The entire process of material quality control: six inspection methods from inspection to certification

In the process of material procurement and engineering application, in order to ensure that the product quality meets the standards, a systematic inspection, testing and certification process must be carried out. The following are six core testing methods, which are applicable to factory inspection audits and product certification procedures: 
1. Written Inspection (Document Verification)
The materials quality assurance documents provided along with the samples, third-party inspection test reports, and experimental reports, etc. will be reviewed. Only after obtaining the mutual approval from the supervisor, the general contractor, and the construction party can they be used. This step serves as the basis for verifying the supplier's quality system and certification documents during the factory inspection. 
II. Appearance Inspection (On-site Inspection)
Conduct an intuitive inspection of the material's type, specification, external geometric dimensions, markings, corrosion condition, damage, packaging situation, welding appearance and insulation condition, as well as packaging methods to determine if there are any quality issues. The inspector completes this through visual inspection and using measuring tools, and it is the most fundamental step in the inspection process. 
III. Chemical Performance Testing (Laboratory Inspection)
Chemical tests, chemical reagents, and instruments are used to identify and test the chemical composition of material samples. The results of these tests need to be compared with product certification standards (such as RoHS, REACH) to ensure that the levels of harmful substances do not exceed the limits. 
IV. Physical Performance Testing (Performance Inspection)
Using instruments, meters, optical equipment, testing machines, etc., the physical properties (such as density, thermal conductivity, electrical properties, etc.) of the material samples are identified and tested. The inspection report is an important basis for product certification. 
V. Mechanical Performance Testing (Mechanical Inspection)
Using mechanical testing equipment, test devices, and instruments, the mechanical properties (such as tensile strength, compressive strength, hardness, impact toughness, etc.) of the material samples are evaluated and tested. In the factory inspection, the calibration records of the equipment and the qualifications of the operators need to be verified for this item. 
VI. Non-destructive Testing (NDT Inspection)
Samples are tested using detection tools and instruments such as ultrasonic waves, X-rays, surface flaw detection (with dyeing, magnetic particles, or penetrant methods), without causing damage to the samples. It is commonly used for the inspection of critical structural components and pressure vessels, and the results must comply with the certification specifications.