High Temperature Cracking in the Weld Heat Affected Zone of High Strength Ferritic Steels


A study has been made of the effects of steel composition and welding parameters on hot cracking in the heat affected zone of high strength ferritic steels. In addition, the hot ductility test has been studied to determine whether it is capable of distinguishing unambiguously between crack sensitive and crack resistant steels. This has involved parallel weld cracking and hot ductility tests on low alloy steels to specifications SAE 4130, EN 24 and ASTM A387B. Both composition and welding parameters were shown to have a marked influence on cracking severity. Consideration of composition confirmed the detrimental effects of carbon, sulphur and phosphorus. High levels (>0.030% wt) of either sulphur or phosphorus could cause Significant. cracking; phosphorus being the more detrimental. For a constant steel composition, cracking was found to increase with i) Increasing Heat Input/unit length; (ii) Increasing depth of finger penetration; (iii) Application of external restraint; (iv) Increasing distance along the weld bead. Metallographic and fractographic examination of welded specimens has shown that cracking occurs only within a discrete zone in the high temperature region of the H.A.Z., and is associated with the modification of MnS type inclusions. Furthermore, in the high sulphur steels, this crack susceptible zone is brittle at ambient temperatures due to extensive sulphide films at the grain boundaries. It was found that the H.A.Z. hot cracking severity of a steel could be related quantitatively to the zero ductility range, measured during the cooling portion of a simulated weld thermal cycle, providing the peak temperature was equivalent to the nil-strength temperature or above. The greatest sensitivity was achieved with a peak temperature of 12°C below the bulk melting temperature.

Divisions: College of Engineering & Physical Sciences
Additional Information: Copyright © Phillips, 1973. R.H. Phillips asserts their moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: high temperature cracking,weld heat affected zone,high strength,ferritic steels
Last Modified: 08 Dec 2023 08:03
Date Deposited: 07 Feb 2011 11:04
Completed Date: 1973
Authors: Phillips, R.H.

Export / Share Citation


Additional statistics for this record