1.The importance of 304/304L stainless steel seamless pipe
304/304L ss(stainless steel) seamless pipe is one of the very important raw materials in the manufacture of stainless steel pipe fittings. It is a common chromium-nickel alloy stainless steel with good corrosion resistance and high temperature resistance, and is very suitable for manufacturing pipe fittings.304 stainless steel has good oxidation resistance and corrosion resistance, and can maintain the stability and strength of its structure in a variety of chemical environments. In addition, it also has excellent processing performance and toughness, facilitates cold processing and hot processing, and can meet the manufacturing requirements of different pipe fittings.
Stainless steel pipe fittings, especially seamless pipe fittings, have higher requirements on materials and need to have good sealing and pressure resistance. 304 stainless steel seamless pipe is often used to manufacture various pipe fittings, such as elbows and tees, due to its high strength, corrosion resistance and smooth inner surface.
In short, 304 stainless steel seamless pipes play an important role in the manufacturing of stainless steel pipe fittings. They provide excellent performance and reliable quality, providing an important guarantee for the safe operation and durability of pipe fittings.
Therefore, during the raw material production process, before leaving the factory, they must go through numerous tests and must meet the standard requirements for the production of pipe fittings. The following are some performance inspection methods for 304/304L stainless steel seamless pipes.
2. Performance testing of 304/304L stainless steel seamless pipes
(1)Corrosion resistance inspection
304 stainless steel seamless pipes should be subjected to corrosion resistance tests according to standards or corrosion methods agreed upon by both parties.① Intergranular corrosion test
The purpose of this test is to detect whether seamless pipes are prone to intergranular corrosion. Intergranular corrosion is a kind of local corrosion that will form corrosion cracks at the grain boundaries of the material, eventually leading to material failure.② Stress corrosion test
The purpose of this test is to detect the corrosion resistance of stainless steel seamless pipes under stress and corrosive environments. Stress corrosion is a highly dangerous form of corrosion that causes cracks to form in parts of a material where it is stressed, causing the material to break.③ Pitting corrosion test
The purpose of this test is to test the material's ability to resist pitting corrosion in an environment containing chloride ions. Pitting corrosion is a form of localized corrosion that creates small holes on the surface of the material that gradually enlarge to form cracks.④ Uniform corrosion test
The purpose of this test is to detect the overall corrosion resistance of materials in corrosive environments. Uniform corrosion refers to the uniform formation of oxide layers or corrosion products on the surface of materials.When conducting corrosion tests, it is necessary to select appropriate test conditions, such as corrosive media, temperature, pressure, exposure time, etc. After the test, it is necessary to conduct visual inspection, weight loss measurement, metallographic analysis and other methods on the sample to judge the corrosion resistance of the material.
(2) Process performance inspection
Flattening test: detects the deformation ability of the pipe in the flat direction.Tensile test: Measures the tensile strength and elongation of a material.
Impact test: uates the toughness and impact resistance of materials.
Expansion test: Test the pipe's resistance to deformation during the expansion process.
Hardness test: measure the hardness value of materials.
Metallographic test: observe the structure and phase transformation of the material.
Bending test: uate the deformation and damage of the pipe during the bending process.
Non-destructive testing: including eddy current testing, X-ray testing and ultrasonic testing, used to detect defects and defects inside the pipe.
(3)Chemical analysis
Chemical analysis of the material chemical composition of 304 stainless steel seamless pipes can be carried out through spectral analysis, chemical analysis, energy spectrum analysis and other methods. Among them, the type and content of elements in the material can be determined by measuring the spectrum of the material. The type and content of elements can also be determined through chemical dissolution, oxidation and reduction operations on materials, and then through titration or instrumental analysis. Energy spectrum analysis is a fast and simple method that can determine the type and content of elements in the material by subjecting the material to electron beam excitation and then detecting the resulting X-rays or characteristic radiation.For 304 stainless steel seamless pipes, the chemical composition of the material should meet standard requirements, such as the Chinese standard GB/T 14976-2012 "Stainless steel seamless pipes for fluid transportation", which stipulates various chemical composition indicators of 304 stainless steel seamless pipes, Such as the content range of carbon, silicon, manganese, phosphorus, sulfur, chromium, nickel, molybdenum, nitrogen and other elements. When conducting chemical analysis, these standards or specifications need to be used as a basis to ensure that the chemical composition of the material meets the requirements.
- Iron (Fe): balance
- Carbon (C): ≤ 0.08% (304L carbon content ≤ 0.03%)
- Silicon (Si): ≤ 1.00%
- Manganese (Mn): ≤ 2.00%
- Phosphorus (P): ≤ 0.045%
- Sulfur (S): ≤ 0.030%
- Chromium (Cr): 18.00% - 20.00%
- Nickel (Ni): 8.00% - 10.50%
These values are the range required by general standards, and the specific chemical composition can be fine-tuned according to different standards (such as ASTM, GB, etc.) and the manufacturer's specific product requirements.
(4) Air pressure and water pressure test
The hydraulic pressure test and air pressure test of 304 stainless steel seamless pipe are used to detect the pressure resistance and air tightness of the pipe.①Hydraulic pressure test
Prepare the specimen: Select a suitable specimen and ensure that the length and diameter of the specimen meet the test requirements.Connect the specimen: Connect the specimen to the hydraulic testing machine, ensuring that the connection is well sealed.
Start the test: Inject water at the specified pressure into the sample and maintain it for the specified time. Normally, the test pressure is 2.45Mpa, and the holding time cannot be less than five seconds.
Check for leaks: Observe the sample for leaks or other abnormalities during the test.
Record results: Record the pressure and results of the test and analyze the results.
②Air pressure test
Prepare the specimen: Select a suitable specimen and ensure that the length and diameter of the specimen meet the test requirements.Connect the specimen: Connect the specimen to the pneumatic testing machine, ensuring that the connection is well sealed.
Start the test: Inject air at the specified pressure into the sample and maintain it for the specified time. Normally, the test pressure is 0.5Mpa, and the holding time can be adjusted as needed.
Check for leaks: Observe the sample for leaks or other abnormalities during the test.
Record results: Record the pressure and results of the test and analyze the results.
It should be noted that the test should be carried out in suitable environment and conditions, such as temperature, humidity and other parameters should meet the test requirements. At the same time, you need to pay attention to safety when conducting tests to avoid accidents during the test.
