Cause analysis of LSAW steel pipe surface crack

Surface microcracks in LSAW steel pipes significantly impact product quality, ranging from minor defects to severe issues that can lead to product rejection. These defects are particularly prominent in pipes containing elements like niobium, vanadium, and titanium, which seriously affect product quality and yield rates. The presence of surface microcracks not only results in substantial economic losses for enterprises but also limits the development of plate production lines. Longitudinal surface microcracks, such as edge cracks, longitudinal cracks, and star cracks, arise from several factors, including improper rolling process parameters, abnormal continuous casting processes, inherited slab cracks, and the enrichment of residual elements.

Causes of Longitudinal Surface Microcracks:

- Continuous Casting Mold Issues:

Copper Coating Detachment: The detachment of the copper coating from the continuous casting mold is a primary cause. This can lead to copper penetrating the solidified shell's austenite grain boundaries, resulting in grain boundary cracks.

- Thermal Stress:

Uneven Thermal Stress: Uneven thermal stress during the casting process can lead to cracks, especially in steels containing titanium, which exhibit high crack sensitivity.

Control Measures:

- Improve Mold Copper Quality:

Enhance Copper Coating: Ensure the copper coating on the continuous casting mold is of high quality and prevent its detachment.

- Strengthen Slab Quality Inspection:

Pre-production Inspection: Conduct thorough inspections of slab quality before production to identify and address potential issues.

- Post-production Inspection:

Longitudinal Crack Detection: Implement rigorous inspection procedures after production to detect and mitigate longitudinal cracks.

- Improve Casting Conditions:

Good Casting Practices: Adopt good casting practices to enhance the cleanliness of the steel, thereby reducing the likelihood of surface microcracks.

By implementing these control measures, the occurrence of surface microcracks in LSAW steel pipes can be significantly reduced, improving product quality and yield rates.