The Process Research On Vacuum Hot Roll-Cladding For 45 Steel And E690 Steel Ultra-thick Steel Plates

In modern industrialization process,market demand for ultra-thick steel plates in the construction of infrastructure projects and large equipment manufacturing industry is relatively strong. In the case of the steel industry slump,ultra-thick steel plates production and supply can still bring considerable economic benefits for the enterprise.Vacuum hot roll-cladding for ultra-thick steel plates technique as a low-cost,high-quality,environment-friendly technology which is praised by many enterprises.Currently there are many steel companies introduced vacuum hot roll-cladding for ultra-thick steel plates. However,due to high carbon equivalent when using vacuum electron beam weld,welding cracks and defects appear,we can not guarantee that the composite interface is always in a state of high vacuum,so the product is limited to the field of low-carbon steel.Under the trend of the high-intensity, high-grade special plates,high-tech and high value-added varieties gradually become the main steel products,research on high carbon equivalent and high content of alloying elements plates technique becomes more and more important.Though the the project of "The preparation of ultra-thick steel billet technical equipment and process development research of Nanjing Steel Company",we researched on the process of vacuum hot roll-cladding for 45 steel and E690 steel ultra-thick steel plates and the vacuum electron beam weld strength substandard issue was solved,ultra-thick steel plates morphology and composition of inclusion and difference reduction rate of the mechanical properties was analyzed,TMCP process of E690 steel which can effectively improve the mechanical properties was drawn.The main work and the research results of this thesis are as follows:(1) During 45 steel and E690 steel vacuum electron beam welding,the through cracks can be eliminate by adjusted welding parameters,but coarse columnar crystals and brittle organization which lead to cracking during rolling can not eliminate by adjusting the welding parameters. Adding filler metal and set welding parameters can prevent cracks and defects produce effectively.(2) The structure of the welding zone is needle martensites.After adding filler metal,the weld organization shift to lath martensite, gradually,with the slowing down welding speed and increasing focus beam,the final organization mainly contains pearlite and a small amount of lath martensite. Weld organization has no defects and no cracks.The welding zone of E690 steel organization is martensite and bainite.After adding filler metal,the weld organization shift to lath bainite,gradually,mainly containing lath bainite and a small amount of ferrite.Welding microstructure uniformity, no defects,no cracks.(3) With using vacuum hot roll-cladding for 45 steel and E690 steel ultra-thick steel plates interface combines excellent performance.In the case of the reduction ratio exceeds 30%, interfacial bonding strength is better than the matrix strength. With the increase of the reduction rate of ultra-thick steel plates,Z to tensile strength, elongation and reduction of area have gradually increased,tensile fracture is located on matrix, the interface inclusions are crushed until it disappears gradually.(4) By controlling the temperature,austenite grain can be significantly refinement in E690 steel.Using TMCP technology can significantly improve the mechanical properties,change structure,and let the properties of the E690 steel change toward the expected direction.