1. The Engineering Significance of Welded Pipes

In the global market for industrial fluids, the various types of welded pipes serve as the circulatory system of modern civilization. Unlike tubi senza saldatura, which are extruded from solid billets, welded pipes are formed from flat steel plates or coils. This manufacturing process allows for greater control over wall thickness consistency and enables the production of extremely large diameters that would be impossible to achieve through seamless extrusion.

The reliability of a welded pipe depends entirely on the quality of its seam. In 2026, advances in automated laser tracking and ultrasonic testing have made welded joints nearly as strong as the parent metal. Whether transporting natural gas across continents or managing high-purity chemicals in a pharmaceutical lab, selecting the correct types of welded pipes is the first step in ensuring operational safety and longevity.

3. Type 1: Electric Resistance Welded (ERW) Pipes

Electric Resistance Welding (ERW) is one of the most common types of welded pipes used in low to medium-pressure applications. The process involves cold-forming a steel ribbon into a cylindrical shape. Current is then passed between the two edges of the steel to heat the metal to a point where the edges are forced together to form a bond without the use of welding filler material.

ERW pipes are highly favored for their dimensional accuracy and cost-efficiency. In 2026, ERW technology has evolved to utilize high-frequency induction, which significantly reduces the heat-affected zone (HAZ), resulting in a more uniform grain structure at the weld. These pipes are frequently found in water transport, scaffolding, and line pipe for the oil and gas industry.

4. Type 2: Longitudinal Submerged Arc Welded (LSAW) Pipes

For high-pressure, heavy-wall applications, LSAW is the preferred choice among the different types of welded pipes. This method uses a single wide steel plate as the raw material. The plate is pressed (UOE or JCOE process) into a pipe shape and then welded both internally and externally using submerged arc welding. The use of flux protects the weld pool from atmospheric contamination, resulting in extremely clean and strong joints.

LSAW pipes are the backbone of long-distance oil and gas pipelines, particularly those crossing difficult terrain or offshore environments where high tensile strength is mandatory. Their ability to reach diameters of up to 60 inches makes them irreplaceable for major infrastructure projects.

5. Type 3: Spiral Submerged Arc Welded (SSAW) Pipes

SSAW pipes, also known as HSAW (Helical Submerged Arc Welded), are unique in their production. Rather than a longitudinal seam, the weld follows a spiral path around the circumference of the pipe. This allows a narrow coil of steel to be transformed into a very large diameter pipe. One of the structural advantages of SSAW pipes is that the spiral seam provides extra resistance against internal pressure, as the stresses are distributed across the helical path.

While historically seen as less robust than LSAW, modern SSAW pipes produced in 2026 under strict quality controls are widely used for low-pressure fluid transport, piling for construction, and large-scale water distribution systems.

6. Type 4: High-Frequency Welded (HFW) Pipes

HFW is a specialized subset of ERW that utilizes high-frequency current (typically 70 kHz or higher). This type of welded pipe is synonymous with high-quality automotive and mechanical tubing. The high-speed welding process ensures that the seam is nearly invisible and extremely ductile. HFW pipes are often subjected to post-weld heat treatment (PWHT) to normalize the seam, making it ideal for applications requiring bending or flaring.

7. Type 5: TIG/Plasma Welded Precision Pipes

When dealing with stainless steel and high-nickel alloys, Tungsten Inert Gas (TIG) or Plasma welding is the gold standard for creating the most precise types of welded pipes. This process is slower than ERW or LSAW but offers unmatched control over the weld bead and penetration. This is the method used by leaders like TOKO TECH to produce specialized products such as Stainless steel welded Coiled tubes.

Precision TIG welding is essential for the pharmaceutical and food processing industries, where the internal surface of the pipe must be perfectly smooth to prevent bacterial growth. Furthermore, the ability to produce these in coiled formats allows for long, continuous runs in heat exchangers and hydraulic systems, reducing the number of potential leak points at mechanical fittings.

8. Comparison Table: Welded Pipe Characteristics

9. Frequently Asked Questions (FAQs)

Are welded pipes as strong as seamless pipes?

In modern engineering, the “weld factor” is often 1.0, meaning the weld is considered as strong as the parent metal. While seamless pipes are traditionally used for the highest pressures, the types of welded pipes produced today with automated ultrasonic inspection are sufficient for nearly all industrial applications.

What are the benefits of stainless steel welded Coiled tubes?

Coiled tubes, like those produced by TOKO TECH, offer significant advantages in installation. Because they can be produced in lengths of several kilometers, they minimize the need for welds and joints in the field, which are common failure points in subsea or high-pressure energy systems.

What is JCOE in LSAW manufacturing?

JCOE refers to the “J-ing, C-ing, O-ing, and Expanding” process. The steel plate is bent into a ‘J’ shape, then a ‘C’ shape, and finally an ‘O’ shape before the seam is welded and the pipe is mechanically expanded to its final diameter.

Can welded pipes be used in corrosive environments?

Yes, provided the correct alloy and welding technique are used. Stainless steel welded pipes with high chromium and nickel content are specifically designed for corrosion resistance in chemical plants and shipbuilding.

10. References and Quality Standards

• API Spec 5L: Specification for Line Pipe (American Petroleum Institute).
• ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes.