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Steel MakingProperties Of SteelSteels are known by certain tests. Early tests were more or l... Preventing Carburizing By Copper-plating Copper-plating has been found effective and must have a thick... Annealing Alloy Steel The term alloy steel, from the steel maker's point of view, r... Typical Oil-fired Furnaces Several types of standard oil-fired furnaces are shown herew... Impact Tests Impact tests are of considerable importance as an indication ... Calibration Of Pyrometer With Common Salt An easy and convenient method for standardization and one whi... Uses Of The Various Tempers Of Carbon Tool Steel DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres... Quenching It is considered good practice to quench alloy steels from th... Cyanide Bath For Tool Steels All high-carbon tool steels are heated in a cyanide bath. Wi... Restoring Overheated Steel The effect of heat treatment on overheated steel is shown gra... Silicon Silicon prevents, to a large extent, defects such as gas bubb... Tool Or Crucible Steel Crucible steel can be annealed either in muffled furnace or b... Alloying Elements Commercial steels of even the simplest types are therefore p... Carbon Tool Steel Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham... Classifications Of Steel Among makers and sellers, carbon tool-steels are classed by g... Temperature Recording And Regulation Each furnace is equipped with pyrometers, but the reading an... Introduction Of Carbon The matter to which these notes are primarily directed is the... Brown Automatic Signaling Pyrometer In large heat-treating plants it has been customary to mainta... Preventing Cracks In Hardening The blacksmith in the small shop, where equipment is usually ... Sulphur SULPHUR is another element (symbol S) which is always found i... |
Preventing Cracks In HardeningCategory: HARDENING CARBON STEEL FOR TOOLS The blacksmith in the small shop, where equipment is usually very limited, often consisting of a forge, a small open hard-coal furnace, a barrel of water and a can of oil must have skill and experience. With this equipment the smith is expected to, and usually can, produce good results if proper care is taken. In hardening carbon tool steel in water, too much cannot be said in favor of slow, careful heating, nor against overheating if cracks are to be avoided. It is not wise to take the work from the hardening bath and leave it exposed to the air if there is any heat left in it, because it is more liable to crack than if left in the bath until cold. In heating, plenty of time is taken for the work to heat evenly clear through, thus avoiding strains caused by quick and improper heating, In quenching in water, contraction is much more rapid than was the expansion while heating, and strains begin the moment the work touches the water. If the piece has any considerable size and is taken from the bath before it is cold and allowed to come to the air, expansion starts again from the inside so rapidly that the chilled hardened surface cracks before the strains can be relieved. Many are most successful with the hardening bath about blood warm. When the work that is being hardened is nearly cold, it is taken from the water and instantly put into a can of oil, where it is allowed to finish cooling. The heat in the body of the tool will come to the surface more slowly, thus relieving the strain and overcoming much of the danger of cracking. Some contend that the temper should be drawn as soon as possible after hardening: but that if this cannot be done for some hours, the work should be left in the oil until the tempering can be done. It is claimed that forming dies and punch-press dies that are difficult to harden will seldom crack if treated in this way. Small tools or pieces that are very troublesome because of peculiar shape should be made of steel which has been thoroughly annealed. It is often well to mill or turn off the outer skin of the bar, to remove metal which has been cold-worked. Then heat slowly just through the critical range and cool in the furnace, in order to produce a very fine grain. Tools machined from such stock, and hardened with the utmost care, will have the best chance to survive without warping, growth or cracking. Next: Shrinking And Enlarging Work Previous: Hints For Tool Steel Users
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