High strength long products with improved toughness and fatigue resistance
In the transportation industry and structural applications, there is an ongoing search for steels and processes that allow for increasing strength, maintaining enough toughness and, at the same time, reducing the weight and cost of the component. In addition to toughness criteria, stringent fatigue requirements also have to be satisfied since many components undergo cycling stressing during service. At present, the classical quenched and tempered (Q&T) low alloy steels are used. A novel design approach to increase toughness, in addition to ferrite grain refinement and reduction/elimination of pearlite, is the introduction of non-traditional microstructures of acicular ferrite, martensite and retained austenite (RA). This project was devoted to define steel chemistry and process conditions in order to achieve the following target mechanical properties on rods and wires: a) rods of 10 to 60 mm diameter with ultimate tensile strength in the range 900 to 1400 MPa, and enough toughness (Charpy V-notch energy = 30 J at -60°C); b) wire-rod of 10 to 20 mm diameter, able to reach in the as-rolled condition or after cold deformation/drawing an ultimate tensile strength in the range of 800 to 1300 MPa, with good toughness, ductility and fatigue resistance. The effect of chemical composition and thermo-mechanical process on the phase transformation and mechanical properties of multiphase / bainite steel wire-rods and drawn wires was investigated by thermal-metallurgical models, laboratory tests (dilatometry, thermo-mechanical simulators) and industrial trials, in order to identify new steel grades and practicable operating conditions for obtaining the desired products. An assessment of properties such as strength, ductility, toughness and fatigue resistance for these mixed microstructures was carried out.
Bibliographic Reference: EUR 23855 EN (2009), 151 pp. Euro: 20
Availability: http://bookshop.europa.eu/is-bin/INTERSHOP.enfinity/WFS/EU-Bookshop-Site/en_GB/-/EUR/ViewPublication-Start?PublicationKey=KINA23855 (Catalogue Number: KI-NA-23855-EN-S)
ISBN: ISBN: 978-92-79-11302-4
Record Number: 200910470 / Last updated on: 2009-10-12
Original language: en
Available languages: en