I. Classification of Profiles
1. Single section steel
① Square steel – hot-rolled square steel, cold-drawn square steel;
② Round steel – hot rolled round steel, forged round steel, cold drawn round steel
③ Wire rod;
④ Flat steel;
⑤ Flat steel spring;
⑥ Angle steel – equal angle steel, unequal angle steel;
⑦ Steel triangle
⑧ Hexagonal steel;
⑨ Arc-shaped steel;
⑩ Elliptical steel
2. Steel Complex Section
① I beam – common I beam, light I beam
② Steel channel – hot rolled steel channel (common steel channel, mild steel channel), bent steel channel
③ H beam (also known as wide-leg I beam)
④ Steel rail – heavy rail, light rail, crane rail, other special rail
⑤ Window frame steel
⑥ Steel sheet piling
⑦ Bent section steel – cold formed steel, hot formed steel
⑧ Others
II. Classification of Large, Medium and Small Sections in Structural Steel
| Profiles | Big | Average size | Small size |
| I-beam | Height ≥ 180 mm | Height<180mm | / |
| Channel steel | Height ≥ 180 mm | Height<180mm | / |
| Equilateral angle steel | Edge width 2160 mm | Edge width 50-140mm | Edge width 20-45mm |
| Unequal Angle Steel | Edge width ≥ 160 × 100 mm | Edge width 140 × 90-50 × 32 mm | Edge width ≤ 45 × 28 mm |
| Round steel | Diameter ≥ 90mm | Diameter 38-80mm | Diameter 10-36mm |
| Square steel | Edge width 290 mm | Edge width 50-75mm | Edge width 10-25mm |
| Flat steel | Width ≥ 120mm | Width 60-100mm | Width 12-55mm |
| Threaded steel | / | Diameter ≥ 40mm | Diameter 10-36mm |
| rivet steel | / | / | Diameter 10-22mm |
| Others | Special shaped steel: track shoes, steel sheet piles, etc. | Special shaped steel, composite flat steel for small agricultural tools, etc. | Special shaped steel, agricultural tool steel, window frame steel, etc. |
III. Wire machine
They mainly refer to hot-rolled round steel with a diameter of 5 to 9 mm and threaded steel with a diameter of less than 10 mm. Most are supplied in coil form via a winding machine, also known as a bobbin bar or wound bobbin.
Wire rod is mainly used as reinforcement in reinforced concrete, welding of structural components or for further processing (such as drawing, stapling, etc.) as a raw material.
According to the steel distribution directory, wire rod includes common low carbon steel hot-rolled coil bars, welding coil bars, shot blasting wire coil bars, tempered thread coil bars, and of high quality coils.
The most widely used wire rod is common low carbon steel hot-rolled coil bar, also known as common wire rod. It is hot rolled from common carbon steel Q195, Q215, Q235, with a nominal diameter of 5.5-14.0mm.
Generally, each coil weighs between 100-200kg. Currently, high-speed, twist-free wire rod rolling mills are often used for rolling, followed by controlled cooling after rolling. The diameter varies from 5.5 to 22.0 mm, with a maximum coil weight reaching 2,500 kg.
Common wire rod is mainly used in construction, drawing, packaging, welding rods and in the manufacture of screws, nuts, rivets, etc. High-quality wire rod is only supplied as hot-rolled bars of high-quality carbon structural steel. , such as 08F, 10, 35Mn, 50Mn, 65, 75Mn, etc. They serve as raw materials for steel wire and other metal products and other structural components, with other high-quality steels rolled into wire rod.
Typically, anything above 8mm is classified as a high-quality profile, while anything below 8mm is classified as a metal product. In addition to the strength requirements for wire rod, cold bending tests, size checks, etc. are carried out based on its uses. The surface must be free from defects such as cracks, folds, crusts, holes, delamination and inclusions.
4. Hot rolled ribbed rebar
1. Types and specifications
The designation of hot-rolled ribbed rebar is formed by the initials HRB and the minimum yield strength of the class. H, R and B represent, respectively, hot rolled, ribbed and bars. There are three types of hot rolled ribbed rebar: HRB335 (former grade 20MnSi), HRB400 (former grade 20MnSiV, 20MnSiNb, 20MnTi) and HRB500.
2. Grade III Vanadium Threaded Rebar
① Promising market prospects for grade III vanadium threaded rebar
The new grade III vanadium threaded rebar (20MnSiV, 400Mpa), which incorporates alloys such as vanadium, niobium and titanium during production, features higher strength, better toughness, superior welding performance and good seismic resistance compared to grade II threaded rebar common.
In the construction markets of developed countries such as Europe, grade III threaded rebar constitutes 80% of the total threaded rebar volume. The use of high-strength grade III vanadium threaded rebar has reached 80-90% in countries such as the United Kingdom, Germany, Australia and Japan.
Introduced in China in 1995 by the former Ministry of Metallurgy and Ministry of Construction, the new technical specifications of Grade III threaded rebar have been incorporated into the national standard GBJ10-89 “Concrete Structure Design Specifications”.
It has been implemented since January 1, 1997 and has been successfully applied to tall buildings, large power plants, bridges, tunnels, airports and other engineering projects, demonstrating a vast market potential. The Ministry of Construction intended that the new grade III rebar would reach 50% of the total volume of threaded rebar by 2002, and 80% by the end of the “10th Five-Year Plan”.
However, due to insufficient promotion, its use is still significantly lower than the old ordinary Grade II 335Mpa threaded rebar. Therefore, vigorous promotion and marketing for the new Grade III threaded rebar is necessary.
② Advantages of grade III vanadium threaded rebar
A. Economical: Due to its high strength, the new Grade III threaded rebar saves 10-15% steel compared to Grade II, thus reducing the construction cost.
B. High strength and good toughness: Microalloy treatment produces yield point above 400Mpa and tensile strength above 570Mpa, each 20% higher than Grade II threaded rebar.
C. Anti-seismic: Vanadium rebar features superior flexural strength, aging resistance and low-cycle fatigue performance, making it far superior to Grade II threaded rebar in seismic resistance.
D. Weldable: With carbon content ≤0.54%, it offers excellent weldability, accommodating a variety of welding methods with simple and convenient processes.
E. Convenient Construction: New Grade III threaded rebar increases the construction gap, ensuring convenience and construction quality.
V. Hot rolled H steel
1. Representation of hot rolled H steel
H steel is categorized into wide flange H steel (HK), narrow flange H steel (HZ) and H steel pile (HU). Its representation is: Height H × Width B × Web thickness t1 × Flange thickness t2.
For example, H steel Q235, SS400 200×200×8×12 represents a wide flange of H steel with a height of 200 mm, a width of 200 mm, a web thickness of 8 mm and a flange thickness of 12 mm, with its grade being Q235 or SS400.
2. Advantages of hot rolled H steel
H steel is a new type of economical construction steel. Its section shape is economical and reasonable, with excellent mechanical properties. It stretches evenly at all points of the section during rolling, has little internal stress, and compared to ordinary I-beam steel, it has a larger section modulus, lighter weight, and the advantage of saving metal, which can reduce weight of the building structure by 30-40%.
Due to the parallel inner and outer sides of the legs and the right-angled leg ends, assembling it into components can save up to 25% of welding and riveting work. It is commonly used in large structures that require large shear capacity and good section stability (such as factories, high-rise buildings, etc.), as well as bridges, ships, lifting and transport machinery, equipment foundations, supports, foundation piles, and more.
SAW. Cold formed steel
Cold-formed steel is an economical, lightweight and thin-walled steel material, also known as cold-formed steel profile or cold-formed profile. It is formed by bending hot- or cold-rolled steel strips into various cross-sectional shapes and sizes. Cold-formed steel has the following characteristics:
1. Economical and rational cross section, material saving. The cross-sectional shape of cold-formed steel can be designed according to needs, with a reasonable structure and a higher section coefficient per unit weight compared with hot-rolled steel.
Under the same load, the weight of components can be reduced, saving materials. When used in building structures, cold-formed steel can save 38-50% metal compared to hot-rolled steel, and when used in agricultural machinery and vehicles, it can save 15-60% metal. This makes construction easier and reduces overall costs.
2. Various varieties, capable of producing cold-formed steel profiles with uniform wall thickness and complex cross-sectional shapes that are difficult to produce using general hot-rolling methods, as well as cold-formed steel made from different materials.
3. The surface of the product is smooth and attractive, with precise dimensions, and the length can be flexibly adjusted according to needs. They are supplied entirely according to size or in multiple sizes, improving the use of the material.
4. The production process can be coordinated with punching and other operations to meet different needs.
Cold-formed steel comes in several types. From a transversal point of view, there are open, semi-closed and closed types. The main products include cold-formed channel steel, angle steel, Z-shaped steel, cold-formed corrugated steel sheet, square tube, rectangular tube, special-shaped steel tube for electric welding, roller shutter door, etc.
Cold-formed steel typically produced is less than 6mm thick and less than 500mm wide. The products are widely used in industries such as mining, construction, agricultural machinery, transportation, bridges, petrochemicals, light industry and electronics.
VII. High quality profiles
High-quality profiles are shapes made from premium steel, categorized into hot-rolled (forged), cold-drawn (pulled), and other varieties.
High-quality hot-rolled (forged) profiles include carbon structural steel, carbon tool steel, alloy structural steel, spring steel, stainless steel, bearing steel, alloy tool steel, mold steel, and high speed tools.
High quality cold drawn (drawn) profiles include carbon structural steel, carbon tool steel, alloy structural steel, spring steel, stainless steel, bearing steel, alloy tool steel, high speed tool steel , free cutting steel, cold heading steel and S/5A. S/5A is a product often used to make artillery shells and bullet points.
Other varieties are high-quality specialized profiles, including hollow steel, oxygen cylinder material, cold steel, industrial pure iron, hot-rolled free cutting steel, D60, S/5A, F18, F11 and more. The latter are military-grade materials.
High-quality profiled steel comes in various sizes, with round and square steel classified by specification range, such as 8-10mm, 11-15mm, 18-20mm, 205-245mm. Flat steel is classified by cross-sectional area into large, medium and small planes. Hexagonal steel is not graded by range.
However, the range of high-quality steel profiles cannot replace specific specifications, which must be provided in the documentation. The specifications of high-quality profiles are simple, with the majority being round steel. In addition, square steel, flat steel, hexagonal steel, hollow steel and special shapes are available.
The dimensional deviations of high-quality hot-rolled (forged) round, square and hexagonal steel feature common accuracy and higher accuracy. Cold drawn profiles have more precise dimensions and smoother surfaces, some of which are subsequently polished or ground.
Round steel with surfaces refined through polishing or grinding is called bright steel. High-quality profiles are rarely used as is. They often undergo additional processing and heat treatment at the user's facility. Therefore, in addition to guaranteeing the chemical composition, it is essential to guarantee the mechanical properties after heat treatment.
