1942: Metallurgy

A war economy such as the world is facing today, may well be expected to have an important repercussion upon technical developments. That is just as true in metallurgy as it is in other branches of science. Steel, copper, aluminum, manganese, all of the more commonly consumed metals, have been in such tremendous demand for the production of war goods, that very little has been left for purely civilian consumption. Some of these metals have been so scarce that unprecedented measures had to be taken to insure their being used exclusively in the war effort. The need has been so great that extra precautions have had to be taken to forestall waste, and effect conservation.

During the past year conservation and waste-saving methods have undoubtedly taught the consumer much that he would not otherwise have learned. Such war-time restraints as have been found necessary have undoubtedly also developed ingenuity which technologists may not have hitherto exercised so readily, and have hastened improvements few thought possible twelve months ago.

The scarcity of tin resulting from the loss of Malaysia by the allied nations has made it necessary not only to set up a large tin smelter in this country, but also to expand detinning establishments for the recovery of tin. It has brought into full commercial use an electroplating process which requires only approximately a third of the amount of tin per given unit of area as was used in the older processes. Welding has been adapted and its technique so improved that there is a considerable saving in the metal required in a finished article, and a tremendous saving of time in prefabrication. No more spectacular example of this can be cited than what has happened in shipbuilding. Merchant ships are today being welded throughout, with a resultant immense saving in metal and in man-hours of labor.

So great has been the war demand for so-called scarce metals (scarce only because of war consumption), that unprecedented methods have been adopted for the collection and disposition of scrap.

Approximately 50 per cent of an open-hearth melt of steel may be scrap. The percentage has, at times during the past year, fallen as low as 40 per cent, but under such conditions the time of a melt is lengthened and the steel-making process prolonged. Steels containing both low and high alloy contents are usually made in the electric furnace and by the crucible processes. It has been found possible to recover some of the alloying elements, such as nickel, copper, chromium and manganese, etc., from scrap. This has proved to be a notable development.

The steel industry is thoroughly prepared to act upon such changes, as it has set up a committee to study metallurgical standards and to recommend changes consonant with today's realities. This committee has discovered by experiment that many of the richly alloyed steels can be replaced by leaner alloyed steels without jeopardizing the results. Changes and improvements in this field are not to be disclosed at the moment because of war censorship, but it is quite obvious that armor plate is important in this struggle, and any steps taken to stretch the available quantity of armor plate, even though it means the leaning up of the metallurgical specifications, is something greatly to be desired.

Early in 1941, demand for nickel began to exceed supply by a substantial margin. Armor-plate steel is toughened with nickel and the metal is added to stainless steel to enhance the ability to resist corrosion and to impart ductility. The United States produced only 554 tons in 1940, but Canada controls 90 per cent of the world supply. Cuba's large deposits of low-grade ore are being intensively developed.

Almost a year before Pearl Harbor, Industry's Technical Committee on Alloy Steel released the results of a study which showed how delicately blended compounds of chromium and molybdenum could do much of nickel's work in the electric and open-hearth furnaces of the nation. This change was abruptly nullified when chromium was put on the ration list early in 1942. A new set of steels had to be invented, each one as lean as possible in alloys. The Committee halved and quartered the amounts of alloys all along the line. Experimental heats were melted, tested, then put to use with results even better than anticipated. Many of the new lean steels — called the N.E. (National Emergency) steels — actually proved better at their individual jobs than some of the richer alloy steels used extensively in pre-war days. The Army and Navy now specify the new low-alloy grades as fast as favorable tests are reported.

An outstanding advantage of the new steels in war time, is that they require less virgin alloy materials, and can be made almost entirely from scrap steel. Scrap piles have become alloy mines. The Committee knew that because of the generally increased use of alloy steels in recent years, the residual contents of nickel, chromium and molybdenum were rising in both steel-plant scrap and purchased scrap, and they drew their plans accordingly. The yield of alloys from scrap has far surpassed all expectations.

In the post-war period, the intrinsic merit of many of the new steels will still remain and they will be thoroughly adaptable for peace-time applications.

Chromium is needed for tool steel, for armor plate, and ammunition. To meet military and essential civilian requirements in 1943, three times the tonnage used in 1939 will be needed. Large low-grade deposits of chromite ore, helpful in the emergency, have been developed in Montana, California and Oregon. The domestic output in 1943, as a result, will be as large as the pre-war imports, but the situation remains critical.

Eighty-five per cent of the world's molybdenum supply is produced here. Molybdenum imparts some characteristics to alloy steels that no other metal does. In the early stages of the war it was widely substituted for tungsten, chromium, nickel and other scarce alloys. Now the formerly plentiful metal is also scarce. It is expected, however, that domestic supply will increase about 15 per cent in 1943.

Large imports of tungsten in 1940 and 1941 helped build a stockpile of this metal, needed for cemented carbides and tool steel. Domestic production has been stepped up sharply in the last few years and a California deposit has been developed which will yield 17 per cent of the new tungsten this year. Idaho is producing 27 per cent of the domestic tungsten. The net shortage of tungsten in 1942 was estimated at somewhat over 10 per cent.

High-speed cutting tools are made of tungsten steel, because the metal stays hard at high temperatures. Production in this country amounted to 5,120 tons in 1940, but for 1942 the amount available was about twice as great. Idaho deposits were found when the situation looked blackest. Bolivian ore is another source that helps offset the loss of China's excellent tungsten ore, once the major part of United States supplies.

Domestic production of vanadium has doubled since 1937, but imports in 1942 were down somewhat from 1940. One large domestic producer is making arrangements to mine a very low-grade marginal ore which will yield an additional 2,200,000 pounds of vanadium. In 1943 production of this metal will be doubled and WPB officials do not expect a serious shortage.

Nickel is essential for steel for armor plate — projectiles, tool steel, engine parts and guns. Nickel is produced in the United States only in negligible amounts — about 3,500 tons annually, as compared with Canadian production in 1939 of 102,000 long tons. Much nickel is gathered from scrap materials. Essential 1942 demands were about four times those of 1938, they will jump to five times in 1943. The most significant possibility of expanding American supply is increasing nickel imports from Cuba.

Added to lead, antimony makes a metal brittle enough for bullets and shrapnel. Antimony sulphide is used as a primer for shells. The United States has never produced much antimony from mines, and in 1940 the take had dropped to 494 tons. Most antimony has come from China. When that source was cut off, new smelters were set up to process ore from Mexico and Peru. Fortunately deposits in Idaho turned out to be larger than the reserves marked out in preliminary explorations.

About 12.5 pounds of manganese is needed to desulphurize and deoxidize every short ton of steel. Standard grades are made only from high-grade ore, and United States stocks of high-grade ore are small. In peace time, about 97 per cent of our supply comes from abroad, mostly from Africa, Russia and British India, so that main sources of manganese still are controlled by friendly nations, but shipping shortages make sources in this hemisphere more important. Brazil and Cuba are increasing their normal shipments to the United States. Within the continent, reserves of low-grade ores in the southwestern and eastern states are being exploited with new reduction methods.

Germany and Italy control the world's greatest supplies of mercury. Mercury is used in anti-fouling paints for ships, in fungicides, and in scientific work. Mercury fulminate is a sensitive compound used to set off the main charge in explosive shells, but lead azide is replacing it. United States mercury production amounted to 37,777 flasks of 76 lb. each in 1940. Reserves of mercury were dwindling fast until discovery of a new source in Idaho bettered the position. With output from Mexican mines increasing, and new deposits opened up in Canada, the outlook for mercury is more promising than it has been.

Magnesium in its combined state is the fifth most abundant metallic element in the earth's crust. It is present in sea water, in brines occurring in underground deposits, in magnesite, dolomite, brucite and other calcine ores which are present literally in hundred-mile patches in the United States. Magnesium is separated from ores by three processes. The first draws magnesium salts from magnesite and other ores by combining chemicals with the ores. The magnesium salts then are broken down by electric current, into magnesium metal and the by-product chemicals.

Other ore processes employ gas or other forms of reducing agent instead of electricity, and are important because they help relieve the pressure of demand for electric power. Most important in this category is the ferrosilicon process. Ferrosilicon is an iron alloy made from common sand mixed with low-grade iron ore or scrap iron. It is added to prepared dolomite, a common limestone ore, and the mixture is heated in a near-vacuum, to distil magnesium metal.

The raw material from which aluminum is made is now produced from low-grade bauxite and clay under a new refining process. This process would enable alumina plants to mix a substantial quantity of clay with high-grade bauxite, conserving the limited domestic bauxite supplies. The refining process can also be used to extract alumina from low-grade bauxite.

1941: Metallurgy

Strategic Metals.

An economy based upon the national emergency began in 1941 to dominate metallurgical thinking in the United States. For strategic reasons many of the changes in practice may not yet be revealed, but the well-publicized metal scarcity due to war's requirements gives a quick picture of the change that is taking place. For the more scarce metals, such as aluminum, copper and zinc, other and less scarce metals and substitute materials are being used. Steel and iron are being adopted in many instances where good substitutes for steel or iron are unavailable. The impetus given by the war to research in the laboratory and to commercial practices in the plant is therefore the most significant single development of the past year.

Army and Navy Munitions Board pronounced these metals as strategic: antimony, chromium, manganese, mercury, nickel, tin and tungsten. Aluminum would be useless for many aircraft applications without the alloying toughness of other metals. Ferro-alloys are in large-scale production, and Europe has yet to catch up with the magnitude of operations in the United States.

From one-third to two-thirds of all the world's production of chrome ore over the last twenty years has been consumed in the United States. Ferro-chromium is not only the main alloy in stainless steel, but it goes into a variety of tough, high heat- and corrosion-resistant engineering steels, airplane and automobile engine parts, tractors, tanks, trucks, armor plate, armor-piercing projectiles, ball bearings, and a host of items vital to a mechanized age. Today ferro-chrome is available with almost any desired carbon content, due to improvement in furnace technique, and there has been produced a high-nitrogen ferro-chrome for special purposes. Owing to the relative scarcity of chromium and the need of that metal in defense, its use in the making of automobiles and other articles of civilian use has been curtailed. Also substitutes for tin have been sought, and it has been suggested that silver be used as a replacement in solder.

Stainless Steel.

One of the most interesting projects is the further development of stainless steel for use in aircraft production. Special heat treating of cold-reduced stainless steels has increased its strength and enhanced its possibilities in fabrication and consequent application to airplane building. This new aircraft steel can be used with high production efficiency, allowing spot welding as against slower and more costly welding and riveting. It is five times stronger, though three times heavier than aluminum. This new weight-strength ratio would mean a complete re-engineering of present plane designs. Maybe the hard pressed aviation industry has not the time just now for anything too revolutionary. The aircraft stainless steel, nevertheless, is already going into sub-assemblies and certain types of wings. It will provide the aeronautical engineers with a new margin of strength from which to squeeze a greater performance record.

Other Metals.

In the present emergency, when chrome ores are all imported, there has been developed a low-carbon ferro-manganese and there has been a pioneering of the so-called low-alloy manganese tonnage steels, in the structural and transportation fields, broadening the whole alloy business.

Calcium, once obtained chiefly from France, and cobalt, once obtained from Belgium, are now being produced in the United States in sufficient volume to meet all needs.

Three pilot plants at Boulder City, Nev., have been started to refine manganese oxide ore by a new reverse flotation and electrolytic process. This may be possible where electricity is cheap and plentiful, and the United States Bureau of Mines is hopeful that they can, by these experiments, prove the practicability of relieving the dependence of the United States upon foreign sources for manganese by making use of our own deposits of manganese ore.

Steel for defense is dependent upon its own special kind of vitamins, which are known as ferro-alloys. Manganese permits hot steel to be rolled without cracking, while zirconium helps to prevent cracking when cold steel is pressed or drawn over dies. Manganese and silicon hasten the exit of strength-stealing impurities. Steel used in axles, crankshafts and springs is toughened and strengthened and made tireless by chromium and vanadium. It is the chromium in stainless steel that renders it rust- and corrosion-proof. And columbium further fortifies stainless steel for fabrication by welding and for high-temperature service. Chromium, tungsten and cobalt make possible engine valves which defy the terrific punishment of high temperatures and the erosion and corrosion of hot exhaust gases. And the very tools and dies that are so essential in steel fabrication, derive their strength, hardness and durability from tungsten, chromium and vanadium.

Electric Alloy Steel.

A plant to produce electric alloy steel, financed by the government, was started at Chicago. It will have a capacity of 504,000 tons of alloy steel ingots annually, producing 317,000 tons of parts for aircraft and ordnance use. It is the first plant in the country in which every unit, from ore to finished product, is designed to produce electric furnace alloy steel. Private management has been quite willing to devote their facilities to the government's needs, but, in many instances, those facilities have been inadequate. Therefore, public moneys have been enlisted to furnish the added facilities. Since these new increments in plant will be privately managed, it is but reasonable to expect that whatever improvements they may contribute to the general advancement will ultimately be incorporated in civilian uses after this war.

Welding.

Welding very naturally has been adopted to a degree never before attained. Not only are steel ships being welded, but welding has been used more extensively in the making of airplanes, tanks, trucks, guns and gun carriages and the innumerable other instruments of war. The wider adoption of welding has, of necessity, changed the metals used and the metallurgical practices in the producing of those metals. The more stringent standards of the Navy and of the Army have been more widely adopted and these improved standards will very likely spread to ordinary commercial practice once this war is over.

Improvements and Developments in Metallurgical Processes.

Under the extreme urge of war, special attention has been given to the need of light metals and tougher metals. Since this is a war of machines that move, it is essential that all possible weight be saved, and since the machines must go into areas of great dangers they must be protected by armor plate or similar protective coverings. Tougher metals and lighter metals must be had without a sacrifice to the workability of the metals which otherwise would retard their conversion into machines. The steel industry in particular has already made great progress in the continuous rolling of iron and steel in continuous tubing. It is now endeavoring to adopt some of the same processes in a continuous forming from the melt. These operations have for their purpose not just to increase the supply of metals for war, but to shorten the time between the ore and the completed machine in the field.

Processing of metals comprises an essential part of the national defense program. These few instances of improvement or change are therefore cited as typical and indicative. They are by no means inclusive of everything of this nature. The improvements in the metallurgical microscope and in the technique of the preparation and microscopic examination of metal specimens have been generally recognized. Modern metallurgical microscopes have been put in use at many of the steel plants and are proving important tools in the development of new alloys and the maintaining of close quality control on the many specialized grades of steel that are being made.

So-called powder metallurgy has also made considerable progress during the year. This is in effect the use of powdered metal which is pressed into a finished shape under very high pressure and then sintered. This powdered metal replaces certain machined parts which otherwise would be cast, forged, rolled, extruded, hammered, machined, hobbed, drilled, milled and ground. The process has gained a following, especially in the automobile field where it is used for the production of bearings as well as for some other parts. Advantages claimed for it in bearings are that it is light in weight and has a porosity which enables the parts to absorb large quantities of oil, giving them semi-permanent built-in lubrication. It is also now being adopted in typewriters and other clerical machines because the parts made of powdered metals are quieter and cheaper.

The fact that many refugees have left the invaded countries of Europe and taken refuge in England and the United States has also contributed something to the improvement of metallurgical processes. The countries of their adoption have profited by the addition to scientific minds. This is indicated in the adoption of additional processes for metal extrusion in England. One such process was developed in Czechoslovakia and perfected in England. See also CHEMISTRY; MINERALOGY.

1940: Metallurgy

Steel Mills.

Organized metallurgical work on a plane which might be termed 'productive research' in the steel mills has been probably the most important development of the year. This was started some few years ago by some of the larger steel companies in creating a staff of metallurgical observers. To that staff largely was encharged the problem of making sure the steel produced came up to the standard set by the metallurgical department. The observers are usually recruited from the graduates of technical schools and assigned to watch the various processes in the making of steel. Observers are usually not responsible to the metallurgical department but to the operating department. Each department of a plant has a departmental metallurgist. These are graduates from the younger group of metallurgical observers. The department metallurgists, such as the open-hearth or the bar mill metallurgists, are under the main or chief mill metallurgist who reports directly to the chief metallurgist of the plant. Each department metallurgist is held responsible for the metallurgical practice in his department. It is the duty of the observers, by checking additions, temperatures before and after pouring, slag conditions, lime-silica ratio, ingot molds, and numerous other details however small, to report on each step. This independence makes their work doubly effective.

In this manner the steel mill is able to insure the output of a product that definitely fills some commercial need, and the metallurgical practices of the mills are keyed to that primary purpose. In the past year or so, however, the organization has gone much further. Competitive mills are now more willing to exchange technical information and metallurgical experience. Committees on metallurgical practice for the industry have been set up, and these, in turn, are today cooperating fully with the Government to insure the best products for the national defense needs.

Codifying Types of Steel.

The industry is now endeavoring to correlate and codify the chemistries of steel which are now being made, and to determine which steels are made in reasonable quantities, as well as the purpose for which these steels are used. The objective is to advertise the steels which are made in significant quantities or which, for strategic reasons, are significant. It is proposed to publish the list under chemical designation, physical designation, or use designation, dependent upon the method of ordering now customary. This will, when adopted by the whole industry, provide an unbiased method of selecting a steel for a purpose and prove extremely useful to the operating and technical men of the steel industry.

An immediate objective, which is promised solution more expeditiously through this system of cooperating, is the development of a steel that will respond better to machining, hence permit higher speeds or heavier feeds. Improvements have been effected in heat treating, in the processing of armor plate, in the development of homogeneous light armor, and other metallurgical processes. War requirements have also increased the demand for so-called rustless steel, some kinds of which are now being produced in volume sufficient to establish them as basic grades. Thus the metallurgists in our mills are increasingly aware of the importance of concentrating sales effort, production control, and plant research on the relatively few steels which make up the large part of the tonnage manufactured and consumed, rather than scattering this research work, production and sales effort over a wide group of steels relatively insignificant from a tonnage standpoint when considered for the industry as a whole. The necessity for concentrating research can be illustrated by the fact that no man knows all the properties and possibilities of a simple carbon steel, and to learn them will take years of painstaking effort. As a matter of fact, many of the small tonnage items are metallurgical 'fads' and are better replaced by more common compositions. Others are useful tools and will remain as such. This is certain to bring about a great improvement in the uniformity and quality of tonnage steels, to the great benefit of the larger group of consumers.

Effect of the War on Metallurgy.

Necessity may be the mother of invention, but it does not always predetermine the trend of discovery, as the human mind cannot fix the results of the test tube. The war in Europe, however, has had a tremendous impress upon metallurgical trends. This being a mechanized war and the airplane requirements proving so large, some effort has to be made to conserve raw materials and to improve the fighting machine. The British Standards Institute prepared aircraft material specifications, and attempted to coordinate specifications for steel and non-ferrous materials to facilitate supply. It prepared standards for metal containers for the various industries to provide for the economic use of materials and machinery and issued some forty-five specifications in connection with air raid precautions for the Ministry of Home Security. As soon as the new defense program for the United States had been voted by Congress in mid-summer, a like effort was initiated in this country to standardize and simplify specifications. As usual, this was concomitant with a serious report of a rubber substitute, an increased interest in electric furnaces, because of the anticipated demand for alloy steels, and similar adjustments of industry to anticipated war requirements.

The metal industries of Germany have long been a part of their totalitarian government. Specifications were rigidly fitted into the war's requirements. The resulting 'blitzkrieg' has not only affected politics but the science of metallurgy as well, and as the concluding months of 1940 approached some idea of what these are becomes a little more apparent to the war makers.

Strategic Metallurgical Materials in the Defense Program.

Certain strategic materials are not available to us in sufficient quantity from our domestic sources.

Congress made appropriations to purchase strategic and critical materials. Purchases were made of tungsten, chromium ore, pig tin, manganese ore, quartz crystal. Plants to produce aluminum and other critical metals have been projected.

For war many special specifications will prevail. Some 660 specifications are listed in 'The Index of U. S. Army and Federal Specifications used by the War Department.' These do incorporate many of the specifications in commercial usage, but the exacting requirements of some war materials, such as combat weapons, make it imperative that the government's requirements be protected by special specifications not generally in common usage. Probably the AN — Aeronautical Specifications and specifications for shell steel are more significant of the latter.

During the year, and undoubtedly for some time to come, the greater effort of metallurgists will be devoted to defense needs. The National Inventors Council, at the request of the Advisory Commission to the Council of National Defense, had indicated the following new things as most urgent from the standpoint of national defense:

Cement for quickly bonding rubber and metal.

Material to which ice would not adhere, for use on airplane wings, highway surfaces, windshields, etc.

Improvements in methods of aircraft construction, such as flush riveting or spot welding to achieve absolutely smooth external surfaces without introducing serious maintenance problems.

More uniform grades of foundry molding sand, probably synthetic.

Easily operated indicator for temperatures of molten steel, both in the melting furnace and in the pouring ladle.

Temperature measuring device that will give readings from 1,500-3,000° C. and above. Optical or radiation pyrometers, because of the gas atmosphere in the temperature pipes, produce erroneous readings.

Tools for welding structural steel in the field. While welding is now pretty general in shop practice, it is expensive on location jobs.

Boilers which will not accumulate scale.

If cast iron could be developed that would bend under stress rather than burst, it would be the greatest single development in the industry. Such an iron has been made for laboratory tests.

Stainless steel that has a yield point of 150,000 lbs. per square inch. Such a material would be extremely valuable in aircraft construction.

Free machining, heat and wear resisting steel bars suitable for machine gun barrels.

A steel alloy which will cast readily, machine freely, and be acid and heat resisting.

Metal alloy that would resist pitting from electrical arcs.

Small diameter steel wire which would be rustproof without coating and without the expensive stainless process.

Of inestimable value to manufacturers of bearing bronzes would be a material to take the place of tin in bronze alloys.

Soldering flux that will not cause corrosion of soldered parts in service.

An aluminum solder to work as well as common lead solder does on tin.

An economical process for the recovery of manganese from low grade ores.

These are only a few of the problems posed for the organized metallurgical brains of the American industry. The war emergency is directing first attention to these, but other needs, the commercial needs, are legion, and the problems confronting the profession truly warrant such a mass approach to their solution as the newer organization in the industry has provided. (See also CHEMISTRY: New Applications of Metals; MINERALOGY.)

1939: Metallurgy

In 1938 an inquiry was addressed to two thousand research men in the United States, Canada, England, France and Germany, asking what would be the outstanding contribution to research in their particular field within the next three years. In the field of metals the responses were: cheaper chromium steels for railroad rolling stock; sheet metal with adherent colored surface for store fronts, autos, house trims and toys; direct casting of copper, aluminum and alloys; production of manganese from domestic deposits; synthetic mica; electroplating color on metals. These replies would scarcely seem to indicate that any metallurgists anticipated an outbreak of war, nor were they especially concerned with metallurgical problems directly related to war. From this we are inclined to conclude that scientific research is a gradual process, the direction of which is not deflected by international emergencies but only quickened by those emergencies.

Trends in Metallurgical Research.

While the leading countries of the world were still at peace and while only a few of the responsible diplomats were thinking of the possibility of war, the National Bureau of Standards in the spring of 1939 held a meeting with its metallurgical advisory committee. The projects then discussed were: copper-base wrought metals '85-5-5-52'; elastic properties of cast iron; foundry sands; high-purity iron; refractories for use in melting high-purity metals; 'gases' in metals; plastic deformation of metals; pipe corrosion; water-treatment to retard corrosion of steel; weathering of aircraft sheet metals; treatments for improving the permanence of magnesium alloys; roofing materials; painting of steel to be used in building construction; silver research project; high-temperature creep of metals; low-temperature properties of aircraft structural metals — impact resistance; thermal transformations in steel and grain size; quality of carbon steels; weather exposure of aircraft sheet metals; accelerated testing to determine susceptibility of aluminum alloys to inter-crystalline corrosion; does continued fatigue-stressing of a steel below its endurance limit seriously affect the metal; significance of a ductility requirement in specifications for metals; study of torsion-impact tests; soldered joints in copper tube plumbing; improved metallographic technique; fatigue of chromium-plated steel; new micro-hardness tests; oxide coloring of steels; elastic properties of high-strength aircraft structural metals; and standard chemical analytical samples.

Few of these projects, indicative of the present advance in metallurgical practice, were directly allied to war needs. But many of them will be quickened by the war requirements and, while this world catastrophe may prove to be a great loss to humanity, it may yet prove of great benefit to scientific knowledge. In the United States the trends noted have all been towards improving economy and quality. This was especially the case with two improvements in methods announced during the year.

Steel-making Improvements.

In part because the quality of the steel can be more easily controlled during the making, the open hearth method has for years grown in popularity. But the open hearth method is slower than the Bessemer method and therefore more expensive. To offset this, several different methods have been or are being developed for measurement of temperatures of steel in the converter. It was revealed this year that Herbert W. Graham, metallurgist for the Jones & Laughlin Steel Corporation, had perfected a method of control for the Bessemer converters with a photo-electric indicator. This 'electric eye' will judge the color and brilliance of a flame of a Bessemer blow better than a human eye can do, and makes it possible to turn out steel with Bessemer rapidity but of a quality more nearly comparable to that of the open hearth product, particularly with respect to uniformity.

G. Naeser in Germany has also made some contribution to the art of steel-making by using the 'Bioptix' color-pyrometer to measure radiation. This method of observing the changes in temperature and the changes in amount and intensity of the radiation emitted from the surface of molten steel aids in determining what is going on in the bath before casting. It thereby enables any necessary corrective measures to be taken in good time, thus reducing the number of rejections.

Alloys.

Patent rights to produce a cemented titanium carbide alloy in the United States have been acquired by the Firth-Sterling Steel Company. This bears the trade name of cutanit and its manufacture in Europe has paralleled the increase in armament production, since its use in cutting tools may have been given impetus by the manufacture of big guns, rifles, shells and other war materials. It has been indicated that titanium carbide may be effectively added to cemented tungsten carbide materials, thus forming a double carbide of tungsten and titanium. This alloy will relieve our dependence on foreign sources of tungsten.

An increasing use of stainless chromium-nickel steels in aircraft is now logical. The lower specific gravity of the light alloys commonly used is compensated for by the higher strength of the stainless steel which, in conjunction with its corrosion-resistance, enables the latter to be safely used in many thin sections, thus bringing the weight of the completed structure down to an equal basis. Wings, tails, fuselage and under-carriage parts have been made of '18-8' stainless in experimental jobs, and the material has been definitely adopted in production for ailerons, flaps, ribs, tanks, etc. Recent European military planes have standardized on stainless for such parts.

Improved methods have been found to produce high tin bronzes. The corrosion-resisting qualities of the new bronzes are improved, thereby making them particularly useful for many parts of machinery which must withstand both stresses and corrosive attack, such as studs and other fittings on ships' hulls, cocks and valves, and on high-speed motor boats, impellors, shafts and stern brackets.

The few examples here cited afford but a brief outline of the art of metallurgy as it developed during the past year and but a glimpse into the possibilities that are ahead. A long mechanized war in Europe might bring about an acceleration of developments now only beginning. See also CHEMISTRY.

1938: Metallurgy

Stainless Steel.

On Dec. 13, 1938, more than a hundred industrial leaders gathered in Pittsburgh to celebrate the twenty-fifth anniversary of the discovery of stainless steel. This was a significant fact in many ways, particularly in that it dramatically marked a new trend in the science of metallurgy. For years man had practised the art of extracting metal from ores, thereby creating the science of metallurgy. With the discovery of stainless steel, however, the effort of the metallurgist has been turning more and more to the art of combining various basic metals to create new products or a product capable of performing a specified and predetermined use.

Twenty-five years ago two men, one in England, Harry Brearley, and one in the United States, Elwood Haynes, started the era of chrome-bearing stainless steel. A third, Dr. Benno Strauss of Germany, almost simultaneously with Brearley and Haynes, conceived an alloy containing not only iron and chromium but also nickel. All had this one thing in common — stainless properties of alloys. Out of those discoveries has come a great new era of metallurgy.

From this discovery, too, have come innumerable brands of compositions, variously estimated at one thousand or more different combinations. One of the most significant recommendations in this twenty-fifth anniversary gathering was that to standardize some thirty types, thereby making possible greater economies and more stable products. Whether or not this is done, the fact stands out that the achievements to date have been primarily to concentrate attention on the great variety of products and the versatility of metallurgy in meeting today's commercial demands. An overlapping of types and a confusion of specifications may have threatened, but the movement now set on foot should go a long way towards correcting those unfortunate tendencies. No stabilization is expected which will rob alloyed metals of their prime virtue, namely of commanding a specification best suited to the needs of the resulting product.

Refining and Processing Iron Ores.

Next to oxygen, silicon and aluminum, iron is the most widely-distributed metal and the largest part of the solid material in the earth. It constitutes probably a little over 4 per cent of the earth's crust. That most notable advances have been made in the refining and processing of iron ores should, therefore, occasion no surprise.

Among the more recent discoveries of vital importance are those relating to the microscopic study of metals, high-temperature and creep properties, as well as many others affecting not only the development of new alloys but the improvement of existing alloys and the adaptation of these materials to the special requirements of modern engineering. Especially noticeable has been the work of the research metallurgists in contributing to engineering knowledge of such important factors as mechanical and corrosion fatigue, creep under stress at both normal and high temperatures, factors which influence brittleness in steels and machining properties and, above all, the intensive study of reactions of corrosive agents, whether from atmospheric or from other causes.

Great improvements have been made in the furnaces in which metals are refined. The use of forced draft and then the application of electricity have each marked advances. Today practically all stainless steels, so-called, are made in electric-arc furnaces, most of which have a capacity of thirty tons. Thus tonnage production for some of the stainless types is being ushered in.

Uses of Alloys.

Nickel steel was introduced about 1890. It was a decided innovation and had important results upon the industry. Today alloy steels are working an even greater metamorphosis. They are making possible better automobiles and airplanes, new light-weight trains, and causing a tremendous revolution in all lines of transportation for these steels are making possible stronger and lighter carriages. These are but the beginning, for metallurgists foresee even wider and still newer uses to which the metal may be put.

Pure aluminum, while possessing many valuable engineering properties, is too weak and soft for a number of engineering purposes for which it is otherwise naturally suitable. Many efforts have been made to improve its application by adopting alloys. In 1911 duralumin was developed and has found extensive use in the construction of Zeppelins. There has followed what are known as the 'Y' and 'RR' aluminum alloys. Magnesium alloys have been developed to provide an ultra-light material possessing reasonable strength.

Iron and Steel Alloys.

Out of some forty possible elements which might be intentionally added to iron or steel, there is a surprisingly small number which, up to the present time at least, have been found to have sufficiently beneficial efforts, at a reasonable cost, to warrant investigation and commercial development. Without regard to relative importance, these are manganese, silicon, chromium, nickel, molybdenum, tungsten, vanadium, titanium, aluminum, zirconium, copper, cobalt, and the non-metallic elements, phosphorus, nitrogen, sulphur, selenium and oxygen. Carbon is invariably present in all steels except in the instance of certain grades of the highly-specialized stainless alloys, where the carbon content is only a few hundredths of one per cent.

Chromium is the only alloying element which has been found to produce in iron alloys a condition approaching complete resistance to atmospheric corrosion. Chemical and metallurgical tests indicate that more than 11 per cent chromium is necessary to provide this characteristic even in pure iron. The presence of carbon in the commercial alloy necessitates an additional amount of chromium because, under certain conditions, each unit of carbon may combine with as many as eighteen units of chromium and render that portion of the alloying element ineffectual in its protective function. The remainder of the chromium forms a homogeneous solid solution with the iron, and imparts to the alloy its notable resistance to corrosion.

Of all the alloys, however, the greatest progress in recent years has been made with the use of chromium and nickel. Chromium mixed in small amounts with steel improves its hardening qualities. In a quantity of more than 10 per cent of the whole mix it prevents rust. This type of steel is used in the making of tools, machinery parts, and stainless, heat- and acid-resisting steels.

Nickel increases the toughness, stiffness, strength and ductility of steel. When used in large amounts the steel will resist heat and acids. This steel is used in the making of tools, machinery parts, and stainless heat- and acid-resisting steels.

When using both chromium and nickel in the steel it acquires unusual characteristics. It is this type of steel which is today commonly known as stainless. The most common prescription is 18 per cent chromium and 8 per cent nickel. A variation of these percentages is used in order to obtain special results. This steel may be grouped under three classifications.

Classification of Stainless Steel.

The austenitic steels are those in which nickel exceeds 7 per cent, and nickel plus chromium exceeds 24 per cent, with or without moderate additions of other elements. These steels are normally non-magnetic. While they cannot be hardened by quenching, they may be hardened materially by cold working and in such cases become slightly magnetic. In the annealed condition they possess higher ductility and toughness than ordinary steels.

The ferritic steels contain chromium in excess of 16 per cent and 0.12 per cent maximum carbon, with or without small additions of other elements. These steels show no significant transformation on heating or cooling and hence remain essentially ferritic at all times, and are magnetic. They are only slightly hardened by quenching, and are hardened only moderately by cold working. They possess relatively high strength and when properly annealed are quite ductile.

The martensitic steels have chromium of 15 per cent maximum, carbon 0.12 per cent maximum (although in stainless cutlery steels the carbon may run as high as 0.30 to 0.40 per cent), and other elements, if present, not exceeding 2 or 3 per cent. These steels are ferritic in the annealed condition, but when cooled rapidly in air or liquid media from above the critical point, they are definitely hardened and hence called martensitie. They may be hardened and tempered as ordinary carbon steel, and possess excellent physical properties of strength and toughness. They are magnetic.

It is significant that these more recent and outstanding developments in the metallurgy of steel have resulted from a more profound study of the uses to which the product is to be put. This approach to metallurgy is destined to have its important effect upon all phases of its practice.