The influence of niobium microalloying on austenite grain coarsening behavior of Ti-modified SAE 8620 steel

被引:67
作者
Alogab, K. A. [1 ]
Matlock, D. K.
Speer, J. G.
Kleebe, H. J.
机构
[1] Buraydah Coll Technol, Dept Mech Technol, Buraydad, Saudi Arabia
[2] Colorado Sch Mines, Dept Met & Mat Engn, Adv Steel Proc & Prod Res Ctr, Golden, CO 80401 USA
[3] Tech Univ Darmstadt, Inst Appl Geosci, D-64287 Darmstadt, Germany
关键词
niobium microalloying; carburizing; precipitation; abnormal grain growth;
D O I
10.2355/isijinternational.47.307
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
The potential for suppressing unacceptable austenite grain growth during carburizing by Nb microalloying additions in the range of 0.02 to 0.11 wt% to a Ti-modified SAE 8620 carburizing steel were evaluated. Alloys, were designed based on fundamental equilibrium thermodynamic analyses, as part of an extensive study on the effects of alloy composition, thermomechanical history, and pseudo-carburizing conditions on austenite grain coarsening behavior. Laboratory samples were produced to simulate both conventional hot rolling and controlled rolling practices designed to produce different initial precipitate distributions. Pseudo-carburizing heat treatments, i.e. without a carburizing atmosphere, were performed in the temperature range of 950 to 1 100 degrees C for holding times of 30 to 360 min. Precipitate distributions, including size, number density, morphology, distribution, and chemical composition in selected samples from the as-rolled and pseudo-carburized conditions were evaluated with transmission electron microscopy on extraction replicas. Results showed that increasing Nb additions to the Ti-modified SAE 8620 steel restrained austenite grain coarsening, and increased the grain coarsening time, especially at temperatures below 1 050 degrees C. The Nb-free (Ti-modified) steel yielded either severely duplex grain structures or pseudo-normal grain growth (with very large mean grain diameter). However, holding a Ti-Nb-modified steel (e.g. 0.06 Nb wt%) at 950 degrees C for 6 h or at 1 000 degrees C for 4h. produced fine and uniform austenite grain structures (with a mean grain diameter less than 20 mu m). The finer grain sizes observed in the T-Nb-modified steels were due to the presence of Nb-rich precipitates that hinder austenite grain coarsening, and precipitate distributions and grain growth behaviors are also influenced by the steel rolling history. The results indicate that Nb can successfully be used to suppress grain growth in carburizing steels.
引用
收藏
页码:307 / 316
页数:10
相关论文
共 49 条
[1]  
ADRIAN H, 1991, MATER SCI TECH SER, V7, P176, DOI 10.1179/026708391790194860
[2]  
Akhlaghi S, 2002, CAN METALL QUART, V41, P111
[3]  
ALOGAB KA, 2006, P 4 SAUD TECH C EXH, V3, P183
[4]   ANALYTICAL MODELING OF GRAIN-GROWTH IN METALS AND ALLOYS IN THE PRESENCE OF GROWING AND DISSOLVING PRECIPITATES .1. NORMAL GRAIN-GROWTH [J].
ANDERSEN, I ;
GRONG, O .
ACTA METALLURGICA ET MATERIALIA, 1995, 43 (07) :2673-2688
[5]  
ANDERSEN I, 1995, ACTA METALL MATER, V43, P2689, DOI 10.1016/0956-7151(94)00489-5
[6]  
ASHBY MF, 1980, RECRYSTALLIZATION GR, P325
[7]   EFFECTS OF 2ND-PHASE PARTICLES ON COARSENING OF AUSTENITE IN 0.15 PCT CARBON-STEELS [J].
BEPARI, MA .
METALLURGICAL TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 1989, 20 (01) :13-16
[8]  
BLECK W, 2003, 20630 EUR
[9]  
BOYER HE, 1987, CASE HARDENING STEEL, P157
[10]   Abnormal grain growth in a medium-carbon microalloyed steel [J].
Cabrera, JM ;
AlOmar, A ;
Prado, JM .
JOURNAL OF MATERIALS SCIENCE, 1996, 31 (05) :1303-1309