The Effect of Preheating on Weld Defect Formation Using X-ray Radiography

Abstract

The manufacturing of long-section pipes is expensive and demands sophisticated procedures, requiring the assembly of smaller pipes by welding. Welding is essential in the oil and gas sectors and several other industries. A welding procedure was executed on two ASTM A106 grade B pipes utilizing GTAW and SMAW techniques for four layers. Testing identified a transverse crack in a welded joint (Test No-01A) at site 20, measuring 4 mm. A PMI test established the chemical composition of the weld joint. A key factor contributing to cracks is the temperature disparity between the weld zone and the base metal. To alleviate this, the joints were warmed prior to welding, The results showed that preheating the metal before the welding process reduces or prevents the occurrence of cracks 
by minimizing the temperature gradient between the base metal and the welding temperature. As the PMI test findings revealed discrepancies in the chemical composition of the welded joints prior to and subsequent to welding, attributable to chemical reactions throughout the operation. These findings underscore the influence of temperature and chemical alterations on weld integrity.