Research Of Hot Forming On Microstructure And Properties Of High Strength Stainless Steel Propeller

For a long time, propeller materials are copper alloy, however the strength of this material severely restricts the development of ship with large-scale and high-speed, combined with the ability of corrosion sulfide in sea-water resistance of copper alloy is limited. Therefore, for the material and production process of the propeller put forward higher requirements. In this paper,the propeller selection is SAF2507 duplex stainless steel, this material has a ferrite-austenite organization, high degree of alloying, excellent corrosion resistance-including the ability of resistance to local corrosion/, the PRE value up to 42, can be used in the seawater environment.To the SAF2507 duplex stainless steel, how to use the correct and reasonable hot forming technology to improve the mechanical properties such as strength of the material, to improve the microstructure of materials become a problem to be solved, this is also the main research content of this article.To make out the best hot forming process parameters for SAF2507 duplex stainless steel,this paper conducted a series of experimental study and theoretical analysis. At first, we put the sample under the condition of different hot forming process parameters-parameter such as temperature, cooling speed changes/ for processing, then sample tensile, impact and micro hardness test, Analysis of hot forming process parameters for the influence of material mechanical properties and mechanical behavior; before and after hot forming, the microstructure of materials and the change of alloy elements is obtained by scanning electron microscopy and spectrometer, used to compare the influence of hot forming for material microstructure, phase ratio and alloy elements, at last analyzed the influence of the harmful phase relative to the material impact. Finally, on a hot simulation experiment machine for material CCT curve drawing, get the CCT curve of material, the characteristics of CCT curve coincide with the experimental data.Hot forming temperature of SAF2507 duplex stainless steel shall be above 10503, lower than the temperature will have harmful phase precipitation; the cooling rate should be faster to through the area of 600 3~10003, the smaller the cooling rate, more ferrite will decomposes in the material, and more harmful phase will precipitate, micro hardness of this materials will also increase, materials prone to brittle fracture. When the temperature of hot forming up to 1100,the cooling rate greater than 303/s, no harmful phase precipitate, ferrite and austenite ratio is close to 1:1, Grain size refinement at the same time, significantly improves the strength of this material, after hot forming the gradient material microstructure make it possess excellent shock resistance, and good toughness. Through reasonable hot forming process, the material strength can up to 1200 MPa, elongation is more than 40%.