Effects of compositional variations and aging treatments on the fracture behavior of H Y130 steel in air and hydrogen
- PDF / 570,100 Bytes
- 6 Pages / 594 x 774 pts Page_size
- 12 Downloads / 125 Views
I.
INTRODUCTION
P R E V I O U S w o r k 1'2 has indicated that HY 130 steel is particularly susceptible to temper embrittlement and that this is the result of segregation of P, Ni + Si, and Sn (in the case of a commercial-purity steel) to grain boundaries. It was also found that the resistance to hydrogen-induced cracking (HIC) also falls precipitously as a result of this segregation. Later 3 it was shown that removal of the Mn, Si, and Sn eliminated both the temper embrittlement and the low-stress HIC. It was subsequently shown 4 that the HIC which occurs in a pure steel is strain-controlled and is an intrinsic property of steel deformed in H2. As the final phase of the study of this class of steels, a series of laboratory heats having varied concentrations of Mn, Si, and A1 was studied by tests in air and in H2. The Mn and Si concentrations were varied because of their effects on embrittlement by P and because of the embrittlement attributable to segregation of Ni + Si; the AI concentration was varied inadvertantly during melting of some of the heats. A Wide range of fracture behavior was observed, but it was found possible to rationalize the effects of these elements, separately and in combinations.
(4) Compact tension, 25 m m thick, for fracture toughness tests at room temperature. The specimens were heat treated as follows: Austenitization: 1000 ~ two hours, water quenched (for WOL and CT specimens) or oil quenched (for Charpy and four-point bend specimens). Tempering: 625 ~ two hours (all heats except J). 600 ~ two hours (heat J). Aging: 480 ~ up to 3000 hours. The specimens were water quenched after tempering. The hardness values fell within the range 34.5 +-l.5Rc. The prior austenitic grain size was ASTM number five. except for heat L (ASTM number nine). The hydrogen loading was done in steps until a load-drop was detected. The threshold stress intensity for hydrogeninduced cracking was determined from the stationary value of the load after periods of five to 24 hours. The hydrogen tests were conducted at 0.21 Pa and 23 ~
III. II.
EXPERIMENTAL PROCEDURE
The compositions of the steels are given in Table 1. All were laboratory heats except heat D , which was a production heat. The following kinds of test specimens were employed: (1) Charpy V-notch, for impact tests over a range of temperatures. (2) Four-point bend with a V-notch (Griffiths-Owen typeS), for slow bend tests at 77 K. (3) Modified, bolt-loaded WOL (Novak-Rolfe type 6) 22.9 mm thick with 1.3 m m deep side grooves, for constant-displacement tests in H2. Y. TAKEDA, Metallurgist, Mitsubishi Heavy Industries Ltd., Nagasaki, Japan, was formerly Research Fellow, Department of Materials Science and Engineering, University of Pennsylvania. C. J. McMAHON, Jr., is Professor, Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104. Manuscript submitted April 17, 1981. METALLURGICAL TRANSACTIONS A
RESULTS
Effect of Aging on Fracture Behavior Charpy Tests. The results of the Charpy tests can be described in s
Data Loading...
