Cleanliness evaluation method for metallic materials based on ultrasonic flaw detection and metallic material affixed with evaluation of cleanliness

A cleanliness evaluation method for metallic materials characterized in that cleanliness of a metallic material to be tested is evaluated by setting n inspection fields in predetermined portions of a metallic material to be tested, scanning each inspection field by ultrasonic flaw detection method for non-metallic inclusion in the metal to obtain ultrasonic echo amplitude data Ij (j=1,n) received from the maximum non-metallic inclusion in each inspection field, then calculating estimated maximum ultrasonic echo amplitude data Imax from the estimated maximum non-metallic inclusion in the metallic material to be tested with the following equations (2) and (2′) from the data Ij (j=1, n) of ultrasonic echo amplitude reflected from the maximum non-metallic inclusion in each inspection field that has been determined, thereby calculating estimated maximum non-metallic inclusion diameter from the estimated maximum ultrasonic echo amplitude data Imax;

• [Equation 2] Linear regression of ultrasonic echo amplitude data Ij (j=1, n) from the maximum non-metallic inclusion and reduced variate yj (j=1,n),
• I=ty+u (2),
• where n=Number of tests,
• Reduced variate yj=−ln[−ln{j/(n+1)}] (where j=1, n),
• t=Regression coefficient,
• u=Constant,
• [Equation 2′] Formula to calculate the maximum ultrasonic echo amplitude data Imax from estimated maximum non-metallic inclusion in the metallic material to be tested,
• Imax=t×ymax+u (2′),
• V0=Reference volume of test (mm3),
• V=Subject volume of estimate (mm3),
• T (Return period)=(V+V0)/V0,
• ymax (Reduced variate)=−ln[−ln{(T−1)/T}].

A metallic material affixed with evaluation of cleanliness thereof given according to estimated maximum non-metallic inclusion diameter amax for the entire metallic material to be tested, which is calculated with the following equations (1) and (1′) from maximum non-metallic inclusion diameter data aj (j=1,n) obtained with ultrasonic flaw detection method by scanning each of n inspection fields that are set in predetermined portions of the metallic material;

• [Equation 1] Linear regression of maximum non-metallic inclusion diameter aj (j=1,n) and reduced variate yj (j=1,n),
• a=ty+u (1),
• where n=Number of tests,
• Reduced variate yj=−ln[−ln{j/(n+1)}] (where j=1, n),
• t=Regression coefficient,
• u=Constant,
• [Equation 1′] Formula to calculate the estimated maximum non-metallic inclusion diameter amax included in the entire metallic material to be tested (equation of regression line),
• amax=t×ymax+u (1′),
• V0=Reference volume of test (mm3),
• V=Subject volume of estimate (mm3),
• (Return period)=(V+V0)/V0,
• ymax (Reduced variate)=−ln[−ln{(T−1)/T}].

A metallic material affixed with evaluation of cleanliness thereof that is given according to estimated maximum non-metallic inclusion diameter determined from estimated maximum ultrasonic echo amplitude Imax for the entire metallic material that is calculated with the following equations (2) and (2′) from maximum value data Ij (j=1,n) of the ultrasonic echo received from non-metallic inclusion in each of n inspection fields that are set in predetermined portions of the metallic material;

• [Equation 2] Linear regression of ultrasonic echo amplitude data Ij (j=1, n) from the maximum non-metallic inclusion and reduced variate yj (j=1,n),
• I=ty+u (2),
• where n=Number of tests,
• Reduced variate yj=−ln[−ln{j/(n+1)}] (where j=1,n),
• t=Regression coefficient,
• u=Constant,
• [Equation 2′] Formula to calculate the maximum ultrasonic echo amplitude data Imax from estimated maximum non-metallic inclusion in the entire metallic material,
• Imax=t×ymax+u (2),
• V0=Reference volume of test (mm3),
• V=Subject volume of estimate (mm3),
• T (Return period)=(V+V0)/V0,
• ymax (Reduced variate)=−ln[−ln{(T−1)/T}].