ASTM A671 Steel Welded Pipe

Update time：2025-03-11

I. Material chemical composition control

(1) The performance of ASTM A671 steel welded pipe results from strict chemical composition control.

The carbon content (0.30% max) is carefully adjusted to ensure strength while reducing the risk of cold cracking.

Manganese (1.30% max) is added to significantly improve hardenability and impact toughness, while silicon (0.10-0.35%) acts as an effective deoxidiser to optimise metallurgical quality.

Unlike spiral steel pipe, ASTM A671 steel welded pipe is produced using a straight-seam pipe manufacturing process with more stringent sulphur and phosphorus content controls (S ≤ 0.025%, P ≤ 0.035%). This differentiated element control makes the resistance to brittle fracture of LSAW steel pipe at low temperatures significantly better than that of traditional spiral steel pipe.

(2) Chemical composition (%)

II. Mechanical performance advantages

(1) ASTM A671 Gr.65 steel welded pipe mechanical properties reflect three core advantages:

  Yield strength ≥ 290MPa

  Tensile strength ≥ 483MPa

  Elongation ≥ 20%

Compared with API 5L spiral steel pipe, LSAW steel pipe has a more uniform distribution of mechanical properties. The longitudinal strength of LSAW steel pipe produced by JCOE forming process is increased by 10-15% on average compared with spiral welded pipe, which is especially suitable for medium and low temperature pressure piping system.

(2) Mechanical properties

III. Welding Process Comparison

ASTM A671 steel welded pipe offers a choice of two advanced welding processes:

(1) Electrofusion Welding (EFW) process

  Welding speed: 3-5m/min

  Depth of fusion control accuracy: ± 0.2mm

  Suitable for straight seam steel pipe with wall thickness ≤ 25mm

(2) submerged arc welding (LSAW) process

  Welding speed: 1-2m/min

  Melting depth range: 8-30mm

  Suitable for wall thickness > 25mm thick-walled pipe

In contrast, spiral steel pipe is welded by continuous spiral welding, although the production efficiency is higher, but there are inherent defects of residual stress concentration.ASTM A671 steel welded pipe straight seam design effectively avoids the problem of stress superposition in the spiral weld.

(3) Welding process parameters

IV. Temperature Adaptability

ASTM A671 steel welded pipe achieves temperature adaptability breakthrough through special heat treatment process:

(1) Medium temperature performance (-29 ℃ ~ 200 ℃)

   High-temperature yield strength retention rate of> 85%

   Oxidation weight gain rate <2mg/cm² (200 ℃/100h)

(2) low temperature performance (-46 ℃ ~ -29 ℃)

   Charpy V-notch impact work ≥ 27J

   Fracture shear area ≥ 50%

This temperature adaptability makes LSA steel pipe perform better than ordinary spiral steel pipe in the application of low temperature pipeline of LNG receiving station. Actual engineering data show that under -40℃ working condition, the leakage rate of LSA steel pipe is 0.3‰ lower than that of spiral steel pipe.

(3) Dimensional tolerances

V.Engineering Application Fields

With its unique advantages, ASTM A671 steel welded pipe is gradually replacing traditional spiral steel pipe in the following fields:

(1) Energy transmission system

　　Oil and gas gathering and transmission pipeline network (design pressure ≤ 12MPa)

　　Low temperature LNG storage and transport pipeline (-162 ℃ ~ -50 ℃)

　　Refining plant process pipeline (medium temperature ≤ 200 ℃)

(2) Building structural engineering

　　Ultra-high-rise building pressure shaft (pressure ≥ 2.5MPa)

　　District heating pipe network (hot water temperature ≤ 150 ℃)

　　Industrial plant support structure (seismic grade ≥ 8)

(3) Special environmental applications

　　Coastal engineering corrosion-resistant pipeline (salt spray test＞1000h)

　　Buried pipeline in permafrost area (-50℃ environmental service)

　　Seismic zone flexible connection system (displacement absorption ≥50mm)

(4) Typical application parameters

VI.Quality control standards

(1) ASTM A671 steel welded pipe implements strict three-level quality assurance system:

　　Raw material inspection: 100% spectral analysis

　　Process monitoring: online weld tracking inspection

　　Finished product inspection: 100% ultrasonic flaw detection +30% X-ray re-examination

Compared with spiral steel pipe, LSAW pipe has obvious advantages in dimensional accuracy control: diameter tolerance ±0.5% (spiral pipe ±1.2%), ellipticity ≤0.8% (spiral pipe ≤1.5%). This makes ASTM A671 steel welded tubes the first choice in precision piping projects.

(2) Testing standards

VII. Economic Analysis

(1) Although the initial cost of ASTM A671 steel welded pipe is 15-20% higher than that of spiral steel pipe, the full life cycle cost advantage is significant:

　　30% improvement in installation efficiency (thanks to precise dimensional fit)

　　40% lower maintenance costs (fewer leak repairs)

50 per cent longer service life (better corrosion resistance)

(2) Economic Comparison