Steel physical properties

Despite variatioas ia hardness test procedures and the variations ia physical properties of the materials tested, hardness conversions from one test to another are possible (see ASTM E140 and Table 2). This approximate relationship is only consistent within a single-material system, eg, iron, steel, or aluminum. 

Calcium—Silicon. Calcium—silicon and calcium—barium—siUcon are made in the submerged-arc electric furnace by carbon reduction of lime, sihca rock, and barites. Commercial calcium—silicon contains 28—32% calcium, 60—65% siUcon, and 3% iron (max). Barium-bearing alloys contains 16—20% calcium, 9—12% barium, and 53—59% sihcon. Calcium can also be added as an ahoy containing 10—13% calcium, 14—18% barium, 19—21% aluminum, and 38—40% shicon These ahoys are used to deoxidize and degasify steel. They produce complex calcium shicate inclusions that are minimally harm fill to physical properties and prevent the formation of alumina-type inclusions, a principal source of fatigue failure in highly stressed ahoy steels. As a sulfide former, they promote random distribution of sulfides, thereby minimizing chain-type inclusions. In cast iron, they are used as an inoculant. 

The durabihty and versatility of steel are shown by its wide range of mechanical and physical properties. By the proper choice of carbon content and alloying elements, and by suitable heat treatment, steel can be made so soft and ductile that it can be cold-drawn into complex shapes such as automobile bodies. Conversely, steel can be made extremely hard for wear resistance, or tough enough to withstand enormous loads and shock without deforming or breaking. In addition, some steels are made to resist heat and corrosion by the atmosphere and by a wide variety of chemicals. 

In general, steel having similar chemical compositions have similar mechanical and physical properties, no matter by which process they are made, unless the patterns of inclusions (oxides, siHcates, and sulfides) are very different. 

Zinc dust is used in the sherardizing process where work pieces are tumbled with zinc dust in rotating steel dmms which are heated electrically or by gas to 370—420°C (149). The steel parts are uniformly coated with zinc. In the chemical and metallurgical industries, zinc dust is used as a reducing agent, in the manufacture of hydrosulfite compounds for the textile and paper industries, and to enhance the physical properties of plastics and lubricants (2). 

Zirconium is a hard, shiny, ductile metal, similar to stainless steel in appearance. It can be hot-worked to form slabs, rods, and rounds from arc-melted ingot. Further cold-working of zirconium with intermediate annealings produces sheet, foil, bar wire, and tubing. Physical properties are given in Table 3. 

Selected physical properties of oxygen are included in Table 9.24. It is a colourless, odourless and tasteless gas which is essential for life and considered to be non-toxic at atmospheric pressure. It is somewhat soluble in water and is slightly heavier than air. Important uses are in the steel and glass industries, oxyacetylene welding, as a chemical intermediate, waste-water treatment, fuel cells, underwater operations and medical applications. 

Steel. Steel shall conform to one of the applicable ASTM specifications referred to by applicable AISC specifications. Other steels not covered by these specifications may be used provided that the chemical and physical properties conform to the limits guaranteed by the steel manufacturer. Structural steel shapes having specified minimum yield less than 33,000 psi shall not be used. Certified mill test report or certified reports of tests made in accordance with ASTM A6 and the governing specification shall constitute evidence of conformity with one of the specifications listed. 

Steel is essentially iron with a small amount of carbon. Additional elements are present in small quantities. Contaminants such as sulfur and phosphorus are tolerated at varying levels, depending on the use to which the steel is to be put. Since they are present in the raw material from which the steel is made it is not economic to remove them. Alloying elements such as manganese, silicon, nickel, chromium, molybdenum and vanadium are present at specified levels to improve physical properties such as toughness or corrosion resistance. 

While a metal or alloy may be selected largely on the basis of its mechanical or physical properties, the fact remains that there are very few applications where the effect of the interaction of a metal with its environment can be completely ignored, although the importance of this interaction will be of varying significance according to circumstances for example, the slow uniform wastage of steel of massive cross section (such as railway lines or sleepers) is of far less importance than the rapid perforation of a buried steel pipe or the sudden failure of a vital stressed steel component in sodium hydroxide solution. 

The basic corrosion behaviour of stainless steels is dependent upon the type and quantity of alloying. Chromium is the universally present element but nickel, molybdenum, copper, nitrogen, vanadium, tungsten, titanium and niobium are also used for a variety of reasons. However, all elements can affect metallurgy, and thus mechanical and physical properties, so sometimes desirable corrosion resisting aspects may involve acceptance of less than ideal mechanical properties and vice versa. 

Typical physical properties for a selection of steels are given in Table 3.15. 

Table 3.15 Physical properties of some stainless steels...

The metals most used for corrosion protection by metal spraying are aluminium and zinc, both of which are anodic to steel in most environments. Physical properties of these coatings are shown in Table 12.6. 

Loop Tests Loop test installations vary widely in size and complexity, but they may be divided into two major categories (c) thermal-convection loops and (b) forced-convection loops. In both types, the liquid medium flows through a continuous loop or harp mounted vertically, one leg being heated whilst the other is cooled to maintain a constant temperature across the system. In the former type, flow is induced by thermal convection, and the flow rate is dependent on the relative heights of the heated and cooled sections, on the temperature gradient and on the physical properties of the liquid. The principle of the thermal convective loop is illustrated in Fig. 19.26. This method was used by De Van and Sessions to study mass transfer of niobium-based alloys in flowing lithium, and by De Van and Jansen to determine the transport rates of nitrogen and carbon between vanadium alloys and stainless steels in liquid sodium. 

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