Investigation on retained delta ferrite occurrence and its influence on HSS and Semi HSS Strengthening after thermomecanical routes

in Proceedings of Abrasion 2008 (2008)

The present work deals with use of DTA tests in order to understand the crystallisation behaviour of semi-HSS and HSS alloys, and to enhance their solid state transformations. Emphasis is laid on the ... [more ▼]

The present work deals with use of DTA tests in order to understand the crystallisation behaviour of semi-HSS and HSS alloys, and to enhance their solid state transformations. Emphasis is laid on the decomposition of the unexpected retained delta ferrite during thermal and thermomechanical treatment. [less ▲]

Fractography survey on high cycle fatigue failure: Crack origin characterisation and correlations between mechanical tests and microstructure in Fe-C-Cr-Mo-X alloys

in International Journal of Fatigue (2007), 29(4), 713-728

Raw materials were cast from different specific processes in order to produce cleaner steels with a reduced amount of inclusions. Studied materials that are HSS hardened alloys belonging to the Fe-Cr-C-X ... [more ▼]

Raw materials were cast from different specific processes in order to produce cleaner steels with a reduced amount of inclusions. Studied materials that are HSS hardened alloys belonging to the Fe-Cr-C-X system were shared out in four groups depending on the tempering temperature and the presence of secondary and primary carbides. Both inclusions and carbides were roughly assessed by means of Image Analysis. Forging was done on all studied materials with different reduction ratios in order to highlight the texture influence oil mechanical properties. High cycle fatigue tests were made using the boundary method to allow a quick evaluation of results. Fractographic analyses carried out on broken samples led to the definition of four failure modes depending on the nature and the location of the point from which the crack was initiated in one hand, and the roughness of striations in the propagating area over and around the initiation point. Internal and surface crack initiation points were found, the latter being more harmful than the first ones. Though oxides appeared to be more detrimental than other inclusions, primary carbides were also found to be both crack initiation candidates and crack propagation enhancers. Various parameters likely to influence high cycle fatigue failures were finally defined, the most significant one dealing with the nature and location of embedded precipitates and the forging reduction ratio. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

Metallurgical assessment of two HSS rolls grades for Hot Strip Mill

in AISTech-Proceedings of the Iron and Steel Technology Conference (2007)

Aurora and Kosmos grades are HSS alloys used for the manufacturing of rolling mill work rolls for early finishing stands of Hot Strip Mills. Both alloys were metallurgically assessed using Electron ... [more ▼]

Aurora and Kosmos grades are HSS alloys used for the manufacturing of rolling mill work rolls for early finishing stands of Hot Strip Mills. Both alloys were metallurgically assessed using Electron Microscopy, X Rays analysis on carbides and Differential Thermal Analysis. These methods allow a better understanding of the behaviour of the studied alloys during solidification and cooling. Some mechanical tests were also performed. A connection between the laboratory results and the performance in operation of both grades is performed. The strong metallurgical differences especially as concern the nature and amount of carbides allow to explain the good behaviour in service of Aurora. [less ▲]

Use of Microscopy for identification of complex MC, M2C, M6C, M7C3 and M23C6 carbides in high speed-steels

in GIT - Imaging and Microscopy (2005), 2

High-speed steels (HSSJ rofis are useci in front finishing stands of hot strip mils. Good wear resistance and hardness at high temperature are defining features of HSS. Many types of carbides are present ... [more ▼]

High-speed steels (HSSJ rofis are useci in front finishing stands of hot strip mils. Good wear resistance and hardness at high temperature are defining features of HSS. Many types of carbides are present in these alloys, each having different effect upon the final properties of HSS. As a resuit, nature, morphology and amount of these carbides are factors of important concern. Identification and characterisation of HSS carbides are realised with optical microscopy comhined with electron microscopy. [less ▲]

Effet des inclusions et des carbures dans des aciers et fontes fortement alliés, soumis à des sollicitations mécaniques sévères

Report (2004)

Structural investigations of HSS rolls for hot strip mill

in Proceedings of the 41st Rolling Seminar Processes, Rolled and Coated Product (2004)

High Speed Steel (HSS) cast rolls are used in front finishing stands of hot strip mills (HSM). Good wear resistance and hardness at high temperatures, are defining features of HSS. Previous experience has ... [more ▼]

High Speed Steel (HSS) cast rolls are used in front finishing stands of hot strip mills (HSM). Good wear resistance and hardness at high temperatures, are defining features of HSS. Previous experience has shown that HSS rolls containing mainly hard MC carbides have a high friction coefficient, which is detrimental for the rolling power consumption and for the strip surface quality. On the other hand, HSS rolls containing eutectic rod shaped carbides are brittle and more susceptible to spalling. To overcome these problems, a suitable grade, called HSS7, that gives the best compromise between a low friction coefficient and a high crack propagation and wear resistance was developed. That alloy contains well-dispersed hard VC carbides improving wear, and non-interconnected eutectic carbides of the M2C and M7C3 type, hindering crack propagation. All the metallurgical factors affecting the performance and damage of under rolling condition in front finishing stands are reviewed: wear resistance, friction coefficient, resistance to rolling incident, and oxide film formation. The effect of nature, morphology and amount was for each of the carbides studied and connected to the factor affecting the behaviour of the new grade developed. Different techniques are used such as: differential thermal analysis, optical and electron scanning microscopy and image analysis. A correlation with mechanical properties was also performed. [less ▲]

Inclusions and Carbides characterisation in High-Speed Steels

in Proceedings de la journée de la société belge de microscopie (SBM-BVM), RUCA, UA (2003)

Prior to assessment of inclusions and carbides is the identification of thes particles. The present survey shows how we determine the nature of inclusions and carbides, while using Scanning Electron ... [more ▼]

Prior to assessment of inclusions and carbides is the identification of thes particles. The present survey shows how we determine the nature of inclusions and carbides, while using Scanning Electron Microscopy and Energy Dispersive Spectroscopy with X-Rays. [less ▲]

Relation entre la nature et la distribution des carbures et les propriétés mécaniques sur des cylindres de laminage à chaud (HSS)

Report (2002)

Microscopic identification of complex MC, M2C, M7C3, M6C and M23C6 carbides in high-speed steels

in Proceedings of The International Conference Joint Microscopic Meeting (2002)

High-speed steels (HSS) rolls are used in front finishing stands of hot strip mills. Good wear resistance and hardness at high temperature are defining features of HSS. Many types of carbides are present ... [more ▼]

High-speed steels (HSS) rolls are used in front finishing stands of hot strip mills. Good wear resistance and hardness at high temperature are defining features of HSS. Many types of carbides are present in these alloys, each having different effect upon the final properties of HSS. As a result, nature, morphology and amount of these carbides are factors of important concern. Identification and characterisation of HSS carbides were realised with optical microscopy combined with electron microscopy. [less ▲]

Microscopic determination of the nature of MC, M2C, M7C3 (M6C) carbides in high speed steels.

in Proceedings of the Annual Meeting of the SBM (société belge de microscopie), Probing the molecular level. (2001)

The present work shows the procedure used to determine the nature of carbides, while using Scanning Electron Microscopy and Energy Dispersive Spectroscopy with X-rays. Then we lay emphasis on optical ... [more ▼]

The present work shows the procedure used to determine the nature of carbides, while using Scanning Electron Microscopy and Energy Dispersive Spectroscopy with X-rays. Then we lay emphasis on optical characterization of carbides. Optical characterization of carbides appear to be the preliminary stage for the general assessment of carbides in HSS microstructure, the final stage of the scheme being the correlation between microstructure parameters (carbides and matrix) and mechanical properties of HSS hot rolling mills rolls. [less ▲]