GB/T 706-2016 is a Chinese national recommended standard titled Hot rolled section steel, issued on December 30, 2016, and officially implemented on September 1, 2017. It supersedes the previous version GB/T 706-2008 and is jointly released by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China and the Standardization Administration of the People's Republic of China, under the jurisdiction of the China Iron and Steel Industry Association全. Its ICS number is 77.140.70, and the Chinese standard classification number is H44.
1. Scope
This standard specifies the order contents, dimensions, shape, weight and their permissible deviations, technical requirements, test methods, inspection rules, as well as packaging, marking and certification requirements for hot - rolled I - beams, hot - rolled channels, hot - rolled equal - leg angles and hot - rolled unequal - leg angles. It applies to the above - mentioned section steels, especially hot - rolled I - beams and channels with tapered inner flanges. It serves as a core technical specification for the production, procurement, inspection and acceptance of these hot - rolled section steels in China.
2. Core Technical Provisions
2.1 Order Contents
When placing an order, the following key information should be clearly specified: standard number, product name, type, specification (such as section size, length), material grade (e.g., Q235B, Q355B), delivery status, quantity, and special requirements (if any).
2.2 Dimensional, Shape and Weight Requirements
It details the permissible deviations for the cross - sectional dimensions (like flange width, web thickness, leg length of angles), length, straightness, torsion, and theoretical weight of various section steels. For example, it stipulates the allowable errors of the leg length, thickness and angle of equal - leg and unequal - leg angles, and the flange and web dimensions of I - beams and channels, which provides a unified standard for product dimensional accuracy control.
2.3 Technical Requirements
Chemical Composition: The chemical composition of steel should comply with the corresponding requirements of basic standards such as GB/T 700 (carbon structural steel) and GB/T 1591 (high - strength low - alloy structural steel).
Mechanical Properties: It specifies the required values of mechanical properties like yield strength, tensile strength, elongation and impact toughness, which should be tested in accordance with GB/T 228.1 (tensile test), GB/T 229 (impact test) and other standards.
Surface Quality: The surface of section steels shall be free of defects such as cracks, folds, scabs and inclusions that affect the use. Minor surface defects can be allowed if they do not exceed the specified dimensional tolerance range.
Delivery Status: Most section steels are delivered in the hot - rolled state, and some can be delivered after heat treatment as required.
2.4 Test Methods and Inspection Rules
Test Methods: It clarifies the specific test methods for dimensional measurement, chemical composition analysis, mechanical property testing and surface quality inspection. For instance, dimensional inspection can be carried out with calipers, rulers and other measuring tools, and chemical composition can be determined by spectral analysis or chemical analysis.
Inspection Rules: It defines the batch division, sampling quantity, inspection items and judgment criteria. For example, mechanical property tests are conducted on a sampling basis for each batch of products, and the batch is judged as qualified only if all the sampled products meet the standard requirements.
2.5 Packaging, Marking and Certification
Section steels should be properly packaged to prevent damage during transportation and storage. Each batch of products must be marked with information such as the manufacturer's name, standard number, product specification, material grade and batch number, and be accompanied by a quality certificate indicating the test results and compliance with the standard.
3. Significance and Application
GB/T 706-2016 unifies the technical specifications of hot - rolled section steels in the Chinese market, ensuring the consistency and stability of product quality. It is widely used in construction, machinery manufacturing, petrochemical, bridge engineering and other fields. It provides a reliable technical basis for design units to select materials, manufacturers to organize production, and procurement parties to conduct quality inspection, and promotes the standardized and orderly development of the hot - rolled section steel industry.
