Steels continued high-strength


As an approximate guide, the martensitic grades of stainless steels can be defined as those alloys of iron and chromium in which %Cr — 17 x %C < 12.5, but which still contain more than li.5% Cr to give adequate corrosion resistance. On quenching such alloys from high temperatures they will traverse the 7 loop in the iron-carbon equilibrium diagram and martensite will be formed to an extent that depends upon the carbon content of the steel. Carbon contents for such steels range from 0.15 to 1.2%, depending upon the strength requirement for the steel. As their name implies, they are used in the quenched and tempered condition for components such as turbine blades, bolts, springs, valve components, cutlery etc. and in the steam generating and chemical industries for many components.  [c.1197]

The discussion so far has been limited to the structure of pure metals, and to the defects which exist in crysteds comprised of atoms of one element only. In fact, of course, pure metals are comparatively rare and all commercial materials contain impurities and, in many cases also, deliberate alloying additions. In the production of commercially pure metals and of alloys, impurities are inevitably introduced into the metal, e.g. manganese, silicon and phosphorus in mild steel, and iron and silicon in aluminium alloys. However, most commercial materials are not even nominally pure metals but are alloys in which deliberate additions of one or more elements have been made, usually to improve some property of the metal examples are the addition of carbon or nickel and chromium to iron to give, respectively, carbon and stainless steels and the addition of copper to aluminium to give a high-strength age-hardenable alloy.  [c.1270]

For many years, plastics reinforced with polymer fibers have been utilized in the manufacture of boats and sports cars. More recently, ultrahigh strength, high modulus fibers have been invented and combined into composites whose strength and stiffness on a specific basis are unmatched by conventional constmction materials. Composites are now replacing metals in such cmcial applications as aircraft and the space shuttle. The polymeric composites contain carbon or aramid fibers several times stiffer, weight for weight, than steel embedded in plastics. In composite materials (qv) the fibers support the load which is distributed by the plastic which also prevents fatigue and failure.  [c.64]

Self-lubricating bearings are also made from iron usually containing 36 wt % Cu and 4 wt % Sn. Iron—lead alloys contain 2—6 wt % Pb and 2—4 wt % graphite. Iron-base materials offer increased hardness and strength in addition, their coefficient of thermal expansion is close to that of the steel shaft. However, iron-base materials are generally not rated as high as copper-base materials for self-lubricating bearing materials.  [c.189]

Welding Hydrogen introduced into welds produces a particularly acute problem, as the weld and the heat-affected zone are inevitably regions of high residual stresses, contain inherent defects and are frequently intrinsically more brittle than the parent material. Thus it is important to minimise the introduction of hydrogen into welds, even for lower strength steels. Gas welding of steels using an oxyacetylene flame will inevitably introduce hydrogen as a result of the hydrogen-containing gases in the flame. In theory electric-arc welding, particularly if the arc is protected from atmospheric moisture by inert gas shielding, will not introduce hydrogen. However, with normal manual metal arc welding using flux-coated electrodes it is possible for the flux coating to absorb moisture from the atmosphere, and this will react with the molten steel to produce hydrogen. For this reason it is good practice to store coated welding electrodes in an oven in order to drive off any moisture (Section 9.5).  [c.1234]

Of the common alloying elements in steel (qv), molybdenum is the most effective in increasing creep—mpture strength, and the carbon—molybdenum steels generally have more than twice the creep—mpture strength of plain carbon steel at the same temperature (34). The most commonly used steels for high temperature service contain from 0.5 to 1.5% molybdenum. Carbon—molybdenum steels are about equivalent to plain carbon steels in metallurgical stabiUty and resistance to corrosion and oxidation, and are therefore used where greater strength is needed, although plain carbon steel would otherwise be acceptable. The straight carbon—molybdenum steels should not be used continuously above 470°C because of graphiti2ation, ie, the breakdown of the cementite present in the peaditic stmcture to form ferrite and carbon in the form of graphite flakes.  [c.117]


See pages that mention the term Steels continued high-strength : [c.2449]    [c.1306]    [c.51]    [c.130]   
Corrosion, Volume 2 (2000) -- [ c.3 , c.8 , c.13 , c.15 , c.27 , c.78 ]