Effects Of Laser Melting On Microstructure And Mechanical Properties Of304Austenitic Stainless Steel

With the increasing advance of scientific innovation ability, advancedtechnology has got swift and violent development. Relevant industries and field give anew challenge to the service performance of stainless steel material, produce highperformance stainless steel material has become important research subject fordomestic and international scholars. Laser surface melting is a high efficient metalmaterials surface strengthening, the structure of base material was obviously refined,excellent physical and chemical properties was prepared by laser surface melting, andimprove the metal material properties. For this reason,“Effects of Laser SurfaceMelting on Microstructure and Mechanical Properties of304Austenitic StainlessSteel” of the study, it will be for the productive process of stainless steel in the futureto provide theoretical guidance and experimental basis has very important theoryvalue and practical significance.This paper takes304austenitic stainless steel as the research object, the topsurface and the bottom surface of304austenitic stainless steel were melted using5KW continuous wave CO2laser in two different cooling way: one group is cooled inroom temperature air, and the other is cooled with ice water, forming the top surfaceand the bottom surface of the melted specimens with fine-grained layer. Mainly fromthe theoretical and experimental analysis, These two kinds of different coolingconditions is studied by melted forming specimens of the microstructure, microscopichardness, yield strength, tensile strength, strain hardening exponent, tensile fracturebehavior, etc. Specific results are as follows:(1) Two kinds of cooling treatment were significantly improved organizationpattern of304austenitic stainless steel. Both melted layer of basic organizationpattern are the same. Along the melted layer’s deep, organization pattern are equiaxed crystal, dendrite, cellular crystal and plane crystal,it presents the obvious gradientorganization phenomena,and microstructure becomes finer from melted layer’sinterface to the surface, the corresponding area’s microstructure is finer with ice watercooling melted layer.(2) From the overall distribution of microhardness value to know, thedistribution of hardness value along melted layer depth is relatively stable,all tend tothe corresponding curve; From the curve of synthetic to know, the crest of curve are inthe subsurface which is closed the surface. Microhardness decreases gradually fromthe subsurface of melted layer to substrate, present the obviously characteristics ofgradient distribution.(3) The yield strength、tensile strength and elongation of surface melting partcooled in the air respectively increase by16.1%、13.7%and6.0%relative to substrate,and these properties of surface melting part useing rapid method in ice watercooling respectively increase by28.4%、23.7%�'�9.7%. Surface melting part also hasstrong toughness, reliability and strain hardening ability. However, the continuousyielding characteristics of surface melting part did not change significantly.(4) There are a large number isometric dimple in the melted specimens fracture,it belongs to typical ductile fracture, and the strengthened layer formed under icewater cooling condition, its fracture dimple is more greater and deeper, thus thematerial has better plasticity and strength.