球墨铸铁管、铸铁管、铸钢管的区别作者: -1 发布时间: 2018-07-20 次浏览
Ductile iron pipe has advantages in strength over cast iron pipe. Ductile iron pipe tensile strength is 60k, while cast iron pipe tensile strength is only 31k. Ductile iron pipe's yield strength is 40k, while the ductile iron pipe does not show the yield strength, and the ductile iron pipe eventually breaks. The strength and cost ratio of ductile iron pipe is much better than that of cast iron pipe.
The strength of ductile iron pipe is comparable to that of cast steel. Ductile iron pipe has a higher yield strength, with a lower yield strength of 40k, while cast steel pipe has a yield strength of only 36k. In most municipal applications, such as water, salt water, steam, etc., ductile iron pipes are more corrosion resistant and oxidation resistant than cast steel pipes. Because of the spheroidal graphite microstructure of ductile iron pipe, ductile iron pipe is superior to cast steel pipe in reducing vibration capability, so it is more beneficial to reduce stress. An important reason to choose ductile iron pipe is that ductile iron pipe costs less than cast steel pipe. The low cost of ductile iron pipe makes the material more popular, the casting efficiency is higher, and the machining cost of ductile iron pipe is less. As an alternative to steel, ductile iron pipes were developed in 1949. Cast steel contains less than 0.3% carbon, while cast iron pipes and ductile iron pipes contain at least 3% carbon. The low carbon content in cast steel tubes prevents the carbon present as free graphite from forming structural sheets. The natural form of carbon in cast iron is free graphite sheet form. In ductile iron, the graphite sheet is changed into tiny spheres by special treatment. The improved sphere gives ductile iron better physical properties than cast iron or steel. It is the spheroidal microstructure of carbon that makes ductile iron pipe have better ductility and impact resistance, while the inner flake form of cast iron causes no ductility of cast iron. Better ductility can be obtained by ferrite matrix.
Therefore, the nodular structure in ductile iron pipe can also eliminate the cracks easily caused by flake graphite in cast iron after the pressure load parts of ductile iron pipe have been processed by ferrite annealing cycle. In microscopic photos of ductile iron, cracks can be seen marching to the graphite ball and ending. In ductile iron pipe industry, these graphite balls are called "crack terminator" because of their ability to prevent fracture.