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.