Malleable cast iron fittings are commonly known as Ma Gang fittings, Ma Tie The production process of ductile iron is as follows: it is first cast into white cast iron parts, and then subjected to malleable annealing (malleable annealing decomposes the cementite into agglomerated graphite) to obtain malleable cast iron parts. 1. Chemical composition, microstructure and properties of malleable cast iron: 1) The chemical composition of malleable cast iron is: wC=2.2%~2.8%, wSi=1.0%~1.8%, wMn=0.3%~0.8%, wS ≤ 0.2%, wP ≤ 0.1%. 2) The microstructure of malleable cast iron has two types: ferrite (F)+agglomerated graphite (G); Pearlite (P)+flocculent graphite (G). 3) Due to the flocculent nature of graphite in malleable cast iron, its cutting effect on the matrix is relatively small. Therefore, its mechanical properties are higher than gray cast iron, with good plasticity and toughness. However, malleable cast iron cannot be forged The matrix structure of malleable cast iron is different, and its properties are also different. Black core malleable cast iron has higher plasticity and toughness, while pearlite malleable cast iron has higher strength, hardness, and