Influence Of High-frequency Micro-forging On Mechanical Prope-Rties Of304Stai-nless Steel Specimens By Laser Rapid Forming

Laser rapid forming technology (LRFT) is a modern advanced manufacturingtechnology, which is developed in the1990s by a combination of the rapidprototyping technology forming thought and high power laser cladding superiorproperties. Through this method we can quickly obtain high performance densitystructure metal nearly end forming parts without any mould. Once this technologyappeared, it takes profound influence for modern machinery manufacturing, and it hasbecome a new study hot spot in the world Laser processing field. Using thistechnology we can find preparation of the parts which has rapid solidification of theorganizational characteristics, high density, the mechanical properties of formingspecimens meet or exceed the normal casting and forging parts processing,formingspecimens can meet directly use requirement after special post-processing. Thistechnology occupy widely application prospect and extensive market demand inaeronautics and astronautics, communication equipment, instrument, mouldmanufacturing, defense equipment, medical, health, and many other fields.At present, the study of this technique is still in the basic experiment researchstage in our country, there are mainly many basic problems needed to be solved. Inthis paper we have combined with the national natural science fund project "Highfrequency micro forging under the action of metal directly laser forming related basicproblems"(No.50974075). This paper is through experiment studied the influence ofmechanical properties of laser direct rapid forming specimens by high-frequencymicro forging treatment.In the existing experiment condition, we choose304stainless steel as rapidforming material, and use the laser rapid forming layered accumulation principlepreparede specimens which were divided flat specimens and cylinder specimens intotwo categories. The plat sample was obtained by ultrasonic micro-forging treatmentafter the forming was prepared, and the cylinder samples were prepared through the mechanical high frequency forging and laser rapid prototyping synergy effect.In order to study the influence of high frequency of laser rapid formingmechanical properties, comparative experiment study was conducted in these twokinds of samples. Using universal tensile testing machine do sample test. Using OMand SEM observate and analysis the effect of the surface organization and internaldefects of micro-forging rapid forming. Using ROS hardness machine test rapidforming surface hardness before and after the micro-forging. Using industrial CTanalyzed a sample of internal defects state. Using SEM observed the morphologicalfeatures of fracture tensile samples. The experimental results show:(1) Due to the influence of rapid forming process, the304stainless steel metaltensile samples exist pores and inclusions defects. Through the high frequency microforging processing, internal pores of the forming have reduced, the defects have alsogoten certain degree of healing.(2) Under the existing experimental conditions, the average tensile strength of304stainless steel plate sample (unforged) is705MPa, the average yield strength is378MPa, after forging, the average tensile strength is781MPa, the average yieldstrength is465MPa; The average tensile strength of304stainless steel cylindricalsample (not forged) is481MPa,the average yield strength is399MPa, after forging,the average tensile strength of the sample is581MPa, the average yield strength of thesample is411MPa;the average tensile strength of C-H304stainless steel cylindricalsample is621MPa, the average yield strength of the sample is410MPa, after forging,the average tensile strength is627MPa,the average yield strength of the sample is449Mpa.(3) Through the high frequency micro plastic deformation forging processing, thelaser rapid forming special branch shape crystallization organization was broken,Surface organization was translated from casting state to forging state, and the grainget refined.(4) Ultrasonic micro forging process of laser rapid forming304stainless steel ofmulti layer multi-channel lap hybrid scanning flat of surface, the hardness ofspecimens was increased from25.7HRC to45.2HRC; average tensile strength was mproved form705MPa before forging to781MPa after forging; multi layer lap arcscanning cylinder samples tensile strength from481Mpa without forging, rising to581Mpa after forging, tensile strength increased by17.2%.(5) Under the condition of specimens have a high internal defects rate, bothmechanical micro forging and ultrasonic frequency forging treatment can obviouslyimproved the tensile strength mechanical properties of laser rapid forming304stainless steel specimens. However, when defects rate reduce a certain degree, theimpact on forming mechanical properties of mechanical high frequency micro-forgingis not big.