High strength steel in fire

High-performance materials are necessary to meet the future demands of the construction industry, which is strongly influenced by a growing population and depletion of natural resources. Sustainable development is central to research and development into innovative structural materials, and requires solutions to be economically viable whilst equally providing a positive contribution towards environmental and social factors. High strength steels (HSS) have the potential to contribute towards such demands by reducing the weight of structures when employed in appropriate applications. Lighter structures require smaller foundations, shorter transportation and construction times and also lower CO2 emissions. A particular challenge related to the use of HSS in structures include increased likelihood of stability issues resulting from the reduction in section thickness, and limiting deflection and vibration criteria are also more likely to be critical. Nevertheless, when used appropriately, they can provide a sustainable solution. Their use in structural applications is further hindered by a lack of performance data and design guidance under fire conditions. This paper compares the mechanical properties, particularly strength and stiffness of HSS (yield strengths between 460-700 MPa) and mild steel (yields between 235-460 MPa) at elevated temperatures, through a critical review of published literature. Various alloying and processing routes used to achieve high yield strength are assessed. At the same time, the review considers available information on the strengthening mechanisms that can be utilised to retain the strength and/or stiffness of the material in the event of a fire. Using the information gathered, an extensive testing programme is developed which will enable design guidance for the fire design of HSS structures to be proposed.Engineering and Physical Sciences Research Council, TW

Behaviour of concrete filled stainless steel elliptical hollow sections

This paper presents the behaviour and design of axially loaded concrete filled stainless steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30 and 100 MPa. The current study is based on stub column tests and is therefore limited to cross-section capacity. Based on the existing design guidance in Eurocode 4 for composite columns, the proposed design equations use the continuous strength method to determine the strength of the stainless steel material. It is found to provide the most accurate and consistent prediction of the axial capacity of the composite concrete filled stainless steel elliptical hollow sections due largely to the more precise assessment of the contribution of the stainless steel tube to the composite resistance

Fatigue of Bolted High Strength Structural Steel

published or submitted for publicatio

High-strength braze joints between copper and steel

High-strength braze joints between copper and steel are produced by plating the faying surface of the copper with a layer of gold. This reduces porosity in the braze area and strengthens the resultant joint

Aluminum/steel wire composite plates exhibit high tensile strength

Composite plate of fine steel wires imbedded in an aluminum alloy matrix results in a lightweight material with high tensile strength. Plates have been prepared having the strength of titanium with only 85 percent of its density

Engineering Performance Of High Strength Concrete Containing Steel Fibre Reinforcement

The development and utilization of the high strength concrete in the construction industry have been increasing rapidly. Fiber reinforced concrete is introduced to overcome the weakness of the conventional concrete because concrete normally can crack under a low tensile force and it is known to be brittle. Steel fibre is proved to be the popular and best combination in the high strength concrete to result the best in the mechanical and durability properties of high strength concrete with consideration of curing time, steel fibre geometry, concrete grade and else more. The incorporation of steel fibre in the mortar mixture is known as steel fibre reinforced concrete have the potential to produce improvement in the workability, strength, ductility and the deformation of high strength concrete. Besides that, steel fibre also increases the tensile strength of concrete and improves the mechanical properties of the steel fibre reinforced concrete. The range for any high strength concrete is between 60MPa-100MPa. Steel fibre reinforced concrete which contains straight fibres has poorer physical properties than that containing hooked end stainless steel fibre due to the length and the hooked steel fibre provide a better effective aspects ratio. Normally, steel fibre tensile strength is in the range of 1100MPa-1700MPa. Addition of less steel fibre volumes in the range of 0.5% to 1.0% can produce better increase in the flexural fatigue strength. The strength can be increased with addition of steel fibre up to certain percentage. This paper will review and present some basic properties of steel fibre reinforced concrete such as mechanical, workability and durability properties

Corrosion fatigue of high strength fastener materials in seawater

Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure

The characteristics of a high-power diode laser fired enamel coating on a carbon steel

Significant changes to the wettability characteristics of a common engineering carbon steel(EN8) were effected after high power diode laser (HPDL) surface treatment. These modifications havebeen investigated in terms of the changes in the surface roughness of the steel, the presence of any surface melting, the polar component of the steel surface energy and the relative surface O2 content of the steel. The morphological and wetting characteristics of the mild steel and the enamel were determined using optical microscopy, scanning electron microscopy, X-ray photoemission spectroscopy, energy-dispersive X-ray analysis and wetting experiments by the sessile drop technique. This work has shown that HPDL radiation can be used to alter the wetting characteristics of carbon steel so as to facilitate improved enamelling. Furthermore, standard mechanical, physical and chemical testing of the HPDL-fired enamel glaze revealed the glaze to possess similar properties to those of a conventionally fired enamel glaze in terms of bond strength, rupture /impact strength, wear and corrosion resistance. Such similar performance can be attributed to the two glazes possessing the same mechanical properties and similar amorphous structure, despite their very different firing techniques

Twin-induced plasticity of an ECAP-processed TWIP steel

The TWIP steels show high strain hardening rates with high ductility which results in high ultimate tensile strength. This makes their processing by equal channel angular pressing very difficult. Up to now, this has only been achieved at warm temperatures (above 200 °C). In this paper, a FeMnCAl TWIP steel has been processed at room temperature and the resulted microstructure and mechanical properties were investigated. For comparison, the material has also been processed at 300 °C. The TWIP steel processed at room temperature shows a large increase in yield strength (from 590 in the annealed condition to 1295 MPa) and the ultimate tensile strength (1440 MPa) as a consequence of a sharp decrease in grain size and the presence within the grains of a high density of mechanical twins and subgrains. This dense microstructure results also in a loss of strain hardening and a reduction in ductility. The material processed at 300 °C is more able to accommodate deformation and has lower reduction in grain size although there is a significant presence of mechanical twins and subgrains produced by dislocation activity. This material reaches an ultimate tensile strength of 1400 MPa with better ductility than the room temperature material.Postprint (published version

Experimental X-ray Stress Analysis Procedures for Ultra High Strength Materials

X-ray stress analysis procedures for accurate measurement of elastic strain in high strength steel