GOST 9940-81 is a national standard formulated by Russia, specifically addressing the technical requirements for hot-deformed seamless steel pipes made of corrosion-resistant steel. Below is a detailed introduction:
1. Background and Replacement Relationship
Publication and Replacement: GOST 9940-81 was issued in 1981, replacing the older version GOST 9940-72. It clarifies the design, manufacturing, and inspection specifications for hot-deformed seamless steel pipes made of corrosion-resistant steel.
Standard Nature: As a Soviet national standard, GOST 9940-81 is still utilized by Russia and some Commonwealth of Independent States (CIS) countries, serving as a crucial technical reference in the field of corrosion-resistant steel pipes.
2. Scope of Application and Material Requirements
Scope of Application: This standard applies to general-purpose hot-deformed seamless steel pipes made of corrosion-resistant steel, primarily used for transporting corrosive media (such as in pipelines in the chemical, petroleum, and natural gas industries) and for manufacturing corrosion-resistant mechanical structural components.
Material Requirements: The steel pipes must be made from ordinary corrosion-resistant steel, with the steel grade meeting specific chemical composition and mechanical property requirements, such as tensile strength and yield strength, to ensure long-term stability in corrosive environments.
3. Classification and Dimensional Specifications of Steel Pipes
Classification Methods:
By Production Method: Divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, and pilgered pipes. GOST 9940-81 primarily focuses on hot-deformed seamless steel pipes.
By Cross-Sectional Shape: Divided into round pipes and shaped pipes (such as square and elliptical pipes), with round pipes being the most widely used.
Dimensional Specifications:
Outer Diameter and Wall Thickness: The outer diameter and wall thickness of the steel pipes must comply with the provisions in Table 1 of the standard. For example, for steel pipes with an outer diameter of 57-325 mm, the wall thickness deviation must meet specific requirements.
Length Specifications: Steel pipe lengths are classified as fixed lengths, multiple lengths, and random lengths. The deviation for fixed lengths does not exceed +15 mm; for multiple lengths, the deviation per segment is +5 mm, with a total length deviation of +15 mm; random lengths range from 1.5-10 m, and steel pipes exceeding 10 m can be produced upon agreement between the supplier and the buyer.
4. Inspection Rules and Quality Requirements
Inspection Items:
Chemical Composition Analysis: Ensures that the material of the steel pipes meets the chemical composition requirements specified in the standard.
Mechanical Property Testing: Includes tensile tests, flattening tests, etc., to verify the strength and plasticity of the steel pipes.
Non-Destructive Testing: Such as ultrasonic testing, to check for internal defects in the steel pipes.
Quality Requirements: The steel pipes must pass the above inspection items to ensure their quality meets the standard requirements before they can enter the market.
5. Standard Application and Certification
Application Fields: GOST 9940-81 standard steel pipes are widely used in the chemical, petroleum, natural gas, and machinery manufacturing industries, serving as important materials for transporting corrosive media and manufacturing corrosion-resistant structural components.
Certification Requirements: Steel pipes conforming to GOST 9940-81 must pass the Russian national certification system (such as GOST R certification) to enter the Russian and CIS markets. Many Chinese steel pipe manufacturers have obtained this standard certification, enabling their products to be exported to Russia and other countries.
6. Standard Updates and Replacement
Standard Updates: GOST 9940-81 has undergone multiple revisions to adapt to technological advancements and changes in market demand. For example, the standard has extended its validity period and modified its text content.
Replacement Standards: With technological development, Russia may introduce new standards to replace GOST 9940-81. However, as of the current time, this standard remains widely used.
