The High Nitrogen Nickel Austenitic Stainless Steel Microstructure And Performance Analysis

Compared with the traditional system of Cr-Ni austenitic stainless steel,high-nitrogen austenitic stainless without nickel can bring huge economic benefits. It becomes the focus of materials science because of its high strength,high toughness and excellent corrosion resistance. As nitrogen solubility in liquid steel is at a low level in the standard atmospheric pressure, equilibrium concentration of only 0.04 wt%, the stability of nickel with nitrogen to replace all the steel austenite content of the minimum needs of 0.4 wt%, so commomly, we take the method of manufacture of high-nitrogen at high-pressure to metallurgy nickel-free austenitic stainless steel.However,in the actual production of high-pressure metallurgy, the precess and technology are complex and dangerous, so it has no large-scale industrial manufacturers in the world because of its production costs are high. In recent years,the technical methods of product the nickel free high nitrogen austenitic stainless steel at atmospheric pressure become the research focus in the world. It has achieved a breakthrough, and become an important way of high nitrogen austenitic stainless steel'development. This article takes method of pre-Cr-Fe alloy nitrogen alloying at atmospheric pressure non-nickel smelter to produce high-nitrogen austenitic stainless steel, test steel heat treatment precess and its microstructure and tensile mechanical properties in-depth study, we analysis and discuss the microstructure of steel structural characteristics and the role of nitrogen in steel. The content of specific studies:1. According to the austenite stability principle of nitrogen replacing the nickel, we conduct the steel composition design, the components of design steel is 0Cr18Mn18N, in which the computing requirements is the minimum nitrogen content of 0.37 wt%; 2.We carried out extensive experimental research through the advance of the method of nitrogen alloying nickel-free atmospheric nitrogen austenitic stainless steel smelting process, at last we acquire an innovative method to manufacte high-nitrogen non-nickel austenitic stainless steel under atmospheric pressure; 3.Compare the corrosion resistance of testing steel to 1Cr18Ni9Ti austenitic stainless steel, the study results show that the test steel have the higher corrosion resistance under the conditions of electrochemical. 4.The experimental steel forging rolling followed by air cooling and heating after slow cooling of the microstructure and tensile mechanical properties were studied and analyzed. The results show that the thermal processing of steel under the conditions of nitrogen in the form of nitride precipitates, nitride lamellar morphology, similar to pearlite, and the decomposition reaction wasγâ†'γ'+Cr2N, due to nitride precipitation led to the deterioration of steel properties, in particular sighificantly reduced plasticity, fracture mechanism of brittle cleavage-off.5.In order to prevern nitride precipitation leading to adversely affect the performance of steel, we obtained a stable single-austenite by using solution methods.At the same time using TMT thermo-mechanical treatment of the as-cast steel that is repeated several large deformation forging rolling, and then solution heat treament. The test steel acquired a kind of nano-scale cellular sub-structures. Its yield strength was 740Mpa, tensile 1370Mpa and elongation was 30%.By analysising structure formation mechanism, the result is because mainly nitrogen in steel micro-area uniformity and nitrogen elements in a strong ordering tendency of making.This research work in the smelting process and toughening theory has innovation, it provides a reliable test data for high-nitrogen austenitic stainless steel without nickel research and development, explores in theory. It is important reference value for the actual production.