1, High-quality seamless pipes of uniform composition, high cold shear tonnage, smooth and neat end face of the cutting head, and inferior materials due to the poor material, cut the first end surface there are often off the meat of the phenomenon that is uneven, and no metallic luster. And because of inferior materials manufacturers cutting products less head, head and tail will be a big ears.

When steel yield to a certain extent, due to the internal grain rearrange and its ability to resist deformation increased, although deformation developed rapidly, but it can only be increased as the stress increased, until the stress reaches the maximum value.

Pipeline steel strength has a significant impact on the work hardening ability of materials and Bauschinger effect. With the increase of the steel strength, the hardening index tends to decrease, namely the work hardening ability decreased, the Bauschinger effect strengthened.

To ensure the quality of spiral steel pipe, spiral steel pipe before delivery should be carried out with a number of strict quality testing. Specific detection is as below:

For tool steel, its stability is mainly determined by the thermal fatigue toughness and strength of steel. Therefore, thermal stability, good mold steel fatigue must have good toughness and high strength (wet strength) a good fit. There should be welded flat work surface rust, the appearance of defects scratches, bumps and other effects used.

Corrosion in the form of seamless steel pipe for buried pipelines are divided into two kinds of localized corrosion and uniform corrosion, localized corrosion mostly dominated, the danger is also the largest.

As there is no need to add filler metal during the welding process of HFW steel pipe, it has the advantage of high welding speed and high production efficiency, and it is widely used in oil and gas transport, oil pipelines, structures and various mechanical pipe and other fields.

Mild carbon steel pipe annealing organization ferrite and a small amount of pearlite, lower its strength and hardness, good ductility and toughness.

There are usually two heating products for the pipe billet of the welded steel pipe, including pre-heating and rolling tube. When manufacturing welded steel pipe, the two heating products should be heated before in a given path, and it requires the use of intermediate annealing so that the residual stress can be removed.

The helix angle of the spiral welded pipe is generally 50-75 degrees, the synthesis of spiral weld stress is longitudinally welded pipes of 60-85% of the principal stress. In the same work under pressure, spiral welded pipe of the same diameter than the straight seam welded pipe wall thickness can be reduced.

Pipe withstand the internal pressure, usually in the wall on the two main stress, radial stress δY and axial stress δX. Weld resultant stress δ = δY (l/4sin2α + cos2α) 1/2, which, α is the helix angle of the spiral weld pipe.

LSAW pipe in the performance of metallurgical testing process for weld defects in the edge of the residual oxide scale during the welding process is the drift of the deposited metal cover caused by the fundamental causes that severely corroded steel.