seamless precision steel tube:

The tubes shall be manufactured from electric steel or basic oxygen steel, the melting and casting processes being at the discretion of the manufacturer.

The steel shall be cast as killed steel.

Table 1: Steel grades

Quality grade	Steel grade		Previous designation used in Germany
	As in DIN EN10027 Part 1	As in DIN EN10027 Part 2
A	S215GSiT S215GAlT S235G2T S255GT S355GT	1.0211 1.0212 1.0308 1.0408 1.0580	St 30 Si St 30 Al St 35 St 45 St 52
C	All grades as for quality grade A, and any other steel grades.

Table 2: Chemical composition of steel grades shown on ladle analysis

Steel grade		Chemical composition, as a percentage by mass
Symbol	Material number	C Max.	Si Max.	Mn	P Max.	S Max.
St 30 Si	1.0211	0.10	0.30	≤0.55	0.025	0.025
St 30 Al	1.0212	0.10	0.35	≤0.55	0.025	0.025
St 35	1.0308	0.17	0.35	≥0.40	0.025	0.025
St 45	1.0408	0.21	0.35	≥0.40	0.025	0.025
St 52	1.0580	0.22	0.55	≤1.60	0.025	0.025

The following alloying elements may be added: Nb≤0.03%, Ti≤0.03%, V≤0.05%, Nb+Ti+V≤0.05%

Table 3: Permitted deviations of the product analysis from the specified ladle analysis

Element	Permitted deviation from the specified limits of the ladle analysis, as a percentage by mass
C	+0.02
Si	+0.03
Mn	+0.06 or -0.06
P	+0.005
S	+0.005
Nb	+0.01
Ti	+0.01
V	+0.02

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Table 4: Final supply conditions

Designation	Symbol	Description
Cold finished (hard)	BK	Tubes do not undergo heat treatment following the final cold forming and, thus, have a rather high resistance to deformation
Cold finished (soft)	BKW	The final heat treatment is followed by cold drawing involving limited deformation. Appropriate further processing allows a certain degree of cold forming (e.g. bending, expanding).
Cold finished and stress-relieved	BKS	Heat treatment is applied following the last cold forming process. Subject to appropriate processing conditions, the increase in the residual stresses involved enables both forming and machining to a certain degree.
Annealed	GBK	The last cold forming process is followed by annealing in a controlled atmosphere.
Normalized	NBK	The last cold forming process is followed by annealing above the upper transformation point in a controlled atmosphere.

Table 5: Mechanical properties of tubes at ambient temperature

Final supply condition	Steel grade	Cold finished (hard) (BK)		Cold finished (soft) (BKW)		Cold finished and stress-relieved (BKS)			Annealed (GBK)		Normalized (NBK)
Material designation	Material number	Min. Tensile strength,Rm, in, N/mm2	Min. Elongation at fracture, A5, as a percentage	Min. Tensile strength, Rm, in, N/mm2	Min. Elongation at fracture, A5, as a percentage	Min. Tensile strength, Rm, in, N/mm2	Min. yield strength, ReH, in N/mm2	Min. Elongation at fracture, A5, as a percentage	Min. Tensile strength, Rm, in N/mm2	Min. Elongation at fracture, A5, as a percentage	Tensile strength, Rm, in N/mm2	Min. Yield strength, ReH, in, N/mm2	Min. Elongation at fracture, A5, as a percentage
St 30 Si	1.0211	430	8	380	12	380	280	16	280	30	290-420	215	30
St 30 Al	1.0212	430	8	380	12	380	280	16	280	30	290-420	215	30
St 35	1.0308	480	6	420	10	420	315	14	315	25	340-470	235	25
St 45	1.0408	580	5	520	8	520	375	12	390	21	440-570	255	21
St 52	1.0580	640	4	580	7	580	420	10	490	22	490-630	355	22

Remark:

1) The yield strength for the annealed (GBK) condition shall be equal to at least 50% of the tensile strength. Depending on the extent of deformation, the yield strength of tubes supplied in the cold finished (hard) (BK) and cold finished (soft) (BKW) conditions, may come close to reaching the tensile strength. Calculations should be based on a minimum value of 80% of the tensile strength for the cold finished (hard) condition and of 70% for the cold finished (soft) condition.

2) For tubes with an outside diameter of up to 30mm and a wall thickness up to 3mm, the minimum yield strength may be 10N/mm2 lower.

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