Science Communications - Publicity for Technologya


hot recipes
U.S. Steel's Technical Centers Follow a Long
Tradition of Research and Development

Although steel's triumphant role in enabling the industrialization of planet Earth is evinced by innumerable classes and types of steel, it is ironic that steel's very ubiquity makes it all but invisible to us.


To take an unlikely and mundane example: The books on your shelf are made of paper from trees that were cut with steel saws, hauled on steel vehicles, shredded in a steel pulp grinder, processed on a steel paper mill and printed on a steel printing press with ink that was ground, blended and mixed with steel equipment. One way or another, directly or otherwise, each of our lives is touched by steel, of numerous types, in many forms, scores of times, every day. The irony of steel's quiet presence at every turn of our lives is annealed by the fact that planet Earth all but overflows with the raw materials of iron and steel production. Consequently, the principal challenge resides not in finding the ingredients, but in finding the recipes. That challenge has been a motivational touchstone of mankind's industry for millennia, and remains so today.


In meeting that challenge through the centuries, what began as a haphazard search for Mother Nature's primary methods and Mother Earth's basic materials has evolved into the science of advanced metallurgical research: The quest to discover the smallest, deepest, most closely guarded secrets of the natural world. For the past 80 years, the discovery of many of those tiny secrets has taken place at United States Steel's Research and Technology Center, originated in 1926, moved to Monroeville in 1956 and relocated over the past few months to a new facility at the Waterfront in Munhall, Pa., on the same site as the company's retired and renowned Homestead Works.


According to Fred Harnack, General Manager of Research at the center, the most recent move was prompted by the company's continuing commitment to research and development. “Throughout its history U. S. Steel has placed a great deal of importance on research and development of new products and processes,” Harnack said. “This move is a significant investment by United States Steel and a good sign of the importance of research toward our long-term strategy in a global market. I'm quite pleased to be part of it.” The center, which remained fully functional throughout the relocation process, provides a full range of product analysis services, including metallurgical evaluations for the company's domestic operations, and technical support for its European manufacturing operations, as well as expert assistance for customers.


In addition it is responsible for new product design, development and testing. From an historical perspective, the new technical center is part of a long tradition throughout the iron and steel making industries. For centuries before the advent of institutional laboratories, research was an essential, if informal, part of the art and science of iron and steelmaking. In times past, iron and steel research concerned itself with the practical issues of remedying problems that occurred in actual use with shop-floor solutions that originated with a scratch of the iron master's head. Today, vast funds of knowledge, along with advanced instrumentation, permit the infinitesimally close and exquisitely precise examination, analysis and testing of the compositional nature and performance characteristics of iron and steel materials, processes and products. That is not to say the search is over. Only that today it is deeper than any iron master of days-gone-by would ever have imagined.


Early History

For purposes of discussion and contemplation, it is important to remember that iron is an element, of which steel is an alloy. Iron's key ingredients are: mineralogical iron ore, a blast of air and intense heat. Steel's key ingredients are refined molten iron, oxygen and carbon. Happily for us all, air is everywhere, carbon is a key component of all living things, and iron is the fourth most abundant element in the Earth's crust, at about five percent. If five percent doesn't sound like a lot, rest easy - the Earth's core is about 90 percent iron.


On the other hand, and somewhat unhappily for us, virtually all that iron is locked up in the form of iron compounds. That is because in elemental form, iron's atomic makeup gives it fewer than half the full complement of electrons in its outermost electron shell. And, in accordance with Mother Nature's rules of elemental bliss, iron, like its sibling elements, wants all its electron shells to be fully occupied. As a consequence, iron atoms have a strong tendency to bond with other elements, such as oxygen, hydrogen and sulfur, to form compounds, some of which are suitable for use as ore. Unlike precious metals, the biggest problem with iron is not finding it, but figuring out how to break the metal away from its partner elements in the compounds in which it occurs. That's where heat and its sidekick, flux, come in. Because iron's melting point is 1530ºC (2786ºF), it won't melt in an open fire. However, when combined with carbon, from burning charcoal for instance, and with the assistance of a flux, such as calcium from crushed limestone or seashells, it is possible to persuade the ore impurities to abandon their ferrous mates and run away with the flux at temperatures as low as 800ºC, leaving behind a lump of rough iron metal. Nonetheless, 800º C is 1472º F, which is far hotter than the average campfire. That's where the air blast comes in.


Given the archeological record, it is not hard to imagine one of our prehistoric ancestor's amazement upon the discovery, in the campfire ashes of the previous windy evening's ritual clambake, of a lump of slag-laced, low-purity iron, accidentally reduced from an unwittingly introduced piece of iron-bearing ore. He would have likened it to 'star metal' (meteoric iron, to us), a highly valued stone that, unlike other stones, would not break when hammered, but rather, changed its shape like gold or bronze but, unlike its haughty relatives, kept its edge in work and war.


Through the centuries, the industry that began on that fortuitous day as an accident of chemistry and physics evolved within the dim light of black art. The campfire became a hillside pit filled with burning charcoal and iron ore inspired by a worker's breath through a pipe of clay to intensify the heat. Firing pits became blooming forges. Lung-driven blowpipes became water-powered bellows. Secrets passed from father to son. The place of the ore's origin foretold of the metal's character. Slag was beaten out; carbon, roasted in. Materials were assayed with looks, licks, bites and sniffs. Heats were timed in psalms and prayers. Innovations that worked were welcomed to the art. Those that did not were left in the dust of the hearth. During the Dark Ages, many forges came under the management of religious orders. Closely kept trade secrets were lost, some never to be re-found.


Perfecting the Process


Then, with the onset of the chemical revolution in the late 18th and early 19th centuries, the crude observational analyses previously employed by iron and steel artisans were gradually displaced by Lavoisier's stoichiometric approach, which defined materials in terms of their proportional elemental compositions. (Think H2O: two hydrogen atoms plus one oxygen atom equals water, and only water - then, now, forever). During that period, the renowned scientist, Michael Faraday produced the first steel alloys in his laboratory. At about the same time, the lesser-known David Mushet, conducted methodical experiments designed to optimize steel making in a laboratory furnace. Although he never enjoyed the fruits of his labors, Mushet is credited with having greatly improved the Bessemer process by making the steel less 'wild,' i.e., more uniform from one batch to the next. Even today, it is sometimes called the Mushet-Bessemer process. The key advantage to the Bessemer process was that cheap, clean steel could be made without re-melting or reheating iron. The 'converter,' as it was called, was an iron vessel lined with firebrick that tilted to receive a charge of liquid iron directly from a blast furnace and tilted back to vertical so that air could be injected into the melt for two purposes: First, to associate residual impurities with oxygen to formed oxides, both gaseous and liquid. The gases were vented to the atmosphere. The liquids, which were less dense than iron, floated to the top as slag, to be skimmed. The second reason for injecting air was to promote the gas-phase association of excess carbon in the iron with oxygen from the injected air, thereby reducing carbon levels to about one percent, the desired amount for steel.


In 1872, much to Pittsburgh's good fortune, Henry Bessemer and Andrew Carnegie made each other's acquaintances, whereupon Carnegie foresaw that inexpensive steel would inevitably supplant brittle and wear-prone iron as the material of choice for railroad rails. Although Carnegie was neither metallurgist nor scientist, he had an enduring commitment to advancing technology and an uncanny ability for matching it with market opportunities. His business acumen never shone so brightly as when his association with the Pennsylvania Railroad and the Keystone Bridge Company converged with Henry Bessemer's converter, Henry Clay Frick's Connellsville coke and Minnesota iron ore. In consideration of this fortunate alignment of resources, Carnegie decided to build a steel mill for the manufacture of steel rails. Located a few miles from downtown Pittsburgh, named after the president of the Pennsylvania Railroad, we know it still, as the Edgar Thomson Works.


In keeping with his commitment to innovation, Carnegie also installed a recently resurrected technology called the open-hearth furnace at Edgar Thomson. The open-hearth method was a variant of the ancient 'puddling' technique in which iron and steel were collected as a lump at the bottom of the furnace when the fire cooled. With open-hearth technology, rather than collecting a 'lump' or 'bloom,' at the end of the process liquid steel poured from spouts into ladles on a pouring floor, where ingots were cast. While Bessemer converters had been capable of 10-ton charges, open-hearth furnaces were capable of charges as high as 350 tons. In addition, the ability to add alloying materials and to take samples for laboratory testing at any time during the process enabled the production of finely tuned steels.


In 1901, on the cusp of the automobile's arrival on the American scene, Andrew Carnegie sold Carnegie Steel to J.P. Morgan, who consolidated 10 competing steel companies, Carnegie Steel being the largest, into United States Steel.


A Need for R&D

 By the 1920s the world needed more new types of steel for increasingly specialized applications with each passing year. U.S. Steel's President, Judge Elbert Gary, whom Morgan had installed at the time of the corporation's founding, saw that progress in the development of steel was stifled by a culture of manufacturing engineers solving technical problems in isolation and, at times, in secret - not unlike the culture of secrecy that had attended the iron and steel industry since its earliest days. For years Gary pressed his Board of Directors to formalize and consolidate the company's research efforts into a single department. In 1926, the Judge's vision prevailed when the board of directors resolved to found a research department.


One of the department's early stars was Edgar C. Bain, who presided over the integration of metallography, the study of microscopic images of metals, into the broader discipline of metallurgy, the macro-scale chemical and physical study of metals. In his years in the department, Bain employed X-ray diffraction and other advanced analytical methods to investigate such fundamental phenomena as the microscopic granular and crystallographic properties of steel as they related to performance characteristics.


To explain what Bain was investigating: At the microscopic level, and working from the bottom up: pure iron is made up of iron atoms aligned in cubic crystals which, in their simplest configuration, have one atom at each corner of the cube and one in the middle of every face, sort of like dice with fives on all sides. One set of 14 atoms arranged this way is called a unit cell. A stack of unit cells is called a lattice array.


While transforming from liquid to solid phase, the crystals grow by adopting atoms as they cool, extending the lattice until one array bumps into a neighbor, at which point, growth stops and a grain is formed. The combined crystalline and granular structure of a grain is characterized as a 'phase.' In principle, steel follows the same progression as for iron, except that carbon and other alloying atoms join the iron atoms, either as substitute atoms within the lattice or squeezed in as extras. In either case, because the elements differ in their crystal spacing preferences, the alloying atoms create deformities in the lattice, which tends to change the properties of the metal. Frequently, because a section of the lattice is 'displaced' or 'bent,' the metal becomes stronger, similar to the way an arch is stronger than a straight span.


With the help of X-ray diffraction, Bain began a tradition of correlating the effects of variables such as chemical composition, thermal cycling, rolling, quenching and continuous cooling with the crystalline and granular properties of various steel phases which, in turn, correlate with performance characteristics, such as strength, hardness, brittleness, elasticity, ductility, weldability and corrosion resistance.


One of Bain's most significant accomplishments was the discovery of a new crystalline phase for steel that came to be known as Bainite, a tough steel produced by the precise thermal cycling between two crystalline phases. Continuing the R&D Tradition Following in Bain's footsteps, today, U. S. Steel's laboratory researchers use miniature furnaces, pilot mills, scanning electron microscopes and other advanced instruments, all equipped with advanced feedback and control systems, for the exact formulation, bench-scale production, nanoscale observation and precision testing of a wide range of steel alloys, including multi-phase steels, which exploit the microstructural characteristics of various crystal phases and 'blend' them for optimal performance.


Throughout the 20th century, researchers at U. S. Steel made regular product improvements in response to an expanding industrialized economy and emerging social needs, including sheet steel for the first automotive vehicles; electroplated steel for tin cans; crack-resistant steel for the Liberty and Victory ships of World War II; high fracture-toughness steel for oil and gas pipelines in Arctic and desert environments; and corrosion-resistant steel for longer lasting automobile bodies.


Beginning in the 1950s, the Basic Oxygen Process (BOP) came onto the scene as the most advanced steel making technology. This method improved both the Bessemer and open-hearth processes by injecting pure oxygen, rather than nitrogen-containing air, into the melt. Because nitrogen tends to make steel brittle, and air contains about 78 percent nitrogen, eliminating nitrogen from the injected gas naturally made the resultant steel less brittle.


In keeping with Andrew Carnegie's tradition of adopting new technology and in the tradition of Bain's metallographic approach to metallurgy, in 1967, U. S. Steel became the proud owner of the first one-million-volt electron microscope in North America. The instrument, which was used to examine NASA's first moon rocks, was sufficiently large and powerful to require its own building with a special system to prevent lightning-like discharges from striking the Earth.


According to U. S. Steel's Harnack, today, researchers at the company are focused on high-strength, light-weight steels for more efficient automobiles; industrial pipe for use in hostile, down-hole environments, such as oil and gas exploration; laminated steels that incorporate non-metallic, polymer materials, for vibration damping; and dual and triple phase steels that use multiple alloy metals in exact chemical formulations processed under precisely timed temperature cycles and closely controlled atmospheric conditions to mix different phases both within the mass and on the surface of steel products. These new steels have heretofore unavailable performance and aesthetic characteristics, including corrosion and dent resistance, surface integrated color and reflection properties, bake hardenability, superior strength, impact resistance, easy formability and light weight.


Of the 40-odd grades of steel that U. S. Steel produces today, 15 were not available 10 years ago. Twelve new grades are under development. Over the past 30 years, researchers at U. S. Steel have been awarded more than 500 patents. On average, that's one every three weeks. A new, more efficient facility is sure to inspire a continuation of that prolific performance. Not that the rest of us are likely to take much notice. With so much steel, in so many places, doing such a good job, it's easy to take it for granted.


This story originally appeared as a TEQ cover story.

©Copyright 2006 Thomas P. Imerito/ dba Science Communications


Bookmark and Share

 
©2009 Science Communications
thomas@science-communications.com