Shrinkage cavities and large inclusions are serious internal defects of heavy steel ingot and influence the quality of subsequent forgings. In order to remove these two types of defects, a 70 t 12Cr2Mo1 heavy ingot fa...Shrinkage cavities and large inclusions are serious internal defects of heavy steel ingot and influence the quality of subsequent forgings. In order to remove these two types of defects, a 70 t 12Cr2Mo1 heavy ingot fabricated by vacuum carbon de-oxidation process was sectioned and investigated by means of structure observation and EDS analysis. To further study the forming mechanism of shrinkage and inclusion defects and find possible solutions, simulation on pouring and solidification processes was also carried out using Fluent and ProCAST software, respectively. Results show that the shrinkage defects do not appear in the middle-upper part of the ingot. The critical value of shrinkage cavity criterion is ascertained as 0.013 on the basis of sectioning investigation and simulation results, which can be used in computer simulation to predict and avoid shrinkage defects in production of 12Cr2Mo1 ingots with different weights. However, large inclusions are found at the bottom of the ingot body. The bad thermal conditions of the ingot surface and large amount of entrained slag are the main origin of the large inclusions. The simulation result of the pouring process shows that large inclusions may be eliminated by combined measures of improving the top thermal condition and controlling the height of rudimental molten steel in the ladle to above 300 mm.展开更多
Good internal quality of steel pipes is a basic guarantee for the safe and efficient operation of pipeline system. While presence of large inclusions has adverse effect on the mechanical properties,weldability and cor...Good internal quality of steel pipes is a basic guarantee for the safe and efficient operation of pipeline system. While presence of large inclusions has adverse effect on the mechanical properties,weldability and corrosion resistance of the steel pipes,and then it would bring huge risk to the safe operation of oil and gas transmission pipeline.In order to reduce the risk to a minimum extent,it is quite necessary to analysis and study the characteristics of large inclusions in high grade pipeline steel,and then it would provide evidence for the formulation of level-determination standard of large inclusions during steel pipe acceptance.Optimized production technology such as electromagnetic stirring is put forward accordingly to prevent the occurrence of large inclusions in pipeline steel.展开更多
基金financially supported by the Program of National Technological Cooperation and Communication(Project 2010 DFR 70640)Chinese National S&T Major Project(2011ZX06004-016)
文摘Shrinkage cavities and large inclusions are serious internal defects of heavy steel ingot and influence the quality of subsequent forgings. In order to remove these two types of defects, a 70 t 12Cr2Mo1 heavy ingot fabricated by vacuum carbon de-oxidation process was sectioned and investigated by means of structure observation and EDS analysis. To further study the forming mechanism of shrinkage and inclusion defects and find possible solutions, simulation on pouring and solidification processes was also carried out using Fluent and ProCAST software, respectively. Results show that the shrinkage defects do not appear in the middle-upper part of the ingot. The critical value of shrinkage cavity criterion is ascertained as 0.013 on the basis of sectioning investigation and simulation results, which can be used in computer simulation to predict and avoid shrinkage defects in production of 12Cr2Mo1 ingots with different weights. However, large inclusions are found at the bottom of the ingot body. The bad thermal conditions of the ingot surface and large amount of entrained slag are the main origin of the large inclusions. The simulation result of the pouring process shows that large inclusions may be eliminated by combined measures of improving the top thermal condition and controlling the height of rudimental molten steel in the ladle to above 300 mm.
文摘Good internal quality of steel pipes is a basic guarantee for the safe and efficient operation of pipeline system. While presence of large inclusions has adverse effect on the mechanical properties,weldability and corrosion resistance of the steel pipes,and then it would bring huge risk to the safe operation of oil and gas transmission pipeline.In order to reduce the risk to a minimum extent,it is quite necessary to analysis and study the characteristics of large inclusions in high grade pipeline steel,and then it would provide evidence for the formulation of level-determination standard of large inclusions during steel pipe acceptance.Optimized production technology such as electromagnetic stirring is put forward accordingly to prevent the occurrence of large inclusions in pipeline steel.
