Influence of Al, Ti, V and O on acicular ferrite formation in TIG weld metal
- TWI, Cambridge (United Kingdom). Materials Dept.
An investigation has been carried out on the influence of Al, Ti and oxygen on the microstructure of TIG weld metal. In the first phase of the investigation, commercial C-Mn and C-Mn-Ni solid, flux-cored and metal-cored electrode wires, some of which contained Ti, were deposited by the hot wire TIGF process in preparations in C-Mn steel plates of two different Al levels. In the second phase, Al and Ti, both separately and together, were sputtered on to a C-Mn steel plate with a low Al level, and bead-on-plate cold wire TIG welds were produced, using a C-Mn wire, also with a low Al level. Metallographic examination of sectioned welds revealed that microstructures containing substantial amounts of fine-grained acicular ferrite were produced only where Al levels were not greatly in excess of the oxygen levels. The use of metal-cored wires increased weld oxygen levels up to {approximately}0.02%, and thus comparable levels of Al could be tolerated. In the cold wire TIG welds, where oxygen levels were {le}0.0043%, Al levels >0.005% reduced the proportion of acicular ferrite. At oxygen levels of {approximately}0.02%, in the hot wire TIG welds, a small amount of Ti ({approximately}0.005%) increased the proportion of acicular ferrite, but larger additions reduced it. At lower oxygen levels, in the cold wire TIG deposits, Ti additions {ge}0.024% reduced the proportion of acicular ferrite; however, for Al > 0.01%, Ti additions contributed to the formation of an increasing proportion of ferrite with second phase in the form of small colonies. In weld beads containing {approximately}0.02% oxygen, {approximately}0.04% V, diluted in from one of the parent steels, increased the proportion of acicular ferrite.
- OSTI ID:
- 403596
- Report Number(s):
- CONF-9606279--; ISBN 0-7918-1492-0
- Country of Publication:
- United States
- Language:
- English
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