I. Basic Classification of Steel (by Shape and Application)

**Structural Steel:** Includes H-beams, I-beams, channel steel, angle steel, T-beams, and steel sheet piles. Primarily used in building structures, factory frameworks, bridges, and foundation pit support systems.

**Plate and Sheet Steel:** Includes medium-to-heavy plates, hot-rolled coils, cold-rolled coils, galvanized sheets, and color-coated sheets. Primarily used in machinery manufacturing, pressure vessels, roofing and wall systems, and appliance casings.

**Steel Pipe and Tube:** Includes seamless steel pipes, straight-seam welded pipes, spiral-welded pipes, and galvanized pipes. Primarily used for fluid conveyance, petrochemical applications, and structural steel supports.

**Bar and Wire Rods:** Includes round bars, deformed bars (rebar), and wire rods. Primarily used for concrete reinforcement, mechanical processing, and the manufacturing of standard fasteners.

II. Comparison of Common International Standards

**Chinese National Standards (GB) – Common Grades:** Q235B, Q355B, 20#, 45#, HRB400.

**American Standards (ASTM) – Common Grades:** A36, A572 Gr50, A53 Gr.B, A992.

**Japanese Standards (JIS) – Common Grades:** SS400, SM490A, STK400, S45C.

**European Standards (EN) – Common Grades:** S235JR, S355JR, S275J0, S355J2.

**British Standards (BS) – Common Grades:** 43A, 50B, 43C (most have now been incorporated into European Standards).

**Approximate Material Equivalents (For Reference Only; Not Direct Substitutes):** GB Q235B is roughly equivalent to JIS SS400, ASTM A36, and EN S235JR; GB Q355B is roughly equivalent to JIS SM490A, ASTM A572 Gr50, and EN S355JR.

III. Steel Specification Notation Methods

**H-Beams** (Common across American, Japanese, and European standards) are designated using the following format: Height × Width × Web Thickness × Flange Thickness. For example, HW 200 × 200 × 8 × 12 indicates a height of 200 mm, a width of 200 mm, a web thickness of 8 mm, and a flange thickness of 12 mm. Common lengths are 6 meters, 9 meters, or 12 meters, or cut to specific lengths according to customer requirements.

**I-beams** are designated either by their model number (representing the height in centimeters) or by their weight per meter. For instance, "I 10" indicates a height of 100 mm and a weight of approximately 11.3 kg per meter; American standards commonly utilize the "W" series—such as "W6 × 9"—which denotes a height of 6 inches and a weight of 9 pounds per foot.

**Channel steel** is designated by its height multiplied by its leg width, multiplied by its web thickness. For example: 100 × 48 × 5.3 mm. **Angle steel** is designated by its leg length multiplied by its leg thickness. For example, "L 50 × 5" indicates an equal-leg angle steel with a leg length of 50 mm and a thickness of 5 mm.

**Steel plates** are designated by their thickness multiplied by their width, multiplied by their length (in millimeters). For example: 10 × 1500 × 6000 mm. **Coiled steel** is designated by its thickness multiplied by its width; the weight per coil typically ranges between 15 and 30 tons.

**Seamless steel pipes** are designated by their outer diameter multiplied by their wall thickness. For example: an outer diameter of 219.1 mm multiplied by a wall thickness of 6.3 mm. Common standards include the Chinese National Standards GB/T 8162 (for structural pipes) and GB/T 8163 (for fluid transport pipes), as well as the American Standard ASTM A106 Gr.B.

**IV. Key Quality Indicators and Inspection Points**

**Material Inspection:** Typically performed using Spectroscopic Analysis (PMI) or by verifying the Mill Test Certificate (MTC). A common issue is the mixing of different steel grades; the solution involves requiring the steel mill to provide the original MTC and conducting spot checks on-site.

**Dimensional Tolerance Inspection:** Measurements are taken using calipers, micrometers, and tape measures. The results should be compared against the permissible deviation ranges specified in the relevant standards (e.g., the American Standard ASTM A6).

**Surface Quality Inspection:** Conducted via visual inspection to check for the presence of cracks, scabs, folds, or severe corrosion.

**Weight Verification:** Can be determined either by actual weighing on a scale or by theoretical weight calculation. Fixed-length steel plates are generally invoiced based on their theoretical weight, whereas structural steel shapes and pipes may be invoiced based on their actual weighed weight, in accordance with client requirements.

**Straightness and Twist Inspection:** Measurements are taken using a surface plate and feeler gauges. The results are compared against the allowable curvature tolerances specified in the relevant standards (typically ranging from 1 to 2 parts per thousand of the total length).

**Coating or Plating Inspection:** Measurements are taken using a coating thickness gauge; alternatively, a salt spray test may be commissioned. For instance, the US standard ASTM A123 mandates that the weight of the galvanized coating must be no less than 505 grams per square meter.

**V. Packaging and Export Shipping Considerations**

**Rust Prevention:** If the steel is to be stored indoors for more than one month, it is recommended to apply rust-inhibiting oil or wrap the material in VCI (Vapor Corrosion Inhibitor) paper. For export via sea freight, the exterior must be wrapped in waterproof film, and edge protectors should be installed at the corners to prevent damage.

**Bundling Methods:** Structural steel shapes and pipes are bundled using steel strapping or wire ties; to facilitate loading and unloading, the weight of each bundle generally does not exceed 3 tons. Steel plates are secured using steel pallets or "well-frame" racks to prevent shifting during transit.

**Shipping Marks (Marks & Nos.):** Markings must include essential information such as product specifications, applicable standards, furnace/batch numbers, net and gross weights, and the destination. It is also recommended to include English warning labels—for example, "Keep Dry" or "Handle with Care."

**Third-Party Inspection:** Common inspection agencies include SGS, BV, Intertek, and TÜV. Inspection checkpoints may be scheduled for mid-production (involving sampling) or immediately prior to loading (involving a comprehensive inspection); the inspection agency must be notified 3 to 5 days in advance.

**VI. Common Client Questions and Answers (Technical)**

**Q: Can US Standard A36 steel be used interchangeably with Chinese Standard Q235B steel?**

**A:** While the mechanical properties of the two grades are similar, they are not entirely identical. US Standard A36 has a slightly lower tensile strength range (approximately 400 to 550 MPa), whereas Q235B falls within the range of 370 to 500 MPa; furthermore, the requirements for impact toughness differ between the two standards. It is strongly recommended to supply materials strictly in accordance with the standards specified in the design drawings, rather than making arbitrary substitutions.

**Q: What is the difference between "Fixed Length" and "Random Length" steel?**

**A:** "Fixed Length" refers to steel that has been cut to a specific, predetermined length (e.g., 12 meters) as requested by the client prior to delivery. "Random lengths" refers to material supplied in non-uniform lengths (e.g., a mixed batch ranging from 5 to 11 meters). This option is typically more economical and is suitable for projects where strict length specifications are not required.

Q: What is the difference between hot-rolled coils and cold-rolled coils?

A: Hot-rolled coils feature a rough surface finish and wider thickness tolerances, but they are lower in cost and are primarily used for structural components. Cold-rolled coils, conversely, possess a smooth surface and high dimensional precision, making them suitable for stamping applications, appliance casings, and automotive parts.

Q: Can you supply special lengths or non-standard dimensions?

A: Yes, we can. However, such requests are subject to the steel mill's minimum rolling quantity requirements (typically ranging from 50 to 200 tons) and will incur additional costs for leveling or sawing. We recommend that you provide us with the specific dimensions and quantities in advance so that we may assist you in assessing the feasibility of your request.