The in uence of intercritical deformation on the microstructure development of a TRIP steel has been investigated by the use of deformation dilatometry, X-ray diffraction, and metallography. The austenite decomposition into ferrite and bainite during cooling from the intercritical annealing and the bainitic annealing have been investigated. A very distinct effect of plastic deformation on the microstructural development has been observed. Since the plastic deformation enhances the ferrite formation during cooling, the degree of deformation can be used to control the balance between allotriomorphic ferrite and bainitic ferrite in the eventual structure. In this paper a semiquantitative phase map has been developed, showing the microstructural composition of the material as a function of the degree of plastic deformation. Using this map the in uence of the intercritical deformation on the microstructure development can be followed.MST/5834

Wire-arc additive manufacturing has become an alternative way to produce industrial parts. In this work 15 kg walls are built with an effective building rate of 4.85 kg/h using an ER100 wire providing good tensile properties and toughness under welding conditions. The thermal evolution of the walls during manufacturing is measured by thermocouples and an IR camera: it depends on process parameters, deposit strategy and the size of the part. The walls are then characterised as deposit and after heat treatment through hardness, tensile and Charpy-V notch tests. The results show a fine microstructure with unexpected retained austenite and coarse allotriomorphic ferrite in the as deposited walls. The final hardness values vary from about 220 to 280 HV2; the yield stress and tensile strength are 520 and 790 MPa, respectively, and a toughness of about 50 J is obtained at room temperature. The heat treatment transforms the retained austenite, leading to an improvement of the yield stress to 600 MPa.

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A new cladding material based on the Fe-Cr-Mo-V-C alloy system, suitable for submerged arc welding, has been designed for the refurbishment of forged and cast backup rolls used in the finishing stands of hot strip rolling mills. The work undertaken includes mechanical analysis, mechanical testing, and microstructural characterisation. The mechanical analysis indicated the nature and level of stresses operating near the surface of rolls; mechanical testing allowed material performance to be anticipated. An optimal post-weld heat treatment procedure, which maximises strength while minimising material strain hardening, was subsequently chosen. The microstructure of the candidate cladding material is a mixture of lower bainite and martensite, containing a very fine distribution of molybdenum carbides. In situ results have shown that welded rolls outperform traditional rolls, as the amount of steel rolled per millimetre of cladding material is 40% higher than with forged rolls and double that obtained with cast rolls.MST/4457