| i'm walking along with a carnival. though the streets of rome. and i can sense him. i'm with someone, a friend. and i can see an archway. its big. i take them over and there is a door on the right that opens on a small room. only big enough to fit a ... Read more of us in rome at My Dreams.ca |  InformationalPrivacy |
Steel MakingTool Or Crucible SteelCrucible steel can be annealed either in muffled furnace or b... Sulphur Sulphur is another impurity and high sulphur is even a greate... Heat Treatment Of Lathe Planer And Similar Tools FIRE.--For these tools a good fire is one made of hard foundr... Gas Consumption For Carburizing Although the advantages offered by the gas-fired furnace for ... Steel For Chisels And Punches The highest grades of carbon or tempering steels are to be re... Effects Of Proper Annealing Proper annealing of low-carbon steels causes a complete solu... Rate Of Cooling At the option of the manufacturer, the above treatment of gea... Preventing Cracks In Hardening The blacksmith in the small shop, where equipment is usually ... Protective Screens For Furnaces Workmen needlessly exposed to the flames, heat and glare from... Hardening Carbon Steel For Tools For years the toolmaker had full sway in regard to make of st... Quenching Tool Steel To secure proper hardness, the cooling of quenching of steel ... Fatigue Tests It has been known for fifty years that a beam or rod would fa... Hardening The forgings can be hardened by cooling in still air or quen... Carbon Steels For Different Tools All users of tool steels should carefully study the different... For Milling Cutters And Formed Tools FORGING.--Forge as before.--ANNEALING.--Place the steel in a ... Temperature Recording And Regulation Each furnace is equipped with pyrometers, but the reading an... Robert Mushet Robert (Forester) Mushet (1811-1891), born in the Forest of D... Mushet And Bessemer That Mushet was "used" by Ebbw Vale against Bessemer is, perh... Restoring Overheated Steel The effect of heat treatment on overheated steel is shown gra... Brown Automatic Signaling Pyrometer In large heat-treating plants it has been customary to mainta... |
ChromiumCategory: ALLOYS AND THEIR EFFECT UPON STEEL Chromium when alloyed with steel, has the characteristic function of opposing the disintegration and reconstruction of cementite. This is demonstrated by the changes in the critical ranges of this alloy steel taking place slowly; in other words, it has a tendency to raise the Ac range (decalescent points) and lower the Ar range (recalescent points). Chromium steels are therefore capable of great hardness, due to the rapid cooling being able to retard the decomposition of the austenite. The great hardness of chromium steels is also due to the formation of double carbides of chromium and iron. This condition is not removed when the steel is slightly tempered or drawn. This additional hardness is also obtained without causing undue brittleness such as would be obtained by any increase of carbon. The degree of hardness of the lower-chrome steels is dependent upon the carbon content, as chromium alone will not harden iron. The toughness so noticeable in this steel is the result of the fineness of structure; in this instance, the action is similar to that of nickel, and the tensile strength and elastic limit is therefore increased without any loss of ductility. We then have the desirable condition of tough hardness, making chrome steels extremely valuable for all purposes requiring great resistance to wear, and in higher-chrome contents resistance to corrosion. All chromium-alloy steels offer great resistance to corrosion and erosion. In view of this, it is surprising that chromium steels are not more largely used for structural steel work and for all purposes where the steel has to withstand the corroding action of air and liquids. Bridges, ships, steel building, etc., would offer greater resistance to deterioration through rust if the chromium-alloy steels were employed. Prolonged heating and high temperatures have a very bad effect upon chromium steels. In this respect they differ from nickel steels, which are not so affected by prolonged heating, but chromium steels will stand higher temperatures than nickel steels when the period is short. Chromium steels, due to their admirable property of increased hardness, without the loss of ductility, make very excellent chisels and impact tools of all types, although for die blocks they do not give such good results as can be obtained from other alloy combinations. For ball bearing steels, where intense hardness with great toughness and ready recovery from temporary deflection is required, chromium as an alloy offers the best solution. Two per cent chromium steels; due to their very hard tough surface, are largely used for armor-piercing projectiles, cold rolls, crushers, drawing dies, etc. The normal structure of chromium steels, with a very low carbon content is roughly pearlitic up to 7 per cent, and martensitic from 8 to 20 per cent; therefore, the greatest application is in the pearlitic zone or the lower percentages. Next: Nickel-chromium Previous: Nickel
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