[机] black heart malleable cast iron, blackheart malleable cast iron

hēi xīn zhǎn xìng zhù tiě ㄏㄟ ㄒㄧㄣ ㄓㄢˇ ㄒㄧㄥˋ ㄓㄨˋ ㄊㄧㄝˇ