High-speed steel

“ Modern high-speed steels which are every day being made have such high quality that tools formed from them will stand up for hours working red-hot under a lathe speed of two or three hundred linear feet per minute taking a deep cut and “plowing out” chips faster than a laborer can carry them away. ”

“ When taking heavy cuts a tool of to-day may exert as much as ten tons’ pressure against the metal it is cutting and the advent of this wonderful material for tools necessitated the building of immensely heavier and stronger lathes and other machines, which, alone, were capable of giving them power to do their work. The high-speed steels, therefore, have revolutionized metal-cutting practice and shop methods and have very largely aided efficiency. ”

“ A considerable amount of doubt has been thrown from time to time on the inability to take finishing cuts with high-speed steel, and in the early stages of its development this contention was to a large extent justified, but experience and practice have brought the steel into line and rendered it possible to obtain an excellent finish at high speeds with tools suitably formed and properly arranged in the machines. ”

“ But with high-speed steel that limit is much higher, for it can get almost red-hot before it loses its hardness and consequently machines can be run and jobs [Pg 106] finished at a speed which would have been out of the question only a few years ago. If one belligerent knew how to make high-speed steel while the other did not the former would have an enormous advantage in war-time. ”

“ It is sometimes contended that on the whole not much advantage or economy results from using high-speed steel, but it is easy to prove very greatly to the contrary, and the author proposes to give some figures and facts as to its use and advantage, not only by knowledge gained from results of his own firm, but also from information supplied by many important engineering establishments as to their present workshop practice, and for which he is indebted. ”

“ The speeds given in this table represent results obtained with tools made of a good grade of high-speed steel properly heat-treated and correctly ground. It will be noted that the cutting speed is much slower for cast iron than for steel. Cast iron is cut with less pressure or resistance than soft steel, but the slower speed required for cast iron is probably due to the fact that the pressure of the chip is concentrated closer to the cutting edge, combined with the fact that cast iron wears the tool faster than steel. ”

“ Perhaps one of the most unlooked-for developments in the use of high-speed steel has been the manufacture from it of twist drills, and it would be safe to say that in no other sphere has the new steel justified itself to a greater extent than in the operations of drilling and boring, as its powers in that respect have revolutionized completely modern workshop practice. ”

“ They were tempered by heating to a dark red and left to cool in the air. The high speed steels of today are heated to 2,000° or 2,200° Fahr., or a white heat bordering on a welding heat.
The chemical composition of these new steels are only known by their makers. However, it is said that they contain carbon, tungsten, chromium, manganese and other elements.
The great advantage in using high speed steel, is that a machine can be run three times as fast as one [81] using carbon steel, without destroying the edge of the tool. ”

“ Professor Greer, lecturing again at the Birmingham Town Hall last night, stated that the firm of Edwards and Sutton, of the Meersbrook Works, Sheffield, of which Sir Mark Edwards is the head, have, after his lengthened experiments, placed on the market a steel with from three to seven times the cutting power of existing high-speed steel, and which, in contradistinction to present material, can be hardened in water, oil, or blast. ”

“ 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 are properly carried out. The massive carbides and tungstides present in the ingot are broken down and uniformly distributed throughout the billet. ”

“ Fortunately, the treatment of the rapid steel produced by the author’s firm is of the simplest; simpler, in fact, than ordinary carbon steels or the old self-hardening steels, as great care had to be exercised in the heating of the latter steels, for if either were heated above a blood-red heat, say 1,600 deg. F., the danger of impairing their efficiency by burning was considerable; whereas with the high-speed steel, heating may be carried to a much higher temperature, even up to melting point, it being practically impossible to injure it by burning. ”

“ Of recent years a special quality of steel for tools called "high-speed" steel has been produced, mainly by the addition to ordinary cast steel of a small percentage of tungsten. The advantage of this is that, within certain limits, this does not soften with heat, and it is, I can assure you, a great invention in war-time, when a nation is straining every nerve to turn out guns and shells as fast as possible. ”

“ It was for some time not thought possible to plane at such high speeds on account of the tools coming into contact suddenly with the job and running risks of snapping off through shock, but where high-speed steel of proper quality is used this difficulty is overcome, and a good example or two of rapid planing may be quoted. Using a 7-ft. planing machine with two tools operating on forged steel of medium quality, the cutting speed, depth of cut and feed of each tool is respectively 54 ft., one-fourth inch, and one eighth inch, the speed of reverse being 160 ft. ”

“ Page 179 It is sometimes advantageous to dip tools, before heating for hardening, in ordinary fuel or quenching oil. The oil leaves a thin film of carbon which tends to prevent decarbonization, giving a very hard surface.
For other makes of high-speed steel used in lathe and planer tools the makers recommend that the tools be cut from the bar with a hack saw or else heated and cut with a chisel. The heating should be very slow until the steel reaches a red after which it can be heated more rapidly and should only be forged at a high heat. ”

“ The author hopes that the few facts he has given as to the use and development of high-speed steel may indicate some of its uses and progress, but he can scarcely refrain from remarking that many are saying. ”

“ Rapid and insufficient heating invariably cracks the steel. If you want to stamp the end with the name of the steel, it is necessary that this is done at a good high orange color heat, as it is otherwise apt to split the steel. (Take your time, do not hurry.) HARDENING HIGH-SPEED STEEL In forging use coke for fuel in the forge. Heat steel slowly and thoroughly to a lemon heat. Do not forge at a lower heat. Do not let the steel cool below a bright cherry red while forging. After the tool is dressed, reheat to forging heat to remove the forging strain, and lay on the floor until cold. ”

“ Heat-treatments are designed to eliminate the stresses without losing the hardness and strength. This is done by tempering at a low heat. Avoid the "blue" range (350 to 750°C.) . Tempering for a considerable time just under the critical is liable to cause great brittleness. Annealing (reheating through the critical) destroys the effect of cold work.
FORGING High-speed Steel.—Heat very slowly and carefully to from 1,800 to 2,000°F. and forge thoroughly and uniformly. If the forging operation is prolonged do not continue forging the tool when the steel begins to stiffen under the hammer. ”

“ The ingots are relatively weak, and the tendency to crack due to cooling strains is great. For this reason the hot ingots are not allowed to cool quickly, but are placed in furnaces which are of about the same temperature and are allowed to cool gradually before being placed in stock. Good steel can be made only from good ingots.
Steel treaters should be more vitally interested in the important Page 168 changes which take place in high-speed steel during the hammering operations than that of any other working the steel receives in the course of its manufacture. ”

“ Cogging in a rolling mill does not break up and distribute the carbides and tungstides as efficiently as cogging under the hammer; another objection to cogging in the rolling mill is that there is no opportunity to chip surface defects developed as they can be under the trained eye of a hammer-man, thereby eliminating such defects in the finished billet.
The rolling of high-speed steel is an art known to very few. ”

“ Nearly a century passed between the making of the first practical engine and that one which now stands as the type of many thousands. But now every little saw-mill in the American woods could have, and finally did have, its little cheap, unscientific, powerful and non-vacuum engine, set up and worked without experience, and maintained in working order by an unskilled laborer. A thousand uses for steam grew out of this experiment of a Yankee who knew no better than to tempt fate with a high-pressure and speed and recklessness that has now become almost universal. ”

“ This alloy is so hard that it cannot be machined or drilled by ordinary means; it must be treated by emery or carborundum wheels. Yet it is so malleable that it can be used for rivets when headed cold. It is so tough that it may be bent and twisted at will without rupture, so that it forms railroad switches, frogs, and crossings of great durability.
High-Speed Tool Steels.
Until 1868, the steel tools used in lathes and drills, planers and so on, were limited to the moderate pace at which they remained cool enough to keep their temper. ”

“ Self-hardened steel has the useful property of retaining its hardness when heated almost to redness; therefore it may be used as a lathe or similar cutter upon hard work, such as cutting cast iron and other metals, at a much higher speed than is possible with ordinary steel, which would be softened by the heat generated by the high speed. This property makes self-hardened steel very useful and economical for many purposes. ”

“ Here is a huge planing machine travelling to and fro over a copper bar. A crank shaft has been cut out of solid steel by boring holes close together through a thick plate, and the two sides of the plate have been broken off, leaving the rough shaft with its edges composed of a considerable number of semicircles. The shaft is slowly rotated on a lathe, and tiny clouds of smoke arise as the tool nicks off pieces of metal to reduce the shaft to a circular shape. [138] Other machines, with high-speed tool steel, are finishing gear shafts. Fly-wheels are being turned and worm shafts cut. ”

“ America has been able to turn out munitions with a rapidity that has astonished the world and even ourselves, because through Niagara's influence the high-speed tool reached an unprecedented development in days of peace.
In the old days of carbon steel the machine that would cut rapidly would heat the steel so hot as to ruin its temper. Today alloy steel is not even fretted, much less put out of temper, by cutting speeds that would have been fatal to any carbon steel ever produced. ”

“ A good cam for an ordinary machine, such as a shear or punch, may be made of Bessemer or open-hearth steel where greater strength and endurance are required than can be had in cast iron; on the other hand, makers of cams for delicately adjusted high-speed machines where intricacy and accuracy are necessary will touch nothing but the very best crucible-steel of fine-tool quality for their work. It is of no use to suggest the greater cheapness of the other steels ”

“ Directly after we got running I received a letter from William R. Jones, superintendent of the Edgar Thompson Steel Company, running a rail mill recently started at Braddocks by Carnegie Brothers, saying that they were in need of an engine to drive a circular saw at a very high rate of speed to cut off steel rails cold. ”

“ Rough-grind while still hot and preheat to about carbon-steel hardening heat, then heat quickly in high-speed furnace to white heat, and quench in oil. If a very hard substance is to be cut, the point of tool may be quenched in kerosene or water and when nearly black, finish cooling in oil. Tempering must be done to suit the material to be cut. For cutting cast iron, brass castings, or hard steel, tempering should be done merely to take strains out of steel. ”

“ We may now picture this great Fleet, with its flotillas and cruisers, steaming slowly out of Portland Harbour, squadron by squadron, scores of gigantic castles of steel wending their way across the misty, shining sea, like giants bowed in anxious thought. We may picture them again as darkness fell, eighteen miles of warships running at high speed and in absolute blackness through the Narrow Straits, bearing with them into the broad waters of the North the safeguard of considerable affairs. ”

“ One of the most important developments during the Liberty engine program was the fact that it is not necessary to use a high-analysis alloy steel to secure a finished part which will give proper service. This fact should save the automotive industry millions of dollars on future production. ”

“ Improvement has followed improvement in composition, manufacture and heat treatment, so that to-day, instead of the cut at 30 feet per minute, which was a high figure with carbon steel tools, the modern lathe or shaper tool often works at 300 or 400 or more feet per minute, and, with sufficient power behind it, at somewhat lower speeds plows out 1⁄2 inch deep and 3⁄4 inch wide chips so fast that their removal to keep the machine clear is no mean problem. ”