Structural Seamless Pipe
High-Quality Structural Seamless Pipe
Precision Mechanical Cold-Rolled Seamless Pipes
Structural Seamless Pipe for Construction

Structural Seamless Pipe

Structural seamless pipes are designed to provide exceptional strength and durability, making them ideal for critical construction and engineering applications where reliability is paramount.

I. Structural Seamless Pipe Use Material Type and Selection Basis

Structural seamless pipe use is widely used in the manufacture of carbon steel, low alloy high-strength steel and special alloy steel, the specific selection of materials need to be matched with the application scenario:

(1) Carbon steel (e.g., 20#, Q345B): low-cost, good weldability, suitable for conventional structures such as building brackets, mechanical frames, and so on.

(2) Low-alloy high-strength steel (such as ST52.3, ASTM A106 Gr.B): through the addition of manganese, silicon and other elements to enhance the strength of the tensile strength of up to 470MPa or more, suitable for bridges, heavy equipment and other high-load scenarios.

(3) Stainless steel (e.g. 304, 316): high corrosion resistance, used in marine platforms or chemical environments.

II. Structural seamless pipe standards and grades
Pipe Standards
Category Standard Common Grades Common Foreign Standards
Structural Seamless Pipe GB/T 8162-2008 10, 20, 35, 45, 40Mn2, 45Mn2, 27SiMn, 20Cr, 40Cr, 20CrMO, 35CrMO, 38CrMoAI, 50CrV, 30CrMnSi ASTM A500-98, ASTM A501-98, ASTM A519-96, JISG3441-1988, JISG3444-1994
Seamless Pipe for Fluid Conveyance GB/T 8163-2008 10, 20, 09MnV, 16Mn ASTMA53-98, JISG3452-1988, JISG3454-1988, DINI629-1984
Petroleum Casing API SPEC5CT J55, K55, N80, P110, C75, L80, C90, C95, T95, L80S, N80T, V150 -
Petroleum Tubing and Couplings API SPEC5CT J55, N80, C90, T95, P110, M65, 80SS -
Pipeline Steel Pipe API SPEC5L A25, A, B, X42, X46, X52, X56, X60, X65, X70 -
High-Pressure Boiler Seamless Pipe GB 5310-2008 20G, 20MnG, 25MnG, 15MoG, 20MoG, 12CrlMoVG, 15CrMoG, 12Cr2MoG, 12Cr2MoWVTiB, 12Cr3MOVSiTiB ASTMAI06-97a, ASTMA213-95a, JISG3461-1988, JISG3462-1988, DINI7175-1979, BS3059:Part2: 1990
Low and Medium Pressure Boiler Seamless Pipe GB 3087-2008 10, 20 -
High-Pressure Seamless Pipe for Fertilizer Equipment GB 6479-2013 10, 20G, 16Mn, 15MnV, 10MoWVNb, 12CrMO, 15CrMO, 1Cr5Mo, 12Cr2MO 1S09329-2-1997, ASTMA161-94
Petroleum Refining Seamless Pipe GB 9948-2013 10, 20, 12CrMO, 15CrMO, 1Cr2Mo, 1Cr5Mo JISG3441-1988
Automotive Axle Tube Seamless Pipe YB/T5053-1997 45Mn2, 45, 25Mn9, 40MnB DINI629-1984
Hydraulic Support Seamless Pipe GB/T17396-2009 27SiMn DINI629-1984
Shipbuilding Carbon Steel Seamless Pipe GB/T5312-2009 C10, C20 -
Cold Drawn Precision Seamless Pipe GB/T3639-2009, GB/T8162-2008 10, 20, 35, 45, 20CrMO DIN2391-1994
Geological Drilling Seamless Pipe GB-T4975-2012 DZ40, DZ50 -
Shell Seamless Pipe for Shells YBn-86 40Mn2, D60 -
Seamless Pipe for Rods Q/OHAD003-94 1Cr5MO -
Bearing Steel Pipe YB/Z12-77YJZ84 GCr5M0 -
Seamless Pipe for Ribbed Bar Couplings Q/0HAD011-1997a 10, 20 -
Seamless Pipe for Gas Cylinders GB/T18248-2008 34Mn2V, 30CrMO, 35CrMo, 45 -
III. Core Performance Advantages

Structural Tubes achieve the following properties through the complete structure without welded seams:

(1) High Strength and Uniformity: Hot rolled seamless tubes eliminate internal stresses through high-temperature rolling, while cold-drawn seamless tubes enhance dimensional accuracy, both of which avoid the problem of weld weak zones in welded steel tubes.

(2) Pressure and impact resistance: seamless steel pipe with uniform wall thickness can withstand high pressure and dynamic loads, which is superior to welded steel pipe that is prone to cracking.

(3) Processing adaptability: can be directly bending, flaring and other molding processes, without worrying about weld cracking.

IV. Comparative Analysis with Welded Steel Pipe

(1) Structural Integrity: Seamless steel pipe has no weld seam and avoids the risk of weld defects; welded steel pipe relies on the quality of the weld seam and requires additional flaw detection.

(2) Cost and efficiency: welded steel pipe production costs are low, high efficiency, suitable for large-diameter or non-load-bearing structure; structural seamless pipe cost is higher, but the life is longer, suitable for critical load-bearing components.

(3) Size range: hot rolled seamless pipe can produce large diameters above Φ600mm, while welded steel pipe has higher size flexibility.

V. Difference between hot rolling and cold drawing process

(1) Hot rolled seamless pipe: formed by rolling at high temperature, there is an oxidized layer on the surface but the production efficiency is high, suitable for thick-walled, large-diameter pipes (such as building columns).

(2) Cold-drawn seamless tubes: stretched and molded at room temperature, with high dimensional accuracy (tolerance ±0.1mm) and clean surface, suitable for precision mechanical parts (such as hydraulic cylinder).

VI.Application Scene Suitability

(1) Construction: Hot rolled seamless tubes are used for trusses and support columns to utilize their high loading capacity.

(2) Mechanical engineering: Cold-drawn seamless tubes are processed into shaft parts to ensure dimensional stability.

(3) Energy and transportation: Low-alloy, high-strength steel seamless tubes are used in oil and gas pipelines and ship structures to balance the need for strength and corrosion resistance.

Common value of outer diameter

Φ20mm~Φ600mm (customized according to demand) .
Common value of wall thickness

1mm~50mm (depending on the application scenario) .
Material

20# steel, Q345B, ASTM A106 Gr.B, ST52.3 .
Standard

National standard (GB/T 8162), American standard (ASTM) or European standard (EN) .
Tensile strength and yield strength

Q345B tensile ≥ 470MPa, yield ≥ 345MPa.
Common value of elongation

≥20% (e.g. 20# steel).
Process Type

Hot Rolling (Hot Expanding), Cold Drawing (Cold Rolling).
Surface Quality Requirements

Oxide Layer, Cracks, Scratches, Pockmarks.
Length and Cut-to-length Accuracy

6m~12m (Customizable).
Chemical Composition

Mild Steel (C≤0.25%), Low Sulfur and Phosphorus (S/P≤0.035%) .
Application Scenarios

Building Trusses, Mechanical Supports, Bridges, Marine Platforms.

Specifications

I. Structural seamless pipe specification size
Standard material: 20G 16Mn
Execution standard: GB5310-95, GB6479-86, GB9948-88

25×2.5-5

57×3-8

114×5-20

168×8-30

325×8-45

28×3-5

60×4-10

121×5-20

180×7-30

351×10-36

32×3-5

63.5×4-12

127×6-20

194×8-30

377×10-38

38×3-6

76×4-14

133×5-22

203×10-32

402×10-45

42×3-6

83×5-14

140×6-22

219×7-45

426×10-30

45×3-6

89×4.5-20

146×8-25

245×8-45

480×12-30

48×3-6

102×4-20

152×8-25

273×8-50

530×12-30

Medium and low pressure boiler tube, fluid pipe, geological pipe standard material: 20 # dz40
Executive standard: GB3087-1999, GB8163-1999, YB23-70

8×1-2

38×3-7

95×6-20

159×5-40

351×10-50

10×1-2

42×3-8

102×4-20

168×8-40

377×10-50

12×1-2.5

45×3-8

108×4-20

180×7-40

402×10-50

14×1.5-4

51×3-10

114×4-20

194×8-40

426×10-50

16×2-4

57×3-10

121×5-20

203×10-45

480×12-45

18×2-5

60×3-12

127×6-25

219×7-50

530×12-40

22×2-5

63.5×3-14

133×5-25

245×8-50

450×12-40

25×2-6

76×4-14

140×6-25

273×8-50

610×12-30

28×2-6

83×5-16

146×8-20

299×10-50

430×12-30

32×2.5-6

89×4-20

152×8-30

325×8-50

720×12-30

II. Size specification of seamless steel pipe for structural use

Name Value
Outer Diameter and Wall Thickness Comply with the provisions of GB/T 17395 (Seamless Steel Tubes)
Length 1. Hot-rolled (extruded, expanded) steel tubes: 3 - 12 m<br>2. Cold-drawn (rolled) steel tubes: 2 - 10.5 m
Straightness 1. For wall thickness ≤15 mm, not more than 1.5 mm/m<br>2. For wall thickness >15 mm to 30 mm, not more than 2.0 mm/m<br>3. For wall thickness >30 mm or outer diameter ≥351 mm, not more than 3.0 mm/m

III. Permissible deviation of outer diameter and wall thickness

Pipe type

Pipe size

Permissible deviation

 

 

 

General

Advanced

Hot Rolled (Extruded, Pressed) Tubes

OD

<50

± 0.50 mm

± 0.40mm

 

 

≥50

± 1 %

± 0.75 %

 

wall thickness

<4

± 12.5 %

(Minimum value ±0.40mm)

± 10 %

(Minimum value ±0.30mm)

 

 

≥4~20

+15%

-12.5%

± 10 %

 

 

>20

± 12.5%

± 10%

Cold Drawn (Rolled) Tubes

Outer diameter

6~10

± 0.20 mm

± 0.10 mm

 

 

>10~30

± 0.40 mm

± 0.20 mm

 

 

>30~50

± 0.45 mm

± 0.25 mm

 

 

>50

± 1 %

± 0.5 %

 

Wall thickness

≤1

± 0.15 mm

± 0.12 mm

 

 

>1~3

+ 15 %, - 10 %

± 10 %

 

 

>3

+ 12.5, - 10 %

± 10 %

Remarks: The permitted deviation after comparison is ± 18 % for hot-expanded tubes with an outside diameter of not less than 351 mm.

 

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