Carbon steel

Properties and Characteristics of Carbon Steel
– Carbon steel is divided into low-carbon steel and high-carbon steel.
– Other elements such as manganese, phosphorus, sulfur, and silicon can affect the properties of carbon steel.
– Carbon steel can be easily machined, welded, and heat treated to improve its strength and durability.
– It is susceptible to rust and corrosion, but can be protected with coatings or made from stainless steel alloy.
– Carbon steel is environmentally friendly, as it is recyclable and energy-efficient to produce.
– Mild or low-carbon steel is the most common form of steel due to its affordability and acceptable material properties.
– It contains approximately 0.05-0.30% carbon, making it malleable and ductile.
– Low-carbon steels are easier to handle and cold-form, commonly used in car parts, pipes, construction, and food cans.
– High-tensile steels have additional alloying ingredients to increase strength and wear properties.
– Higher-carbon steels (0.30-1.70% carbon) can undergo heat treatment and may contain trace impurities that affect their quality.
– Carbon steel is classified into four classes based on carbon content: low-carbon, medium-carbon, high-carbon, and ultra-high-carbon steel.
– Low-carbon steel has 0.05-0.15% carbon content.
– Medium-carbon steel has approximately 0.3-0.5% carbon content, balancing ductility and strength.
– High-carbon steel has 0.6-1.0% carbon content, known for its strength and use in springs, tools, and high-strength wires.
– Ultra-high-carbon steel has 1.25-2.0% carbon content, used for special purposes like knives and axles.
– Heat treatment of carbon steel aims to change its mechanical properties, such as ductility, hardness, yield strength, or impact resistance.
– Electrical and thermal conductivity are minimally affected by heat treatment.
– Young’s modulus (elasticity) remains unaffected.
– Heat treatment involves altering the solubility of carbon in the austenite phase of iron.
– Different heat treatment techniques trade ductility for increased strength or vice versa.
– Carbon steel has various applications, including milling machines, cutting tools, knife-making, and high-strength wires.
– It is commonly used in the spring industry, farm industry, and for a wide range of high-strength wires.
– Carbon steel is used in car parts, pipes, construction, and food cans.
– It is also used for special purposes such as non-industrial knives, axles, and punches.
– The affordability and versatility of carbon steel make it a popular choice in many industries.

Heat Treatment Methods for Carbon Steel
– Spheroidizing: Forms spheroidite by heating carbon steel to approximately 700°C (1,300°F) for over 30 hours.
– Full annealing: Heats carbon steel to approximately 400°C (750°F) for 1 hour and then cools slowly.
– Process annealing: Relieves stress in cold-worked carbon steel by heating it to 550-700°C (1,000-1,300°F) for 1 hour.
– Isothermal annealing: Heats hypoeutectoid steel above the upper critical temperature, maintains it, and then cools to room temperature.
– Normalizing: Heats carbon steel to approximately 550°C (1,000°F) for 1 hour and then air-cools.
– Quenching: Rapidly cools carbon steel with at least 0.4 wt% C in water, brine, or oil to the critical temperature.
– Martempering: Applied after quenching, relieves residual stresses and may form bainite.
– Quenched steel: Extremely hard but brittle, with internal stresses that may cause surface cracks.
– Martempered steel: Increased ductility and impact resistance compared to quenched steel.
– Tempering: Reheats quenched steel to a temperature below the eutectoid temperature and then cools, restoring ductility but reducing hardness.
– Austempering: Interrupts the quench and holds carbon steel in a molten salt bath at temperatures between 205 and 540°C (400 and 1,000°F).
– Bainite: Resulting steel from austempering, with acicular microstructure, high strength, greater ductility, and less distortion than martensite steel.
– Advantage of austempering: Increased impact resistance and minimal loss in strength.
– Disadvantage of austempering: Limited applicability and requires a special salt bath.
– Difference between austempering and martempering: Austempering produces bainite, while martempering produces martensite.
– Case hardening: Hardens only the exterior of the steel part, creating a wear-resistant skin while preserving a tough and ductile interior.
– Carbon steels: Not very hardenable throughout thick sections, making case hardening beneficial.
– Alloy steels: Have better hardenability and can be through-hardened without requiring case hardening.
– Surface characteristics: Case hardening provides good wear characteristics, while the core remains flexible and shock-absorbing.
– Benefits of case hardening: Increased surface hardness and wear resistance.

Influence of Carbide Morphology and Microstructure on Decarburization
– Alvarenga et al. (2014) studied the influence of carbide morphology and microstructure on the kinetics of superficial decarburization in C-Mn steels.
– The research was published in the Metallurgical and Materials Transactions A journal.
– The authors found that carbide morphology and microstructure significantly affect the decarburization process.
– Decarburization refers to the loss of carbon from the surface of steel due to oxidation.
– Understanding the factors influencing decarburization is crucial for controlling the surface properties of carbon steel.

Additional Resources on Carbon Steel
– Wikimedia Commons has a collection Source:  https://en.wikipedia.org/wiki/Carbon_steel