| Dora Franks, Ex-Slave, Monroe County FEC Mrs. Richard Kolb Rewrite, Pauline Loveless Edited, Clara E. Stokes DORA FRANKS Aberdeen, Mississippi Dora Franks, ex-slave, lives at Aberdeen, Monroe County. She is about five feet tall and w... Read more of Dora Franks at Martin Luther King.ca |  Informational.caPrivacy |
Steel MakingPhosphorusPHOSPHORUS is an element (symbol P) which enters the metal fr... Steel Worked In Austenitic State As a general rule steel should be worked when it is in the a... Non-shrinking Oil-hardening Steels Certain steels have a very low rate of expansion and contract... Composition Of Transmission-gear Steel If the nickel content of this steel is eliminated, and the pe... High-carbon Machinery Steel The carbon content of this steel is above 30 points and is ha... Forging High-speed Steel Heat very slowly and carefully to from 1,800 to 2,000 deg.F.... Suggestions For Handling High-speed Steels The following suggestions for handling high-speed steels are ... Liberty Motor Connecting Rods The requirements for materials for the Liberty motor connecti... Quality And Structure The quality of high-speed steel is dependent to a very great ... Hardening Operation Hardening a gear is accomplished as follows: The gear is tak... Hardening Steel is hardened by quenching from above the upper critical.... The Electric Process The fourth method of manufacturing steel is by the electric f... Phosphorus Phosphorus is one of the impurities in steel, and it has been... Properties Of Steel Steels are known by certain tests. Early tests were more or l... Annealing Work With the exception of several of the higher types of alloy s... Conclusions Martien was probably never a serious contender for the honor ... Heating Of Manganese Steel Another form of heat-treating furnace is that which is used ... Oil-hardening Steel Heat slowly and uniformly to 1,450 deg.F. and forge thorough... Heat Treatment Of Punches And Dies Shears Taps Etc HEATING.--The degree to which tools of the above classes shou... The Care Of Carburizing Compounds Of all the opportunities for practicing economy in the heat-t... |
Rate Of AbsorptionCategory: CASE-HARDENING OR SURFACE-CARBURIZING According to Guillet, the absorption of carbon is favored by those special elements which exist as double carbides in steel. For example, manganese exists as manganese carbide in combination with the iron carbide. The elements that favor the absorption of carbon are: manganese, tungsten, chromium and molybdenum those opposing it, nickel, silicon, and aluminum. Guillet has worked out the effect of the different elements on the rate of penetration in comparison with steel that absorbed carbon at a given temperature, at an average rate of 0.035 in. per hour. His tables show that the following elements require an increased time of exposure to the carburizing material in order to obtain the same depth of penetration as with simple steel: When steel contains Increased time of exposure 2.0 per cent nickel 28 per cent 7.0 per cent nickel 30 per cent 1.0 per cent titanium 12 per cent 2.0 per cent titanium 28 per cent 0.5 per cent silicon 50 per cent 1.0 per cent silicon 80 per cent 2.0 per cent silicon 122 per cent 5.0 per cent silicon No penetration 1.0 per cent aluminum 122 per cent 2.0 per cent aluminum 350 per cent The following elements seem to assist the rate of penetration of carbon, and the carburizing time may therefore be reduced as follows: When steel contains Decreased time of exposure 0.5 per cent manganese 18 per cent 1.0 per cent manganese 25 per cent 1.0 per cent chromium 10 per cent 2.0 per cent chromium 18 per cent 0.5 per cent tungsten 0 1.0 per cent tungsten 0 2.0 per cent tungsten 25 per cent 1.0 per cent molybdenum 0 2.0 per cent molybdenum 18 per cent The temperature at which carburization is accomplished is a very important factor. Hence the necessity for a reliable pyrometer, located so as to give the temperature just below the tops of the pots. It must be remembered, however, that the pyrometer gives the temperature of only one spot, and is therefore only an aid to the operator, who must use his eyes for successful results. The carbon content of the case generally is governed by the temperature of the carburization. It generally proves advisable to have the case contain between 0.90 per cent and 1.10 carbon; more carbon than this gives rise to excess free cementite or carbide of iron, which is detrimental, causing the case to be brittle and apt to chip. T. G. Selleck gives a very useful table of temperatures and the relative carbon contents of the case of steels carburized between 4 and 6 hrs. using a good charcoal carburizer. This data is as follows: TABLE 15.--CARBON CONTENT OBTAINED AT VARIOUS TEMPERATURES At 1,500 deg.F., the surface carbon content will be 0.90 per cent At 1,600 deg.F., the surface carbon content will be 1.00 per cent At 1,650 deg.F., the surface carbon content will be 1.10 per cent At 1,700 deg.F., the surface carbon content will be 1.25 per cent At 1,750 deg.F., the surface carbon content will be 1.40 per cent At 1,800 deg.F., the surface carbon content will be 1.75 per cent To this very valuable table, it seems best to add the following data, which we have used for a number of years. We do not know the name of its author, but it has proved very valuable, and seems to complete the above information. The table is self-explanatory, giving depth of penetration of the carbon of the case at different temperatures for different lengths of time: --------------------------------------------------------- Temperature Penetration ----------------------------- 1,550 1,650 1,800 ------------------------------------------------------ Penetration after 1/2 hr. 0.008 0.012 0.030 Penetration after 1 hr. 0.018 0.026 0.045 Penetration after 2 hr. 0.035 0.048 0.060 Penetration after 3 hr. 0.045 0.055 0.075 Penetration after 4 hr. 0.052 0.061 0.092 Penetration after 6 hr. 0.056 0.075 0.110 Penetration after 8 hr. 0.062 0.083 0.130 --------------------------------------------------------- From the tables given, we may calculate with a fair degree of certainty the amount of carbon in the case, and its penetration. These figures vary widely with different carburizers, and as pointed out immediately above, with different alloy steels. Next: Carburizing Material Previous: Surface Carburizing
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