Precision tubes machined to “ready to use” - type HP

Standards and steel grades,
Tube size.

Precision tubes are produced by the cold drawing process. The rolled seamless tubes are used as the semi-finished product. “Ready to use” precision tubes type HP are used directly for production of the hydraulic cylinders. The inside surface is machined by stripping and subsequent rolling at Zeleziarne Podbrezova a.s. Precision tubes HP type are made from carbon and alloyed steel. Overview of dimensional standards and technical-delivery conditions for the HP tubes is presented in a separate overview.

Dimensions of the HP tubes.

Inside diameter range is 40 - 110 mm and the wall thickness range is 4.0 – 10.0 mm. Precision steel tubes are delivered according to EN 10305-1, DIN 2391, STN 42 6711 and 42 6712, ČSN 42 6711 and 42 6712. More detailed overview of manufactured dimensions is presented in the dimensional table.

The Steel grades for the HP tubes

HP tubes are produced from the following steel. According to STN and ČSN 42 0260: 11 523; according to EN 10305-1: E355 and according to EN 10 294-1: 20MnV6; also according to DIN 2391-2: St52 and DIN 17100: St52-3. Overview of the steel together with its chemical composition and its mechanical properties is presented in a separate overview. Steels are produced in electric arc furnace and it is fully killed. Upon agreement it is possible to deliver other types of steel.

Delivery condition and thermal treatment of the HP tubes

Tubes are delivered as cold drawn and annealed to relieve the stress BKS (+SR). Other delivery conditions are possible upon agreement. Overview of other conditions may be found here .

Length of HP tubes

- manufactured length of HP tube is in the range of 3 to 6 meters
- maximum precise length 6 meters

Tolerances of HP tubes

Tolerances of the outside diameter (OD) HP tubes meet the appropriate dimensional table standards DIN 2391-1, EN 10305-1, STN and ČSN 426712. Tolerances values of the inside diameter (d) H8 a H9 are presented in the table. Tolerance of the wall thickness is -/+ 7.5% or 10% of the wall thickness.
HP tubes eccentricity is included in the wall thickness tolerance.

Straightness of HP tubes

1 mm / m (1 : 1 000) measured on the outside surface.

Condition of the HP tubes

According to the DIN 2391 directives, the precision tubes have the outside surface smooth.

Ends of the HP tubes

Ends of the tubes are square to the longitudinal axis of the tubes. Upon agreement the tubes may be capped with plastic caps.

Marking of the HP tubes

The tubes are marked along the length of the tube where the following pieces of information are used: manufacturers’ logo, dimension (OD x ID), steel, heat number and the number of standard or other data as per the customers’ request.

Surface protection of the HP tubes

The surface of the tubes is oiled.

Packaging of the HP tubes

The tubes are delivered in bundles with either circular or hexagonal cross-section weighing maximum 2000 kilograms. The tubes are tied with a steel band.

Testing of HP tubes

Selection of the tests is either according to standards or upon agreement with customer: chemical analysis, tensile test, dimensional test, visual inspection and nondestructive testing (eddy current). Other tests are possible upon agreement.

Certificates for HP tubes

According to the following standards: EN 10 204 - 3.1 or DIN 50049 - 3.1.B

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