JIANGSU HAOHUA INDUSTRY GROUP

 Precision cold drawn seamless steel tube

Cold Drawn Seamless tubing (also known as CDS). Cold Drawn Seamless tubes offer tight tolerances compared to Hot Finished Seamless tube, and offers stronger physical properties compared to other mechanical tubing.
CDS is popular in the hydraulics, being used to make hollowed chrome plated telescopic cylinders and hydraulic rods. It is also popular for large bore, heavy walled, high pressure hydraulic cylinders. Cold Drawn Seamless tubes also find uses in heavy equipment manufacturing such as cranes and garbage trucks.
General process of cold drawing
A considerable proportion of the seamless tubes and pipes manufactured through the cold roll piercing technology undergo subsequent cold forming. The principal reasons behind cold drawing are:
Achievement of closer wall thickness and diameter tolerance
Improvement in surface finish
To enhance serviceability
No premature failure
Suitable for critical forming Such as 180˚ Bends
Enhancement of mechanical properties of the tube
Expansion of product mix towards the lower end of the OD and wall thickness scales.
THERE ARE THREE BASIC PROCESSES EMPLOYED FOR THE COLD DRAWING OF TUBE:Hollow drawing
Stationery drawing or floating plug drawing and
Drawing over a mandrel (also known as drawing on-the-bar)
Annealing
After the goods are cold drawn to sizes, the tubes are put on annealing furnace for heat treatment and normalising.
Straightening
Post annealing, the goods are passed through a seven roller straightening machine to achieve proper straightening of the tubes.
Eddy current
Post straightening, each tube is passed through eddy current machine to detect for surface cracks and other defects . Only the tubes that pass eddy current are fit for delivery to customers.
Finishing
Each tube is either oiled with corrosion resistant oil or varnished for surface protection and corrosion resistant as per customers requirement, each tube end is covered by plastic end caps to avoid damage in transit, the marking and specs are put and the goods are ready for dispatch.

Seamless Precision Steel Tubes according to EN 10305-1

Standard: DIN2391 part 2 , DIN EN10305-1, DIN17175 etc;
Material: ST35,ST45,ST52.
Manufacturing method: cold-rolled / cold-drawn
Delivery condition: BK,BKS,SR,GBK,NBK.

Certificate
Factory Certification: 2.2 according to EN
Acceptance Test Certificate:3.1 according to EN 10204

Packing:
in bundles tied with steel strips. External packing by wooden cases if the wall thickness/OD ratio is low.
Oil-coating is generally necessary especially for export.

Application:
Used in hydraulic & pneumatic cylinder ,automobile and other mechanical device .Feature: high precision and high brightness, the inner and outer surface of the tubes have high cleanness without oxid, mechanical properties of the final tubes also come out excellent, promising no leakage under high pressure, no deformation after cold-bent and no cracks when flaring and flattening, ensuring the efficient operation in all service.
NBK means protective heat-treating under the non-oxidation enviroment to get a bright and smooth surface for the tubes.

DIN 2391-81 Part 2 Seamless Precision steel tubes(DIN2391-81)
Standard DIN 2391 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.
Chemical composition(%)

Mechanical and technological properties

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.

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.

Condition on delivery: