| I come in different shapes and sizes. Part of me are curves, others are straight. You can put me anywhere you like, but there is only one right place for me. What am I? ... Read more of I come in different shapes and sizes. at Free Jokes.ca |  Informational.caPrivacy |
Steel MakingPlacing Of PyrometersWhen installing a pyrometer, care should be taken that it re... Knowing What Takes Place How are we to know if we have given a piece of steel the ver... Introduction Of Carbon The matter to which these notes are primarily directed is the... Tempering Round Dies A number of circular dies of carbon tool steel for use in too... Gears The material used for all gears on the Liberty engine was sel... Application Of Liberty Engine Materials To The Automotive Industry The success of the Liberty engine program was an engineer... Annealing There is no mystery or secret about the proper annealing of d... Silicon Silicon prevents, to a large extent, defects such as gas bubb... High-carbon Machinery Steel The carbon content of this steel is above 30 points and is ha... Composition Of Transmission-gear Steel If the nickel content of this steel is eliminated, and the pe... Protectors For Thermo-couples Thermo-couples must be protected from the danger of mechanica... Heating Of Manganese Steel Another form of heat-treating furnace is that which is used ... Air-hardening Steels These steels are recommended for boring, turning and planing... For Milling Cutters And Formed Tools FORGING.--Forge as before.--ANNEALING.--Place the steel in a ... Gas Consumption For Carburizing Although the advantages offered by the gas-fired furnace for ... Fatigue Tests It has been known for fifty years that a beam or rod would fa... Manganese Manganese adds considerably to the tensile strength of steel,... Impact Tests Impact tests are of considerable importance as an indication ... Carbon Steels For Different Tools All users of tool steels should carefully study the different... Cyanide Bath For Tool Steels All high-carbon tool steels are heated in a cyanide bath. Wi... |
The Quenching TankCategory: CASE-HARDENING OR SURFACE-CARBURIZING The quenching tank is an important feature of apparatus in case-hardening--possibly more so than in ordinary tempering. One reason for this is because of the large quantities of pieces usually dumped into the tank at a time. One cannot take time to separate the articles themselves from the case-hardening mixture, and the whole content of the box is droped into the bath in short order, as exposure to air of the heated work is fatal to results. Unless it is split up, it is likely to go to the bottom as a solid mass, in which case very few of the pieces are properly hardened. A combination cooling tank is shown in Fig. 38. Water inlet and outlet pipes are shown and also a drain plug that enables the tank to be emptied when it is desired to clean out the spent carburizing material from the bottom. A wire-bottomed tray, framed with angle iron, is arranged to slide into this tank from the top and rests upon angle irons screwed to the tank sides. Its function is to catch the pieces and prevent them from settling to the tank bottom, and it also makes it easy to remove a batch of work. A bottomless box of sheet steel is shown at C. This fits into the wire-bottomed tray and has a number of rods or wires running across it, their purpose being to break up the mass of material as it comes from the carbonizing box. Below the wire-bottomed tray is a perforated cross-pipe that is connected with a compressed-air line. This is used when case-hardening for colors. The shop that has no air compressor may rig up a satisfactory equivalent in the shape of a low-pressure hand-operated air pump and a receiver tank, for it is not necessary to use high-pressure air for this purpose. When colors are desired on case-hardened work, the treatment in quenching is exactly the same as that previously described except that air is pumped through this pipe and keeps the water agitated. The addition of a slight amount of powdered cyanide of potassium to the packing material used for carburizing will produce stronger colors, and where this is the sole object, it is best to maintain the box at a dull-red heat. is necessary.] The old way of case-hardening was to dump the contents of the box at the end of the carburizing heat. Later study in the structure of steel thus treated has caused a change in this procedure, the use of automobiles and alloy steels probably hastening this result. The diagrams reproduced in Fig. 39 show why the heat treatment of case-hardened work is necessary. Starting at A with a close-grained and tough stock, such as ordinary machinery steel containing from 15 to 20 points of carbon, if such work is quenched on a carbonizing heat the result will be as shown at B. This gives a core that is coarse-grained and brittle and an outer case that is fine-grained and hard, but is likely to flake off, owing to the great difference in structure between it and the core. Reheating this work beyond the critical temperature of the core refines this core, closes the grain and makes it tough, but leaves the case very brittle; in fact, more so than it was before. Next: Refining The Grain Previous: Quenching The Work
Viewed 693 |
||||||||||||||||||||
