Seamless Precision Steel Pipe & Tube

Seamless precision steel pipe is a seamless steel pipe produced by hot rolling or cold drawing process, with high dimensional accuracy and excellent surface quality. Seamless precision steel pipe is 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.

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

Difference between seamless precision steel tube vs. ordinary seamless tube:

Seamless precision steel tube is a seamless steel tube produced by hot rolling or cold drawing process, with high dimensional accuracy (tolerance ±0.05mm) and excellent surface quality (Ra≤0.8μm). Compared with ordinary seamless pipes, its key features include:

1. Stricter dimensional tolerance control
2. Higher surface finish
3. More uniform mechanical properties
4. More precise geometric shape

Production process of seamless precision tube:

(1) Hot-rolled precision tube process
Steel billet heating → perforation → precision rolling → sizing → straightening → inspection

(2) Cold-drawn precision tube process
Hot-rolled tube billet → pickling → phosphating → cold drawing → heat treatment → finishing

Precision seamless pipes are usually produced by cold rolling. The cold drawing process can achieve higher precision (IT8-IT10 grade)

Chemical composition of precision seamless steel pipe:

Grade	C max	Si max	Mn max	P max	S max
St35	0.17	0.35	0.4	0.05	0.05
St45	0.21	0.35	0.4	0.05	0.05
St52	0.22	0.55	1.6	0.05	0.05

Delivery condition of of precision seamless steel tube:

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.

Industry standard comparison:

USA: ASTM A519 Seamless pipe for machinery
Germany: DIN 2391 Cold-drawn precision pipe
China: GB/T 3639 Precision seamless steel pipe
Japan: JIS G3441 Precision carbon steel pipe

Application areas of seamless precision tube:

(1) Hydraulic system
Engineering machinery hydraulic cylinder (working pressure 35-50MPa)
Aviation hydraulic pipeline (in compliance with AMS 6360 standard)

(2) Automobile manufacturing
Fuel injection pipe (fuel pressure 150-300bar)
Steering system components (fatigue life ≥ 1 million times)

(3) Precision instruments
Semiconductor equipment guide rails (straightness ≤ 0.1mm/m)
Optical instrument brackets (thermal expansion coefficient controllable)

(4) Energy equipment
Boiler temperature measuring sleeve (temperature resistance 600℃)
Nuclear power plant instrument pipe (nuclear grade certification)

Selection points:

(1) Accuracy grade selection
Ordinary grade: IT12 (general structural parts)
Precision grade: IT9 (hydraulic system)
Super precision grade: IT7 (semiconductor equipment)

(2) Surface treatment options
Phosphating (rust prevention + lubrication)
Chrome plating (wear resistance + corrosion resistance)
Electrolytic polishing (ultra-high cleanliness)

(3) Special requirements
Cleanliness (particles ≤ 100/m²)
Magnetic properties (μ≤1.05)
Grain size (ASTM 6-8 grade)

Read more: Cold Drawn Seamless Tube for Mechanical & Hydraulic or Application of Mechanical Precision Tubes