I. Visual Inspection
Surface Smoothness: Observe whether the surface of the stainless steel material is smooth, without obvious bumps, wrinkles, or wavy patterns. This can be observed directly with the naked eye or felt by touch to assess the smoothness of the surface.
Color: Stainless steel has its specific metallic luster. Under normal circumstances, it should be silvery-white and bright. If it appears yellowish, dull, or has black spots, it may indicate that the material has been contaminated, corroded, or has inherent quality problems. For example, the color of 304 stainless steel is usually quite uniform and bright.
Defect Inspection: Check the surface for defects such as scratches, cracks, and pinholes. Scratches may occur during processing or transportation, while cracks and pinholes may affect the strength and corrosion resistance of stainless steel. Magnifying glasses and other tools can be used to assist in inspecting minute defects.

II. Chemical Composition Inspection
Spectroscopic Analysis: This is a commonly used method that uses a spectrometer to determine the content of various elements in the stainless steel. For example, the main components of 304 stainless steel are iron (Fe), chromium (Cr), and nickel (Ni), with chromium content approximately 18-20% and nickel content approximately 8-10.5%. Spectroscopic analysis can quickly and accurately detect whether the actual proportions of these elements meet standard requirements.
Chemical titration: Chemical titration is also effective for determining the content of certain elements. It utilizes a chemical reaction, determining the element content through a quantitative reaction between the titrant and the analyte. However, this method is relatively complex and time-consuming.

III. Mechanical Property Testing
Hardness Testing:
Rockwell Hardness (HRC, HRB, etc.): Suitable for harder stainless steel materials. A Rockwell hardness tester applies pressure to the material surface, and the hardness value is determined based on the depth of the indentation.
Brinell Hardness (HB): Commonly used for softer stainless steel materials or testing the annealed state of materials. It involves pressing a steel ball or cemented carbide ball of a specific diameter into the material surface under a specified test force, and calculating the hardness value based on the diameter of the indentation.
Tensile Test: A tensile testing machine is used to stretch stainless steel specimens, measuring the material's yield strength, tensile strength, and elongation. Yield strength is the stress at which the material begins to undergo significant plastic deformation; tensile strength is the maximum stress the material can withstand before fracture; and elongation reflects the material's plasticity. These indicators are crucial for evaluating the performance of stainless steel under tensile loads.
Impact Test: Used to test the toughness of stainless steel materials, i.e., their ability to resist impact loads. The Charpy impact test is generally used, where a pendulum impacts a notched specimen, measuring the absorbed energy. Stainless steel used in special conditions such as low-temperature environments requires higher impact toughness.

IV. Corrosion Resistance Testing
Salt Spray Test: Stainless steel samples are placed in a salt spray test chamber to simulate marine climates or other harsh environments containing salt. The concentration of sodium chloride (NaCl) solution used is generally 3-5%. The test time can be set according to specific requirements, such as 24 hours, 48 hours, 72 hours, etc. The corrosion resistance of stainless steel is assessed by observing the surface corrosion of the sample, such as the presence of rust spots or pitting.
Immersion test: Stainless steel is immersed in a specific chemical solution, such as an acidic solution (sulfuric acid, hydrochloric acid, etc.), an alkaline solution (sodium hydroxide, etc.), or a solution containing corrosive ions (such as chloride ions). After a certain period of time, the material is removed and the changes on the surface are observed, including color changes and the formation of corrosion products. This method can more directly simulate the corrosion of stainless steel in real chemical environments.

1. Chemical composition is one of the important factors affecting material properties, and it is necessary to ensure that the composition meets the standard requirements. Spectroscopic analysis: The chemical composition of stainless steel plates is analyzed using instruments such as spectrometers to detect the content of key elements such as chromium, nickel, and molybdenum. The content of these elements has a significant impact on the corrosion resistance and strength of stainless steel.
The test results are compared with national or industry standards for stainless steel to confirm whether its chemical composition meets the requirements.

2. Mechanical performance testing is required.
Mechanical properties include tensile strength, yield strength, elongation, and other indicators, which are important parameters for evaluating the strength and plasticity of materials. Tensile tests can be performed using a universal testing machine to obtain tensile curves and related parameters, such as yield strength and elongation.

3. Impact performance testing is required.
Impact performance is an indicator of a material's impact resistance. It can be tested using an impact testing machine to obtain parameters such as impact absorbed energy and impact strength.
Stainless steel sheets need to have good impact resistance under certain special conditions, such as in low-temperature environments.

4. Perform a hardness test.
Hardness is a material's ability to resist scratches and deformation. It can be tested using hardness measuring instruments such as a Rockwell hardness tester to obtain the material's hardness value.
Hardness is closely related to the strength of a material, and hardness testing can assess a material's resistance to scratches.

5. Perform microscopic tissue analysis.
Microstructure is the internal microstructure of a material, which directly affects its mechanical properties and corrosion resistance.
The microstructure of medium-thick stainless steel plates can be observed and analyzed using instruments such as metallographic microscopes to understand information such as grain size, grain boundaries, and phase distribution.

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