LI Huabing
,
JIANG Zhouhua
,
ZHANG Zurui
,
YANG Yan
钢铁研究学报(英文版)
The fine grained structures of nickelfree high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing. The relationship between microstructure and mechanical properties and gain size of nickelfree high nitrogen austenitic stainless steels was examined. High strength and good ductility of the steel were found. In the grain size range, the HallPetch dependency for yield stress, tensile strength, and hardness was valid for grain size ranges for the nickelfree high nitrogen austenitic stainless steel. In the present study, the ductility of cold rolled nickelfree high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined. The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.
关键词:
grain refinement strengthening;nitrogen;nickelfree high nitrogen austenitic stainless steel;HallPetch equation
LI Huabing
,
JIANG Zhouhua
,
SHEN Minghui
,
YOU Xiangmi
钢铁研究学报(英文版)
A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in FeCrMnMo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 069% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickelfree, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 081%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃×1 h followed by water quenching, the microstructure consisted of homogeneous austenite.
关键词:
nitrogen gas alloying;nitrided ferroalloy;high nitrogen austenitic stainless steel;vacuum induction melting;electroslag remelting
