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1. Medium and thick plates refer to steel plates with a thickness of 4.5–25.0 mm; those with a thickness of 25.0–100.0 mm are classified as thick plates, while those with a thickness exceeding 100.0 mm are considered extra-thick plates. Uses: Medium and thick plates are primarily used in construction projects, machinery manufacturing, container production, shipbuilding, bridge construction, and more. It can also be used to manufacture various containers, furnace shells, furnace plates, bridges, as well as steel plates for automobiles – including plain steel plates and low-alloy steel plates – shipbuilding steel plates, boiler steel plates, pressure vessel steel plates, patterned steel plates, automobile frame steel plates, certain parts for tractors, and welded components. For professionals in the medium and heavy plate industry. Specific applications: Steel plates for bridges: Used in large railway bridges. They are required to withstand dynamic loads, impacts, vibrations, and corrosion resistance; examples include Q235q, Q345q, etc. Shipbuilding steel plates: Used for manufacturing the hulls of ocean-going and inland waterway vessels. It is required to have high strength, as well as good plasticity, toughness, cold bending properties, weldability, and corrosion resistance. Such as: A32, D32, A36, D36, etc. Boiler steel plates: Used in the manufacture of various boilers and their essential components. Since these steel plates operate under high pressure at moderate temperatures (below 350°C), they must not only withstand high pressures but also resist impacts, fatigue loads, as well as corrosion caused by water and gas. They require a certain level of strength, as well as good weldability and cold-forming properties; examples include Q245R. Steel plates for pressure vessels: These are primarily used in the manufacture of pressure vessels and other similar devices used in the petroleum and chemical industries for gas separation and gas storage and transportation. The operating pressure ranges from atmospheric pressure to 320 kg/cm2, or even up to 630 kg/cm2, while the temperature range is from -20 to 450°C. It is required that such vessel steel plates not only possess sufficient strength as well as good plasticity and toughness, but also excellent cold bending and welding properties. Examples of such materials include Q245R, Q345R, 14Cr1MoR, 15CrMoR, etc. Automobile chassis steel: Used for manufacturing automobile chassis (longitudinal beams and cross beams), it is low-alloy hot-rolled steel sheet with a thickness of 2.5–12.0 mm. Due to the complex shape of the automobile chassis, in addition to high strength and cold bending properties, good stamping properties are also required. 2. Deformed steel bar is the common name for hot-rolled ribbed rebar. The grade of ordinary hot-rolled steel bars is composed of HRB and the minimum yield strength of the grade. H, R, and B are respectively the first letters of the English words for Hotrolled, Ribbed, and Bars. Hot-rolled ribbed steel bars are divided into three grades: HRB335 (formerly designated as 20MnSi), HRB400 (formerly designated as 20MnSiV, 20MnSiNb, 20Mnti), and HRB500. The grade for fine-grained hot-rolled steel bars is the English abbreviation for hot-rolled ribbed steel bars followed by the initial letter of the word \"Fine\". Such as: HRBF335, HRBF400, HRBF500. For seismic structures with higher requirements, the applicable grades are: add E after the existing grade (for example: HRB400E, HRBF400E). Main uses: Widely used in civil engineering projects such as buildings, bridges, and roads. Main production areas: The manufacturers of rebar in China are primarily located in North China and Northeast China. In North China, companies such as Shougang, Tangsteel, Xuansteel, Chengsteel, Shanxi Zhongyang Steel Plant, and Baoding Puri Steel exist, while in Northeast China, firms like Xilin, Beitai, and Fugang are found. These two regions account for over 50% of the total rebar production in the country. The difference between deformed steel bars and plain round steel bars is that the former have longitudinal and transverse ribs on their surface, usually with two longitudinal ribs and transverse ribs distributed evenly along the length. Reinforcing steel bars belong to the category of small section steels and are primarily used as the framework for reinforced concrete building elements. It is required to have certain mechanical strength, bending deformation resistance, and weldability during use. The raw material billets used for producing deformed steel bars are carbon structural steel or low-alloy structural steel that has been treated through calm melting; the finished steel bars are delivered in a hot-rolled shape, after normalizing, or in their hot-rolled state. 3. Stainless steel sheets: They are divided into hot-rolled and cold-rolled types based on the manufacturing method, including thin sheets with a thickness of 0.5–4 millimeters and thick sheets with a thickness of 4.5–35 millimeters. Based on the structural characteristics of the steel grade, they are classified into 5 categories: austenitic, austenite-ferritic, ferritic, martensitic, and precipitation-hardening. Primary uses: It must be able to resist corrosion by various acids such as oxalic acid, sulfuric acid–ferric sulfate, nitric acid, nitric acid–hydrofluoric acid, sulfuric acid–copper sulfate, phosphoric acid, formic acid, and acetic acid. It is widely used in industries such as chemicals, food processing, pharmaceuticals, paper manufacturing, petroleum, and nuclear energy, as well as in various components for construction, kitchenware, tableware, vehicles, and household appliances. To ensure that the mechanical properties of various stainless steel sheets, such as yield strength, tensile strength, elongation, and hardness, meet the required standards, these sheets must undergo heat treatments such as annealing, solution treatment, and aging before being delivered. Stainless steel sheets have a smooth surface, high plasticity, toughness, and mechanical strength, as well as resistance to corrosion by acidic, alkaline gases, solutions, and other media. It is an alloy steel that is resistant to rusting, but not completely rust-proof. The corrosion resistance of stainless steel depends primarily on its alloying elements (chromium, nickel, titanium, silicon, aluminum, etc.) and its internal microstructure, with chromium playing a key role. Chromium possesses high chemical stability; it forms a passivation film on the surface of steel, isolating the metal from the outside environment and preventing the steel sheet from oxidizing, thereby enhancing its corrosion resistance. When the passivation film is damaged, the corrosion resistance decreases. 4. Steel strips with a width of 12–300 mm and a thickness of 4–60 mm, featuring a rectangular cross-section with slightly rounded edges. Primary uses: Flat steel can be used as finished steel products, as well as as raw material for welded pipes and as slab material for cold-rolled sheets. Primary uses: As a finished product, flat steel can be used to manufacture stirrups, tools, and mechanical parts; in construction, it is used as components in roof frame structures. 5. Steel with a square cross-section; it comes in hot-rolled and cold-rolled varieties ； Hot-rolled square steel with side lengths of 5–250 mm ； The side length of cold-drawn square steel ranges from 3 to 100 mm. Primary use: Rolling or processing into steel with a square cross-section. 6. Channel steel is a long strip of steel with a grooved cross-section. Its specifications are expressed in millimeters as waist height (h) * leg width (b) * waist thickness (d); for example, 120*53*5 means a channel steel with a waist height of 120 millimeters, a leg width of 53 millimeters, and a waist thickness of 5 millimeters, also known as 12# channel steel. For channel steels with the same waist height but different leg widths and waist thicknesses, letters a, b, c should be added to the right of the model to distinguish them, such as 25a#, 25b#, 25c#, etc. Channel steel is divided into ordinary channel steel and light channel steel. The specifications for hot-rolled ordinary channel steel are 5-40#. The specifications for the hot-rolled modified channel steels supplied by agreement between the supplier and the buyer are 6.5-30#. Channel steel is primarily used in building structures, vehicle manufacturing, and other industrial structures; it is also often used in combination with I-beams. Shape classification: Channel steel can be further divided into 4 types based on shape: cold-formed equal-leg channels, cold-formed unequal-leg channels, cold-formed channels with inward bends, and cold-formed channels with outward bends. 7. Angle steel, also known as angle iron, is a long strip of steel whose two sides are perpendicular to each other, forming an angular shape. There are equal-angle steel and unequal-angle steel. Equal-angle steel has two sides of equal width. Its specifications are expressed in millimeters as edge width × edge width × edge thickness. For example, “∠30×30×3” indicates an equilateral angle steel with a side width of 30 millimeters and a side thickness of 3 millimeters. It can also be indicated by a model number, which is the width in centimeters, such as ∠3#. The model number does not indicate the different sizes with varying edge thicknesses within the same model; therefore, it is necessary to specify the edge width and thickness of the angle steel in contracts and other documents, rather than relying solely on the model number. The specifications for hot-rolled equal-angle steel range from 2# to 20#. Primary uses: Angle steel can be used to form various load-bearing components according to different structural requirements, and it can also serve as connectors between components. It is widely used in various building and engineering structures, such as roof beams, bridges, transmission towers, lifting and transportation machinery, ships, industrial furnaces, reaction towers, container racks, and warehouse shelves. For those working with angle steel, it is a type of carbon structural steel used in construction; it is a steel product with a simple cross-section, primarily employed in metal components and the frameworks of buildings. It is required to have good weldability, plastic deformation capacity, and certain mechanical strength during use. The raw material billet for producing angle steel is low-carbon square billet, and the finished angle steel is delivered in hot-rolled formed, normalized, or hot-rolled condition. 8. Round steel refers to solid long bars of steel with a circular cross-section. Its specification is indicated by the diameter in millimeters; for example, “50” means a round steel bar with a diameter of 50 millimeters. Round steel is divided into three types: hot-rolled, forged, and cold-drawn. The specifications for hot-rolled round bars are 5.5–250 millimeters. Primary uses: Among them, the small round bars with a diameter of 5.5–25 millimeters are mostly supplied in straight bars bundled together, and are commonly used as rebar, bolts, and various mechanical parts ； Round bars larger than 25 millimeters are mainly used to manufacture mechanical parts or as billets for seamless steel pipes. Differences between round steel and other types of rebar: 1. The shape is different; round steel has a smooth surface without any grooves or ribs, while other types of rebar have grooves or ribs on their surface. This results in weaker adhesion between round steel and concrete, as compared to the stronger adhesion between other types of rebar and concrete. 2. The composition is different; round steel (grade 1 steel) belongs to ordinary low-carbon steel, whereas other types of rebar are usually alloy steel. 3. The strength is different as well. Round steel has lower strength, while other types of steel have higher strength. In other words, for rebars of the same diameter, round steel can withstand less tensile force than other types of rebar. However, round steel has greater plasticity – it can deform more before breaking, while other types of rebar deform much less before breaking. 9. Welded steel pipes: Also known as welded tubes, these are made by bending steel plates or strips and then welding them together. Based on the weld pattern, they are divided into straight-seam welded pipes and spiral-welded pipes. Based on their purpose, they are further divided into ordinary welded pipes, galvanized welded pipes, oxygen-blown welded pipes, wire sleeves, metric welded pipes, idler roller pipes, deep well pump pipes, pipes for use in automobiles, transformer pipes, thin-walled welded pipes, shaped welded pipes, and spiral welded pipes. Primary use: General welded pipes, which are used for transporting low-pressure fluids. Manufactured from Q195A, Q215A, and Q235A steel. It can also be manufactured from other soft steels that are easy to weld. Steel pipes are subject to tests such as hydrostatic pressure testing, bending tests, and flattening tests, and certain requirements are placed on their surface quality. The typical delivery length is 4–10 meters, with fixed lengths (or multiples thereof) usually being required for delivery. The specifications of welded pipes are expressed in nominal diameter (in millimeters or inches). The nominal diameter differs from the actual size. According to specified wall thicknesses, welded pipes come in two types: regular steel pipes and thick-walled steel pipes. Based on the end configuration, these pipes are further divided into threaded and unthreaded types. Table 6-17 shows the dimensions of welded pipes. 10. Galvanized steel sheet: It refers to a steel sheet with a layer of zinc coated on its surface. Galvanizing steel is a commonly used, economical, and effective method for corrosion prevention. Primary uses: Based on the production process, they can be divided into hot-dip galvanized sheets and electro-galvanized sheets; the former has a thicker zinc coating and is used for components that require high corrosion resistance ； The latter has a thinner and more uniform zinc coating, and is often used for painting or indoor items. 11. Square tube: As the name implies, it is a tubular shape with square dimensions. Many different materials can be used to create square tubes. Depending on their purpose and application areas, most square tubes are made of steel; they are often used in structural applications, for decoration, or in construction. A square tube is simply a type of tubular material with equal sides. It is formed by rolling steel strips through a specific processing procedure. Generally, the steel strip is first unpacked, leveled, curled, and welded to form a round tube; this round tube is then rolled into a square tube and cut to the desired length. Generally, it's 50 pieces per pack. 12. High-speed wire, a type of wire rod, usually referring to rod bars rolled using \"high-speed twist-free rolling mills\"; common examples include ordinary low-carbon steel twist-free controlled-cooling or hot-rolled rod bars (ZBH4403-88) as well as high-quality carbon steel twist-free controlled-cooling or hot-rolled rod bars (ZBH44002-88). The rolling speed for high-speed lines is 80–160 meters per second, with each rod’s weight (disk weight) ranging from 1.8 to 2.5 tons. The dimensional tolerance is very high, reaching 0.02 mm; during the rolling process, different requirements for the products can be met by adjusting the process parameters, especially those related to the cooling stage. 13. Spiral tube: Features of spiral tubes include a simple production process for straight-seam welded tubes, high production efficiency, low costs, and rapid development. The strength of spiral welded pipes is generally higher than that of straight-seam welded pipes. They allow for the production of pipes with larger diameters using narrower billets, and it is also possible to produce pipes with different diameters using billets of the same width. However, compared with straight-seam pipes of the same length, the weld length increases by 30–100%, and the production speed is lower. Therefore, welded pipes with smaller diameters are mostly welded using straight-seam welding, while those with larger diameters are mostly welded using spiral welding. Spiral pipes and their standard classifications: Spiral-welded submerged-arc welded steel pipes for transporting pressurized fluids (SY5036-83) are primarily used in pipelines for transporting oil and natural gas ； Spiral-welded high-frequency welded steel pipes for transporting pressurized fluids (SY5038-83) – spiral-welded high-frequency welded steel pipes used for transporting pressurized fluids, welded by high-frequency lap welding. Steel pipes have strong pressure resistance, good plasticity, and are easy to weld and shape ； Spiral-welded submerged arc welded steel pipes for general low-pressure fluid transportation (SY5037-83) are submerged arc welded steel pipes used for transporting general low-pressure fluids such as water, gas, air, and steam, manufactured by double-sided automatic submerged arc welding or single-sided welding methods. The common standards for spiral pipes nowadays generally include: SY/T5037-2000 (industry standard, also known as spiral-welded submerged-arc welded steel pipes for transporting ordinary fluids); GB/T9711.1-1997 (national standard, also known as Part 1 of the Technical Specifications for Steel Pipes Used in the Oil and Gas Industry: Grade A steel pipes; currently, the more stringent requirement is specified by GB/T9711.2 for Grade B steel pipes); API-5L (American Petroleum Institute, also known as pipeline steel pipes) ； Which are divided into two grades: PSL1 and PSL2); SY/T5040-92 (Spiral-welded submerged-arc welded steel pipes for piles). Materials for spiral pipes: Q235A, Q235B, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb; Q345, L245, L290, X42, X46, X70, X80, X95. 14. Cast iron pipes: Pipes that are formed by casting cast iron. Cast iron pipes are used for water supply, drainage, and gas transmission pipelines; they include cast iron straight pipes and fittings. Low labor intensity. Based on the casting method, they are divided into continuous cast iron pipes and centrifugally cast iron pipes; the latter are further classified into sand mold and metal mold types. They are classified into gray cast iron pipes and ductile iron pipes based on the material. The flexible joints are sealed with rubber rings; the nominal diameter of continuous gray cast iron pipes ranges from 75 to 1200 millimeters, and they use socket-type or flange-type joints ； Based on function, they can be further divided into flexible interfaces and rigid interfaces. The length of the straight pipe is 4 meters, 5 meters, and 6 meters; it is classified into three grades—LA, A, and B—based on wall thickness. The nominal diameter of sand-cast centrifugal gray cast iron pipes ranges from 200 to 1000 millimeters, with effective lengths of 5 meters and 6 meters ； It is divided into P and G grades based on wall thickness. It features high strength, good toughness, thin wall thickness, reduced metal usage, and the ability to withstand high pressures. Compared to gray cast iron pipes, ductile iron pipes have higher strength, better toughness, thinner walls, less metal used, and the ability to handle higher pressures; their effective length is 5 meters or 6 meters ； It is divided into P and G grades based on wall thickness. It is the development direction of cast iron pipes. The connection between pipes is achieved using socket-type or flange-type interfaces ； Based on function, they can be further divided into flexible interfaces and rigid interfaces. Flexible joints are sealed with rubber rings, allowing a certain degree of rotation and displacement; as a result, they offer good seismic resistance and sealing properties. They are easier and faster to install than rigid joints, and require less labor depending on the casting method used. For those working with cast iron pipes.