Mechanical Behavior and Microstructural Change of a High Nitrogen CrMn Austenitic Stainless Steel during Hot Deformation
- PDF / 853,396 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 103 Downloads / 246 Views
UCTION
HIGH nitrogen austenitic steel (HNAS) (N levels exceeds approximately 0.4 mass pct) is developing into a new class of engineering material.[1–4] Recent advances in melting technologies, such as pressurized electric slag remelting and contrary pressure casting manufacture, have made it possible to produce HNAS with N concentrations in excess of 1.0 mass pct.[4] As a high nitrogen CrMn austenitic stainless steel, 18Mn18Cr0.5N has an interesting combination of mechanical, chemical, and physical properties: high strength and toughness, good corrosion resistance, and low magnetic susceptibility.[5] Thus, it has been widely used for the production of heavy generator retaining rings. As many kinds of alloying elements exist in HNAS, the hot workability of the steels is generally lower. There are usually many problems, such as surface cracking, coarse grains, and mixed grain structures, in the forging process, causing adverse influence on ultrasonic inspection and subsequent processing. ZHENHUA WANG, WANTANG FU, HUI LI, and ZHIQING LV are with the State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, People’s Republic of China. Contact e-mail: [email protected] SHUHUA SUN is with College of Sciences, Yanshan University, Qinhuangdao 066004, People’s Republic of China. DELI ZHAO, formerly with the State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, is with China First Heavy Industries, Qiqihar, 161042, People’s Republic of China. Manuscript submitted June 28, 2009. Article published online February 3, 2010 METALLURGICAL AND MATERIALS TRANSACTIONS A
Many properties of HNAS, especially 18Cr18Mn0.5N steel, have been extensively studied, such as precipitation, resistance to cavitation erosion, microstructure, and cold and hot deformation behaviors.[5–9] The hot deformation equation and microstructural evolution have been obtained using the hot torsion test.[8] In fact, the strain and strain rate vary along the torsion specimen radius, and there is a distinct difference in stress and strain states between the torsion specimen (simple shear deformation) and heavy forging. The dependence of the thermoplasticity of 18Cr18Mn0.5N steel on temperature has also been determined using the compression test, but the microstructural evolution and flow behavior have not been chiefly concerned yet.[9] The hot processing map technology based on the dynamic materials model has the capabilities of optimizing the parameters of processing technology, controlling microstructure and properties, and improving the hot working repeatability. It has been used to evaluate the thermal deformation mechanisms of a wide range of metal materials such as alloys of magnesium, aluminum, titanium, and Ni-base superalloys as well as austenitic steel.[10–14] However, relatively few studies are available on the application of hot processing map technology in HNAS, especially in the hig
Data Loading...
