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

Structural Seamless Pipe

Product Specifications

Product Name: Seamless Steel Tube for Construction、Carbon Steel Seamless Pipe for Structure、Mechanical Seamless Pipe

OD: 10mm – 1220mm

WT: 2mm – 40mm

Length: 5.8m、6m、11.8m

Material: Q195、Q215、Q235、Q345、20#、16Mn、Q420

Standard: GB/T 8162、GB/T 8163、ASTM A106

Application: Structural seamless pipes are mainly used in mechanical manufacturing, bridges, building structures, vehicle manufacturing, and other structural components that require high strength and dimensional accuracy.

I. Material Types and Selection Criteria for Structural Seamless pipes

Structural seamless pipes are manufactured using a variety of materials, and the specific selection must be reasonably matched based on the application environment and performance requirements.

i. Carbon Steel Materials

Carbon steel seamless pipes, such as 20# and Q345B, are widely used in conventional structures like building supports and mechanical frames due to their low cost and excellent weldability.

They are the most economical and practical choice among structural seamless pipes, particularly suitable for applications involving general loads.

ii. Low-Alloy High-Strength Steel

For high-load applications such as bridges and heavy equipment, low-alloy high-strength steel materials like ST52.3 or ASTM A106 Gr.B are typically used.

These materials enhance strength and durability by adding alloy elements like manganese and silicon, achieving tensile strengths of 470 MPa or higher, meeting stringent performance requirements for structural seamless pipes.

iii. Stainless steel materials

In corrosive environments or special operating conditions, such as offshore platforms or chemical industries, 304 or 316 stainless steel round seamless pipes with excellent corrosion resistance are more suitable. They effectively resist rust and extend the service life of the pipes.

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 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 of Structural Seamless Pipes

Structural seamless Pipes achieve the following performance characteristics through their seamless, integrated structure:

i. High strength and uniformity: hot rolled seamless steel pipes eliminate internal stresses through high-temperature rolling, while cold-drawn seamless pipes enhance dimensional accuracy. Both methods avoid the weld zone weaknesses found in welded steel pipe.

ii. Pressure Resistance and Impact Resistance: Seamless steel pipes with uniform wall thickness can withstand high pressure and dynamic loads, outperforming welded steel pipes prone to cracking.

iii. Processing Adaptability: They can be directly subjected to forming processes such as bending and flaring without concerns about weld seam cracking.

IV. Comparison Between Structural Seamless Pipe and Welded Steel Pipe

i. Structural Integrity
Structural seamless pipe is manufactured without welds, which eliminates the risk of weld-related defects. In contrast, welded steel pipe relies on the quality of its weld seam, and additional inspection is typically required to detect possible flaws.

ii. Cost and Efficiency
Welded steel pipe is produced at lower cost and higher efficiency, making it suitable for large-diameter or non-load-bearing structures. Structural seamless pipe, while more expensive, is preferred in critical load-bearing applications due to its superior durability and longer service life.

iii. Size Range
Hot-rolled seamless pipe can be manufactured in diameters exceeding Φ600mm. However, greater dimensional flexibility is offered by welded pipe, especially for custom or oversized designs.

V. Difference between hot rolling and cold drawing process

i. 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).

ii. Cold-drawn seamless pipes: 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. Applications of Structural Seamless Pipes

i. Building Structures
Widely used in load-bearing frames and support components of high-rise buildings, bridges, factories, and other engineering projects, offering excellent strength and seismic resistance.

ii. Mechanical Manufacturing
Suitable for manufacturing mechanical equipment components such as shafts, connecting rods, and sleeves, requiring high precision and excellent load-bearing capacity.

iii. Vehicle and Shipbuilding
Commonly used in truck chassis, construction machinery structural components, and ship hull frames, capable of withstanding high impact and dynamic loads.

iv. Tower Structures and Steel Structures
Such as communication towers, power towers, and crane equipment structures, requiring steel pipes with high strength and stability.

v. Warehousing and Logistics Equipment
Used in applications such as shelving, conveying equipment, and forklift structural components, where both strength and lightweight design are prioritized.
Structural seamless pipes are typically custom-produced by specialized seamless steel pipe factorys according to standard dimensions and performance requirements, ensuring excellent safety and durability in various structural engineering applications.

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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