DIN 2391-81 Part 2 Seamless Precision steel tubes

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DIN 2391-81 Part 2 Seamless Precision steel tubes

Field of application
This Standard defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.
Tubes according to this Standard are mainly used where accuracy to dimension and, possibly, small wall thicknesses and good surface condition are required.

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

JIS Number and Corrensponding Foreign Standards (DIN2391)

Chemical composition(%)

Grade	Mfg. Process	Chemical composition(%)
		C	Si	Mn	P	S	Ni	Cr	Mo	Others	①
											②
											③
											④
St30Si	S	0.10Max	0.30Max	0.55Max	0.040Max	0.040Max	-	-	-	-	①
											②
											③
											④
St30A1	S	0.10Max	0.05Max	0.55Max	0.040Max	0.040Max	-	-	-	Al deoxydized	①
											②
											③
											④
St35	S	0.17Max	0.35Max	0.40Max	0.050Max	0.050Max	-	-	-	-	①
											②
											③
											④
St45	S	0.21Max	0.35Max	0.40Max	0.050Max	0.050Max	-	-	-	-	①
											②
											③
											④
St52	S	0.22Max	0.55Max	1.60Max	0.050Max	0.050Max	-	-	-	-	①
											②
											③
											④

Note: ①Cold-finished/hard ②Cold-finished/soft ③Annealed ④Normalized
Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Mechanical Properties(Mpa)

Grade	Material number	Tensile Test MPa or N/mm²		Remaks (Similar to JIS)	Possibility Temperature
Grade	Material number	Min Yield point	Tensile Strength	Remaks (Similar to JIS)	Possibility Temperature
St30Si	1.0211	-	400Min	(STKM11)
		-	355Min
		-	285Min
		215	295~420
St30Al	1.0212	-	400Min	(STKM11)
		-	355Min
		-	285Min
		215	295~420
St35	1.0308	-	440Min	(STC38)
		-	370Min
		-	315Min
		235	340~470
St45	1.0408	-	540Min	(STKM13)
		-	470Min
		-	390Min
		255	440~570
St52	1.0580	-	590Min	(STKM19)
		-	540Min
		-	490Min
		350	490~630

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Welded Steel Tubing and pipe-Corresponding to DIN 2391-1

Wall thickness s	Nominal dimension	0.5	0.8	1	1.2	1.5	1.8	2	2.2	2.5	2.8	3	4.5	5	5.5	6	7	8	9	10	12	14	16	18	20	22	25
Wall thickness s	Permissible deviation
Outside diameter da
Nominal dimension	Permissible deviation
4	±0.1
5
6
7
8
9
10
12	±0.08
14
15
16
18
20
22
25
26
28
30
32	±0.15
35
38
40
42	±0.20
45
48
50
55	±0.25
60	±0.25
65	±0.30
70	±0.30
75	±0.35
80	±0.35
85	±0.40
90	±0.40
95	±0.45
100	±0.45
110	±0.50
120	±0.50
130	±0.70
140	±0.70
150	±0.80
160	±0.80
170	±0.90
180	±0.90
190	±1.0
200	±1.0
220	±1.20
240	±1.20
260	±1.30
1) For outside diameters of nominal dimensions 4 and 5 mm, the permissible deviation from the nominal dimension s of the wall thickness is ± 20 % For outside diameters of nominal dimensions 6 to 8 mm, the permissible deviation from the nominal dimension s of the wall thickness is ±15%.													s/D =1/60			s/D =1/40					s/D =1/20

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Quality grade

The tubes are supplied in the following quality grades :

A	precision steel tubes intended primarily for mechanical stressing, without any particular quality requirement and without acceptance test certificate
B	precision steel tubes intended primarily for mechanical stressing, with special quirement and exclusively with acceptance test certificate
C	precision steel tubes with special requirement according to section 12. Theses requirements and corresponding tests must be agreed, with the customer having to specify his requirements at the time of enquiry and on ordering

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Table 1. Steel grades

Quality grade	Steel grade
	Code number	Material number
A and B	St 30 Si St 30 Al St 35 St 45 St 52	1.0211 1.0212 1.0308 1.0408 1.0580
C	All steel grades according to quality grade A and B, as well as other steels, e.g. according to
	DIN 1651 DIN 17 100 DIN 17 200	DIN 17 210 DIN 17 211 DIN 17 212

Condition on delivery

The tubes are supplied in one of the conditions listed in table 3. Other conditions on delivery are specified in table 9 (quality grade C).
Table 3. Conditions on delivery

Term	Symbol	Explanation
Cold-finished/hard (cold-finished as-drawn)	BK	No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
Cold-finished/soft (lightly cold-worked)	BKW	After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed	GBK	After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized	NBK	The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Material Comparison Tables (ASTM →KS, JIS, DIN, BS, NBN, NF, UNI)

Mechanical and technological properties

8.1. The mechanical properties depend on the condition on delivery as defined in table 3.

8.2. In technological testing (drift expandig test and flattening test) the samples must comply with the requirements of sections 11.2.3.2. and 11.2.3.3.

8.3. In the case of other steel grades and/or other conditions on delivery then those specified in tables 2, 3 and 8, the mechanical and technological properties must be mutually agreed. In these cases, the tubes are supplied according to quality grade C.

8.4. The steels listed in table 2 are deemed to be suitable for welding because of their chemical composition and metal lurgical treatment.

In the BK or BKW conditions on delivery, the mechanical properties are modified in the zone which has been subjectes to heating. This should be taken into account (see DIN 8528 Part 1) in assessing the weldability of a component.

Steel grade		Condition on delivery
Steel grade		Cold-finished/hard (BK) 3)		Cold-finished/soft (BKW) 3)		Annealed (GBK) 3)		Normalized (NBK)
Code number	Material number	Tensile strength Rm N/mm^2 min	Elonga- tion at repture A5(%) min	Tensile strength Rm N/mm^2 min	Elonga- tion at repture A5(%) min	Tensile strength Rm N/mm^2 min	Elonga- tion at repture A5(%) min	Tensile strength Rm N/mm^2	Upper yield point ReH N/mm^2 min	Elongation at repture A5(%) min
St 30 Si	1.0211	400	8	330	12	280	30	290 to 420	215	30
St 30 Al	1.0212	400	8	330	12	280	30	290 to 420	215	30
St 35	1.0308	440	6	370	10	315	25	340 to 470	235	25
St 45	1.0408	540	5	470	8	390	21	440 to 570	255	21
St 52	1.0580	590	4	540	7	490	22	490 to 630	355	22
3) The yield point for the annealed (GBK)condition on delivery is at least 50% of the (ultimate) tensile strength. Depending upon the degree of deformation in the drawing operation, the yield point of tubes delivered in the cold-finished/hard (BK)and cold-finished/soft(BKW) conditions, may be increased to a level close to the tensile strength. In calculating the yield point, the following values are recommended : cold-finished/hard condition on delivery ≥ 80% of the tensile strength, cold-finished/soft condition on delivery ≥ 70% of the tensile strength. 4) In the case of tubes of outside diameter ≤ 30 mm, the wall thickness of which is ≤ 3mm, the minimum value of the yield point is 10 N /mm^2 lower.

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