EN10305 Seamless Precision Steel Tube Standard and Steel grade: EN10305-1 E215 EN10305-1 E235 EN10305-1 E355 EN 10305 european standard specifies the technical delivery conditions for seamless cold drawn steel pipe of circular cross section used in hyhydraulic and pneumatic power systems. The allowed pressure rates and temperatures are the responsibility of the customer in accordance with the state of the art and in application of the safety coefficients specified in the application regulations, codes or standards. Tubes according to this EN 10305 European standard are characterised by having precisely defined tolerances on dimensions and a specified surface roughness. EN 10305 seamless precision steel tube shall be manufactured from hot finished seamless tubes by cold drawning. Other suitable methods of cold working are permitted. The tubes shall be delivered in the delivery condition +N which means that after the final cold drawing operation the tubes are normalized in a controlled atmosphere. NBK means protective heat-treating under the non-oxidation enviroment to get a bright and smooth surface for the tubes.   Chemical composition(%) of EN 10305-1

Steel grade Name	Steel Number	C(% max)	Si(% max)	Mn(% max)	P(% max)	S(% max)
E215	1.0212	0.10	0.05	0.70	0.025	0.015
E235	1.0308	0.17	0.35	1.20	0.025	0.015
E355	1.0580	0.22	0.55	1.60	0.025	0.015

  Mechanical and technological properties of EN 10305-1

Yield strength (min Mpa)	Tensile strength (min Mpa)	Elongation (min %)
215	290-430	30
235	340-480	25
355	490-630	22

Note:

• 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.

  Condition on delivery of EN 10305-1:

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.