Spiral steel pipe production process and use characteristics

Spiral steel pipe production process and use characteristics

Spiral steel pipe is a spiral seam steel pipe which is made of steel coiled coil as raw material, which is often heated and extruded and welded by automatic double wire double-sided submerged arc welding process.

(1) Raw materials are strip coils, welding wire, flux. Strict physical and chemical testing is required before input.

(2) The steel head and tail are butt jointed, and the single wire or double wire submerged arc welding is used, and the automatic submerged arc welding is used after the steel pipe is rolled.

(3) Before forming, the strip is leveled, trimmed, planed, surface cleaned and pre-bent.

(4) The electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of the strip.

(5) Adopt external control or internal control roll molding.

(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are strictly controlled.

(7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding by American Lincoln welding machine to obtain stable welding specifications.

(8) The welded seams are all inspected by online continuous ultrasonic automatic injury inspection to ensure the non-destructive testing coverage of 100% spiral welds. If there is a defect, the alarm is automatically alarmed and sprayed, and the production worker adjusts the process parameters at any time to eliminate defects in time.

(9) The steel pipe is cut into individual pieces by an air plasma cutting machine.

(10) After cutting into a single steel pipe, each batch of steel pipe shall be subjected to a strict first inspection system to check the mechanical properties, chemical composition, bonding condition, surface quality of the steel pipe and non-destructive testing to ensure the pipe making process. After that, it can be officially put into production.

(11) The part of the weld with continuous acoustic flaw detection mark, after manual ultrasonic and X-ray review, if it is defective, after repair, it will pass the non-destructive test again until it is confirmed that the defect has been eliminated.

(12) The tube of the butt weld of the strip and the joint of the butt joint intersecting the spiral weld are all inspected by X-ray television or film.

(13) Each steel pipe is subjected to hydrostatic pressure test and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. The test parameters are automatically printed and recorded.

(14) Pipe end machining, so that the verticality of the end face, the groove angle and the blunt edge are accurately controlled.

Overview of the characteristics of the production and use of spiral steel pipe:

The rust removal of the hand-opening tool can reach the Sa2 level, and the rust removal of the power tool can reach the Sa3 level. If the steel surface is attached with a strong iron oxide scale, the effect of the tool rust removal is not illusory, and the anchor pattern deep pickling required for the anti-corrosion construction is not achieved. The main stress of the straight seam pipe is exactly perpendicular to the direction in which the pipe impact resistance is the lowest, while the spiral steel pipe staggers the direction in which the pipe impact resistance is the lowest, so that the advantage of the length of the spiral steel pipe weld is changed to the upper hand. The anti-corrosion method of spiral steel pipe also suppresses one of the processes.

In the application process, the principal stress direction of the spiral steel pipe, that is, the axial direction of the steel pipe, is equivalent to the length of the straight seam pipe. Secondly, since the pipeline steel is a rolled steel plate, the impact toughness is relatively isotropic, and the rolling is smooth. The CVN value of the direction can be three times higher than the CVN value perpendicular to the rolling direction.

Using a wire brush and other tools to stop the grinding of the steel surface, it can remove loose or raised scale, rust, welding slag and so on.

The rust removal of the hand-opening tool can reach the Sa2 level, and the rust removal of the power tool can reach the Sa3 level. If the steel surface is attached with a strong iron oxide scale, the effect of the tool rust removal is not illusory, and the anchor pattern deep pickling required for the anti-corrosion construction is not achieved.

The main stress of the straight seam pipe is exactly perpendicular to the direction in which the pipe impact resistance is the lowest, while the spiral steel pipe staggers the direction in which the pipe impact resistance is the lowest, so that the advantage of the length of the spiral steel pipe weld is changed to the upper hand.

The anti-corrosion method of spiral steel pipe also starts from suppressing one of the processes.

If anti-corrosion coating is applied to the outer wall of the pipeline, the loop resistance can be increased, and the corrosion current can be added. The DC power supply is applied to make the steel pipe form a negative potential to the soil and constitute a cathodic protection, which can eliminate the anode-anode potential difference and basically stop the anode-anode process. Suspended.

Anti-corrosion coating rule of law, cathodic protection rule of law.

However, once the anti-corrosion coating is broken, the local iron will decelerate local corrosion.

Therefore, the separation of the anti-corrosion coating and the cathodic protection phase is the method of treating both the symptoms and the root causes, and is economically ineffective.

Countries such as the United States have understood the rules, and the use of anti-corrosion coatings requires the use of cathodic protection.

However, regarding the fragmentation of rural gas, due to the dense open network, the external power supply for cathodic protection is very disturbing to other pipelines, which will constitute a benefit to itself and the benefit of his family.

However, the anode protection law that is connected with the spiral steel pipe with the metal material negative than the steel tube potential does not exhibit such a situation. Therefore, the gas pipeline of the country gas should adopt an anti-corrosion method in which the anti-corrosion coating is separated from the anode.

For other non-trunk pipelines with lower pressure, the anti-corrosion coating method is generally used indirectly.

At present, the external anti-corrosion coating commonly used in buried gas pipelines has three types of PE composite structure, epoxy resin powder, coal tar enamel, epoxy coal tar pitch and PE tape.

The three-layer PE composite structure and epoxy powder anti-corrosion coating have excellent functions, so it is also a secondary anti-corrosion coating for buried pipelines in Europe and America.

Considering the one-sided economic factors such as durability and protection, the three-layer PE composite structure anticorrosive coating is generally preferred.

In the anode protection method, a magnesium alloy is generally used as an anode to terminate the pipeline protection.

Due to the destruction of the input current process, the expected service life of the magnesium alloy anode is best matched with the service life of the pipeline, and neither the cost nor the protection cost is added.

However, it should be noted that when the soil resistivity is too high and the protected pipeline passes through the water, anode protection should not be used.

Different anti-corrosion methods have different anti-corrosion quality and cost. According to the different pressures of the protected spiral steel pipes, different uses and their different environments and different gas supplies, the anti-corrosion methods and anti-corrosion measures are considered one-sidedly.