Analysis On The Formation And Improvement Measures Of Surface Cracks In 09CrCuSb Slab

09CrCuSb steel is the most ideal corrosion resistant steel for low temperature dew point corrosion at home and abroad. It is easy to produce cracks on the surface of the cast slab during the process of 09 CrCuSb continuous casting, which brings some influence to the qualified rate and the use of the product. In this paper, 09 CrCuSb continuous casting slab is studied, the cause of surface crack formation is analyzed, and the measures to improve the surface crack of 09 CrCuSb slab are put forward.Firstly, the morphology of crack in 09 CrCuSb slab were observed by the optical microscop.and the crack morphology and precipitates were scanned by the electron microscopy and energy spectrum instrument; and test of 09 CrCuSb phase transition temperature of billet, the analysis of austenitic phase transformation temperature and the casting billet in high temperature brittle zone;high temperature tensile test experiment was carried out to study the influence of temperature on the strength and plasticity of high temperature mechanical properties, and the fracture morphology was observed and analyzed by scanning electron microscope; by PROCAST software simulated acid proof of 09 CrCuSb steel casting billet continuous casting temperature and solidification microstructure change. Finally through the experiment results analysis combined with numerical simulation results, analysis of the causes of cracks, and put forward the corresponding improving crack measures from the cast billet surface temperature and microstructure of two aspects.By observing and analyzing the microstructure and the energy spectrum of the 09 CrCuSb crack cast slab, coarse austenite grain size, grain size distribution uneven and grain boundary segregation of Cu?Sb element is caused of 09 CrCuSb billet produced shows that one of the reasons of the cracks; high temperature mechanical properties test results show that, the 09 CrCuSb casting billet the third brittle temperature zone was 725 ~825 ? and in high temperature 950 ~1150 ? still have a brittle zone. in this brittle zone Cu, Sb enrichment caused by grain boundary segregation resulting in poor ductility, which is another reason the slab surface cracks. By09 CrCuSb continuous casting process known temperature calculations, the billet surface temperature at about 990 ?, high temperature brittle zone, so easy to produce surface cracks,indicating that the process of continuous casting secondary cooling water irrational allocation; by cooling rate on solidification structure impact analysis found that as the cooling rate increases, the increase in the number of organizations austenite grains become smaller and smaller, the grain boundary segregation density decreases, the yield strength is gradually increased. Another reason to produce slab surface cracks.According to the above experimental and calculation results, by increasing the amount of secondary cooling water 09 CrCuSb continuous casting, slab cooling rate increases, austenite grain refinement, one can reduce the austenite grain boundaries of Cu, Sb segregation concentration, and the other on the one hand to avoid the high temperature brittle zone, thereby reducing the incidence of 09 CrCuSb slab surface cracks. Test results found that good 09 CrCuSb internal strand quality,meet the technical requirements.