Correct marking of seamless steel pipes （SMLS steel pipe） refers to the method of clarifying their specifications, materials and standards through a standardized format. The core is to mark "outer diameter × wall thickness × length" (unit: mm), such as Φ108×4×6000. Correctly marking seamless steel pipes is like affixing accurate labels to goods, which plays an indispensable role in ensuring product quality, convenience of use and safety. Accurate labeling allows users to quickly understand the various parameters of the steel pipe and determine whether it meets the use requirements, thereby avoiding safety hazards caused by parameter mismatches and ensuring the smooth progress of production activities. The following is a careful summary of the following common seamless steel pipe marking methods:
Marked according to national standards (GB standards)
According to GB standards, the dimensions of seamless steel pipes must be marked in the order of "outer diameter × wall thickness × length", all in millimeters (mm). The length can be omitted or marked with a specific value according to requirements.
For example:
Φ108×4×6000: seamless steel pipe with outer diameter of 108mm, wall thickness of 4mm and length of 6000mm.
Φ57×3
When the length is omitted, the default is to use an indefinite length (usually 3-12m), which is suitable for scenarios where the length is not specified during procurement.
Classification by purpose
The marking method of seamless steel pipe can also be classified according to its use. Common uses are:
Seamless steel pipe for structure (GB/T 8162)
Seamless steel pipe for fluid transportation (GB/T 8163)
Boiler pipe (GB/T 3087)
Petroleum cracking pipe (GB/T 9948)
High-pressure boiler pipe (GB/T 5310)
The marking method usually includes:
Purpose (such as boiler tube) + material brand + outer diameter x wall thickness + standard number
Boiler tube 20G 42×4
Boiler tube: indicates that the steel tube is used in boiler system.
20G: indicates that the material is 20G (high temperature alloy steel).
42×4: indicates that the outer diameter is 42mm and the wall thickness is 4mm.
Marking by material grade
The material grade marking of seamless steel pipes is the key to clarifying their chemical composition, mechanical properties and application scenarios. It needs to be marked in combination with national standards (GB), industry standards and international general system specifications. The following are the marking methods and examples of common material grades:
For example:
High-quality carbon structural steel (GB/T 699) Marking rules:
Expressed as carbon content in ten thousandths, with “#” or “steel” after the number.
20# steel (carbon content about 0.20%)
Marking: Φ89×4×6000, 20# steel, GB/T 8162-2018 (for structure)
Marking by outer diameter and wall thickness
In the marking of seamless steel pipes, the outer diameter and wall thickness are very important parameters, which are usually expressed in the form of "outer diameter × wall thickness".
For example: 76×4
76: The outer diameter is 76mm.
4: The wall thickness is 4mm.
Marking according to the manufacturing standard of steel pipe
The production standard labeling adopts international or domestic standards to indicate the specifications followed by steel pipe production. Common ones include the American Petroleum Institute standard API, which has strict requirements for steel pipes used in the oil and gas industry; the American Society for Testing and Materials standard ASTM, which covers a variety of material standards; the German industrial standard DIN, which is widely used in Europe; the Japanese industrial standard JIS, etc. Different production standards are suitable for different application fields and use environments.
For example: ASTM A106 Gr.B 3/4"
ASTM A106: Indicates compliance with ASTM A106 standard (for high-temperature steam pipes).
Gr.B: Indicates that the pipe is made of Grade B material.
3/4": Indicates that the outer diameter is 3/4 inches.
Special performance marking of pipelines
For some seamless steel pipes with special properties, their special properties, such as corrosion resistance and wear resistance, etc., need to be indicated during marking.
Stainless steel pipe 304 50×3.0
Stainless steel pipe: indicates that the material of the steel pipe is stainless steel.
304: indicates that the material of the steel pipe is 304 stainless steel.
50×3.0: indicates that the outer diameter is 50mm and the wall thickness is 3.0mm.
Other standards and marking methods
In addition to the common standard marking methods mentioned above, more technical details and special requirements may be involved, such as:
API standard: seamless steel pipes used in the petroleum industry, generally marked as API 5L or API 5CT, etc.
Pressure vessel pipeline: pipelines that comply with ASME standards or other international standards.
Notes on marking
When marking, clarity, accuracy and completeness are the basic principles. The marked information must be clear and easy to read, with characters of moderate size to avoid ambiguity, otherwise it will affect subsequent identification and use. Key details such as size, material, standard number, etc. must be accurate, as any mistake may lead to serious consequences.
In actual production, there was a case where due to a dimension marking error, the wall thickness of 4 mm was mistakenly marked as 3 mm. This was used for a pressure pipe. After it was put into use, the pipe broke because it could not withstand the pressure. This not only caused economic losses, but also led to production stagnation, with a severe impact. The annotation content must also be complete and important information should not be omitted. Only by fully presenting all parameters can we fully reflect the product characteristics and provide users with a reliable basis.
Conclusion
In the complex network of industrial production and construction, seamless steel pipe marking is a key node to ensure its circulation and use. Accurate labeling can enable each seamless steel pipe to find its appropriate application scenario and maximize its value. From the standardization of marking content, to the display of marking examples, to the emphasis on marking precautions, each link is closely linked and together constitutes a complete system for seamless steel pipe marking.
