(3) sulfur sulfur in steel is a harmful element, it mainly exists in the form of Fey in steel.With iron to form crystal, its melting point is 989 degrees, much lower than the melting point of steel.In the process of steel solidification, separating out the grain boundary of sulfides in steel because of its low strength, large brittleness, greatly reduces the mechanical properties of steel and easy to generate heat brittle at high temperatures.If the steel liquid deoxidation is bad, more FeC, sulfur and iron and Fe0 ternary eutectic formation, lower its melting point (940 degrees), are also more dangerous.Sulfur is have an adverse effect on steel welding performance.Therefore, should as far as possible when in steelmaking to remove sulfur.(4) manganese manganese in cast stainless steel pipe fittings, the requirement for manganese mass fraction of 0.5% to 0.8%, its role is deoxidization, desulphurization.(5) phosphate phosphorus is also a harmful impurity in steel, hope as small as possible, ask its mass fraction is less than 0.06%.