Small diameter seamless steel pipe is produced by hot‑rolled or cold‑drawn process without welding seam. Cold‑drawn version features high dimensional accuracy and smooth surface. Carbon steel, alloy steel and stainless steel available. MTR / MTC certificate provided. Custom sizes, end finishing and export packing are offered.

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ASTM A106‑B EN10216 API 5L 16Mn (Q345B) 12Cr1MoVG 40Cr 4130 15CrMo TP304 TP316L

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Product Detail

Product Overview：

Small‑diameter seamless steel pipe generally refers to seamless tubes with outer diameter ≤219mm. Two primary manufacturing processes: hot‑rolled and cold‑drawn.
✅ Hot‑rolled seamless pipe Directly pierced and hot‑formed from steel billet. Cost‑effective for general‑purpose service. Outer diameter range: 32mm‑219mm. Surface comes with black oxide scale. Not suitable for ultra‑thin‑wall requirement.
✅ Cold‑drawn seamless pipe Formed by cold drawing process. Superior dimensional tolerance and smooth surface finish. It can realize thin‑wall specification from 1.5mm wall thickness. Annealing treatment is optional to release internal stress for machining and high‑performance applications. OD range: 6mm‑219mm. We supply carbon steel, low‑alloy, alloy steel and stainless‑steel small‑diameter seamless pipes. Material Test Report (MTR / MTC) is available for each batch. Third‑party inspection such as SGS is acceptable upon request.

Applications：
Oil, gas and industrial fluid transportation
Instrument piping & hydraulic line
Mechanical components and machining blanks
Boiler & heat‑exchanger tubes
Petro‑chemical and general‑engineering projects

Parameter range
Outer diameter	Φ6mm - Φ219mm (small diameter range)
Wall thickness	0.5mm-10mm
Standard length	1-12m, customizable shorter lengths supported
Outer diameter accuracy	Maximum ±0.03mm
Executive Standards	DIN 2391, EN 10305-1, ASTM A519, GB/T 3639
Non-standard customization	Customizable non-standard outer diameter, wall thickness, and inner hole honing

Optional tolerance range
Tolerance control	Optional manufacturing process
Tolerance ≤ 0.05 mm	Cold rolling
Tolerance ≤ 0.10 mm	Cold rolling
Tolerance ≤ 0.30 mm	Cold drawing \| Cold rolling
Tolerance ≤ 0.50 mm	Cold drawing \| Hot rolling
Tolerance ≤ 1.00 mm	Hot rolling \| Hot expanding

Common outer diameter tolerance
Outer Diameter (mm)	20	25	32	38	45	51
Outer diameter tolerance (mm)	±0.15	±0.19	±0.24	±0.29	±0.34	±0.38
Qualified range (mm)	19.85-20.15	24.81-25.19	31.76-32.24	37.71-38.29	44.66-45.34	50.62-51.38

Outer Diameter (mm)	57	620	76	89	108	114
Outer diameter tolerance (mm)	±0.43	±0.45	±0.57	±0.67	±0.81	±0.86
Qualified range (mm)	56.57-57.43	59.55-60.45	75.43-76.57	88.33-89.67	107.19-108.81	113.14-114.86
Allowable deviation of outer diameter: ± 0.75% D or ± 0.30 mm, whichever is greater

Allowable deviation of wall thickness (cold drawn tube)
Wall thickness (mm)	S ≤ 3	3＜S ≤ 10	S＞10
Allowable deviation of wall thickness	+15% S or ± 0.15mm, whichever is greater	+12.5%S / −10%S	±10%S

Length and bending tolerance
Project	Fixed length	Fixed length	Bending degree per meter	Full length curvature
Specification conditions	L ≤ 6m	L＞6m	all	≤1.5 mm/m
Allowable deviation	+30 / 0 mm	+50 / 0 mm	all	≤ Total length × 0.15%
The above table shows the GB/T8162-8163 standard for ordinary fluid/structural cold drawn tubes; Hydraulic precision bright small caliber tube execution: GB/T 3639-2021, with higher accuracy and smaller tolerances.

Optional delivery status
Oil removal from oil pipes	Annealing and straightening	Steel pipe corrosion prevention
Steel pipe threading	Length cut-to-length	Steel pipe coating
Steel pipe cap	Exquisite bundling	Beveling

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Product Detail

Product Overview：

Parameter range
Outer diameter	Φ6mm - Φ219mm (small diameter range)
Wall thickness	0.5mm-10mm
Standard length	1-12m, customizable shorter lengths supported
Outer diameter accuracy	Maximum ±0.03mm
Executive Standards	DIN 2391, EN 10305-1, ASTM A519, GB/T 3639
Non-standard customization	Customizable non-standard outer diameter, wall thickness, and inner hole honing

Optional tolerance range
Tolerance control	Optional manufacturing process
Tolerance ≤ 0.05 mm	Cold rolling
Tolerance ≤ 0.10 mm	Cold rolling
Tolerance ≤ 0.30 mm	Cold drawing \| Cold rolling
Tolerance ≤ 0.50 mm	Cold drawing \| Hot rolling
Tolerance ≤ 1.00 mm	Hot rolling \| Hot expanding

Common outer diameter tolerance
Outer Diameter (mm)	20	25	32	38	45	51
Outer diameter tolerance (mm)	±0.15	±0.19	±0.24	±0.29	±0.34	±0.38
Qualified range (mm)	19.85-20.15	24.81-25.19	31.76-32.24	37.71-38.29	44.66-45.34	50.62-51.38

Outer Diameter (mm)	57	620	76	89	108	114
Outer diameter tolerance (mm)	±0.43	±0.45	±0.57	±0.67	±0.81	±0.86
Qualified range (mm)	56.57-57.43	59.55-60.45	75.43-76.57	88.33-89.67	107.19-108.81	113.14-114.86
Allowable deviation of outer diameter: ± 0.75% D or ± 0.30 mm, whichever is greater

Allowable deviation of wall thickness (cold drawn tube)
Wall thickness (mm)	S ≤ 3	3＜S ≤ 10	S＞10
Allowable deviation of wall thickness	+15% S or ± 0.15mm, whichever is greater	+12.5%S / −10%S	±10%S

Length and bending tolerance
Project	Fixed length	Fixed length	Bending degree per meter	Full length curvature
Specification conditions	L ≤ 6m	L＞6m	all	≤1.5 mm/m
Allowable deviation	+30 / 0 mm	+50 / 0 mm	all	≤ Total length × 0.15%
The above table shows the GB/T8162-8163 standard for ordinary fluid/structural cold drawn tubes; Hydraulic precision bright small caliber tube execution: GB/T 3639-2021, with higher accuracy and smaller tolerances.

Optional delivery status
Oil removal from oil pipes	Annealing and straightening	Steel pipe corrosion prevention
Steel pipe threading	Length cut-to-length	Steel pipe coating
Steel pipe cap	Exquisite bundling	Beveling