Research On Cracking Causes And Preventive Measures Of Seamless Steel Tube

Seamless steel tube is widely used in buildings, vehicles, petroleum, aviation,chemical industry, boiler and military industry and other industries with its unique andexcellent performance，it plays a very important role in the economic development of thewhole country. In recent years, seamless steel pipe in promoting national economicdevelopment and also highlighted some problems.the steel industry is always pay attentionto the seamless steel pipe cracking, the steel tube cracks in production process will not onlylead to the waste of raw materials, possibly reduced production efficiency cause theproduction of the time delay. If the seamless steel pipe cracking in the use process, maycause a great loss of property, and even lead to the casualty. In addition, because theproduction technology parameters of seamless steel tube is complex, when the steel pipecracking, we often can not timely find the cracking reasons.In order to solve the problem above, this subject relied on the actual situation of theco-operation, using the German BrukerQ4170direct reading spectrometer, the GermanLeica DM4000M microscope, polishing machine, metallography cutting machine and soon. We mainly from the following three aspects to study the influence factors and theinfluence law of seamless steel pipe cracking: the defects of original material，metallographic organization,preventive measures.The results show:1. The defects of original material has an important influence on the seamless steelpipe cracking. Research shows that: In seamless steel pipe cracking, the main type ofnon-metallic inclusions is spherical oxide inclusions (D class), When the oxide levels morethan2level, it has a very important influence to the cracking of steel; Chemicalcomposition segregation mainly Performance for the Uneven distribution of carbonelement, this phenomenon will cause the uneven mechanical properties of the steel pipe,When processing, beause the internal stress resulting in seamless steel pipe cracking.2.The defects of Metallographic organization has an important influence on theseamless steel pipe cracking. Research shows that: banded structure plays an importantrole on cracking of steel pipe, When the band structure is greater than or equal to the level4,The banded structure has an important influence on the cracking of steel. In addition,widmanstatten structure has some influence on the cracking of steel, Experimental results show that: When the widmanstatten structure is greater than or equal to the level3, Thewidmanstatten structure has an important influence on the cracking of steel; Themicrostructure morphology abnormality is an important reason leading to cracking of steel,Experimental results show that: Metallographic organization abnormal reflected in thegrain coarsening, metallographic uneven, abnormal components and so on.3.According to the different causes of cracking, put forward correspondingimprovement or prevent measures. For the non metallic inclusions, Through the selectionof high quality refractory materials or crystallizer protection slag, or selecte appropriatedeoxidizer, Smelting and casting process, the strictly non-metallic reducing mixing; forsegregation, segregation easily control the content of the other elements other than carbon,or to reduce the casting temperature or electromagnetic stirring prevent segregation; thestrip organizations and widmanstatten, can be used normalizing or annealing process toeliminate, in addition banded structure should also be prevented by preventing segregation;abnormalities caused by the microstructure of seamless steel pipe cracking, mainly byimproving heat treatment specific parameters or heat treatment to deal with.