Preventing Cracks In Hardening
: HARDENING CARBON STEEL FOR TOOLS: The Working Of Steel
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, and usually can,
produce good results if proper care is taken.
In hardening carbon tool steel in water, too much cannot be said in
favor of slow, careful heati
are to be avoided.
It is not wise to take the work from the hardening bath and leave
it exposed to the air if there is any heat left in it, because
it is more liable to crack than if left in the bath until cold.
In heating, plenty of time is taken for the work to heat evenly
clear through, thus avoiding strains caused by quick and improper
heating, In quenching in water, contraction is much more rapid
than was the expansion while heating, and strains begin the moment
the work touches the water. If the piece has any considerable size
and is taken from the bath before it is cold and allowed to come to
the air, expansion starts again from the inside so rapidly that the
chilled hardened surface cracks before the strains can be relieved.
Many are most successful with the hardening bath about blood warm.
When the work that is being hardened is nearly cold, it is taken
from the water and instantly put into a can of oil, where it is
allowed to finish cooling. The heat in the body of the tool will
come to the surface more slowly, thus relieving the strain and
overcoming much of the danger of cracking.
Some contend that the temper should be drawn as soon as possible
after hardening: but that if this cannot be done for some hours, the
work should be left in the oil until the tempering can be done. It
is claimed that forming dies and punch-press dies that are difficult
to harden will seldom crack if treated in this way.
Small tools or pieces that are very troublesome because of peculiar
shape should be made of steel which has been thoroughly annealed.
It is often well to mill or turn off the outer skin of the bar,
to remove metal which has been cold-worked. Then heat slowly just
through the critical range and cool in the furnace, in order to
produce a very fine grain. Tools machined from such stock, and
hardened with the utmost care, will have the best chance to survive
without warping, growth or cracking.
More
-
High Speed Steel
For centuries the secret art of making tool steel was handed down from father to son. The manufacture of tool steel is still an art which, by the aid of science, has lost much of its secrecy; yet tool steel is today made by practical men skilled as ... High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is hardly ever above 60 points or 0.60 per cent. Annealing such steel is generally in quantity production and does not require the care that the other steels need because it is very largely a m... High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing from 11 to 14 per cent chromium, was originally developed for cutlery purposes, but has in the past few years been used to a considerable extent for exhaust valves in airplane engines becau... Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of the connecting-rod bolt, the main-bearing bolt, the propeller-hub key, etc. The material used for parts of this type was selected at the option of the manufacturer from standard S. A. E. s... Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to the best steel to use for a given purpose, mentioning in as much detail as possible the use for which it is intended. Do not heat the steel to a higher degree than that fixed in the desc... Impact Tests
Impact tests are of considerable importance as an indication of how a metal will perform under shock. Some engineers think that the tensile test, which is one made under slow loading, should therefore be supplemented by another showing what will hap... Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed steels by various makers, it is always advisable to follow the directions of each when using his brand of steel. In the absence of specific directions the following general suggestions fr... Introduction Of Carbon
The matter to which these notes are primarily directed is the introduction of carbon into the case of the article to be hardened. In the first place the chances of success are increased by selecting as few brands of steel as practicable to cover the... Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to have accurate knowledge as to the heat being used in either forging or hardening steels, a color chart will be of considerable assistance if carefully studied. These have been prepared by sev... Knowing What Takes Place
How are we to know if we have given a piece of steel the very best possible treatment? The best method is by microscopic examination of polished and etched sections, but this requires a certain expense for laboratory equipment and upkeep, which m... Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is particularly desirable in the winter, then heat slowly and carefully to a scaling heat, that is a lemon heat (1,800 to 2,000 deg.F.), and forge uniformly. Reheat the tool for further forging di... Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is particularly desirable in the winter. Then heat slowly and carefully to a scaling heat, that is a lemon heat (1,800 deg.-2,000 deg.F.), and forge uniformly. Reheat the tool for further forging ... Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring temperature are sketched in Fig. 123. The instrument is light and portable, and can be sighted as easily as an opera glass. The telescope, which is held in the hand, weighs only 25 oz.;... Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecting rods are so severe that the methods of securing the desired qualities will be of value in other lines. The original specifications called for chrome-nickel but the losses due to the dif... Machineability
Reheating for machine ability was done at 100 deg. less than the drawing temperature, but the time of soaking is more than double. After both drawing and reheating, the blanks were buried in lime where they remain, out of contact with the air, until... Making Steel Balls
Steel balls are made from rods or coils according to size, stock less than 9/16-in. comes in coils. Stock 5/8-in. and larger comes in rods. Ball stock is designated in thousandths so that 5/8-in. rods are known as 0.625-in. stock. Steel for makin... Manganese
MANGANESE is a metal much like iron. Its chemical symbol is Mn. It is somewhat more active than iron in many chemical changes--notably it has what is apparently a stronger attraction for oxygen and sulphur than has iron. Therefore the metal is used ... Manganese
Manganese adds considerably to the tensile strength of steel, but this is dependent on the carbon content. High carbon materially adds to the brittleness, whereas low-carbon, pearlitic-manganese steels are very tough and ductile and are not at all b... Molybdenum
Molybdenum steels have been made commercially for twenty-five years, but they have not been widely exploited until since the war. Very large resources of molybdenum have been developed in America, and the mining companies who are equipped to produce... Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perhaps, only an assumption; but that he was badly treated by Ebbw Vale is subject to no doubt. Mushet's business capacity was small but it is difficult to believe that he could have been so f... Nickel
Nickel may be considered as the toughest among the non-rare alloys now used in steel manufacture. Originally nickel was added to give increased strength and toughness over that obtained with the ordinary rolled structural steel and little attempt wa... Nickel-chromium
A combination of the characteristics of nickel and the characteristics of chromium, as described, should obviously give a very excellent steel as the nickel particularly affects the ferrite of the steel and the chromium the carbon. From this combina... Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contraction in hardening and are very desirable for test plugs, gages, punches and dies, for milling cutters, taps, reamers, hard steel bushings and similar work. It is recommended that for for... Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thoroughly. Do not under any circumstances attempt to harden at the forging heat. After cooling from forging reheat to about 1,450 deg.F. and cool slowly so as to remove forging strains. ... Open Hearth Process
The open hearth furnace consists of a big brick room with a low arched roof. It is charged with pig iron and scrap through doors in the side walls. Through openings at one end of the furnace come hot air and gas, which burn in the furnace, prod... Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is largely used. This is a comparative method. By means of the rheostat the current through the lamp is adjusted until the brightness of the filament is just equal to the brightness of the image ... Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal from the ore. It remains in the steel when made by the so-called acid process, but it can be easily eliminated down to 0.06 per cent in the basic process. In fact the discovery of the basic ... Phosphorus
Phosphorus is one of the impurities in steel, and it has been the object of steel makers for years to eliminate it. On cheap grades of steel, not subject to any abnormal strain or stress, 0.1 per cent phosphorus is not objectionable. High phosphorus... Pickling The Forgings
The forgings were then pickled in a hot solution of either niter cake or sulphuric acid and water at a temperature of 170 deg.F., and using a solution of about 25 per cent. The solution was maintained at a constant point by taking hydrometer reading... 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...