Formation and prevention of engineering stress corrosion cracks in steel structures

Formation of engineering stress corrosion cracks in steel structures.

With the progress of science and technology and the deepening of people's understanding of steel structure engineering, steel structure engineering as a new form of building structure has been more and more applied. Due to the different levels and processing processes of production or installation manufacturers, the quality of steel structure engineering also varies greatly. The paper introduces the formation of stress corrosion crack in steel structure engineering.

Cause of stress corrosion crack formation.

(1) activation channel stress corrosion.

When the corroded battery is large Yin and small Yang, the dissolution of Yang shows concentrated corrosion damage. As long as the Yang remains in front of the crack during the corrosion process, the crack tip is not passivated, and some parts (on both sides of the crack port) are passivated, so that the crack develops forward to fracture.

Strain produces active channel stress corrosion.

The passivation film cracks under the action of stress, and the exposed metal at the crack becomes activated Yang and dissolves. In the corrosion process, the passivation film breaks, the passivation film breaks and repairs, and the passivation film repaired under continuous strain conditions is damaged and continues to corrode.

(3) hydrogen embrittlement stress corrosion.

Corrosion cells are composed of small Yin and large Yang. The dissolution of the sun appears as uniform corrosion. If hydrogen analysis occurs in the small negative region, the metal in the negative region will concentrate hydrogen infiltration, resulting in brittle fracture under continuous load, and stress corrosion will develop smoothly. With the appearance of crack, the stress and strain concentration of crack causes hydrogen in metal to approach the crack, resulting in stress corrosion fracture.

Second, stress corrosion crack prevention measures.

The formation of stress corrosion must have the comprehensive effect of material, medium and tensile stress. Therefore, corresponding measures should be taken from three aspects: product structure design, installation and construction to production management.

(1) Material: duplex stainless steel material; Select welding materials that are basically consistent with the chemical composition and organization of the base material (equal composition principle);

(2) Medium: Be sure to consider the possibility of medium corrosion base material. In order to reduce stress corrosion in a specific environment, the caustic agent can be added to the medium. Surface treatment technology can also be used to prepare sacrificial positive coatings or physical isolation coatings on the surface of the member.

(3) Stresses include:

① Select a reasonable joint form in the welding process to reduce residual stress; ② Correct welding sequence; (3) Appropriate heat input; ④ Stress removal can be performed after welding.