Steelmaking Process Finals Reviewer PDF

**FINALS REVIEWER** **STEELMAKING PROCESS** In steelmaking, the key element is iron. To produce pure iron (which is called *pig iron* or *molten iron*) from the iron ore, in a blast furnace at [2000℃]{.math.inline}, **iron ore**, **coking coal**, and **limestone** are mixed. Diagram of a blast fu...

**FINALS REVIEWER** **STEELMAKING PROCESS** In steelmaking, the key element is iron. To produce pure iron (which is called *pig iron* or *molten iron*) from the iron ore, in a blast furnace at [2000℃]{.math.inline}, **iron ore**, **coking coal**, and **limestone** are mixed. Diagram of a blast furnace Description automatically generated Chemical reactions inside the blast furnace: 1. Hot air containing oxygen gas reacts with some coke producing carbon dioxide. \ [*C*(*s*) + *O*~2~(*g*) → *CO*~2~(*g*)]{.math.display}\ 2. The produced carbon dioxide from \#1 reacts with the remaining coke and produces carbon monoxide. \ [*CO*~2~(*g*) + *C*(*s*) → 2*CO*(*g*)]{.math.display}\ 3. The carbon monoxide produced from \#2 reacts with the iron ore (hematite or ferric oxide) to form pure iron in liquid form (molten iron or pig iron) and carbon dioxide \ [3*CO*(*g*) + *Fe*~2~*O*~3~(*s*) → 2*Fe*(*l*) + 3*CO*~2~(*g*)]{.math.display}\ 4. Limestone (also known as calcium carbonate) decomposes to Calcium Oxide and Carbon Dioxide. \ [CaC*O*~3~(*s*) → *CaO*(*s*) + *CO*~2~(*g*)]{.math.display}\ 5. The Calcium oxide produced in \#4 combines with Silicon dioxide (sand) to form Calcium metasilicate (slag). \ [CaO(*s*) + *SiO*~2~(*s*) → *CaSiO*~3~(*l*)]{.math.display}\ **STEEL REFINING PROCESSES** 1. **Basic Oxygen Furnace (BOF) --** this removes excess carbon using oxygen (oxidation) to refine molten iron. 2. **Electric Arc Furnace (EAF)-** this is usually used for recycling. Scrap metals are melted using electric arcs. **Secondary Refining Techniques:** 1. **Ladle Refining --** After the primary treatment process, molten steel is refined in a ladle furnace to adjust its chemical composition (carbon, sulfur, phosphorus, oxygen, etc.) and add alloying elements (chromium, manganese, and nickel). **Problematic Elements** +-----------------------------------+-----------------------------------+ | **DETRIMENTAL ELEMENTS** | **EFFECT** | +===================================+===================================+ | Sulfur | It contributes to "hot shortness" | | | or brittleness at elevated | | | temperatures, which makes the | | | forging or welding process | | | problematic. | +-----------------------------------+-----------------------------------+ | Phosphorus | It causes "cold shortness" or | | | brittleness at low temperatures | | | and reduces toughness | +-----------------------------------+-----------------------------------+ | Carbon (\> 2% for cast iron) | Causes brittleness, reduced | | | weldability, difficult | | (\> 0.8% for High carbon steel) | machinability | +-----------------------------------+-----------------------------------+ | Oxygen | Reduced strength and toughness, | | | cause poor surface finish (scale | | | or rust), increased porosity, and | | | casting defects | +-----------------------------------+-----------------------------------+ **Effects of Alloying Elements to Steel's Properties** +-----------------------------------+-----------------------------------+ | **ELEMENT** | **EFFECT** | +===================================+===================================+ | Carbon | Increase hardness and strength | +-----------------------------------+-----------------------------------+ | Manganese | Improves toughness | +-----------------------------------+-----------------------------------+ | Chromium | Adds corrosion resistance | +-----------------------------------+-----------------------------------+ | Nickel | Enhances strength and ductility | | | | | | Adds corrosion resistance | +-----------------------------------+-----------------------------------+ 2. **Casting Techniques -** While primary refining typically occurs in the furnace, some casting techniques incorporate steps that enhance the quality of the final product by removing impurities and improving the material's properties. **Examples:** - **Continuous Casting with Electromagnetic Stirring --** this reduces segregation and enhances homogeneity. - **Filtered Casting System --** this removes particulates and ensures a cleaner melt. **Hot and Cold Rolling** - **HOT ROLLING -** The cast material is reheated above its recrystallization temperature and passed through rollers to reduce thickness or alter the shape. This *shapes* and *toughens* the steel. - **COLD ROLLING --** This process is optional. The hot-rolled product is cooled to room temperature and then cold-rolled. This refines thickness, improves surface quality, and increases strength via strain hardening. **HEAT TREATMENT PROCESSES** **Stress relief treatment** involves heating the metal to a *sub-critical temperature*, below its recrystallization point, and then cooling it slowly. This process is used to relieve residual stresses, improve dimensional stability, and reduce distortion during machining. It is commonly applied to metals such as steel, cast iron, aluminum, and copper alloys. **Annealing** is performed by heating the metal to a specific temperature, holding it at that temperature, and then cooling it *slowly*, often in a furnace. This process softens the metal, enhances its ductility, refines its grain structure, and relieves internal stresses. It is widely used for materials like steel, aluminum, copper, brass, and other alloys. **Hardening** requires heating the metal to a *high* temperature, often to achieve austenitization in steel, followed by *rapid* cooling through quenching. This increases the hardness and strength of the metal but reduces its ductility. Hardening is typically applied to carbon steel, alloy steel, and tool steel. **Tempering** involves reheating a previously hardened metal to a *lower* temperature and then allowing it to cool, usually in the *air*. This process reduces brittleness, improves toughness, and creates a balance between hardness and ductility. Tempering is most often used on hardened steel, alloy steel, and tool steel. **Quenching** consists of rapidly cooling a metal, usually in water, oil, or air, after it has been heated to a high temperature. This locks in a hard microstructure, such as martensite in steel, which increases hardness but can also introduce residual stresses. Metals like carbon steel, alloy steel, and aluminum alloys commonly undergo quenching. **Normalizing** involves heating the metal above its critical temperature, holding it there, and then cooling it in air at room temperature. This process refines the grain structure, enhances mechanical properties, and reduces internal stresses. Normalizing is frequently used for carbon steel, alloy steel, and cast iron. **NON-FERROUS METALS AND ALLOYS** Non-ferrous alloys are metal combinations that do not contain significant amounts of iron. These alloys are widely used in marine engineering due to their unique properties, including corrosion resistance, lightweight nature, and strength. *Common Non-Ferrous Alloys in Marine Applications* 1. **Aluminum-Magnesium Alloys** - **Key Properties**: - High corrosion resistance, especially in saltwater environments. - Lightweight, reducing overall weight in marine structures. - Good weldability, making it ideal for shipbuilding. - **Common Applications**: - Ship hulls and superstructures. - Decks and gangways. 2. **Copper-Nickel Alloys** - **Key Properties**: - Exceptional corrosion resistance, particularly in seawater. - High thermal conductivity, useful in heat exchangers. - Biofouling resistance, preventing marine organism buildup. - **Common Applications**: - Heat exchangers, condensers, and piping systems. - Desalination plant components. 3. **Bronze (Copper-Tin Alloy)** - **Key Properties**: - High strength and wear resistance. - Good corrosion resistance in marine environments. - Excellent machinability. - **Common Applications**: - Propeller blades. - Bearings, pumps, and valves in marine systems. 4. **Titanium Alloys** - **Key Properties**: - Exceptional corrosion resistance, even in extreme saltwater exposure. - High strength-to-weight ratio, ideal for lightweight structures. - Resistance to biofouling and erosion. - **Common Applications**: - Masts for sailing vessels. - Marine platforms and critical components exposed to severe marine environments. **Things to Consider in Selecting an Alloy for Marine Applications:** When selecting an alloy for a specific marine task, consider: 1. **Corrosion Resistance**: Essential for prolonged exposure to saltwater. 2. **Weight**: Lightweight materials improve fuel efficiency and design flexibility. 3. **Strength**: Ensure the alloy can withstand mechanical stresses and loads. 4. **Thermal Conductivity**: Important for components like heat exchangers. 5. **Durability**: Resistance to wear, biofouling, and environmental damage. **PLASTICS, RUBBERS, AND COMPOSITES IN MARINE APPLICATIONS** Engineering materials used in marine environments must withstand harsh conditions, including saltwater corrosion, mechanical stress, UV radiation, and extreme temperatures. Plastics, rubbers, and composites are often chosen for their unique properties and advantages over traditional materials like metals. **PLASTICS** Plastics are lightweight, corrosion-resistant, and versatile, making them ideal for various marine applications. **Types of Plastics Commonly Used**: 1. **Polyethylene Terephthalate (PET)**: Known for durability and resistance to chemicals. 2. **Polyvinyl Chloride (PVC)**: Used for pipes and coatings due to its corrosion resistance. 3. **Polytetrafluoroethylene (PTFE)**: Also known as Teflon, it offers excellent low-friction and chemical resistance. 4. **Polypropylene (PP)**: Lightweight and resistant to water absorption and fatigue. **Advantages of Plastics**: - Lightweight reduces fuel consumption. - Resistant to corrosion and chemicals. - Easy to shape and fabricate. **Disadvantages**: - Susceptible to UV degradation and mechanical wear. - Solutions: Use UV-resistant coatings or additives to enhance durability. **RUBBERS** Rubbers (elastomers) are valued for their flexibility, durability, and resistance to harsh marine conditions. **Common Types of Marine Rubbers**: 1. **Natural Rubber**: Good elasticity but poor resistance to saltwater and UV. 2. **Neoprene Rubber**: Ideal for marine applications due to its resistance to UV, oil, and saltwater. 3. **Silicone Rubber**: Withstands extreme temperatures but has moderate strength. 4. **Styrene-Butadiene Rubber (SBR)**: Economical but less resistant to environmental conditions. **Key Properties for Marine Use**: - **Saltwater Resistance**: Prevents degradation in corrosive environments. - **UV and Ozone Resistance**: Protects seals and gaskets exposed to sunlight and weather. **COMPOSITES** Composites combine a matrix material (e.g., epoxy resin) with reinforcements (e.g., glass or carbon fibers) to achieve superior performance. **Common Marine Composites**: 1. **Glass-Reinforced Plastics (GRP)**: Lightweight and corrosion-resistant, used for hulls and decks. 2. **Carbon Fiber Composites**: High strength-to-weight ratio, ideal for high-performance vessel components. 3. **Epoxy Resin Composites**: Used for adhesives and laminates due to excellent bonding properties. **Advantages of Composites**: 1. High strength-to-weight ratio. 2. Excellent corrosion and fatigue resistance. 3. Tailorable properties for specific applications. **Typical Layers in Fiber-Reinforced Composites**: 1. **Fibers (Reinforcement)**: Provide strength and stiffness (e.g., glass, carbon, or Kevlar). 2. **Matrix (Binder)**: Holds fibers together and transfers load (e.g., epoxy resin). 3. **Surface Coating**: Protects the composite from environmental damage. **Applications of Plastics, Rubbers, and Composites in Marine Engineering** 1. **Plastics**: Pipes, coatings, bearings, and lightweight components. 2. **Rubbers**: Gaskets, seals, and flexible connectors. 3. **Composites**: Hull structures, masts, and high-performance vessel parts. **ADHESIVES** Adhesives are substances used to bond two or more surfaces together. In engineering, especially in marine applications, adhesives provide lightweight, durable, and seamless alternatives to mechanical fasteners like screws or bolts. They play a vital role in maintaining structural integrity and preventing water ingress in harsh environments. **Types of Adhesives:** 1. **Epoxy** - Often comes as two components (resin and hardener) that must be mixed before application. It is high strength, chemical resistance, and water resistance. - **Applications:** Repairing damaged metal or fiberglass components and bonding structural materials in boats and ships. 2. **Polyurethane** - Flexible, waterproof, and resistant to environmental conditions like UV light and saltwater. - **Applications:** Sealing decks and hull seams, bonding wood to metal or other materials. 3. **Cyanoacrylate (Super Glue)** - Quick-setting and effective for small, precise applications. - **Applications:** Sealing small cracks in plastics or ceramics, quick repairs on minor components. 4. **Silicone Adhesives:** - Elastic, waterproof, and suitable for sealing applications. - **Applications:** Sealing portholes, deck fittings, and preventing water ingress in joints. 5. **Contact Adhesives** - Requires coating on both surfaces and drying before joining. It bonds immediately upon contact. - **Applications:** Bonding rubber, laminates, and insulation materials. Surface Preparation for Adhesive Use These are the step-by-step instructions for surface preparation: 1. **Clean the Surface:** Remove dirt, grease, oil, and contaminants using a degreaser or solvent. 2. **Dry the Surface:** Ensure it is completely moisture-free to prevent adhesion failure. 3. **Roughen the Surface:** Use sandpaper or abrasive tools to create a textured surface, improving adhesive grip. 4. **Verify Compatibility:** Check that the adhesive is suitable for the materials being joined. 5. **Apply in Proper Conditions:** Ensure the application environment is within the recommended temperature and humidity range for the adhesive. *Why is surface preparation important?* - Ensures maximum adhesive performance. - Prevents premature bond failure caused by contaminants or insufficient bonding area. - Increases bond longevity in challenging marine environments. **Advantages and Limitations of Adhesives in Marine Applications** *Advantages:* - Lightweight and reduces the need for heavy mechanical fasteners. - Provides a continuous seal, reducing water ingress points. - Distributes stress evenly across bonded surfaces. *Disadvantages:* - Requires meticulous surface preparation. - May degrade under extreme environmental conditions. - Limited shear strength in certain applications. **DESTRUCTIVE TESTING (DT)** Destructive Testing involves physically damaging or destroying a material or component to evaluate its properties, performance, and failure limits. It is used to determine mechanical properties such as strength, ductility, hardness, toughness, and fatigue. *Common Methods:* 1. **Tensile Testing** -- it measures a material\'s strength and elongation under tension. 2. **Hardness Testing** -- evaluates resistance to surface indentation (e.g., Brinell, Rockwell). 3. **Impact Testing** -- it assesses toughness and energy absorption under sudden force (e.g., Charpy test). 4. **Fatigue Testing** -- it determines resistance to cyclic loading. 5. **Bend Testing** -- it measures ductility and flexural strength. **NON-DESTRUCTIVE TESTING** Non-Destructive Testing examines the integrity and properties of a material or component without causing damage. It is used to detect surface and subsurface flaws or irregularities while preserving the item being tested**.** *Common Methods:* 1. **Ultrasonic Testing (UT)** -- this uses sound waves to detect internal flaws. 2. **Radiographic Testing (RT)** -- this uses X-rays or gamma rays to visualize internal structures. 3. **Magnetic Particle Testing (MT)** -- it detects surface and near-surface defects in ferromagnetic materials. 4. **Dye Penetrant Testing (PT)** -- it reveals surface cracks and defects by applying a dye and developer. 5. **Visual Testing (VT)** -- this method involves inspecting surface defects using the naked eye or magnifying tools.