APPLICATION OF CRACKABILITY PARAMETERS TO EVALUATE TEST RESULTS OF SELF-RESTRAINED CRACKING SPECIMENS

Weld cracking susceptibility, or simply, the weldability, is a most significant problem in utilizing high strength steels. A number of formulas have been suggested and available for the prediction of the weldability using chemical composition. Those formulas calculate various weldability criteria such as the hardness, the ductility and the amount of cracking in the heat affected zone. Ito and Bessyo have proposed crackability formulas (Pc and/or Pw) including chemical composition, weld metal hydrogen centent, plate thickness and stress-intensity. In their work they have used the y-groove restraint cracking test specimen. In this investigation, an attempt was made to evaluate test results of Tekken, Lehigh and CTS using the proposed parameters. Structural steels of different chemical composition and thickness were welded, using electrode diameters from 3.25 to 5.0 mm. Welding current was varied from 120 to 220A and welding speed from 8 to 20 cm/min. Preheating temperature range was from 25 to 150°C. Cracks were detected and evaluated in three to four transverse sections of test welds. Test results obtained using Tekken, Lehigh and CTS crackability tests are .compared and evaluated. Critical cooling time between 800 and 500°C was determined for each test condition using crackability parameters Pc and/or Pw at which crack formation starts in the welded joints. Simultanously, the abovementioned tests were ranked from severity point of view.