What are the advantages and disadvantages of SSAW pipe piles compared with the straight seam welded pipes?

SSAW pipe pile is made of low carbon structural steel or low alloy structural steel steel strip rolled into a pipe billet at a certain angle of spiral line (called forming angle), and then the SSAW pipe pile seam is welded together, it can produce large diameter steel pipe.

Here is the content list:

What are the advantages of SSAW pipe piles compared withthe straight seam welded pipes?

What are the disadvantages of SSAW pipe piles compared with the straight seam welded pipes?

What are the outstanding properties of SSAW pipe piles?

What are the advantages of SSAW pipe piles compared with the straight seam welded pipes?

Advantages of SSAW pipe pile.

Easy and stable to connect with other steel materials

Easily spliced into longer lengths

Ideal for hard driving conditions

High strength and good roundness

Easy transport handling (loading/unloading and storage)

SSAW pipe pile production process is simple, high production efficiency, low cost, and faster development. The strength of SSAW pipe pile is generally higher than that of pipe, and can produce larger diameter welded pipe with narrower billets, and can also produce welded pipe of different diameters with the same width of billets.

According to the above characteristics, it is known that SSAW pipe pile burst, because the positive stress and synthetic stress suffered by the weld seam is relatively small, the burst generally does not originate in the spiral weld seam, its safety than the straight seam welded pipe.

What are the disadvantages of SSAW pipe piles compared with the straight seam welded pipes?

When the SSAW pipe pile is subjected to internal pressure, two main stresses are usually generated in the tube wall, namely radial stress δY and axial stress δX. The synthetic stress at the weld seam δ = δY(l/4sin2α+cos2α)1/2, where α is the helix angle of the SSAW pipe pile weld seam.

The helix angle of SSAW pipe pile seam is generally 50-75 degrees, so the synthetic stress at the spiral weld seam is 60-85% of the main stress of straight welded pipe. In the same working pressure, the same diameter of the SSAW pipe piles than the wall thickness of the straight seam welded pipe can be reduced.

But,compared with the same length of straight seam pipe, the weld length increases by 30 to 100%, and the production speed is lower. Therefore, most of the smaller diameter SSAW pipe piles are straight seam welded, and most of the large diameter SSAW pipe piles are spiral welded.

What are the outstanding properties of SSAW pipe piles?

Metallurgical properties of the materials that distinguish SSAW pipe piles from LSAW welded pipe is produced from steel plates, while SSAW pipe pile is produced from hot rolled coils. The hot rolled strip unit rolling process has a number of advantages and has the metallurgical process capability to obtain the production of high quality pipe line steel.

For example, the output stand is equipped with a water cooling system to accelerate cooling, which allows the use of low-alloy compositions to achieve special strength grades and low-temperature toughness, thereby improving the weldability of the steel.However, this system is largely absent in steel sheet production plants. The alloy content (carbon equivalent) of coils is often lower than that of similar grades of steel plates, which also improves the weldability of SSAW pipe piles.

More important to note is that, because the SSAW pipe pile coil rolling direction is not perpendicular to the direction of the steel pipe axis (its clamping solution depends on the spiral angle of the steel pipe), while the straight seam steel pipe steel plate rolling direction perpendicular to the direction of the steel pipe axis, and thus, the SSAW pipe pile material is better than the straight seam steel pipe crack resistance.

From the welding process SSAW pipe piles and straight seam steel pipe welding method is the same, but the straight seam welded pipe will inevitably have a lot of ding weld, so the chances of welding defects are greatly increased, and the residual stress of welding at the ding weld is larger, the weld metal is often in a three-way stress state, increasing the possibility of cracking.

Moreover, according to the submerged arc welding process, each weld should be at the arc initiation and arc extinguishing, but each straight seam welded pipe in the welded ring seam, can not achieve the condition, thus there may be more welding defects at the arc extinguishing.