Short Method Of Treatment
: HEAT TREATMENT OF STEEL: The Working Of Steel
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 it averages nearly 500 deg.F. as shown in the pyrometer chart,
Fig. 61. The work and furnace must be brought to 1,600 deg.F. Within
2-1/2 hr.; otherwise, a longer time will be
the desired depth of case. On this work, the depth of case required
is designated in thousandths, and on crown gears, the depth in
0.028 in. Having brought the work to a temperature of 1,600 deg.F.
the depth of case mentioned can be obtained in about 5-1/2 hr. by
maintaining this temperature.
As stated before, at the top of each pot are several test pieces
consisting of a whole scrap gear and several sections. After the
pots have been heated at 1,600 deg.F. for about 5-1/4 hr., they are
removed, and a scrap-section test-piece is quenched direct from
the pot in mineral oil at not more than 100 deg.F. The end of a tooth
of this is then ground and etched to ascertain the depth of case.
As these test pieces are of exactly the same cross-section as the
gears themselves, the carburizing action is similar. When the depth
of case has been found from the etched test pieces to be satisfactory,
the pots are removed. The iron ball then is dropped into the tube
to seal the hole in the bottom of the pot; the cover and the tube
are removed, and the gears quenched direct from the pot in mineral
oil, which is kept at a temperature not higher than 100 deg.F.
More
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Piston Pin
The piston pin on an aviation engine must possess maximum resistance to wear and to fatigue. For this reason, the piston pin is considered, from a metallurgical standpoint, the most important part on the engine to produce in quantities and still pos... Placing Of Pyrometers
When installing a pyrometer, care should be taken that it reaches directly to the point desired to be measured, that the cold junction is kept cold, and that the wires leading to the recording instrument are kept in good shape. The length of these ... Placing The Thermo-couples
The following illustrations from the Taylor Instrument Company show different applications of the thermo-couples to furnaces of various kinds. Figure 118 shows an oil-fired furnace with a simple vertical installation. Figure 119 shows a method of im... Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-treating them to meet the specifications demanded by some of the foreign governments led Wheelock, Lovejoy & Company to establish a complete plant for this purpose in connection with their wa... Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, Dayton, Ohio, they have a large quantity of small shafts, Fig. 40, that are to be case-hardened at A while the ends B and C are to be left soft. Formerly, the part A was brush-coated with ... Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thickness of 0.0005 in. Less than this does not give a continuous coating. The plating bath used has a temperature of 170 deg.F. A voltage of 4.1 is to be maintained across the terminals. Regio... Preventing Cracks In Hardening
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, ... Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such tools as taps and form cutters, which must keep their shape after hardening and which cannot be ground away on the profile. For this reason it is well to put taps, reamers and the like in... Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-carbon steel. This produces what might be termed a dual steel, allowing for an outer shell which when hardened would withstand wear, and a soft ductile core to produce ductility and withst... Properties Of Alloy Steels
The following table shows the percentages of carbon, manganese, nickel, chromium and vanadium in typical steel alloys for engineering purposes. It also gives the elastic limit, tensile strength, elongation and reduction of area of the various alloys... Properties Of Steel
Steels are known by certain tests. Early tests were more or less crude, and depended upon the ability of the workman to judge the grain exhibited by a freshly broken piece of steel. The cold-bend test was also very useful--a small bar was bent flat ... Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from furnaces where high temperatures are maintained suffer in health as well as in bodily discomfort. This shows several types of shields designed for the maximum protection of the furnace wo... Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanical injury. For this purpose tubes of various refractory materials are made to act as protectors. These in turn are usually protected by outside metal tubes. Pure wrought iron is largely use... Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' water pyrometer because they can place a number of the balls or weights on the plate in locations where it is difficult to use other pyrometers. One of these pyrometers is shown in section... Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermocouples as in Fig. 132. Usually the pyrometer is portable, as shown in this case, which is a Brown. Other methods of mounting for this kind of work arc shown in Figs. 133 and 134. The bent ... Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or the measurement of temperatures, is quite necessary for one engaged in the heat treatment of steel. It is only by careful measurement and control of the heating of steel that the full benefi... 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...