Seamless hydraulic steel tubes to DIN 2391‑C & DIN 2445‑2, 4 mm to 190 mm

It conveys fluid between hydraulic components — fittings, valves, flanges, cylinders and power units. The tube is cold drawn seamless, which gives close dimensional tolerances, higher strength and better machinability than a hot finished tube, so it suits high‑performance piping rather than general structural work.

E355 is the higher tensile grade — minimum yield 355 MPa, tensile 490–630 N/mm². It takes more pressure at the same wall, so you can often hold the duty with a thinner wall and less weight. E235 has lower carbon, so it is more ductile and easier to weld and bend — minimum yield 235 MPa, tensile 340–480 N/mm². Choose on whether pressure or fabrication is the constraint. Tell us the working pressure and we will pick.

It depends on OD, wall and grade — all 158 sizes are tabulated on this page with working pressure, burst pressure and IMPA code. As examples, 10 mm OD × 2.0 mm is 565 bar in E235 and 799 bar in E355; 42 mm OD × 4.0 mm is 269 bar in E235. Pressures are calculated per DIN 2413 at normal temperature.

Multiply the tabulated working pressure by the rating factor: 0.90 at −40 °C, 1.0 at 120 °C, 0.89 at 150 and 175 °C, 0.83 at 200 °C. Above 200 °C these tubes are not rated — ask us for a different material. Note that cold derates it too, which is easy to miss.

Yes — an EN 10204 3.1 mill test certificate as standard, carrying the chemical analysis and mechanical results per heat plus flattening, flaring and 100% eddy current test results. An EN 10204 3.2 countersigned by a nominated third‑party inspector can be arranged if the contract requires it; ask before the order. There is a real 3.1 reproduced on this page.

Phosphated and normalised, oiled inside and outside. Phosphating gives corrosion resistance; normalising relieves the stress left by cold drawing and leaves the steel tougher, more formable and more ductile, which is what makes the tube bendable on site. Galvanising, hot dip or electro, is available on request.

3× the outer diameter for cold bending, on a tube bender or by hand. So a 42 mm tube wants a 126 mm radius minimum. The calculator works it out alongside the weight.

kg/m = 0.02466 × wall × (OD − wall), both in mm, at a steel density of 7.85 g/cm³. A 42 mm OD tube with a 4.0 mm wall is 3.748 kg/m. Use the calculator for your own sizes.

Seamless. Our hydraulic steel tube is drawn from a billet, so there is no weld join or seam anywhere in the wall. That is what allows the pressure ratings in the tables to apply around the full circumference.

It is the minimum yield strength in MPa — which makes the designation genuinely useful rather than arbitrary. E355 has a minimum yield of 355 MPa; E235 has 235 MPa. Once you know that, the old ST names line up: ST52.4 = E355 and ST37.4 = E235. Worth remembering the small‑size exception though: below a 3.0 mm wall and 30 mm OD the minimum yield is 10 MPa lower than the headline figure.

They are the two dimensional standards hydraulic tube is made to, and we supply both. DIN 2391/C is now published as DIN EN 10305‑1, and DIN 2445/2 as DIN EN 10305‑4. Both cover cold drawn seamless precision steel tube, and both are available in E355 and E235. Which one applies is normally set by the specification you are working to rather than by the duty — so if the drawing names one, quote it and we will supply to it.

Yes, on request — it is not a stock finish. Two options: hot dip galvanising, where the tube is immersed in molten zinc to form a metallurgical bond and a thick, durable coating for outdoor, marine and heavy industrial exposure; and electro (cold) galvanising, which deposits a thinner, more uniform layer suited to indoor plant and tighter fits where coating build‑up would foul an assembly. Tell us the environment and we will say whether it is worth the cost and lead time — on many indoor installations the standard NBK finish is genuinely enough.

Tighter ones than ordinary welded or hot‑finished tube — that is the point of cold drawn precision tube, and it is what lets a compression fitting bite and seal on the outside surface without weeping. The exact figures depend on the size and the tolerance class, and the mill certificate for your batch states what was achieved. Send the OD and wall and we will confirm the tolerance for that size before you order.

Stock is held in Malaysia or Singapore. A product specialist prices your enquiry within two working hours, and stocked sizes are dispatched same or next working day — across Malaysia and Singapore, including Johor Bahru and the Klang Valley. For cutting lists or non‑stocked sizes, tell us the date you need them and we will confirm it before you commit.