This standard refers to the International Standard ISO 4969-1980 "Steel-Macroscopic Examination by Etching with Strong Mineral Acids".
1. Subject Content and Application Scope
This national standard specifies the inspection for the hot and cold acid etch and electric erosion method of the steel’s macrostructure and defects.
This standard is applicable to inspection of steel's macrostructure and defect. Arbitrating inspection shall be subject to hot acid etching method is there is no specific requirements on technical condition.
2. Specimen
2.1 Specimen Intercept
Specimen intercept's position, quantity and test condition shall be conducted according to relevant standard, technical condition or requirements in mutual agreement. In case of no requirements, take two specimens from the steel products (billet) according to melting (batch) number. Manufacturing plant shall sample from the most severe defect position, generally intercepting the header of the equivalent first and last panel (branch) of steel ingot.
As to continuous casting blank, intercepting a piece of specimen from the first billet after adjusting continuous casting drawing speed, according to melting (batch) number..
2.2 Sampling Method
Use methods such as cut, saw and cutting to sample. When processing the specimen, remove manufacturing deficiency such as deformation and heat-affected zone as well as crack, which is caused by sampling. After processing, surface roughness of test surface shall be not larger than 1.6μm, cold acid etching method not larger than 0.8μm, test surface is no oily soil and processing scratches, if necessary take pre-cleaning.
The reference dimension between test surface and cut surface is:
a. Hot cutting not less than 20mm;
b. Cold cutting not less than 10mm;
c. Burning not less than 40mm.
2.3 Sample Size
Generally thickness of transverse test-piece is 20mm; test surface shall be perpendicular to bearing of trend of steel products (billet). generally the length of specimen in longitudinal direction is 1.5 times that of side length or diameter, generally test surface shall be through longitudinal axis of steel products(billet), and the last machine direction of test surface shall be perpendicular to bearing of trend of steel products(billet). Steel plate's test surface shall generally be 250mm in length, and width is equal to plate thickness.
