| I It was never quite clear to me how Jim Shorthouse managed to get his private secretaryship; but, once he got it, he kept it, and for some years he led a steady life and put money in the savings bank. One morning his employer sent for him into the... Read more of The Strange Adventures Of A Private Secretary In New York at Scary Stories.ca |  Informational.caPrivacy |
Steel MakingSteel Worked In Austenitic StateAs a general rule steel should be worked when it is in the a... Protective Screens For Furnaces Workmen needlessly exposed to the flames, heat and glare from... Silicon SILICON is a very widespread element (symbol Si), being an es... Ebbw Vale And The Bessemer Process After his British Association address in August 1856, Besseme... Chrome-nickel Steel Forging heat of chrome-nickel steel depends very largely on ... Application To The Automotive Industry The information given on the various parts of the Liberty eng... Detrimental Elements Sulphur and phosphorus are two elements known to be detrimen... Manganese Manganese adds considerably to the tensile strength of steel,... Case-hardening Treatments For Various Steels Plain water, salt water and linseed oil are the three most co... Annealing Alloy Steel The term alloy steel, from the steel maker's point of view, r... Sulphur Sulphur is another impurity and high sulphur is even a greate... Effects Of Proper Annealing Proper annealing of low-carbon steels causes a complete solu... High-chromium Or Rust-proof Steel High-chromium, or what is called stainless steel containing f... Carbon-steel Forgings Low-stressed, carbon-steel forgings include such parts as car... Hints For Tool Steel Users Do not hesitate to ask for information from the maker as to t... Pyrometry And Pyrometers A knowledge of the fundamental principles of pyrometry, or th... The Modern Hardening Room A hardening room of today means a very different place from ... Hardening The forgings can be hardened by cooling in still air or quen... Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer For extremely high temperature, the optical pyrometer is lar... Testing And Inspection Of Heat Treatment The hard parts of the gear must be so hard that a new mill f... |
Care In AnnealingCategory: HEAT TREATMENT OF STEEL Not only will benefits in machining be found by careful annealing of forgings but the subsequent troubles in the hardening plant will be greatly reduced. The advantages in the hardening start with the carburizing operation, as a steel of uniform and fine grain size will carburize more uniformly, producing a more even hardness and less chances for soft spots. The holes in the gears will also close in more uniformly, not causing some gears to require excessive grinding and others with just enough stock. Also all strains will have been removed from the forging, eliminating to a great extent distortion and the noisy gears which are the result. With the steels used, for the heat-treated gears, always of a higher carbon content, treatment after forging is necessary for machining, as it would be impossible to get the required production from untreated forgings, especially in the alloy steels. The treatment is more delicate, due to the higher percentage of carbon and the natural increase in cementite together with complex carbides which are present in some of the higher types of alloys. Where poor machining conditions in heat-treated steels are present they are generally due to incomplete solution of cementite rather than bands of free ferrite, as in the case of case-hardening steels. This segregation of carbon, as it is sometimes referred to, causes hard spots which, in the forming of the tooth, cause the cutter to ride over the hard metal, producing high spots on the face of the tooth, which are as detrimental to satisfactory gear cutting as the drops or low spots produced on the face of the teeth when the pearlite is coarse-grained or in a banded condition. In the simpler carburized steels it is not necessary to test the forgings for hardness after annealing, but with the high percentages of alloys in the carburizing steels and the heat-treated steels a hardness test is essential. To obtain the best results in machining, the microstructure of the metal should be determined and a hardness range set that covers the variations in structure that produce good machining results. By careful control of the heat-treating operation and with the aid of the Brinell hardness tester and the microscope it is possible to continually give forgings that will machine uniformly and be soft enough to give desired production. The following gives a few of the hardness numerals on steel used in gear manufacture that produce good machining qualities: 0.20 per cent carbon, 3 per cent nickel, 1-1/4; per cent chromium--Brinell 156 to 170. 0.50 per cent carbon, 3 per cent nickel, 1 per cent chromium--Brinell 179 to 187. 0.50 per cent carbon chrome-vanadium--Brinell 170 to 179. Next: The Influence Of Size Previous: Temperature For Annealing
Viewed 641 |
||||||||||||||||||||
