Technical Regulation for Low-Alloy Structural Steels
This regulatory document establishes a comprehensive list of requirements for high-strength low-alloy steels, governing labeling methods, physical and chemical parameters, dimensional tolerances, profile geometry, quality control procedures, packaging rules, and documentary proof of compliance. The provisions of the standard apply to steel plates, strip steel, shaped profiles, merchant bars, and steel billets used in critical engineering and construction structures supplied by EV Group China.
Normative References
The application of this standard is based on the current versions of the following regulations. In the absence of a revision date, the current version of the document, including all amendments, shall be followed:
- GB/T 222 — Permissible deviations for the chemical composition of finished rolled products.
- GB/T 223.3 — Gravimetric method for the determination of phosphorus using diantipyrylmethane.
- GB/T 223.9 — Photometric analysis of aluminum content using chromazurol S.
- GB/T 223.11 — Titration methods for the determination of chromium mass fraction.
- GB/T 223.14 — Determination of vanadium by N-benzoyl-N-phenylhydroxylamine extraction.
- GB/T 223.17 — Photometry with diantipyrylmethane for titanium control.
- GB/T 223.18 — Iodometric analysis of copper using sodium thiosulfate.
- GB/T 247 — Packaging, marking, and certification rules for plate and strip steel.
- GB/T 702 — Technical tolerances for hot-rolled round and square steel.
- GB/T 706 — Standards for hot-rolled shaped profiles.
- GB/T 709 — Geometric dimensions and limit deviations for hot-rolled sheets.
- GB/T 2101 — Requirements for acceptance, packaging, and labeling of shaped steel.
- GB/T 2975-2018 — Rules for the preparation of test specimens for mechanical testing.
- GB/T 4336 — Atomic emission spectrometric analysis of carbon and low-alloy steels.
- GB/T 5313 — Standards for steels with through-thickness characteristic requirements (Z-steels).
- GB/T 8170 — Rules for rounding off numerical values.
- GB/T 11263 — Specifications for H-beams and T-beams.
- GB/T 14977 — Quality requirements for the surface of hot-rolled sheets.
- GB/T 17505 — General delivery conditions for steel products.
- GB/T 20066 — Sampling for chemical analysis.
- GB/T 20123 — Infrared absorption method for carbon and sulfur analysis.
- GB/T 20124 — Nitrogen analysis by thermal conductivity.
- GB/T 20125 — ICP spectrometry for the analysis of multi-component low-alloy steels.
- GB/T 28300 — Classification of surface quality for hot-rolled bars.
Terminology
Thermomechanical Control Process (TMCP)
A technological process of metal deformation under strictly controlled temperature conditions, ensuring the formation of a specific microstructure that cannot be reproduced by standard heat treatment.
Note 1: Heating finished products above 580°C may lead to softening. Coordination of heat treatment at higher temperatures must be carried out with the technical department of EV Group China.
Note 2: The method allows for the use of accelerated cooling, including self-cooling, excluding classic quenching and tempering.
Normalized Rolling
A rolling process in which the final deformation occurs in a temperature range that ensures mechanical properties identical to the results of standard normalization.
Designation System
EV Group China steel marking includes the prefix Q (yield strength), the nominal yield strength value (MPa), the delivery condition code, and the quality category (from B to F). Example: Q355ND.
- Q — Designation for yield strength.
- 355 — Guaranteed minimum yield strength in MPa.
- N — Delivery condition after normalization or normalized rolling.
- D — Impact toughness grade.
For products requiring increased resistance to lamellar tearing, the Z-direction thickness index is added (e.g., Q355NDZ25).
Geometric Parameters and Tolerances
Dimensions, limit deviations for shape, and mass of metal products supplied by EV Group China strictly comply with current GB/T national standards.