1. Raw materials:

Straight seam submerged arc welded steel pipe: Steel plates are usually used as raw materials. The size and specifications of steel plates can be selected according to production needs. For large-diameter straight seam submerged arc welded steel pipes, multiple steel plates may need to be spliced and welded together.

Spiral submerged arc welded steel pipes: mainly produced using hot-rolled coils. Hot rolled coils are accelerated by a water cooling system during the rolling process, and their alloy content (carbon equivalent) is often lower than that of similar grade steel plates, which makes the weldability of spiral welded pipes better.

2. Production process:

Straight seam submerged arc welded steel pipe: It is a steel plate that is cut, leveled, and then bent into a tube shape through forming processes such as JCOE, and then welded. When welding, a single weld seam is usually used. When the diameter is greater than 914.4mm, the standard allows the steel pipe to have two straight welds. During the production process, it is inevitable to produce a large number of T-shaped welds, where the welding residual stress is relatively high. The weld metal is often in a three-dimensional stress state, increasing the possibility of cracking.

Spiral submerged arc welded steel pipe: It is made by spiral forming and automatic welding of coiled steel plates. The automatic double wire double-sided submerged arc welding process is adopted, and the weld seam gap control device ensures that the weld seam gap meets the welding requirements, and strictly controls the pipe diameter, misalignment, and weld seam gap. The head and tail of the strip steel are welded using single or double wire submerged arc welding, and automatically repaired by submerged arc welding after being rolled into steel pipes.

3. Characteristics of welds:

Straight seam submerged arc welded steel pipe: The weld seam is a straight strip with a relatively short length. For steel pipes of the same length and diameter, the weld seam length is shorter than that of spiral submerged arc welded steel pipes. However, due to the presence of T-shaped welds, the probability of welding defects is relatively high.

Spiral submerged arc welded steel pipe: The weld seam presents a spiral shape, with a longer length. Compared with straight seam pipes of the same length, the weld seam length increases by 30% -100%. However, the composite stress at the spiral weld seam is 60% -85% of the main stress of the straight seam welded pipe. Under the same working pressure, the wall thickness of the spiral welded pipe with the same diameter can be reduced compared to the straight seam welded pipe, thereby improving the utilization rate of materials and the bearing capacity of the steel pipe.

4. Production scope:

Straight seam submerged arc welded steel pipe: The production diameter is generally 426-1920mm, the wall thickness can reach 60mm, and the length of the steel pipe (without connecting pipes) is generally 6-12 meters. There are certain advantages in producing thick walled steel pipes.

Spiral submerged arc welded steel pipe: The production diameter can reach 3620mm, the wall thickness generally does not exceed 26mm, and the length of the steel pipe can theoretically be infinitely extended. Due to the limitations of the production workshop and transportation tools, the length of a single pipe can reach 21 meters. Has advantages in producing large-diameter steel pipes.

5. Welding quality:

Straight seam submerged arc welded steel pipe: using expansion process, residual stress is close to zero. But there are many T-shaped welds, which increases the possibility of welding defects. According to the process regulations of submerged arc welding, each weld seam should have a starting point and a extinguishing point. However, when welding the circumferential seam of straight seam welded pipes, this condition is often not met, resulting in many welding defects at the extinguishing point.

Spiral submerged arc welded steel pipe: residual stress is high, approaching the yield limit. Weld seam tracking and ultrasonic online detection tracking are difficult, and the probability of weld defects exceeding the standard is higher than that of straight seam submerged arc welded pipes. However, there are a series of strict process controls during the welding process, such as weld seam gap control, strip steel head and tail welding and repair, which make the overall welding quality meet the requirements of many projects.

6. Geometric dimension accuracy:

Straight seam submerged arc welded steel pipe: With high geometric dimension accuracy, the diameter, wall thickness, straightness and other indicators of the steel pipe can be well controlled, making it easier to carry out on-site construction operations such as alignment and welding, and improving construction efficiency and quality.

Spiral submerged arc welded steel pipe: The geometric dimension accuracy is poor. Due to the characteristics of the spiral forming process, it is relatively difficult to control the pipe diameter, roundness and other indicators, which brings certain difficulties to on-site construction. Special measures need to be taken during the construction process to ensure installation quality.

7. Application areas:

Straight seam submerged arc welded steel pipe: It has higher precision and quality, and is usually used in fields such as high-pressure gas and oil transportation, building structures, and bridge pipe piles that require high quality and precision of steel pipes. In some situations where strict requirements are placed on corrosion resistance and compressive strength, straight seam submerged arc welded steel pipes can better meet engineering needs.

Spiral submerged arc welded steel pipe: The production materials and processes are relatively simple, the price is low, and it is mainly used in low-pressure liquid transportation, structural engineering and other fields. For applications such as water supply engineering, agricultural irrigation, and general building structural support that do not require high steel pipe pressure but are sensitive to cost.

8. Price cost:

Straight seam submerged arc welded steel pipe: The production process is relatively complex, and the raw material cost is also high, so the price is relatively high. But its performance advantages are obvious in some specific fields, and its overall cost still has a certain competitiveness in these areas.

Spiral submerged arc welded steel pipes: high production efficiency, relatively low raw material costs, and relatively affordable prices. In some fields where the performance requirements for steel pipes are not particularly stringent, it has a high cost-effectiveness.