NEWS&CASES
I. Diverse Types, Each with Its Own Strengths
Classified by Carbon Content
- Low-carbon steel plates (C≤0.25%): Characterized by low hardness, excellent ductility, and good weldability. They are commonly used in automobile body manufacturing; for example, about 60% of the components in a certain car brand's body are made of low-carbon steel plates, which not only meet lightweight requirements but also satisfy welding process needs. In the production of electronic device casings, due to their ease of processing and shaping to achieve complex designs, some of Apple's electronic product casings use low-carbon steel plates.
- Medium-carbon steel plates (C 0.25%-0.6%): They strike a balance between strength, plasticity, and toughness. After heat treatment, their comprehensive mechanical properties are enhanced, making them widely used in machinery manufacturing. For instance, over 70% of shaft parts are made of medium-carbon steel plates, which can withstand large torques and bending moments; about 50% of gears are made of medium-carbon steel plates, and after quenching and tempering, they meet the requirements for high wear resistance and strength.
- High-carbon steel plates (C>0.6%): They have extremely high hardness and strength but poor plasticity and toughness. In the tool manufacturing industry, such as in cemented carbide tools, high-carbon steel plates are used as the base material, accounting for about 30%. Their high hardness ensures that tools remain sharp for a long time; in stamping die manufacturing, about 40% of dies use high-carbon steel plates, which can withstand huge stamping pressure.
Classified by Thickness
- Thin carbon steel plates (0.2mm - 4mm): They are lightweight, have good surface quality, and high dimensional accuracy. In electronic device manufacturing, about 80% of mobile phone and tablet casings use thin carbon steel plates, which not only ensure an attractive appearance but also reduce product weight. In the food packaging industry, such as can production, over 90% use thin carbon steel plates, and their good surface quality ensures food hygiene.
- Medium-thickness carbon steel plates (4mm - 20mm): They have moderate strength and rigidity. In the construction industry, about 70% of the beams and columns in steel structure frames are made of medium-thickness carbon steel plates, which bear the main load of the building. In the machinery manufacturing field, about 60% of mechanical component casings and support structures use medium-thickness carbon steel plates to ensure stable operation of equipment.
- Thick carbon steel plates (20mm - 60mm): They have strong load-bearing capacity and deformation resistance. In pressure vessel manufacturing, over 95% use thick carbon steel plates to ensure safe operation in high-pressure and high-temperature environments. In the shipbuilding industry, about 80% of the hull structures of large ocean-going ships use thick carbon steel plates to resist seawater pressure and wind-wave impact.
- Extra-thick carbon steel plates (60mm +): They have extremely high strength and rigidity. In the construction of nuclear power plant containment structures, extra-thick carbon steel plates are key materials, accounting for over 90% to ensure the safety of nuclear power plants. In key structural components of large water conservancy project dams, about 70% use extra-thick carbon steel plates to ensure the long-term stability of the dams.
Classified by Rolling Method
- Hot-rolled carbon steel plates: Rolled at high temperatures, they have good comprehensive performance but with an oxide scale on the surface. In the construction field, hot-rolled carbon steel plates account for about 80% of the steel used in steel structure building frames, providing stable support for buildings. In the manufacturing of large mechanical bases, about 75% use hot-rolled carbon steel plates to ensure equipment stability.
- Cold-rolled carbon steel plates: Rolled at room temperature, they have a smooth surface, high dimensional accuracy, and relatively high strength and hardness. In automobile body panels, the application ratio of cold-rolled carbon steel plates exceeds 90%, ensuring the appearance and assembly accuracy of the car body. For home appliance casings, such as refrigerators and washing machines, about 85% use cold-rolled carbon steel plates, which are both attractive and strong.
II. Precision Manufacturing, Forging Quality
Iron Smelting
Iron ore is crushed and beneficiated as pre-treatment, then fed into the blast furnace together with coke and limestone. In the blast furnace, coke burns to provide heat, reducing iron from the iron ore. Limestone reacts with impurities to form slag, and finally, molten iron flows out from the bottom of the blast furnace. Take a large steel plant as an example; its daily molten iron output can reach tens of thousands of tons, providing sufficient raw materials for subsequent steelmaking.
Steelmaking
In converter steelmaking, molten iron is poured into the converter and oxygen is blown in. Oxygen reacts violently with impurities such as carbon, silicon, manganese, and phosphorus in the molten iron to reduce the carbon content, while releasing a large amount of heat to maintain a high temperature of about 1600°C. Slag-forming materials such as lime are added to remove phosphorus and sulfur impurities, and the chemical composition of the molten steel is precisely adjusted. This process can reduce the carbon content in molten steel from about 4% in molten iron to the target value, meeting the production requirements of different carbon steel plates.
Forming
- Continuous casting: Molten steel is poured into the mold through a tundish, and parameters such as temperature, casting speed, and cooling water volume are controlled to ensure the quality of the cast billet. The continuous casting production line of a certain steel enterprise can produce cast billets several meters long per minute, with high production efficiency and stable quality.
- Rolling: The cast billet is first heated to improve its plasticity, then rolled through multiple passes of rough rolling and finish rolling. By adjusting the roll spacing and speed, carbon steel plates of different specifications are produced. For example, to produce a carbon steel plate with a thickness of 10mm, it needs to go through multiple rolling passes to gradually reduce the thickness to the target.
Heat Treatment
- Quenching: Carbon steel plates are heated above the critical temperature to form austenite, then quickly cooled in a quenching medium to obtain martensite, significantly improving hardness and strength. For example, after quenching, the hardness of high-carbon steel plate tools can be increased to above HRC60.
- Tempering: Quenched carbon steel plates are heated to a temperature range below the critical temperature, held for a certain time, and then slowly cooled to eliminate internal stress and adjust the balance between hardness and toughness. Low-temperature tempering is used for tool steel to maintain high hardness; medium-temperature tempering improves the elastic limit of springs; high-temperature tempering enables mechanical parts to obtain good comprehensive performance.
- Normalizing: Heating to above the critical temperature and cooling in air, the structure is finer than that after quenching, with lower hardness and strength but better plasticity and toughness. It is often used to improve the machinability of low-carbon and medium-carbon steels.
Surface Treatment
- Galvanizing: Hot-dip galvanizing forms a metallurgical bond between the zinc layer and the carbon steel plate substrate. The zinc layer is thick and has strong corrosion resistance; over 80% of outdoor facilities in construction and electric power use hot-dip galvanized carbon steel plates. Electro-galvanizing has a thin layer and good surface quality; about 60% of auto parts use electro-galvanized carbon steel plates.
- Painting: The process is simple and low-cost; over 90% of building decorative panels are painted, which is both protective and aesthetic. Painting the surface of mechanical equipment can effectively extend the service life of the equipment.
- Electroplating: Using electrolysis to deposit a metal or alloy on the surface of carbon steel plates. For example, nickel-plated layers have good corrosion resistance and wear resistance, and about 70% of electronic device casings use nickel-plated carbon steel plates. Chromium-plated layers have a bright appearance and excellent corrosion resistance, and the chromium plating ratio of hardware products reaches more than 50%.
III. Wide Applications, Supporting Industries
Construction Field
In building structures, steel structure frames use a large amount of carbon steel plates. For example, in high-rise office buildings, about 80% of the steel beams and columns are made of carbon steel plates to support the building's main body. In bridge construction, about 90% of the main beams and piers of large bridges use carbon steel plates to ensure the load-bearing capacity and stability of the bridge. In terms of building envelope structures, thin carbon steel plates made of exterior wall decorative panels have a market share of over 70%, and medium-thick carbon steel plates are used for floors and roofs, accounting for about 60%.
Machinery Manufacturing Field
Carbon steel plates are indispensable in the manufacturing of mechanical parts; about 70% of gears, shafts, connecting rods, etc., are processed from carbon steel plates. For heavy machinery such as mining machinery and construction machinery, about 80% of key components such as excavator buckets and crane booms use carbon steel plates to withstand high impact loads and wear.
Automobile Manufacturing Field
About 60% of automobile body frames, doors, hoods, etc., use carbon steel plates. With the development of automobile lightweighting, some models use aluminum alloys and other materials, but carbon steel plates are still widely used in some components due to their cost advantages. In the chassis system, about 70% of key components such as suspension systems and drive shafts are made of carbon steel plates.
Shipbuilding Field
About 90% of structural components such as hull shells, decks, and bulkheads are made of carbon steel plates to withstand seawater corrosion and ship operating loads. About 80% of ship components such as anchor chains, rudders, and propellers use carbon steel plates.
Energy Field
In the oil and gas industry, about 85% of equipment such as pipelines, storage tanks, and pressure vessels use carbon steel plates to ensure safe operation in harsh environments. In the nuclear energy field, about 70% of some components of nuclear reactors use carbon steel plates with special properties to ensure the stability and safety of the equipment.