Precision tubes for mechanical machining – HPZ type

Standards and steel grades.
Tube sizes

Precision tubes for mechanical machining are produced by the cold drawn process. The rolled seamless tubes are used as the semi-finished product. HPZ type precision tubes are used as the semi-finished product to produce the hydraulic cylinders. They are destined to have the inside surface machined by honing or stripping and subsequent rolling. Precision tubes for mechanical machining are manufactured from carbon and alloyed steel. Overview of dimensional standards and technical and delivery conditions for mechanical tubes are presented in a separate overview.

Dimensions of hydraulic cylinder tubes

Inside diameter 40 - 115 mm and wall thickness 5,0 - 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 the manufactured dimensions is presented in the dimensional table.

Steel grades for hydraulic cylinder tubes

HPZ tubes are manufactured from the following types of steel. According to STN and ČSN 42 0260: 11 523, according to EN 10305-1: E355 and EN 10 294-1: 20MnV6 and according to DIN 2391-2: St52 and DIN 17100: St52-3. Steel overview together with its chemical composition and its mechanical properties is presented in a separate overview . Steel is produced in the electric arc furnace and it is fully killed. Other steel grades may be delivered upon agreement.

Condition of delivery and thermal treatment of hydraulic cylinder tubes

The 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 hydraulic cylinder tubes

- manufactured length of precision tubes in the range of 3 to 6 meters
- maximum precise length 6 meters

Tolerances of hydraulic cylinder tubes

Tolerances of the outside diameter (OD) HPZ tubes meet the appropriate dimensional table standards. Tolerances values of the inside diameter (ID) are presented in the table. Tolerance of the wall thickness is -/+ 7.5% of the wall thickness. HPZ tubes eccentricity is included in the wall thickness tolerance.

Straightness of hydraulic cylinder tubes

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

Condition of the precision tube surface for mechanical machining

According to the EN 10305-1 directives the precision tubes have the outside surface smooth.

Ends of the hydraulic cylinder 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 hydraulic cylinder 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 hydraulic cylinder tubes

The surface of the tubes is oiled.

Packaging of the precision tubes for mechanical machining

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 precision tubes for mechanical machining

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 hydraulic cylinder tubes

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

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