MSE 131 Lecture Notes - Steel

 Overview Steel is an alloy of iron and carbon, or of iron, carbon and other alloying element. One classical definition is that steels are iron-carbon alloys with up to 1.5 percent carbon by weight; alloys with higher carbon content than this are known as...

 Overview Steel is an alloy of iron and carbon, or of iron, carbon and other alloying element. One classical definition is that steels are iron-carbon alloys with up to 1.5 percent carbon by weight; alloys with higher carbon content than this are known as cast iron. Steel Structures/Allotropes Iron-carbon phase diagram, showing the conditions necessary to form different phases. Steel Structures/Allotropes FERRITE (Pure Iron) At room temperature, the most stable form of iron is the body-centered cubic structure FERRITE or α-iron, a fairly soft and ductile metallic material that can dissolve only a small concentration of carbon (no more than 0.021 wt% at 910 °C). Steel Structures/Allotropes AUSTENITE Face-centered cubic configuration, called AUSTENITE or γ-iron, which is similarly soft and metallic but can dissolve considerably more carbon (as much as 2.04 wt% carbon at 1146 °C). Steel Structures/Allotropes CEMENTITE Cementite is a stochiometric phase with the chemical formula of Fe3C. Non ductile and very hard Cementite forms in regions of higher carbon content while other areas revert to ferrite around it. Steel Structures/Allotropes PEARLITE º BAINITE Has a laminar structure of alternate layers of ferrite and cementite. Carbon content: 0.83 % by weight < 0.83 % Carbon ➔ mixture of grains of ferrite and pearlite > 0.83 % Carbon ➔ mixture of grains of pearlite and cementite = 0.83 % Carbon ➔ wholly pearlite composition “ eutectoid “ structure. Steel Structures/Allotropes MARTENSITE Perhaps the most important allotrope is MARTENSITE, a chemically metastable substance with about four to five times the strength of ferrite. Martensite has a very similar unit cell structure to austenite, and identical chemical composition.  Other materials are often added to the iron-carbon mixture to tailor the resulting properties. Nickel and manganese in steel add to its tensile strength and make austenite more chemically stable, chromium increases the hardness and melting temperature, and vanadium also increases the hardness while reducing the effects of metal fatigue Large amounts of chromium and nickel (often 18 and 8 %, respectively) are added to stainless steel so that a hard oxide forms on the metal surface to inhibit corrosion. Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel. On the other hand sulfur, nitrogen, and phosphorus make steel more brittle, so these commonly found elements must be removed from the ore during processing.  Production Methods Iron ore pellets for the production of steel. Production Methods ▪CRUCIBLE TECHNIQUE or PUDDLING The original steel making technique, developed in India, used in the Middle East as Damascus steel and independently redeveloped in Sheffield by Benjamin Huntsman in 1740, and Pavel Anosov in Russia in 1837. ▪BESSEMER PROCESS The first commercial-scale steel production process ▪OPEN-HEARTH FURNACE ▪BASIC OXYGEN FURNACE This process uses 25%-35% old steel tomake new. It produces products such as automotive fenders, encasements of refrigerators, and for packaging. ▪ELECTRIC ARC FURNACE A form of secondary steelmaking from scrap, though the process can also use direct-reduced iron. The process uses virtually 100% old steel to make new. This process uses 25-35 percent old steel tomake new. It produces products such as structural beams, steel plates, and reinforcement bars—whose major required characteristic is strength. Types of Steel ▪CARBON STEEL ▪DAMASCUS STEEL ▪TOOL STEELS ▪HSLA (High Strength, Low Alloy) STEELS ▪ADVANCED HIGH STRENGTH STEELS ▪FERROUS SUPERALLOYS ▪STAINLESS STEELS STEEL Products STEEL Products  TRADITIONAL & RECENT APPLICATIONS STEEL in your Life  STEEL “The Household Choice” Building Homes to Last Steel is playing a more and more important role in the homebuilding industry.  STEEL “The Household Choice” Secure Your Family with Steel Doors Renovation spending has risen exponentially in recent years. With so much emphasis being placed on the home, consumers are constantly looking for new materials to enhance their new homes and for remodeling projects.  STEEL “The Household Choice” Appliances By weight, the typical appliance consists of approximately 75 percent steel. The steel used in appliances is made with a minimum of 25 percent recycled steel. Internal steel components may be made using either 25 percent or virtually 100 percent recycled steel. All appliances are recyclable when they have reached the end of their useful lives. Steel is the engine that drives appliance recycling.  STEEL “The Household Choice” The New Steel… Keeping Food Fresh Food in steel cans is preservative-free because the canning process preserves the food naturally. And since the food is heat-sterilized after being vacuum-sealed in a steel can, it is protected from contamination.  STEEL in your Car Steel Provides Ultimate Protection on the Road A steel safety cage absorbs the energy created in a crash by bending without breaking. Because steel is strong, and gets stronger as it bends, it reduces the chance of intrusion into the passenger compartment, better protecting you and your family. The safety cage also helps prevent problems that occur as the result of a crash, such as another collision, rollover of the vehicle or a fire. A steel roof protects passengers by helping the vehicle remain structurally sound if it rolls over in an accident. The seat structures and instrument panel of a car are made from steel for added safety and protection of the occupant. Seat tracks are made of steel to minimize the risk of a passenger being injured during a car crash because the seat assemblies were pulled off the tracks. In addition to a steel buckle, steel parts anchor seat belts. This helps ensure that passengers stay safely secured in their seats throughout a crash. A steel beam is placed inside the doors to help absorb the energy of a side-impact collision. Steel door latches help keep the doors closed during a crash, enhancing the strength of the safety cage. Steel bumpers absorb energy during a crash and minimize damage during low-speed impacts. Steel fuel tank systems meet a 15-year or better life requirement against different types of corrosion. In addition to being number one in safety, steel is the environmental leader among automotive materials. Virtually 100 percent of the steel used in an automobile can be recycled. And recycled steel is used to make more cars, as well as bridges, food cans, construction beams and many other steel products. STEEL for Construction / Infrastructure BRIDGES Structural Advantages: high strength, durability, and light weight, lighter foundations and lower erection costs, durability, ease of maintenance and ease of construction **HIGH PERFORMANCE STEEL provided up to 18% cost savings and up to 28% weight savings when compared with traditional steel bridge design materials. STEEL for Construction / Infrastructure UTILITY POLES Structural Advantages: strong and durable impervious to insect and rot 100% recyclable at the end of their long service lives do not need toxic chemical preservatives to prevent corrosion, can be galvanized or manufactured with weathering steel lightweight and easy to install, require less maintenance, and offer lower overall life cycle cost. STEEL for Construction / Infrastructure FRAMING Structural Advantages: high strength, durability, and light weight, lighter foundations and lower erection costs, durability, ease of maintenance and ease of construction Structural Advantages: *durability * resistance to fire, insect damage and extreme weather conditions * long-term cost effectiveness. STEEL for Construction / Infrastructure ROOFING Structural Advantages: It fulfills the building owner's need for durable, puncture-resistant protection against the weather, fire, wind and insects STEEL for Construction / Infrastructure PIPES AND TANKS Structural Advantages: With considerable and ongoing improvements in the quality of mill steel, fabrication technology, welding, linings, coatings, and cathodic protection, the combination of steel's strength, performance, and durability remains unparalleled. Steel also makes sense as the material of choice for above- ground water storage tanks. Steel fuel storage tanks (both above-ground and below- ground) have lower initial and life cycle costs than other materials, meet zero leakage tolerance standards, are safe in the face of extreme weather conditions or natural disasters (including earthquakes, tornados, mud slides and extreme temperature changes), and are recyclable. STEEL for Construction / Infrastructure CORRUGATED STEEL PIPES Structural Advantages: It is among the top-rated products for infrastructure because it withstands the stress of heavy traffic and unstable foundations better than most construction materials. In drainage systems, CSP provides years of durability, making it the material of choice for culverts, storm sewers, spillways, subdrains, underpasses, conveyer conduits, service tunnels, detention chambers and recharge systems. The strength and integrity of soil/steel structures are almost unlimited. STEEL for Construction / Infrastructure CORRUGATED STEEL PIPES Structural Advantages: Corrugated steel pipe is available in various shapes and sizes to meet several kinds of drainage, sewer and transportation needs. It can be fabricated to exact specifications. Research shows that CSP generally provides outstanding soil side durability. With proper coating and/or invert paving, CSP can provide a service life of 50-100 years for a wide range of environments and applications. Maintenance costs can be effectively controlled through modern structural and durability design criteria. STEEL in Automotive Industry  STEEL in Automotive Industry Fierce competitors joined together in a common purpose: a lightweight steel auto body structure that outperforms benchmarked averages and can also cost less to build. ULSAB-Advanced Vehicle Concepts (ULSAB-AVC) UltraLight Steel Auto Body (ULSAB)  STEEL in Automotive Industry UltraLight Steel Auto Closure (ULSAC) A study undertaken by the global steel industry to demonstrate the effective use of steel in producing lightweight, structurally sound, steel automotive closure panels that are manufacturable and affordable. STEEL in Automotive Industry A showcase for the best automotive design technology that can be brought to bear on today's highly complex technical challenges - a primer on understanding and exploiting the properties of steel as they apply to automotive suspensions. UltraLight Steel Auto Suspensions (ULSAS)  STEEL in Automotive Industry Light Truck Structure (LTS) A study that was undertaken to demonstrate ways to optimize steel in automotive manufacturing, while cutting costs, reducing weight, creating manufacturing efficiencies and improving performance and safety. STEEL in Automotive Industry Vehicle crashworthiness as measured in standardized crash tests is currently ranked at equal level to quality, styling, ride and handling, and fuel economy. Auto manufacturers, government agencies, insurance underwriters, and the news media provide consumers with assessments of automotive safety. Safety features such as energy absorbing front and side structures, air bags, seats with integrated seat belts, and various crash avoidance devices are just some of the safety features offered as standard equipment on many vehicles. Future safety devices may include “smart” safety devices that would protect occupants based on age, gender, location in the vehicle, and crash severity. The focus on vehicle safety, meaning structural crashworthiness and reduction in occupant fatalities and harm, will undoubtedly continue to sharpen during the next decades in response to consumer demands, increasing government regulation and globalization of the industry. ULSAB, ULSAC, ULSAB-AVC, ULSAC  The steel industry has a standing commitment to sustainability, which is backed by significant investment in new technologies to improve energy efficiency, reduce carbon emissions and greenhouse gas emissions through recycling and process innovation, developing green building guidelines for construction and heighten productivity..  Quiz 2 Complete the table: MATERIAL PROPERTIES PROCESS PRODUCT Concrete for roads Concrete for buildings Steel for roofing Steel for pipes Steel for automotive