We Super Steel Manufacturing Co.,Ltd(SMC) are amongst the top manufacturers and suppliers for the seamless steel pipe, welded steel pipe, OCTG products and fittings from China. We have been manufacturing and supplying these products to the industry since 1993, and received repeat orders and appreciation from our valued customers.
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Always up to date. In this column you can find the steel pipe related articles, including industry trends, product standards and materials, and some technical guidelines.
In the 1950s and 1960s, spiral steel pipes were a prominent choice for oil and gas pipelines. However, the 1970s and 1980s brought significant competition from LSAW (Longitudinal Submerged Arc Welded) and ERW (Electric Resistance Welded) steel pipes. Today, SSAW pipes are rarely used in oil and gas pipelines globally. Many major international oil companies and pipeline firms have ceased to allow their use, driven by the industry's increasing demands for reliability. SSAW steel pipes face inherent manufacturing limitations that hinder their ability to meet these requirements.
Quality Comparison: SSAW vs. LSAW Steel Pipes
SSAW pipes exhibit several deficiencies compared to LSAW pipes:
- Residual Stress:
SSAW pipes have relatively high residual stress, occasionally nearing the yield limit, while LSAW pipes, benefiting from the expansion process, have residual stress close to zero.
- Weld Tracking:
Tracking spiral welds and performing ultrasonic online detection are challenging, resulting in a higher probability of weld defects exceeding standards.
- Weld Seam Staggering:
SSAW pipes often experience seam misalignment of 1.1–1.2 mm, which exceeds the internationally recommended limit of 10% of the wall thickness.
- Stress Concentration:
Spiral welds show poorer streamlining, leading to significant stress concentrations compared to LSAW pipes.
- Heat-Affected Zone:
The heat-affected zone in SSAW pipes is larger and represents a weak link in the weld quality.
- Dimensional Accuracy:
SSAW pipes typically lack the geometric precision of LSAW pipes, posing challenges for on-site construction such as fitting and welding.
- Thickness Limitations:
SSAW pipes cannot achieve the same wall thickness as LSAW pipes for a given diameter.
Process Differences: Straight Seam vs. Spiral Seam Steel Pipes
Both straight seam and spiral seam pipes are types of welded steel pipes widely used in industrial production and construction. Key distinctions arise from their respective manufacturing processes:
- Straight Seam Pipes:
Produced via high-frequency welding or submerged arc welding, these pipes offer simpler production processes, higher efficiency, lower cost, and faster production. However, larger diameter straight seam pipes often require T-welding, where shorter segments are joined to achieve the desired length. T-welded joints increase the likelihood of defects, residual stress, and crack formation due to their three-dimensional stress state.
- Spiral Seam Pipes:
Manufactured using submerged arc welding, these pipes can produce varying diameters from the same width of raw material and larger diameters from narrower blanks. Despite these advantages, their weld length is 30–100% longer than that of straight seam pipes for the same length, reducing production efficiency. Consequently, smaller diameters favor straight seam welding, while larger diameters often utilize spiral welding.
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