Defect name: Surface defect
Record No.: 690
Type of defect (Internal/Surface): Surface
Defect classification: Machining defects
Steel name:
Steel composition in weight %: 0.06% C, 0.96% Mn, 0.02% Si, 0.05% P, 0.31% S, 0.03% Cr, 0.03% Ni, 0.01% Mo, 0.06% Cu.
Note: One cold drawn and machined part exhibiting a linear defect indication on the machined ID surface was submitted to our laboratory for a metallurgical failure analysis service investigation. Our metallurgy experts were requested to determine the source cause of the ID surface defect indication. The material identification is shown in the table below.
Based upon the opinion of our failure analysis lab and the performed examinations, it is our opinion the ID surface of the part contained a faint, intermittent, tool mark that was induced during the machining operation.
No evidence was observed of a pre-existing internal steel defect or inclusion stringer on the ID surface that could have caused the defect indication.
The microstructure as determined by the metal test lab was typical of AISI 1215 steel.
SEM examination of the ID surface revealed a faint, intermittent, linear surface defect indication along the .234” diameter ID surface. (See arrows in Figures 1 - 2).
Examination at higher magnification showed evidence of disturbed metal, most likely from the machining tool (see Figures 3 – 4). No evidence was observed of a pre-existing internal steel defect or inclusion stringer on the ID surface.
Metallographic examination
1. A transverse section removed from the region containing the ID surface defect indication confirmed the presence of a tool mark that was induced during the machining operation. (See arrow in Figures 5 - 6).
2. No evidence was observed of an abnormal inclusion content or any other detrimental internal conditions that could have caused the defect indication.
3. The microstructure consisted of pearlite and grain boundary cementite in a matrix of ferrite, typical of AISI 1215 steel.