| 2507 duplex stainless steel with excellent corrosion resistance,mechanical properties and relatively low price,is widely used in shipbuilding,petrochemical and other corrosive environment.Laser welding has the characteristics of concentrated heating and small heat affected zone,and is widely used in the welding of 2507 duplex stainless steel.In this paper,the butt joint of 2507 duplex stainless steel are welded by laser and plasma welding.The microstructure and mechanical properties of duplex stainless steel welded joints were studied by means of microstructure observation,hardness test and tensile test.The experimental results were as follows:?1?The welded joints with good appearance can be obtained by both welding methods.The microstructure of the two weld joints is composed of ferrite and austenite.The ferrite mainly consists of columnar and equiaxed grains,and austenite mainly distributes on the grain boundary.Cr2N precipitate in the ferrite grains,when the heat input is large,the austenite precipitate not only in the ferrite grains,but also on the grain boundaries to form Wechsler structure.?2?The tensile strength of laser welded joints can reach 900MPa,while that of plasma welded joints is only 865 MPa.?3?The fracture surfaces of the tensile specimens obtained by the two welding methods are similar to each other,which can be divided into two parts.The one near the laser beam or the plasma beam incident plane are relatively flat accompanied with small dimples,The other far away from the laser beam or the plasma beam incident plane are rough accompanied with deep dimples.It is considered that the fracture occurs in grain boundary austenite.The fracture near the incident plane of laser beam or plasma beam occurs in the austenite between equiaxed grains,accompanied with fine and uniform dimples.The fracture far from the incident plane occurs in austenite between columnar crystals and causes deep dimples,whether columnar crystals are pulled out or torn apart. |
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