Patent ID: 8393226

Claim:
An inclusion rating method using a tensile test, the method comprising the steps of: actively charging a test specimen made of metallic material with hydrogen such that an amount of hydrogen in the test specimen is 0.2 wppm or more; carrying out the tensile test on the test specimen to cause a fracture originating from a nonmetallic inclusion affected by hydrogen in the test specimen; identifying a type of the nonmetallic inclusion; measuring a size of the nonmetallic inclusion; and evaluating a cleanliness of the metallic material by obtaining a distribution function of the size of the nonmetallic inclusion; wherein the step off measuring the size of the nonmetallic inclusion comprises measuring a projected area of the nonmetallic inclusion projected in a direction of a tensile axis of the tensile test, and wherein the step of evaluating the cleanliness of the metallic material comprises analyzing a square root of the projected area using an extreme value statistics, and estimating the size of the largest nonmetallic inclusion in the metallic material.