Testing And Inspection Of Heat Treatment
: HEAT TREATMENT OF STEEL: The Working Of Steel
The hard parts of the
gear must be so hard that a new mill file does not bite in the
least. Having passed this file test at several points, the gears go
to the center-punch test. The inspector is equipped with a wooden
trough secured to the top of the bench to support the gear, a number
of center punches (made of 3/4-in. hex-steel having points sharpened
to an angle of 120 deg.) and a hammer weighing about 4 oz. With
these simple tools, supplemented by his skill, the inspector can
feel the depth and quality of the case and the condition of the
core. The gears are each tested in this way at several points on
the teeth and elsewhere, the scrap gear being also subjected to
the test. Finally, the scrap gear is securely clamped in the
straightening press shown in Fig. 57. With a 3-1/2-lb. hammer and
a suitable hollow-ended drift manipulated by one of Sandow's
understudies, teeth are broken out of the scrap gear at various
points. These give a record confirming the center-punch tests,
which, if the angle of the center punch is kept at 120 deg. and
the weight of the hammer and blow are uniform, is very accurate.
After passing the center-punch test the ends of the teeth are peened
lightly with a hammer. If they are too hard, small particles fly
off. Such gears are drawn in oil at a temperature of from 300 to
350 deg.F., depending on their hardness. Some builders prefer to have
the extreme outer ends of the teeth drawn somewhat lower than the
rest. This drawing is done on gas-heated red-hot plates, as shown
at A in Fig. 58.
Nickel steel, in addition to all the tests given to carbon steel,
is subjected to a Brinell test. For each steel, the temperature
and the period of treatment are specific. For some unknown reason,
apparently like material with like treatment will, in isolated
cases, not produce like results. It then remains for the treatment
to be repeated or modified, but the results obtained during inspection
form a valuable aid to the metallurgist in determining further
treatment.
More
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Quality And Structure
The quality of high-speed steel is dependent to a very great extent upon its structure. The making of the structure begins under the hammer, and the beneficial effects produced in this stage persist through the subsequent operations, provided they a... Quenching
It is considered good practice to quench alloy steels from the pot, especially if the case is of any appreciable depth. The texture of carbon steel will be weakened by the prolonged high heat of carburizing, so that if we need a tough core, we must ... Quenching The Work
In some operations case-hardened work is quenched from the box by dumping the whole contents into the quenching tank. It is common practice to leave a sieve or wire basket to catch the work, allowing the carburizing material to fall to the bottom of... Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel is as important as its heating. Quenching baths vary in nature, there being a large number of ways to cool a piece of steel in contrast to the comparatively few ways of heating it. Plai... Rate Of Absorption
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 absorpt... Rate Of Cooling
At the option of the manufacturer, the above treatment of gear forgings could be substituted by normalizing the forgings at a temperature of from 1,550 to 1,600 deg.F. The most important criterion for proper normalizing, consisted in allowing the fo... Refining The Grain
This is remedied by reheating the piece to a temperature slightly above the critical temperature of the case, this temperature corresponding ordinarily to that of steel having a carbon content of 85 points, When this is again quenched, the temperatu... Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown graphically in Fig. 65 to the series of illustrations on pages 137 to 144. This was prepared by Thos. Firth & Sons, Ltd., Sheffield, England. The center piece Fig. 65 represents a block ... Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of Dean, Gloucestershire, of a Scots father (David, 1772-1847) himself a noted contributor to the metallurgy of iron and steel, is, like the American William Kelly, considered by many to have ... S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat treatments to suit different steels and varying conditions. These have already been referred to on pages 39 to 41 in connection with the different steels used in automobile practice. Thes... Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a cast-iron screen which forms a table or apron for the furnace. Directly beneath this table is located one of the steel conveyor carts, shown in Fig. 43, which is provided with two wheels at ... Short Method Of Treatment
In the new method, the packed pots are run into the case-hardening furnaces, which are heated to 1,600 deg.F. On the insertion of the cold pots, the temperature naturally falls. The amount of this fall is dependent upon a number of variables, but i... Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling. Pins for forced fits can be enlarged several thousandths of an inch by rapid heating to a dull red and quenching in water. The theory is that the metal is expanded in heating and that th... Silicon
SILICON is a very widespread element (symbol Si), being an essential constituent of nearly all the rocks of the earth. It is similar to carbon in many of its chemical properties; for instance it burns very readily in oxygen, and consequently native ... Silicon
Silicon prevents, to a large extent, defects such as gas bubbles or blow holes forming while steel is solidifying. In fact, steel after it has been melted and before it has been refined, is wild and gassy. That is to say, if it would be cast into mo... Standard Analysis
The selection of a standard analysis by the manufacturer is the result of a series of compromises between various properties imparted to the steel by the addition of different elements and there is a wide range of chemical analyses of various brands... Steel Before The 1850's
In spite of a rapid increase in the use of machines and the overwhelming demand for iron products for the expanding railroads, the use of steel had expanded little prior to 1855. The methods of production were still largely those of a century earlie... Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of cold-rolled steel. Heat treatment of cold-worked steel is a very delicate operation. Cold working hardens and strengthens steel. It also introduces internal stresses. Heat-treatments are d... Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be recommended for tools which have to withstand shocks, such as for cold chisels or punches. These steels are, however, particularly useful where it is necessary to cut tempered or heat-treate... Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the austenitic state. (See page 108.) It is then soft and ductile. As the steel is heated above the critical temperature the size of the austenite crystals tends to grow rapidly. When forging... Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are given by a maker whose steel is probably typical of a number of different makes, so that they will be found useful in other cases as well. These include hints as to forging as well as hard... Sulphur
SULPHUR is another element (symbol S) which is always found in steel in small quantities. Some sulphur is contained in the ore from which the iron is smelted; more sulphur is introduced by the coke and fuel used. Sulphur is very difficult to get rid... Sulphur
Sulphur is another impurity and high sulphur is even a greater detriment to steel than phosphorus. High sulphur up to 0.09 per cent helps machining properties, but has a tendency to make the steel hot short, i.e., subject to opening up cracks and se... Surface Carburizing
Carburizing, commonly called case-hardening, is the art of producing a high-carbon surface, or case, upon a low carbon steel article. Wrenches, locomotive link motions, gun mechanisms, balls and ball races, automobile gears and many other devices ar... Take Time For Hardening
Uneven heating and poor quenching has caused loss of many very valuable dies, and it certainly seems that when a firm spends from $75 to $450 in cutting a die that a few hours could be spared for proper hardening. But the usual feeling is that a to... Temperature For Annealing
Theoretically, annealing should be accomplished at a temperature at just slightly above the critical point. However, in practice the temperature is raised to a higher point in order to allow for the solution of the carbon and iron to be produced mo... Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading and recording of all temperatures are in the hands of one man, who occupies a room with an opening into the end of the hardening department. The opening is about 15 ft. above the floor level... Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (212 deg.F.) the transformation begins, increasing in intensity as the temperature is raised, until finally when the lower critical range is reached, the steel has been all changed into the ... Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by the various colors, or oxides, which appear on steel in tempering. The figures shown are from five different sources and while the variations are not great, it is safer to take the averag... Tempering Round Dies
A number of circular dies of carbon tool steel for use in tool holders of turret lathes were required. No proper tempering oven was available, so the following method was adopted and proved quite successful. After the dies had been hardened dead ... Tensile Properties
Strength of a metal is usually expressed in the number of pounds a 1-in. bar will support just before breaking, a term called the ultimate strength. It has been found that the shape of the test bar and its method of loading has some effect upon the ... Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill file does not bite in the least. Having passed this file test at several points, the gears go to the center-punch test. The inspector is equipped with a wooden trough secured to the top of ... The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-treatment department, there is none that offers greater possibilities for profitable returns than the systematic cleaning, blending and reworking of artificial carburizers, or compounds. ... The Effect
The heating at 1,600 deg.F. gives the first heat treatment which refines the core, which under the former high heat (1,700 deg.F.) was rendered coarsely crystalline. All the gears, including the scrap gears, are quenched direct from the pot in this ... The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and Electric Furnaces, Ltd., 6, Queenstreet, London, S. W.: Two gages of 3/4 in. diameter, 12 threads per inch, were heated in a Wild-Barfield furnace, using the pyroscopic detector, and we... The Electric Process
The fourth method of manufacturing steel is by the electric furnace. These furnaces are of various sizes and designs; their size may be sufficient for only 100 lb. of metal--on the other hand electric furnaces for making armor-plate steel will hold ... The Forging Of Steel
So much depends upon the forging of steel that this operation must be carefully supervised. This is especially true because of the tendency to place unskilled and ignorant men as furnace-tenders and hammer men. The main points to be supervised are t... The Influence Of Size
The size of the piece influences the physical properties obtained in steel by heat treatment. This has been worked out by E. J. Janitzky, metallurgical engineer of the Illinois Steel Company, as follows: With an increase in the mass of steel th... The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and substantial in that it is not affected by the jar and vibration of the factory or the forge shop. Large or small couples, long or short leads can be used without adjustment. The recording instr... The Modern Hardening Room
A hardening room of today means a very different place from the dirty, dark smithshop in the corner with the open coal forge. There, when we wanted to be somewhat particular, we sometimes shoveled the coal cinders to one side and piled a great pile... The Packing Department
In Fig. 56 is shown the packing pots where the work is packed. These are of malleable cast iron, with an internal vertical flange around the hole A. This fits in a bell on the end of the cast-iron pipe B, which is luted in position with fireclay be... The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufacture of automobile and other parts which are likely to be subjected to rough usage. The strength and ability to withstand hard knocks depend to a very considerable degree on the thoroughn... The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely necessary that a measuring instrument be used which will give the operator an exact reading of heat in furnace. There are a number of instruments and devices manufactured for this purpose but ... The Quenching Tank
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 ... The Theory Of Tempering
Steel that has been hardened is generally harder and more brittle than is necessary, and in order to bring it to the condition that meets our requirements a treatment called tempering is used. This increases the toughness of the steel, i.e., decrea... The Thermo-couple
With the application of the thermo-couple, the measurement of temperatures, between, say, 700 and 2,500 deg.F., was made more simple and precise. The theory of the thermo-couple is simple; it is that if two bars, rods, or wires of different metals a... Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or by being packed. Packing is by far the most satisfactory method as it prevents scaling, local hard spots, uneven annealing, or violent changes in shape. It should be brought up slowly to ju... Tungsten
Tungsten, as an alloy in steel, has been known and used for a long time. The celebrated and ancient damascus steel being a form of tungsten-alloy steel. Tungsten and its effects, however, did not become generally realized until Robert Mushet experim... Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herewith. Figure 92 is a lead pot furnace, Fig. 93 is a vertical furnace with a center column. This column reduces the cubical contents to be heated and also supports the cover. A small too... Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pressing and drop forgings. Mining drills to harden only. Easily weldable. SMITHS' TOOL TEMPER.--No. 3-1/2: Large punches, minting and rivet dies, nailmakers' tools, hammers, hot and cold se... Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the facilities available in the locality where the shop is situated and the nature and quantity of the work to be done. The furnaces can be heated with producer gas in most cases, but when space... Vanadium
Vanadium has a very marked effect upon alloy steels rich in chromium, carbon, or manganese. Vanadium itself, when combined with steel very low in carbon, is not so noticeably beneficial as in the same carbon steel higher in manganese, but if a small... William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association was published in the Scientific American on September 13, 1856.[95] On September 16, 1856, Martien filed application for a U.S. patent on his furnace and Mushet for one on the application o...