Studying And Manufacturing Of Multilayer Laminates Based On Arc Additive Manufacturing

The use of a variety of alloys to make composite reinforcements is a way to make high-strength steels,and there have been many related studies.In this study,the material used in experiment were 304 stainless steel welding wire and TH-Q50 c low carbon steel welding wire.Through the additive manufacturing method of "A-B-A" form,the high strength steel forming member with much higher strength than the two raw materials was finally obtained.The formed high-strength steel has high strength but poor plasticity,and is subsequently subjected to annealing heat treatment to improve the plasticity of the molding material.The main conclusions are as follows:For the molding material,there is a difference in the final structure formed between the low carbon steel layer and the stainless steel layer.In the low carbon steel layer,the resulting microstructure is a ferrite structure with uneven grain size,mainly due to unbalanced crystallization during the manufacturing process,and the appearance of fine grain regions is related to the silicon contained in the material.The presence of silicon provides a matrix of heterogeneous nucleation.In the stainless steel layer,the resulting structure is a lath martensite of bcc structure,and the cause of formation is related to the large cooling rate in the additive manufacturing process.The mechanical properties of the molding material were tested.The hardness test results showed that the hardness of the stainless steel layer was higher than that of the low carbon steel layer;the tensile strength could reach 900 MPa,but the elongation was only 3%,which seriously limited the performance of the material.The subsequent material is subjected to a subsequent annealing heat treatment.Annealing temperature is selected from 500? to 1100? every 100 ° C annealing,heating rate is 5? / min,the annealing temperature is maintained for 2.5 h,and then the furnace is cooled to room temperature,microstructure observation and mechanical properties of all samples test.In the low carbon steel layer,when the annealing temperature is 500? and 600?,the grain refinement,the resulting structure is ferrite;when the annealing temperature is 700?,the bainite is finally obtained;the annealing temperature is 800 ? At 900 ?,the structure is bainite,pearlite,and a part of unconverted austenite;when the annealing temperature is 1000? and 1100?,the tissue type is similar to the annealing temperature of 800? and 900?,but the austenite The bulk grain size is significantly increased.In contrast,the microstructure of the stainless steel layer does not change with increasing annealing temperature.The tensile results show that when the annealing temperature is 900 ?,the best strength and plasticity combination can be achieved.At this time,the tensile strength along the vertical direction is 1255 MPa,and the elongation is 15%;the stretching along the horizontal direction was 1176 MPa and the elongation was 26%.The tensile fracture of all the specimens in the vertical direction occurred in the low carbon steel layer,indicating that the interface strength between the low carbon steel layer and the stainless steel layer exceeded that of the pure material layer.The hardness test results of all the samples indicate that the hardness of the stainless steel layer is greater than the hardness of the low carbon steel layer,because the hardness is approximately positively correlated with the tensile strength,so the tensile specimens in the vertical direction are broken in the low carbon steel layer.