Causes Of Magnetic Field And Damage Analysis Of Ssaw Steel Pipe

Causes of magnetic field and damage analysis of SSAW steel pipe

The reason why the spiral steel pipe has a magnetic field: during the welding process, DC welding is used. On the welding line, due to the large current at the position of the welding head, there is a strong magnetic field. Under the action of the magnetic field, the magnetic moment of the pipe body may be consistent with the direction of the external magnetic field. When the welding is completed, the magnetic field gradually decreases until it disappears. Due to the hysteresis phenomenon, this is what we usually call the residual magnetic field under the pipe body and the residual magnetic field density.

1. Reasons for the magnetic field of SSAW steel pipes
1. Electromagnetic effect during welding
In the production process of SSAW steel pipes, submerged arc welding technology is used. This welding method requires the arc to generate high temperature in the welding area to melt and fuse the welding material and the base material. During the arc welding process, a strong electromagnetic field is generated, which may remain inside the steel pipe after welding, forming a permanent magnetic field.
2. Magnetic properties of materials
Steel itself is a magnetic material, especially alloys containing iron, which are easily magnetized under the action of external electromagnetic fields. SSAW steel pipes are usually made of carbon steel. The iron element in carbon steel will give it certain magnetic characteristics. It may be magnetized when exposed to magnetic fields of different intensities during production, transportation and use.
3. Influence of mechanical stress
During the manufacturing and installation of SSAW steel pipes, they may be subjected to various mechanical stresses, such as bending, stretching, compression, etc. These mechanical stresses will cause changes in the internal lattice structure of the steel pipe, causing the originally disordered magnetic domains to rearrange, thereby forming a macroscopic magnetic field.
4. Environmental factors
Magnetic fields in the external environment may also have an impact on SSAW steel pipes. For example, near power transmission lines or around strong magnetic field equipment, the external magnetic field will magnetize the steel pipe, causing a magnetic field to form inside it. In addition, the earth's magnetic field itself may also affect the magnetization state of the steel pipe to a certain extent.
2. Damage to the magnetic field of SSAW steel pipe
1. Impact on detection and measurement
The magnetic field inside the SSAW steel pipe will interfere with non-destructive testing equipment, especially detection methods that rely on magnetic principles such as magnetic particle detection and magnetic flux leakage detection. The internal magnetic field may lead to inaccurate test results, increase the risk of missed detection and false detection, and affect the maintenance and safety management of the pipeline.
2. Increased corrosion risk
The presence of a magnetic field may promote the electrochemical corrosion process on the surface of the steel pipe. The magnetic field will affect the potential distribution on the surface of the steel pipe, forming a local battery effect and accelerating the corrosion rate in the local area. This is particularly unfavorable for pipelines that transport corrosive media, which may shorten the life of the pipeline and increase maintenance and replacement costs.
3. Changes in mechanical properties
The magnetic field may have an adverse effect on the mechanical properties of SSAW steel pipes. The presence of a magnetic field will change the stress distribution inside the steel pipe, which may lead to stress concentration and reduce the bearing capacity and fatigue resistance of the steel pipe. This effect is particularly significant in high-pressure transmission environments, which may increase the risk of pipeline bursting and leakage.
4. Impact on the stability of the pipeline system
In pipeline systems that transport flammable and explosive gases or liquids, the internal magnetic field may cause electromagnetic interference, affect the normal operation of sensors, valves and other equipment, and increase system instability and the probability of accidents.
III. Solutions and suggestions
1. Welding process optimization
During the production process of SSAW steel pipes, the welding process can be optimized to reduce the intensity of the electromagnetic field generated during the welding process. For example, using more stable power supplies and welding parameters, reducing arc current and voltage, and reducing the generation of magnetic fields.
2. Demagnetization treatment
After the steel pipe is produced, it can be demagnetized. Common demagnetization methods include heat treatment, AC demagnetization and mechanical vibration demagnetization, which can effectively reduce the residual magnetic field inside the steel pipe.
3. Select low-magnetic materials
If conditions permit, low-magnetic materials can be used to make SSAW steel pipes to reduce the risk of magnetization. For example, selecting steel containing non-magnetic alloy elements can significantly reduce the magnetism of the steel pipe.
4. Strengthen detection and monitoring
Perform regular inspection and monitoring of SSAW steel pipes, especially in the initial use and when used in high-risk environments. Use a combination of multiple detection methods to ensure the accuracy of the test results, and promptly discover and deal with magnetic field problems.
5. External environment management
In the use environment of SSAW steel pipes, try to avoid approaching strong magnetic field equipment and areas to reduce the impact of external magnetic fields on steel pipes. At the same time, shielding measures can be taken to reduce the magnetization effect of external magnetic fields on pipelines.
The occurrence of magnetic fields in SSAW steel pipes is an issue that cannot be ignored. The reasons are complex and diverse, involving production, materials, mechanical stress and environment. The presence of magnetic fields will have an adverse effect on the detection, corrosion, mechanical properties and system stability of steel pipes. Therefore, in practical applications, comprehensive measures need to be taken to optimize the production process, conduct demagnetization treatment, select suitable materials and strengthen monitoring to reduce the negative impact of magnetic fields on SSAW steel pipes and ensure the safe and stable operation of the pipeline system.