Black heart malleable cast iron and method for producing same

A black heart malleable cast iron comprising a matrix of ferrite and lump graphite included in the matrix, the black heart malleable cast iron comprising 50 ppm or more and 100 ppm or less of boron, and 65 ppm or more and 200 ppm or less of nitrogen in a mass ratio, wherein

• the black heart malleable cast iron excludes bismuth,
• the black heart malleable cast iron excludes aluminum,
• when the content of boron is B (ppm) and the content of nitrogen is N (ppm) in a mass ratio, the values of B and N satisfy the following formula (1), and
• a grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph and a standard grain size chart;
• N
• ≥
• 1.
• 3
• ⁢
• B
• -
• 10.
• (
• 1
• )