Various Grades Of Steel Research Articles

Energy absorption by metal-vapor-dominated plasma during carbon dioxide laser welding of steels

During laser welding, the plasma plume affects the amount of energy reaching the weld surface and the composition and properties of the welds. Light emissions during welding were recorded by emission spectroscopy to understand the energy absorption and the nature of the plasma formed during welding of various grades of steels. The flow of gases and the concentrations of the various metal vapors were computed by solving the Navier Stokes equation and the equations of conservation of various species. The variables studied were shielding gas composition and flow rate and the base metal composition. Until now, self-absorption of emissions arising from species present at high concentrations within the plasma has kept researchers limited to either analyzing ideal situations that are unrelated to the welding process or not accounting for the attenuation of the emissions. It is demonstrated that during welding, the peaks in the emission spectra that are affected by the self-absorption process can be eliminated on the basis of the initial and the terminal energy levels for electronic transitions. By selectively eliminating the affected transitions and by using the numerically computed local concentrations of metal vapors, the absorption of the laser beam energy by the plasma can be accurately determined.

Glass-ceramic Coatings for Steel and Nimonic Alloy

A number of TiO2 and P2O5 nucleated glass-ceramic coating compositions in the system RO-R′2O-Al2O3-SiO2 (R = Ca, Mg; R′ = Na, K, Li) have been studied for application on various grades of steel and alloy with a view to protecting them against mechanical wear and chemical corrosion. Good adhesion of the coating has been obtained on mild steel, stainless steel and nimonic alloy. The conventional technique has been used in the preparation and application of the coating material. The nucleation and crystal growth have been achieved by suitable heat-treatment schedule of the coated specimen. The properties of the coatings with respect to resistance towards abrasion, impact, high temperature, thermal shock and chemical corrosion have been evaluated and found to be superior to those of the conventional vitreous enamel coatings. X-ray and electron microscopic studies have been used to analyse the crystalline phases formed in the coating during the heat-treatment process. The unique combination of properties achie...

Punch friction tests for sheet metal forming

A previously described tensile strip test which simulates the stretching of sheet over a punch corner radius in a typical draw die was used to compare frictional effects in different sheet materials. Various grades of steel including galvanized samples were tested as well as soft and age-hardening aluminum alloy sheets. The measured friction coefficients varied over a wide range and the experiments illustrate how the straining process over the punch is influenced by both the stress-strain curve of the sheet and its friction characteristics.

The reinstatement of fire damaged steel framed structures

The paper examines the factors which can cause steelwork to distort and collapse during fires. In many situations no distortion occurs and the steelwork may be reused. Laboratory based experiments are described in which the strengths of various grades of steel were determined at elevated temperatures. The effects on mechanical properties of heating steelwork to temperatures in the range 100 — 1000°C and cooling back to ambient temperature have also been assessed. It has been shown that mild and microalloyed steels are likely to show distortion or collapse if they are heated to temperatures above 600°C, but no deterioration in mechanical properties occurs on cooling back to room temperature until steel temperatures have exceeded 650 °C. The available data on cast and wrought iron in fires are also summarised; these materials show similar behaviour to that of steels. Metallurgical examinations of several samples retrieved from the frameworks of structures involved in fires are included. Some guidelines are presented describing the major factors to be considered when contemplating the reinstatement of a steel framework after a fire. However, decisions on reinstatement need to be taken in the light of expert engineering and metallurgical advice in each individual case. This paper is intended for guidance purposes only and is not intended to be used as a definitive reference for such decisions.

Ion nitriding of steels

This paper deals with the ’’ion-nitriding’’ method of nitriding various grades of steels in a laboratory model furnace. Four different grades of steels such as AISI 4140, Nitralloy 135 Mod., high-speed steel M2 and stainless steel 304 were ion nitrided at different temperatures with cycle times ranging from 1 to 36 h in a gaseous mixture of nitrogen and hydrogen under a total pressure of 7 Torr (9.1×103 Pa). Results obtained with 4140 steel show that ion nitriding at 950°F is much faster than conventional gaseous nitriding. At a given temperature of ion nitriding, case depth versus treatment time follows a parabolic law for all four grades of steels. Current theoretical and experimental evidence has been used to explain different nitriding rates observed for various steels. Finally results of ion nitriding performed at 750°F have been presented to show the versatility of this process.

Optimum least-cost design of a truss roof system

An algorithm is presented encompassing the application of optimization methods to the least-cost elastic design of roof systems composed of rigid steel trusses, web joists and steel roof deck. The method is capable of designing rigid trusses that can be fabricated from various grades of steel and several types of standard sections. The selection of open web joist is presently limited to standard H-series, and decking material is standard 22 gage. The design is based upon AISC allowable values where combined stresses resulting from axial forces and secondary bending moments are considered. The effective column lengths are computed using the characteristic buckling equation for a member whose ends are elastically restrained against rotation. The procedure developed considers changes in the mechanical properties of the members, geometric variations in the truss configuration and changes in topology. Selected sets of members may be chosen to be identical, and chord members may be defined as continuous over several panels. Also investigated is the problem of finding the design containing the optimum number of trusses. A number of examples are presented which demonstrate the flexibility and generality of the design approach developed.

Protection of Steel Bridges From Corrosion

AbstractAtmospheric corrosion is only one of many causes of deterioration of structures, and protective measures applied to bridges are usually successful, in the sense that disasters resulting from corrosion are rare. Most bridge steelwork requires careful protection and regular inspection and maintenance, though in certain circumstances various grades of steel can be left uncoated. Depending on the intended life of a bridge, the procedure which in the long run is the most economic is usually one which employs a high standard of initial protection, so that unnecessarily frequent repainting is avoided. The circumstances in which steel piles can safely be used to support a bridge structure are briefly discussed. The protection of superstructure steelwork begins at the design stage, when much can be done to minimise subsequent corrosion troubles. Guidance is given on the choice of protective films, with or without a preliminary coating of non-ferrous metal. The standard of surface preparation needed for eac...

Vacuum arc re-melting and its influence on mechanical properties of steels

Vacuum arc re-melting was compared with conventional melting and pouring with regard to the resultant mechanical properties and overall steel quality. Various grades of steel were tested and the results indicate that the vacuum arc re-melting has a favourable influence on all properties of the steel produced. Most pronounced benefits were found to be: reduction of gas and oxide contents; improved homogeneity of the ingots obtained; improved ductility; greater uniformity of properties in the transverse and longitudinal directions; improved fatigue properties; and uniformity of chemical composition.

Coefficient of Friction in Joints of Various Steels

The coefficient of friction in bolted joints made of various grades of steels and of variable number of faying surfaces was studied and values are presented. A test suitable for standardization is proposed for slip tests.

Development of operating and metallurgical practices for Lukens’ 150-ton vacuum degassing unit

The operating and metallurgical practices for the Lukens 150-ton D-H vacuum degassing unit have been developed through studies of the kinetics of the hydrogen and oxygen removal processes and supplemented by material property evaluations and statistical analyses of plant quality control data. In this manner, vacuum treatment procedures have been tailored to meet the end-point quality requirements for the various grades of steel that Lukens produces.

Intensification of heat-treatment processes

1. The mechanical properties do not depend on overheating characterized by the appearance of coarse-grain structure. 2. For various grades of steel the static strength is stable after quenching in oil from temperatures of the “extreme range”. The plasticity characteristics of steel quenched from the extreme range temperatures may be controlled by proper tempering conditions. 3. The stability of the high static strength indices for all steels quenched from the “extreme-range” temperatures is attributable to the homogenization of the solid solution, increased density of dislocations at the austenite grain boundaries, the refinement of the mosaic blocks, and the formation of an optimal fine structure due to phase hardening resulting fromα→γ transformation in the process of heating.

The Strength and Elasticity of Structural Steel and its Efficiency in the form of Beams and Struts

The various grades of steel used in structures possess such an extended range of physical properties, that it is impossible to consider the metal in its individual sense, as we might treat of iron. The character of steel is so largely determined by the various agents that enter into its composition, that a complete description of any particular grade involves a consideration of these agents.