The composition of stainless steel pipe fittings is complex, primarily consisting of five key elements that have a decisive impact on the performance of stainless steel pipe fittings. Whether these elements are beneficial or harmful depends on how their content is managed. In addition to these primary elements, there are also trace elements such as Cr and Ni, which can have a certain impact on the performance of stainless steel pipe fittings and thus need to be strictly controlled.
(1) Carbon:The performance of carbon steel mainly depends on the carbon content. As the carbon content in steel increases, the strength and hardness values of the steel increase while the plasticity and toughness decrease.
(2) Silicon: In cast carbon steel, the mass fraction of silicon is 0.2%-0.45%, and this content range has little impact on the mechanical properties. The requirement for a certain amount of silicon is to ensure deoxidation of the steel; therefore, silicon is a beneficial element in steel.
(3) Sulfur: Sulfur is a harmful element in steel, mainly existing in the form of FeS. It forms eutectic with iron, with a melting point of 989 degrees, much lower than the melting point of steel. During the solidification process of steel, sulfides often precipitate at the grain boundaries, significantly reducing the mechanical properties of the steel and easily causing hot brittleness at high temperatures. If the deoxidation of the steel liquid is poor and there is a high FeC content, sulfides form ternary eutectic with iron and Fe0, with an even lower melting point (around 940 degrees), posing greater harm. Sulfur also adversely affects the welding performance of steel, so efforts should be made to remove sulfur during steelmaking.
(4) Manganese: In the casting of stainless steel pipe fittings, the mass fraction of manganese is required to be 0.5%-0.8%, serving the purpose of deoxidation and desulfurization.
(5) Phosphorus: Phosphorus is also a harmful impurity in steel, and lower content is preferred, with the mass fraction required to be less than 0.06%.
